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Dyneins are microtubule motors capable of a retrograde sliding movement. Dynein complexes are much larger and more complex than kinesin and myosin motors. Dyneins are composed of two or three heavy chains and a large and variable number of associated light chains. Dyneins drive intracellular transport toward the minus end of microtubules which lies in the microtubule organizing center near the nucleus. The dynein family has two major branches. Axonemal dyneins facilitate the beating of cilia and flagella by rapid and efficient sliding movements of microtubules. Another branch is cytoplasmic dyneins which facilitate the transport of intracellular cargos. Compared to 15 types of axonemal dynein, only two cytoplasmic forms are known.
Genomic representation of dynein motors:
* Fungi (yeast): 1
* Plants (Arabidopsis thaliana): 0
* Insects (Drosophila melanogaster): 13
* Mammals (human): 14-15 | 0 | Theoretical and Fundamental Chemistry |
Because the urea conversion is incomplete, the urea must be separated from the unconverted reactants, including the ammonium carbamate. Various commercial urea processes are characterized by the conditions under which urea forms and the way that unconverted reactants are further processed. | 0 | Theoretical and Fundamental Chemistry |
The axial expansion joint absorbs movement in an axial direction. Standard connectors of the axial expansion joint are welded ends, fixed flanges and loose flanges. Axial expansion joints are often equipped with a guiding tube on the inside of the metal bellows. This reduces the flow resistance and prevents damage caused by direct contact with the flowing medium. Axial expansion joints, which can absorb large movements, frequently consist of two metal bellows and an inside or outside sleeve that protects against buckling under internal pressure. For small nominal diameters, protective tubes prevent mechanical damage during installation and operation. Axial expansion joints are suitable for internal and external overpressure.
If pressure is applied to the outside of the metal bellows of axial expansion joints, the expansion joints permit very large axial movements in case of internal pressure in a pipeline. Because there is no danger of buckling when an external overpressure is applied, the creator of the metal expansion joint was by a professor called Joshua Yap. | 1 | Applied and Interdisciplinary Chemistry |
Single cells of uncultured bacteria, archaea and protists, as well as individual viral particles and single fungal spores have been sequenced with the help of MDA.
The ability to sequence individual cells is also useful in combating human disease. Genomes from single human embryonic cells have been successfully amplified for sequencing using MDA, allowing preimplantation genetic diagnosis (PGD): screening for genetic health issues in an early-stage embryo before implantation. Diseases with heterogeneous properties, such as cancer, also benefit from MDA-based genome sequencing's ability to study mutations in individual cells.
The MDA products from a single cell have also been successfully used in array-comparative genomic hybridization experiments, which usually require a relatively large amount of amplified DNA. | 1 | Applied and Interdisciplinary Chemistry |
The chemical equations below summarize the fermentation of sucrose (CHO) into ethanol (CHOH). Alcoholic fermentation converts one mole of glucose into two moles of ethanol and two moles of carbon dioxide, producing two moles of ATP in the process.
:CHO + 2 ADP + 2 P → 2 CHOH + 2 CO + 2 ATP
Sucrose is a sugar composed of a glucose linked to a fructose. In the first step of alcoholic fermentation, the enzyme invertase cleaves the glycosidic linkage between the glucose and fructose molecules.
Next, each glucose molecule is broken down into two pyruvate molecules in a process known as glycolysis. Glycolysis is summarized by the equation:
:CHO + 2 ADP + 2 P + 2 NAD → 2 CHCOCOO + 2 ATP + 2 NADH + 2 HO + 2 H
CHCOCOO is pyruvate, and P is inorganic phosphate. Finally, pyruvate is converted to ethanol and CO in two steps, regenerating oxidized NAD+ needed for glycolysis:
:1. CHCOCOO + H → CHCHO + CO
catalyzed by pyruvate decarboxylase
:2. CHCHO + NADH + H → CHOH + NAD
This reaction is catalyzed by alcohol dehydrogenase (ADH1 in baker's yeast).
As shown by the reaction equation, glycolysis causes the reduction of two molecules of NAD to NADH. Two ADP molecules are also converted to two ATP and two water molecules via substrate-level phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
Simple, unhindered dialkylboranes are reactive at room temperature towards most alkenes and terminal alkynes but are difficult to prepare in high purity, since they exist in equilibrium with mono- and trialkylboranes. One common way of preparing them is the reduction of dialkylhalogenoboranes with metal hydrides. An important synthetic application using such dialkylboranes, such as diethylborane, is the transmetallation of the organoboron compounds to form organozinc compounds. | 0 | Theoretical and Fundamental Chemistry |
The delocalization of electrons across the structure of a radical, also known as its ability to form one or more resonance structures, allows for the electron-deficiency to be spread over several atoms, minimizing instability. Delocalization usually occurs in the presence of electron-donating groups, such as hydroxyl groups (−OH), ethers (−OR), adjacent alkenes, and amines (−NH or −NR), or electron-withdrawing groups, such as C=O or C≡N.
Delocalization effects can also be understood using molecular orbital theory as a lens, more specifically, by examining the intramolecular interaction of the unpaired electron with a donating group's pair of electrons or the empty π* orbital of an electron-withdrawing group in the form of a molecular orbital diagram. The HOMO of a radical is singly-occupied hence the orbital is aptly referred to as the SOMO, or the Singly-Occupied Molecular Orbital. For an electron-donating group, the SOMO interacts with the lower energy lone pair to form a new lower-energy filled bonding-orbital and a singly-filled new SOMO, higher in energy than the original. While the energy of the unpaired electron has increased, the decrease in energy of the lone pair forming the new bonding orbital outweighs the increase in energy of the new SOMO, resulting in a net decrease of the energy of the molecule. Therefore, electron-donating groups help stabilize radicals.
With a group that is instead electron-withdrawing, the SOMO then interacts with the empty π* orbital. There are no electrons occupying the higher energy orbital formed, while a new SOMO forms that is lower in energy. This results in a lower energy and higher stability of the radical species. Both donating groups and withdrawing groups stabilize radicals.
Another well-known albeit weaker form of delocalization is hyperconjugation. In radical chemistry, radicals are stabilized by hyperconjugation with adjacent alkyl groups. The donation of sigma (σ) C−H bonds into the partially empty radical orbitals helps to differentiate the stabilities of radicals on tertiary, secondary, and primary carbons. Tertiary carbon radicals have three σ C-H bonds that donate, secondary radicals only two, and primary radicals only one. Therefore, tertiary radicals are the most stable and primary radicals the least stable. | 1 | Applied and Interdisciplinary Chemistry |
Modern astrobiology inquiry has emphasized the search for water on Mars, chemical biosignatures in the permafrost, soil and rocks at the planet's surface, and even biomarker gases in the atmosphere that may give away the presence of past or present life. The detection of preserved organic molecules of unambiguous biological origin is fundamental for the confirmation of present or past life, but the 1976 Viking lander biological experiments failed to detect organics on Mars, and it is suspected it was because of the combined effects of heat applied during analysis and the unexpected presence of oxidants such as perchlorates in the Martian soil. The recent discovery of near surface ground ice on Mars supports arguments for the long-term preservation of biomolecules on Mars.
SOLID demonstrated that antibodies are unaffected by acidity, heat and oxidants such as perchlorates, and it has emerged as a viable choice for an astrobiology mission directly searching for biosignatures.
For a time, the ExoMars Rosalind Franklin' rover was planned to carry a similar instrument called Life Marker Chip. | 1 | Applied and Interdisciplinary Chemistry |
In fluid mechanics, two-phase flow is a flow of gas and liquid — a particular example of multiphase flow. Two-phase flow can occur in various forms, such as flows transitioning from pure liquid to vapor as a result of external heating, separated flows, and dispersed two-phase flows where one phase is present in the form of particles, droplets, or bubbles in a continuous carrier phase (i.e. gas or liquid). | 1 | Applied and Interdisciplinary Chemistry |
NSTX is quite similar to saxitoxin, like all the neurotoxins associated to PSP, the only difference is that NSTX shows one hydroxyl group bonded to nitrogen "1", where saxitoxyn contains one hydrogen.
This purine is highly hydrophilic and thermostable, it is not destroyed by cooking. Moreover, is very stable in usual storage, specially in acidic condition. | 1 | Applied and Interdisciplinary Chemistry |
Members of the society are required to have worked in geochemistry for at least two years at the time of application; student members are admitted if they are enrolled in courses recognised by the Association. To become a voting member, or fellow, members must satisfy the society that they have adequate training and experience in the field. Membership in the society has been used to measure total numbers of working geochemists. | 0 | Theoretical and Fundamental Chemistry |
Organoids provide an opportunity to create cellular models of human disease, which can be studied in the laboratory to better understand the causes of disease and identify possible treatments. The power of organoids in this regard was first shown for a genetic form of microcephaly, where patient cells were used to make cerebral organoids, which were smaller and showed abnormalities in early generation of neurons. In another example, the genome editing system called CRISPR was applied to human pluripotent stem cells to introduce targeted mutations in genes relevant to two different kidney diseases, polycystic kidney disease and focal segmental glomerulosclerosis. These CRISPR-modified pluripotent stem cells were subsequently grown into human kidney organoids, which exhibited disease-specific phenotypes. Kidney organoids from stem cells with polycystic kidney disease mutations formed large, translucent cyst structures from kidney tubules. When cultured in the absence of adherent cues (in suspension), these cysts reached sizes of 1 cm in diameter over several months. Kidney organoids with mutations in a gene linked to focal segmental glomerulosclerosis developed junctional defects between podocytes, the filtering cells affected in that disease. Importantly, these disease phenotypes were absent in control organoids of identical genetic background, but lacking the CRISPR mutations. Comparison of these organoid phenotypes to diseased tissues from mice and humans suggested similarities to defects in early development.
As first developed by Takahashi and Yamanaka in 2007, induced pluripotent stem cells (iPSC) can also be reprogrammed from patient skin fibroblasts. These stem cells carry the exact genetic background of the patient including any genetic mutations which might contribute to the development of human disease. Differentiation of these cells into kidney organoids has been performed from patients with Lowe Syndrome due to ORCL1 mutations. This report compared kidney organoids differentiated from patient iPSC to unrelated control iPSC and demonstrated an inability of patient kidney cells to mobilise transcription factor SIX2 from the golgi complex. Because SIX2 is a well characterised marker of nephron progenitor cells in the cap mesenchyme, the authors concluded that renal disease frequently seen in Lowe Syndrome (global failure of proximal tubule reabsorption or renal Fanconi syndrome) could be related to alteration in nephron patterning arising from nephron progenitor cells lacking this important SIX2 gene expression.
Other studies have used CRISPR gene editing to correct the patients mutation in the patient iPSC cells to create an isogenic control, which can be performed simultaneously with iPSC reprogramming. Comparison of a patient iPSC derived organoid against an isogenic control is the current gold standard in the field as it permits isolation of the mutation of interest as the only variable within the experimental model. In one such report, kidney organoids derived from iPSC of a patient with Mainzer-Saldino Syndrome due to compound heterozygous mutations in IFT140 were compared to an isogenic control organoid in which an IFT140' variant giving rise to a non-viable mRNA transcript was corrected by CRISPR. Patient kidney organoids demonstrated abnormal ciliary morphology consistent with existing animal models which was rescued to wild type morphology in the gene corrected organoids. Comparative transcriptional profiling of epithelial cells purified from patient and control organoids highlighted pathways involved in cell polarity, cell-cell junctions and dynein motor assembly, some of which had been implicated for other genotypes within the phenotypic family of renal ciliopathies. Another report utilising an isogenic control demonstrated abnormal nephrin localisation in the glomeruli of kidney organoids generated from a patient with congenital nephrotic syndrome.
Things such as epithelial metabolism can also be modelled. | 1 | Applied and Interdisciplinary Chemistry |
When a salt is distributed between two phases, the Galvani potential difference is called the distribution potential and is obtained from the respective Nernst equations for the cation C and the anion A to read
where γ represents the activity coefficient. | 0 | Theoretical and Fundamental Chemistry |
Carotenoids are produced by all photosynthetic organisms and are primarily used as accessory pigments to chlorophyll in the light-harvesting part of photosynthesis.
They are highly unsaturated with conjugated double bonds, which enables carotenoids to absorb light of various wavelengths. At the same time, the terminal groups regulate the polarity and properties within lipid membranes.
Most carotenoids are tetraterpenoids, regular isoprenoids. Several modifications to these structures exist: including cyclization, varying degrees of saturation or unsaturation, and other functional groups. Carotenes typically contain only carbon and hydrogen, i.e., they are hydrocarbons. Prominent members include α-carotene, β-carotene, and lycopene, are known as carotenes. Carotenoids containing oxygen include lutein and zeaxanthin. They are known as xanthophylls. Their color, ranging from pale yellow through bright orange to deep red, is directly related to their structure, especially the length of the conjugation. Xanthophylls are often yellow, giving their class name.
Carotenoids also participate in different types of cell signaling. They are able to signal the production of abscisic acid, which regulates plant growth, seed dormancy, embryo maturation and germination, cell division and elongation, floral growth, and stress responses. | 0 | Theoretical and Fundamental Chemistry |
Cytosine and uracil are converted into beta-alanine and later to malonyl-CoA which is needed for fatty acid synthesis, among other things. Thymine, on the other hand, is converted into β-aminoisobutyric acid which is then used to form methylmalonyl-CoA. The leftover carbon skeletons such as acetyl-CoA and Succinyl-CoA can then be oxidized by the citric acid cycle. Pyrimidine degradation ultimately ends in the formation of ammonium, water, and carbon dioxide. The ammonium can then enter the urea cycle which occurs in the cytosol and the mitochondria of cells.
Pyrimidine bases can also be salvaged. For example, the uracil base can be combined with ribose-1-phosphate to create uridine monophosphate or UMP. A similar reaction can also be done with thymine and deoxyribose-1-phosphate.
Deficiencies in enzymes involved in pyrimidine catabolism can lead to diseases such as Dihydropyrimidine dehydrogenase deficiency which has negative neurological effects. | 1 | Applied and Interdisciplinary Chemistry |
The concentration of purified protein solutions in the laboratory is useful in determining yield and measuring the success of a prep. MDS reports concentration as well as size for each test.
Since the detection is not based on inherent fluorescence of tryptophan or tyrosine residues, MDS has been used as an alternative to A280 UV-Vis quantification. | 1 | Applied and Interdisciplinary Chemistry |
The chloroplast genome most commonly includes around 100 genes that code for a variety of things, mostly to do with the protein pipeline and photosynthesis. As in prokaryotes, genes in chloroplast DNA are organized into operons. Unlike prokaryotic DNA molecules, chloroplast DNA molecules contain introns (plant mitochondrial DNAs do too, but not human mtDNAs).
Among land plants, the contents of the chloroplast genome are fairly similar. | 0 | Theoretical and Fundamental Chemistry |
Thermogenin (called uncoupling protein by its discoverers and now known as uncoupling protein 1, or UCP1) is a mitochondrial carrier protein found in brown adipose tissue (BAT). It is used to generate heat by non-shivering thermogenesis, and makes a quantitatively important contribution to countering heat loss in babies which would otherwise occur due to their high surface area-volume ratio. | 1 | Applied and Interdisciplinary Chemistry |
The great austrapede (Tsawltsping in Navi) is a bipedal, flightless, bird-like creature resembling the emu, ostrich, or the extinct Phorusrhacids that live in Pandoran savannah, and can be tamed and ridden as a mount by certain Navi clans. It has dark grey skin with blue-grey striping on its body and yellow markings on its wings, which it uses for threat displays and the long-clawed fingers at the ends for hunting and battling rivals. Great austrapedes stand slightly taller than their genetic cousin, the austrapede, and is a far more imposing creature overall. They first appear in the musical Toruk – The First Flight. | 1 | Applied and Interdisciplinary Chemistry |
Directed differentiation is a bioengineering methodology at the interface of stem cell biology, developmental biology and tissue engineering. It is essentially harnessing the potential of stem cells by constraining their differentiation in vitro toward a specific cell type or tissue of interest. Stem cells are by definition pluripotent, able to differentiate into several cell types such as neurons, cardiomyocytes, hepatocytes, etc. Efficient directed differentiation requires a detailed understanding of the lineage and cell fate decision, often provided by developmental biology. | 1 | Applied and Interdisciplinary Chemistry |
Although the possibility of function in gene deserts was predicted as early as the 1960s, genetic identification tools were unable to uncover any specific characteristics of the long noncoding regions, other than that no coding occurred in those regions. Before the completion of the human genome in 2001 through the Human Genome Project, most of the early associative gene comparisons relied on the belief that essential housekeeping genes were clustered in the same areas of the genome for ease of access and tight regulation. This belief later constructed a hypothesis that gene deserts are therefore previous regulatory sequences that are highly linked (and hence do not undergo recombination), but have had substitutions between them over time. These substitutions could cause tightly conserved genes to separate over time, thus forming regions of nonsense codes with a few essential genes. However, uncertainty due to differential gene conservation rates in different portions of chromosomes prevented accurate identification.
Later associations were remodeled when regulatory sequences were associated with transcription factors, leading to the birth of large-scale genome-wide mapping. Thus began the hunt for the contents and functions of gene deserts. Recent advancements in the screening of chromatin signatures on chromosomes (for instance, chromosome conformation capture, also known as 3C) have allowed the confirmation of the long-range gene activation model, which postulates that there are indeed physical links between regulatory enhancers and their target promoters. Research on gene deserts, although centralized on human genetics, has also been applied to mice, various birds, and Drosophila melanogaster. Although conservation is variable among selected species’ genomes, orthologous gene deserts function similarly. Thus, the prevailing the contention of gene deserts is that these noncoding sequences harbor active and important regulatory elements. | 1 | Applied and Interdisciplinary Chemistry |
The model organism Caenorhabditis elegans classified under the phylum Nematoda is amongst the most studied invertebrate species in glycobiology. The literature clearly documents a repertoire of nematodal paucimannosidic glycans. Another model nematode, Pristionchus pacificus, was also documented to express common nematodal paucimannosidic glycans.
Parasitic nematodes such as Haemonchus contortus have been reported to carry paucimannosidic glycans conjugated to an intestinal microsomal aminopeptidase. In addition, there have been reports documenting the expression of paucimannosidic glycans by others parasitic nematodes such as Ascaris suum, Heligmosomoides polygyrus and Trichuris suis. | 1 | Applied and Interdisciplinary Chemistry |
Overflow from the facultative lagoon may be routed through one or more polishing ponds supporting lower populations of anaerobic micro-organisms and a higher proportion of aerobic organisms adapted to survival in lower concentrations of organic material. Effluent from the final polishing pond may be suitable for discharge to natural receiving waters. | 1 | Applied and Interdisciplinary Chemistry |
Solid-phase epitaxy (SPE) is a transition between the amorphous and crystalline phases of a material. It is usually produced by depositing a film of amorphous material on a crystalline substrate, then heating it to crystallize the film. The single-crystal substrate serves as a template for crystal growth. The annealing step used to recrystallize or heal silicon layers amorphized during ion implantation is also considered to be a type of solid phase epitaxy. The impurity segregation and redistribution at the growing crystal-amorphous layer interface during this process is used to incorporate low-solubility dopants in metals and silicon. | 0 | Theoretical and Fundamental Chemistry |
The synthesis of 6-acetyl-1,2,3,4-tetrahydropyridine, an important bread aroma compound, starting from 2-piperidone was accomplished using t-boc anhydride.
(See Maillard reaction). The first step in this reaction sequence is the formation of the carbamate from the reaction of the amide nitrogen with boc anhydride in acetonitrile using DMAP as a catalyst.
Di-tert-butyl dicarbonate also finds applications as a polymer blowing agent due to its decomposition into gaseous products upon heating. | 0 | Theoretical and Fundamental Chemistry |
To improve the delivery of the new DNA into the cell, the DNA must be protected from damage and positively charged. Initially, anionic and neutral lipids were used for the construction of lipoplexes for synthetic vectors. However, in spite of the facts that there is little toxicity associated with them, that they are compatible with body fluids and that there was a possibility of adapting them to be tissue specific; they are complicated and time-consuming to produce so attention was turned to the cationic versions.
Cationic lipids, due to their positive charge, were first used to condense negatively charged DNA molecules so as to facilitate the encapsulation of DNA into liposomes. Later it was found that the use of cationic lipids significantly enhanced the stability of lipoplexes. Also as a result of their charge, cationic liposomes interact with the cell membrane, endocytosis was widely believed as the major route by which cells uptake lipoplexes. Endosomes are formed as the results of endocytosis, however, if genes can not be released into cytoplasm by breaking the membrane of endosome, they will be sent to lysosomes where all DNA will be destroyed before they could achieve their functions. It was also found that although cationic lipids themselves could condense and encapsulate DNA into liposomes, the transfection efficiency is very low due to the lack of ability in terms of "endosomal escaping". However, when helper lipids (usually electroneutral lipids, such as DOPE) were added to form lipoplexes, much higher transfection efficiency was observed. Later on, it was discovered that certain lipids have the ability to destabilize endosomal membranes so as to facilitate the escape of DNA from endosome, therefore those lipids are called fusogenic lipids. Although cationic liposomes have been widely used as an alternative for gene delivery vectors, a dose dependent toxicity of cationic lipids were also observed which could limit their therapeutic usages.
The most common use of lipoplexes has been in gene transfer into cancer cells, where the supplied genes have activated tumor suppressor control genes in the cell and decrease the activity of oncogenes. Recent studies have shown lipoplexes to be useful in transfecting respiratory epithelial cells. | 1 | Applied and Interdisciplinary Chemistry |
Muon spin spectroscopy, also known as µSR, is an experimental technique based on the implantation of spin-polarized muons in matter and on the detection of the influence of the atomic, molecular or crystalline surroundings on their spin motion. The motion of the muon spin is due to the magnetic field experienced by the particle and may provide information on its local environment in a very similar way to other magnetic resonance techniques, such as electron spin resonance (ESR or EPR) and, more closely, nuclear magnetic resonance (NMR). | 0 | Theoretical and Fundamental Chemistry |
Volatilizing roasting, involves oxidation at elevated temperatures of the ores, to eliminate impurity elements in the form of their volatile oxides. Examples of such volatile oxides include AsO, SbO, ZnO and sulfur oxides. Careful control of the oxygen content in the roaster is necessary, as excessive oxidation can form non-volatile oxides. | 1 | Applied and Interdisciplinary Chemistry |
Paracrine signaling through fibroblast growth factors and its respective receptors utilizes the receptor tyrosine pathway. This signaling pathway has been highly studied, using Drosophila eyes and human cancers.
Binding of FGF to FGFR phosphorylates the idle kinase and activates the RTK pathway. This pathway begins at the cell membrane surface, where a ligand binds to its specific receptor. Ligands that bind to RTKs include fibroblast growth factors, epidermal growth factors, platelet-derived growth factors, and stem cell factor. This dimerizes the transmembrane receptor to another RTK receptor, which causes the autophosphorylation and subsequent conformational change of the homodimerized receptor. This conformational change activates the dormant kinase of each RTK on the tyrosine residue. Due to the fact that the receptor spans across the membrane from the extracellular environment, through the lipid bilayer, and into the cytoplasm, the binding of the receptor to the ligand also causes the trans phosphorylation of the cytoplasmic domain of the receptor.
An adaptor protein (such as SOS) recognizes the phosphorylated tyrosine on the receptor. This protein functions as a bridge which connects the RTK to an intermediate protein (such as GNRP), starting the intracellular signaling cascade. In turn, the intermediate protein stimulates GDP-bound Ras to the activated GTP-bound Ras. GAP eventually returns Ras to its inactive state. Activation of Ras has the potential to initiate three signaling pathways downstream of Ras: Ras→Raf→MAP kinase pathway, PI3 kinase pathway, and Ral pathway. Each pathway leads to the activation of transcription factors which enter the nucleus to alter gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Potently bioactive agents of the specialized proresolving mediator class include:
* DHA-derived resolvins (Rvs) of the D series: RvD1, RvD2, RvD3, RvD4, RvD5, RvD6, AT-RvD1, AT-RvD2, AT-RvD3, AT-RvD4, AT-RvD5, and AT-RvD6.
* n-3 DPA-derived resolvins of the D series (RvD1, RvD2, and RvD5) and the T series (RvT1, RvT2, RvT3, and RvT4).
* DHA-derived neuroprotectins, also termed protectins: PD1, PDX, 17-epi-PD1, and 10-epi-PD1.
* n-3 DPA derived protectins: PD1 and PD2.
* DHA-derived maresins: MaR1, MaR2, 7-epi-Mar1, Mar-L1, and Mar-L2.
* n-3 DPA-derived maresins: Mar1, Mar2, and Mar3.
These DHA metabolites possess anti-inflammation and tissue-protection activities in animal models of inflammatory diseases; they are proposed to inhibit innate immune responses and thereby to protect from and to resolve a wide range of inflammatory responses in animals and humans. These metabolites are also proposed to contribute to the anti-inflammatory and other beneficial effects of dietary omega-3 fatty acids by being metabolized to them. | 1 | Applied and Interdisciplinary Chemistry |
The and can be approximated up to nth order as
where and are two basic polynomials of order n (Refer Chandrasekhar chapter VIII equation (97)), where are the zeros of Legendre polynomials and , where are the positive, non vanishing roots of the associated characteristic equation
where are the quadrature weights given by | 0 | Theoretical and Fundamental Chemistry |
Homogeneous Schrock-type carbene complexes such as Tebbe's reagent can be used for the olefination of carbonyls, replacing the oxygen atom with a methylidene group. The nucleophilic carbon atom behaves similarly to the carbon atom of the phosphorus ylide in the Wittig reaction, attacking the electrophilic carbonyl atom of a ketone, followed by elimination of a metal oxide.
In the nucleophilic abstraction reaction, a methyl group can be abstracted from the donating group of a Fischer carbene, making it a strong nucleophile for further reaction.
Diazo compounds like methyl phenyldiazoacetate can be used for cyclopropanation or to insert into C-H bonds of organic substrates. These reactions are catalyzed by dirhodium tetraacetate or related chiral derivatives. Such catalysis is assumed to proceed via the intermediacy of carbene complexes. | 0 | Theoretical and Fundamental Chemistry |
The Indian rivers interlinking project is a proposed large-scale civil engineering project that aims to effectively manage water resources in India by linking Indian rivers by a network of reservoirs and canals to enhance irrigation and groundwater recharge, reduce persistent floods in some parts and water shortages in other parts of India. India accounts for 18% of the world population and about 4% of the worlds water resources. One of the solutions to solve the countrys water woes is to link the rivers and lakes.
The interlinking project has been split into three parts: a northern Himalayan rivers inter-link component, a southern peninsular component and starting 2005, an intrastate rivers linking component. The project is being managed by India's National Water Development Agency, which is part of the Ministry of Jal Shakti. NWDA has studied and prepared reports on 14 inter-link projects for the Himalayan component, 16 inter-link projects for the peninsular component and 37 intrastate river linking projects.
The average rainfall in India is about 4,000 billion cubic metres, but most of Indias rainfall comes over a 4-month period – June through September. Furthermore, the rain across the very large nation is not uniform, the east and north gets most of the rain, while the west and south get less. India also sees years of excess monsoons and floods, followed by below average or late monsoons with droughts. This geographical and time variance in availability of natural water versus the year round demand for irrigation, drinking and industrial water creates a demand-supply gap, that has been worsening with Indias rising population.
Proponents of the rivers interlinking projects claim the answers to India's water problem is to conserve the abundant monsoon water bounty, store it in reservoirs, and deliver this water – using the rivers interlinking project – to areas and over times when water becomes scarce. Beyond water security, the project is also seen to offer potential benefits to transport infrastructure through navigation, hydro power as well as to broadening income sources in rural areas through fish farming. Opponents are concerned about well-known environmental, ecological, social displacement impacts as well as unknown risks associated with tinkering with nature. Others are concerned that some projects create international impact and the rights of nations such as Bangladesh must be respected and negotiated. | 1 | Applied and Interdisciplinary Chemistry |
In quantum mechanics, a state of a system is described by a wavefunction which solves the Schrödinger equation. The square of the absolute value of , i.e.
is the probability density to measure the particle in place x at time t.
Usually, when involving some sort of potential, the wavefunction is decomposed into a superposition of energy eigenstates, each oscillating with frequency of . Thus, one may write
The eigenstates have a physical meaning further than an orthonormal basis. When the energy of the system is measured, the wavefunction collapses into one of its eigenstates and so the particle wavefunction is described by the pure eigenstate corresponding to the measured energy. | 0 | Theoretical and Fundamental Chemistry |
When an initially homogenous alloy is placed in an acid that can preferentially dissolve one or more components out of the alloy, the remaining component will diffuse and organize into a unique, nano-porous microstructure. The resulting material will have ligaments, formed by the remaining material, surrounded by pores, empty space from which atoms were leached/diffused away. | 1 | Applied and Interdisciplinary Chemistry |
An expression vector, otherwise known as an expression construct, is usually a plasmid or virus designed for gene expression in cells. The vector is used to introduce a specific gene into a target cell, and can commandeer the cell's mechanism for protein synthesis to produce the protein encoded by the gene. Expression vectors are the basic tools in biotechnology for the production of proteins.
The vector is engineered to contain regulatory sequences that act as enhancer and promoter regions and lead to efficient transcription of the gene carried on the expression vector. The goal of a well-designed expression vector is the efficient production of protein, and this may be achieved by the production of significant amount of stable messenger RNA, which can then be translated into protein. The expression of a protein may be tightly controlled, and the protein is only produced in significant quantity when necessary through the use of an inducer, in some systems however the protein may be expressed constitutively. Escherichia coli is commonly used as the host for protein production, but other cell types may also be used. An example of the use of expression vector is the production of insulin, which is used for medical treatments of diabetes. | 1 | Applied and Interdisciplinary Chemistry |
TIRAP (TIR domain containing adaptor protein) is an adapter molecule associated with toll-like receptors. The innate immune system recognizes microbial pathogens through Toll-like receptors (TLRs), which identify pathogen-associated molecular patterns. Different TLRs recognize different pathogen-associated molecular patterns and all TLRs have a Toll-interleukin 1 receptor (TIR) domain, which is responsible for signal transduction. The protein encoded by this gene is a TIR adaptor protein involved in the TLR4 signaling pathway of the immune system. It activates NF-kappa-B, MAPK1, MAPK3 and JNK, which then results in cytokine secretion and the inflammatory response. Alternative splicing of this gene results in several transcript variants; however, not all variants have been fully described. | 1 | Applied and Interdisciplinary Chemistry |
Kazimierz Fajans (Kasimir Fajans in many American publications; 27 May 1887 – 18 May 1975) was a Polish American physical chemist of Polish-Jewish origin, a pioneer in the science of radioactivity and the co-discoverer of chemical element protactinium. | 1 | Applied and Interdisciplinary Chemistry |
These particulates are generally small enough to be carried by the fluid but large enough to be picked up using a flow visualization technique, such as particle image velocimetry (PIV). In reference to aerodynamic testing, such as wind tunnel testing, water tunnel testing, or any other test investigating the flow of a fluid which may be invisible to the naked eye, seeding a flow is often the only way to take visual measurements. Simple examples of a seeded flow include the introduction of smoke into a low speed wind tunnel to see the general path of the air, or injecting colored dye into a water tunnel to see secondary flow structures such as hairpin vortices.
As stated in The Handbook of Fluid Dynamics, an ideal seeding particle should have uniform properties such that its density is the same as the fluid that it's added to. | 1 | Applied and Interdisciplinary Chemistry |
A variety of Ru catalysts catalyze the Murai reaction, including RuH(CO)(PPh), RuH(PPh), Ru(CO)(PPh), and Ru(CO). | 0 | Theoretical and Fundamental Chemistry |
Lactate dehydrogenase catalyzes the interconversion of pyruvate and lactate with concomitant interconversion of NADH and NAD. It converts pyruvate, the final product of glycolysis, to lactate when oxygen is absent or in short supply, and it performs the reverse reaction during the Cori cycle in the liver. At high concentrations of lactate, the enzyme exhibits feedback inhibition, and the rate of conversion of pyruvate to lactate is decreased. It also catalyzes the dehydrogenation of 2-hydroxybutyrate, but this is a much poorer substrate than lactate. | 1 | Applied and Interdisciplinary Chemistry |
Many proteins are glycosylated on certain residues, which can affect the proteome.
Glycans can interact with receptors, which in turn affect their cellular and subcellular localization. For example, cytokines and the subgroup chemokines are small signaling proteins that are involved in the immune response. Many of the N-linked glycans on these cytokines play an important role in metabolic turnover and by engineering the glycoform and its branching, there can be advantageous physiochemical affects on the immune response.
Furthermore, glycosylated proteins, or glycoproteins, can have increased resistance to degradation by proteases, which will increase the half-life of those proteins. For example, interferon beta has been shown to be important in the treatment of multiple sclerosis. Recombinant versions of interferon beta have been produced in Escherichia coli, with the glycosylated form being more stable and resistant to protease degradation, while the non-glycosylated form is degraded much more quickly. Engineered glycoproteins have also been instrumental in enzyme replacement therapy (ERT). This has been of particular interest in the development of therapeutics for lysosomal storage disease. Proper delivery of these enzymes is highly dependent on the mannose 6-phosphate (M6P) tagging on N-glycans. Thus, engineering of these N-glyans, such as by modification of branching patterns, sialic acid capping, M6P tagging, monosaccharide constituents, and glycosidic bond linkage, there can be increased efficacy of lysosomal targeting and better delivery to the central nervous system through the blood brain barrier.
Additionally, glycoengineering has been utilized with neural stem cell cultures to increase adhesion to the extracellular matrix through the treatment of an N-acetylmannosamine analog. | 1 | Applied and Interdisciplinary Chemistry |
This enzyme belongs to the family of transferases, to be specific, those glycosyltransferases that transfer hexoses (hexosyltransferases). The systematic name of this enzyme class is 1,4-alpha-D-glucan:1,4-alpha-D-glucan 6-alpha-D-(1,4-alpha-D-glucano)-transferase. Other names in common use include branching enzyme, amylo-(1,4→1,6)-transglycosylase, Q-enzyme, alpha-glucan-branching glycosyltransferase, amylose isomerase, enzymatic branching factor, branching glycosyltransferase, enzyme Q, glucosan transglycosylase, 1,4-alpha-glucan branching enzyme 1, plant branching enzyme, alpha-1,4-glucan:alpha-1,4-glucan-6-glycosyltransferase, and starch branching enzyme. This enzyme participates in starch and sucrose metabolism. | 1 | Applied and Interdisciplinary Chemistry |
When a cell is subjected to stressful conditions, the ATF4 gene is expressed. The ATF4 transcription factor has the ability to form dimers with many different proteins that influence gene expression and cell fate. ATF4 binds to C/EBP‐ATF response element (CARE) sequences which work together to increase the transcription of stress-responsive genes. However, when undergoing amino acid starvation, the sequences will act as amino acid response elements instead.
ATF4 will work together with other transcription factors, such as CHOP and ATF3, by forming homodimers or heterodimers, resulting in numerous observed effects. The proteins that ATF4 interacts with determines the outcome of the cell during the integrated stress response. For example, ATF4 and ATF3 work to establish homeostasis inside of the cell following stressful conditions. On the other hand, ATF4 and CHOP work together to induce cell death, as well as regulating amino acid biosynthesis, transport and metabolic processes. The presence of a leucine zipper domain (bZIP) allows ATF4 to work together with many other proteins, thus creating specific responses to different types of stressors. When a cell is undergoing the stress of hypoxia, ATF4 will interact with PHD1 and PHD3 to decrease its transcriptional activity. In addition, when a cell is undergoing amino acid starvation or endoplasmic reticulum stress, TRIP3 also interacts with ATF4 to decrease activity.
One result of ATF4 and stress-response proteins expression is the induction of autophagy. During this process, the cell forms autophagosomes, or double membraned vesicles, that allow for transportation of material throughout the cell. These autophagosomes can carry unneeded organelles and proteins, as well as damaged or harmful components in an attempt by the cell to maintain homeostasis. | 1 | Applied and Interdisciplinary Chemistry |
The 65 "Sohncke" space groups, not containing any mirrors, inversion points, improper rotations or glide planes, yield chiral crystals, not identical to their mirror image; whereas space groups that do include at least one of those give achiral crystals. Achiral molecules sometimes form chiral crystals, but chiral molecules always form chiral crystals, in one of the space groups that permit this.
Among the 65 Sohncke groups are 22 that come in 11 enantiomorphic pairs. | 0 | Theoretical and Fundamental Chemistry |
A mixture of dimethyl ether and propane is used in some "freeze spray" preparations such as Dr. Scholl's Freeze Away. The mixture is stored in an aerosol spray type container at room temperature and drops to when dispensed. The mixture is often dispensed into a straw with a cotton-tipped swab. Similar products may use tetrafluoroethane or other substances. | 1 | Applied and Interdisciplinary Chemistry |
Hemoglobin has a quaternary structure characteristic of many multi-subunit globular proteins. Most of the amino acids in hemoglobin form alpha helices, and these helices are connected by short non-helical segments. Hydrogen bonds stabilize the helical sections inside this protein, causing attractions within the molecule, which then causes each polypeptide chain to fold into a specific shape. Hemoglobin's quaternary structure comes from its four subunits in roughly a tetrahedral arrangement.
In most vertebrates, the hemoglobin molecule is an assembly of four globular protein subunits. Each subunit is composed of a protein chain tightly associated with a non-protein prosthetic heme group. Each protein chain arranges into a set of alpha-helix structural segments connected together in a globin fold arrangement. Such a name is given because this arrangement is the same folding motif used in other heme/globin proteins such as myoglobin. This folding pattern contains a pocket that strongly binds the heme group.
A heme group consists of an iron (Fe) ion held in a heterocyclic ring, known as a porphyrin. This porphyrin ring consists of four pyrrole molecules cyclically linked together (by methine bridges) with the iron ion bound in the center. The iron ion, which is the site of oxygen binding, coordinates with the four nitrogen atoms in the center of the ring, which all lie in one plane. The heme is bound strongly (covalently) to the globular protein via the N atoms of the imidazole ring of F8 histidine residue (also known as the proximal histidine) below the porphyrin ring. A sixth position can reversibly bind oxygen by a coordinate covalent bond, completing the octahedral group of six ligands. This reversible bonding with oxygen is why hemoglobin is so useful for transporting oxygen around the body. Oxygen binds in an "end-on bent" geometry where one oxygen atom binds to Fe and the other protrudes at an angle. When oxygen is not bound, a very weakly bonded water molecule fills the site, forming a distorted octahedron.
Even though carbon dioxide is carried by hemoglobin, it does not compete with oxygen for the iron-binding positions but is bound to the amine groups of the protein chains attached to the heme groups.
The iron ion may be either in the ferrous Fe or in the ferric Fe state, but ferrihemoglobin (methemoglobin) (Fe) cannot bind oxygen. In binding, oxygen temporarily and reversibly oxidizes (Fe) to (Fe) while oxygen temporarily turns into the superoxide ion, thus iron must exist in the +2 oxidation state to bind oxygen. If superoxide ion associated to Fe is protonated, the hemoglobin iron will remain oxidized and incapable of binding oxygen. In such cases, the enzyme methemoglobin reductase will be able to eventually reactivate methemoglobin by reducing the iron center.
In adult humans, the most common hemoglobin type is a tetramer (which contains four subunit proteins) called hemoglobin A, consisting of two α and two β subunits non-covalently bound, each made of 141 and 146 amino acid residues, respectively. This is denoted as αβ. The subunits are structurally similar and about the same size. Each subunit has a molecular weight of about 16,000 daltons, for a total molecular weight of the tetramer of about 64,000 daltons (64,458 g/mol). Thus, 1 g/dL = 0.1551 mmol/L. Hemoglobin A is the most intensively studied of the hemoglobin molecules.
In human infants, the fetal hemoglobin molecule is made up of 2 α chains and 2 γ chains. The γ chains are gradually replaced by β chains as the infant grows.
The four polypeptide chains are bound to each other by salt bridges, hydrogen bonds, and the hydrophobic effect. | 0 | Theoretical and Fundamental Chemistry |
Advanced glycation end products (AGEs) are proteins or lipids that become glycated as a result of exposure to sugars. They are a bio-marker implicated in aging and the development, or worsening, of many degenerative diseases, such as diabetes, atherosclerosis, chronic kidney disease, and Alzheimer's disease. | 1 | Applied and Interdisciplinary Chemistry |
Oligosaccharides have diverse structures. The number of monosaccharides, ring size, the different anomeric stereochemistry, and the existence of the branched-chain sugars all contribute to the amazing complexity of the oligosaccharide structures. The essence of the reducing oligosaccharide synthesis is connecting the anomeric hydroxyl of the glycosyl donors to the alcoholic hydroxyl groups of the glycosyl acceptors. Protection of the hydroxyl groups of the acceptor with the target alcoholic hydroxyl group unprotected can assure regiochemical control. Additionally, factors such as the different protecting groups, the solvent, and the glycosylation methods can influence the anomeric configurations. This concept is illustrated by an oligosaccharide synthesis in Scheme 1. Oligosaccharide synthesis normally consists of four parts: preparation of the glycosyl donors, preparation of the glycosyl acceptors with a single unprotected hydroxyl group, the coupling of them, and the deprotection process. | 0 | Theoretical and Fundamental Chemistry |
Calcium disilicide (CaSi) is an inorganic compound, a silicide of calcium. It is a whitish or dark grey to black solid matter with melting point 1033 °C. It is insoluble in water, but may decompose when subjected to moisture, evolving hydrogen and producing calcium hydroxide. It decomposes in hot water, and is flammable and may ignite spontaneously in air.
Industrial calcium silicide usually contains iron and aluminium as the primary contaminants, and low amounts of carbon and sulfur. | 1 | Applied and Interdisciplinary Chemistry |
At higher energies ionization tends to occur more than chemical dissociations. In a typical reactive gas, 1 in 100 molecules form free radicals whereas only 1 in 10 ionizes. The predominant effect here is the forming of free radicals.
Ionic effects can predominate with selection of process parameters and if necessary the use of noble gases. | 1 | Applied and Interdisciplinary Chemistry |
MLSS is responsible for removing the biochemical oxygen demand make-up of a large portion of the solids that are retained in the activated sludge process within the water treatment process. They are the "active" part of the activated sludge process. Mixed liquor suspended solids are the solids under aeration. MLSS is measured by filtering a known volume of the mixed liquor sample, which is the same way that suspended solids are measured in wastewater. Some of the MLSS may be an inorganic material. Sometimes this may represent a large percentage of the solids present in the wastewater.
Environmental engineering focuses on the particles suspended in water and the suitable operation of water treatment plants. Therefore, it is important to measure the total mass of suspended solids, which is the MLSS, as well as the mass of organic matter suspended in the activated sludge unit. These measurements allow engineers to adjust the flow rate of return sludge from the secondary clarifier into the secondary treatment reactor. This ensures that influent organic matter will be treated with a correct concentration of microorganisms. | 0 | Theoretical and Fundamental Chemistry |
Eudistomins are β-carboline derivatives, isolated from ascidians (marine tunicates of the family Ascidiacea), like Ritterella sigillinoides, Lissoclinum fragile, or Pseudodistoma aureum. | 1 | Applied and Interdisciplinary Chemistry |
Eigen et al. and Woese proposed that the genomes of early protocells were composed of single-stranded RNA, and that individual genes corresponded to separate RNA segments, rather than being linked end-to-end as in present-day DNA genomes. A protocell that was haploid (one copy of each RNA gene) would be vulnerable to damage, since a single lesion in any RNA segment would be potentially lethal to the protocell (e.g. by blocking replication or inhibiting the function of an essential gene).
Vulnerability to damage could be reduced by maintaining two or more copies of each RNA segment in each protocell, i.e. by maintaining diploidy or polyploidy. Genome redundancy would allow a damaged RNA segment to be replaced by an additional replication of its homolog. For such a simple organism, the proportion of available resources tied up in the genetic material would be a large fraction of the total resource budget. Under limited resource conditions, the protocell reproductive rate would likely be inversely related to ploidy number, and the protocell's fitness would be reduced by the costs of redundancy. Consequently, coping with damaged RNA genes while minimizing the costs of redundancy would likely have been a fundamental problem for early protocells.
A cost-benefit analysis was carried out in which the costs of maintaining redundancy were balanced against the costs of genome damage. This analysis led to the conclusion that, under a wide range of circumstances, the selected strategy would be for each protocell to be haploid, but to periodically fuse with another haploid protocell to form a transient diploid. The retention of the haploid state maximizes the growth rate. The periodic fusions permit mutual reactivation of otherwise lethally damaged protocells. If at least one damage-free copy of each RNA gene is present in the transient diploid, viable progeny can be formed. For two, rather than one, viable daughter cells to be produced would require an extra replication of the intact RNA gene homologous to any RNA gene that had been damaged prior to the division of the fused protocell. The cycle of haploid reproduction, with occasional fusion to a transient diploid state, followed by splitting to the haploid state, can be considered to be the sexual cycle in its most primitive form. In the absence of this sexual cycle, haploid protocells with damage in an essential RNA gene would simply die.
This model for the early sexual cycle is hypothetical, but it is very similar to the known sexual behavior of the segmented RNA viruses, which are among the simplest organisms known. Influenza virus, whose genome consists of 8 physically separated single-stranded RNA segments, is an example of this type of virus. In segmented RNA viruses, "mating" can occur when a host cell is infected by at least two virus particles. If these viruses each contain an RNA segment with a lethal damage, multiple infection can lead to reactivation providing that at least one undamaged copy of each virus gene is present in the infected cell. This phenomenon is known as "multiplicity reactivation". Multiplicity reactivation has been reported to occur in influenza virus infections after induction of RNA damage by UV-irradiation, and ionizing radiation. | 0 | Theoretical and Fundamental Chemistry |
Cyclic AMP-dependent protein kinases (protein kinase A) are activated by the signal chain coming from the G protein (that was activated by the receptor) via adenylate cyclase and cyclic AMP (cAMP). In a feedback mechanism, these activated kinases phosphorylate the receptor. The longer the receptor remains active the more kinases are activated and the more receptors are phosphorylated. In β-adrenoceptors, this phosphorylation results in the switching of the coupling from the G class of G-protein to the G class. cAMP-dependent PKA mediated phosphorylation can cause heterologous desensitisation in receptors other than those activated. | 1 | Applied and Interdisciplinary Chemistry |
Ibuprofen, like other 2-arylpropionate derivatives such as ketoprofen, flurbiprofen and naproxen, contains a stereocenter in the α-position of the propionate moiety.
The product sold in pharmacies is a racemic mixture of the S and R-isomers. The S (dextrorotatory) isomer is the more biologically active; this isomer has been isolated and used medically (see dexibuprofen for details).
The isomerase enzyme, alpha-methylacyl-CoA racemase, converts (R)-ibuprofen into the (S)-enantiomer.
(S)-ibuprofen, the eutomer, harbors the desired therapeutic activity. Interestingly, the inactive (R)-enantiomer, the distomer, undergoes a unidirectional chiral inversion to offer the active (S)-enantiomer. That is, when the ibuprofen is administered as a racemate the distomer is converted in vivo into the eutomer while the latter is unaffected. | 0 | Theoretical and Fundamental Chemistry |
Adding elements is usually helpful because of solid solution strengthening, but can result in unwanted precipitation. Precipitates can be classified as geometrically close-packed (GCP), topologically close-packed (TCP), or carbides. GCP phases usually benefit mechanical properties, but TCP phases are often deleterious. Because TCP phases are not truly close packed, they have few slip systems and are brittle. Also they "scavenge" elements from GCP phases. Many elements that are good for forming γ' or have great solid solution strengthening may precipitate TCPs. The proper balance promotes GCPs while avoiding TCPs.
TCP phase formation areas are weak because they:
* have inherently poor mechanical properties
* are incoherent with the γ matrix
* are surrounded by a "depletion zone" where there is no γ'
* usually form sharp plate or needle-like morphologies which nucleate cracks
The main GCP phase is γ. Almost all superalloys are Ni-based because of this phase. γ is an ordered L1 (pronounced L-one-two), which means it has a certain atom on the face of the unit cell, and a certain atom on the corners of the unit cell. Ni-based superalloys usually present Ni on the faces and Ti or Al on the corners.
Another "good" GCP phase is γ. It is also coherent with γ, but it dissolves at high temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Captopril, the first ACE inhibitor, is a functional and structural analog of a peptide derived from the venom of the jararaca, a Brazilian pit viper (Bothrops jararaca). Enalapril is a derivative, designed by scientists at Merck to overcome the rash and bad taste caused by captopril.
Enalapril is actually a prodrug; the active metabolite is enalaprilat.
The di-acid metabolite of enalapril, enalaprilat, and its lysine analogue lisinopril are potent inhibitors of angiotensin converting enzyme (ACE); they do not contain sulphydryl groups. Both drugs can be assayed by high pressure liquid chromatography and by radioimmunoassay and plasma ACE inhibition remains stable under normal storage conditions. It is therefore possible to study their pharmacokinetics as well as their pharmacodynamic effects in humans. Enalaprilat and lisinopril as well as ACE activity have been measured in blood taken during the course of two studies of the effects of these drugs on blood pressure and autonomic responsiveness.
Lisinopril is a synthetic peptide derivative of captopril. Scientists at Merck created lisinopril by systematically altering each structural unit of enalaprilat, substituting various amino acids. Adding lysine at one end of the drug turned out to have strong activity and had adequate bioavailability when given orally; analogs of that compound resulted in lisinopril, which takes its name from the discovery with lysine. Merck conducted clinical trials, and the drug was approved for hypertension in 1987 and congestive heart failure in 1993.
The discovery posed a problem, since sales of enalapril were strong for Merck, and the company did not want to diminish those sales. Merck ended up entering into an agreement with Zeneca under which Zeneca received the right to co-market lisinopril, and Merck received the exclusive rights to an earlier stage aldose reductase inhibitor drug candidate, a potential treatment for diabetes. Zenecas marketing and brand name, "Zestril", turned out to be stronger than Mercks effort. The drug became a blockbuster for AstraZeneca (formed in 1998), with annual sales in 1999 of $1.2B.
The US patents expired in 2002. Since then, lisinopril has been available under many brand names worldwide; it is also available in combination drugs with diuretic hydrochlorothiazide (as lisinopril/hydrochlorothiazide), and with calcium channel blocker amlodipine (as lisinopril/amlodipine). | 0 | Theoretical and Fundamental Chemistry |
The phrase has also been adopted as a title for various works of art, such as the 2014 found-footage horror film As Above, So Below, as well as a number of musical works listed at As above, so below (disambiguation). | 1 | Applied and Interdisciplinary Chemistry |
Following his PhD, Chibale joined the University of Liverpool as a Sir William Ramsay British Postdoctoral Research Fellow. He developed optically active alcohols using lanthanides. In 1994 he joined the Scripps Research Institute, creating complicated natural and designed molecules from organic building blocks. He began to explore angiogenesis inhibitors, which can be used to stop cancer cells developing new blood vessels. Inspired by medicinal chemistry, Chibale returned to Africa in 1996, joining the research group of James Bull. In 2002 he joined the University of California, San Francisco as a Sandler Foundation Sabbatical Fellow. He was promoted to the rank of Professor in 2007 and a Life Fellow of the University of Cape Town in 2009. His group currently studies treatments for malaria, tuberculosis, and antibiotic-resistant microbial diseases. He set up collaborations and exchange programs for South African students to learn how to translate basic science into potential products. He was elected a Fellow of the Royal Society of South Africa in 2009.
In 2010 he founded H3D, the first drug discovery centre at the University of Cape Town. The research program received significant media attention and has been supported by Bill Gates. In 2008 he took a sabbatical, working as a Fulbright scholar at the University of Pennsylvania and Pfizer. In 2012 Chibales group discovered MMV390048, an aminopyridine compound that can be used as a single-dose treatment for malaria. It was the first antimalarial medicine to enter phase 1 human studies in Africa. In 2016 they discovered another antimalarial compound, UCT943. He has written for The Conversation about how Africas medicinal drug research can paved the landscape for health innovation in the continent.
Today he holds the Neville Isdell Chair in African-centric Drug Discovery and Development at the University of Cape Town. Over the years H3D has partnered with the South African government and innovative pharmaceutical companies to build Africa's capacity for research.
In 2016 the Royal Society of Chemistry recognised him as one of their 175 Faces of chemistry. He was elected a Fellow of the Royal Society of Chemistry in 2014.
Kelly has received many notable awards and honors, which include:
* a 2010/11 National Science and Technology Forum-BHP Billiton Award in the category TW Kambule NRF Senior Black Researcher (2011)
* UCT Alan Pifer Research Award (2011)
* South African National Research Foundation (NRF) Special Recognition Award: Champion of Research Capacity Development at South African Higher Education Institutions (2012)
* South African Medical Research Council Gold Medal (2016)
* Cheney Visiting Fellowship from the University of Leeds in the UK (2017-2018)
* South African Chemical Institute Gold Medal (2018)
Kelly was also:
# [https://newafricanmagazine.com/100/#PharmaPioneer%20#ZambianScientist%20#African one of the 100 Most Influential Africans] by New African magazine for 2019
# one of the world’s top 60 most influential/ inspirational leaders in the pharmaceutical industry on [https://themedicinemaker.com/power-list/2020 The Medicine Maker's 2020] and [https://themedicinemaker.com/power-list/2021/small-molecules/kelly-chibale 2021] Power Lists
# [https://timmermanreport.com/2021/06/on-juneteenth-honoring-22-black-biotech-leaders/ one of the 22 black biotech leaders] in honour of Juneteenth in the USA in 2021. The list, published by the Timmerman Report, celebrates innovative black leaders who are change-makers in their respective fields;
# [https://harvardpublichealth.org/25-names-to-know-in-african-public-health/ one of the 25 standout voices in African public health] by Harvard University’s Public Health magazine, 12 May 2022
# the first E[https://axial.acs.org/medicinal-chemistry/kelly-chibale-named-editor-in-chief-of-acs-medicinal-chemistry-letters ditor-In-Chief from Africa of an American Chemical Society] (ACS) publication when appointed EIC of ACS Medicinal Chemistry Letters in 2023
# Awarded [https://www.ch.cam.ac.uk/news/kelly-chibale-recognised-drug-discovery-research Royal Society (UK) Africa Prize] 2023
# Awarded [https://www.schmidtfutures.org/second-cohort-of-ai2050-senior-fellows-named-by-schmidt-futures/ Schmidt Sciences AI2050 Senior Fellowship 2023], one of seven worldwide
# Awarded [https://www.unibas.ch/en/News-Events/News/Uni-People/The-University-of-Basel-is-awarding-Kelly-Chibale-with-an-honory-doctorate.html Honorary Doctorate of the Faculty of Science], University of Basel in 2023 | 0 | Theoretical and Fundamental Chemistry |
The vectors magnitude and direction is best understood when the dislocation-bearing crystal structure is first visualized without the dislocation, that is, the perfect crystal structure. In this perfect crystal structure, a rectangle whose lengths and widths are integer multiples of (the unit cell edge length) is drawn encompassing the site of the original dislocations origin. Once this encompassing rectangle is drawn, the dislocation can be introduced. This dislocation will have the effect of deforming, not only the perfect crystal structure, but the rectangle as well. The said rectangle could have one of its sides disjoined from the perpendicular side, severing the connection of the length and width line segments of the rectangle at one of the rectangles corners, and displacing each line segment from each other. What was once a rectangle before the dislocation was introduced is now an open geometric figure, whose opening defines the direction and magnitude of the Burgers vector. Specifically, the breadth of the opening defines the magnitude of the Burgers vector, and, when a set of fixed coordinates is introduced, an angle between the termini of the dislocated rectangles length line segment and width line segment may be specified.
When calculating the Burgers vector practically, one may draw a rectangular counterclockwise circuit (Burgers circuit) from a starting point to enclose the dislocation (see the picture above). The Burgers vector will be the vector to complete the circuit, i.e., from the end to the start of the circuit.
The direction of the vector depends on the plane of dislocation, which is usually on one of the closest-packed crystallographic planes.
The magnitude is usually represented by the equation (For BCC and FCC lattices only):
where is the unit cell edge length of the crystal, is the magnitude of the Burgers vector, and , , and are the components of the Burgers vector, the coefficient is owing to the fact that in BCC and FCC lattices, the shortest lattice vectors could be as expressed Comparatively, for simple cubic lattices, and hence the magnitude is represented by
Generally, the Burgers vector of a dislocation is defined by performing a line integral over the distortion field around the dislocation line
where the integration path is a Burgers circuit around the dislocation line, is the displacement field, and is the distortion field.
In most metallic materials, the magnitude of the Burgers vector for a dislocation is of a magnitude equal to the interatomic spacing of the material, since a single dislocation will offset the crystal lattice by one close-packed crystallographic spacing unit.
In edge dislocations, the Burgers vector and dislocation line are perpendicular to one another. In screw dislocations, they are parallel.
The Burgers vector is significant in determining the yield strength of a material by affecting solute hardening, precipitation hardening and work hardening.
The Burgers vector plays an important role in determining the direction of dislocation line. | 0 | Theoretical and Fundamental Chemistry |
The liquid chromatography marketplace is incredibly diverse. Five to ten firms are consistently market leaders, yet nearly half of the market is made up of small, fragmented companies. This section of the report will focus on the roles that a few companies have had in bringing monolith column technologies to the commercial market.
In 1998, start-up biotechnology company BIA Separations of Ljubljana, Slovenia, came into being. The technology was originally developed by Tatiana Tennikova and Frantisek Svec during a collaboration between their respective institutes. The patent for these columns was acquired by BIA Separations and Ales Podgornik and Milos Barut developed the first commercially available monolith column in the form of a short disc encapsulated in a plastic housing. Trademarked CIM, BIA Separations has since introduced full lines of reversed-phase, normal-phase, ion-exchange, and affinity polymeric monoliths. Ales Podgornik and Janez Jancar then went on to develop large scale tube monolithic columns for industrial use. The largest column currently available is 8L. In May 2008, LC instrumentation powerhouse Agilent technologies agreed to market BIA Separations’ analytical columns based on monolith technology. Agilent's commercialized the columns with strong and weak ion exchange phases and Protein A in September 2008 when they unveiled their new Bio-Monolith product line at the BioProcess International conference.
While BIA Separations was the first to commercially market polymeric monoliths, Merck KGaA was the first company to market silica monoliths. In 1996, Tanaka and coworkers at the Kyoto Institute of Technology published extensive work on silica monolith technologies. Merck was later issued a license from Kyoto Institute of Technology to develop and produce the silica monoliths. Promptly thereafter, in 2001, Merck introduced its Chromolith line of monolithic HPLC columns at analytical instrumentation trade show PittCon. Initially, says Karin Cabrera, senior scientist at Merck, the high flow rate was the selling point for the Chromolith line. Based on customer feedback, though, Merck soon learned that the columns were more stable and longer-lived than particle-packed columns. The columns were the recipients of various new product awards. Difficulties in production of the silica monoliths and tight patent protection have precluded attempts by other companies at developing a similar product. It has been noted that there are more patents concerning how to encapsulate the silica rod than there are on the manufacture of the silica itself.
Historically, Merck has been known for its superior chemical products, and, in liquid chromatography, for the purity and reliability of its particulate silica. Merck is not known for its LC columns. Five years after the introduction of its Chromolith line, Merck made a very strategic marketing decision. They granted a worldwide sublicense of the technology to a small (less than $100M in sales), innovative company well known for its cutting-edge column technology: Phenomenex. This was a superior strategic move for two reasons. As mentioned above, Merck is not well known for its column manufacturing. Furthermore, having more than one silica monolith manufacturer serves to better validate the technology. Having sublicensed the technology from Merck, Phenomenex introduced its Onyx product line in January 2005.
On the other side of monolith technologies are the polymerics. Unlike the inorganic silica columns, the polymer monoliths are made of an organic polymer base. Dionex, traditionally known for its ion chromatography capabilities, has led this side of the field. In the 1990s, Dionex first acquired a license for the polymeric monolith technology developed by leading monolithic chromatography researcher Frantisec Svec while he was at Cornell University. In 2000, they acquired LC Packings, whose competencies were in LC column packings. LC Packings/Dionex revealed their first monolithic capillary column at the Montreux LC-MS Conference. Earlier that year, another company, Isco, introduced a polystyrene divinylbenzene (PS-DVB) monolith column under the brand SWIFT. In January 2005, Dionex was sold the rights to Teledyne Isco's SWIFT media products, intellectual property, technology, and related assets. Though the core competencies of Dionex have traditionally been in ion chromatography, through strategic acquisitions and technology transfers, it has quickly established itself as the primary producer of polymeric monoliths. | 0 | Theoretical and Fundamental Chemistry |
The centrifuge relies on the force resulting from centrifugal acceleration to separate molecules according to their mass, and can be applied to most fluids. The dense (heavier) molecules move towards the wall and the lighter ones remain close to the center. The centrifuge consists of a rigid body rotor rotating at full period at high speed. Concentric gas tubes located on the axis of the rotor are used to introduce feed gas into the rotor and extract the heavier and lighter separated streams. For U production, the heavier stream is the waste stream and the lighter stream is the product stream. Modern Zippe-type centrifuges are tall cylinders spinning on a vertical axis. A vertical temperature gradient can be applied to create a convective circulation rising in the center and descending at the periphery of the centrifuge. Such a countercurrent flow can also be stimulated mechanically by the scoops that take out the enriched and depleted fractions. Diffusion between these opposing flows increases the separation by the principle of countercurrent multiplication.
In practice, since there are limits to how tall a single centrifuge can be made, several such centrifuges are connected in series. Each centrifuge receives one input and produces two output lines, corresponding to light and heavy fractions. The input of each centrifuge is the output (light) of the previous centrifuge and the output (heavy) of the following stage. This produces an almost pure light fraction from the output (light) of the last centrifuge and an almost pure heavy fraction from the output (heavy) of the first centrifuge. | 0 | Theoretical and Fundamental Chemistry |
Fic-1 is the only Fic protein present in the genetic code of C. elegans. It is primarily found in the ER nuclear envelope of adult germline cells and embryotic cells, but small amounts may be found within the cytoplasm. This extra-ER pool of FICD-1s is credited with AMPylation of core histones and eEF1-A type translation factors within the nematode.
Though varying AMPylation levels did not create any noticeable effects within the nematodes behaviour or physiology, Fic-1 knockout worms were more susceptible to infection by Pseudomonas aeruginosa' compared to the counterparts with active Fic-1 domains, implying a link between AMPylation of cellular targets and immune responses within nematodes. | 1 | Applied and Interdisciplinary Chemistry |
Pathogenic bacteria and fungi have developed the means of survival in animal tissue. They may invade the gastro-intestinal tract (Escherichia, Shigella and Salmonella), the lung (Pseudomonas, Bordetella, Streptococcus and Corynebacterium), skin (Staphylococcus) or the urinary tract (Escherichia and Pseudomonas). Such bacteria may colonise wounds (Vibrio and Staphylococcus) and be responsible for septicaemia (Yersinia and Bacillus). Some bacteria survive for long periods of time in intracellular organelles, for instance Mycobacterium. (see table). Because of this continual risk of bacterial and fungal invasion, animals have developed a number of lines of defence based on immunological strategies, the complement system, the production of iron–siderophore binding proteins and the general "withdrawal" of iron.
There are two major types of iron-binding proteins present in most animals that provide protection against microbial invasion – extracellular protection is achieved by the transferrin family of proteins and intracellular protection is achieved by ferritin. Transferrin is present in the serum at approximately 30 μM, and contains two iron-binding sites, each with an extremely high affinity for iron. Under normal conditions it is about 25–40% saturated, which means that any freely available iron in the serum will be immediately scavenged – thus preventing microbial growth. Most siderophores are unable to remove iron from transferrin. Mammals also produce lactoferrin, which is similar to serum transferrin but possesses an even higher affinity for iron. Lactoferrin is present in secretory fluids, such as sweat, tears and milk, thereby minimising bacterial infection.
Ferritin is present in the cytoplasm of cells and limits the intracellular iron level to approximately 1 μM. Ferritin is a much larger protein than transferrin and is capable of binding several thousand iron atoms in a nontoxic form. Siderophores are unable to directly mobilise iron from ferritin.
In addition to these two classes of iron-binding proteins, a hormone, hepcidin, is involved in controlling the release of iron from absorptive enterocytes, iron-storing hepatocytes and macrophages. Infection leads to inflammation and the release of interleukin-6 (IL-6 ) which stimulates hepcidin expression. In humans, IL-6 production results in low serum iron, making it difficult for invading pathogens to infect. Such iron depletion has been demonstrated to limit bacterial growth in both extracellular and intracellular locations.
In addition to "iron withdrawal" tactics, mammals produce an iron –siderophore binding protein, siderochelin. Siderochelin is a member of the lipocalin family of proteins, which while diverse in sequence, displays a highly conserved structural fold, an 8-stranded antiparallel β-barrel that forms a binding site with several adjacent β-strands. Siderocalin (lipocalin 2) has 3 positively charged residues also located in the hydrophobic pocket, and these create a high affinity binding site for iron(III)–enterobactin. Siderocalin is a potent bacteriostatic agent against E. coli. As a result of infection it is secreted by both macrophages and hepatocytes, enterobactin being scavenged from the extracellular space. | 1 | Applied and Interdisciplinary Chemistry |
In subsurface flow constructed wetlands the flow of wastewater occurs between the roots of the plants and there is no water surfacing (it is kept below gravel). As a result, the system is more efficient, does not attract mosquitoes, is less odorous and less sensitive to winter conditions. Also, less area is needed to purify water. A downside to the system are the intakes, which can clog or bioclog easily, although some larger sized gravel will often solve this problem.
Subsurface flow wetlands can be further classified as horizontal flow or vertical flow constructed wetlands. In the vertical flow constructed wetland, the effluent moves vertically from the planted layer down through the substrate and out (requiring air pumps to aerate the bed). In the horizontal flow constructed wetland the effluent moves horizontally via gravity, parallel to the surface, with no surface water thus avoiding mosquito breeding. Vertical flow constructed wetlands are considered to be more efficient with less area required compared to horizontal flow constructed wetlands. However, they need to be interval-loaded and their design requires more know-how while horizontal flow constructed wetlands can receive wastewater continuously and are easier to build.
Due to the increased efficiency a vertical flow subsurface constructed wetland requires only about of space per person equivalent, down to 1.5 square metres in hot climates.
The "French System" combines primary and secondary treatment of raw wastewater. The effluent passes various filter beds whose grain size is getting progressively smaller (from gravel to sand). | 1 | Applied and Interdisciplinary Chemistry |
Several factors complicate simple correlation of obsidian hydration band thickness with absolute age. Temperature is known to speed up the hydration process. Thus, artifacts exposed to higher temperatures, for example by being at lower elevation, seem to hydrate faster. As well, obsidian chemistry, including the intrinsic water content, seems to affect the rate of hydration. Once an archeologist can control for the geochemical signature of the obsidian (e.g., the "source") and temperature (usually approximated using an "effective hydration temperature" or EHT coefficient), he or she may be able to date the artifact using the obsidian hydration technique. Water vapor pressure may also affect the rate of obsidian hydration.
The reliability of the method based on Friedmans empirical age equation (x²=kt, where x is the thickness of the hydration rim, k is the diffusion coefficient, and t' is the time) is questioned from several grounds regarding temperature dependence, square root of time and determination of diffusion rate per sample and per site, as part of some successful attempts on the procedure and applications. The SIMS-SS age calculation procedure is separated into two major steps. The first step concerns the calculation of a 3rd order fitting polynomial of the SIMS profile (eq. 1). The second stage regards the determination of the saturation layer, i.e. its depth and concentration. The whole computing processing is embedded in stand-alone software created in Matlab (version 7.0.1) software package with a graphical user interface and executable under Windows XP. Thus, the SIMS-SS age equation in years before present is given in eq. 2:
<br>
Eq. 1 Fitting polynomial of the SIMS profile
<br>
Eq. 2 The SIMS-SS age equation in years before present
Where, Ci is the intrinsic concentration of water, Cs is the saturation concentration, dC/dx is the diffusion coefficient for depth x=0, k is derived from a family of Crank's theoretical diffusion curves, and is an effective diffusion coefficient (eq. 3) which relates the inverse gradient of the fit polynomial to well dated samples:
:D = aD + b/ (10D) = 8.051eD+0.999/(1022D), Eq. 3'
where Ds = (1/(dC/dx))10 assuming a constant flux and taken as unity. The eq. (2) and assumption of unity is a matter of further investigation.
Several commercial companies and university laboratories provide obsidian hydration services. | 0 | Theoretical and Fundamental Chemistry |
The IUBMB publishes standards on biochemical nomenclature, including Enzyme Commission number nomenclature, in some cases jointly with the International Union of Pure and Applied Chemistry (IUPAC). The enzyme nomenclature scheme was developed in 1955 at the International Congress of Biochemistry and, with the addition of translocases in 2018, contains 7 classes of enzymes. | 1 | Applied and Interdisciplinary Chemistry |
Generally, there are two types of protein carbohydrate binding important in biological processes: Lectin and antibody. | 0 | Theoretical and Fundamental Chemistry |
In plants, light-dependent reactions occur in the thylakoid membranes of the chloroplasts where they drive the synthesis of ATP and NADPH. The light-dependent reactions are of two forms: cyclic and non-cyclic.
In the non-cyclic reaction, the photons are captured in the light-harvesting antenna complexes of photosystem II by chlorophyll and other accessory pigments (see diagram at right). The absorption of a photon by the antenna complex loosens an electron by a process called photoinduced charge separation. The antenna system is at the core of the chlorophyll molecule of the photosystem II reaction center. That loosened electron is taken up by the primary electron-acceptor molecule, pheophytin. As the electrons are shuttled through an electron transport chain (the so-called Z-scheme shown in the diagram), a chemiosmotic potential is generated by pumping proton cations (H) across the membrane and into the thylakoid space. An ATP synthase enzyme uses that chemiosmotic potential to make ATP during photophosphorylation, whereas NADPH is a product of the terminal redox reaction in the Z-scheme. The electron enters a chlorophyll molecule in Photosystem I. There it is further excited by the light absorbed by that photosystem. The electron is then passed along a chain of electron acceptors to which it transfers some of its energy. The energy delivered to the electron acceptors is used to move hydrogen ions across the thylakoid membrane into the lumen. The electron is eventually used to reduce the coenzyme NADP with an H to NADPH (which has functions in the light-independent reaction); at that point, the path of that electron ends.
The cyclic reaction is similar to that of the non-cyclic but differs in that it generates only ATP, and no reduced NADP (NADPH) is created. The cyclic reaction takes place only at photosystem I. Once the electron is displaced from the photosystem, the electron is passed down the electron acceptor molecules and returns to photosystem I, from where it was emitted, hence the name cyclic reaction. | 0 | Theoretical and Fundamental Chemistry |
Natural radioactivity is the spontaneous decay of the atoms of certain isotopes into other isotopes. If the resultant isotope is not stable, it undergoes further decay until a stable isotope forms. The decay process is usually accompanied by emissions of alpha, beta, and gamma radiation. Natural gamma ray radiation is one form of spontaneous radiation emitted by unstable nuclei. Gamma (γ) radiation may be considered either as an electromagnetic wave similar to visible light or X-rays, or as a particle of photon. Gamma rays are electromagnetic radiations emitted from an atomic nucleus during radioactive decay, with the wavelength in the range of 10 to 10cm | 0 | Theoretical and Fundamental Chemistry |
Inert solids in wastewater will accumulate on the bottom of the lagoon and gradually reduce depth until there is inadequate room for the facultative zone. Lagoon depths between 2 and 5 feet (60 to 150 cm) are preferred for effective treatment. Parallel facultative lagoons with common polishing ponds allow wastewater treatment to continue while one lagoon is out of service for sludge removal.
Precipitation falling on the surface of the lagoons and polishing ponds will increase the volume of wastewater requiring disposal. Conversely, the volume of wastewater may be reduced by evaporation from the water surface in arid climates.
Wastewater nutrients may cause continuing growth of algae in the polishing ponds after the original wastes have been catabolized. Algae may cause measurable contribution to biochemical oxygen demand (BOD) and total suspended solids (TSS) concentrations where discharge regulations include limitations on those concentrations. The TSS contribution of algae tends to peak in the summer months, but the long-term BOD of decomposing algae may not be evident within the typical 5-day test. United States Environmental Protection Agency regulations describe facultative lagoons as providing "treatment equivalent to secondary treatment" when 65 percent of influent BOD and TSS are removed and effluent BOD and TSS concentrations do not exceed a 7-day average of 65 mg/L and a 30-day average of 45 mg/L. Individual States may establish alternative effluent limitations. | 1 | Applied and Interdisciplinary Chemistry |
The exact mechanism by which levetiracetam acts to treat epilepsy is unknown. Levetiracetam does not exhibit pharmacologic actions similar to that of classical anticonvulsants. It does not inhibit voltage-dependent Na+ channels, does not affect GABAergic transmission, and does not bind to GABAergic or glutamatergic receptors. However, the drug binds to SV2A, a synaptic vesicle glycoprotein, and inhibits presynaptic calcium channels, reducing neurotransmitter release and acting as a neuromodulator. This is believed to impede impulse conduction across synapses. | 0 | Theoretical and Fundamental Chemistry |
Potassium ethyl xanthate is used in the mining industry as flotation agent for extraction of the ores of copper, nickel, and silver. The method exploits the affinity of these "soft" metals for the organosulfur ligand.
Potassium xanthate is a useful reagent for preparing xanthate esters from alkyl and aryl halides. The resulting xanthate esters are useful intermediates in organic synthesis. | 1 | Applied and Interdisciplinary Chemistry |
3-Hydroxypropionaldehyde is formed by the condensation of acetaldehyde and formaldehyde. This reaction, when conducted in the gas-phase, was the basis for a now obsolete industrial route acrolein:
:CHCHO + CHO → HOCHCHCHO
:HOCHCHCHO → CH=CHCHO + HO
Presently 3-hydroxypropionaldehyde is an intermediate in the production of pentaerythritol. Hydrogenation of reuterin gives 1,3-propanediol. | 1 | Applied and Interdisciplinary Chemistry |
In the Arctic, commercial fisheries are threatened because acidification harms calcifying organisms which form the base of the Arctic food webs (pteropods and brittle stars, see above). Acidification threatens Arctic food webs from the base up. Arctic food webs are considered simple, meaning there are few steps in the food chain from small organisms to larger predators. For example, pteropods are "a key prey item of a number of higher predators – larger plankton, fish, seabirds, whales". Both pteropods and sea stars serve as a substantial food source and their removal from the simple food web would pose a serious threat to the whole ecosystem. The effects on the calcifying organisms at the base of the food webs could potentially destroy fisheries. | 0 | Theoretical and Fundamental Chemistry |
In 1855, physiologist Adolf Fick first reported his now well-known laws governing the transport of mass through diffusive means. Ficks work was inspired by the earlier experiments of Thomas Graham, which fell short of proposing the fundamental laws for which Fick would become famous. Ficks law is analogous to the relationships discovered at the same epoch by other eminent scientists: Darcys law (hydraulic flow), Ohms law (charge transport), and Fourier's Law (heat transport).
Ficks experiments (modeled on Grahams) dealt with measuring the concentrations and fluxes of salt, diffusing between two reservoirs through tubes of water. It is notable that Ficks work primarily concerned diffusion in fluids, because at the time, diffusion in solids was not considered generally possible. Today, Ficks Laws form the core of our understanding of diffusion in solids, liquids, and gases (in the absence of bulk fluid motion in the latter two cases). When a diffusion process does not follow Ficks laws (which happens in cases of diffusion through porous media and diffusion of swelling penetrants, among others), it is referred to as non-Fickian'. | 0 | Theoretical and Fundamental Chemistry |
* Carotid bodies and aortic bodies detect changes primarily in pCO and H ion concentration. They also sense decrease in partial pressure of O, but to a lesser degree than for pCO and H ion concentration.
* The chemoreceptor trigger zone is an area of the medulla in the brain that receives inputs from blood-borne drugs or hormones, and communicates with the vomiting center (area postrema) to induce vomiting.
* Primary cilia play important roles in chemosensation. In adult tissues, these cilia regulate cell proliferation in response to external stimuli, such as tissue damage. In humans, improper functioning of primary cilia is associated with important diseases known as ciliopathies. | 0 | Theoretical and Fundamental Chemistry |
In materials science, an interstitial defect is a type of point crystallographic defect where an atom of the same or of a different type, occupies an interstitial site in the crystal structure. When the atom is of the same type as those already present they are known as a self-interstitial defect. Alternatively, small atoms in some crystals may occupy interstitial sites, such as hydrogen in palladium. Interstitials can be produced by bombarding a crystal with elementary particles having energy above the displacement threshold for that crystal, but they may also exist in small concentrations in thermodynamic equilibrium. The presence of interstitial defects can modify the physical and chemical properties of a material. | 1 | Applied and Interdisciplinary Chemistry |
Digital PCR can detect rare sequences such as HIV DNA in patients with HIV, and DNA from fecal bacteria in ocean and other water samples for assessing water quality. dPCR can detect sequences as rare as 1 in every 1,250,000 cells. | 1 | Applied and Interdisciplinary Chemistry |
Using a light microscope, it is just barely possible to see tiny green granules—which were named grana. With electron microscopy, it became possible to see the thylakoid system in more detail, revealing it to consist of stacks of flat thylakoids which made up the grana, and long interconnecting stromal thylakoids which linked different grana.
In the transmission electron microscope, thylakoid membranes appear as alternating light-and-dark bands, 8.5 nanometers thick.
The three-dimensional structure of the thylakoid membrane system haz been disputed. Many models have been proposed, the most prevalent being the helical model, in which granum stacks of thylakoids are wrapped by helical stromal thylakoids. Another model known as the bifurcation model, which was based on the first electron tomography study of plant thylakoid membranes, depicts the stromal membranes as wide lamellar sheets perpendicular to the grana columns which bifurcates into multiple parallel discs forming the granum-stroma assembly. The helical model was supported by several additional works, but ultimately it was determined in 2019 that features from both the helical and bifurcation models are consolidated by newly discovered left-handed helical membrane junctions. Likely for ease, the thylakoid system is still commonly depicted by older "hub and spoke" models where the grana are connected to each other by tubes of stromal thylakoids.
Grana consist of a stacks of flattened circular granal thylakoids that resemble pancakes. Each granum can contain anywhere from two to a hundred thylakoids, though grana with 10–20 thylakoids are most common. Wrapped around the grana are multiple parallel right-handed helical stromal thylakoids, also known as frets or lamellar thylakoids. The helices ascend at an angle of ~20°, connecting to each granal thylakoid at a bridge-like slit junction.
The stroma lamellae extend as large sheets perpendicular to the grana columns. These sheets are connected to the right-handed helices either directly or through bifurcations that form left-handed helical membrane surfaces. The left-handed helical surfaces have a similar tilt angle to the right-handed helices (~20°), but ¼ the pitch. Approximately 4 left-handed helical junctions are present per granum, resulting in a pitch-balanced array of right- and left-handed helical membrane surfaces of different radii and pitch that consolidate the network with minimal surface and bending energies. While different parts of the thylakoid system contain different membrane proteins, the thylakoid membranes are continuous and the thylakoid space they enclose form a single continuous labyrinth. | 0 | Theoretical and Fundamental Chemistry |
One modification of the Hiyama coupling utilizes a silacyclobutane ring and a fluoride source that is hydrated as shown below. This mimics the use of an alkoxysilane/organosilanol rather than the use of alkylsilane. The mechanism of this reaction, using a fluoride source, allowed for the design of future reactions that can avoid the use of the fluoride source. | 0 | Theoretical and Fundamental Chemistry |
The BIG-NSE offers a structured curriculum for obtaining the degree of "Doctor" within 3 years. The main characteristic of the BIG-NSE is a comprehensive integration and mentoring programme for its students, especially foreign students. It includes:
* An "Initial Phase", with intensive support, especially for administrative and integration aspects. Preparation of a schedule by the students themselves during the first semester.
* Continuous supervision by two professors/senior scientists and one mentor.
* Regular evaluation of the students’ work/study achievements.
* Continuous support for all professional and social aspects.
* Regular lectures presented by guest scientists from all over the world.
* Language and soft skill courses.
* Financial support for scientific and teaching materials. | 1 | Applied and Interdisciplinary Chemistry |
HBr can be prepared by distillation of a solution of sodium bromide or potassium bromide with phosphoric acid or sulfuric acid:
: KBr + HSO → KHSO + HBr
Concentrated sulfuric acid is less effective because it oxidizes HBr to bromine:
: 2 HBr + HSO → Br + SO + 2 HO
The acid may be prepared by:
* reaction of bromine with water and sulfur:
*: 2 Br + S + 2 HO → 4 HBr + SO
* bromination of tetralin:
*: CH + 4 Br → CHBr + 4 HBr
* reduction of bromine with phosphorous acid:
*: Br + HPO + HO → HPO + 2 HBr
Anhydrous hydrogen bromide can also be produced on a small scale by thermolysis of triphenylphosphonium bromide in refluxing xylene.
Hydrogen bromide prepared by the above methods can be contaminated with Br, which can be removed by passing the gas through a solution of phenol at room temperature in tetrachloromethane or other suitable solvent (producing 2,4,6-tribromophenol and generating more HBr in the process) or through copper turnings or copper gauze at high temperature. | 0 | Theoretical and Fundamental Chemistry |
The chemical composition of sporopollenin has long been elusive due to its unusual chemical stability, insolubility and resistance to degradation by enzymes and strong chemical reagents. It was once thought to consist of polymerised carotenoids but the application of more detailed analytical methods since the 1980s has shown that this is not correct. Analyses have revealed a complex biopolymer, containing mainly long-chain fatty acids, phenylpropanoids, phenolics and traces of carotenoids in a random co-polymer. It is likely that sporopollenin derives from several precursors that are chemically cross-linked to form a rigid structure. There is also good evidence that the chemical composition of sporopollenin is not the same in all plants, indicating it is a class of compounds rather than having one constant structure.
In 2019, thioacidolysis degradation and solid-state NMR was used to determine the molecular structure of pitch pine sporopollenin, finding it primarily composed of polyvinyl alcohol units alongside other aliphatic monomers, all crosslinked through a series of acetal linkages. Its complex and heterogeneous chemical structure give some protection from the biodegradative enzymes of bacteria, fungi and animals. Some aromatic structures based on p-coumarate and naringenin were also identified within the sporopollenin polymer. These can absorb ultraviolet light and thus prevent it penetrating further into the spore. This has relevance to the role of pollen and spores in transporting and dispersing the gametes of plants. The DNA of the gametes is readily damaged by the ultraviolet component of daylight. Sporopollenin thus provides some protection from this damage as well as a physically robust container.
Analysis of sporopollenin from the clubmoss Lycopodium in the late 1980s have shown distinct structural differences from that of flowering plants. In 2020, more detailed analysis of sporopollenin from Lycopodium clavatum provided more structural information. It showed a complete lack of aromatic structures and the presence of a macrocyclic backbone of polyhydroxylated tetraketide-like monomers with pseudo-aromatic 2-pyrone rings. These were crosslinked to a poly(hydroxy acid) chain by ether linkages to form the polymer. | 1 | Applied and Interdisciplinary Chemistry |
Cram and Reetz demonstrated that 1,3-stereocontrol is possible if the reaction proceeds through an acyclic transition state. The reaction of β-alkoxy aldehyde with allyltrimethylsilane showed good selectivity for the anti-1,3-diol, which was explained by the Cram polar model. The polar benzyloxy group is oriented anti to the carbonyl to minimize dipole interactions and the nucleophile attacks anti- to the bulkier (R) of the remaining two substituents. | 0 | Theoretical and Fundamental Chemistry |
Adult women in the United States consume on average half the AI, for men two-thirds. For all adults, fewer than 5% exceed the AI. Similarly, in the European Union, insufficient potassium intake is widespread. | 1 | Applied and Interdisciplinary Chemistry |
The proper combination of chemicals is selected for decellularization depending on the thickness, extracellular matrix composition, and intended use of the tissue or organ. For example, enzymes would not be used on a collagenous tissue because they disrupt the connective tissue fibers. However, when collagen is not present in a high concentration or needed in the tissue, enzymes can be a viable option for decellularization. The chemicals used to kill and remove the cells include acids, alkaline treatments, ionic detergents, non-ionic detergents, and zwitterionic detergents.
The ionic detergent, sodium dodecyl sulfate (SDS), is commonly used because of its high efficacy for lysing cells without significant damage to the ECM. Detergents act effectively to lyse the cell membrane and expose the contents to further degradation. After SDS lyses the cell membrane, endonucleases and exonucleases degrade the genetic contents, while other components of the cell are solubilized and washed out of the matrix. SDS is commonly used even though it has a tendency to slightly disrupt the ECM structure. Alkaline and acid treatments can be effective companions with an SDS treatment due to their ability to degrade nucleic acids and solubilize cytoplasmic inclusions.
The most well known non-ionic detergent is Triton X-100, which is popular because of its ability to disrupt lipid-lipid and lipid-protein interactions. Triton X-100 does not disrupt protein-protein interactions, which is beneficial to keeping the ECM intact. EDTA is a chelating agent that binds calcium, which is a necessary component for proteins to interact with one another. By making calcium unavailable, EDTA prevents the integral proteins between cells from binding to one another. EDTA is often used with trypsin, an enzyme that acts as a protease to cleave the already existing bonds between integral proteins of neighboring cells within a tissue. Together, the EDTA-Trypsin combination make a good team for decellularizing tissues. | 1 | Applied and Interdisciplinary Chemistry |
Silicon carbide is a semiconductor, which can be doped n-type by nitrogen or phosphorus and p-type by beryllium, boron, aluminium, or gallium. Metallic conductivity has been achieved by heavy doping with boron, aluminium or nitrogen.
Superconductivity has been detected in 3C-SiC:Al, 3C-SiC:B and 6H-SiC:B at similar temperatures ~1.5 K. A crucial difference is however observed for the magnetic field behavior between aluminium and boron doping: 3C-SiC:Al is type-II. In contrast, 3C-SiC:B is type-I, as is 6H-SiC:B. Thus the superconducting properties seem to depend more on dopant (B vs. Al) than on polytype (3C- vs 6H-). In an attempt to explain this dependence, it was noted that B substitutes at C sites in SiC, but Al substitutes at Si sites. Therefore, Al and B "see" different environments, in both polytypes. | 1 | Applied and Interdisciplinary Chemistry |
Fixed transfer stations are dedicated facilities installed strategically throughout the municipality that serve as drop off locations for collected fecal sludge. They may include a receiving station with screens, a tank for holding the collected waste, trash storage containers, and wash down facilities. These may be more appropriate for FSM programs using the "call-for-service" business model.
While static transfer stations are fixed tanks, mobile transfer stations are simply tanker trucks or trailers that work alongside the SVVs and actually do the longer haul transferring of the waste from the community to the treatment plant. Mobile transfer stations work best for scheduled desludging programs where there are no traffic restrictions or truck bans, and a relatively large number of homes that are inaccessible to the larger vehicles. | 1 | Applied and Interdisciplinary Chemistry |
Glycoproteins and glycolipids are by definition covalently bonded to carbohydrates. They are very abundant on the surface of the cell, and their interactions contribute to the overall stability of the cell. | 0 | Theoretical and Fundamental Chemistry |
Johann Juncker also created a very complete picture of phlogiston. When reading Stahl's work, he assumed that phlogiston was in fact very material. He, therefore, came to the conclusion that phlogiston has the property of levity, or that it makes the compound that it is in much lighter than it would be without the phlogiston. He also showed that air was needed for combustion by putting substances in a sealed flask and trying to burn them.
Guillaume-François Rouelle brought the theory of phlogiston to France, and he was a very influential scientist and teacher so it gained quite a strong foothold very quickly. Many of his students became very influential scientists in their own right, Lavoisier included. The French viewed phlogiston as a very subtle principle that vanishes in all analysis, yet it is in all bodies. Essentially they followed straight from Stahl's theory.
Giovanni Antonio Giobert introduced Lavoisiers work in Italy. Giobert won a prize competition from the Academy of Letters and Sciences of Mantua in 1792 for his work refuting phlogiston theory. He presented a paper at the of Turin on 18 March 1792, entitled ("Chemical examination of the doctrine of phlogiston and the doctrine of pneumatists in relation to the nature of water"), which is considered the most original defence of Lavoisiers theory of water composition to appear in Italy. | 1 | Applied and Interdisciplinary Chemistry |
RPB3 is involved in RNA polymerase II assembly. A subcomplex of RPB2 and RPB3 appears soon after subunit synthesis. This complex subsequently interacts with RPB1. RPB3, RPB5, and RPB7 interact with themselves to form homodimers, and RPB3 and RPB5 together are able to contact all of the other RPB subunits, except RPB9. Only RPB1 strongly binds to RPB5. The RPB1 subunit also contacts RPB7, RPB10, and more weakly but most efficiently with RPB8. Once RPB1 enters the complex, other subunits such as RPB5 and RPB7 can enter, where RPB5 binds to RPB6 and RPB8 and RPB3 brings in RPB10, RPB 11, and RPB12. RPB4 and RPB9 may enter once most of the complex is assembled. RPB4 forms a complex with RPB7. | 1 | Applied and Interdisciplinary Chemistry |
Diols where the hydroxyl groups are separated by several carbon centers are generally prepared by hydrogenation of diesters of the corresponding dicarboxylic acids:
: (CH)(COR) + 4 H → (CH)(CHOH) + 2 HO + 2 ROH
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol are important precursors to polyurethanes. | 0 | Theoretical and Fundamental Chemistry |
Phytomining, sometimes called agromining, is the concept of extracting heavy metals from the soil using plants. Specifically, phytomining is for the purpose of economic gain. The approach exploits the existence of hyperaccumulators, proteins or compounds secreted by plants to bind certain metal ions. These extracted ores are called bio-ores. The approach has little practical value ("its commercial viability is limited") because it is slow and inefficient. | 1 | Applied and Interdisciplinary Chemistry |
A study published in Science in August 2022 indicated that perfluoroalkyl carboxylic acids (PFCAs) can be mineralized via heating in a polar aprotic solvent such as dimethyl sulfoxide. It reported that heating PFCAs in an 8 to 1 mixture of dimethyl sulfoxide and water at in the presence of sodium hydroxide caused the removal of the carboxylic acid group at the end of the carbon chain, creating a perfluoroanion that mineralizes into sodium fluoride and other salts such as sodium trifluoroacetate, formate, carbonate, oxalate, and glycolate. The process does not work on perfluorosulfonic acids such as PFOS. A more recent study published in Chemical Science shows breakdown of C-F bonds and their mineralization as YF or YF clusters. Another study in the Journal of the American Chemical Society described the PFAs breakdown using metal-organic frameworks (MOFs). | 0 | Theoretical and Fundamental Chemistry |
Food physical chemistry is considered to be a branch of Food chemistry concerned with the study of both physical and chemical interactions in foods in terms of physical and chemical principles applied to food systems, as well as the applications of physical/chemical techniques and instrumentation for the study of foods. This field encompasses the "physiochemical principles of the reactions and conversions that occur during the manufacture, handling, and storage of foods."
Food physical chemistry concepts are often drawn from rheology, theories of transport phenomena, physical and chemical thermodynamics, chemical bonds and interaction forces, quantum mechanics and reaction kinetics, biopolymer science, colloidal interactions, nucleation, glass transitions, and freezing, disordered/noncrystalline solids.
Techniques utilized range widely from dynamic rheometry, optical microscopy, electron microscopy, AFM, light scattering, X-ray diffraction/neutron diffraction, to MRI, spectroscopy (NMR, FT-NIR/IR, NIRS, ESR and EPR, CD/VCD, Fluorescence, FCS, HPLC, GC-MS, and other related analytical techniques.
Understanding food processes and the properties of foods requires a knowledge of physical chemistry and how it applies to specific foods and food processes. Food physical chemistry is essential for improving the quality of foods, their stability, and food product development. Because food science is a multi-disciplinary field, food physical chemistry is being developed through interactions with other areas of food chemistry and food science, such as food analytical chemistry, food process engineering/food processing, food and bioprocess technology, food extrusion, food quality control, food packaging, food biotechnology, and food microbiology. | 0 | Theoretical and Fundamental Chemistry |
The annual AP Chemistry examination, which is typically administered in May, is divided into two major sections (multiple-choice questions and free response essays). | 1 | Applied and Interdisciplinary Chemistry |
The main factor affecting the formal (or apparent) reduction potentials in biochemical or biological processes is the pH. To determine approximate values of formal reduction potentials, neglecting in a first approach changes in activity coefficients due to ionic strength, the Nernst equation has to be applied taking care to first express the relationship as a function of pH. The second factor to be considered are the values of the concentrations taken into account in the Nernst equation. To define a formal reduction potential for a biochemical reaction, the pH value, the concentrations values and the hypotheses made on the activity coefficients must always be clearly indicated. When using, or comparing, several formal (or apparent) reduction potentials they must also be internally consistent.
Problems may occur when mixing different sources of data using different conventions or approximations (i.e., with different underlying hypotheses). When working at the frontier between inorganic and biological processes (e.g., when comparing abiotic and biotic processes in geochemistry when microbial activity could also be at work in the system), care must be taken not to inadvertently directly mix standard reduction potentials ( versus SHE, pH = 0) with formal (or apparent) reduction potentials ( at pH = 7). Definitions must be clearly expressed and carefully controlled, especially if the sources of data are different and arise from different fields (e.g., picking and directly mixing data from classical electrochemistry textbooks ( versus SHE, pH = 0) and microbiology textbooks ( at pH = 7) without paying attention to the conventions on which they are based). | 1 | Applied and Interdisciplinary Chemistry |
Robert Guillaumont (born 26 February 1933 in Lyon) is a French chemist and honorary professor at the University of Paris-Saclay in Orsay (1967-1998), Member of the French Academy of Sciences and the French Academy of Technologies | 0 | Theoretical and Fundamental Chemistry |
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