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Many eukaryotic organisms have electron transport chains that differ from the much-studied mammalian enzymes described above. For example, plants have alternative NADH oxidases, which oxidize NADH in the cytosol rather than in the mitochondrial matrix, and pass these electrons to the ubiquinone pool. These enzymes do not transport protons, and, therefore, reduce ubiquinone without altering the electrochemical gradient across the inner membrane.
Another example of a divergent electron transport chain is the alternative oxidase, which is found in plants, as well as some fungi, protists, and possibly some animals. This enzyme transfers electrons directly from ubiquinol to oxygen.
The electron transport pathways produced by these alternative NADH and ubiquinone oxidases have lower ATP yields than the full pathway. The advantages produced by a shortened pathway are not entirely clear. However, the alternative oxidase is produced in response to stresses such as cold, reactive oxygen species, and infection by pathogens, as well as other factors that inhibit the full electron transport chain. Alternative pathways might, therefore, enhance an organism's resistance to injury, by reducing oxidative stress. | 1 | Biochemistry |
Levobupivacaine is an amino-amide anaesthetic that is similar in structure to bupivacaine, namely the S-enantiomer of bupivacaine. A lipophilic aromatic ring is linked to a hydrocarbon chain by an amide bond. The lipophilic components of levobupivacaine allow it to cross cell membraness and exert its local anaesthetic effect by causing a reversible blockade of open neuronal sodium channels. | 4 | Stereochemistry |
At room temperature and below, hydroxylamine-O-sulfonic acid reacts with ketones and aldehydes as a nucleophile to the corresponding oxime-O-sulfonic acids or their salts. The oxime-O-sulfonic acids of aldehydes react above room temperature upon elimination of sulfuric acid in high yields to nitriles.
Aliphatic ketones provide under similar conditions in very high yields oximes, arylalkyl ketones react in a Beckmann rearrangement to amides. When heated to reflux for several hours under acidic conditions (e.g., in the presence of concentrated formic acid) alicyclic ketones react to provide lactams in high yields.
Under basic conditions in the presence of primary amines, hydroxylamine-O-sulfonic acid forms with aldehydes and ketones (e.g. cyclohexanone) diaziridines, which can easily be oxidized to the more stable diazirines.
The reaction also provides substituted aziridines from simple aldehydes and ketones with high yield and diastereoselectivity.
1,2-Benzisoxazole is efficiently produced by nucleophilic attack of hydroxylamine-O-sulfonic acid to the carbonyl group of 2-hydroxybenzaldehyde followed by cyclization.
1,2-Benzisoxazole is a structural element in the antipsychotic risperidone and paliperidone, as well as the anticonvulsant zonisamide.
In a one-pot reaction, N-aryl[3,4-d]pyrazolopyrimidines are obtained in good yields from simple 4,6-dichloropyrimidine-5-carboxaldehyde,
which can be used as purine analogs for a wide range of diagnostic and therapeutic applications. | 0 | Organic Chemistry |
Techniques commonly used in the field of phytochemistry are extraction, isolation, and structural elucidation (MS,1D and 2D NMR) of natural products, as well as various chromatography techniques (MPLC, HPLC, and LC-MS). | 1 | Biochemistry |
A signal peptide (sometimes referred to as signal sequence, targeting signal, localization signal, localization sequence, transit peptide, leader sequence or leader peptide) is a short peptide (usually 16-30 amino acids long) present at the N-terminus (or occasionally nonclassically at the C-terminus or internally) of most newly synthesized proteins that are destined toward the secretory pathway.
These proteins include those that reside either inside certain organelles (the endoplasmic reticulum, Golgi or endosomes), secreted from the cell, or inserted into most cellular membranes. Although most type I membrane-bound proteins have signal peptides, most type II and multi-spanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which biochemically resembles a signal sequence except that it is not cleaved. They are a kind of target peptide. | 1 | Biochemistry |
The advantage of this method, aside from its relatively straightforward nature, is the fact that with a large enough solid surface, multiple droplets can be deposited in various locations on the sample to determine heterogeneity. The reproducibility of particular values of the contact angle will reflect the heterogeneity of the surfaces energy properties. Conversely, the disadvantage is that if the sample is only large enough for one droplet, then it will be difficult to determine heterogeneity, or consequently to assume homogeneity. This is particularly true because conventional, commercially available goniometers do not swivel the camera/backlight set up relative to the stage, and thus can only show the contact angle at two points: the right and the left edge of the droplet. In addition to this, this measurement is hampered by its inherent subjectivity, as the placement of the lines is determined either by the user looking at the pictures or by the image analysis softwares definition of the lines. | 7 | Physical Chemistry |
* between any kind of biomolecules including proteins, DNA, RNA, peptides, small molecules, fragments and ions
* for interactions with high molecular weight complexes, large molecule assemblies, even with liposomes, vesicles, nanodiscs, nanoparticles and viruses
* in any buffer, including serum and cell lysate
* in competition experiments (for example with substrate and inhibitors)
Stoichiometry | 1 | Biochemistry |
Chemical oxidation analysers inject the sample into a chamber with phosphoric acid followed by persulfate. The analysis is separated into two steps. One removes inorganic carbon by acidification and purging. After removal of inorganic carbon persulfate is added and the sample is either heated or bombarded with UV light from a mercury vapor lamp. Free radicals form persulfate and react with any carbon available to form carbon dioxide. The carbon from both determination (steps) is either run through membranes which measure the conductivity changes that result from the presence of varying amounts of carbon dioxide, or purged into and detected by a sensitive NDIR detector. Same as the combustion analyser, the total carbon formed minus the inorganic carbon gives a good estimate of the total organic carbon in the sample.
This method is often used in online applications because of its low maintenance requirements. | 3 | Analytical Chemistry |
polySia was discovered in E. coli K-235 by Barry and Goebel in 1957. E. coli is an encapsulated, gram-negative bacteria in which Barry and Goebel studied, pinpointing polySia, which they called colominic acid. Following this discovery, multiple other bacterial capsules abundant in glycans were found to contain polySia. This included Neisseia meningitidis serogroups B and C in 1975. This was done by the use of a horse anti-polySia polyclonal antibody, being one of the first effective immunochemical probes. This was revolutionary as the anti-polySia antibodies were used to find polySia on proteins and cells. Mannheimia haemolytica A2, Moraxella nonliquifaciens, and E. coli K92 were found in 2013. Due to the capsule containing polySia, many scientists have tried to generate vaccines for these specific bacteria, notoriously difficult to target. However, their successes have been numbered as α2,8-polySia is naturally produced by humans. Another issue is that polySia found in bacteria does not produce a solid or consistent immune response.
Another method of polySia detection relies on molecular labeling with fluorescence. This process, started in 1998, involves exposing α2→8-linked N-acylneuraminic acid (Neu5Acyl) to periodate oxidation causing the terminals to be oxidized and in between untouched. If C compounds are observed after this exposure it indicates the presence of polySia. The way these can be numbered is by anion exchange chromatography after periodate oxidation with the label 1,2-diamino-4,5-methylenedioxybenzene (DMB) on C and C. It is known that there are many different structures of polySia and these were difficult to recognize and detect until this fluorescent labeling, making it very advantageous. | 1 | Biochemistry |
Taxol resulted from the tail addition of the Ojima lactam to alcohol 51, which is baccatin III (the original target molecule of the Danishefsky synthesis). Alcohol 51 was derived from the allylic oxidation of α-acylketone 49. Compound 49 was ultimately derived from the Heck reaction of enol triflate 38, which was used to close the B-ring. Enol triflate 38 resulted from a rearrangement of compound 31 after protection of its hydroxyl group. Compound 31 was derived from the connection of the A and C rings with aldehyde 21 combining with the vinyllithium reagent derived from cyanohydrin 29. Cyanohydrin 29 originated as the ethyl isopropyl ketone (22). Aldehyde 21 was obtained from compound 17, which was the product of the opening of ketal 12. Ketal 12 was ultimately derived from the Wieland-Miescher ketone (1). | 0 | Organic Chemistry |
A ρ factor (Rho factor) is a bacterial protein involved in the termination of transcription. Rho factor binds to the transcription terminator pause site, an exposed region of single stranded RNA (a stretch of 72 nucleotides) after the open reading frame at C-rich/G-poor sequences that lack obvious secondary structure.
Rho factor is an essential transcription protein in bacteria. In Escherichia coli, it is a ~274.6 kD hexamer of identical subunits. Each subunit has an RNA-binding domain and an ATP-hydrolysis domain. Rho is a member of the RecA/SF5 family of ATP-dependent hexameric helicases that function by wrapping nucleic acids around a single cleft extending around the entire hexamer. Rho functions as an ancillary factor for RNA polymerase.
There are two types of transcriptional termination in bacteria, rho-dependent termination and intrinsic termination (also called Rho-independent termination). Rho-dependent terminators account for about half of the E. coli factor-dependent terminators. Other termination factors discovered in E. coli include Tau and nusA. Rho-dependent terminators were first discovered in bacteriophage genomes. | 1 | Biochemistry |
Zuclopenthixol is available in three major preparations:
* As zuclopenthixol decanoate (Clopixol Depot, Cisordinol Depot), it is a long-acting intramuscular injection. Its main use is as a long-acting injection given every two or three weeks to people with schizophrenia who have a poor compliance with medication and suffer frequent relapses of illness. There is some evidence it may be more helpful in managing aggressive behaviour.
* As zuclopenthixol acetate (Clopixol-Acuphase, Cisordinol-Acutard), it is a shorter-acting intramuscular injection used in the acute sedation of psychotic inpatients. The effect peaks at 48–72 hours providing 2–3 days of sedation.
* As zuclopenthixol dihydrochloride (Clopixol, Cisordinol), it is a tablet used in the treatment of schizophrenia in those who are compliant with oral medication.
It is also used in the treatment of acute bipolar mania. | 4 | Stereochemistry |
The principal mission of iron foundry is the conversion of iron oxides (purified iron ores) to iron metal. This reduction is usually effected using a reducing atmosphere consisting of some mixture of natural gas, hydrogen (H), and carbon monoxide. The byproduct is carbon dioxide. | 8 | Metallurgy |
In recent years many industrial efforts have focused on tuning the color of lights using polyfluorenes. It was found that by doping green or red emitting materials into polyfluorenes one could tune the color emitted by the polymers. Since polyfluorene homopolymers emit higher energy blue light, they can transfer energy via Förster resonance energy transfer (FRET) to lower energy emitters. In addition to doping, color of polyfluorenes can be tuned by copolymerizing the fluorene monomers with other low band gap monomers. Researchers at the Dow Chemical Company synthesized several fluorene-based copolymers by alternating copolymerization using 5,5-dibromo-2,2-bithiophene which showed yellow emission and 4,7-dibromo-2,1,3-benzothiadiazole, which showed green emission. Other copolymerizations are also suitable; researchers at IBM performed random copolymerization of fluorene with 3,9(10)-dibromoperylene,4,4-dibromo-R-cyanostilbene, and 1,4-bis(2-(4-bromophenyl)-1-cyanovinyl)-2-(2-ethylhexyl)-5-methoxybenzene. Only a small amount of the co-monomer, approximately 5%, was needed to tune the emission of the polyfluorene from blue to yellow. This example further illustrates that by introducing monomers that have a lower band gap than the fluorene monomer, one can tune the color that is emitted by the polymer.
Substitution at the nine position with various moieties has also been examined as a means to control the color emitted by polyfluorene. In the past researchers have tried putting alkyl substituents on the ninth position, however it has been found that by putting bulkier groups, such as alkoxyphenyl groups, the polymers had enhanced blue emission stability and superior polymer light-emitting diode performance (compared to polymers which have alkyl substituents at the ninth position). | 7 | Physical Chemistry |
Phosphonates feature tetrahedral phosphorus centers. They are structurally closely related to (and often prepared from) phosphorous acid.
Phosphonate salts are the result of deprotonation of phosphonic acids, which are diprotic acids:
:RPO(OH) + NaOH → HO + RPO(OH)(ONa) (monosodium phosphonate)
:RPO(OH)(ONa) + NaOH → HO + RPO(ONa) (disodium phosphonate)
Phosphonate esters are the result of condensation of phosphonic acids with alcohols. | 0 | Organic Chemistry |
There are two main types of transmetalation, redox-transmetalation (RT) and redox-transmetalation/ligand-exchange (RTLE). Below, M is usually a 4d or 5d transition metal and M is usually a main group or 3d transition metal. By looking at the electronegativities of the metals and ligands, one can predict whether the RT or RTLE reaction will proceed and what products the reaction will yield. For example, one can predict that the addition of 3 HgPh to 2 Al will yield 3 Hg and 2 AlPh because Hg is a more electronegative element than Al. | 0 | Organic Chemistry |
A component is any part of a molecule or molecules that function as a unit in a pericyclic reaction. A component consists of one or more atoms and any of the following types of associated orbitals:
* An isolated p- or sp-orbital (unfilled or filled, symbol ω)
* A conjugated π system (symbol π)
* A σ bond (symbol σ)
The electron count of a component is the number of electrons in the orbital(s) of the component:
* The electron count of an unfilled ω orbital (i.e., an empty p orbital) is 0, while that of a filled ω orbital (i.e., a lone pair) is 2.
* The electron count of a conjugated π system with n double bonds is 2n (or 2n + 2, if a (formal) lone pair from a heteroatom or carbanion is conjugated thereto).
* The electron count of a σ bond is 2.
The bond topology of a component can be suprafacial and antarafacial:
* The relationship is suprafacial (symbol: s) when the interactions with the π system or p orbital occur on the same side of the nodal plane (think syn). For a σ bond, it corresponds to interactions occurring on the two "interior" lobes or two "exterior" lobes of the bond.
* The relationship is antarafacial (symbol: a) when the interactions with the π system or p orbital occur on opposite sides of the nodal plane (think anti). For a σ bond, it corresponds to interactions occurring on one "interior" lobe and one "exterior" lobe of the bond.
Using this notation, all pericyclic reactions can be assigned a descriptor, consisting of a series of symbols N, connected by + signs and enclosed in brackets, describing, in order, the type of orbital(s), number of electrons, and bond topology involved for each component. Some illustrative examples follow:
* The Diels-Alder reaction (a (4+2)-cycloaddition) is [4 + 2].
* The 1,3-dipolar cycloaddition of ozone and an olefin in the first step of ozonolysis (a (3+2)-cycloaddition) is [4 + 2].
* The cheletropic addition of sulfur dioxide to 1,3-butadiene (a (4+1)-cheletropic addition) is [0 + 4] + [2 + 4].
* The Cope rearrangement (a [3,3]-sigmatropic shift) is [2 + 2 + 2] or [2 + 2 + 2].
* The [1,3]-alkyl migration with inversion at carbon discovered by Berson (a [1,3]-sigmatropic shift) is [2 + 2].
* The conrotatory electrocyclic ring closing of 1,3-butadiene (a 4π-electrocyclization) is [4].
* The conrotatory electrocyclic ring opening of cyclobutene (a reverse 4π-electrocyclization) is [2 + 2] or [2 + 2].
* The disrotatory electrocyclic ring closing of 1,3-cyclooctadien-5-ide anion (a 6π-electrocyclization) is [6].
* A Wagner-Meerwein shift of a carbocation (a [1,2]-sigmatropic shift) is [0 + 2].
Antarafacial and suprafacial are associated with (conrotation or inversion) and (disrotation or retention), respectively. A single descriptor may correspond to two pericyclic processes that are chemically distinct, that a reaction and its microscopic reverse are often described with two different descriptors, and that a single process may have more than a one correct descriptor. One can verify, using the pericyclic selection rule given below, that all of these reactions are allowed processes. | 7 | Physical Chemistry |
The SK channel family contains 4 members – SK1, SK2, SK3, and SK4. SK4 is often referred to as IK (Intermediate conductance) due to its higher conductance 20 – 80 pS. | 1 | Biochemistry |
δ-Aminolevulinic acid (also dALA, δ-ALA, 5ALA or 5-aminolevulinic acid), an endogenous non-proteinogenic amino acid, is the first compound in the porphyrin synthesis pathway, the pathway that leads to heme in mammals, as well as chlorophyll in plants.
5ALA is used in photodynamic detection and surgery of cancer. | 1 | Biochemistry |
For safety and convenience diazomethane is always prepared as needed as a solution in ether and used as such. It converts carboxylic acids to methyl esters and phenols into their methyl ethers. The reaction is thought to proceed via proton transfer from carboxylic acid to diazomethane to give methyldiazonium cation, which reacts with the carboxylate ion to give the methyl ester and nitrogen gas. Labeling studies indicate that the initial proton transfer is faster than the methyl transfer step. Since proton transfer is required for the reaction to proceed, this reaction is selective for the more acidic carboxylic acids (pK ~ 5) and phenols (pK ~ 10) over aliphatic alcohols (pK ~ 15).
In more specialized applications, diazomethane and homologues are used in Arndt-Eistert synthesis and the Büchner–Curtius–Schlotterbeck reaction for homologation.
Diazomethane reacts with alcohols or phenols in presence of boron trifluoride (BF) to give methyl ethers.
Diazomethane is also frequently used as a carbene source. It readily takes part in 1,3-dipolar cycloadditions. | 0 | Organic Chemistry |
The age of a water parcel can be estimated by the CFC partial pressure (pCFC) age or SF partial pressure (pSF) age. The pCFC age of a water sample is defined as:
where [CFC] is the measured CFC concentration (pmol kg) and F is the solubility of CFC gas in seawater as a function of temperature and salinity. The CFC partial pressure is expressed in units of 10–12 atmospheres or parts-per-trillion (ppt). The solubility measurements of CFC-11 and CFC-12 have been previously measured by Warner and Weiss Additionally, the solubility measurement of CFC-113 was measured by Bu and Warner and SF by Wanninkhof et al. and Bullister et al. Theses authors mentioned above have expressed the solubility (F) at a total pressure of 1 atm as:
where F = solubility expressed in either mol l or mol kg atm,
T = absolute temperature,
S = salinity in parts per thousand (ppt),
a, a, a, b, b, and b are constants to be determined from the least squares fit to the solubility measurements. This equation is derived from the integrated Van 't Hoff equation and the logarithmic Setchenow salinity dependence.
It can be noted that the solubility of CFCs increase with decreasing temperature at approximately 1% per degree Celsius.
Once the partial pressure of the CFC (or SF) is derived, it is then compared to the atmospheric time histories for CFC-11, CFC-12, or SF in which the pCFC directly corresponds to the year with the same. The difference between the corresponding date and the collection date of the seawater sample is the average age for the water parcel. The age of a parcel of water can also be calculated using the ratio of two CFC partial pressures or the ratio of the SF partial pressure to a CFC partial pressure. | 2 | Environmental Chemistry |
Several lines of evidence suggest that intelectins recognize microbes and may function as an innate immune defense protein. Tunicate intelectin is an opsonin for phagocytosis by hemocyte. Amphioxus intelectin has been shown to agglutinate bacteria. In zebrafish and rainbow trout, intelectin expression is stimulated upon microbial exposure. Mammals such as sheep and mice also upregulate intelectin expression upon parasitic infection. Increase in intelectin expression upon microbial exposure support the hypothesis that intelectins play a role in the immune system. | 1 | Biochemistry |
The levonorgestrel intrauterine system (LNG-IUS) is a type of long-term birth control that releases the progestin into the uterine cavity. Levonorgestrel is released at a constant, gradual rate of 0.02 mg per day by the polydimethylsiloxane membrane of the device, which renders it effective for up to five years. Because it is inserted directly into the uterus, levonorgestrel is present in the endometrium in much higher concentrations that would result from a LNG-containing oral pill; the LNG-IUS delivers 391 ng of levonorgestrel to the inner uterine region while a comparable oral contraceptive delivers only 1.35 ng. This high level of levonorgestrel impedes the function of the endometrium, making it hostile for sperm transport, fertilization, and implantation of an ovum. | 4 | Stereochemistry |
*1847 fellow of the Royal Scottish Society of Arts
*1848 a member of the Glasgow Philosophical Society (now Royal Philosophical Society of Glasgow)
*1855 elected Fellow of the Faculty of Physicians and Surgeons, the University of Glasgow
*1855 elected member (1857–59 Hon. Sec), the Philosophical Institute of Victoria, later to become the Royal Society of Victoria
*1860 vice-president of Royal Society of Victoria | 3 | Analytical Chemistry |
* MicroMSI is endorsed by the NGA.
* Opticks is an open-source remote sensing application.
* Multispec is freeware multispectral analysis software.
* Gerbil is open source multispectral visualization and analysis software. | 7 | Physical Chemistry |
A familiar radical reaction is combustion. The oxygen molecule is a stable diradical, best represented by O–O. Because spins of the electrons are parallel, this molecule is stable. While the ground state of oxygen is this unreactive spin-unpaired (triplet) diradical, an extremely reactive spin-paired (singlet) state is available. For combustion to occur, the energy barrier between these must be overcome. This barrier can be overcome by heat, requiring high temperatures. The triplet-singlet transition is also "forbidden". This presents an additional barrier to the reaction. It also means molecular oxygen is relatively unreactive at room temperature except in the presence of a catalytic heavy atom such as iron or copper.
Combustion consists of various radical chain reactions that the singlet radical can initiate. The flammability of a given material strongly depends on the concentration of radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material has been consumed, termination reactions again dominate and the flame dies out. As indicated, promotion of propagation or termination reactions alters flammability. For example, because lead itself deactivates radicals in the gasoline-air mixture, tetraethyl lead was once commonly added to gasoline. This prevents the combustion from initiating in an uncontrolled manner or in unburnt residues (engine knocking) or premature ignition (preignition).
When a hydrocarbon is burned, a large number of different oxygen radicals are involved. Initially, hydroperoxyl radical (HOO) are formed. These then react further to give organic hydroperoxides that break up into hydroxyl radicals (HO). | 2 | Environmental Chemistry |
In mineralogy, epitaxy is the overgrowth of one mineral on another in an orderly way, such that certain crystal directions of the two minerals are aligned. This occurs when some planes in the lattices of the overgrowth and the substrate have similar spacings between atoms.
If the crystals of both minerals are well formed so that the directions of the crystallographic axes are clear then the epitaxic relationship can be deduced just by a visual inspection.
Sometimes many separate crystals form the overgrowth on a single substrate, and then if there is epitaxy all the overgrowth crystals will have a similar orientation. The reverse, however, is not necessarily true. If the overgrowth crystals have a similar orientation there is probably an epitaxic relationship, but it is not certain.
Some authors consider that overgrowths of a second generation of the same mineral species should also be considered as epitaxy, and this is common terminology for semiconductor scientists who induce epitaxic growth of a film with a different doping level on a semiconductor substrate of the same material. For naturally produced minerals, however, the International Mineralogical Association (IMA) definition requires that the two minerals be of different species.
Another man-made application of epitaxy is the making of artificial snow using silver iodide, which is possible because hexagonal silver iodide and ice have similar cell dimensions. | 3 | Analytical Chemistry |
Conductometric sensing involves measuring the change in conductive properties of the sample solution or a medium. The reaction between the biomolecule and analyte changes the ionic species concentration, leading to a change in the solution electrical conductivity or current flow. Two metal electrodes are separated at a certain distance and an AC potential is applied across the electrodes, causing a current flow between the electrodes. During a biorecognition event the ionic composition changes, using an ohmmeter the change in conductance can be measured. | 1 | Biochemistry |
The absorption of levetiracetam tablets and oral solution is rapid and essentially complete. The bioavailability of levetiracetam is close to 100 percent, and the effect of food on absorption is minor. | 4 | Stereochemistry |
Pseudoephedrine is a sympathomimetic amine. Its principal mechanism of action relies on its direct action on the adrenergic receptor system. The vasoconstriction that pseudoephedrine produces is believed to be principally an α-adrenergic receptor response.
Pseudoephedrine acts on α- and β2-adrenergic receptors, to cause vasoconstriction and relaxation of smooth muscle in the bronchi, respectively. α-Adrenergic receptors are located on the muscles lining the walls of blood vessels. When these receptors are activated, the muscles contract, causing the blood vessels to constrict (vasoconstriction). The constricted blood vessels now allow less fluid to leave the blood vessels and enter the nose, throat, and sinus linings, which results in decreased inflammation of nasal membranes, as well as decreased mucus production. Thus, by constriction of blood vessels, mainly those located in the nasal passages, pseudoephedrine causes a decrease in the symptoms of nasal congestion. Activation of β2-adrenergic receptors produces relaxation of smooth muscle of the bronchi, causing bronchial dilation and in turn decreasing congestion (although not fluid) and difficulty breathing. | 4 | Stereochemistry |
The Goldbeter–Koshland kinetics describe a steady-state solution for a 2-state biological system. In this system, the interconversion between these two states is performed by two enzymes with opposing effect. One example would be a protein Z that exists in a phosphorylated form Z and in an unphosphorylated form Z; the corresponding kinase Y and phosphatase X interconvert the two forms. In this case we would be interested in the equilibrium concentration of the protein Z (Goldbeter–Koshland kinetics only describe equilibrium properties, thus no dynamics can be modeled). It has many applications in the description of biological systems.
The Goldbeter–Koshland kinetics is described by the Goldbeter–Koshland function:
with the constants
Graphically the function takes values between 0 and 1 and has a sigmoid behavior. The smaller the parameters J and J the steeper the function gets and the more of a switch-like behavior is observed. Goldbeter–Koshland kinetics is an example of ultrasensitivity. | 7 | Physical Chemistry |
Immunomagnetic separation involves purified antigens biotinylated and bound to streptoavidin-coated paramagnetic particles. The raw sample is mixed with the beads, then a specific magnet is used to hold the target organisms against the vial wall and the non-bound material is poured off. This method can be used to recover specific indicator bacteria. | 3 | Analytical Chemistry |
Operando spectroscopy has become a vital tool for surface chemistry. Nanotechnology, used in materials science, involves active catalytic sites on a reagent surface with at least one dimension in the nano-scale of approximately 1–100 nm. As particle size decreases, surface area increases. This results in a more reactive catalytic surface. The reduced scale of these reactions affords several opportunities while presenting unique challenges; for example, due to the very small size of the crystals (sometimes <5 nm), any X-ray crystallography diffraction signal may be very weak.
As catalysis is a surface process, one particular challenge in catalytic studies is resolving the typically weak spectroscopic signal of the catalytically active surface against that of the inactive bulk structure. Moving from the micro to the nano scale increases the surface to volume ratio of the particles, maximizing the signal of the surface relative to that of the bulk.
Furthermore, as the scale of the reaction decreases towards nano scale, individual processes can be discerned that would otherwise be lost in the average signal of a bulk reaction composed of multiple coincident steps and species such as spectators, intermediates, and reactive sites. | 7 | Physical Chemistry |
1,3-BPG has a very similar role in the Calvin cycle to its role in the glycolytic pathway. For this reason both reactions are said to be analogous. However the reaction pathway is effectively reversed. The only other major difference between the two reactions is that NADPH is used as an electron donor in the calvin cycle whilst NAD is used as an electron acceptor in glycolysis. In this reaction cycle 1,3BPG originates from 3-phosphoglycerate and is made into glyceraldehyde 3-phosphate by the action of specific enzymes.
Contrary to the similar reactions of the glycolytic pathway, 1,3BPG in the Calvin cycle does not produce ATP but instead uses it. For this reason it can be considered to be an irreversible and committed step in the cycle. The outcome of this section of the cycle is an inorganic phosphate is removed from 1,3BPG as a hydrogen ion and two electrons are added to the compound.
In complete reverse of the glycolytic pathway reaction, the enzyme phosphoglycerate kinase catalyses the reduction of the carboxyl group of 1,3BPG to form an aldehyde instead. This reaction also releases an inorganic phosphate molecule which is subsequently used as energy for the donation of electrons from the conversion of NADPH to NADP. Overseeing this latter stage of the reaction is the enzyme glyceraldehyde-phosphate dehydrogenase. | 5 | Photochemistry |
The strength with which oxygen binds to hemoglobin is affected by several factors. These factors shift or reshape the oxyhemoglobin dissociation curve. A shift to right indicates that the hemoglobin under study has a decreased affinity for oxygen. This makes it more difficult for hemoglobin to bind to oxygen (requiring a higher partial pressure of oxygen to achieve the same oxygen saturation), but it makes it easier for the hemoglobin to release oxygen bound to it.
The effect of this shift of the curve increases the partial pressure of oxygen in the tissues when it is most needed, such as during exercise, or hemorrhagic shock.
In contrast, the curve is shifted to the left by the opposite of these conditions.
This shift indicates that the hemoglobin under study has an increased affinity for oxygen so that hemoglobin binds oxygen more easily, but unloads it more reluctantly.
Left shift of the curve is a sign of hemoglobin's increased affinity for oxygen (e.g. at the lungs).
Similarly, right shift shows decreased affinity, as would appear with an increase in either body temperature, hydrogen ions, 2,3-bisphosphoglycerate (2,3-BPG) concentration or carbon dioxide concentration.
Note:
* Left shift: higher O affinity
* Right shift: lower O affinity
* fetal hemoglobin has higher O affinity than adult hemoglobin; primarily due to much-reduced affinity to 2,3-bisphosphoglycerate .
The causes of shift to right can be remembered using the mnemonic, "CADET, face Right!" for CO, Acid, 2,3-DPG, Exercise and Temperature. Factors that move the oxygen dissociation curve to the right are those physiological states where tissues need more oxygen. For example, during exercise, muscles have a higher metabolic rate, and consequently need more oxygen, produce more carbon dioxide and lactic acid, and their temperature rises. | 1 | Biochemistry |
cDNA is created from a mature mRNA from a eukaryotic cell with the use of reverse transcriptase. In eukaryotes, a poly-(A) tail (consisting of a long sequence of adenine nucleotides) distinguishes mRNA from tRNA and rRNA and can therefore be used as a primer site for reverse transcription. This has the problem that not all transcripts, such as those for the histone, encode a poly-A tail. | 1 | Biochemistry |
In the early 17th century, ironworkers in Western Europe had developed the cementation process for carburizing wrought iron. Wrought iron bars and charcoal were packed into stone boxes, then sealed with clay to be held at a red heat continually tended in an oxygen-free state immersed in nearly pure carbon (charcoal) for up to a week. During this time, carbon diffused into the surface layers of the iron, producing cement steel or blister steel—also known as case hardened, where the portions wrapped in iron (the pick or axe blade) became harder, than say an axe hammer-head or shaft socket which might be insulated by clay to keep them from the carbon source. The earliest place where this process was used in England was at Coalbrookdale from 1619, where Sir Basil Brooke had two cementation furnaces (recently excavated in 2001–2005). For a time in the 1610s, he owned a patent on the process, but had to surrender this in 1619. He probably used Forest of Dean iron as his raw material, but it was soon found that oregrounds iron was more suitable. The quality of the steel could be improved by faggoting, producing the so-called shear steel. | 8 | Metallurgy |
A Euclidean graph in three-dimensional space is a pair (V, E), where V is a set of vertices (sometimes called points or nodes) and E is a set of edges (sometimes called bonds or spacers) where each edge joins two vertices. There is a tendency in the polyhedral and chemical literature to refer to geometric graphs as nets (contrast with polyhedral nets), and the nomenclature in the chemical literature differs from that of graph theory. | 3 | Analytical Chemistry |
Homologation reactions like the Kowalski ester homologation provide simple examples of insertion process in organic synthesis. In the Arndt-Eistert reaction, a methylene unit is inserted into the carboxyl-carbon bond of carboxylic acid to form the next acid in the homologous series. Organic Syntheses provides the example of t-BOC protected (S)-phenylalanine (2-amino-3-phenylpropanoic acid) being reacted sequentially with triethylamine, ethyl chloroformate, and diazomethane to produce the α-diazoketone, which is then reacted with silver trifluoroacetate / triethylamine in aqueous solution to generate the t-BOC protected form of (S)-3-amino-4-phenylbutanoic acid.
Mechanistically, the α-diazoketone undergoes a Wolff rearrangement to form a ketene in a 1,2-rearrangement. Consequently, the methylene group α- to the carboxyl group in the product is the methylene group from the diazomethane reagent. The 1,2-rearrangement has been shown to conserve the stereochemistry of the chiral centre as the product formed from t-BOC protected (S)-phenylalanine retains the (S) stereochemistry with a reported enantiomeric excess of at least 99%.
A related transformation is the Nierenstein reaction in which a diazomethane methylene group is inserted into the carbon-chlorine bond of an acid chloride to generate an α-chloro ketone. An example, published in 1924, illustrates the reaction in a substituted benzoyl chloride system:
Perhaps surprisingly, α-bromoacetophenone is the minor product when this reaction is carried out with benzoyl bromide, a dimeric dioxane being the major product. Organic azides also provide an example of an insertion reaction in organic synthesis and, like the above examples, the transformations proceed with loss of nitrogen gas. When tosyl azide reacts with norbornadiene, a ring expansion reaction takes place in which a nitrogen atom is inserted into a carbon-carbon bond α- to the bridge head:
The Beckmann rearrangement is another example of a ring expanding reaction in which a heteroatom is inserted into a carbon-carbon bond. The most important application of this reaction is the conversion of cyclohexanone to its oxime, which is then rearranged under acidic conditions to provide ε-caprolactam, the feedstock for the manufacture of Nylon 6. Annual production of caprolactam exceeds 2 billion kilograms.
Carbenes undergo both intermolecular and intramolecular insertion reactions. Cyclopentene moieties can be generated from sufficiently long-chain ketones by reaction with trimethylsilyldiazomethane, (CH)Si–CHN:
Here, the carbene intermediate inserts into a carbon-hydrogen bond to form the carbon-carbon bond needed to close the cyclopentene ring. Carbene insertions into carbon-hydrogen bonds can also occur intermolecularly:
Carbenoids are reactive intermediates that behave similarly to carbenes. One example is the chloroalkyllithium carbenoid reagent prepared in situ from a sulfoxide and t-BuLi which inserts into the carbon-boron bond of a pinacol boronic ester: | 0 | Organic Chemistry |
Hellmut Friedrich Fischmeister (14 May 1927 – 6 November 2019) was an Austrian metallurgist who was a pioneer in powder metallurgy. | 8 | Metallurgy |
The concept that individuals might have a "metabolic profile" that could be reflected in the makeup of their biological fluids was introduced by Roger Williams in the late 1940s, who used paper chromatography to suggest characteristic metabolic patterns in urine and saliva were associated with diseases such as schizophrenia. However, it was only through technological advancements in the 1960s and 1970s that it became feasible to quantitatively (as opposed to qualitatively) measure metabolic profiles. The term "metabolic profile" was introduced by Horning, et al. in 1971 after they demonstrated that gas chromatography-mass spectrometry (GC-MS) could be used to measure compounds present in human urine and tissue extracts. The Horning group, along with that of Linus Pauling and Arthur B. Robinson led the development of GC-MS methods to monitor the metabolites present in urine through the 1970s.
Concurrently, NMR spectroscopy, which was discovered in the 1940s, was also undergoing rapid advances. In 1974, Seeley et al. demonstrated the utility of using NMR to detect metabolites in unmodified biological samples. This first study on muscle highlighted the value of NMR in that it was determined that 90% of cellular ATP is complexed with magnesium. As sensitivity has improved with the evolution of higher magnetic field strengths and magic angle spinning, NMR continues to be a leading analytical tool to investigate metabolism. Recent efforts to utilize NMR for metabolomics have been largely driven by the laboratory of Jeremy K. Nicholson at Birkbeck College, University of London and later at Imperial College London. In 1984, Nicholson showed H NMR spectroscopy could potentially be used to diagnose diabetes mellitus, and later pioneered the application of pattern recognition methods to NMR spectroscopic data.
In 1994 and 1996, liquid chromatography mass spectrometry metabolomics experiments were performed by Gary Siuzdak while working with Richard Lerner (then president of the Scripps Research Institute) and Benjamin Cravatt, to analyze the cerebral spinal fluid from sleep deprived animals. One molecule of particular interest, oleamide, was observed and later shown to have sleep inducing properties. This work is one of the earliest such experiments combining liquid chromatography and mass spectrometry in metabolomics.
In 2005, the first metabolomics tandem mass spectrometry database, METLIN, for characterizing human metabolites was developed in the Siuzdak laboratory at the Scripps Research Institute. METLIN has since grown and as of December, 2023, METLIN contains MS/MS experimental data on over 930,000 molecular standards and other chemical entities, each compound having experimental tandem mass spectrometry data generated from molecular standards at multiple collision energies and in positive and negative ionization modes. METLIN is the largest repository of tandem mass spectrometry data of its kind. The dedicated academic journal Metabolomics first appeared in 2005, founded by its current editor-in-chief Roy Goodacre.
In 2005, the Siuzdak lab was engaged in identifying metabolites associated with sepsis and in an effort to address the issue of statistically identifying the most relevant dysregulated metabolites across hundreds of LC/MS datasets, the first algorithm was developed to allow for the nonlinear alignment of mass spectrometry metabolomics data. Called XCMS, it has since (2012) been developed as an online tool and as of 2019 (with METLIN) has over 30,000 registered users.
On 23 January 2007, the Human Metabolome Project, led by David S. Wishart, completed the first draft of the human metabolome, consisting of a database of approximately 2,500 metabolites, 1,200 drugs and 3,500 food components. Similar projects have been underway in several plant species, most notably Medicago truncatula and Arabidopsis thaliana for several years.
As late as mid-2010, metabolomics was still considered an "emerging field". Further, it was noted that further progress in the field depended in large part, through addressing otherwise "irresolvable technical challenges", by technical evolution of mass spectrometry instrumentation.
In 2015, real-time metabolome profiling was demonstrated for the first time. | 1 | Biochemistry |
EGF; LDLR; LRP1; LRP10; LRP1B; LRP2; LRP4; LRP5;
LRP5L; LRP6; LRP8; NID1; NID2; SORL1; VLDLR; | 1 | Biochemistry |
Aquatic carbon occurs in different forms. Firstly, a division is made between organic and inorganic carbon. Organic carbon is a mixture of organic compounds originating from detritus or primary producers. It can be divided into POC (particulate organic carbon; particles > 0.45 μm) and DOC (dissolved organic carbon; particles .
Likewise, inorganic carbon also consists of a particulate (PIC) and a dissolved phase (DIC). PIC mainly consists of carbonates (e.g., CaCO), DIC consists of carbonate (CO), bicarbonate (HCO), CO and a negligibly small fraction of carbonic acid (HCO). The inorganic carbon compounds exist in equilibrium that depends on the pH of the water. DIC concentrations in freshwater range from about zero in acidic waters to 60 mg C L in areas with carbonate-rich sediments.
POC can be degraded to form DOC; DOC can become POC by flocculation. Inorganic and organic carbon are linked through aquatic organisms. CO is used in photosynthesis (P) by for instance macrophytes, produced by respiration (R), and exchanged with the atmosphere. Organic carbon is produced by organisms and is released during and after their life; e.g., in rivers, 1–20% of the total amount of DOC is produced by macrophytes. Carbon can enter the system from the catchment and is transported to the oceans by rivers and streams. There is also exchange with carbon in the sediments, e.g., burial of organic carbon, which is important for carbon sequestration in aquatic habitats.
Aquatic systems are very important in global carbon sequestration; e.g., when different European ecosystems are compared, inland aquatic systems form the second largest carbon sink (19–41 Tg C y); only forests take up more carbon (125–223 Tg C y). | 2 | Environmental Chemistry |
Non-metallic inclusions arise because of many physical-chemical effects that occur in molten and consolidated metal during production.
Non-metallic inclusions that arise because of different reactions during metal production are called natural or indigenous. They include oxides, sulfides, nitrides and phosphides.
Apart from natural inclusions there are also parts of slag, refractories, material of a casting mould (the material the metal contacts during production) in the metal. Such non-metallic inclusions are called foreign, accidental or exogenous.
Most inclusions in the reduction smelting of metal formed because of admixture dissolubility decreasing during cooling and consolidation.
The present-day level of steel production technology allows the elimination of most natural and foreign inclusions from the metal. However its general content in different steels can vary between wide limits and has a big influence on the metal properties. | 8 | Metallurgy |
Space stations transmitting solar power have appeared in science-fiction works like Isaac Asimovs "Reason" (1941), that centers around the troubles caused by the robots operating the station. Asimovs short story "The Last Question" also features the use of SBSP to provide limitless energy for use on Earth.
Erc Kotani and John Maddox Robertss 2000 novel The Legacy of Prometheus' posits a race between several conglomerates to be
the first to beam down a gigawatt of energy from a solar satellite in geosynchronous orbit.
In Ben Bovas novel PowerSat (2005), an entrepreneur strives to prove that his companys nearly completed power satellite and spaceplane (a means of getting maintenance crews to the satellite efficiently) are both safe and economically viable, while terrorists with ties to oil producing nations attempt to derail these attempts through subterfuge and sabotage.
Various aerospace companies have also showcased imaginative future solar power satellites in their corporate vision videos, including Boeing, Lockheed Martin, and United Launch Alliance.
The solar satellite is one of three means of producing energy in the browser-based game OGame. The city building game SimCity 2000 also features a Microwave Power Plant.
In the 1978 anime TV series Future Boy Conan, SBSP enables the country of Industria to develop geomagnetic weapons, more powerful than nuclear weapons, that destroy entire continents. | 7 | Physical Chemistry |
Metallurgy in China has a long history, with the earliest metal objects in China dating back to around 3,000 BCE. The majority of early metal items found in China come from the North-Western Region (mainly Gansu and Qinghai, 青海). China was the earliest civilization to use the blast furnace and produce cast iron. | 8 | Metallurgy |
The identity operation corresponds to doing nothing to the object. Because every molecule is indistinguishable from itself if nothing is done to it, every object possesses at least the identity operation. The identity operation is denoted by or . In the identity operation, no change can be observed for the molecule. Even the most asymmetric molecule possesses the identity operation. The need for such an identity operation arises from the mathematical requirements of group theory. | 7 | Physical Chemistry |
Solenopsins are described as toxic against vertebrates and invertebrates. For example, the compound known as isosolenopsin A has been demonstrated to have strong insecticidal effects which may play a central role in the biology of fire ants.
In addition to its toxicity, solenopsis has a number of other biological activities. It inhibits angiogenesis in vitro via the phosphoinositide 3-kinase (PI3K) signaling pathway, inhibits neuronal nitric oxide synthase (nNOS) in a manner that appears to be non-competitive with -arginine, and inhibits quorum-sensing signaling in some bacteria. The biological activities of solenopsins have led researchers to propose a number of biotechnological and biomedical applications for these compounds. For instance, mentioned anti-bacterial and interference in quorum-sensing signalling apparently provide solenopsins with considerable anti-biofilm activity, which suggests the potential of analogs as new disinfectants and surface-conditioning agents. Also, solenopsins have been demonstrated to inhibit cell division and viability of Trypanosoma cruzi, the cause of Chagas disease, which suggests these alkaloids as potential chemotherapeutic drugs.
Solenopsin and analogs share structural and biological properties with the sphingolipid ceramide, a major endogenous regulator of cell signaling, inducing mitophagy and anti-proliferative effects in different tumor cell lines.
Synthetic analogs of solenopsin are being studied for the potential treatment of psoriasis. | 0 | Organic Chemistry |
Norgestrel (rac-13-ethyl-17α-ethynyl-19-nortestosterone), the racemic mixture containing levonorgestrel and dextronorgestrel, was discovered by Hughes and colleagues at Wyeth in 1963 via structural modification of norethisterone (17α-ethynyl-19-nortestosterone). It was the first progestogen to be manufactured via total chemical synthesis. Norgestrel was introduced for medical use as a combined birth control pill with ethinylestradiol under the brand name Eugynon in Germany in 1966 and under the brand name Ovral in the United States 1968, and as a progestogen-only pill under the brand name Ovrette in the United States in 1973. Following its discovery, norgestrel had been licensed by Wyeth to Schering AG, which separated the racemic mixture into its two optical isomers and identified levonorgestrel (13β-ethyl-17α-ethynyl-19-nortestosterone) as the active component of the mixture. Levonorgestrel was first studied in humans by 1970, and was introduced for medical use in Germany as a combined birth control pill with ethinylestradiol under the brand name Neogynon in August 1970. A more widely used formulation, containing lower doses of ethinylestradiol and levonorgestrel, was introduced under the brand name Microgynon by 1973. In addition to combined formulations, levonorgestrel was introduced as a progestogen-only pill under the brand names Microlut by 1972 and Microval by 1974. Many other formulations and brand names of levonorgestrel-containing birth control pills have also been marketed.
Levonorgestrel, taken alone in a single high dose, was first evaluated as a form of emergency contraception in 1973. It was the second progestin to be evaluated for such purposes, following a study of quingestanol acetate in 1970. In 1974, the Yuzpe regimen, which consisted of high doses of a combined birth control pill containing ethinylestradiol and norgestrel, was described as a method of emergency contraception by A. Albert Yuzpe and colleagues, and saw widespread interest. Levonorgestrel-only emergency contraception was introduced under the brand name Postinor by 1978. Ho and Kwan published the first study comparing levonorgestrel only and the Yuzpe regimen as methods of emergency contraception in 1993 and found that they had similar effectiveness but that levonorgestrel alone was better-tolerated. In relation to this, the Yuzpe regimen has largely been replaced as a method of emergency contraception by levonorgrestrel-only preparations. Levonorgestrel-only emergency contraception was approved in the United States under the brand name Plan B in 1999, and has also been marketed widely elsewhere throughout the world under other brand names such as Levonelle and NorLevo in addition to Postinor. In 2013, the Food and Drug Administration approved Plan B One-Step for sale over-the-counter in the United States without a prescription or age restriction.
Levonorgestrel has also been introduced for use as a progestogen-only intrauterine device under the brand names Mirena and Skyla among others, as a progestogen-only birth control implant under the brand names Norplant and Jadelle, as a combined oral tablet with estradiol valerate for menopausal hormone therapy under the brand name Klimonorm, and as a combined transdermal patch with estradiol for menopausal hormone therapy under the brand name Climara Pro. Ester prodrugs of levonorgestrel such as levonorgestrel acetate and levonorgestrel butanoate have been developed and studied as other forms of birth control such as long-acting progestogen-only injectable contraceptives and contraceptive vaginal rings, but have not been marketed for medical use. | 4 | Stereochemistry |
Assimilation can be broadly defined as a process where a mass of magma wholly or partially homogenizes with materials derived from the wall rock of the magma body. Assimilation is a popular mechanism to partly explain the felsification of ultramafic and mafic magmas as they rise through the crust: a hot primitive melt intruding into a cooler, felsic crust will melt the crust and mix with the resulting melt. This then alters the composition of the primitive magma. Also, pre-existing mafic host rocks can be assimilated by very hot primitive magmas.
Effects of assimilation on the chemistry and evolution of magma bodies are to be expected, and have been clearly proven in many places. In the early 20th century there was a lively discussion on the relative importance of the process in igneous differentiation. More recent research has shown, however, that assimilation has a fundamental role in altering the trace element and isotopic composition of magmas, in formation of some economically important ore deposits, and in causing volcanic eruptions. | 9 | Geochemistry |
An example of an electrophilic substitution using a diazomethyl compound is that of a reaction between an acyl halide and diazomethane, for example the first step in the Arndt-Eistert synthesis. | 0 | Organic Chemistry |
Mitogen-activated protein kinase (MAPK) networks can be found in eukaryotic cells. MAPK pathways in plants are known to regulate cell growth, cell development, cell death, and cell responses to environmental stimuli. Only a few of the MAPK mechanism components are known and have been studied. The components such as Arabidopsis MAPKKKs YODA, ANP2/ANP3, and MP3K6/MP3K7 functions in the development of the cell. MEKK1 and ANP1 function in the response to environmental stress. Unfortunately, only eight out of the twenty mitogen-activated protein kinases have been studied. The most commonly studied MAPKs are MPK3, MPK4, and MPK6, which are activated by a diversity of stimuli including abiotic stresses, pathogens, and oxidative stressors. MPK4 negatively regulates biotic stress signaling, while MPK3 and MPK6 function as positive mediators of defense responses. The plant has these positive and negative mediators allowing for normal plant growth and development, which has been proven true by the severely dwarfed phenotype of mpk4 and the embryo lethal phenotype of mpk3 and mpk6 mutants. | 1 | Biochemistry |
Isomers are types of molecules that share a chemical formula but have difference geometries, resulting in different properties:
* A pure substance is composed of only one type of isomer of a molecule (all have the same geometrical structure).
* Structural isomers have the same chemical formula but different physical arrangements, often forming alternate molecular geometries with very different properties. The atoms are not bonded (connected) together in the same orders.
** Functional isomers are special kinds of structural isomers, where certain groups of atoms exhibit a special kind of behavior, such as an ether or an alcohol.
* Stereoisomers may have many similar physicochemical properties (melting point, boiling point) and at the same time very different biochemical activities. This is because they exhibit a handedness that is commonly found in living systems. One manifestation of this chirality or handedness is that they have the ability to rotate polarized light in different directions.
* Protein folding concerns the complex geometries and different isomers that proteins can take. | 4 | Stereochemistry |
Underwater archaeology is a subfield of archaeology that focuses on the exploration of submerged archaeological sites in seas, rivers, and other bodies of water. In 1988, the Maryland Maritime Archeology Program (MMAP) was established with the goal to manage and explore the various underwater archaeological sites that line the Chesapeake Bay. This was in response to the National Abandoned Shipwreck Act passed in 1987, which gave ownership of historically significant shipwrecks to those states with proper management programs.
Water makes up 25% of the State of Maryland and there are over 550 submerged archaeological sites that have been located across the Chesapeake Bay and its surrounding watersheds. Ranging from 12,000-year-old, precolonial native settlements to shipwrecks from as recent as World War II, the MMAP researches thousands of years worth of history in these archaeological sites. Susan Langley has been Marylands State Underwater Archaeologist, one of only nine state-appointed underwater archaeologists in the United States, since assuming the role in 1995. Before Langley was hired, only 1% of the underwater archaeological sites in the bay area had been examined. Over the next 10 years, Langley made significant improvements to the MMAP's marine technology, allowing her and her team to explore 34% of the underwater archaeological sites by 2004. | 2 | Environmental Chemistry |
Phenol extraction is a widely used technique for purifying nucleic acid samples from cell lysates. To obtain nucleic acids, the cell must be lysed, and the nucleic acids separated from other cell components.
Phenol is a polar substance with a higher density than water (1.07 g/cm compared to water's 1.00 g/cm). When suspended in a water-phenol solution, denatured proteins and unwanted cell components dissolve in the phenol, while polar nucleic acids dissolve in the water phase. The solution may then be centrifuged to separate the phenol and water into distinct organic and aqueous phases. Purified nucleic acids can be precipitated from the aqueous phase of the solution.
Phenol is often used in combination with chloroform. Adding an equal volume of chloroform and phenol ensures a distinct separation between the aqueous and organic phases. Chloroform and phenol are miscible and create a denser solution than phenol alone, aiding the separation of the organic and aqueous layers. This addition of chloroform is useful when removing the aqueous phase to obtain a purified nucleic acid sample.
The pH of the solution must be adjusted specifically for each type of extraction. For DNA extraction, the pH is adjusted to 7.0–8.0. For RNA-specific extraction, the pH is adjusted to 4.5. At pH 4.5, hydrogen ions neutralize the negative charges on the phosphate groups, causing DNA to dissolve in the organic phase while allowing RNA to be isolated separately in the aqueous phase. | 1 | Biochemistry |
The specifics for binding of π cyclic systems are much more complex and depend on the electrons, the HOMO, and the LUMO in each individual case of molecules. Cyclic π systems can bind monohapto or polyhapto depending on the individual situation. This means that π bonds can bind individually to the metal or there can be a single bond from the center of a benzene or cyclopentadienyl complex. Of course the bonding modes (η, η, η, etc.) determine the number of donated electrons (1, 3, 5, etc.). The diversity of these cyclic complexes allows for a seemingly endless number of metallic structures. | 6 | Supramolecular Chemistry |
Volcanic gases are gases given off by active (or, at times, by dormant) volcanoes. These include gases trapped in cavities (vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from lava, from volcanic craters or vents. Volcanic gases can also be emitted through groundwater heated by volcanic action.
The sources of volcanic gases on Earth include:
* primordial and recycled constituents from the Earth's mantle,
* assimilated constituents from the Earth's crust,
* groundwater and the Earth's atmosphere.
Substances that may become gaseous or give off gases when heated are termed volatile substances. | 2 | Environmental Chemistry |
Solvated electrons are involved in electrode processes, a broad area with many technical applications (electrosynthesis, electroplating, electrowinning).
A specialized use of sodium-ammonia solutions is the Birch reduction. Other reactions where sodium is used as a reducing agent also are assumed to involve solvated electrons, e.g. the use of sodium in ethanol as in the Bouveault–Blanc reduction.
Work by Cullen et al. showed that metal-ammonia solutions can be used to intercalate a range of layered materials, which can then be exfoliated in polar, aprotic solvents, to produce ionic solutions of two-dimensional materials. An example of this is the intercalation of graphite with potassium and ammonia, which is then exfoliated by spontaneous dissolution in THF to produce a graphenide solution. | 0 | Organic Chemistry |
Originally, the use of laser-induced shock waves on metals to achieve property or functional benefits was referred to as laser shock processing, a broader, more inclusive term. As it happened, laser peening was the first commercial aspect of laser shock processing. However, laser-induced shock waves have found uses in other industrial applications outside of surface enhancement technologies.
One application is for metal shaping or forming. By selectively laser shocking areas on the surface of metal sheets or plates, or smaller items such as airfoils, the associated compressive residual stresses cause the material to flex in a controllable manner. In this way a particular shape can be imparted to a component, or a distorted component might be brought back into the desired shape. Thus, this process is capable of bringing manufactured parts back into design tolerance limits and form shaping thin section parts.
Another variation is to use the shock wave for spallation testing of materials. This application is based on the behavior of shockwaves to reflect from the rear free surface of a work piece as a tensile wave. Depending on the material properties and the shock wave characteristics, the reflected tensile wave may be strong enough to form microcracks or voids near the back surface, or actually "blow-off" or spall material from the back surface. This approach has some value for testing ballistic materials.
Use of laser shocks to measure the bond strength of coatings on metals has been developed over a period of years in France called LASAT for Laser Adhesion Test. This application is also based on the behavior of shockwaves to reflect from the rear free surface of a work piece as a tensile wave. If the back surface is coated with an adherent coating, the tensile wave can be tailored to fracture the bond upon reflection from the surface. By controlling the characteristics of the shock wave, the bond strength of the coating can be measured, or alternatively, determined in a comparative sense.
Careful tailoring of the shockwave shape and intensity has also enabled the inspection of bonded composite structures via laser shocking. The technology, termed Laser Bond Inspection initiates a shockwave that reflects off the backside of a bonded structure and returns as a tensile wave. As the tensile wave passes back through the adhesive bond, depending on the strength of the bond and the peak tensile stress of the stress wave, the tensile wave will either pass through the bond or rupture it. By controlling the pressure of the tensile wave this procedure is capable of reliably locally testing adhesion strength between bonded joints. This technology is most often found in application to bonded fiber composite material structures but has also been shown to be successful in evaluating bonds between metal-composite material. Fundamental issues are also studied to characterize and quantify the effect of shock wave produced by laser inside these complex materials. | 8 | Metallurgy |
Long-term weight management is directly proportional to calories absorbed from feeding; nevertheless, myriad non-caloric factors also play biologically significant roles (not covered here) in estimating energy intake. In counting energy expenditure, the use of a resting measurement (RMR) is the most accurate method for estimating the major portion of Total daily energy expenditure (TEE), thereby giving the closest approximations when planning & following a Calorie Intake Plan. Thus, estimation of REE by indirect calorimetry is strongly recommended for accomplishing long-term weight management, a conclusion reached and maintained due to ongoing observational research by well-respected institutions such as the USDA, AND (previously ADA), ACSM, and internationally by the WHO. | 1 | Biochemistry |
Toll-like receptors bind and become activated by different ligands, which, in turn, are located on different types of organisms or structures. They also have different adapters to respond to activation and are located sometimes at the cell surface and sometimes to internal cell compartments. Furthermore, they are expressed by different types of leucocytes or other cell types: | 1 | Biochemistry |
Levomilnacipran has a high oral bioavailability of 92% and a low plasma protein binding of 22%. It is metabolized in the liver by the cytochrome P450 enzyme CYP3A4, thereby making the medication susceptible to grapefruit-drug interactions. The drug has an elimination half-life of approximately 12 hours, allowing for once-daily administration. Levomilnacipran is excreted in urine. | 4 | Stereochemistry |
Salts or esters of cyclic polyphosphoric acids are often called "metaphosphates". What are commonly called trimetaphosphates actually have a mixture of ring sizes. A general formula for such cyclic compounds is where x = number of phosphoric units in the molecule.
When metaphosphoric acids lose their hydrogens as , cyclic anions called metaphosphates are formed. An example of a compound with such an anion is sodium hexametaphosphate (), used as a sequestrant and a food additive. | 0 | Organic Chemistry |
Dredging is the removal of sediment, plant species, and debris from an aquatic area. Industry, travel, and recreation throughout wetlands often requires the dredging of canals, especially by oil industry to get out to their offshore drills through coastal wetlands. Canals widen after being dredged because of the increased water flow and loss of plant life, both attributing to increased erosion. It is estimated that there are 4,572 miles of canals south of the Intracoastal Waterway, not including Lake Pontchartrain and Lake Maurepas, and that canals alone attribute to 6.53 square miles of land loss per year in the United States. The permits required to dredge these canals include stipulations of refilling, but these are not often enforced. John M. Barry, along with a group of private lawyers and coastal experts, filed a lawsuit in 2013 against 97 corporations who had violated their permits in Louisiana’s coastal wetlands in response to this. It is referred to as “the most ambitious environmental lawsuit ever” by the New York Times and has been met with political resistance. | 9 | Geochemistry |
A mitotoxin is a cytotoxic molecule targeted to specific cells by a mitogen. Generally found in snake venom. Mitotoxins are responsible for mediating cell death by interfering with protein or DNA synthesis. Some mechanisms by which mitotoxins can interfere with DNA or protein synthesis include the inactivation of ribosomes or the inhibition of complexes in the mitochondrial electron transport chain. These toxins have a very high affinity and level of specificity for the receptors that they bind to. Mitotoxins bind to receptors on cell surfaces and are then internalized into cells via receptor-mediated endocytosis. Once in the endosome, the receptor releases its ligand and a mitotoxin can mediate cell death.
There are different classes of mitotoxins, each acting on a different type of cell or system. The mitotoxin classes that have been identified thus far include: interleukin-based, transferrin based, epidermal growth factor-based, nerve growth factor-based, insulin-like growth factor-I-based, and fibroblast growth factor-based mitotoxins. Because of the high affinity and specificity of mitotoxin binding, they present the possibility of creating precise therapeutic agents. A major one of these possibilities is the potential usage of growth factor-based mitotoxins as anti-neoplastic agents that can modulate the growth of melanomas. | 1 | Biochemistry |
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 | Biochemistry |
Clone Manager is a commercial bioinformatics software work suite of Sci-Ed, that supports molecular biologists with data management and allows them to perform certain in silico preanalysis.
This type of bioinformatics software is used for managing, analyzing and visualizing DNA and protein sequence data essential for molecular biology.
For enzyme read control, sequence processing of identical individuals, cloning simulation, graphic map drawing, primer design and analysis, global and local sequence alignment, similarity search, laboratory scale sequence assembly projects A comprehensive set of tools. | 1 | Biochemistry |
To first order, δCu values in organisms are driven by the δCu values of source materials. The δCu values of various soils from different regions have been found to vary from -0.34 to +0.33‰ depending on the biogeochemical processes taking place in the soil and the ligands with which Cu complexes. Organic-rich soils generally have lighter δCu values than mineral soils because the organic layers result from plant litter, which is isotopically light.
In plants, δCu values vary between the different components (seeds, roots, stem and leaves). The δCu values the roots of rice, lettuce, tomato and durum wheat plants were found to be 0.5 to 1.0‰ Cu-depleted relative to their source, while their shoots were up to 0.5‰ lighter than the roots. Seeds appear to be the most isotopically light component of plants, followed by leaves, then stems.
Rivers sampled throughout the world have a range of dissolved δCu values from +0.02 to +1.45‰. The average δCu values of the Amazon, Brahmaputra and Nile rivers are 0.69, 0.64 and 0.58‰, respectively. The average δCu value of the Chang Jiang river is 1.32‰, while that of the Missouri river is 0.13‰. | 9 | Geochemistry |
*Feedstock
**Microbial oil
***Oleaginous microorganism
**Palm oil
**Soybean oil
**Coconut oil
**Vegetable fats and oils
**Jatropha
**Animal fat
**Waste oil
Common feedstock used in biodiesel production include:
*Yellow grease (recycled vegetable oil)
*Vegetable oil fuel
*Tallow
Lignocellulose generates byproducts that act as enzyme inhibitors, such as acetic acid, furfural, formic acid, vanillin, and these chemical inhibitors affect cell growth.
Recycled oil is processed to remove impurities from cooking, storage, and handling, such as dirt, charred food, and water. Virgin oils are refined, but not to a food-grade level. Degumming to remove phospholipids and other plant matter is common, though refinement processes vary. Water is removed because its presence during base-catalyzed transesterification results in the saponification (hydrolysis) of the triglycerides, producing soap instead of biodiesel.
A sample of the cleaned feedstock is then tested via titration against a standardized base solution, to determine the concentration of free fatty acids present in the vegetable oil sample. The acids are then either removed (typically through neutralization), or are esterified to produce biodiesel (or glycerides). | 0 | Organic Chemistry |
Plasmid DNA may appear in one of five conformations, which (for a given size) run at different speeds in a gel during electrophoresis. The conformations are listed below in order of electrophoretic mobility (speed for a given applied voltage) from slowest to fastest:
* Nicked open-circular DNA has one strand cut.
* Relaxed circular DNA is fully intact with both strands uncut but has been enzymatically relaxed (supercoils removed). This can be modeled by letting a twisted extension cord unwind and relax and then plugging it into itself.
* Linear DNA has free ends, either because both strands have been cut or because the DNA was linear in vivo. This can be modeled with an electrical extension cord that is not plugged into itself.
* Supercoiled (or covalently closed-circular) DNA is fully intact with both strands uncut, and with an integral twist, resulting in a compact form. This can be modeled by twisting an extension cord and then plugging it into itself.
* Supercoiled denatured DNA is like supercoiled DNA, but has unpaired regions that make it slightly less compact; this can result from excessive alkalinity during plasmid preparation.
The rate of migration for small linear fragments is directly proportional to the voltage applied at low voltages. At higher voltages, larger fragments migrate at continuously increasing yet different rates. Thus, the resolution of a gel decreases with increased voltage.
At a specified, low voltage, the migration rate of small linear DNA fragments is a function of their length. Large linear fragments (over 20 kb or so) migrate at a certain fixed rate regardless of length. This is because the molecules respirate, with the bulk of the molecule following the leading end through the gel matrix. Restriction digests are frequently used to analyse purified plasmids. These enzymes specifically break the DNA at certain short sequences. The resulting linear fragments form bands after gel electrophoresis. It is possible to purify certain fragments by cutting the bands out of the gel and dissolving the gel to release the DNA fragments.
Because of its tight conformation, supercoiled DNA migrates faster through a gel than linear or open-circular DNA. | 1 | Biochemistry |
Volcanic gases were directly responsible for approximately 3% of all volcano-related deaths of humans between 1900 and 1986. Some volcanic gases kill by acidic corrosion; others kill by asphyxiation. Some volcanic gases including sulfur dioxide, hydrogen chloride, hydrogen sulfide and hydrogen fluoride react with other atmospheric particles to form aerosols. | 2 | Environmental Chemistry |
Some chemists have also considered the 2-norbornyl cation to be best represented by the nortricyclonium ion, a C-symmetric protonated nortricyclene. This depiction was first invoked to partially explain results of a C isotope scrambling experiment. The molecular orbital representation of this structure involves an in-phase interaction between sp-hybridized orbitals from carbons 1, 2 and 6 and the 1s atomic orbital on a shared hydrogen atom (see Figure 5). | 7 | Physical Chemistry |
An early application of TRMS was in the observation of flash photolysis process. It took advantage of a time-of-flight mass analyzer.
TRMS currently finds applications in the monitoring of organic reactions, formation of reactive intermediates, enzyme-catalyzed reactions, convection, protein folding, extraction, and other chemical and physical processes. | 1 | Biochemistry |
Survivin has been a target of attention in recent years for cancer immunotherapy, as it is an antigen that is expressed mostly in cancer cells and absent in normal cells. This is because survivin is deemed to be a crucial player in tumour survival. There has been much evidence accumulated over the years that shows survivin as a strong T-cell-activating antigen, and clinical trials have already been initiated to prove its usefulness in the clinic. | 1 | Biochemistry |
RNA sequencing has taken over microarray and SAGE technology in recent years, as noted in 2016, and has become the most efficient way to study transcription and gene expression. This is typically done by next-generation sequencing.
A subset of sequenced RNAs are small RNAs, a class of non-coding RNA molecules that are key regulators of transcriptional and post-transcriptional gene silencing, or RNA silencing. Next-generation sequencing is the gold standard tool for non-coding RNA discovery, profiling and expression analysis. | 1 | Biochemistry |
Ziegler and coworkers reacted an allyl iodide with the azaenolate to generate a chiral hydrocarbon chain. To avoid loss of the enantiomeric purity of the product, the authors used cupric acetate to regenerate the carbonyl group, obtaining only moderate yield for the cleavage of C=N bond but good enantioselectivity (ee = 89%). The ketone was transformed after several steps into denticulatin A and B - polypropionate metabolites isolated from Siphonaria Denticulata. | 0 | Organic Chemistry |
In the US, more copper is recovered and put back into service from recycled material than is derived from newly mined ore. Copper's recycle value is so great that premium-grade scrap normally has at least 95% of the value of primary metal from newly mined ore. In Europe, about 50% of copper demand comes from recycling (as of 2016).
, recycled copper provided 35% of total worldwide copper usage. | 8 | Metallurgy |
The high error rate (0.01-0.001) of standard NGS platforms introduced during sample preparation or sequencing is a major limitation for the detection of variants present in a small fraction of cells. Due to the duplex tagging system and use of information in both strands of DNA, duplex sequencing has significantly decreased the error rate of sequencing about 10 million fold using both SSCS and DCS method. | 1 | Biochemistry |
* Free download location of SahysMod software from : [http://www.waterlog.info/software.htm] or from : [http://www.waterlog.info/sahysmod.htm] | 9 | Geochemistry |
*ATP2C1 NM_014382
*ATP5A1 NM_004046 Homo sapiens ATP synthase, H+ transporting, mitochondrial F1 complex, alpha
*ATP5B NM_001686
*ATP5C1 NM_005174
*ATP5D NM_001687 Homo sapiens ATP synthase, H+ transporting, mitochondrial F1 complex, delta
*ATP5F1 NM_001688
*ATP5G2 NM_005176
*ATP5G3 NM_001689 Homo sapiens ATP synthase, H+ transporting, mitochondrial F0 complex, subunit c
*ATP5H NM_006356 Homo sapiens ATP synthase, H+ transporting, mitochondrial F0 complex, subunit d
*ATP5J NM_001685
*ATP5J2 NM_004889 Homo sapiens ATP synthase, H+ transporting, mitochondrial F0 complex, subunit f,
*ATP5J2-PTCD1 NM_001198879
*ATP5L NM_006476
*ATP5O NM_001697 Homo sapiens ATP synthase, H+ transporting, mitochondrial F1 complex, O subunit
*ATP5S NM_015684
*ATP5SL NM_018035
*ATP6AP1 NM_001183 Homo sapiens ATPase, H+ transporting, lysosomal interacting protein 1 (ATP6IP1),
*ATP6V0A2 NM_012463
*ATP6V0B NM_004047 Homo sapiens ATPase, H+ transporting, lysosomal 21kDa, V0 subunit c (ATP6V0B),
*ATP6V0C NM_001694 Homo sapiens ATPase, H+ transporting, lysosomal 16kDa, V0 subunit c (ATP6V0C),
*ATP6V0D1 NM_004691
*ATP6V0E1 NM_003945
*ATP6V1C1 NM_001695
*ATP6V1D NM_015994
*ATP6V1E1 NM_001696 Homo sapiens ATPase, H+ transporting, lysosomal 31kDa, V1 subunit E isoform 1
*ATP6V1F NM_004231 Homo sapiens ATPase, H+ transporting, lysosomal 14kDa, V1 subunit F (ATP6V1F),
*ATP6V1G1 NM_004888 Homo sapiens ATPase, H+ transporting, lysosomal 13kDa, V1 subunit G isoform 1
*ATP6V1H NM_015941
*ATPAF2 NM_145691
*ATPIF1 NM_016311 | 1 | Biochemistry |
If quantum effects are negligible, an accelerating charged particle radiates power as described by the Larmor formula and its relativistic generalization. | 7 | Physical Chemistry |
The visual cycle is consistent within mammals, and is summarized as follows:
#all-trans-retinyl ester + HO → 11-cis-retinol + fatty acid; RPE65 isomerohydrolases;
#11-cis-retinol + NAD → 11-cis-retinal + NADH + H; 11-cis-retinol dehydrogenases;
#11-cis-retinal + aporhodopsin → rhodopsin + HO; forms Schiff base linkage to lysine, -CH=NH-;
#rhodopsin + hν → metarhodopsin II (i.e., 11-cis photoisomerizes to all-trans):
#:(rhodopsin + hν → photorhodopsin → bathorhodopsin → lumirhodopsin → metarhodopsin I → metarhodopsin II);
#metarhodopsin II + HO → aporhodopsin + all-trans-retinal;
#all-trans-retinal + NADPH + H → all-trans-retinol + NADP; all-trans-retinol dehydrogenases;
#all-trans-retinol + fatty acid → all-trans-retinyl ester + HO; lecithin retinol acyltransferases (LRATs).
Steps 3, 4, 5, and 6 occur in rod cell outer segments; Steps 1, 2, and 7 occur in retinal pigment epithelium (RPE) cells. | 1 | Biochemistry |
Early investigations into low bandgap semiconductors focused on germanium (Ge). Ge has a bandgap of 0.66 eV, allowing for conversion of a much higher fraction of incoming radiation. However, poor performance was observed due to the high effective electron mass of Ge. Compared to III-V semiconductors, Ge's high electron effective mass leads to a high density of states in the conduction band and therefore a high intrinsic carrier concentration. As a result, Ge diodes have fast decaying "dark" current and therefore, a low open-circuit voltage. In addition, surface passivation of germanium has proven difficult. | 7 | Physical Chemistry |
In situ ellipsometry refers to dynamic measurements during the modification process of a sample. This process can be used to study, for instance, the growth of a thin film, including calcium phosphate mineralization at the air-liquid interface, etching or cleaning of a sample. By in situ ellipsometry measurements it is possible to determine fundamental process parameters, such as, growth or etch rates, variation of optical properties with time. In situ ellipsometry measurements require a number of additional considerations: The sample spot is usually not as easily accessible as for ex situ measurements outside the process chamber. Therefore, the mechanical setup has to be adjusted, which can include additional optical elements (mirrors, prisms, or lenses) for redirecting or focusing the light beam. Because the environmental conditions during the process can be harsh, the sensitive optical elements of the ellipsometry setup must be separated from the hot zone. In the simplest case this is done by optical view ports, though strain induced birefringence of the (glass-) windows has to be taken into account or minimized. Furthermore, the samples can be at elevated temperatures, which implies different optical properties compared to samples at room temperature. Despite all these problems, in situ ellipsometry becomes more and more important as process control technique for thin film deposition and modification tools. In situ ellipsometers can be of single-wavelength or spectroscopic type. Spectroscopic in situ ellipsometers use multichannel detectors, for instance CCD detectors, which measure the ellipsometric parameters for all wavelengths in the studied spectral range simultaneously. | 7 | Physical Chemistry |
Sieverts' law, in physical metallurgy and in chemistry, is a rule to predict the solubility of gases in metals. It is named after German chemist Adolf Sieverts (1874–1947). The law states that the solubility of a diatomic gas in metal is proportional to the square root of the partial pressure of the gas in thermodynamic equilibrium. Hydrogen, oxygen and nitrogen are examples of dissolved diatomic gases of frequent interest in metallurgy. | 8 | Metallurgy |
Triparental mating is a form of bacterial conjugation where a conjugative plasmid present in one bacterial strain assists the transfer of a mobilizable plasmid present in a second bacterial strain into a third bacterial strain. Plasmids are introduced into bacteria for such purposes as transformation, cloning, or transposon mutagenesis. Triparental matings can help overcome some of the barriers to efficient plasmid mobilization. For instance, if the conjugative plasmid and the mobilizable plasmid are members of the same incompatibility group they do not need to stably coexist in the second bacterial strain for the mobilizable plasmid to be transferred. | 1 | Biochemistry |
For patients who have achieved long term remission, it is recommended to discontinue lithium gradually and in a controlled fashion.
Discontinuation symptoms may occur in patients stopping the medication including irritability, restlessness and somatic symptoms like vertigo, dizziness or lightheadedness. Symptoms occur within the first week and are generally mild and self-limiting within weeks. | 1 | Biochemistry |
Rickets, a childhood disease, is characterized by impeded growth and soft, weak, deformed long bones that bend and bow under their weight as children start to walk. Rickets typically appears between 3 and 18 months of age. Cases continue to be reported in North American and other Western Countries and is primarily seen in breastfed infants and those with darker skin complexions. This condition is characterized by bow legs, which can be caused by calcium or phosphorus deficiency, as well as a lack of vitamin D; in the 21st century, it is largely found in low-income countries in Africa, Asia, or the Middle East and in those with genetic disorders such as pseudo-vitamin-D-deficiency rickets.
Maternal vitamin D deficiency may cause overt bone disease from before birth and impairment of bone quality after birth. Nutritional rickets exists in countries with intense year-round sunlight such as Nigeria and can occur without vitamin D deficiency.
Although rickets and osteomalacia are now rare in the United Kingdom, outbreaks have happened in some immigrant communities in which people with osteomalacia included women with seemingly adequate daylight outdoor exposure wearing Western clothing. Having darker skin and reduced exposure to sunshine did not produce rickets unless the diet deviated from a Western omnivore pattern characterized by high intakes of meat, fish, and eggs. The dietary risk factors for rickets include abstaining from animal foods.
Vitamin D deficiency remains the main cause of rickets among young infants in most countries because breast milk is low in vitamin D and social customs and climatic conditions can prevent adequate sun exposure. In sunny countries such as Nigeria, South Africa, and Bangladesh, where rickets occurs among older toddlers and children, it has been attributed to low dietary calcium intakes, which are characteristic of cereal-based diets with limited access to dairy products.
Rickets was formerly a major public health problem among the US population. In Denver, almost two-thirds of 500 children had mild rickets in the late 1920s. An increase in the proportion of animal protein in the 20th century American diet coupled with increased consumption of milk fortified with relatively small quantities of vitamin D coincided with a dramatic decline in the number of rickets cases. Also, in the United States and Canada, vitamin D-fortified milk, infant vitamin supplements, and vitamin supplements have helped to eradicate the majority of cases of rickets for children with fat malabsorption conditions. | 1 | Biochemistry |
In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. Nam et al. demonstrated the direct condensation of purine and pyrimidine nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Also, a plausible prebiotic process for synthesizing purine ribonucleosides was presented by Becker et al. | 1 | Biochemistry |
Filtrate is the waste that has been discharge in vacuum ceramic filters through the waste stream. During cake washing, a wash liquid is sprayed on the cake solids to remove impurities or additional filtrate. The filtrate goes into filtrate tank and is drained through a discharge system. However, the filtrate is recyclable and has low suspended solid content. Thus, it can be recycled through the system without further treatment. Filtrate is used to flush the disc during back flow washing to clean the micro-porous structure and remove any residual cake. | 3 | Analytical Chemistry |
2DPs as two dimensional sheet macromolecules have a crystal lattice, that is they consist of monomer units that repeat in two dimensions. Therefore, a clear diffraction pattern from their crystal lattice should be observed as a proof of crystallinity. The internal periodicity is supported by electron microscopy imaging, electron diffraction and Raman-spectroscopic analysis.
2DPs should in principle also be obtainable by, e.g., an interfacial approach whereby proving the internal structure, however, is more challenging and has not yet been achieved.
In 2014 a 2DP was reported synthesised from a trifunctional photoreactive anthracene derived monomer, preorganised in a lamellar crystal and photopolymerised in a [4+4]cycloaddition. Another reported 2DP also involved an anthracene-derived monomer | 7 | Physical Chemistry |
Klein-Seetharaman moved to the University of Pittsburgh as an assistant professor in 2002 and was promoted to associate professor in 2009. She joined the Warwick Medical School as a professor in medicine in 2013. She returned to the[United States in 2017, first as a professor at the Colorado School of Mines and then as a professor at the Arizona State University in 2021. Her research looks to uncover the structure-property relationships of membrane proteins. | 1 | Biochemistry |
On the surface of cells, there are many proteins. Some proteins are involved in recognition, attachment, or transportation. The citrate-malate shuttle system consists of citrate shuttle and malate shuttle, which are carrier proteins. Carrier proteins are present on the cell surface. They transport different molecules across the mitochondria. In this system, the substances being transported are malate and citrate.
The starting material is acetyl-CoA. It is a molecule that is involved in ATP synthesis, protein metabolism, and lipid metabolism. As the inner membrane is not permeable to this molecule, acetyl-CoA needs to be converted into other products for effective transport. It is also the first step of the reaction. | 1 | Biochemistry |
After completing his PhD, he became an assistant and lecturer at Technical University of Munich (1965–1968). From 1968 to 1973, he was Professor and Director at Technical University of Hannover; then, he became a professor at Institute for Physical Chemistry, Ludwig Maximilian University of Munich (1973–1986). During the 1970s and 80s, he was also a visiting professor at the California Institute of Technology (1976–1977), the University of Wisconsin–Milwaukee (1979) and the University of California, Berkeley (1981–82).
He became the director at the Fritz Haber Institute of the MPG from 1986 till his retirement in 2004. In 1986, as honors, he was named "Honorary Professor" at the Free University of Berlin and at the Technical University of Berlin, and in 1996 at the Humboldt University of Berlin.
From 2008 to 2016, Ertl served as a member of the university council of Technische Universität Darmstadt. | 7 | Physical Chemistry |
The process for TLC is similar to paper chromatography but provides faster runs, better separations, and the choice between different stationary phases. Plates can be labelled before or after the chromatography process with a pencil or other implement that will not interfere with the process.
There are four main stages to running a thin-layer chromatography plate:
Plate preparation: Using a capillary tube, a small amount of a concentrated solution of the sample is deposited near the bottom edge of a TLC plate. The solvent is allowed to completely evaporate before the next step. A vacuum chamber may be necessary for non-volatile solvents. To make sure there is sufficient compound to obtain a visible result, the spotting procedure can be repeated. Depending on the application, multiple different samples may be placed in a row the same distance from the bottom edge; each sample will move up the plate in its own "lane."
Development chamber preparation: The development solvent or solvent mixture is placed into a transparent container (separation/development chamber) to a depth of less than 1 centimetre. A strip of filter paper (aka "wick") is also placed along the container wall. This filter paper should touch the solvent and almost reach the top of the container. The container is covered with a lid and the solvent vapors are allowed to saturate the atmosphere of the container. Failure to do so results in poor separation and non-reproducible results.
Development: The TLC plate is placed in the container such that the sample spot(s) are not submerged into the mobile phase. The container is covered to prevent solvent evaporation. The solvent migrates up the plate by capillary action, meets the sample mixture, and carries it up the plate (elutes the sample). The plate is removed from the container before the solvent reaches the top of the plate; otherwise, the results will be misleading. The solvent front, the highest mark the solvent has travelled along the plate, is marked.
Visualization: The solvent evaporates from the plate. Visualization methods include UV light, staining, and many more. | 3 | Analytical Chemistry |
Worthy of note is that in 2013, a structural prediction of the Au (SCH) cluster, based on Density Functional Theory (DFT) was confirmed in 2015. This result represents the maturity of this field where calculations are able to guide the experimental work.
The following table features some sizes. | 7 | Physical Chemistry |
Shotgun lipidomics is fast, highly sensitive, and it can identify hundreds of lipids missed by other methods — all with a much smaller tissue sample so that specific cells or minute biopsy samples can be examined. | 1 | Biochemistry |
Currently, there are two main types of silencers in DNA, which are the classical silencer element and the non-classical negative regulatory element (NRE). In classical silencers, the gene is actively repressed by the silencer element, mostly by interfering with general transcription factor (GTF) assembly. NREs passively repress the gene, usually by inhibiting other elements that are upstream of the gene. Of the NREs, there are certain silencers that are orientation-dependent meaning that the binding factor binds in a particular direction relative to other sequences. Promoter-dependent silencers are understood to be silencer elements because they are position and orientation-dependent but must also use a promoter-specific factor. There has been a recent discovery of Polycomb-group Response Elements (PREs), which can allow and inhibit repression depending on the protein bound to it, and the presence of non-coding transcription. | 1 | Biochemistry |
Epitaxial wafers of crystalline silicon can be grown on a monocrystalline silicon "seed" wafer by chemical vapor deposition (CVD), and then detached as self-supporting wafers of some standard thickness (e.g., 250 µm) that can be manipulated by hand, and directly substituted for wafer cells cut from monocrystalline silicon ingots. Solar cells made with this "kerfless" technique can have efficiencies approaching those of wafer-cut cells, but at appreciably lower cost if the CVD can be done at atmospheric pressure in a high-throughput inline process. The surface of epitaxial wafers may be textured to enhance light absorption.
In June 2015, it was reported that heterojunction solar cells grown epitaxially on n-type monocrystalline silicon wafers had reached an efficiency of 22.5% over a total cell area of 243.4 cm. | 7 | Physical Chemistry |
The Canadian Headache Society guideline for migraine prophylaxis recommends, based on low-quality evidence, that 300 mg of CoQ be offered as a choice for prophylaxis. | 1 | Biochemistry |
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