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All luciferases are classified as oxidoreductases (), meaning they act on single donors with incorporation of molecular oxygen. Because luciferases are from many diverse protein families that are unrelated, there is no unifying mechanism, as any mechanism depends on the luciferase and luciferin combination. However, all characterised luciferase-luciferin reactions to date have been shown to require molecular oxygen at some stage. | 1 | Applied and Interdisciplinary Chemistry |
The amino radical has two characteristic electronic states:
The more stable electronic state is B, where the unpaired electron is in the p-orbital perpendicular to the plane of the molecule (π type radical). The high energy electronic state, A, has the two electrons in the p-orbital and the unpaired electron in the sp orbital (σ type radical).
Nitrogen centered compounds, such as amines, are nucleophilic in nature. This character is also seen in amino radicals, which can be considered to be nucleophilic species. | 0 | Theoretical and Fundamental Chemistry |
An aminopolycarboxylic acid (sometimes abbreviated APCA) is a chemical compound containing one or more nitrogen atoms connected through carbon atoms to two or more carboxyl groups. Aminopolycarboxylates that have lost acidic protons form strong complexes with metal ions. This property makes aminopolycarboxylic acids useful complexone in a wide variety of chemical, medical, and environmental applications. | 0 | Theoretical and Fundamental Chemistry |
Square antiprisms can be capped on both square faces, giving bicapped square antiprismatic molecular geometry. The bicapped square antiprismatic atoms surrounding a central atom define the vertices of a gyroelongated square bipyramid. The symmetry group of this object is D.
Examples:
*BH, defined by the B framework
*[AsRh(CO)] and [SRh(CO)], defined by the Rh framework, which encapsulates the main group atoms As and S
*[TlSn], a zintl ion | 0 | Theoretical and Fundamental Chemistry |
Perilipin-null mice eat more food than wild-type mice, but gain 1/3 less fat than wild-type mice on the same diet; perilipin-null mice are thinner, with more lean muscle mass. Perilipin-null mice also exhibit enhanced leptin production and a greater tendency to develop insulin resistance than wild-type mice. Even though perilipin-null mice present less fat mass and a higher insulin resistance, they do not show signs of a whole lipodystrophic phenotype.
In humans, studies suggest that a deficiency of PLIN1 causes lipodystrophic syndromes, which disables the optimal accumulation of triglycerides in adipocytes that derives in an abnormal deposition of lipids in tissues such as skeletal muscle and liver. The storage of lipids in the liver leads to insulin resistance and hypertriglyceridemia. Affected patients are characterized by a subcutaneous fat with smaller than normal adipocytes, macrophage infiltration and fibrosis.
These findings affirm a new primary form of inherited lipodystrophy and emphasize on the severe metabolic consequences of a defect in the formation of lipid droplets in adipose tissue.
In particular, variants 13041A>G and 14995A>T have been associated with increased risk of obesity in women and 11482G>A has been associated with decreased perilipin expression and increased lipolysis in women. | 1 | Applied and Interdisciplinary Chemistry |
CA 242 is a tumor marker for sialylated Lewis carbohydrates associated with adenocarcinomas and e-selectin-mediated metastatic risk. It is commonly tested along with CEA, CA19-9, and CA242 for detecting pancreatic cancer. The specificity of CA 242 is higher than similar markers. Current research dictates that diagnostic efficiency is highest when various tumor markers are tested for at once.
CA 242 has been used clinically as a diagnostic biomarker for pancreatic, colorectal and other cancers. Since CA 242 is overexpressed in malignant tumors, it is within reason to assume that CA 242 could be a product of cancer cells. A study was conducted where CA 242 serum levels were acquired from 34, 680 patients with 27 clinically defined diseases. The data acquired shows that patients with pancreatic cancer, cervical cancer and lymphoma had the highest levels of the CA 242 serum, which was followed by esophageal, colon and ovarian cancer. CA 242 can be shown to detect other types of cancer as shown. | 1 | Applied and Interdisciplinary Chemistry |
Membrane ruffling is a characteristic feature of many actively migrating cells. When the membrane is unable to attach to the substrate, the membrane protrusion is recycled back into the cell. The ruffling of membranes is thought to be controlled by a group of enzymes known as Rho GTPases, specifically RhoA, Rac1 and cdc42. | 1 | Applied and Interdisciplinary Chemistry |
*Honorary Member, Chinese Chemical Society (1962)
*Foreign Member, Royal Swedish Academy of Sciences (1972)
*Honorary Member, Japan Pharmaceutical Association) (1973)
*Honorary Member, Chemical Society of Japan (1977)
*Honorary Member, Japan Society for Bioscience, Biotechnology, and Agrochemistry (1977)
*Honorary Member, Swiss Chemical Society (1977)
*Member, Japan Academy (1977)
*Honorary Member, Society of Synthetic Organic Chemistry of Japan (1990) | 0 | Theoretical and Fundamental Chemistry |
Near the extinction of the diffusion flame, is order unity. The equation has no solution for , where is the extinction Damköhler number. For with , the equation possess two solutions, of which one is an unstable solution. Unique solution exist if and . The solution is unique for , where is the ignition Damköhler number.
Liñán also gave a correlation formula for the extinction Damköhler number, which is increasingly accurate for , | 1 | Applied and Interdisciplinary Chemistry |
The mechanism of action of armodafinil is unknown. Armodafinil (R-(−)-modafinil) has pharmacological properties almost identical to those of modafinil (a mixture of R-(−)- and (S)-(+)-modafinil). The (R)- and (S)-enantiomers have similar pharmacological action in animals. Armodafinil has wake-promoting actions similar to sympathomimetic agents including amphetamine and methylphenidate, although its pharmacologic profile is not identical to that of the sympathomimetic amines. Armodafinil is an indirect dopamine receptor agonist; it binds in vitro to the dopamine transporter (DAT) and inhibits dopamine reuptake. For modafinil, this activity has been associated in vivo with increased extracellular dopamine levels. In genetically engineered mice lacking the dopamine transporter, modafinil lacked wake-promoting activity, suggesting that this activity was DAT-dependent. However, the wake-promoting effects of modafinil, unlike those of amphetamine, were not antagonized by the dopamine receptor antagonist haloperidol in rats. In addition, alpha-methyl-p-tyrosine, an inhibitor of dopamine synthesis, blocks the action of amphetamine but does not block locomotor activity induced by modafinil.
In addition to its wake-promoting effects and ability to increase locomotor activity in animals, according to Nuvigil prescribing information from manufacturer Cephalon, armodafinil produces psychoactive and euphoric effects, alterations in mood, perception, thinking, and feelings typical of other central nervous system (CNS) stimulants in humans. Armodafinil, like racemic modafinil, may also possess reinforcing properties, as evidenced by its self-administration in monkeys previously trained to administer cocaine; armodafinil was also partially discriminated as stimulant-like. A Cephalon-founded study in which patients were administered modafinil, methylphenidate, and a placebo found that modafinil produces "psychoactive and euphoric effects and feelings consistent with [methylphenidate]." | 0 | Theoretical and Fundamental Chemistry |
Phycochromes are a subclass of phycobiliprotein that was initially recognised only as light sensory pigments in cyanobacteria. They are now deemed to constitute of all possible photoreversibly photochromic pigments, regardless of function. They are also found in red algae. In a series of journal articles written by G.S. and L.O. Björn, it was reported that phycochromes a, b, c and d were discovered by scientists who fractionated samples of blue-green algae using electrofocusing. The fractions with isoelectric points at or around 4.6 seemed analogous to phytochromes in that they possessed photochromic properties, yet were sensitive to light of shorter wavelengths. All four phycochromes except phycochrome c were extracted from the blue-green algae Tolypothrix distorta; whereas phycochrome a was also found in Phormidium luridum, Nostoc muscorum 1453/12 and Anacystis nidulans; and phycochrome c was extracted from Nostoc muscorum A and Tolypothrix tenuis. | 1 | Applied and Interdisciplinary Chemistry |
There are several quality control techniques used to ensure the quality of extracted DNA, including:
* Spectrophotometry: This is a widely used method for measuring the concentration and purity of a DNA sample. Spectrophotometry measures the absorbance of a sample at different wavelengths, typically at 260 nm and 280 nm. The ratio of absorbance at 260 nm and 280 nm is used to determine the purity of the DNA sample.
* Gel electrophoresis: This technique is used to visualize and compare the size and integrity of DNA samples. The DNA is loaded onto an agarose gel and then subjected to an electric field, which causes the DNA to migrate through the gel. The migration of the DNA can be visualized using ethidium bromide, which intercalates into the DNA and fluoresces under UV light.
* Fluorometry: Fluorometry is a method to determine the concentration of nucleic acids by measuring the fluorescence of the sample when excited by a specific wavelength of light. Fluorometry uses dyes that specifically bind to nucleic acids and have a high fluorescence intensity.
* PCR: Polymerase Chain Reaction (PCR) is a technique that amplifies a specific region of DNA, it is also used as a QC method by amplifying a small fragment of the DNA, if the amplification is successful, it means the extracted DNA is of good quality and it's not degraded.
* Qubit Fluorometer: The Qubit Fluorometer is an instrument that uses fluorescent dyes to measure the concentration of DNA and RNA in a sample. It is a quick and sensitive method that can be used to determine the concentration of DNA samples.
* Bioanalyzer: The bioanalyzer is an instrument that uses electrophoresis to separate and analyze DNA, RNA, and protein samples. It can provide detailed information about the size, integrity, and purity of a DNA sample. | 1 | Applied and Interdisciplinary Chemistry |
Edith Ellen Humphrey (11 September 1875 – 25 February 1978) was a British inorganic chemist who carried out pioneering work in co-ordination chemistry at the University of Zurich under Alfred Werner. She is thought to be the first British woman to obtain a doctorate in chemistry and the first chemist to synthesize a chiral inorganic complex.
On the occasion of the 150th anniversary of the Royal Society of Chemistry (RSC), 8 April 1991, a sample of the original crystals synthesised by Humphrey for her PhD were sent to them by the Swiss Committee of Chemistry, together with a modern CD spectrum of a solution of one crystal. This box of crystals remains on display in the exhibition room of the RSC. | 0 | Theoretical and Fundamental Chemistry |
Organic matter soil amendments have been known by farmers to be beneficial to plant growth for longer than recorded history. However, the chemistry and function of the organic matter have been a subject of controversy since humans began postulating about it in the 18th century. Until the time of Liebig, it was supposed that humus was used directly by plants, but, after Liebig showed that plant growth depends upon inorganic compounds, many soil scientists held the view that organic matter was useful for fertility only as it was broken down with the release of its constituent nutrient elements into inorganic forms.
At the present time, soil scientists hold a more holistic view and at least recognize that humus influences soil fertility through its effect on the water-holding capacity of the soil. Also, since plants have been shown to absorb and translocate the complex organic molecules of systemic insecticides, they can no longer discredit the idea that plants may be able to absorb the soluble forms of humus; this may in fact be an essential process for the uptake of otherwise insoluble iron oxides.
A study on the effects of humic acid on plant growth was conducted at Ohio State University which said in part "humic acids increased plant growth" and that there were "relatively large responses at low application rates".
A 1998 study by scientists at the North Carolina State University College of Agriculture and Life Sciences showed that addition of humate to soil significantly increased root mass in creeping bentgrass turf.
A 2018 study by scientists at the University of Alberta showed that humic acids can reduce prion infectivity in laboratory experiments, but that this effect may be uncertain in the environment due to minerals in the soil that buffer the effect. | 0 | Theoretical and Fundamental Chemistry |
Ortho lithiation followed by methylation with methyl iodide is a convenient method for the synthesis of starting materials for lateral lithiations. Elaboration of the benzylic carbon through lateral lithiation and treatment with an electrophile provides a powerful synthetic alternative to direct electrophilic aromatic substitution (EAS). Although yields over the entire sequence are moderate, site selectivity is generally higher than analogous EAS reactions. | 0 | Theoretical and Fundamental Chemistry |
Many general purpose vectors such as pUC19 usually include a system for detecting the presence of a cloned DNA fragment, based on the loss of an easily scored phenotype. The most widely used is the gene coding for E. coli β-galactosidase, whose activity can easily be detected by the ability of the enzyme it encodes to hydrolyze the soluble, colourless substrate X-gal (5-bromo-4-chloro-3-indolyl-beta-d-galactoside) into an insoluble, blue product (5,5-dibromo-4,4-dichloro indigo). Cloning a fragment of DNA within the vector-based lacZα sequence of the β-galactosidase prevents the production of an active enzyme. If X-gal is included in the selective agar plates, transformant colonies are generally blue in the case of a vector with no inserted DNA and white in the case of a vector containing a fragment of cloned DNA. | 1 | Applied and Interdisciplinary Chemistry |
The main disadvantage of glass ionomer sealants or cements has been inadequate retention or simply lack of strength, toughness, and
limited wear resistance. For instance, due to its poor retention rate, periodic recalls are necessary, even after 6 months, to eventually replace the lost sealant. Different methods have been used to address the physical shortcomings of the glass ionomer cements such as thermo-light curing (polymerization), or addition of the zirconia, hydroxyapatite, N-vinyl pyrrolidone, N-vinyl caprolactam, and fluoroapatite to reinforce the glass ionomer cements. | 0 | Theoretical and Fundamental Chemistry |
Europe has very few sources of tin. Therefore, throughout ancient times it was imported long distances from the known tin mining districts of antiquity. These were the Ore Mountains (Erzgebirge) along the modern border between Germany and the Czech Republic, the Iberian Peninsula, Brittany in modern France, and Cornwall and Devon in southwestern Britain.) There are several smaller sources of tin in the Balkans and another minor source of tin is known to exist at Monte Valerio in Tuscany, Italy. The Tuscan source was exploited by Etruscan miners around 800 BC, but it was not a significant source of tin for the rest of the Mediterranean. Even at that time, the Etruscans themselves had to import additional tin from the northwest of the Iberian Peninsula, and later from Cornwall.
It has been claimed that tin was first mined in Europe around 2500 BC in the Erzgebirge, and knowledge of tin bronze and tin extraction techniques spread from there to Brittany and Cornwall around 2000 BC and from northwestern Europe to northwestern Spain and Portugal around the same time. However, the only Bronze Age object from Central Europe whose tin has been scientifically provenanced is the Nebra sky disk, and its tin (and gold, though not its copper), is shown by tin isotopes to have come from Cornwall. In addition, a rare find of a pure tin ingot in Scandinavia was provenanced to Cornwall. Available evidence, though very limited, thus points to Cornwall as the sole early source of tin in Central and Northern Europe.
Cornwall and Devon were important sources of tin for Europe and the Mediterranean throughout ancient times and may have been the earliest sources of tin in Western Europe, with evidence for trade to the Eastern Mediterranean by the Late Bronze Age. Within recorded history, Cornwall and Devon only dominated the European market for tin from late Roman times, starting around the 3rd century AD, as many Spanish tin mines were exhausted. Cornwall maintained its importance as a source of tin throughout medieval times and into the modern period.
Brittany – opposite Cornwall on the Celtic Sea – has significant sources of tin which show evidence of being extensively exploited after the Roman conquest of Gaul during the 50s BC and onwards. Brittany remained a significant source of tin throughout the medieval period.
A group of 52 bronze artifacts from the late Bronze Age Balkans has been shown to have tin of multiple origins, based on the correlation of tin isotope differences with the different find locations of the artifacts. While the locations of these separate tin sources are uncertain, the larger Serbian group of artifacts is inferred to be derived from tin sources in western Serbia (e.g. Mount Cer), while the smaller group, largely from western Romania, is inferred to have western Romanian origins.
Iberian tin was widely traded across the Mediterranean during the Bronze Age, and extensively exploited during Roman times. But Iberian tin deposits were largely forgotten throughout the medieval period, were not rediscovered until the 18th century, and only re-gained importance during the mid-19th century. | 1 | Applied and Interdisciplinary Chemistry |
Coactivators are promising targets for drug therapies in the treatment of cancer, metabolic disorder, cardiovascular disease and type 2 diabetes, along with many other disorders. For example, the steroid receptor coactivator (SCR) NCOA3 is often overexpressed in breast cancer, so the development of an inhibitor molecule that targets this coactivator and decreases its expression could be used as a potential treatment for breast cancer.
Because transcription factors control many different biological processes, they are ideal targets for drug therapy. The coactivators that regulate them can be easily replaced with a synthetic ligand that allows for control over an increase or decrease in gene expression.
Further technological advances will provide new insights into the function and regulation of coactivators at a whole-organism level and elucidate their role in human disease, which will hopefully provide better targets for future drug therapies. | 1 | Applied and Interdisciplinary Chemistry |
The SELDI process is a combination of surface-enhanced neat desorption (SEND),surface-enhanced affinity-capture (SEAC), and surface-enhanced photolabile attachment and release (SEPAR) mass spectrometry. With SEND, analytes can be desorbed and ionized without adding a matrix; the matrix is incorporated into the sample surface. In SEAC, the sample surface is modified to bind the analyte of interest for analysis with laser desorption/ionization mass spectrometry (LDI-MS). SEPAR is a combination of SEND and SEAC; the modified sample surface also acts as an energy absorbing matrix for ionization. | 1 | Applied and Interdisciplinary Chemistry |
Johan Gadolin was born in Åbo (Finnish name Turku), Finland (then a part of Sweden). Johan was the son of Jakob Gadolin, professor of physics and theology at Åbo. Johan began to study mathematics at the Royal Academy of Turku (Åbo Kungliga Akademi) when he was fifteen. Later he changed his major to chemistry, studying with Pehr Adrian Gadd, the first chair of chemistry at Åbo.
In 1779 Gadolin moved to Uppsala University. In 1781, he published his dissertation Dissertatio chemica de analysi ferri ("Chemical dissertation on the analysis of iron"), under the direction of Torbern Bergman. Bergman founded an important research school, and many of his students, including Gadolin, Johan Gottlieb Gahn, and Carl Wilhelm Scheele, became close friends. | 1 | Applied and Interdisciplinary Chemistry |
The overall reaction is
: 4 Fe – cytochrome c + 4 H + O → 4 Fe – cytochrome c + 2 HO ΔG = - 218 kJ/mol, E = +565 mV
Two electrons are passed from two cytochrome cs, through the Cu and cytochrome a sites to the cytochrome a–Cu binuclear center, reducing the metals to the Fe form and Cu. The hydroxide ligand is protonated and lost as water, creating a void between the metals that is filled by O. The oxygen is rapidly reduced, with two electrons coming from the Fe-cytochrome a, which is converted to the ferryl oxo form (Fe=O). The oxygen atom close to Cu picks up one electron from Cu, and a second electron and a proton from the hydroxyl of Tyr(244), which becomes a tyrosyl radical. The second oxygen is converted to a hydroxide ion by picking up two electrons and a proton. A third electron from another cytochrome c is passed through the first two electron carriers to the cytochrome a–Cu binuclear center, and this electron and two protons convert the tyrosyl radical back to Tyr, and the hydroxide bound to Cu to a water molecule. The fourth electron from another cytochrome c flows through Cu and cytochrome a to the cytochrome a–Cu binuclear center, reducing the Fe=O to Fe, with the oxygen atom picking up a proton simultaneously, regenerating this oxygen as a hydroxide ion coordinated in the middle of the cytochrome a–Cu center as it was at the start of this cycle. Overall, four reduced cytochrome cs are oxidized while O and four protons are reduced to two water molecules. | 1 | Applied and Interdisciplinary Chemistry |
In general, electronegativity increases on passing from left to right along a period and decreases on descending a group. Hence, fluorine is the most electronegative of the elements (not counting noble gases), whereas caesium is the least electronegative, at least of those elements for which substantial data is available. This would lead one to believe that caesium fluoride is the compound whose bonding features the most ionic character.
There are some exceptions to this general rule. Gallium and germanium have higher electronegativities than aluminium and silicon, respectively, because of the d-block contraction. Elements of the fourth period immediately after the first row of the transition metals have unusually small atomic radii because the 3d-electrons are not effective at shielding the increased nuclear charge, and smaller atomic size correlates with higher electronegativity (see Allred-Rochow electronegativity and Sanderson electronegativity above). The anomalously high electronegativity of lead, in particular when compared to thallium and bismuth, is an artifact of electronegativity varying with oxidation state: its electronegativity conforms better to trends if it is quoted for the +2 state with a Pauling value of 1.87 instead of the +4 state. | 0 | Theoretical and Fundamental Chemistry |
Sources:
The choice of the dividing surface, strictly speaking, is arbitrary, however, it is very desirable to take into account the type of external potential . Otherwise, these expressions are at odds with the generally accepted concepts and common sense.
First, must lie close to the transition layer (i.e., the region where the number density varies), otherwise it would mean the attribution of the bulk properties of one of the phase to the surface.
Second. In the case of weak adsorption, for example, when the potential is close to the stepwise, it is logical to choose close to . (In some cases, choosing , where is particle radius, excluding the "dead" volume.)
In the case of pronounced adsorption it is advisable to choose close to the right border of the transition region. In this case all particles from the transition layer will be attributed to the solid, and is always positive. Trying to put in this case will lead to a strong shift of to the solid body domain, which is clearly unphysical.
Conversely, if (fluid on the left), it is advisable to choose lying on the left side of the transition layer. In this case the surface particles once again refer to the solid and is back positive.
Thus, except in the case of static membrane, we can always avoid the "negative adsorption" for one-component systems. | 0 | Theoretical and Fundamental Chemistry |
An inverted repeat sequence with no intervening nucleotides between the initial sequence and its downstream reverse complement is a palindrome. <br /> EXAMPLE:<br />
Step 1: start with an inverted repeat: <br />
Step 2: remove intervening nucleotides: <br />
This resulting sequence is palindromic because it is the reverse complement of itself.
::: test sequence (from Step 2 with intervening nucleotides removed)
::: complement of test sequence
::: reverse complement This is the same as the test sequence above, and thus, it is a palindrome. | 1 | Applied and Interdisciplinary Chemistry |
The old MIL-F-14256 and QQ-S-571 standards defined fluxes as:
*R (rosin)
*RMA (rosin mildly activated)
*RA (rosin activated)
*WS (water-soluble)
Any of these categories may be no-clean, or not, depending on the chemistry selected and the standard that the manufacturer requires. | 1 | Applied and Interdisciplinary Chemistry |
In dual-mode, the mobile and stationary phases are reversed part way through the separation experiment. This requires changing the phase being pumped through the column as well as the direction of flow. Dual-mode operation is likely to elute the entire sample from the column but the order of elution is disrupted by switching the phase and direction of flow. | 0 | Theoretical and Fundamental Chemistry |
A euthanaticum is used for euthanasia and physician-assisted suicide. Euthanasia is not permitted by law in many countries, and consequently, medicines will not be licensed for this use in those countries. | 1 | Applied and Interdisciplinary Chemistry |
The Toxicity/Residue Database is maintained by the U.S. EPA and is a database for the prediction of toxicity of organic and inorganic chemicals to aquatic organisms. This data base was developed by the EPA Duluth office and became operational in 1999. The data base is derived from more than 500 peer-reviewed references and is a collection of their findings on roughly 200 chemicals and 190 species both marine and fresh water. Data regarding organism response endpoints or effects are measured as the concentration of chemical in the tissue of the test organism at the time which effects such as lethality, metabolic depression, or increased respiration occur. More than 3,000 effects may be queried from a small piece of downloaded software to gather survival, growth or reproductive endpoint effect data. | 1 | Applied and Interdisciplinary Chemistry |
The examination process is normally conducted by hydrologists and hydrologic technicians, and involves a review of historical engineering information about the bridge, followed by a visual inspection. Information is recorded about the type of rock or sediment carried by the river, and the angle at which the river flows toward and away from the bridge. The area under the bridge is also inspected for holes and other evidence of scour.
Bridge examination begins by office investigation. The history of the bridge and any previous scour related problems should be noted. Once a bridge is recognized as a potential scour bridge, it will proceed to further evaluation including field review, scour vulnerability analysis and prioritizing. Bridges will also be rated in different categories and prioritized for scour risk. Once a bridge is evaluated as scour critical, the bridge owner should prepare a scour plan of action to mitigate the known and potential deficiencies. The plan may include installation of countermeasures, monitoring, inspections after flood events, and procedures for closing bridges if necessary.
Alternatively, sensing technologies are also being put in place for scour assessment. The scour-sensing level can be classified into three levels: general bridge inspection, collecting limited data and collecting detailed data. There are three different types of scour-monitoring systems: fixed, portable and geophysical positioning. Each system can help to detect scour damage in an effort to avoid bridge failure, thus increasing public safety. | 1 | Applied and Interdisciplinary Chemistry |
Cellulose is a polyol and thus susceptible to acetylation, which is achieved using acetic anhydride. Acetylation disrupts hydrogen bonding, which otherwise dominates the properties of cellulose. Consequently, the cellulose esters are soluble in organic solvents and can be cast into fibers and films. | 0 | Theoretical and Fundamental Chemistry |
The four most common modes of radioactive decay are: alpha decay, beta decay, inverse beta decay (considered as both positron emission and electron capture), and isomeric transition. Of these decay processes, only alpha decay (fission of a helium-4 nucleus) changes the atomic mass number (A) of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same residue mod 4. This divides the list of nuclides into four classes. All the members of any possible decay chain must be drawn entirely from one of these classes.
Three main decay chains (or families) are observed in nature. These are commonly called the thorium series, the radium or uranium series, and the actinium series, representing three of these four classes, and ending in three different, stable isotopes of lead. The mass number of every isotope in these chains can be represented as A = 4n, A = 4n + 2, and A = 4n + 3, respectively. The long-lived starting isotopes of these three isotopes, respectively thorium-232, uranium-238, and uranium-235, have existed since the formation of the Earth, ignoring the artificial isotopes and their decays created since the 1940s.
Due to the relatively short half-life of its starting isotope neptunium-237 (2.14 million years), the fourth chain, the neptunium series with A = 4n + 1, is already extinct in nature, except for the final rate-limiting step, decay of bismuth-209. Traces of Np and its decay products do occur in nature, however, as a result of neutron capture in uranium ore. The ending isotope of this chain is now known to be thallium-205. Some older sources give the final isotope as bismuth-209, but in 2003 it was discovered that it is very slightly radioactive, with a half-life of .
There are also non-transuranic decay chains of unstable isotopes of light elements, for example those of magnesium-28 and chlorine-39. On Earth, most of the starting isotopes of these chains before 1945 were generated by cosmic radiation. Since 1945, the testing and use of nuclear weapons has also released numerous radioactive fission products. Almost all such isotopes decay by either β or β decay modes, changing from one element to another without changing atomic mass. These later daughter products, being closer to stability, generally have longer half-lives until they finally decay into stability. | 0 | Theoretical and Fundamental Chemistry |
The first transformation of metabolism of ZEN will reduce the ketone group to an alcohol via aliphatic hydroxylation and result in the formation of the two zearalenol metabolites. This process is catalyzed by 3 α- and 3 β-hydroxy steroid dehydrogenase (HSD). CYP450 enzymes will then catalyze aromatic hydroxylation at the 13 or 15 position resulting in 13- or 15- catechols. Steric hindrance of at the 13 position is suspected to be the reason that in humans and rats there is more of the 15-catechol present. The catechols are the processed into mono-ethyl esters by catechol-o-methyl transferase (COMT) and S-adenosyl methionine (SAM). After this transformation they may be metabolized further to quinones which can cause the formation of reactive oxygen species (ROS) and cause covalent modification of DNA. | 1 | Applied and Interdisciplinary Chemistry |
The technique was invented in 1955 by Grant Henry Lathe and Colin R Ruthven, working at Queen Charlotte's Hospital, London. They later received the John Scott Award for this invention. While Lathe and Ruthven used starch gels as the matrix, Jerker Porath and Per Flodin later introduced dextran gels; other gels with size fractionation properties include agarose and polyacrylamide. A short review of these developments has appeared.
There were also attempts to fractionate synthetic high polymers; however, it was not until 1964, when J. C. Moore of the Dow Chemical Company published his work on the preparation of gel permeation chromatography (GPC) columns based on cross-linked polystyrene with controlled pore size, that a rapid increase of research activity in this field began. It was recognized almost immediately that with proper calibration, GPC was capable to provide molar mass and molar mass distribution information for synthetic polymers. Because the latter information was difficult to obtain by other methods, GPC came rapidly into extensive use. | 1 | Applied and Interdisciplinary Chemistry |
For a system of diameter and volume , at constant temperature , the classical canonical partition function
with a scaled coordinate, the free energy is given by:
Combining the above equation with the definition of chemical potential,
we get the chemical potential of a sufficiently large system from (and the fact that the smallest allowed change in the particle number is )
wherein the chemical potential of an ideal gas can be evaluated analytically.
Now let's focus on since the potential energy of an system can be separated into the potential energy of an system and the potential of the excess particle interacting with the system, that is,
and
Thus far we converted the excess chemical potential into an ensemble average, and the integral in the above equation can be sampled by the brute force Monte Carlo method.
The calculating of excess chemical potential is not limited to homogeneous systems, but has also been extended to inhomogeneous systems by the Widom insertion method, or other ensembles such as NPT and NVE. | 0 | Theoretical and Fundamental Chemistry |
Carboxypeptidases are usually classified into one of several families based on their active site mechanism.
* Enzymes that use a metal in the active site are called "metallo-carboxypeptidases" (EC number 3.4.17).
* Other carboxypeptidases that use active site serine residues are called "serine carboxypeptidases" (EC number 3.4.16).
* Those that use an active site cysteine are called "cysteine carboxypeptidase" (or "thiol carboxypeptidases")(EC number 3.4.18).
These names do not refer to the selectivity of the amino acid that is cleaved. | 1 | Applied and Interdisciplinary Chemistry |
The term human equivalent is used in a number of different contexts. This term can refer to human equivalents of various comparisons of animate and inanimate things. | 1 | Applied and Interdisciplinary Chemistry |
In the field of molecular biology, the ETS (E26 transformation-specific or E-twenty-six. (Erythroblast Transformation Specific)) family is one of the largest families of transcription factors and is unique to animals. There are 29 genes in humans, 28 in the mouse, 10 in Caenorhabditis elegans and 9 in Drosophila. The founding member of this family was identified as a gene transduced by the leukemia virus, E26. The members of the family have been implicated in the development of different tissues as well as cancer progression. | 1 | Applied and Interdisciplinary Chemistry |
A hydrophilic molecule or portion of a molecule is one whose interactions with water and other polar substances are more thermodynamically favorable than their interactions with oil or other hydrophobic solvents. They are typically charge-polarized and capable of hydrogen bonding. This makes these molecules soluble not only in water but also in other polar solvents.
Hydrophilic molecules (and portions of molecules) can be contrasted with hydrophobic molecules (and portions of molecules). In some cases, both hydrophilic and hydrophobic properties occur in a single molecule. An example of these amphiphilic molecules is the lipids that comprise the cell membrane. Another example is soap, which has a hydrophilic head and a hydrophobic tail, allowing it to dissolve in both water and oil.
Hydrophilic and hydrophobic molecules are also known as polar molecules and nonpolar molecules, respectively. Some hydrophilic substances do not dissolve. This type of mixture is called a colloid.
An approximate rule of thumb for hydrophilicity of organic compounds is that solubility of a molecule in water is more than 1 mass % if there is at least one neutral hydrophile group per 5 carbons, or at least one electrically charged hydrophile group per 7 carbons.
Hydrophilic substances (ex: salts) can seem to attract water out of the air. Sugar is also hydrophilic, and like salt is sometimes used to draw water out of foods. Sugar sprinkled on cut fruit will "draw out the water" through hydrophilia, making the fruit mushy and wet, as in a common strawberry compote recipe. | 0 | Theoretical and Fundamental Chemistry |
Fluids display properties such as:
* lack of resistance to permanent deformation, resisting only relative rates of deformation in a dissipative, frictional manner, and
* the ability to flow (also described as the ability to take on the shape of the container).
These properties are typically a function of their inability to support a shear stress in static equilibrium. By contrast, solids respond to shear either with a spring-like restoring force—meaning that deformations are reversible—or they require a certain initial stress before they deform (see plasticity).
Solids respond with restoring forces to both shear stresses and to normal stresses, both compressive and tensile. By contrast, ideal fluids only respond with restoring forces to normal stresses, called pressure: fluids can be subjected both to compressive stress—corresponding to positive pressure—and to tensile stress, corresponding to negative pressure. Solids and liquids both have tensile strengths, which when exceeded in solids createsirreversible deformation and fracture, and in liquids cause the onset of cavitation.
Both solids and liquids have free surfaces, which cost some amount of free energy to form. In the case of solids, the amount of free energy to form a given unit of surface area is called surface energy, whereas for liquids the same quantity is called surface tension. In response to surface tension, the ability of liquids to flow results in behaviour differing from that of solids, though at equilibrium both tend to minimise their surface energy: liquids tend to form rounded droplets, whereas pure solids tend to form crystals. Gases, lacking free surfaces, freely diffuse. | 1 | Applied and Interdisciplinary Chemistry |
Drug repurposing is considered a rapid, cost-effective, and reduced-risk strategy for the development of new treatment options also for psychiatric disorders. | 1 | Applied and Interdisciplinary Chemistry |
Ridges (regions of increased gene expression) are domains of the genome with a high gene expression; the opposite of ridges are antiridges. The term was first used by Caron et al. in 2001. Characteristics of ridges are:
*Gene dense
*Contain many C and G nucleobases
*Genes have short introns
*High SINE repeat density
*Low LINE repeat density | 1 | Applied and Interdisciplinary Chemistry |
Most IPNs do not interpenetrate completely on a molecular scale, but rather form small dispersed or bicontinuous phase morphologies with characteristic length scales on the order of tens of nanometers. However, since these length scales are relatively small, they are often considered homogeneous on a macroscopic scale. The characteristic lengths associated with these domains often scale with the length of chains between crosslinks, and thus the morphology of the phases is often dictated by the crosslinking density of the constituent networks. The kinetics of phase separation in IPNs can arise from both nucleation and growth and spinodal decomposition mechanisms, with the former producing discrete phases akin to dispersed spheres and the latter forming bicontinuous phases akin to interconnected cylinders. Contrary to many typical phase separation processes, coarsening, where the length scale of the phases tends to increase over time, can be impeded by the formation of crosslinks in either network. Furthermore, IPNs are often able to maintain these complex morphologies over long periods of time compared to what could be achieved by simple polymer blends. | 0 | Theoretical and Fundamental Chemistry |
The L-A dsRNA virus of the yeast Saccharomyces cerevisiae has a single 4.6 kb genomic segment that encodes its major coat protein, Gag (76 kDa) and a Gag-Pol fusion protein (180 kDa) formed by a -1 ribosomal frameshift. L-A can support the replication and encapsidation in separate viral particles of any of several satellite dsRNAs, called M dsRNAs, each of which encodes a secreted protein toxin (the killer toxin) and immunity to that toxin. L-A and M are transmitted from cell to cell by the cytoplasmic mixing that occurs in the process of mating. Neither is naturally released from the cell or enters cells by other mechanisms, but the high frequency of yeast mating in nature results in the wide distribution of these viruses in natural isolates. Moreover, the structural and functional similarities with dsRNA viruses of mammals has made it useful to consider these entities as viruses. | 1 | Applied and Interdisciplinary Chemistry |
Melt spinning is a metal forming technique that is typically used to form thin ribbons of metal or alloys with a particular atomic structure.
Some important commercial applications of melt-spun metals include high-efficiency transformers (Amorphous metal transformer), sensory devices, telecommunications equipment, and power electronics.
A typical melt spinning process involves casting molten metal by jetting it onto a rotating wheel or drum, which is cooled internally, usually by water or liquid nitrogen. The molten material rapidly solidifies upon contact with the large, cold surface area of the drum. The rotation of the drum constantly removes the solidified product while exposing new surface area to the molten metal stream, allowing for continuous production. The resulting ribbon is then directed along the production line to be packaged or machined into further products.
The cooling rates achievable by melt spinning are on the order of 10–10 Kelvins per second (K/s). Consequently, melt spinning is used to develop materials that require extremely high cooling rates in order to form, such as metallic glasses. Due to their rapid cooling, these products have a highly disordered atomic structure which gives them unique magnetic and physical properties (see amorphous metals).
Several variations to the melt spinning process provide specific advantages. These processes include planar flow casting, twin roll melt spinning, and auto ejection melt spinning.
Originating with Robert Pond in a series of related patents from 1958 to 1961 (US Patent Nos. 2825108, 2910744, and 2976590), the current concept of the melt spinner was outlined by Pond and Maddin in 1969. At first, the liquid was quenched on the inner surface of a drum. Liebermann and Graham further developed the process as a continuous casting technique by 1976, this time on the drum's outer surface. The process can continuously produce thin ribbons of material, with sheets several inches in width commercially available. | 1 | Applied and Interdisciplinary Chemistry |
At normal temperatures pumping mechanisms in cell walls retain intracellular potassium at high levels and extrude sodium. If these pumps fail sodium is taken up by the cell and potassium lost. Water follows the sodium passively and results in swelling of the cells. The importance of this control of cell swelling was demonstrated by McLoughlin who found a significant correlation between canine renal cortical water content and the ability of kidneys to support life after 36-hour storage. The pumping mechanism is driven by the enzyme system known as Na+K+- activated ATPase and is inhibited by cold. Levy found that metabolic activity at 10 °C, as indicated by oxygen consumption measurements, was reduced to about 5% of normal and, because all enzyme systems are affected in a similar way by hypothermia, ATPase activity is markedly reduced at 10 °C.
There are, however, tissue and species differences in the cold sensitivity of this ATPase which may account for the differences in the ability of tissues to withstand hypothermia. Martin has shown that in dog kidney cortical cells some ATPase activity is still present at 10 °C but not at 0 °C. In liver and heart cells activity was completely inhibited at 10 °C and this difference in the cold sensitivity of ATPase correlated with the greater difficulty in controlling cell swelling during hypothermic storage of liver and heart cells. A distinct ATPase is found in vessel walls, and this was shown by Belzer to be completely inhibited at 10 °C, when at this temperature kidney cortical cells ATPase is still active. These experiments were performed on aortic endothelium, but if the vascular endothelium of the kidney has the same properties, then vascular injury may be the limiting factor in prolonged kidney storage.
Willis has shown how hibernators derive some of their ability to survive low temperatures by having a Na+K+-ATPase which is able to transport sodium and potassium actively across their cell membranes, at 5 °C, about six times faster than in non-hibernators; this transport rate is sufficient to prevent cell swelling.
The rate of cooling of a tissue may also be significant in the production of injury to enzyme systems. Francavilla showed that when liver slices were rapidly cooled (immediate cooling to 12 °C in 6 minutes) anaerobic glycolysis, as measured on rewarming to 37 °C, was inhibited by about 67% of the activity that was demonstrated in slices that had been subjected to delayed cooling. However, dog kidney slices were less severely affected by the rapid cooling than were the liver slices. | 1 | Applied and Interdisciplinary Chemistry |
A process flow diagram (PFD) is a diagram commonly used in chemical and process engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations. Another commonly used term for a PFD is process flowsheet. It is the key document in process design. | 1 | Applied and Interdisciplinary Chemistry |
For binary mixtures, the conversion to molality is
where the solvent is substance 1, and the solute is substance 2.
For solutions with more than one solute, the conversion is | 0 | Theoretical and Fundamental Chemistry |
It is important to distinguish molecularity from order of reaction. The order of reaction is an empirical quantity determined by experiment from the rate law of the reaction. It is the sum of the exponents in the rate law equation. Molecularity, on the other hand, is deduced from the mechanism of an elementary reaction, and is used only in context of an elementary reaction. It is the number of molecules taking part in this reaction.
This difference can be illustrated on the reaction between nitric oxide and hydrogen:
where the observed rate law is , so that the reaction is third order. Since the order does not equal the sum of reactant stoichiometric coefficients, the reaction must involve more than one step. The proposed two-step mechanism has a rate-limiting first step whose molecularity corresponds to the overall order of 3:
Slow:
Fast:
On the other hand, the molecularity of this reaction is undefined, because it involves a mechanism of more than one step. However, we can consider the molecularity of the individual elementary reactions that make up this mechanism: the first step is trimolecular because it involves three reactant molecules, while the second step is bimolecular because it involves two reactant molecules. | 0 | Theoretical and Fundamental Chemistry |
Kinetic isotope effect (KIE) is a measurement of the reaction rate of isotope-labeled reactants against the more common natural substrate. Kinetic isotope effect values are a ratio of the turnover number and include all steps of the reaction. Intrinsic kinetic isotope values stem from the difference in the bond vibrational environment of an atom in the reactants at ground state to the environment of the atom's transition state. Through the kinetic isotope effect much insight can be gained as to what the transition state looks like of an enzyme-catalyzed reaction and guide the development of transition state analogs. | 1 | Applied and Interdisciplinary Chemistry |
Fluoroestradiol F-18, also known as [F]16α-fluoroestradiol and sold under the brand name Cerianna, is a radioactive diagnostic agent indicated for use with positron emission tomography (PET) imaging. It is an analog of estrogen and is used to detect estrogen receptor-positive breast cancer lesions. | 1 | Applied and Interdisciplinary Chemistry |
Mummia, mumia, or originally mummy referred to several different preparations in the history of medicine, from "mineral pitch" to "powdered human mummies". It originated from Arabic mūmiyā "a type of resinous bitumen found in Western Asia and used curatively" in traditional Islamic medicine, which was translated as pissasphaltus (from "pitch" and "asphalt") in ancient Greek medicine. In medieval European medicine, mūmiyā "bitumen" was transliterated into Latin as mumia meaning both "a bituminous medicine from Persia" and "mummy". Merchants in apothecaries dispensed expensive mummia bitumen, which was thought to be an effective cure-all for many ailments. It was also used as an aphrodisiac.
Beginning around the 12th century when supplies of imported natural bitumen ran short, mummia was misinterpreted as "mummy", and the word's meaning expanded to "a black resinous exudate scraped out from embalmed Egyptian mummies". This began a period of lucrative trade between Egypt and Europe, and suppliers substituted rare mummia exudate with entire mummies, either embalmed or desiccated. After Egypt banned the shipment of mummia in the 16th century, unscrupulous European apothecaries began to sell fraudulent mummia prepared by embalming and desiccating fresh corpses.
During the Renaissance, scholars proved that translating bituminous mummia as mummy was a mistake, and physicians stopped prescribing the ineffective drug. Artists in the 17–19th centuries still used ground up mummies to tint a popular oil-paint called mummy brown. | 1 | Applied and Interdisciplinary Chemistry |
The bromine cycle is a biogeochemical cycle of bromine through the atmosphere, biosphere, and hydrosphere. | 0 | Theoretical and Fundamental Chemistry |
The first models which tried to explain the clustering of genes were, of course, focused on operons because they were discovered before eukaryote gene clusters were. In 1999 Lawrence proposed a model for the origin operons. This selfish operon model suggests that individual genes were grouped together by vertical en horizontal transfer and were preserved as a single unit because that was beneficial for the genes, not per se for the organism. This model predicts that the gene clusters must have conserved between species. This is not the case for many operons and gene clusters seen in eukaryotes.
According to Eichler and Sankoff the two mean processes in eukaryotic chromosome evolution are 1) rearrangements of chromosomal segments and 2) localized duplication of genes. Clustering could be explained by reasoning that all genes in a cluster are originated from tandem duplicates of a common ancestor. If all co-expressed genes in a cluster were evolved from a common ancestral gene it would have been expected that theyre co-expressed because they all have comparable promoters. However, gene clustering is a very common tread in genomes and it isnt clear how this duplication model could explain all of the clustering. Furthermore, many genes that are present in clusters are not homologous.
How did evolutionary non-related genes come in close proximity in the first place? Either there is a force that brings functionally related genes near to each other, or the genes came near by change. Singer et al. proposed that genes came in close proximity by random recombination of genome segments. When functionally related genes came in close proximity to each other, this proximity was conserved. They determined all possible recombination sites between genes of human and mouse. After that, they compared the clustering of the mouse and human genome and looked if recombination had occurred at the potentially recombination sites. It turned out that recombination between genes of the same cluster was very rare. So, as soon as a functional cluster is formed recombination is suppressed by the cell. On sex chromosomes, the amount of clusters is very low in both human and mouse. The authors reasoned this was due to the low rate of chromosomal rearrangements of sex chromosomes.
Open chromatin regions are active regions. It is more likely that genes will be transferred to these regions. Genes from organelle and virus genome are inserted more often in these regions. In this way non-homologous genes can be pressed together in a small domain.
It is possible that some regions in the genome are better suited for important genes. It is important for the cell that genes that are responsible for basal functions are protected from recombination. It has been observed in yeast and worms that essential genes tend to cluster in regions with a small replication rate.
It is possible that genes came in close proximity by change. Other models have been proposed but none of them can explain all observed phenomena. It's clear that as soon as clusters are formed they are conserved by natural selection. However, a precise model of how genes came in close proximity is still lacking.
The bulk of the present clusters must have formed relatively recent because only seven clusters of functionally related genes are conserved between phyla. Some of these differences can be explained by the fact that gene expression is very differently regulated by different phyla. For example, in vertebrates and plants DNA methylation is used, whereas it is absent in yeast and flies. | 1 | Applied and Interdisciplinary Chemistry |
Nonsense-mediated mRNA decay (NMD) is a surveillance pathway that exists in all eukaryotes. Its main function is to reduce errors in gene expression by eliminating mRNA transcripts that contain premature stop codons. Translation of these aberrant mRNAs could, in some cases, lead to deleterious gain-of-function or dominant-negative activity of the resulting proteins.
NMD was first described in human cells and in yeast almost simultaneously in 1979. This suggested broad phylogenetic conservation and an important biological role of this intriguing mechanism. NMD was discovered when it was realized that cells often contain unexpectedly low concentrations of mRNAs that are transcribed from alleles carrying nonsense mutations. Nonsense mutations code for a premature stop codon which causes the protein to be shortened. The truncated protein may or may not be functional, depending on the severity of what is not translated. In human genetics, NMD has the possibility to not only limit the translation of abnormal proteins, but it can occasionally cause detrimental effects in specific genetic mutations.
NMD functions to regulate numerous biological functions in a diverse range of cells, including the synaptic plasticity of neurons which may shape adult behavior. | 1 | Applied and Interdisciplinary Chemistry |
Post-translational modification of histones either by acetylation or crotonylation is important for the active transcription of genes. Histone crotonylation is regulated by the concentration of crotonyl-coA which can change based on environmental cell conditions or genetic factors. | 1 | Applied and Interdisciplinary Chemistry |
Toluene derivatives with heteroatom-containing substituents in the ortho position undergo site-selective benzylic lithiation in the presence of organolithium compounds (either alkyllithiums or lithium dialkylamides). Coordination of the Lewis acidic lithium atom to the Lewis basic heteroatom, as well as inductive effects derived from the electronegativity of the heteroatom, encourage selective deprotonation at the benzylic position. Competitive ring metalation (directed ortho-metalation) is an important side reaction, but a judicious choice of base often allows for selective benzylic metalation. Useful heteroatom-containing directing groups include dialkylamines, amides (secondary or tertiary), ketone enolates, carbamates, and sulfonates. Lateral lithiation of alkyl-substituted heterocycles incorporating heteroatom-containing substituents is also possible, although ring lithiation α to the ring heteroatom may compete with lateral lithiation. The products of lateral lithiation react with a variety of electrophiles, including reactive alkyl halides (allylic, benzylic, and primary), carbonyl compounds, silyl and stannyl chlorides, disulfides and diselenides, and others. A general, highly selective method for benzylic metalation using a mixed lithium and potassium metal amide (LiNK chemistry) has been developed which permits metalation regardless of the relative position (ortho, meta or para) of the methyl group to the heteroatom containing substituent | 0 | Theoretical and Fundamental Chemistry |
The OFM probes are perfused with a physiological solution (the perfusate) which equilibrates with the ISF of the surrounding tissue. Operating flow rates range from 0.1 to 10 μL/min. OFM allows unrestricted exchange of compounds via an open structure across the open exchange area of the probe. This exchange of compounds between the probe’s perfusate and the surrounding ISF is driven by convection and diffusion, and occurs non-selectively in either direction (Figure 1).
The direct liquid pathway between the probe’s perfusate and the surrounding fluid results in collection of ISF samples. These samples can be collected frequently and are then subjected to bioanalytical analysis to enable monitoring of substance concentrations with temporal resolution during the whole sampling period.
The concentric OFM probe (Figure 2) works according to the same principle. The perfusate is pumped to the tip of the OFM probe through the inner, thin lumen and exits beyond the Open Exchange Area, where it then mixes with exogenous substances present in the ISF before being withdrawn through the outer, thick lumen. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen bonds can vary in strength from weak (1–2 kJ/mol) to strong (161.5 kJ/mol in the bifluoride ion, ). Typical enthalpies in vapor include:
* (161.5 kJ/mol or 38.6 kcal/mol), illustrated uniquely by
* (29 kJ/mol or 6.9 kcal/mol), illustrated water-ammonia
* (21 kJ/mol or 5.0 kcal/mol), illustrated water-water, alcohol-alcohol
* (13 kJ/mol or 3.1 kcal/mol), illustrated by ammonia-ammonia
* (8 kJ/mol or 1.9 kcal/mol), illustrated water-amide
* (18 kJ/mol or 4.3 kcal/mol)
The strength of intermolecular hydrogen bonds is most often evaluated by measurements of equilibria between molecules containing donor and/or acceptor units, most often in solution. The strength of intramolecular hydrogen bonds can be studied with equilibria between conformers with and without hydrogen bonds. The most important method for the identification of hydrogen bonds also in complicated molecules is crystallography, sometimes also NMR-spectroscopy. Structural details, in particular distances between donor and acceptor which are smaller than the sum of the van der Waals radii can be taken as indication of the hydrogen bond strength. One scheme gives the following somewhat arbitrary classification: those that are 15 to 40 kcal/mol, 5 to 15 kcal/mol, and >0 to 5 kcal/mol are considered strong, moderate, and weak, respectively.
Hydrogen bonds involving C-H bonds are both very rare and weak. | 0 | Theoretical and Fundamental Chemistry |
The hydrophilic–lipophilic balance (HLB) of a surfactant is a measure of its degree of hydrophilicity or lipophilicity, determined by calculating percentages of molecular weights for the hydrophilic and lipophilic portions of the surfactant molecule, as described by Griffin in 1949 and 1954. Other methods have been suggested, notably in 1957 by Davies. | 0 | Theoretical and Fundamental Chemistry |
Alba, a green-fluorescent rabbit, was created by a French laboratory commissioned by Eduardo Kac using GFP for purposes of art and social commentary. The US company Yorktown Technologies markets to aquarium shops green fluorescent zebrafish (GloFish) that were initially developed to detect pollution in waterways. NeonPets, a US-based company has marketed green fluorescent mice to the pet industry as NeonMice. Green fluorescent pigs, known as Noels, were bred by a group of researchers led by Wu Shinn-Chih at the Department of Animal Science and Technology at National Taiwan University. A Japanese-American Team created green-fluorescent cats as proof of concept to use them potentially as model organisms for diseases, particularly HIV. In 2009 a South Korean team from Seoul National University bred the first transgenic beagles with fibroblast cells from sea anemones. The dogs give off a red fluorescent light, and they are meant to allow scientists to study the genes that cause human diseases like narcolepsy and blindness. | 1 | Applied and Interdisciplinary Chemistry |
Spectral karyotyping is an image of colored chromosomes. Spectral karyotyping involves FISH using multiple forms of many types of probes with the result to see each chromosome labeled through its metaphase stage. This type of karyotyping is used specifically when seeking out chromosome arrangements. | 1 | Applied and Interdisciplinary Chemistry |
(p)ppGpp, guanosine pentaphosphate and tetraphosphate, also known as the "magic spot" nucleotides, are alarmones involved in the stringent response in bacteria that cause the inhibition of RNA synthesis when there is a shortage of amino acids. This inhibition by (p)ppGpp decreases translation in the cell, conserving amino acids present. Furthermore, ppGpp and pppGpp cause the up-regulation of many other genes involved in stress response such as the genes for amino acid uptake (from surrounding media) and biosynthesis. | 1 | Applied and Interdisciplinary Chemistry |
In the 1950s, Viktor Glukhovsky developed concrete materials originally known under the names "soil silicate concretes" and "soil cements", but since the introduction of the geopolymer concept by Joseph Davidovits, the terminology and definitions of the word geopolymer have become more diverse and often conflicting. The word geopolymer is sometimes used to refer to naturally occurring organic macromolecules; that sense of the word differs from the now-more-common use of this terminology to discuss inorganic materials which can have either cement-like or ceramic-like character.
In the following presentation, a geopolymer is essentially a mineral chemical compound or mixture of compounds consisting of repeating units, for example silico-oxide (-Si-O-Si-O-), silico-aluminate (-Si-O-Al-O-), ferro-silico-aluminate (-Fe-O-Si-O-Al-O-) or alumino-phosphate (-Al-O-P-O-), created through a process of geopolymerization. This method of describing mineral synthesis (geosynthesis) was first presented by Davidovits at an IUPAC symposium in 1976.
Even within the context of inorganic materials, there exist various definitions of the word geopolymer, which can include (or not) a relatively wide variety of low-temperature synthesized solid materials. The most typical geopolymer is generally described as resulting from the reaction between metakaolin (calcined kaolinitic clay) and a solution of sodium or potassium silicate (waterglass). The chemical reaction of geopolymerization tends to result in a highly-connected, disordered network of tetrahedral oxide units - which are silicate and aluminate tetrahedra in the metakaolin-waterglass example mentioned above - and with the net negative charges that are associated with aluminate tetrahedra being balanced by the sodium or potassium ions.
In the simplest form, an example chemical formula for a geopolymer can be written as NaO·AlO·nSiO·wHO, where n is usually between 2 and 4, and w is around 11-15. Geopolymers can be formulated with a wide variety of substitutions in both the framework (Si,Al) and non-framework (Na) sites; most commonly K or Ca take on the non-framework (Na) sites, or Fe or P can in principle replace some of the Al or Si.
Geopolymerization usually occurs at ambient or slightly elevated temperature; the solid aluminosilicate raw materials (e.g. metakaolin) dissolve into the alkaline solution, and then cross-link and polymerize into a growing gel phase, which then continues to set, harden and gain strength. | 0 | Theoretical and Fundamental Chemistry |
The time frame in question when dealing with radioactive waste ranges from 10,000 to 1,000,000 years, according to studies based on the effect of estimated radiation doses. Researchers suggest that forecasts of health detriment for such periods should be examined critically. Practical studies only consider up to 100 years as far as effective planning and cost evaluations are concerned. Long term behavior of radioactive wastes remains a subject for ongoing research projects in geoforecasting. | 0 | Theoretical and Fundamental Chemistry |
Trofimenko's initial work in the field was with the homoscorpionates where three pyrazolyl groups are attached to a boron. Since this work a range of ligands have been reported where more than one type of metal binding group is attached to the central atom; these are the heteroscorpionates.
Many other chemists continue to explore the possibilities of scorpionate ligand alternatives, such as:
*utilizing pyrrole, imidazole, or indole compounds in place of the pyrazole rings²;
*the possibility of tripodal heptadentate ligands such as NO from the ligand tris[6-((2-N,N-diethylcarbamoyl)pyridyl)methyl]amine³;
*Sulfur donor groups such as those found in the Tm ligand or oxygen donor groups.
*changing the ligands to alter the type of molecular encapsulation needed to metals;
*for very different applications, "heteroscorpionate ligands" have been examined of hybrid scorpionate/cyclopentadienyl-lithium compounds such as [Li(2,2-bis(3,5-dimethylpyrazol-1-yl)1,1-diphenylethylcyclopentadienyl(THF)] which catalyzes olefin polymerization. | 0 | Theoretical and Fundamental Chemistry |
Prelog wanted to work in an academic environment, so he accepted the position of lecturer at the University of Zagreb in 1935. At the Technical Faculty in Zagreb, he lectured on organic chemistry and chemical engineering.
With the help of collaborators and students, Prelog started researching quinine and its related compounds. He was financially supported by the pharmaceutical factory "Kaštel", currently Pliva. He developed a financially successful method of producing Streptazol, one of the first commercial sulfonamides. In 1941, while at Zagreb, Prelog developed the first synthesis of adamantane, a hydrocarbon with an unusual structure that was isolated from Moravian oil fields. | 0 | Theoretical and Fundamental Chemistry |
The proton pump, H/K ATPase is a α,β-heterodimeric enzyme. The catalytic α subunit has ten transmembrane segments with a cluster of intramembranal carboxylic amino acids located in the middle of the transmembrane segments TM4, TM5, TM6 and TM8. The β subunit has one transmembrane segment with N terminus in cytoplasmic region. The extracellular domain of the β subunit contains six or seven N-linked glycosylation sites which is important for the enzyme assembly, maturation and sorting. | 1 | Applied and Interdisciplinary Chemistry |
Wong-Ng was a research associate and lecturer in the chemistry department at University of Toronto. From 1981 to 1985, she was a critical review scientist at the International Centre for Diffraction Data. Wong-Ng was a research scientist in the chemistry department at University of Maryland, College Park and a research associate in the ceramics division at the National Bureau of Standards from 1985 to 1988. Since 1988, Wong-Ng works as a research chemist in the ceramics division at the National Institute of Standards and Technology. She served as president the Association of NIST Asian Pacific Americans from 2000 to 2003.
Wong-Ng's research interest includes materials for energy applications, thermoelectric standards, metrology, and data, sorbent materials for sustainability, and high throughput combinatorial approach for novel materials discovery and property optimization for energy conversion applications. She also researches crystallography, phase equilibria, and crystal chemistry of energy materials to understand their structure and property relationships. Structural studies involve synchrotron X-ray and neutron diffraction techniques. | 0 | Theoretical and Fundamental Chemistry |
The rhodium-catalyzed hydroboration reaction is thought to be initiated with the dissociation of a triphenylphosphine from the Rh(I) centre. Oxidative addition of the B-H bond of the borane reagent to this 14 e species is then followed by coordination of the alkene to the 16e Rh(III) hydride complex. Subsequent migratory insertion of the alkene into the rhodium-hydride bond can give two regioisomeric alkyl rhodium(III) boride complexes. Reductive elimination of the boronate ester regenerates the catalyst. Catalyst prepared and handled under anaerobic condition reverses the selectivity to favor the secondary boronate ester. What has been debated is the coordination of the alkene. In the dissociative mechanism, proposed by Männig and Nöth, and supported by Evans and Fu the coordination is accompanied by the loss of one triphenylphosphine ligand.
In the associative mechanism (see below), proposed by Burgess et al., the alkene binds trans to the chloride without dissociation of a triphenylphosphine ligand. The mechanism has been studied by computational methods. Dorigo and Schleyer excluded the associative mechanism by an ab initio study on the dissociative mechanism, whereas Musaev and co-workers support the associative mechanism. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, a Tollmien–Schlichting wave (often abbreviated T-S wave) is a streamwise unstable wave which arises in a bounded shear flow (such as boundary layer and channel flow). It is one of the more common methods by which a laminar bounded shear flow transitions to turbulence. The waves are initiated when some disturbance (sound, for example) interacts with leading edge roughness in a process known as receptivity. These waves are slowly amplified as they move downstream until they may eventually grow large enough that nonlinearities take over and the flow transitions to turbulence.
These waves, originally discovered by Ludwig Prandtl, were further studied by two of his former students, Walter Tollmien and Hermann Schlichting after whom the phenomenon is named.
Also, the T-S wave is defined as the most unstable eigen-mode of Orr–Sommerfeld equations. | 1 | Applied and Interdisciplinary Chemistry |
After initial encapsulation the remaining molecules form connections between the individual micelles to form a network within the aqueous media called a hydrogel, creating a diffuse and relatively constant concentration of the encapsulated particle within the gel. The formation of hydrogels is a phenomenon observed in superabsorbent polymers, or "slush powders," in which the polymer, often in the form of a powder, absorbs water, becoming up to 99% liquid and 30-60 times larger in size. | 0 | Theoretical and Fundamental Chemistry |
cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP-dependent protein kinase A (PKA), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of PKA is a tetramer composed of two regulatory and two catalytic subunits. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits of PKA have been identified in humans. The protein encoded by this gene is one of the regulatory subunits. This protein was found to be a tissue-specific extinguisher that down-regulates the expression of seven liver genes in hepatoma x fibroblast hybrids Three alternatively spliced transcript variants encoding the same protein have been observed. | 1 | Applied and Interdisciplinary Chemistry |
Glycolysis is performed by all living organisms and consists of 10 steps. The net reaction for the overall process of glycolysis is:
:Glucose + 2 NAD+ + 2 P + 2 ADP → 2 pyruvate + 2 ATP + 2 NADH + 2 HO
Steps 1 and 3 require the input of energy derived from the hydrolysis of ATP to ADP and P (inorganic phosphate), whereas steps 7 and 10 require the input of ADP, each yielding ATP. The enzymes necessary to break down glucose are found in the cytoplasm, the viscous fluid that fills living cells, where the glycolytic reactions take place. | 1 | Applied and Interdisciplinary Chemistry |
The setup for projection topography (also called "traverse" topography") is essentially identical to section topography, the difference being that both sample and film are now scanned laterally (synchronously) with respect to the narrow incident beam. A projection topograph therefore corresponds to the superposition of many adjacent section topographs, able to investigate not just a restricted portion, but the entire volume of a crystal.
The technique is rather simple and has been in routine use at "Lang cameras" in many research laboratories. | 0 | Theoretical and Fundamental Chemistry |
The integration of Microalgal Bacterial (MaB) flocs into sustainable agricultural practices presents an innovative approach to enhancing the nutritional content of food sources, particularly in terms of omega-3 fatty acids. Omega-3 fatty acids, such as Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA), are essential fats that humans must obtain from their diet. These fats are crucial for brain health, maintaining the health of cell membranes, and supporting cardiovascular health.
MaB-flocs, comprising both microalgae and bacteria, have shown promise in wastewater treatment applications by effectively removing nutrients such as nitrogen and phosphorus. Microalgae, a key component of MaB-flocs, are known for their ability to accumulate high levels of omega-3 fatty acids. This positions MaB-flocs as a potential sustainable source of these essential nutrients. The cultivation of microalgae within MaB-flocs for omega-3 production offers a dual benefit: improving water quality through nutrient removal and providing a source of essential dietary fats.
Current research focuses on optimizing the growth conditions of MaB-flocs to maximize the yield of omega-3 fatty acids. This includes investigating the effects of various environmental parameters, such as light intensity, temperature, and pH, on the fatty acid profile of microalgae within the flocs. Additionally, the feasibility of harvesting omega-3-rich microalgae from MaB-flocs for use in food and feed applications is being explored.
While the direct contribution of MaB-flocs to disease prevention through omega-3 production requires further research, their potential to serve as a sustainable source of these essential nutrients is clear. As the global demand for omega-3 fatty acids continues to rise, MaB-flocs represent a promising avenue for environmentally friendly production of these vital dietary components. | 1 | Applied and Interdisciplinary Chemistry |
At the age of 26, around the time he was elected to the Academy of Sciences, Lavoisier bought a share in the Ferme générale, a tax farming financial company which advanced the estimated tax revenue to the royal government in return for the right to collect the taxes. On behalf of the Ferme générale Lavoisier commissioned the building of a wall around Paris so that customs duties could be collected from those transporting goods into and out of the city. His participation in the collection of its taxes did not help his reputation when the Reign of Terror began in France, as taxes and poor government reform were the primary motivators during the French Revolution.
Lavoisier consolidated his social and economic position when, in 1771 at age 28, he married Marie-Anne Pierrette Paulze, the 13-year-old daughter of a senior member of the Ferme générale. She was to play an important part in Lavoisiers scientific career—notably, she translated English documents for him, including Richard Kirwans Essay on Phlogiston and Joseph Priestleys research. In addition, she assisted him in the laboratory and created many sketches and carved engravings of the laboratory instruments used by Lavoisier and his colleagues for their scientific works. Madame Lavoisier edited and published Antoines memoirs (whether any English translations of those memoirs have survived is unknown as of today) and hosted parties at which eminent scientists discussed ideas and problems related to chemistry.
A portrait of Antoine and Marie-Anne Lavoisier was painted by the famed artist Jacques-Louis David. Completed in 1788 on the eve of the Revolution, the painting was denied a customary public display at the Paris Salon for fear that it might inflame anti-aristocratic passions.
For three years following his entry into the Ferme générale, Lavoisiers scientific activity diminished somewhat, for much of his time was taken up with official Ferme générale' business. He did, however, present one important memoir to the Academy of Sciences during this period, on the supposed conversion of water into earth by evaporation. By a very precise quantitative experiment, Lavoisier showed that the "earthy" sediment produced after long-continued reflux heating of water in a glass vessel was not due to a conversion of the water into earth but rather to the gradual disintegration of the inside of the glass vessel produced by the boiling water. He also attempted to introduce reforms in the French monetary and taxation system to help the peasants. | 1 | Applied and Interdisciplinary Chemistry |
The total energy of the system is where S is entropy, and the are the other extensive parameters of the system (e.g. volume, particle number, etc.). The entropy of the system may likewise be written as a function of the other extensive parameters as . Suppose that X is one of the which varies as a system approaches equilibrium, and that it is the only such parameter which is varying. The principle of maximum entropy may then be stated as:
: and at equilibrium.
The first condition states that entropy is at an extremum, and the second condition states that entropy is at a maximum. Note that for the partial derivatives, all extensive parameters are assumed constant except for the variables contained in the partial derivative, but only U, S, or X are shown. It follows from the properties of an exact differential (see equation 8 in the exact differential article) and from the energy/entropy equation of state that, for a closed system:
It is seen that the energy is at an extremum at equilibrium. By similar but somewhat more lengthy argument it can be shown that
which is greater than zero, showing that the energy is, in fact, at a minimum. | 0 | Theoretical and Fundamental Chemistry |
In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. An RNA-binding repressor binds to the mRNA and prevents translation of the mRNA into protein. This blocking or reducing of expression is called repression. | 1 | Applied and Interdisciplinary Chemistry |
Mitigation of combined sewer overflows include sewer separation, CSO storage, expanding sewage treatment capacity, retention basins, screening and disinfection facilities, reducing stormwater flows, green infrastructure and real-time decision support systems. For example, cities with combined sewer overflows employ one or more engineering approaches to reduce discharges of untreated sewage, including:
* utilizing a green infrastructure approach to improve storm water management capacity throughout the system, and reduce the hydraulic overloading of the treatment plant
* repair and replacement of leaking and malfunctioning equipment
* increasing overall hydraulic capacity of the sewage collection system (often a very expensive option).
The United Kingdom Environment Agency identified unsatisfactory intermittent discharges and issued an Urban Wastewater Treatment Directive requiring action to limit pollution from combined sewer overflows. In 2009, the Canadian Council of Ministers of the Environment adopted a Canada-wide Strategy for the Management of Municipal Wastewater Effluent including national standards to (1) remove floating material from combined sewer overflows, (2) prevent combined sewer overflows during dry weather, and (3) prevent development or redevelopment from increasing the frequency of combined sewer overflows.
Rehabilitation of combined sewer systems to mitigate CSOs require extensive monitoring networks which are becoming more prevalent with decreasing sensor and communication costs. These monitoring networks can identify bottlenecks causing the main CSO problem, or aid in the calibration of hydrodynamic or hydrological models to enable cost effective CSO mitigation.
Municipalities in the US have been undertaking projects to mitigate CSO since the 1990s. For example, prior to 1990, the quantity of untreated combined sewage discharged annually to lakes, rivers, and streams in southeast Michigan was estimated at more than per year. In 2005, with nearly $1 billion of a planned $2.4 billion CSO investment put into operation, untreated discharges have been reduced by more than per year. This investment that has yielded an 85 percent reduction in CSO has included numerous sewer separation, CSO storage and treatment facilities, and wastewater treatment plant improvements constructed by local and regional governments.
Many other areas in the US are undertaking similar projects (see, for example, in the Puget Sound of Washington). Cities like Pittsburgh, Seattle, Philadelphia, and New York are focusing on these projects partly because they are under federal consent decrees to solve their CSO issues. Both up-front penalties and stipulated penalties are utilized by EPA and state agencies to enforce CSO-mitigating initiatives and the efficiency of their schedules. Municipalities' sewage departments, engineering and design firms, and environmental organizations offer different approaches to potential solutions. | 1 | Applied and Interdisciplinary Chemistry |
Adenylosuccinate is an intermediate in the interconversion of purine nucleotides inosine monophosphate (IMP) and adenosine monophosphate (AMP). The enzyme adenylosuccinate synthase carries out the reaction by the addition of aspartate to IMP and requires the input of energy from a phosphoanhydride bond in the form of guanosine triphosphate (GTP). GTP is used instead of adenosine triphosphate (ATP), so the reaction is not dependent on its products. | 1 | Applied and Interdisciplinary Chemistry |
Pereys archives with materials dating from 1929 to 1975 were left at the University of Strasbourg. They include laboratory notebooks, course materials from her work as professor of nuclear chemistry, papers from her laboratory directorship, and publications. All documents are currently held at the Archives départementales du Bas-Rhin' (Departmental archives of the Bas-Rhin). | 1 | Applied and Interdisciplinary Chemistry |
Unlike a du Noüy ring, no correction factors are required when calculating surface tensions. Due to its small size the rod can be used in high throughput instruments that use a 96-well plate to determine the surface tension. The small diameter of the rod allows its use in a small volume of liquid with 50 l samples being used in some devices.
In addition, the rod also allows use for the Wilhelmy method because the rod is not completely removed during measurements. For this the dynamic surface tension can be used for accurate determination of surface kinetics on a wide range of timescales.
The Padday technique also offers low operator variance and does not need an anti-vibration table. This advantage over other devices allows the Padday devices to be used in the field easily. The rod when made of composite material is also less likely to bend and therefore cheaper than the more costly platinum rod offered in the du Noüy method.
In a typical experiment, the rod is lowered using a manual or automatic device to the surface being analyzed until a meniscus is formed, and then raised so that the bottom edge of the rod lies on the plane of the undisturbed surface. One disadvantage of this technique is that it can not bury the rod into the surface to measure interfacial tension between two liquids. | 0 | Theoretical and Fundamental Chemistry |
Chiral auxiliaries on the alkene partner have been used for stereoselective transformations. In the reaction of camphorsultam-derived unsaturated amides, lower temperatures were needed to achieve high selectivities.
In reactions of silyl-substituted allylic acetates, chiral sulfoxides can be used to enforce high diastereofacial selectivity. | 0 | Theoretical and Fundamental Chemistry |
One well-studied eRNA is the eRNA of the enhancer that interacts with the promoter of the prostate specific antigen (PSA) gene. The PSA eRNA is strongly up-regulated by the androgen receptor. High PSA eRNA then has a domino effect. PSA eRNA binds to and activates the positive transcription elongation factor P-TEFb protein complex which can then phosphorylate RNA polymerase II (RNAP II), initiating its activity in producing mRNA. P-TEFb can also phosphorylate the negative elongation factor NELF (which pauses RNAP II within 60 nucleotides after mRNA initiation begins). Phosphorylated NELF is released from RNAP II, then allowing RNAP II to have productive mRNA progression (see Figure). Up-regulated PSA eRNA thereby increases expression of 586 androgen receptor-responsive genes. Knockdown of PSA eRNA or deleting a set of nucleotides from PSA eRNA causes decreased presence of phosphorylated (active) RNAP II at these genes causing their reduced transcription.
The negative elongation factor NELF protein can also be released from its interaction with RNAP II by direct interaction with some eRNAs. Schaukowitch et al. showed that the eRNAs of two immediate early genes (IEGs) directly interacted with the NELF protein to release NELF from the RNAP II paused at the promoters of these two genes, allowing these two genes to then be expressed.
In addition, eRNAs appear to interact with as many as 30 other proteins. | 1 | Applied and Interdisciplinary Chemistry |
Inverse polymerase chain reaction (Inverse PCR) is a variant of the polymerase chain reaction that is used to amplify DNA with only one known sequence. One limitation of conventional PCR is that it requires primers complementary to both termini of the target DNA, but this method allows PCR to be carried out even if only one sequence is available from which primers may be designed.
Inverse PCR is especially useful for the determination of insert locations. For example, various retroviruses and transposons randomly integrate into genomic DNA. To identify the sites where they have entered, the known, "internal" viral or transposon sequences can be used to design primers that will amplify a small portion of the flanking, "external" genomic DNA. The amplified product can then be sequenced and compared with DNA databases to locate the sequence which has been disrupted.
The inverse PCR method involves a series of restriction digests and ligation, resulting in a looped fragment that can be primed for PCR from a single section of known sequence. Then, like other polymerase chain reaction processes, the DNA is amplified by the thermostable DNA polymerase:
# A target region with an internal section of known sequence and unknown flanking regions is identified
# Genomic DNA is digested into fragments of a few kilobases by a usually low-moderate frequency (6-8 base) cutting restriction enzyme.
# Under low DNA concentrations or quick ligation conditions, self-ligation is induced to give a circular DNA product.
# PCR is carried out as usual with the circular template, with primers complementary to sections of the known internal sequence pointing outwards.
Finally the sequence of the sequenced PCR product is compared against sequence databases.
It is used in case of chromosome crawling. | 1 | Applied and Interdisciplinary Chemistry |
In addition to microarrays, biochips have been designed for two-dimensional electrophoresis, transcriptome analysis, and PCR amplification. Other applications include various electrophoresis and liquid chromatography applications for proteins and DNA, cell separation, in particular, blood cell separation, protein analysis, cell manipulation and analysis including cell viability analysis and microorganism capturing. | 1 | Applied and Interdisciplinary Chemistry |
Bioconversion, also known as biotransformation, is the conversion of organic materials, such as plant or animal waste, into usable products or energy sources by biological processes or agents, such as certain microorganisms. One example is the industrial production of cortisone, which one step is the bioconversion of progesterone to 11-alpha-Hydroxyprogesterone by Rhizopus nigricans. Another example is the bioconversion of glycerol to 1,3-propanediol, which is part of scientific research for many decades.
Another example of bioconversion is the conversion of organic materials, such as plant or animal waste, into usable products or energy sources by biological processes or agents, such as certain microorganisms, some detritivores or enzymes.
In the US, the Bioconversion Science and Technology group performs multidisciplinary R&D for the Department of Energys (DOE) relevant applications of bioprocessing, especially with biomass. Bioprocessing combines the disciplines of chemical engineering, microbiology and biochemistry. The Group s primary role is investigation of the use of microorganism, microbial consortia and microbial enzymes in bioenergy research. New cellulosic ethanol conversion processes have enabled the variety and volume of feedstock that can be bioconverted to expand rapidly. Feedstock now includes materials derived from plant or animal waste such as paper, auto-fluff, tires, fabric, construction materials, municipal solid waste (MSW), sludge, sewage, etc. | 1 | Applied and Interdisciplinary Chemistry |
tert-Butyl hydroperoxide is used for epoxidation and hydroxylation reagents in conjunction with metal catalysts. | 0 | Theoretical and Fundamental Chemistry |
The 1,3-enyne moiety is an important structural unit for biologically active and natural compounds. It can be derived from vinylic systems and terminal acetylenes by using a configuration-retention stereospecific procedure such as the Sonogashira reaction. Vinyl iodides are the most reactive vinyl halides to Pd oxidative addition, and their use is therefore most frequent for Sonogashira cross-coupling reactions due to the usually milder conditions employed. Some examples include:
*The coupling of 2-iodoprop-2-en-1-ol with a wide range of acetylenes.
*The preparation of alk-2-ynylbuta-1,3-dienes from the cross-coupling of a diiodide and phenylacetylene, as shown below. | 0 | Theoretical and Fundamental Chemistry |
A fishs hypoxia tolerance can be represented in different ways. A commonly used representation is the critical O tension (P), which is the lowest water O tension (P consumption rate (M is therefore thought to be more hypoxia-tolerant than a fish with a higher P. But while P is often used to represent hypoxia tolerance, it more accurately represents the ability to take up environmental O at hypoxic P is nevertheless closely tied to a fishs hypoxia tolerance, in part because some fish prioritize their use of aerobic metabolism over anaerobic metabolism and metabolic suppression. It therefore remains a widely used hypoxia tolerance metric.
A fish's hypoxia tolerance can also be represented as the amount of time it can spend at a particular hypoxic P</sub>-of-LOE value therefore imply enhanced hypoxia tolerances. In either case, LOE is a more holistic representation of overall hypoxia tolerance because it incorporates all contributors to hypoxia tolerance, including aerobic metabolism, anaerobic metabolism and metabolic suppression. | 0 | Theoretical and Fundamental Chemistry |
In the built environment, evaporation limited capillary penetration is responsible for the phenomenon of rising damp in concrete and masonry, while in industry and diagnostic medicine this phenomenon is increasingly being harnessed in the field of paper-based microfluidics.
In physiology, capillary action is essential for the drainage of continuously produced tear fluid from the eye. Two canaliculi of tiny diameter are present in the inner corner of the eyelid, also called the lacrimal ducts; their openings can be seen with the naked eye within the lacrymal sacs when the eyelids are everted.
Wicking is the absorption of a liquid by a material in the manner of a candle wick.
Paper towels absorb liquid through capillary action, allowing a fluid to be transferred from a surface to the towel. The small pores of a sponge act as small capillaries, causing it to absorb a large amount of fluid. Some textile fabrics are said to use capillary action to "wick" sweat away from the skin. These are often referred to as wicking fabrics, after the capillary properties of candle and lamp wicks.
Capillary action is observed in thin layer chromatography, in which a solvent moves vertically up a plate via capillary action. In this case the pores are gaps between very small particles.
Capillary action draws ink to the tips of fountain pen nibs from a reservoir or cartridge inside the pen.
With some pairs of materials, such as mercury and glass, the intermolecular forces within the liquid exceed those between the solid and the liquid, so a convex meniscus forms and capillary action works in reverse.
In hydrology, capillary action describes the attraction of water molecules to soil particles. Capillary action is responsible for moving groundwater from wet areas of the soil to dry areas. Differences in soil potential () drive capillary action in soil.
A practical application of capillary action is the capillary action siphon. Instead of utilizing a hollow tube (as in most siphons), this device consists of a length of cord made of a fibrous material (cotton cord or string works well). After saturating the cord with water, one (weighted) end is placed in a reservoir full of water, and the other end placed in a receiving vessel. The reservoir must be higher than the receiving vessel. A related but simplified capillary siphon only consists of two hook-shaped stainless-steel rods, whose surface is hydrophilic, allowing water to wet the narrow grooves between them. Due to capillary action and gravity, water will slowly transfer from the reservoir to the receiving vessel. This simple device can be used to water houseplants when nobody is home. This property is also made use of in the lubrication of steam locomotives: wicks of worsted wool are used to draw oil from reservoirs into delivery pipes leading to the bearings. | 0 | Theoretical and Fundamental Chemistry |
In spectroscopy, a Voigt profile results from the convolution of two broadening mechanisms, one of which alone would produce a Gaussian profile (usually, as a result of the Doppler broadening), and the other would produce a Lorentzian profile. Voigt profiles are common in many branches of spectroscopy and diffraction. Due to the expense of computing the Faddeeva function, the Voigt profile is sometimes approximated using a pseudo-Voigt profile. | 0 | Theoretical and Fundamental Chemistry |
Gerhard Lagaly (born 14 October 1938, in Ludwigshafen am Rhein) is a German chemist and retired university professor. | 0 | Theoretical and Fundamental Chemistry |
Several chemical factors affect the ionophore activity. The activity of an ionophore-metal complex depends on its geometric configuration and the coordinating sites and atoms which create coordination environment surrounding the metal center. This affects the selectivity and affinity towards a certain ion. Ionophores can be selective to a particular ion but may not be exclusive to it. Ionophores facilitate the transport of ions across biological membranes most commonly via passive transport, which is affected by lipophilicity of the ionophore molecule. The increase in lipophilicity of the ionophore-metal complex enhances its permeability through lipophilic membranes. The hydrophobicity and hydrophilicity of the complex also determines whether it will slow down or ease the transport of metal ions into cell compartments. The reduction potential of a metal complex influences its thermodynamic stability and affects its reactivity. The ability of an ionophore to transfer ions is also affected by the temperature. | 0 | Theoretical and Fundamental Chemistry |
Lithium diisopropylamide (commonly abbreviated LDA) is a chemical compound with the molecular formula . It is used as a strong base and has been widely utilized due to its good solubility in non-polar organic solvents and non-nucleophilic nature. It is a colorless solid, but is usually generated and observed only in solution. It was first prepared by Hamell and Levine in 1950 along with several other hindered lithium diorganylamides to effect the deprotonation of esters at the α position without attack of the carbonyl group. | 0 | Theoretical and Fundamental Chemistry |
Coordination cages are used to study guest-guest and host–guest interactions and reactions.
In some instance, planar aromatic molecules stack inside of metalloprisms, as can be observed by UV-visible spectroscopy. Metal-metal interactions can also be observed. Mixed valence species have also been trapped inside of coordination cages. | 0 | Theoretical and Fundamental Chemistry |
Gas phase titrations are titrations done in the gas phase, specifically as methods for determining reactive species by reaction with an excess of some other gas, acting as the titrant. In one common gas phase titration, gaseous ozone is titrated with nitrogen oxide according to the reaction
:O + NO → O + NO.
After the reaction is complete, the remaining titrant and product are quantified (e.g., by Fourier transform spectroscopy) (FT-IR); this is used to determine the amount of analyte in the original sample.
Gas phase titration has several advantages over simple spectrophotometry. First, the measurement does not depend on path length, because the same path length is used for the measurement of both the excess titrant and the product. Second, the measurement does not depend on a linear change in absorbance as a function of analyte concentration as defined by the Beer–Lambert law. Third, it is useful for samples containing species which interfere at wavelengths typically used for the analyte. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, an N-methylamide (NME) is a blocking group for the C-terminus end of peptides. When the carboxyl group of the C-terminus is replaced with a methylamide, further elongation of the peptide chain is prevented. C-Terminal modified peptides are also useful for the modulation of structure-activity relationships and for modifying conformational properties of peptides. N-Methylamides can be prepared directly from solid phase resin-bound peptides. | 1 | Applied and Interdisciplinary Chemistry |
Microbial food cultures are live bacteria, yeasts or moulds used in food production. Microbial food cultures carry out the fermentation process in foodstuffs. Used by humans since the Neolithic period (around 10 000 years BC) fermentation helps to preserve perishable foods and to improve their nutritional and organoleptic qualities (in this case, taste, sight, smell, touch). As of 1995, fermented food represented between one quarter and one third of food consumed in Central Europe. More than 260 different species of microbial food culture are identified and described for their beneficial use in fermented food products globally, showing the importance of their use.
The scientific rationale of the function of microbes in fermentation started to be built with the discoveries of Louis Pasteur in the second half of the 19th century. Extensive scientific study continues to characterize microbial food cultures traditionally used in food fermentation taxonomically, physiologically, biochemically and genetically. This allows better understanding and improvement of traditional food processing and opens up new fields of applications. | 1 | Applied and Interdisciplinary Chemistry |
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