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Low-affinity nerve growth factor receptor has been shown to interact with:
* FSCN1,
* MAGEH1,
* NDN,
* NGFRAP1
* NGF,
* PRKACB,
* TRAF2, and
* TRAF4.
*Nogo-66 receptor
*c-Jun N-terminal kinases
* RhoA
* Rho GDP dissociation inhibitor (RhoGDI)
*NF-kB
*Neurotrophin-3
*Brain-derived neurotrophic factor
*Neurotrophin-4 | 1 | Biochemistry |
Given that DNA and RNA polymerases both carry out template-dependent nucleotide polymerization, it might be expected that the two types of enzymes would be structurally related. However, x-ray crystallographic studies of both types of enzymes reveal that, other than containing a critical Mg ion at the catalytic site, they are virtually unrelated to each other; indeed template-dependent nucleotide polymerizing enzymes seem to have arisen independently twice during the early evolution of cells. One lineage led to the modern DNA polymerases and reverse transcriptases, as well as to a few single-subunit RNA polymerases (ssRNAP) from phages and organelles. The other multi-subunit RNAP lineage formed all of the modern cellular RNA polymerases. | 1 | Biochemistry |
Many inhibitors of glycosyltransferases are known. Some of these are natural products, such as moenomycin, an inhibitor of peptidoglycan glycosyltransferases, the nikkomycins, inhibitors of chitin synthase, and the echinocandins, inhibitors of fungal β-1,3-glucan synthases. Some glycosyltransferase inhibitors are of use as drugs or antibiotics. Moenomycin is used in animal feed as a growth promoter. Caspofungin has been developed from the echinocandins and is in use as an antifungal agent. Ethambutol is an inhibitor of mycobacterial arabinotransferases and is used for the treatment of tuberculosis. Lufenuron is an inhibitor of insect chitin syntheses and is used to control fleas in animals. Imidazolium-based synthetic inhibitors of glycosyltransferases have been designed for use as antimicrobial and antiseptic agents. | 0 | Organic Chemistry |
Raman spectroscopy is one of the easiest methods to integrate into a heterogeneous operando experiment, as these reactions typically occur in the gas phase, so there is very low litter interference and good data can be obtained for the species on the catalytic surface. In order to use Raman, all that is required is to insert a small probe containing two optical fibers for excitation and detection. Pressure and heat complications are essentially negligible, due to the nature of the probe. Operando confocal Raman micro-spectroscopy has been applied to the study of fuel cell catalytic layers with flowing reactant streams and controlled temperature. | 7 | Physical Chemistry |
The processes just above have assumed that the boundaries are also impermeable to particles. Otherwise, we may assume boundaries that are rigid, but are permeable to one or more types of particle. Similar considerations then hold for the chemical potential–particle number conjugate pair, which is concerned with the transfer of energy via this transfer of particles.
* In a constant chemical potential process the system is particle-transfer connected, by a particle-permeable boundary, to a constant-µ reservoir.
* The conjugate here is a constant particle number process. These are the processes outlined just above. There is no energy added or subtracted from the system by particle transfer. The system is particle-transfer-insulated from its environment by a boundary that is impermeable to particles, but permissive of transfers of energy as work or heat. These processes are the ones by which thermodynamic work and heat are defined, and for them, the system is said to be closed. | 7 | Physical Chemistry |
Monomers with aromatic motifs such as bis(merocyanine), oligo(para-phenylenevinylene) (OPV), perylene bisimide (PBI) dye, cyanine dye, corannulene and nano-graphene derivatives have been employed to prepare supramolecular polymers. In some cases, hydrogen bonding side chains appended onto the core aromatic motif help to hold the monomer strongly in the supramolecular polymer. A notable system in this category is a nanotubular supramolecular polymer formed by the supramolecular polymerization of amphiphilic hexa-peri-hexabenzocoronene (HBC) derivatives. Generally, nanotubes are categorized as 1D objects morphologically, however, their walls adopt a 2D geometry and therefore require a different design strategy. HBC amphiphiles in polar solvents solvophobically assemble into a 2D bilayer membrane, which roles up into a helical tape or a nanotubular polymer. Conceptually similar amphiphilic design based on cyanine dye and zinc chlorin dye also polymerize in water resulting in nanotubular supramolecular polymers. | 6 | Supramolecular Chemistry |
The Nernst–Planck equation is applied in describing the ion-exchange kinetics in soils. It has also been applied to membrane electrochemistry. | 7 | Physical Chemistry |
In chemical terms, creatinine is a lactam and an imidazolidinone, so a spontaneously formed cyclic derivative of creatine.
Several tautomers of creatinine exist; ordered by contribution, they are:
*2-Amino-1-methyl-1H-imidazol-4-ol (or 2-amino-1-methylimidazol-4-ol)
*2-Amino-1-methyl-4,5-dihydro-1H-imidazol-4-one
*2-Imino-1-methyl-2,3-dihydro-1H-imidazol-4-ol (or 2-imino-1-methyl-3H-imidazol-4-ol)
*2-Imino-1-methylimidazolidin-4-one
*2-Imino-1-methyl-2,5-dihydro-1H-imidazol-4-ol (or 2-imino-1-methyl-5H-imidazol-4-ol)
Creatinine starts to decompose around 300 °C. | 1 | Biochemistry |
He is also the co-author of three popular books on total synthesis:
#Classics in Total Synthesis I, 1996
#Classics in Total Synthesis II, 2003
#Classics in Total Synthesis III, 2011
Additionally, he authored or co-authored several other books:
#Molecules That Changed the World, 2008
#Handbook of Combinatorial Chemistry: Drugs, Catalysts, Materials, 2002
#Selenium in Natural Products Synthesis, 1984 | 0 | Organic Chemistry |
In 1954, the International Committee for Weights and Measures (CIPM) established the definition of the Kelvin as 1/273.16 of the absolute temperature of the triple point of water. Waters with different isotopic compositions had slightly different triple points. Thus, the International Committee for Weights and Measures specified in 2005 that the definition of the kelvin temperature scale would refer to water with a composition of the nominal specification of VSMOW. The decision was welcomed in 2007 by Resolution 10 of the 23rd CGPM. The triple point is measured in triple-point cells, where the water is held at its triple point and allowed to reach equilibrium with its surroundings. Using ordinary waters, the range of inter-laboratory measurements of the triple point can be about . With VSMOW, the inter-laboratory range of measurements of the triple point is about .
After the 2019 redefinition of the SI base units, the kelvin is defined in terms of the Boltzmann constant, which makes its definition completely independent of the properties of water. The defined value for the Boltzmann constant was selected so that the measured value of the VSMOW triple point is identical to the prior defined value, within measurable accuracy. Triple-point cells remain a practical method of calibrating thermometers. | 9 | Geochemistry |
Sulfide is incorporated into cysteine, catalyzed by O-acetylserine (thiol)lyase, with O-acetylserine as substrate. The synthesis of O-acetylserine is catalyzed by serine acetyltransferase and together with O-acetylserine (thiol)lyase it is associated as enzyme complex named cysteine synthase.
The formation of cysteine is the direct coupling step between sulfur (sulfur metabolism) and nitrogen assimilation in plants. This differs from the process in yeast, where sulfide must be incorporated first in homocysteine then converted in two steps to cysteine.
Cysteine is sulfur donor for the synthesis of methionine, the major other sulfur-containing amino acid present in plants. This happens through the transsulfuration pathway and the methylation of homocysteine.
Both cysteine and methionine are sulfur-containing amino acids and are of great significance in the structure, conformation and function of proteins and enzymes, but high levels of these amino acids may also be present in seed storage proteins. The thiol groups of the cysteine residues in proteins can be oxidized resulting in disulfide bridges with other cysteine side chains (and form cystine) and/or linkage of polypeptides.
Disulfide bridges (disulfide bonds) make an important contribution to the structure of proteins. The thiol groups are also of great importance in substrate binding of enzymes, in metal-sulfur clusters in proteins (e.g. ferredoxins) and in regulatory proteins (e.g. thioredoxins). | 1 | Biochemistry |
A further method to synthesize Grignard reagents involves reaction of Mg with an organozinc compound. This method has been used to make adamantane-based Grignard reagents, which are, due to C-C coupling side reactions, difficult to make by the conventional method from the alkyl halide and Mg. The reductive transmetalation achieves:
:AdZnBr + Mg → AdMgBr + Zn | 0 | Organic Chemistry |
Gold extraction is the extraction of gold from dilute ores using a combination of chemical processes. Gold mining produces about 3600 tons annually, and another 300 tons is produced from recycling.
Since the 20th century, gold has been principally extracted in a cyanide process by leaching the ore with cyanide solution. The gold may then be further refined by gold parting, which removes other metals (principally silver) by blowing chlorine gas through the molten metal. Historically, small particles of gold were amalgamated with mercury, and then concentrated by boiling away the mercury. The mercury method is still used in some small operations. | 8 | Metallurgy |
Pesticide residue refers to the pesticides that may remain on or in food after they are applied to food crops. The maximum residue limits (MRL) of pesticides in food are carefully set by the regulatory authorities to ensure, to their best judgement, no health impacts. Regulations such as pre-harvest intervals also often prevent harvest of crop or livestock products if recently treated in order to allow residue concentrations to decrease over time to safe levels before harvest. Exposure of the general population to these residues most commonly occurs through consumption of treated food sources, or being in close contact to areas treated with pesticides such as farms or lawns.
Persistent pesticides are no longer used for agriculture, and will not be approved by the authorities. Because the half life in soil is long (for DDT 2–15 years) residues can still be detected in humans at levels 5 to 10 times lower than found in the 1970s.
Residues are monitored by the authorities. In 2016, over 99% of samples of US produce had no pesticide residue or had residue levels well below the EPA tolerance levels for each pesticide. | 2 | Environmental Chemistry |
The properties of the polymer are influenced by the chain length. The correct chain length ensures that the encapsulant is not released over time. Avoiding the release of QDs and other toxic particles is critical to prevent unintentional cell necrosis in patients.
The length of the polymer is controlled by two factors:
* Weight of the PEG backbone measured in daltons or kilodaltons (Da or kDa),
* Length of the hydrophobic ends, denoted by the number of carbon atoms in the terminal group (C#).
Increasing the PEG length increases the solubility of the polymer. However, if the PEG chain is too long the micelle will become unstable. It has been observed that a stable hydrogel can only be formed with PEG backbones weighing between six and ten kilodaltons.
On the other hand, increasing the length of the hydrophobic terminal groups decreases aqueous solubility. For a given PEG weight, if the hydrophobe is too short the polymer will just dissolve into the solution, and if it is too long the polymer won't dissolve at all. Generally, two end groups result in the highest conversion into micelles (91%): | 7 | Physical Chemistry |
The Laplace-Perrin distribution law can be rearranged to give the sedimentation length . The sedimentation length describes the probability of finding a colloidal particle at a height above the point of reference . At the length above the reference point, the concentration of colloidal particles decreases by a factor of .
If the sedimentation length is much greater than the diameter of the colloidal particles (), the particles can diffuse a distance greater than this diameter, and the substance remains a suspension. However, if the sedimentation length is less than the diameter (), the particles can only diffuse by a much shorter length. They will sediment under the influence of gravity and settle to the bottom of the container. The substance can no longer be considered a colloidal suspension. It may become a colloidal suspension again if an action to undertaken to suspend the colloidal particles again, such as stirring the colloid. | 1 | Biochemistry |
The disulfide anion is , or S−S. In disulfide, sulfur exists in the reduced state with oxidation number −1. Its electron configuration then resembles that of a chlorine atom. It thus tends to form a covalent bond with another S center to form group, similar to elemental chlorine existing as the diatomic Cl. Oxygen may also behave similarly, e.g. in peroxides such as HO. Examples:
*Hydrogen disulfide (SH), the simplest inorganic disulfide
*Disulfur dichloride (SCl), a distillable liquid.
*Iron disulfide (FeS), or pyrite. | 0 | Organic Chemistry |
Vancomycin is indicated for the treatment of serious, life-threatening infections by Gram-positive (aerobic and/or anaerobic) bacteria unresponsive to other antibiotics.
The increasing emergence of vancomycin-resistant enterococci has resulted in the development of guidelines for use by the Centers for Disease Control Hospital Infection Control Practices Advisory Committee. These guidelines restrict use of vancomycin to these indications:
* treatment of serious infections caused by susceptible organisms resistant to penicillins (methicillin-resistant S. aureus (MRSA) and multidrug-resistant S. epidermidis (MRSE)) or in individuals with serious allergy to penicillins,
* treatment of pseudomembranous colitis caused by C. difficile; in particular, in cases of relapse or where the infection is unresponsive to metronidazole treatment (for this indication, vancomycin is given orally, rather than by its typical intravenous route),
* treatment of infections caused by Gram-positive microorganisms in patients with serious allergies to beta-lactam antimicrobials,
* antibacterial prophylaxis for endocarditis following certain procedures in penicillin-hypersensitive individuals at high risk,
* surgical prophylaxis for major procedures involving implantation of prostheses in institutions with a high rate of MRSA or MRSE,
* early in treatment as an empiric antibiotic for possible MRSA infection while waiting for culture identification of the infecting organism,
* halting the progression of primary sclerosing cholangitis and preventing symptoms; vancomycin does not cure the patient and success is limited,
* treatment of endophthalmitis by intravitreal injection for gram-positive bacteria coverage; it has been used to prevent the condition, however, is not recommended due to the risk of side effects. | 0 | Organic Chemistry |
Fahy was named as a Fellow of the Society for Cryobiology in 2014, and in 2010 he received the Distinguished Scientist Award for Reproductive Biology from the Reproductive Biology Professional Group of the American Society of Reproductive Medicine. He received the Cryopreservation Award from the International Longevity and Cryopreservation Summit held in Madrid, Spain in 2017 in recognition of his career in and dedication to the field of cryobiology. Fahy also received the Grand Prize for Medicine from INPEX in 1995 for his invention of computerized organ cryoprotectant perfusion technology. In 2005, he was recognized as a Fellow of the American Aging Association. | 1 | Biochemistry |
Some [NiFe]-containing proteins are known to sense H and thus regulate transcription.
Copper-containing proteins are known to sense ethylene, which is known to be a hormone relevant to the ripening of fruit. This example illustrates the essential role of organometallic chemistry in nature, as few molecules outside of low-valent transition metal complexes reversibly bind alkenes. Cyclopropenes inhibit ripening by binding to the copper(I) center. Binding to copper is also implicated in the mammalian olfaction of olefins.
Carbon monoxide occurs naturally and is a transcription factor via its complex with a sensor protein based on ferrous porphyrins. | 0 | Organic Chemistry |
Drimane is a bicyclic sesquiterpene. It is the parent structure of many natural products with various biological activity.
Among the notable drimanes are:
*Polygodial, found in several different plants
*Multiple compounds found in several members of the family Canellaceae | 0 | Organic Chemistry |
S-Adenosylmethionine synthetase (), also known as methionine adenosyltransferase (MAT), is an enzyme that creates S-adenosylmethionine (also known as AdoMet, SAM or SAMe) by reacting methionine (a non-polar amino acid) and ATP (the basic currency of energy). | 1 | Biochemistry |
Cold water pitting of copper tube occurs in only a minority of installations. Copper water tubes are usually guaranteed by the manufacturer against manufacturing defects for a period of 50 years. The vast majority of copper systems far exceed this time period but a small minority may fail after a comparatively short time.
The majority of failures seen are the result of poor installation or operation of the water system. The most common failure seen in the last 20 years is pitting corrosion in cold water tubes, also known as Type 1 pitting. These failures are usually the result of poor commissioning practice although a significant number are initiated by flux left in the bore after assembly of soldered joints. Prior to about 1970 the most common cause of Type 1 pitting was carbon films left in the bore by the manufacturing process.
Research and manufacturing improvements in the 1960s virtually eliminated carbon as a cause of pitting with the introduction of a clause in the 1971 edition of BS 2871 requiring tube bores to be free of deleterious films. Despite this, carbon is still regularly blamed for tube failures without proper investigation. | 8 | Metallurgy |
A promoter is defined in RegulonDB as the nucleotide sequence 60 bases upstream and 20 downstream from the precise initiation of transcription or +1. Terminators are regions where transcription ends, and RNA Polymerase unbinds from DNA. | 1 | Biochemistry |
Galactogen is a polysaccharide of galactose that functions as energy storage in pulmonate snails and some Caenogastropoda. This polysaccharide is exclusive of the reproduction and is only found in the albumen gland from the female snail reproductive system and in the perivitelline fluid of eggs. Furthermore, galactogen serves as an energy reserve for developing embryos and hatchlings, which is later replaced by glycogen in juveniles and adults.
Formed by crosslinking polysaccharide-based nanoparticles and functional polymers, galactogens have applications within hydrogel structures. These hydrogel structures can be designed to release particular nanoparticle pharmaceuticals and/or encapsulated therapeutics over time or in response to environmental stimuli.
Galactogens are polysaccharides with binding affinity for bioanalytes. With this, by end-point attaching galactogens to other polysaccharides constituting the surface of medical devices, galactogens have use as a method of capturing bioanalytes (e.g., CTC's), a method for releasing the captured bioanalytes and an analysis method. | 0 | Organic Chemistry |
Microbiota-accessible carbohydrates (MACs) are carbohydrates that are resistant to digestion by a hosts metabolism, and are made available for gut microbes, as prebiotics, to ferment or metabolize into beneficial compounds, such as short chain fatty acids. The term, ‘‘microbiota-accessible carbohydrate’’ contributes to a conceptual framework for investigating and discussing the amount of metabolic activity that a specific food or carbohydrate can contribute to a hosts microbiota.
MACs may come from plants, fungi, animal tissues, or food-borne microbes, and must be metabolized by the microbiome. A significant quantity of the cellulose humans consume is not metabolized by gut microbes and therefore cannot be considered a MAC. The amount of dietary MACs found within a food source will differ for each individual, since which carbohydrates are metabolized depends upon the composition of each person's microbiota. For example, many Japanese individuals possess the genes for the consumption of the algal polysaccharide porphyran in their microbiomes, which are rarely found in North American and European individuals. For individuals who harbor such a porphyran-degrading strain, porphyran would be a MAC. However, porphyran would not be a MAC for those without a microbiota adaptation to seaweed. In similar fashion, germ-free mice without a microbiota might consume a diet with large quantities of potential MACs, but none of the carbohydrates would be considered MACs, since they would escape the digestive tract without being metabolized by microbes.
Lack of dietary MACs results in a microbiota reliant upon endogenous host-derived MACs, such as mucin glycans. Different host genotypes can influence the identity of MACs available to the microbiota in multiple ways. For example, a hosts genes may affect the level of mucus structures, such as the absence of alpha-1-2 fucose residues in the mucus of nonsecretor individuals who lack alpha-1-2- fucosyltransferase activity in the intestine. Similarly, a host may have genes that can determine the efficiency of digestion and absorption of carbohydrates in the small intestine. For example, lactose is accessible to the microbiota in people who are lactose intolerant, and should therefore be considered a MAC for those individuals. For nursing infants, dietary MACs that are naturally found in breast milk are known as human milk oligosaccharides (HMOs). For formula-fed infants, dietary MACs, such as galacto-oligosaccharides, are artificially added to formula. Therefore, the research, discussion and quantification of MACs and their impact on a hosts microbiota may be critical to determining their impact on human health. | 0 | Organic Chemistry |
The subgroup structure suggests another way to compose an arbitrary isometry:
: Pick a fixed point, and a mirror through it.
# If the isometry is odd, use the mirror; otherwise do not.
# If necessary, rotate around the fixed point.
# If necessary, translate.
This works because translations are a normal subgroup of the full group of isometries, with quotient the orthogonal group; and rotations about a fixed point are a normal subgroup of the orthogonal group, with quotient a single reflection. | 3 | Analytical Chemistry |
In 1855, physiologist Adolf Fick first reported his now well-known laws governing the transport of mass through diffusive means. Ficks work was inspired by the earlier experiments of Thomas Graham, which fell short of proposing the fundamental laws for which Fick would become famous. Ficks law is analogous to the relationships discovered at the same epoch by other eminent scientists: Darcys law (hydraulic flow), Ohms law (charge transport), and Fourier's Law (heat transport).
Ficks experiments (modeled on Grahams) dealt with measuring the concentrations and fluxes of salt, diffusing between two reservoirs through tubes of water. It is notable that Ficks work primarily concerned diffusion in fluids, because at the time, diffusion in solids was not considered generally possible. Today, Ficks Laws form the core of our understanding of diffusion in solids, liquids, and gases (in the absence of bulk fluid motion in the latter two cases). When a diffusion process does not follow Ficks laws (which happens in cases of diffusion through porous media and diffusion of swelling penetrants, among others), it is referred to as non-Fickian'. | 7 | Physical Chemistry |
DNA methylation is the process in which a methyl group is added to either a cytosine or adenine. This process causes the activation or inactivation of gene expression, thereby resulting in gene regulation in eukaryotic cells. DNA methylation process is also known to be involved in certain types of cancer formation. In order for this chemical modification to occur, it is necessary that the target base flips out of the DNA double helix to allow the methyltransferases to catalyze the reaction. | 1 | Biochemistry |
It is disputed that Wöhlers synthesis sparked the downfall of the theory of vitalism, which states that organic matter possessed a certain vital force' common to all living things. Prior to the Wöhler synthesis, the work of John Dalton and Jöns Jacob Berzelius had already convinced chemists that organic and inorganic matter obey the same chemical laws. It took until 1845 when Kolbe reported another inorganic – organic conversion (of carbon disulfide to acetic acid) before vitalism started to lose support. Wöhler also did not, as some textbooks have claimed, act as a "crusader" against vitalism. A 2000 survey by historian Peter Ramberg found that 90% of chemical textbooks repeat some version of the Wöhler myth. | 0 | Organic Chemistry |
STARR-seq is a technique similar to MPRAs to assay enhancer activity of randomly sheared genomic fragments. In the original publication, randomly sheared fragments of the Drosophila genome were placed downstream of a minimal promoter. Candidate enhancers amongst the randomly sheared fragments will transcribe themselves using the minimal promoter. By using sequencing as a readout and controlling for input amounts of each sequence the strength of putative enhancers are assayed by this method. | 1 | Biochemistry |
The Kroll process was invented in 1940 by William J. Kroll in Luxembourg. After moving to the United States, Kroll further developed the method for the production of zirconium.
Many methods had been applied to the production of titanium metal, beginning with a report in 1887 by Nilsen and Pettersen using sodium, which was optimized into the commercial Hunter process. In the 1920s van Arkel had described the thermal decomposition of titanium tetraiodide to give highly pure titanium. Titanium tetrachloride was found to reduce with hydrogen at high temperatures to give hydrides that can be thermally processed to the pure metal. With this background, Kroll developed both new reductants and new apparatus for the reduction of titanium tetrachloride. Its high reactivity toward trace amounts of water and other metal oxides presented challenges. Significant success came with the use of calcium as a reductant, but the resulting mixture still contained significant oxide impurities. Major success using magnesium at 1000 °C using a molybdenum clad reactor, as reported to the Electrochemical Society in Ottawa. Krolls titanium was highly ductile reflecting its high purity. The Kroll process displaced the Hunter process and continues to be the dominant technology for the production of titanium metal, as well as driving the majority of the worlds production of magnesium metal. | 8 | Metallurgy |
To operate in this cycle, the desiccant is required to absorb moisture from air coming off of the coil that is colder and about 98% RH and to desorb moisture to air that is warmer and at a lower RH. The desiccant is regenerated by the vapor pressure differential inherent in the RH differences rather than heat or temperature difference. Desiccants that have a moisture sorption isotherm of the type shown in Figure 3 (Type III) are common, such as many formulations of silica gel. Type III desiccants absorb little moisture below 70% RH but many will take up more than their own weight in water from the air when presented with over 90% RH. The absorption isotherm is very steep between 90 and 100% RH. Desiccants of Type III have plenty of potential for the cycling of moisture from the air off of the coil, around 98% RH, over to the return air stream, typically around 50% RH. | 7 | Physical Chemistry |
The use of two wires of iridium/rhodium alloys can provide a thermocouple that can be used up to about 2000 °C in inert atmospheres. | 8 | Metallurgy |
* In the Markó–Lam deoxygenation, an alcohol could be almost instantaneously deoxygenated by electroreducing its toluate ester.
* In concept, adiponitrile is prepared from dimerizing acrylonitrile:
:In practice,the cathodic hydrodimerization of activated olefins is applied industrially in the synthesis of adiponitrile from two equivalents of acrylonitrile :
* The cathodic reduction of arene compounds to the 1,4-dihydro derivatives is similar to a Birch reduction. Examples from industry are the reduction of phthalic acid:
and the reduction of 2-methoxynaphthalene:
* The Tafel rearrangement, named for Julius Tafel, was at one time an important method for the synthesis of certain hydrocarbons from alkylated ethyl acetoacetate, a reaction accompanied by the rearrangement reaction of the alkyl group:
* The cathodic reduction of a nitrile to a primary amine in a divided cell; the cathodic reduction of benzyl cyanide to phenethylamine is shown:
* Cathodic reduction of a nitroalkene can give the oxime in good yield. At higher negative reduction potentials, the nitroalkene can be reduced further, giving the primary amine but with lower yield.
* Azobenzene is prepared in industrial electrosynthesis using nitrobenzene.
* An electrochemical carboxylation of a para-isobutyl benzyl chloride to Ibuprofen is promoted under supercritical carbon dioxide.
* Cathodic reduction of a carboxylic acid (oxalic acid) to an aldehyde (glyoxylic acid, shows as the rare aldehyde form) in a divided cell:
* Originally phenylpropanoic acid could be prepared from reduction of cinnamic acid by electrolysis.
* An electrocatalysis by a copper complex helps reduce carbon dioxide to oxalic acid; this conversion uses carbon dioxide as a feedstock to generate oxalic acid.
* It has been reported that formate can be formed by the electrochemical reduction of (in the form of bicarbonate) at a lead cathode at pH 8.6:
or
If the feed is and oxygen is evolved at the anode, the total reaction is: | 7 | Physical Chemistry |
In case of a porous materials many issues have been raised both about the physical meaning of the calculated pore diameter and the real possibility to use this equation for the calculation of the contact angle of the solid, even if this method is often offered by much software as consolidated. Change of weight as a function of time is measured. | 7 | Physical Chemistry |
Thyroids secretory capacity (G, also referred to as thyroids incretory capacity, maximum thyroid hormone output, T4 output or, if calculated from serum levels of thyrotropin and thyroxine, as SPINA-GT) is the maximum stimulated amount of thyroxine that the thyroid can produce in a given time-unit (e.g. one second). | 1 | Biochemistry |
For an electrode in a solution with a particular size and geometry, the reversible charge injection limit is the amount of charge that can move from the electrode to the surroundings without causing a chemical reaction that is irreversible. | 7 | Physical Chemistry |
In mathematical statistics, the Kullback–Leibler (KL) divergence (also called relative entropy and I-divergence), denoted , is a type of statistical distance: a measure of how one probability distribution is different from a second, reference probability distribution . A simple interpretation of the KL divergence of from is the expected excess surprise from using as a model when the actual distribution is . While it is a measure of how different two distributions are, and in some sense is thus a "distance", it is not actually a metric, which is the most familiar and formal type of distance. In particular, it is not symmetric in the two distributions (in contrast to variation of information), and does not satisfy the triangle inequality. Instead, in terms of information geometry, it is a type of divergence, a generalization of squared distance, and for certain classes of distributions (notably an exponential family), it satisfies a generalized Pythagorean theorem (which applies to squared distances).
In the simple case, a relative entropy of 0 indicates that the two distributions in question have identical quantities of information. Relative entropy is a nonnegative function of two distributions or measures. It has diverse applications, both theoretical, such as characterizing the relative (Shannon) entropy in information systems, randomness in continuous time-series, and information gain when comparing statistical models of inference; and practical, such as applied statistics, fluid mechanics, neuroscience and bioinformatics. | 7 | Physical Chemistry |
Bosons are quantum mechanical particles that follow Bose–Einstein statistics, or equivalently, that possess integer spin. These particles can be classified as elementary: these are the Higgs boson, the photon, the gluon, the W/Z and the hypothetical graviton; or composite like the atom of hydrogen, the atom of O, the nucleus of deuterium, mesons etc. Additionally, some quasiparticles in more complex systems can also be considered bosons like the plasmons (quanta of charge density waves).
The first model that treated a gas with several bosons, was the photon gas, a gas of photons, developed by Bose. This model leads to a better understanding of Plancks law and the black-body radiation. The photon gas can be easily expanded to any kind of ensemble of massless non-interacting bosons. The phonon gas', also known as Debye model, is an example where the normal modes of vibration of the crystal lattice of a metal, can be treated as effective massless bosons. Peter Debye used the phonon gas model to explain the behaviour of heat capacity of metals at low temperature.
An interesting example of a Bose gas is an ensemble of helium-4 atoms. When a system of He atoms is cooled down to temperature near absolute zero, many quantum mechanical effects are present. Below 2.17 kelvins, the ensemble starts to behave as a superfluid, a fluid with almost zero viscosity. The Bose gas is the most simple quantitative model that explains this phase transition. Mainly when a gas of bosons is cooled down, it forms a Bose–Einstein condensate, a state where a large number of bosons occupy the lowest energy, the ground state, and quantum effects are macroscopically visible like wave interference.
The theory of Bose-Einstein condensates and Bose gases can also explain some features of superconductivity where charge carriers couple in pairs (Cooper pairs) and behave like bosons. As a result, superconductors behave like having no electrical resistivity at low temperatures.
The equivalent model for half-integer particles (like electrons or helium-3 atoms), that follow Fermi–Dirac statistics, is called the Fermi gas (an ensemble of non-interacting fermions). At low enough particle number density and high temperature, both the Fermi gas and the Bose gas behave like a classical ideal gas. | 7 | Physical Chemistry |
The integrated stress response can be triggered within a cell due to either extrinsic or intrinsic conditions. Extrinsic factors include hypoxia, amino acid deprivation, glucose deprivation, viral infection and presence of oxidants. The main intrinsic factor is endoplasmic reticulum stress due to the accumulation of unfolded proteins. It has also been observed that the integrated stress response may trigger due to oncogene activation. The integrated stress response will either cause the expression of genes that fix the damage in the cell due to the stressful conditions, or it will cause a cascade of events leading to apoptosis, which occurs when the cell cannot be brought back into homeostasis. | 1 | Biochemistry |
In the simplest case, the linear N–H molecule (imidogen) has its nitrogen atom sp hybridized, with two of its four non-bonded electrons as a lone pair in an sp orbital and the other two occupying a degenerate pair of p orbitals. The electron configuration is consistent with Hund's rule: the low energy form is a triplet with one electron in each of the p orbitals and the high energy form is the singlet with an electron pair filling one p orbital and the other p orbital vacant.
As with carbenes, a strong correlation exists between the spin density on the nitrogen atom which can be calculated in silico and the zero-field splitting parameter D which can be derived experimentally from electron spin resonance. Small nitrenes such as NH or CFN have D values around 1.8 cm with spin densities close to a maximum value of 2. At the lower end of the scale are molecules with low D (< 0.4) values and spin density of 1.2 to 1.4 such as 9-anthrylnitrene and 9-phenanthrylnitrene. | 0 | Organic Chemistry |
Total inorganic carbon (C or TIC) is the sum of the inorganic carbon species.
Carbon compounds can be distinguished as either organic or inorganic, and dissolved or particulate, depending on their composition. Organic carbon forms the backbone of key components of organic compounds such as proteins, lipids, carbohydrates, and nucleic acids. Inorganic carbon is found primarily in simple compounds such as carbon dioxide (), carbonic acid (), bicarbonate (), and carbonate (). | 9 | Geochemistry |
A plasmid is a double stranded circular DNA molecule commonly used for molecular cloning. Plasmids are generally 2 to 4 kilobase-pairs (kb) in length and are capable of carrying inserts up to 15kb. Plasmids contain an origin of replication allowing them to replicate inside a bacterium independently of the host chromosome. Plasmids commonly carry a gene for antibiotic resistance that allows for the selection of bacterial cells containing the plasmid. Many plasmids also carry a reporter gene that allows researchers to distinguish clones containing an insert from those that do not. | 1 | Biochemistry |
Optical transfection is a biomedical technique that entails introducing nucleic acids (i.e. genetic material such as DNA) into cells using light. All cells are surrounded by a plasma membrane, which prevents many substances from entering or exiting the cell. Lasers can be used to burn a tiny hole in this membrane, allowing substances to enter. This is tremendously useful to biologists who are studying disease, as a common experimental requirement is to put things (such as DNA) into cells.
Typically, a laser is focussed to a diffraction limited spot (~1 µm diameter) using a high numerical aperture microscope objective. The plasma membrane of a cell is then exposed to this highly focussed light for a small amount of time (typically tens of milliseconds to seconds), generating a transient pore on the membrane. The generation of a photopore allows exogenous plasmid DNA, RNA, organic fluorophores, or larger objects such as semiconductor quantum nanodots to enter the cell. In this technique, one cell at a time is treated, making it particularly useful for single cell analysis.
This technique was first demonstrated in 1984 by Tsukakoshi et al., who used a frequency tripled Nd:YAG to generate stable and transient transfection of normal rat kidney cells. Since this time, the optical transfection of a host of mammalian cell types has been demonstrated using a variety of laser sources, including the 405 nm continuous wave (cw), 488 nm cw, or pulsed sources such as the 800 nm femtosecond pulsed Ti:Sapphire or 1064 nm nanosecond pulsed Nd:YAG. | 1 | Biochemistry |
The Gouy-Stodola theorem is often applied upon an open thermodynamic system, which can exchange heat with some thermal reservoirs. It holds both for systems which cannot exchange mass, and systems which mass can enter and leave.
Observe such a system, as sketched in the image shown, as it is going through some process. It is in contact with multiple reservoirs, of which one, that at temperature , is the environment reservoir. During the process, the system produces work and generates entropy. Under these conditions, the theorem has two general forms. | 7 | Physical Chemistry |
SedDB was developed to complement current geological data systems (PetDB, EarthChem, NavDat and Georoc) with an integrated and easily accessible compilation of geochemical data of marine and continental sediments to be utilized for sedimentological, geochemical, petrological, oceanographic, and paleoclimate research, as well as for educational purposes. | 9 | Geochemistry |
Medium-pressure mercury-vapor lamps have historically been the industry standard for curing products with ultraviolet light. The bulbs work by sending an electric discharge to excite a mixture of mercury and noble gases, generating a plasma. Once the mercury reaches a plasma state, it irradiates a high spectral output in the UV region of the electromagnetic spectrum. Major peaks in light intensity occur in the 240-270 nm and 350-380 nm regions. These intense peaks, when matched with the absorption profile of a photoinitiator, cause the rapid curing of materials. By modifying the bulb mixture with different gases and metal halides, the distribution of wavelength peaks can be altered, and material interactions are changed.
Medium-pressure lamps can either be standard gas-discharge lamps or electrodeless lamps, and typically use an elongated bulb to emit energy. By incorporating optical designs such an elliptical or even aconic reflector, light can either be focused or projected over a far distance. These lamps can often operate at over 900 degrees Celsius and produce UV energy levels over 10 W/cm. | 5 | Photochemistry |
Take the simplest CHX–CH system as an example; the donor orbital is σ(C–H) orbital and the acceptor is σ*(C–X). When moving from fluorine to chlorine, then to bromine, the electronegativity of the halogen and the energy level of the σ*(C–X) orbitals decreases. Consequently, the general trend of acceptors can be summarized as: π*(C=O)>σ*(C–Hal)>σ*(C–O)>σ*(C–N)>σ*(C–C), σ*(C–H). For donating orbitals, the nonbonding orbitals, or the lone pairs, are generally more effective than bonding orbitals due to the high energy levels. Also, different from acceptors, donor orbitals require less polarized bonds. Thus, the general trends for donor orbitals would be: n(N)>n(O)>σ(C–C), σ(C–H)>σ(C–N)>σ(C–O)>σ(C–S)>σ(C–Hal).
Stereoelectronic effect can be directional in specific cases. The radius of sulfur is much larger than the radius of carbon and oxygen. Thus the differences in C–S bond distances generate a much-amplified difference in the two stereoelectronic effects in 1,3-dithiane (σ(C–H) → σ*(C–S)) than in 1,3-dioxane(σ(C–H) → σ*(C–O)). The differences between C–C and C–S bonds shown below causes a significant difference in the distances between C–S and two C–H bonds. The shorter the difference is, the better the interaction and the stronger the stereoelectronic effect. | 4 | Stereochemistry |
In contrast with crystals, liquids have no long-range order (in particular, there is no regular lattice), so the structure factor does not exhibit sharp peaks. They do however show a certain degree of short-range order, depending on their density and on the strength of the interaction between particles. Liquids are isotropic, so that, after the averaging operation in Equation (), the structure factor only depends on the absolute magnitude of the scattering vector . For further evaluation, it is convenient to separate the diagonal terms in the double sum, whose phase is identically zero, and therefore each contribute a unit constant:
One can obtain an alternative expression for in terms of the radial distribution function : | 3 | Analytical Chemistry |
Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis. The term artificial photosynthesis is used loosely, refer to any scheme for capturing and storing energy from sunlight by producing a fuel, specifically a solar fuel. An advantage of artificial photosynthesis is that the solar energy can be immediately converted and stored. By contrast, using photovoltaic cells, sunlight is converted into electricity and then converted again into chemical energy for storage, with some necessary losses of energy associated with the second conversion. The byproducts of these reactions are environmentally friendly. Artificially photosynthesized fuel would be a carbon-neutral source of energy, which could be used for transportation or homes. The economics of artificial photosynthesis are not competitive. | 5 | Photochemistry |
Epimerization is a chemical process where an epimer is converted to its diastereomeric counterpart. It can happen in condensed tannins depolymerization reactions. Epimerization can be spontaneous (generally a slow process), or catalysed by enzymes, e.g. the epimerization between the sugars N-acetylglucosamine and N-acetylmannosamine, which is catalysed by renin-binding protein.
The penultimate step in Zhang & Trudells classic epibatidine synthesis is an example of epimerization. Pharmaceutical examples include epimerization of the erythro isomers of methylphenidate to the pharmacologically preferred and lower-energy threo isomers, and undesired in vivo' epimerization of tesofensine to brasofensine. | 4 | Stereochemistry |
Other bodies may define classes of reference material differently. WHO guidelines for biological reference materials provide the terms:
* Reference standards: materials that are used as calibrators in assays
* International biological measurement standard: a biological substance provided to enable the results of biological assay or immunological assay procedures to be expressed in the same way throughout the world
* Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests
* Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit
For chemical substances some pharmacopoeias use the WHO terms
* Primary chemical reference substance: a chemical reference substance ... whose value is accepted without requiring comparison to another chemical substance.
* Secondary chemical reference substance: substance whose characteristics are assigned and/or calibrated by comparison with a primary chemical reference substance.
The United States National Institute of Standards and Technology (NIST) uses the trade marked term Standard Reference Material (SRM) to denote a certified reference material that satisfies additional NIST-specific criteria. In addition, commercial producers adhering to criteria and protocols defined by NIST may use the trademark "NIST traceable reference material" to designate certified reference materials with a well-defined traceability linkage to existing NIST standards for chemical measurements. | 3 | Analytical Chemistry |
In response to a systemic bacterial infection, the immune system initiates a process known as "iron withholding". If bacteria are to survive, then they must obtain iron from their environment. Disease-causing bacteria do this in many ways, including releasing iron-binding molecules called siderophores and then reabsorbing them to recover iron, or scavenging iron from hemoglobin and transferrin. The harder the bacteria have to work to get iron, the greater a metabolic price they must pay. That means that iron-deprived bacteria reproduce more slowly. So, control of iron levels appears to be an important defense against many bacterial infections. Certain bacteria species have developed strategies to circumvent that defense, TB causing bacteria can reside within macrophages, which present an iron rich environment and Borrelia burgdorferi uses manganese in place of iron. People with increased amounts of iron, as, for example, in hemochromatosis, are more susceptible to some bacterial infections.
Although this mechanism is an elegant response to short-term bacterial infection, it can cause problems when it goes on so long that the body is deprived of needed iron for red cell production. Inflammatory cytokines stimulate the liver to produce the iron metabolism regulator protein hepcidin, that reduces available iron. If hepcidin levels increase because of non-bacterial sources of inflammation, like viral infection, cancer, auto-immune diseases or other chronic diseases, then the anemia of chronic disease may result. In this case, iron withholding actually impairs health by preventing the manufacture of enough hemoglobin-containing red blood cells. | 1 | Biochemistry |
Pipecolic acid (piperidine-2-carboxylic acid) is an organic compound with the formula HNCHCOH. It is a carboxylic acid derivative of piperidine and, as such, an amino acid, although not one encoded genetically. Like many other α-amino acids, pipecolic acid is chiral, although the S-stereoisomer is more common. It is a colorless solid.
Its biosynthesis starts from lysine. CRYM, a taxon-specific protein that also binds thyroid hormones, is involved in the pipecolic acid pathway. | 1 | Biochemistry |
Many cross-couplings entail forming carbon–carbon bonds.
The restrictions on carbon atom geometry mainly inhibit β-hydride elimination when complexed to the catalyst. | 0 | Organic Chemistry |
Zintl phases that contain molecule-like polyanions will often separate into its constituent anions and cations in liquid ammonia, ethylenediamene, crown ethers, or cryptand solutions. Therefore, they are referred to as Zintl ions. The term clusters is also used to emphasize them as groups with homonuclear bonding. The structures can be described by Wade's rules and occupy an area of transition between localized covalent bonds and delocalized skeletal bonding. Beyond the "aesthetic simplicity and beauty of their structures" and distinctive electronic properties, Zintl ions are also of interest in synthesis because of their unique and unpredictable behavior in solution.
The largest subcategory of Zintl ions is homoatomic clusters of group 14 or 15 elements. Some examples are listed below.
Many examples similarly exist for heteroatomic clusters where the polyanion is composed of greater than one main group element. Some examples are listed below. Zintl ions are also capable of reacting with ligands and transition metals, and further 'heteroatomic examples are discussed below (intermetalloid clusters). In some solvents, atoms exchange can occur between heteroatomic clusters. Additionally, it is notable that fewer large cluster examples exist. | 7 | Physical Chemistry |
Currently, the two most prominent areas of co-receptor research are investigations regarding HIV and cancer. HIV research is highly focused on the adaption of HIV strains to a variety of host co-receptors. Cancer research is mostly focused on enhancing the immune response to tumor cells, while some research also involves investigating the receptors expressed by the cancerous cells themselves. | 1 | Biochemistry |
CoQ is metabolized in all tissues, with the metabolites being phosphorylated in cells. CoQ10 is reduced to ubiquinol during or after absorption in the small intestine. It is absorbed by chylomicrons, and redistributed in the blood within lipoproteins. Its elimination occurs via biliary and fecal excretion. | 1 | Biochemistry |
In fuel cells, electro-osmosis causes protons moving through a proton exchange membrane (PEM) to drag water molecules from one side (anode) to the other (cathode). | 7 | Physical Chemistry |
Activation, in chemistry and biology, is the process whereby something is prepared or excited for a subsequent reaction. | 7 | Physical Chemistry |
Another possible biosignature might be morphology since the shape and size of certain objects may potentially indicate the presence of past or present life. For example, microscopic magnetite crystals in the Martian meteorite ALH84001 are one of the longest-debated of several potential biosignatures in that specimen. The possible biomineral studied in the Martian ALH84001 meteorite includes putative microbial fossils, tiny rock-like structures whose shape was a potential biosignature because it resembled known bacteria. Most scientists ultimately concluded that these were far too small to be fossilized cells. A consensus that has emerged from these discussions, and is now seen as a critical requirement, is the demand for further lines of evidence in addition to any morphological data that supports such extraordinary claims. Currently, the scientific consensus is that "morphology alone cannot be used unambiguously as a tool for primitive life detection". Interpretation of morphology is notoriously subjective, and its use alone has led to numerous errors of interpretation. | 2 | Environmental Chemistry |
Photocyclization can be carried out with ortho-, meta-, and para-substituted stilbene substrates.
ortho-Substituted substrates generally give 1-substituted phenanthrenes, unless the substituent
is a good leaving group, in which case elimination to form unsubstituted phenanthrene occurs. meta-
Substituted substrates give mixtures of 2- and 4-substituted products.
Substitution of the exocyclic double bond is well tolerated. Polycyclic aromatic compounds can be
synthesized using substrates containing multiple aromatic rings.
Stilbene derivatives containing fused aromatic systems may cyclize using either of two nonequivalent
ortho carbons. Which carbon reacts depends on both steric and electronic factors. Electronically, the
dihydrophenanthrene intermediate exhibiting greater aromatic stabilization is preferred. For instance, in
1-naphthyl-2-phenylethylene, electronic factors favor the formation of 1 over 2 in a ratio of 98.5:1.5.
ortho-Terphenyl substrates cyclize to the corresponding triphenylenes in the presence of an
oxidant, such as iodine. Oxygen is unsatisfactory because ring-opening to highly stabilized terphenyl is
faster than oxidation when oxygen is used.
Amides may cyclize to form lactams. Esters, which exist primarily in the trans conformation about the
C-O single bond, do not undergo this process efficiently.
Photocyclization can also form five-membered rings. In the vinyl naphthalene series, both oxidative and
non-oxidative processes are possible; although the latter requires a proton-transfer catalyst.
Cyclization of arylvinyl- or diarylamines provides indolines and carbazoles, respectively. In one
interesting example, the use of circularly polarized light provided 3 in slight enantiomeric excess.
In 2015, Li and Twieg reported a novel derivative of Mallory type photocyclizations and named it as photocyclodehydrofluorination (PCDHF). In the cyclization a stilbene (or ortho-terphenyl) with a pentafluorophenyl group, the fluorine atom can be used as a facile leaving group. | 5 | Photochemistry |
The high surface tension of water causes droplets to assume a nearly spherical shape, since a sphere has minimal surface area, and this shape therefore minimizes the solid-liquid surface energy. On contact of liquid with a surface, adhesion forces result in wetting of the surface. Either complete or incomplete wetting may occur depending on the structure of the surface and the fluid tension of the droplet.
The cause of self-cleaning properties is the hydrophobic water-repellent double structure of the surface. This enables the contact area and the adhesion force between surface and droplet to be significantly reduced, resulting in a self-cleaning process.
This hierarchical double structure is formed out of a characteristic epidermis (its outermost layer called the cuticle) and the covering waxes. The epidermis of the lotus plant possesses papillae 10 μm to 20 μm in height and 10 μm to 15 μm in width on which the so-called epicuticular waxes are imposed. These superimposed waxes are hydrophobic and form the second layer of the double structure. This system regenerates. This biochemical property is responsible for the functioning of the water repellency of the surface.
The hydrophobicity of a surface can be measured by its contact angle. The higher the contact angle the higher the hydrophobicity of a surface. Surfaces with a contact angle < 90° are referred to as hydrophilic and those with an angle >90° as hydrophobic. Some plants show contact angles up to 160° and are called ultrahydrophobic, meaning that only 2–3% of the surface of a droplet (of typical size) is in contact. Plants with a double structured surface like the lotus can reach a contact angle of 170°, whereby the droplet's contact area is only 0.6%. All this leads to a self-cleaning effect.
Dirt particles with an extremely reduced contact area are picked up by water droplets and are thus easily cleaned off the surface. If a water droplet rolls across such a contaminated surface the adhesion between the dirt particle, irrespective of its chemistry, and the droplet is higher than between the particle and the surface. This cleaning effect has been demonstrated on common materials such as stainless steel when a superhydrophobic surface is produced. As this self-cleaning effect is based on the high surface tension of water it does not work with organic solvents. Therefore, the hydrophobicity of a surface is no protection against graffiti.
This effect is of a great importance for plants as a protection against pathogens like fungi or algae growth, and also for animals like butterflies, dragonflies and other insects not able to cleanse all their body parts.
Another positive effect of self-cleaning is the prevention of contamination of the area of a plant surface exposed to light resulting in reduced photosynthesis. | 7 | Physical Chemistry |
Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions.
Temperature is a monotonic function of the average molecular kinetic energy of a substance. When a substance is heated, molecules begin to vibrate and move more, usually creating more distance between themselves. Substances which contract with increasing temperature are unusual, and only occur within limited temperature ranges (see examples below).
The relative expansion (also called strain) divided by the change in temperature is called the material's coefficient of linear thermal expansion and generally varies with temperature. As energy in particles increases, they start moving faster and faster, weakening the intermolecular forces between them and therefore expanding the substance. | 7 | Physical Chemistry |
Translation is one of the key energy consumers in cells, hence it is strictly regulated. Numerous mechanisms have evolved that control and regulate translation in eukaryotes as well as prokaryotes. Regulation of translation can impact the global rate of protein synthesis which is closely coupled to the metabolic and proliferative state of a cell. To delve deeper into this intricate process, scientists typically use a technique known as ribosome profiling. This method enables researchers to take a snapshot of the translatome, showing which parts of the mRNA are being translated into proteins by ribosomes at a given time. Ribosome profiling provides valuable insights into translation dynamics, revealing the complex interplay between gene sequence, mRNA structure, and translation regulation. Expanding on this concept, a more recent development is single-cell ribosome profiling, a technique that allows us to study the translation process at the resolution of individual cells. Single-cell ribosome profiling has the potential to shed light on the heterogeneous nature of cells, leading to a more nuanced understanding of how translation regulation can impact cell behavior, metabolic state, and responsiveness to various stimuli or conditions. | 1 | Biochemistry |
In many photo-productive systems this charge separation is kinetically isolated by delivery of the electron to a lower energy conductor attached to the p/n junction or into an electron transport chain. In this case some of the energy can be captured to do work. If the electron is not kinetically isolated thermodynamics will take over and the products will react with each other to regenerate the ground state starting material. This process is called recombination and the photon's energy is released as heat.
:Recombination of photoinduced oxidation
:[ML] + donor → [ML] + donor | 5 | Photochemistry |
The residence time of a fluid parcel is the total time that the parcel has spent inside a control volume (e.g.: a chemical reactor, a lake, a human body). The residence time of a set of parcels is quantified in terms of the frequency distribution of the residence time in the set, which is known as residence time distribution (RTD), or in terms of its average, known as mean residence time.
Residence time plays an important role in chemistry and especially in environmental science and pharmacology. Under the name lead time or waiting time it plays a central role respectively in supply chain management and queueing theory, where the material that flows is usually discrete instead of continuous. | 9 | Geochemistry |
The trifluoromethyl group is a functional group that has the formula -CF. The naming of is group is derived from the methyl group (which has the formula -CH), by replacing each hydrogen atom by a fluorine atom. Some common examples are trifluoromethane H–, 1,1,1-trifluoroethane –, and hexafluoroacetone –CO–. Compounds with this group are a subclass of the organofluorines. | 0 | Organic Chemistry |
Topochemical polymerization is a polymerization method performed by monomers aligned in the crystal state. In this process, the monomers are crystallised and polymerised under external stimuli such as heat, light, or pressure. Compared to traditional polymerisation, the movement of monomers was confined by the crystal lattice in topochemical polymerisation, giving rise to polymers with high crystallinity, tacticity, and purity. Topochemical polymerisation can also be used to synthesise unique polymers such as polydiacetylene that are otherwise hard to prepare.
Various reactions have been adopted in the field of topochemical polymerisation, such as [2+2], [4+2], [4+4], and [3+2] cycloaddition, linear addition between dienes, trienes, diacetylenes. Other than linear polymers, they can also be applied to the synthesis of two dimensional covalent networks. | 7 | Physical Chemistry |
Since the carbon cycle is tightly connected to the issue of ocean acidification, the most effective method for minimizing the effects of ocean acidification is to slow climate change. Anthropogenic inputs of CO can be reduced through methods such as limiting the use of fossil fuels and employing renewable energies. This will ultimately lower the amount of CO in the atmosphere and reduce the amount dissolved into the oceans. More intrusive methods to mitigate acidification involve a technique called enhanced weathering where powdered minerals like silicate are applied to the land or ocean surface. The powdered minerals enable accelerated dissolution, releasing cations, converting CO to bicarbonate and increasing the pH of the oceans. Other mitigation methods, like ocean iron fertilization, still need more experimentation and evaluation in order to be deemed effective. Ocean iron fertilization in particular has been shown to increase acidification in the deep ocean while only slightly reducing acidification at the surface. | 9 | Geochemistry |
Mitochondrial threshold effect is a phenomenon where the number of mutated mtDNA has surpassed a certain threshold which causes the electron transport chain and ATP synthesis of a mitochondrion to fail. There isn't a set number that needs to be surpassed, however, it is associated with an increase of the number of mutated mtDNA. When there is 60-80% of mutated mtDNA present, that is said to be the threshold level. While 60-80% is the general threshold level, this is also dependent on the individual, the specific organ in question and what the specific mutation is. There are three specific types of mitochondrial threshold effects: phenotypic threshold effect, biochemical threshold effect and translational threshold effect.
Threshold expression is a phenomenon in which phenotypic expression of a mitochondrial disease within an organ system occurs when the severity of the mutation, relative number of mutant mtDNA, and reliance of the organ system on oxidative phosphorylation combine in such a way that ATP production of the tissue falls below the level required by the tissue. The phenotype may be expressed even if the percentage of mutant mtDNA is below 50% if the mutation is severe enough. | 1 | Biochemistry |
In 1987 Parker was a fellow of the John Simon Guggenheim Foundation. In 2009 the Parker was elected a fellow of the American Chemical Society and she received the Francis P. Garvan-John M. Olin Medal from the American Chemical Society. In 2017 she received the Arthur C. Cope Scholar Award in recognition of her work synthesizing organic compounds. | 0 | Organic Chemistry |
Intravesical drug administration is the delivery of pharmaceuticals to the urinary bladder through a catheter. This route of administration is used for the therapy of bladder cancer and interstitial cystitis. The retention of dosage forms in the bladder is relatively poor, which is related to the need for a periodical urine voiding. Some mucoadhesive materials are able to stick to mucosal lining in the bladder, resist urine wash out effects and provide a sustained drug delivery. | 1 | Biochemistry |
dPCR measures the actual number of molecules (target DNA) as each molecule is in one droplet, thus making it a discrete “digital” measurement. It provides absolute quantification because dPCR measures the positive fraction of samples, which is the number of droplets that are fluorescing due to proper amplification. This positive fraction accurately indicates the initial amount of template nucleic acid. Similarly, qPCR utilizes fluorescence; however, it measures the intensity of fluorescence at specific times (generally after every amplification cycle) to determine the relative amount of target molecule (DNA), but cannot specify the exact amount without constructing a standard curve using different amounts of a defined standard. It gives the threshold per cycle (CT) and the difference in CT is used to calculate the amount of initial nucleic acid. As such, qPCR is an analog measurement, which may not be as precise due to the extrapolation required to attain a measurement.
dPCR measures the amount of DNA after amplification is complete and then determines the fraction of replicates. This is representative of an endpoint measurement as it requires the observation of the data after the experiment is completed. In contrast, qPCR records the relative fluorescence of the DNA at specific points during the amplification process, which requires stops in the experimental process. This “real-time” aspect of qPCR may theoretically affect results due to the stopping of the experiment. In practice, however, most qPCR thermal cyclers read each sample's fluorescence very quickly at the end of the annealing/extension step before proceeding to the next melting step, meaning this hypothetical concern is not actually relevant or applicable for the vast majority of researchers. dPCR measures the amplification by measuring the products of end point PCR cycling and is therefore less susceptible to the artifacts arising from impaired amplification efficiencies due to the presence of PCR inhibitors or primer template mismatch.
Real-time Digital PCR (rdPCR) combines the methodologies of digital PCR (dPCR) and quantitative PCR (qPCR), integrating the precision of dPCR with the real-time analysis capabilities of qPCR. This integration aims to provide enhanced sensitivity, specificity, and the ability for absolute quantification of nucleic acid sequences, contributing to the quantification of genetic material in scientific and clinical research.
qPCR is unable to distinguish differences in gene expression or copy number variations that are smaller than twofold. On the other hand, dPCR has a higher precision and has been shown to detect differences of less than 30% in gene expression, distinguish between copy number variations that differ by only 1 copy, and identify alleles that occur at frequencies less than 0.1%. | 1 | Biochemistry |
Many of the competitive single-molecule sequencing methods rely on the incorporation of fluorescently labeled nucleotides. In next-generation sequencing, the fluorescence signal of clusters can be easily detected. However, when the same concept is applied to single-molecule sequencing, the largest complication results from the high error rates. Because it is difficult to detect single labeled molecules, these platforms suffer from low signal-to-noise ratios, often resulting in misdetection or non-detection of fluorescent signals. In the case of magnetic sequencing, the signal measured is the changes in distance between two ends of a hairpin. Such signal can be readily detected with standard cameras. Thus, the signals are easier to detect, even without the use of expensive imaging devices. | 1 | Biochemistry |
Maximum entropy spectral estimation is a method of spectral density estimation. The goal is to improve the spectral quality based on the principle of maximum entropy. The method is based on choosing the spectrum which corresponds to the most random or the most unpredictable time series whose autocorrelation function agrees with the known values. This assumption, which corresponds to the concept of maximum entropy as used in both statistical mechanics and information theory, is maximally non-committal with regard to the unknown values of the autocorrelation function of the time series. It is simply the application of maximum entropy modeling to any type of spectrum and is used in all fields where data is presented in spectral form. The usefulness of the technique varies based on the source of the spectral data since it is dependent on the amount of assumed knowledge about the spectrum that can be applied to the model.
In maximum entropy modeling, probability distributions are created on the basis of that which is known, leading to a type of statistical inference about the missing information which is called the maximum entropy estimate. For example, in spectral analysis the expected peak shape is often known, but in a noisy spectrum the center of the peak may not be clear. In such a case, inputting the known information allows the maximum entropy model to derive a better estimate of the center of the peak, thus improving spectral accuracy. | 7 | Physical Chemistry |
Surface integrity is the surface condition of a workpiece after being modified by a manufacturing process. The term was coined by Michael Field and John F. Kahles in 1964.
The surface integrity of a workpiece or item changes the material's properties. The consequences of changes to surface integrity are a mechanical engineering design problem, but the preservation of those properties are a manufacturing consideration.
Surface integrity can have a great impact on a parts function; for example, Inconel 718 can have a fatigue limit as high as after a gentle grinding or as low as after electrical discharge machining (EDM). | 8 | Metallurgy |
Force spectroscopy is a method to measure forces between the tip and the sample. In this method the topographic feedback loop is disabled, and the tip is ramped towards the surface, then back. During the ramp the amplitude or frequency shift (depending on the mode of operation) is recorded to show the strength of the interaction at different distances. Force spectroscopy was originally performed in amplitude modulation mode, but is now more commonly performed in frequency modulation. The force is not directly measured during the spectroscopy measurement, instead the frequency shift is measured which must then be converted into a force. The frequency shift can be calculated, by:
where is the tips oscillation from its equilibrium position, and are the sensors stiffness and resonant frequency, and is the amplitude of oscillation. The angle brackets represent an average of one oscillation cycle. However, turning a measures frequency shift into a force, which is necessary during a real experiment, is much more complicated. Two methods are commonly used for this conversion, the Sader-Jarvis method and the Giessibl matrix method.
For measurements of chemical forces the effect of the long range van der Waals forces must be subtracted from the frequency shift data. Originally this was done by fitting a power law to the long range tail of the spectrum (when the tip is far from the surface) and extrapolating this over the short range interaction (tip close to the surface). This fitting, however, is very sensitive to where the cut-off between long and short range forces is chosen, causing results of questionable accuracy. Usually the most appropriate method is to perform two spectroscopy measurements, one over any molecule under study, and a second above a lower section of the clean surface, then to directly subtract the second from the first. This method is not applicable to features under study on a flat surface as no lower section may exist. | 6 | Supramolecular Chemistry |
When a concrete structure is heavily reinforced, the very dense rebar network can block the contraction movement of the protecting concrete cover located above the external layer of reinforcement bars due to the natural drying shrinkage process. As a consequence, a network of fissures with the characteristic honeycomb pattern also typical for the cracks resulting from the expansive chemical reactions (ASR, DEF, ESA) forms.
The formation of fissures in the concrete cover above the reinforcement bars represents a preferential pathway for the ingress of water and aggressive agents such as carbon dioxide| (lowering of pH around the rebar) and chloride anions (pitting corrosion) into concrete. The physical formation of cracks therefore favors the chemical degradation of concrete and aggravates steel corrosion. Physical and chemical degradation processes are intimately coupled, and the presence of water infiltrations also accelerates the formation of expansive products of harmful swelling chemical reactions (iron corrosion products, ASR, DEF, ISA, ESA).
Different approaches and methods have been developed to attempt to quantitatively estimate the influence of cracks in concrete structures on carbonation and chloride penetration. Their aim is to avoid underestimating the penetration depth of these harmful chemical agents and to calculate a sufficient thickness for the concrete cover to protect the rebar against corrosion during the whole service life of the concrete structure. | 8 | Metallurgy |
1,1-Dichloro-1-fluoroethane is mainly used as a solvent and foam blowing agent under the names R-141b and HCFC-141b. It is a class 2 ozone depleting substance undergoing a global phaseout from production and use under the Montreal Protocol since the late 1990s. It is being replaced by HFCs within some applications. | 2 | Environmental Chemistry |
The method numbers generally range from 1 to 9000 and may have modification letters appended to the end, signifying a newer version of the method has been released. Some ranges of numbers appear to be organized with intention, for example methods 1-99 being air methods or the 7000s being for hazardous waste. Others number ranges, however, seem to only contain random methods, like the 300 and 400 series both being for wet chemistry methods. | 3 | Analytical Chemistry |
Imprelis is a selective herbicide created by DuPont. The active ingredient is aminocyclopyrachlor, a synthetic auxin. | 2 | Environmental Chemistry |
MgCu is a binary intermetallic compound of magnesium (Mg) and copper (Cu) adopting cubic crystal structure, more specifically the C15 Laves phase. The space group of MgCu is Fdm with lattice parameter a = 7.04 Å. | 8 | Metallurgy |
Fulmer Research Institute was founded in 1945 as a UK contract research and development organization specializing in materials technology and related areas of physics and chemistry. It was modelled on American contract research companies such as Battelle Memorial Institute and The Mellon Institute of Industrial Research. In 1965 it was acquired by The Institute of Physics and the Physical Society, a rare case of a contract research company being owned by a Learned Society. Through the 1970s and 80s Fulmer evolved. Its services in testing, consultancy and certification were greatly strengthened while academic research declined. It continued to make important developments and innovations for industry and government until in 1990 it was split up and sold to other R & D and testing organizations.
A few of the landmark achievements during its forty five years were:
* The extraction of aluminium using sub-halide sublimation
* Aluminium-tin and aluminium-lead alloys for plain-bearings
* Chemical Vapour Deposition of metals and ceramics to produce coatings, tubes, crucibles etc.
* Fundamental research into aluminium copper alloys, leading to high strength formulations for the skin of high performance aircraft
* YQAF, a subsidiary company authorised to assess and accredit organizations to quality standards.
__TOC__ | 8 | Metallurgy |
The starting reactants for these reactions are hydrogen cyanide (HCN) as well as HCN derivatives and acetylene. Both of these are hypothesized to be present on the early Earth. The conditions this reaction occurs in are a relatively moderate temperature of 35 degrees C and in anoxic or oxygen free conditions. The early Earth was anoxic before the great oxidation event, making these conditions plausible. In the laboratory synthesis, a neutral phosphate buffer was used to maintain a stable, neutral pH. hydrogen sulfide (H2S) is used as a reductant in these reactions. The reactions are driven forward by ultraviolet radiation and catalyzed by Cu(I)-Cu(II) photoredox cycling. Some compounds in the system perform multiple roles. For example, phosphate serves as a buffer to maintain a neutral pH, acts as a catalyst in the synthesis of 2-aminooxazole and urea and serves as a reagent in the formation of glycerol-3-phosphate and ribonucleotides. The mechanisms involved in these reactions include reductive homologation processes to build larger, more complex molecules from the simple starting materials. The products of this reaction include the precursors of many amino acids, the precursors of lipids, and ribonucleotides. It is worth noting that most of the prebiotic monomers are not synthesized in their entirety by these reactions, only their precursors. The amino acid precursors would then be produced by Strecker synthesis reactions. Cyanosulfidic metabolism also does produce the precursors of both purines and pyrimidines ribonucleotides simultaneously. Many of the compounds produced also include intermediates in one-carbon metabolism. | 9 | Geochemistry |
Targeting of TNRF2 in tumor cells is associated with increased tumor cell death and decreased progression of tumor cell growth.
Increased expression of TNFR2 is found in breast cancer, cervical cancer, colon cancer, and renal cancer. A link between the expression of TNRF2 in tumor cells and late-stage cancer has been discovered. TNFR2 plays a significant role in tumor cell growth as it has been found that the loss of TNFR2 expression is linked with increased death of associated tumor cells and a significant standstill of further growth. There is therapeutic potential in the targeting of TNFR2 for cancer treatments through TNFR2 inhibition. | 1 | Biochemistry |
Individual progeny genomes are excised from genomic replicative concatemers starting by introducing breaks in replication origins, usually by the replication initiator protein. This results in the establishment of new replication forks that replicate the telomeres in a combination of terminal resolution and junction resolution and displaces individual ssDNA genomes from the replicative molecule. At the end of this process, the telomeres are folded back inwards to form hairpins on excised genomes. The extended-form termini created during excision resemble the extended-form molecules prior to terminal resolution, so they can be melted out and refolded into rabbit ears for additional rounds of replication. Within an infected cell, numerous replicative concatemers are therefore able to arise.
Displacement of progeny ssDNA genomes either occurs: predominantly or exclusively during active DNA replication, or when cells are assembling viral particles. Displacement of single strands may therefore be associated with packaging viral DNA into capsids. Earlier research suggested that the preassembled viral particle may sequester the genome in a 5′-to-3′ direction as it is displaced from the fork, but more recent research suggests that packaging is performed in a 3′-to-5′ direction driven by the NS1 helicase using newly synthesized single strands.
It is not clear if these single strands are released into the nucleoplasm so that packaging complexes are physically separate from replication complexes or if the replication intermediates serve as both replication and packaging substrates. In the latter case, newly displaced progeny genomes would be kept in the replication complex via interactions between their 5′-linked NS1 molecules and NS1 or capsid proteins that are physically associated with replicating DNA. Genomes are inserted into the capsid via an entrance called a portal situated at one of the icosahedral 5-fold axes of the capsid, which is possibly opposite of the opening from which genomes are expelled early in the replication cycle.
Strand selection for encapsidation likely does not involve specific packaging signals but may be predictable by the Kinetic Hairpin Transfer (KHT) mathematical model, which explains the distribution of the strands and terminal conformations of packaged genomes in terms of the efficiency with which each terminus type can undergo reactions that allow it to be copied and reformed. In other words, the KHT model postulates that the relative efficiency with which two genomic termini are resolved and replicated determines the distribution of amplified replication intermediates created during infection and ultimately the efficiency with which ssDNAs of characteristic polarity and terminal orientations are excised, which will then be packaged with equal efficiency.
Preferential excision of particular genomes is only apparent during packaging. Therefore, among parvoviruses that package strands of one sense, replication appears to be biphasic. At early times, both sense strands are excised. This is followed by a switch in the replication mode that allows for exclusive synthesis of a single sense for packaging. A modified form of the KHT model, called the preferential strand displacement model, proposes that the aforementioned switch in replication is caused by the onset of packaging because the substrate for packaging is probably a newly displaced DNA molecule. For heterotelomeric parvoviruses, imbalance of origin firing leads to preferential displacement of negative sense strands from the right-end origin. The relative frequency of sense strands in packaged virions can therefore be used to infer the type of resolution mechanism used during excision.
Shortly after the start of S-phase, translation of viral mRNA leads to the accumulation of capsid proteins in the nucleus. These proteins form into oligomers that are assembled into intact empty capsids. After encapsidation, complete virions may be exported from the nucleus to the exterior of the cell before disintegration of the nucleus. Disruption of the host cell environment may also occur later on in infection. This results in cell lysis via necrosis or apoptosis, which releases virions to the outside of the cell. | 1 | Biochemistry |
The suffix -yl is used in organic chemistry to form names of radicals, either separate species (called free radicals) or chemically bonded parts of molecules (called moieties). It can be traced back to the old name of methanol, "methylene" (from , wine and , wood, forest), which became shortened to "methyl" in compound names, from which -yl was extracted. Several reforms of chemical nomenclature eventually generalized the use of the suffix to other organic substituents.
The use of the suffix is determined by the number of hydrogen atoms that the substituent replaces on a parent compound (and also, usually, on the substituent). According to the 1993 IUPAC recommendations:
* -yl means that one hydrogen is replaced.
* -ylidene means that two hydrogens are replaced by a double bond between parent and substituent.
* -ylidyne means that three hydrogens are replaced by a triple bond between parent and substituent.
The suffix -ylidine is encountered sporadically, and appears to be a variant spelling of "-ylidene"; it is not mentioned in the IUPAC guidelines.
For multiple bonds of the same type, which link the substituent to the parent group, the infixes -di-, -tri-, -tetra-, etc., are used: -diyl (two single bonds), -triyl (three single bonds), -tetrayl (four single bonds), -diylidene (two double bonds).
For multiple bonds of different types, multiple suffixes are concatenated: -ylylidene (one single and one double), -ylylidyne (one single and one triple), -diylylidene (two single and one double).
The parent compound name can be altered in two ways:
* For many common compounds the substituent is linked at one end (the 1 position) and historically not numbered in the name. The IUPAC 2013 Rules however do require an explicit locant for most substituents in a preferred IUPAC name. The substituent name is modified by stripping -ane (see alkane) and adding the appropriate suffix. This is "recommended only for saturated acyclic and monocyclic hydrocarbon substituent groups and for the mononuclear parent hydrides of silicon, germanium, tin, lead, and boron". Thus, if there is a carboxylic acid called "X-ic acid", an alcohol ending "X-anol" (or "X-yl alcohol"), or an alkane called "X-ane", then "X-yl" typically denotes the same carbon chain lacking these groups but modified by attachment to some other parent molecule.
* The more general method omits only the terminal "e" of the substituent name, but requires explicit numbering of each yl prefix, even at position 1 (except for -ylidyne, which as a triple bond must terminate the substituent carbon chain). Pentan-1-yl is an example of a name by this method, and is synonymous with pentyl from the previous guideline.
Note that some popular terms such as "vinyl" (when used to mean "polyvinyl") represent only a portion of the full chemical name. | 0 | Organic Chemistry |
There are numerous cell signalling pathways that exhibit cross-talk with the PI3K pathway, potentially allowing cancer cells to escape inhibition of PI3K. As such, inhibition of the PI3K pathway alongside other targets could offer a synergistic response, such as that seen with PI3K and MEK co-targeted inhibition in lung cancer cells. More recently, co-targeting the PI3K pathway with PIM kinases has been suggested, with numerous pre-clinical studies suggesting the potential benefit of this approach. Development of panels of cell lines that are resistant to inhibition of the PI3K pathway may lead to the identification of future co-targets, and better understanding of which pathways may compensate for loss of PI3K signalling following drug treatment. Combined PI3K inhibition with more traditional therapies such as chemotherapy may also offer improved response over inhibition of PI3K alone. | 1 | Biochemistry |
The TLK model is credited as having originated from papers published in the 1920s by the German chemist W. Kossel and the Bulgarian chemist I. N. Stranski wherein the thermodynamic stability of step edges were discussed. | 7 | Physical Chemistry |
For a solid crystalline ionic compound the enthalpy change in forming the solid from gaseous ions is termed the lattice energy. The experimental value for the lattice energy can be determined using the Born–Haber cycle. It can also be calculated (predicted) using the Born–Landé equation as the sum of the electrostatic potential energy, calculated by summing interactions between cations and anions, and a short-range repulsive potential energy term. The electrostatic potential can be expressed in terms of the interionic separation and a constant (Madelung constant) that takes account of the geometry of the crystal. The further away from the nucleus the weaker the shield. The Born–Landé equation gives a reasonable fit to the lattice energy of, e.g., sodium chloride, where the calculated (predicted) value is −756 kJ/mol, which compares to −787 kJ/mol using the Born–Haber cycle. In aqueous solution the binding strength can be described by the Bjerrum or Fuoss equation as function of the ion charges, rather independent of the nature of the ions such as polarizability or size. The strength of salt bridges is most often evaluated by measurements of equilibria between molecules containing cationic and anionic sites, most often in solution. Equilibrium constants in water indicate additive free energy contributions for each salt bridge. Another method for the identification of hydrogen bonds also in complicated molecules is crystallography, sometimes also NMR-spectroscopy.
The attractive forces defining the strength of ionic bonding can be modeled by Coulomb's Law. Ionic bond strengths are typically (cited ranges vary) between 170 and 1500 kJ/mol. | 6 | Supramolecular Chemistry |
* ASBMB Award for Exemplary Contributions to Education
* ASBMB Leadership Awards
* ASBMB–Merck Award
* ASBMB Young Investigator Award
* Avanti Award in Lipids
* Bert and Natalie Vallee Award in Biomedical Science
* DeLano Award for Computational Biosciences
* Earl and Thressa Stadtman Distinguished Scientist Award
* Earl and Thressa Stadtman Young Scholar Award
* Herbert Tabor Research Award
* Mildred Cohn Award in Biological Chemistry - The Mildred Cohn Award in Biological Chemistry was established in 2013 to honor the scientific achievements of Mildred Cohn. Cohn was the first female president of the society, in 1978. The award of $5,000 is presented annually to a scientist who has made substantial advances in understanding biological chemistry using innovative physical approaches. The recipient is expected to deliver the Mildred Cohn Award lecture at the annual meeting.
* Ruth Kirschstein Diversity in Science Award
* The Alice and C. C. Wang Award in Molecular Parasitology
* Walter A. Shaw Young Investigator Award in Lipid Research
* William C. Rose Award | 1 | Biochemistry |
A variety of substituted derivatives of phen have been examined as ligands. Substituents at the 2,9 positions confer protection for the attached metal, inhibiting the binding of multiple equivalents of the phenanthroline. Such bulky ligands also favor trigonal or tetrahedral coordination at the metal. Phen itself form complexes of the type [M(phen)]Cl when treated with metal dihalides (M = Fe, Co, Ni). By contrast, neocuproine and bathocuproine form 1:1 complexes such as [Ni(neocuproine)Cl]. | 3 | Analytical Chemistry |
The Boyle temperature is formally defined as the temperature for which the second virial coefficient, , becomes zero.
It is at this temperature that the attractive forces and the repulsive forces acting on the gas particles balance out
This is the virial equation of state and describes a real gas.
Since higher order virial coefficients are generally much smaller than the second coefficient, the gas tends to behave as an ideal gas over a wider range of pressures when the temperature reaches the Boyle temperature (or when or are minimized).
In any case, when the pressures are low, the second virial coefficient will be the only relevant one because the remaining concern terms of higher order on the pressure. Also at Boyle temperature the dip in a PV diagram tends to a straight line over a period of pressure. We then have
where is the compressibility factor.
Expanding the van der Waals equation in one finds that . | 7 | Physical Chemistry |
It is expected that [CO] will reach 500–1000 ppm by 2100. 96% of the past 400,000 years experienced below 280 ppm CO. From this figure, it is highly probable that genotypes of today’s plants have diverged from their pre-industrial relatives.
The gene HIC (high carbon dioxide) encodes a negative regulator for the development of stomata in plants. Research into the HIC gene using Arabidopsis thaliana found no increase of stomatal development in the dominant allele, but in the ‘wild type’ recessive allele showed a large increase, both in response to rising CO levels in the atmosphere. These studies imply the plants response to changing CO levels is largely controlled by genetics. | 5 | Photochemistry |
A fluorogen is a ligand (fluorogenic ligand) which is not itself fluorescent, but when it is bound by a specific protein or RNA structure becomes fluorescent.
For instance, FAST is a variant of photoactive yellow protein which was engineered to bind chemical mimics of the GFP tripeptide chromophore.
Likewise, the spinach aptamer is an engineered RNA sequence which can bind GFP chromophore chemical mimics, thereby conferring conditional and reversible fluorescence on RNA molecules containing the sequence. | 1 | Biochemistry |
Example phases are:
*β-MgAl: 1168 atoms per unit cell, face-centred cubic, atoms arranged in Friauf polyhedra.
*ξ'–AlPdMn: 318 atoms per unit cell, face-centred orthorhombic, atoms arranged in Mackay-type clusters.
* (Bergman phase): 163 atoms per unit cell, body centred cubic, atoms arranged in Bergman clusters.
* (Taylor phase): 204 atoms per unit cell, face-centred orthorhombic, atoms arranged in Mackay-type clusters. | 8 | Metallurgy |
The naturally occurring calcium cycle has been altered by human intervention. Calcium is predominantly extracted from limestone deposits to be utilised by many industrial processes. Purification of iron ore and aluminium, replacing asbestos brake linings and some coatings for electric cables, are some of these major uses of calcium. Furthermore, calcium is used within the household to maintain alkaline pH of swimming pools, counteracting acidic disinfectants and in the food production industry to produce bicarbonate soda, some wines and dough.
With its widespread uses, a large volume of calcium must be obtained from mines and quarries to supply the high demand. As more limestone and water is removed from mines, underground stores of rock are often weakened making the ground more susceptible to sink holes. Sinkholes and mining both affect the presence of groundwater, potentially leading to a lower water table or altered pathways of flowing water. This may affect local ecosystems or farmland as the water supply is restricted. Additionally, the water that is released from mining areas will have higher concentrations of dissolved calcium. This can either be released into oceans or absorbed by the soil. Whilst not always detrimental, it alters the natural calcium cycle which may have flow-on effects for ecosystems. Furthermore, water being pumped from mines increases the danger of downstream flooding whilst simultaneously decreasing the volume on water in upstream reservoirs such as marshes, ponds of wetlands It is however important to note than limestone mining is comparatively less damaging than other mining process, with potential to restore the environment after the mine is no longer in use | 1 | Biochemistry |
Quinaldine red (pronounced , abbreviated QR) is a dark green–red or black solid that does not dissolve easily in water (it is partly miscible). In addition to being used as colored indicator, quinaldine red is also used as a fluorescence probe and an agent in bleaching. | 3 | Analytical Chemistry |
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