text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
Bromotrifluoromethane, commonly referred to by the code numbers Halon 1301, R13B1, Halon 13B1 or BTM, is an organic halide with the chemical formula CBrF. It is used for gaseous fire suppression as a far less toxic alternative to bromochloromethane. | 2 | Environmental Chemistry |
The Diels–Reese Reaction is a reaction between hydrazobenzene and dimethyl acetylenedicarboxylate (or related esters) first reported in 1934 by Otto Diels and Johannes Reese. Later work by others extended the reaction scope to include substituted hydrazobenzenes. The exact mechanism is not known. By changing the acidic or basic nature of the solvent, the reaction gives different products. With acetic acid as solvent (acidic), the reaction gives an diphenylpyrazolone. With xylene as solvent (neutral), the reaction gives an indole. With pyridine as solvent (basic), the reaction gives a carbomethoxyquinoline which can be degraded to a dihydroquinoline. | 0 | Organic Chemistry |
From 1985 to 1988, Bols did PhD with Professor Inge Lundt at the Technical University of Denmark. From 1988 to 1989, he did a post doc with professor Walter Szarek at Queens University before joining Leo Pharmaceuticals in 1989. From 1991 to 1995, he was Ass. Prof. at DTU only interrupted by a visit in the last 6 month of 1994 Gilbert Storks group at Columbia University. From 1995 to 2000, he was Assoc. Prof. (Lektor) at University of Aarhus during which period he became Dr. Scient. (1997). From 1998 to 2000 and from 2004 to 2006, he was Head of the chemistry department at university of Aarhus. From 2000 to 2005, he became Lundbeckfondsprofessor and subsequently (2005-2007) ordinary professor. In 2007, he became professor and Head of department of the Department of Chemistry at University of Copenhagen. | 0 | Organic Chemistry |
The cyclic relation is also known as the cyclic rule or the Triple product rule. Setting the second term in brackets equal to zero yields
Using a reciprocity relation for on this equation and reordering gives a cyclic relation (the triple product rule),
If, instead, reciprocity relations for and are used with subsequent rearrangement, a standard form for implicit differentiation is obtained: | 7 | Physical Chemistry |
After John Macadam and her children's deaths his widow, Elizabeth Clark, later remarried. She married the Reverend John Dalziel Dickie, who was pastor at Colac for 32 years. They married on 26 February 1868 They had four daughters. Elizabeth Dickie died aged 82 in 1915, in Brighton, Victoria, as the widow of the Rev. Dickie. Dickie had died 25 December 1909. | 3 | Analytical Chemistry |
Sulfates in solution in contact with concrete can cause chemical changes to the cement, which can cause significant microstructural effects leading to the weakening of the cement binder (chemical sulfate attack). Sulfate solutions can also cause damage to porous cementitious materials through crystallization and recrystallization (salt attack). Sulfates and sulfites are ubiquitous in the natural environment and are present from many sources, including gypsum (calcium sulfate) often present as an additive in blended cements which include fly ash and other sources of sulfate. With the notable exception of barium sulfate, most sulfates are slightly to highly soluble in water. These include acid rain where sulfur dioxide in the airshed is dissolved in rainfall to produce sulfurous acid. In lightning storms, the dioxide is oxidized to trioxide making the residual sulfuric acid in rainfall even more highly acidic. Concrete sewage infrastructure is most commonly attacked by sulfuric acid and sulfate anions arising from the oxidation of sulfide present in the sewage. Sulfides are formed when sulfate-reducing bacteria present in sewer mains reduce the ubiquitous sulfate ions present in water drains into hydrogen sulfide gas (). is volatile and released from water in the sewage atmosphere. It dissolves in a thin film of water condensed onto the wall of the sewer ducts where it is also accompanied by hydrogeno-sulfide () and sulfide () ions. When and anions are further exposed to atmospheric oxygen or to oxygenated stormwater, they are readily oxidized and produce sulfuric acid (in fact acidic hydrogen ions accompanied by sulfate and bisulfate ions) according to the respective oxidation reactions:
or,
The corrosion often present in the crown (top) of concrete sewers is directly attributable to this process – known as crown rot corrosion. | 8 | Metallurgy |
In 1964 Impalco decided to offer Fulmer for sale.
At that time Dr (later Sir) James Taylor, who was Chairman of Imperial Metal Industries (IMI), was also the Honorary Treasurer of the Institute of Physics and the Physical Society (IOP). He proposed that IOP should acquire Fulmer and thus become the first Learned Society to own a commercial research company. The Council of the IOP, in recommending the purchase of Fulmer to its membership, expressed the intention that, after providing for equipment needs, income from the investment in Fulmer was to be used to support the scientific and educational work of the IOP. The purchase was made possible by a grant from ICI, to be repaid over ten years from Fulmer profits. Thus, in 1965, IOP became the owner of Fulmer. | 8 | Metallurgy |
CBP and p300 are large nuclear proteins that bind to many sequence-specific factors involved in cell growth and/or differentiation, including c-jun and the adenoviral oncoprotein E1A. The protein encoded by the PCAF gene associates with p300/CBP. It has in vitro and in vivo binding activity with CBP and p300, and competes with E1A for binding sites in p300/CBP. It has histone acetyl transferase activity with core histones and nucleosome core particles, indicating that this protein plays a direct role in transcriptional regulation. | 1 | Biochemistry |
The classification of thermodynamic systems arose with the development of thermodynamics as a science.
Theoretical studies of thermodynamic processes in the period from the first theory of heat engines (Saadi Carnot, France, 1824) to the theory of dissipative structures (Ilya Prigozhin, Belgium, 1971) mainly concerned the patterns of interaction of thermodynamic systems with the environment.
At the same time, thermodynamic systems were mainly classified as isolated, closed and open, with corresponding properties in various thermodynamic states, for example, in states close to equilibrium, nonequilibrium and strongly nonequilibrium.
In 2010, Boris Dobroborsky (Israel, Russia) proposed a classification of thermodynamic systems according to internal processes consisting in energy redistribution (passive systems) and energy conversion (active systems). | 7 | Physical Chemistry |
Diagnostic serum creatinine studies are used to determine renal function. The reference interval is 0.6–1.3 mg/dL (53–115 μmol/L). Measuring serum creatinine is a simple test, and it is the most commonly used indicator of renal function.
A rise in blood creatinine concentration is a late marker, observed only with marked damage to functioning nephrons. Therefore, this test is unsuitable for detecting early-stage kidney disease. A better estimation of kidney function is given by calculating the estimated glomerular filtration rate (eGFR). eGFR can be accurately calculated without a 24-hour urine collection using serum creatinine concentration and some or all of the following variables: sex, age, weight, and (no longer https://www.kidney.org/content/laboratory-implementation-nkf-asn-task-force-reassessing-inclusion-race-diagnosing-kidney) race, as suggested by the American Diabetes Association. Many laboratories will automatically calculate eGFR when a creatinine test is requested. Algorithms to estimate GFR from creatinine concentration and other parameters are discussed in the renal function article.
A concern as of late 2010 relates to the adoption of a new analytical methodology, and a possible impact this may have in clinical medicine. Most clinical laboratories now align their creatinine measurements against a new standardized isotope dilution mass spectrometry (IDMS) method to measure serum creatinine. IDMS appears to give lower values than older methods when the serum creatinine values are relatively low, for example 0.7 mg/dL. The IDMS method would result in a comparative overestimation of the corresponding calculated GFR in some patients with normal renal function. A few medicines are dosed even in normal renal function on that derived GFR. The dose, unless further modified, could now be higher than desired, potentially causing increased drug-related toxicity. To counter the effect of changing to IDMS, new FDA guidelines have suggested limiting doses to specified maxima with carboplatin, a chemotherapy drug.
A 2009 Japanese study found a lower serum creatinine concentration to be associated with an increased risk for the development of type 2 diabetes in Japanese men. | 1 | Biochemistry |
Nikolay Dmitriyevich Zelinsky (; 6 February 1861 – 31 July 1953) was a Russian and Soviet chemist. Academician of the Academy of Sciences of the Soviet Union (1929).
Zelinsky studied at the University of Odessa and at the universities of Leipzig and Göttingen in Germany. Zelinsky was one of the founders of theory on organic catalysis. He was the inventor of the first effective filtering activated charcoal gas mask in the world (1915). | 0 | Organic Chemistry |
An index of biological integrity (IBI), also called an index of biotic integrity, is a scientific tool typically used to identify and classify water pollution problems, although there have been some efforts to apply the idea to terrestrial environments. An IBI associates anthropogenic influences on a water body with biological activity in the water body, and is formulated using data developed from biosurveys. Biological integrity is associated with how "pristine" an environment is and its function relative to the potential or original state of an ecosystem before human alterations were imposed. Biological integrity is built on the assumption that a decline in the values of an ecosystem's functions are primarily caused by human activity or alterations. The more an environment and its original processes are altered, then by definition, the less biological integrity it holds for the community as a whole. If these processes were to change over time naturally, without human influence, the integrity of the ecosystem would remain intact. Similar to the concept of ecosystem health, the integrity of the ecosystem relies heavily on the processes that occur within it because those determine which organisms can inhabit an area and the complexities of their interactions. Deciding which of the many possible states or conditions of an ecosystem is appropriate or desirable is a political or policy decision. | 2 | Environmental Chemistry |
P elements are transposable elements that were discovered in Drosophila as the causative agents of genetic traits called hybrid dysgenesis. The transposon is responsible for the P trait of the P element and it is found only in wild flies. They are also found in many other eukaryotes.
The name was first suggested by evolutionary biologist Margaret Kidwell, who, together with James Kidwell and John Sved, researched hybrid dysgenesis in Drosophila. They referred to strains as P of paternal and M of maternal if they contributed to hybrid dysgenesis in this reproductive role.
The P element encodes for an enzyme known as P transposase. Unlike laboratory-bred females, wild-type females are thought also to express an inhibitor to P transposase function, produced by the very same element. This inhibitor reduces the disruption to the genome caused by the movement of P elements, allowing fertile progeny. Evidence for this comes from crosses of laboratory females (which lack the P transposase inhibitor) with wild-type males (which have P elements). In the absence of the inhibitor, the P elements can proliferate throughout the genome, disrupting many genes and often proving lethal to progeny or rendering them sterile.
P elements are commonly used as mutagenic agents in genetic experiments with Drosophila. One advantage of this approach is that the mutations are easy to locate. In hybrid dysgenesis, one strain of Drosophila mates with another strain of Drosophila, producing hybrid offspring and causing chromosomal damage known to be dysgenic. Hybrid dysgenesis requires a contribution from both parents. For example, in the P-M system, where the P strain contributes paternally and M strain contributes maternally, dysgenesis can occur. The reverse cross, with an M cytotype father and a P mother, produces normal offspring, as it crosses in a P x P or M x M manner. P male chromosomes can cause dysgenesis when crossed with an M female. | 1 | Biochemistry |
Alternative non-helical models were briefly considered in the late 1970s as a potential solution to problems in DNA replication in plasmids and chromatin. However, the models were set aside in favor of the double-helical model due to subsequent experimental advances such as X-ray crystallography of DNA duplexes and later the nucleosome core particle, and the discovery of topoisomerases. Also, the non-double-helical models are not currently accepted by the mainstream scientific community. | 4 | Stereochemistry |
More than 100 immune system disorders affect humans, including inflammatory bowel diseases, multiple sclerosis, systemic lupus erythematosus, bloom syndrome, familial cold autoinflammatory syndrome, and dyskeratosis congenita. The Shapiro–Senapathy algorithm has been used to discover genes and mutations involved in many immune disorder diseases, including Ataxia telangiectasia, B-cell defects, epidermolysis bullosa, and X-linked agammaglobulinemia.
Xeroderma pigmentosum, an autosomal recessive disorder is caused by faulty proteins formed due to new preferred splice donor site identified using S&S algorithm and resulted in defective nucleotide excision repair.
Type I Bartter syndrome (BS) is caused by mutations in the gene SLC12A1. S&S algorithm helped in disclosing the presence of two novel heterozygous mutations c.724 + 4A > G in intron 5 and c.2095delG in intron 16 leading to complete exon 5 skipping.
Mutations in the MYH gene, which is responsible for removing the oxidatively damaged DNA lesion are cancer-susceptible in the individuals. The IVS1+5C plays a causative role in the activation of a cryptic splice donor site and the alternative splicing in intron 1, S&S algorithm shows, guanine (G) at the position of IVS+5 is well conserved (at the frequency of 84%) among primates. This also supported the fact that the G/C SNP in the conserved splice junction of the MYH gene causes the alternative splicing of intron 1 of the β type transcript.
Splice site scores were calculated according to S&S to find EBV infection in X-linked lymphoproliferative disease. Identification of Familial tumoral calcinosis (FTC) is an autosomal recessive disorder characterized by ectopic calcifications and elevated serum phosphate levels and it is because of aberrant splicing. | 1 | Biochemistry |
Post-mortem chemistry, also called necrochemistry or death chemistry, is a subdiscipline of chemistry in which the chemical structures, reactions, processes and parameters of a dead organism is investigated. Post-mortem chemistry plays a significant role in forensic pathology. Biochemical analyses of vitreous humor, cerebrospinal fluid, blood and urine is important in determining the cause of death or in elucidating forensic cases. | 1 | Biochemistry |
Chemically, levorphanol belongs to the morphinan class and is (−)-3-hydroxy-N-methyl-morphinan. It is the "left-handed" (levorotatory) stereoisomer of racemorphan, the racemic mixture of the two stereoisomers with differing pharmacology. The "right-handed" (dextrorotatory) enantiomer of racemorphan is dextrorphan (DXO), an antitussive, potent dissociative hallucinogen (NMDA receptor antagonist), and weakly active opioid. DXO is an active metabolite of the pharmaceutical drug dextromethorphan (DXM), which, analogously to DXO, is an enantiomer of the racemic mixture racemethorphan along with levomethorphan, the latter of which has similar properties to those of levorphanol. | 4 | Stereochemistry |
In molecular biology and genetics, upstream and downstream both refer to relative positions of genetic code in DNA or RNA. Each strand of DNA or RNA has a 5 end and a 3 end, so named for the carbon position on the deoxyribose (or ribose) ring. By convention, upstream and downstream relate to the 5 to 3 direction respectively in which RNA transcription takes place. Upstream is toward the 5 end of the RNA molecule and downstream is toward the 3 end. When considering double-stranded DNA, upstream is toward the 5 end of the coding strand for the gene in question and downstream is toward the 3 end. Due to the anti-parallel nature of DNA, this means the 3 end of the template strand is upstream of the gene and the 5 end is downstream.
Some genes on the same DNA molecule may be transcribed in opposite directions. This means the upstream and downstream areas of the molecule may change depending on which gene is used as the reference.
The terms upstream and downstream are sometimes also applied to a polypeptide sequence, where upstream refers to a region N-terminal and downstream to residues C-terminal of a reference point. | 1 | Biochemistry |
MUSE system mainly serves as a low-cost alternative to traditional histological analysis for cancer diagnostics with simpler and less time-consuming techniques. By integrating microscopy and fresh tissue fluorescence staining into an automated optical system, the overall acquiring time needed for getting digital images with diagnostic values can be much shortened into the scale of minutes comparing with conventional pathology, where general procedure can take from hours to days. The color-mapping techniques that correlated fluorescence staining to traditional H&E staining provide the same visual representation to pathologists based on existing knowledge with no need for additional training on image recognition.
Additionally, this system also has great potential to be used for intraoperative consultation, a method performed in pathologists lab that examine the microscopic features of tissue during oncological surgery usually for rapid cancer lesion and margin detection. It also can play an important role in biological and medical research, which might require examination on cellular features of tissue samples. In the future, the system can be further optimized to include more features including staining protocol, LEDs wavelength for more research usages and applications. | 5 | Photochemistry |
In organic chemistry, hydrocarbons (compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. aleiphar, fat, oil). Aliphatic compounds can be saturated (in which all the C-C bonds are single requiring the structure to be completed, or saturated, by hydrogen) like hexane, or unsaturated, like hexene and hexyne. Open-chain compounds, whether straight or branched, and which contain no rings of any type, are always aliphatic. Cyclic compounds can be aliphatic if they are not aromatic. | 0 | Organic Chemistry |
A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein). A term derived from the lac operon, structural genes are typically viewed as those containing sequences of DNA corresponding to the amino acids of a protein that will be produced, as long as said protein does not function to regulate gene expression. Structural gene products include enzymes and structural proteins. Also encoded by structural genes are non-coding RNAs, such as rRNAs and tRNAs (but excluding any regulatory miRNAs and siRNAs). | 1 | Biochemistry |
Flucloxacillin is used for both staphylococcal and streptococcal skin infections. These include folliculitis, carbuncles, impetigo, ecthyma, cellulitis, erysipelas, necrotising fasciitis, and infections of skin conditions such as eczema, scabies, ulcers and acne. Due to the widespread belief that dual-therapy is needed to cover both Staphylococcus and Streptococcus in cellulitis, flucloxacillin is sometimes given with the addition of benzylpenicillin for more severe cellulitis. However, support for this practice has lessened since findings in a study published in the Emergency Medicine Journal in 2005 did not show this combination to give additional clinical benefit. In the UK, using flucloxacillin alone is the first choice for treating cellulitis. Some other countries vary. | 4 | Stereochemistry |
Flow-induced dispersion analysis (FIDA) is an immobilization-free technology used for characterization and quantification of biomolecular interaction and protein concentration under native conditions. In the FIDA assay, the size of a ligand (indicator) with affinity to the target analyte is measured. When the indicator interacts with the analyte the apparent size increases and this change in size can be used to determine the analyte concentration and interaction. Additionally, the hydrodynamic radius of the analyte-indicator complex is obtained. A FIDA assay is typically completed in minutes and only requires a modest sample consumption of a few µl. | 1 | Biochemistry |
Diffusion process can also be calculated with Arrhenius equation:
where D is the diffusion coefficient and E is diffusion activation energy.
All three processes strongly depend on surface morphology at a certain time. For example, atoms tend to lend at the edges of a group of connected atoms, the so-called island, rather than on a flat surface, this reduces the total energy. When atoms diffuse and connect to an island, each atom tends to diffuse no further, because activation energy to detach itself out of the island is much higher. Moreover, if an atom landed on top of an island, it would not diffuse fast enough, and the atom would tend to move down the steps and enlarge it. | 7 | Physical Chemistry |
Carbohydrate Research is a peer-reviewed scientific journal covering research on the chemistry of carbohydrates. It is published by Elsevier and was established in 1965. The editor-in-chief is M. Carmen Galan (University of Bristol). According to the Journal Citation Reports, the journal has a 2022 impact factor of 3.1. | 0 | Organic Chemistry |
Geostationary Carbon Cycle Observatory (GeoCarb) was an intended NASA Venture-class Earth observation mission that was designed to measure the carbon cycle. Originally intended to be mounted on a commercial geostationary communication satellite operated by SES S.A., a lack of hosting opportunities drove NASA to seek a standalone spacecraft to carry GeoCarb. GeoCarb was to be stationed over the Americas and make observations between 50° North and South latitudes. Its primary mission was to conduct observations of vegetation health and stress, as well as observe the processes that govern the carbon exchange of carbon dioxide, methane, and carbon monoxide between the land, atmosphere, and ocean.
GeoCarb was a joint collaboration between NASA's Ames Research Center, Goddard Space Flight Center, and Jet Propulsion Laboratory; the University of Oklahoma; Colorado State University; the Lockheed Martin Advanced Technology Center of Palo Alto, California; and SES Government Solutions (now SES Space & Defense) of Reston, Florida.
On 29 November 2022, NASA announced the cancellation of development of the GeoCarb mission, citing cost overruns and the availability of other options to measure and observe greenhouse gases, like the EMIT instrument on the ISS and the upcoming Earth System Observatory. | 2 | Environmental Chemistry |
The Hyper-IL-6 protein has also been used to explore the physiologic role of Interleukin-6 trans-signaling in vivo. It turned out that this signaling mode was involved in many types of inflammation and cancer.
Hyper-IL-6 has helped to establish the concept of Interleukin-6 trans-signaling. Interleukin-6 trans-signaling mediates the pro-inflammatory activities of Interleukin-6 whereas Interleukin-6 classic signaling governs the protective and regenerative Interleukin-6 activities. Recently, in breast cancer patients, it was shown with the help of Hyper-IL-6 that IL-6 trans-signaling via phosphoinositid-3-kinase signaling activates disseminated cancer cells long before metastases are formed. In addition, it was demonstrated in mice that Hyper-IL-6 transneuronal delivery enabled functional recovery after severe spinal cord injury. | 1 | Biochemistry |
Stereochemical information of a chiral monomer can be expressed in a supramolecular polymer. Helical supramolecular polymer with P-and M-conformation are widely seen, especially those composed of disc-shaped monomers. When the monomers are achiral, both P-and M-helices are formed in equal amounts. When the monomers are chiral, typically due to the presence of one or more stereocenters in the side chains, the diastereomeric relationship between P- and M-helices leads to the preference of one conformation over the other. Typical example is a C-symmetric disk-shaped chiral monomer that forms helical supramolecular polymers via the "majority rule". A slight excess of one enantiomer of the chiral monomer resulted in a strong bias to either the right-handed or left-handed helical geometry at the supramolecular polymer level. In this case, a characteristic nonlinear dependence of the anisotropic factor, g, on the enantiomeric excess of a chiral monomer can be generally observed. Like in small molecule based chiral system, chirality of a supramolecular polymer also affected by chiral solvents. Some application such as a catalyst for asymmetric synthesis and circular polarized luminescence are observed in chiral supramolecular polymers too. | 6 | Supramolecular Chemistry |
In a rat model of premature aging, oxidative stress induced DNA damage in the neocortex and hippocampus was substantially higher than in normally aging control rats. Numerous studies have shown that the level of 8-oxo-2-deoxyguanosine, a product of oxidative stress, increases with age in the brain and muscle DNA of the mouse, rat, gerbil and human. Further information on the association of oxidative DNA damage with aging is presented in the article DNA damage theory of aging. However, it was recently shown that the fluoroquinolone antibiotic Enoxacin can diminish aging signals and promote lifespan extension in nematodes C. elegans 'by inducing oxidative stress. | 1 | Biochemistry |
Apoptotic DNA fragmentation is a key feature of apoptosis, a type of programmed cell death. Apoptosis is characterized by the activation of endogenous endonucleases, particularly the caspase-3 activated DNase (CAD), with subsequent cleavage of nuclear DNA into internucleosomal fragments of roughly 180 base pairs (bp) and multiples thereof (360, 540 etc.). The apoptotic DNA fragmentation is being used as a marker of apoptosis and for identification of apoptotic cells either via the DNA laddering assay, the TUNEL assay, or the by detection of cells with fractional DNA content ("sub G cells") on DNA content frequency histograms e.g. as in the Nicoletti assay. | 1 | Biochemistry |
A superhydrophobic coating is a thin surface layer that repels water. It is made from superhydrophobic (ultrahydrophobicity) materials. Droplets hitting this kind of coating can fully rebound. Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and the other provides low surface energy. | 7 | Physical Chemistry |
Concentrated fluoride solutions are corrosive. Gloves made of nitrile rubber are worn when handling fluoride compounds. The hazards of solutions of fluoride salts depend on the concentration. In the presence of strong acids, fluoride salts release hydrogen fluoride, which is corrosive, especially toward glass. | 1 | Biochemistry |
Design and fabrication of E-AB aptamers is consistent with methods used for previously reported aptamers. SELEX is a well known selection method for fabrication and selection of nucleotide aptamers. In 1990s, scientists introduced SELEX. Aptamers are chosen based on their in vitro target recognition through this process. In SELEX, aptamers are chosen based on their ability to recognize specific targets. This method involves three key steps: First, single-stranded nucleic acids are bound to the target. Next, the bound nucleic acids are separated from unbound ones. Finally, Polymerase Chain Reaction (PCR) amplifies the nucleic acids that have an affinity for the target, allowing for further screening or functional analysis. Following SELEX, high-throughput sequencing is used to identify sequences that have been enriched due to their target-binding abilities. SELEX is relatively limited by the amount of enrichment that can be achieved in a single round. A less-reported screening method for aptamer fabrication that overcomes this limitation is affinity-based library enrichment that has been termed Particle Display. | 7 | Physical Chemistry |
Ghodsi Mohammadi Ziarani (born 1964) is an Iranian chemist and Professor of Organic Chemistry at Alzahra University. Mohammadi Ziarani is among the most-cited Iranian researchers and is known for her works on organic chemistry, nanochemistry, multi-component reactions, natural product synthesis, and asymmetric synthesis. | 0 | Organic Chemistry |
In the 1960s and '70s, the ever-growing list of strongly interacting particles — mesons and baryons — made it clear to physicists that none of these particles is elementary. Geoffrey Chew and others went so far as to question the distinction between composite and elementary particles, advocating a "nuclear democracy" in which the idea that some particles were more elementary than others was discarded. Instead, they sought to derive as much information as possible about the strong interaction from plausible assumptions about the S-matrix, which describes what happens when particles of any sort collide, an approach advocated by Werner Heisenberg two decades earlier.
The reason the program had any hope of success was because of crossing, the principle that the forces between particles are determined by particle exchange. Once the spectrum of particles is known, the force law is known, and this means that the spectrum is constrained to bound states which form through the action of these forces. The simplest way to solve the consistency condition is to postulate a few elementary particles of spin less than or equal to one, and construct the scattering perturbatively through field theory, but this method does not allow for composite particles of spin greater than 1 and without the then undiscovered phenomenon of confinement, it is naively inconsistent with the observed Regge behavior of hadrons.
Chew and followers believed that it would be possible to use crossing symmetry and Regge behavior to formulate a consistent S-matrix for infinitely many particle types. The Regge hypothesis would determine the spectrum, crossing and analyticity would determine the scattering amplitude (the forces), while unitarity would determine the self-consistent quantum corrections in a way analogous to including loops. The only fully successful implementation of the program required another assumption to organize the mathematics of unitarity (the narrow resonance approximation). This meant that all the hadrons were stable particles in the first approximation, so that scattering and decays could be thought of as a perturbation. This allowed a bootstrap model with infinitely many particle types to be constructed like a field theory — the lowest order scattering amplitude should show Regge behavior and unitarity would determine the loop corrections order by order. This is how Gabriele Veneziano and many others constructed string theory, which remains the only theory constructed from general consistency conditions and mild assumptions on the spectrum.
Many in the bootstrap community believed that field theory, which was plagued by problems of definition, was fundamentally inconsistent at high energies. Some believed that there is only one consistent theory which requires infinitely many particle species and whose form can be found by consistency alone. This is nowadays known not to be true, since there are many theories which are nonperturbatively consistent, each with their own S-matrix. Without the narrow-resonance approximation, the bootstrap program did not have a clear expansion parameter, and the consistency equations were often complicated and unwieldy, so that the method had limited success. It fell out of favor with the rise of quantum chromodynamics, which described mesons and baryons in terms of elementary particles called quarks and gluons.
Bootstrapping here refers to pulling oneself up by ones bootstraps,' as particles were surmised to be held together by forces consisting of exchanges of the particles themselves.
In 2017 Quanta Magazine published an article in which bootstrap was said to enable new discoveries in the field of quantum theories. Decades after bootstrap seemed to be forgotten, physicists have discovered novel "bootstrap techniques" that appear to solve many problems. The bootstrap approach is said to be "a powerful tool for understanding more symmetric , perfect theories that, according to experts, serve as signposts or building blocks in the space of all possible quantum field theories". | 7 | Physical Chemistry |
In Chemistry, a kryptoracemic compound or kryptoracemate (sometimes false conglomerate) is a racemic compound crystallizing in a Sohncke space group.
In most of the cases, racemic compounds crystallize in centrosymmetric crystal structures. In a kryptoracemic compound the chemical composition of the crystal is racemic although the crystal belongs to space groups in which all enantiomerically pure molecules have to crystallize.
Crystallographically, in kryptoracemic compounds, the number of independent molecules in the asymmetric unit (Z′) is necessarily greater than 1 and should take an even value (to respect the racemic composition). By extension, the scalemic compounds (or unbalanced compounds), i.e. crystal with non-stoichiometric ratio of enantiomer, crystallizing in Sohncke space group are sometimes included in kryptoracemic compounds although they are not strito-sensu kryptoracemic. | 4 | Stereochemistry |
Levan has shown uses for burned tissue, anti-inflammation, and aquaculture. By combining levan into a thin film, it is able to activate an enzyme known as metalloproteinase which increases the recovery and healing process. In the case of inflammation, levan interacts with the aggregating cells and affects their adhesion to the blood vessel causing reduced accumulation. In aquaculture, results have shown that levan incorporated diets could possibly cause an increase in aggregation of viruses allowing for easier phagocytic removal. Levan produced by Pantoea agglomerans ZMR7 was reported to decrease the viability of rhabdomyosarcoma (RD) and breast cancer (MDA) cells compared with untreated cancer cells. In addition, it has high antiparasitic activity against the promastigote of Leishmania tropica | 1 | Biochemistry |
The Journal of Electroanalytical Chemistry is a peer-reviewed scientific journal on electroanalytical chemistry, published by Elsevier twice per month. It was originally established in 1959 under the current name, but was known as the Journal of Electroanalytical Chemistry and Interfacial Electrochemistry from 1967 to 1991. It is currently edited by X.-H. Xia (Nanjing University). The journal is associated with the International Society of Electrochemistry. While the journal is now published exclusively in English, earlier volumes sometimes published articles in French and German.
The journal, which The New York Times described as "a specialty publication not widely circulated" in 1990, became more broadly known in 1989 when Martin Fleischmann and Stanley Pons published a description of their controversial cold fusion research in it, withdrawing their work from publication in Nature after questions were raised during peer review there. | 3 | Analytical Chemistry |
Examples of restriction enzymes include:
Key:<br/>
= blunt ends<br/>
N = C or G or T or A<br/>
W = A or T | 1 | Biochemistry |
The dynamic behavior of Min proteins has been reconstituted in vitro using artificial lipid bilayers, with varying lipid composition and different confinement geometry as mimics for the cell membrane. The first pattern to be reconstituted were spiraling waves of MinD chased by MinE, followed by the reconstitution of waves of all three proteins, MinD, MinE and MinC. Importantly, MinD and MinE can self-organize into a wide variety of patterns depending on the reaction conditions.
Additional study is required to elucidate the extent of temporal and spatial signaling permissible by this biological function. These in vitro systems offered unprecedented access to features such as residence times and molecular motility. | 1 | Biochemistry |
Ferric reducing ability of plasma (FRAP, also Ferric ion reducing antioxidant power) is an antioxidant capacity assay that uses Trolox as a standard. The FRAP assay was first performed by Iris Benzie and J. J. Strain of the Human Nutrition Research Group at the University of Ulster, Coleraine. The method is based on the formation of O-Phenanthroline-Fe(2+) complex and its disruption in the presence of
chelating agents. This assay is often used to measure the antioxidant capacity of foods, beverages and nutritional supplements containing polyphenols. | 1 | Biochemistry |
In 2009, Illumina released its first whole genome sequencers that were approved for clinical as opposed to research-only use and doctors at academic medical centers began quietly using them to try to diagnose what was wrong with people whom standard approaches had failed to help. In 2009, a team from Stanford led by Euan Ashley performed clinical interpretation of a full human genome, that of bioengineer Stephen Quake. In 2010, Ashley's team reported whole genome molecular autopsy and in 2011, extended the interpretation framework to a fully sequenced family, the West family, who were the first family to be sequenced on the Illumina platform. The price to sequence a genome at that time was $19,500USD, which was billed to the patient but usually paid for out of a research grant; one person at that time had applied for reimbursement from their insurance company. For example, one child had needed around 100 surgeries by the time he was three years old, and his doctor turned to whole genome sequencing to determine the problem; it took a team of around 30 people that included 12 bioinformatics experts, three sequencing technicians, five physicians, two genetic counsellors and two ethicists to identify a rare mutation in the XIAP that was causing widespread problems.
Due to recent cost reductions (see above) whole genome sequencing has become a realistic application in DNA diagnostics. In 2013, the 3Gb-TEST consortium obtained funding from the European Union to prepare the health care system for these innovations in DNA diagnostics. Quality assessment schemes, Health technology assessment and guidelines have to be in place. The 3Gb-TEST consortium has identified the analysis and interpretation of sequence data as the most complicated step in the diagnostic process. At the Consortium meeting in Athens in September 2014, the Consortium coined the word genotranslation for this crucial step. This step leads to a so-called genoreport. Guidelines are needed to determine the required content of these reports.
Genomes2People (G2P), an initiative of Brigham and Womens Hospital and Harvard Medical School was created in 2011 to examine the integration of genomic sequencing into clinical care of adults and children. G2Ps director, Robert C. Green, had previously led the REVEAL study — Risk EValuation and Education for Alzheimers Disease – a series of clinical trials exploring patient reactions to the knowledge of their genetic risk for Alzheimers.
In 2018, researchers at Rady Childrens Hospital Institute for Genomic Medicine in San Diego determined that rapid whole-genome sequencing (rWGS) could diagnose genetic disorders in time to change acute medical or surgical management (clinical utility) and improve outcomes in acutely ill infants. In a retrospective cohort study of acutely ill inpatient infants in a regional childrens hospital from July 2016-March 2017, forty-two families received rWGS for etiologic diagnosis of genetic disorders. The diagnostic sensitivity of rWGS was 43% (eighteen of 42 infants) and 10% (four of 42 infants) for standard genetic tests (P = .0005). The rate of clinical utility of rWGS (31%, thirteen of 42 infants) was significantly greater than for standard genetic tests (2%, one of 42; P = .0015). Eleven (26%) infants with diagnostic rWGS avoided morbidity, one had a 43% reduction in likelihood of mortality, and one started palliative care. In six of the eleven infants, the changes in management reduced inpatient cost by $800,000-$2,000,000. The findings replicated a prior study of the clinical utility of rWGS in acutely ill inpatient infants, and demonstrated improved outcomes, net healthcare savings and consideration as a first tier test in this setting.
A 2018 review of 36 publications found the cost for whole genome sequencing to range from $1,906USD to $24,810USD and have a wide variance in diagnostic yield from 17% to 73% depending on patient groups. | 1 | Biochemistry |
Agricultural practices such as allowing livestock to graze near water bodies, spreading manure as fertilizer on fields during wet periods, using sewage sludge biosolids and allowing livestock watering in streams can all contribute to fecal coliform contamination. | 3 | Analytical Chemistry |
Non-photochemical quenching is measured by the quenching of chlorophyll fluorescence and is distinguished from photochemical quenching by applying a bright light pulse under actinic light to transiently saturate photosystem II reaction center and compare the maximal yield of fluorescence emission under light and dark-adapted state. Non-photochemical quenching is not affected if the pulse of light is short. During this pulse, the fluorescence reaches the level reached in the absence of any photochemical quenching, known as maximum fluorescence, .
For further discussion, see Measuring chlorophyll fluorescence and Plant stress measurement.
Chlorophyll fluorescence can easily be measured with a chlorophyll fluorometer. Some fluorometers can calculate NPQ and photochemical quenching coefficients (including qP, qN, qE and NPQ), as well as light and dark adaptation parameters (including Fo, Fm, and Fv/Fm). | 5 | Photochemistry |
Volkensin is a eukaryotic ribosome-inactivating protein found in the Adenia volkensii plant. It is a glycoprotein with two subunits A and B. A subunit is linked to B subunit with disulfide bridges and non-covalent bonds. B subunit is responsible for binding to the galactosyl-terminated receptors on the cell membrane that allows the entry the A subunit of the toxin into the cell, which performs the inhibitory function. Volkensin is a galactose specific lectin that can inhibit protein synthesis in whole cells and in cell-free lysates. This protein can be included into the category of risin like toxins and it resembles modeccin, the toxin of Adenia digitata. Although very similar in composition, volkensin contains more cysteine residues and more than twice as much sugar than modeccin, due to high content of galactose and mannose. In addition, volkensin is able to inhibit protein synthesis at concentrations 10 times lower than required for modeccin. From gene sequencing analysis, volkensin was found to be coded by 1569-bp ORF, that is 523 amino acid residues without introns. The internal linker sequence is 45 bp. The active site of the A subunit contains Ser203, a novel residue that is conserved in all ribosome inactivating proteins.
The toxin can be isolated via affinity chromatography, using acid-treated Sepharose 6B.
Volkensin, and toxins alike are studied to understand protein entry into the cell and many have been found to have antitumor applicability. Rats that have been administered a high dose of volkensin died between 7 and 12 hours. For 1–2 hours after poisoning, rats behaved normally and then became sedated until death with short-lasting seizures. Rats that have been administered lower doses died within several days and showed wax-like peritoneal fat, which indicated the formation of a pancreatic lesion.
In addition, volkensin has been also found to agglutinate red blood cells without any specificity for a particular blood group. This is likely due to its affinity for galactose residues, which are in common with all three blood groups.
Volkensin is a potent neurotoxin that can kill neurons. It is able to bind to the axon terminal of neurons, where it is internalized and transported to the cell body and inactivates ribosomes, thereby killing the neuron. Experiments performed in vitro showed increased toxicity of volkensin to microglia and astrocytes. | 1 | Biochemistry |
Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-spanning receptors usually expressed on sentinel cells such as macrophages and dendritic cells, that recognize structurally conserved molecules derived from microbes. Once these microbes have reached physical barriers such as the skin or intestinal tract mucosa, they are recognized by TLRs, which activate immune cell responses. The TLRs include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, TLR11, TLR12, and TLR13. Humans lack genes for TLR11, TLR12 and TLR13 and mice lack a functional gene for TLR10. The receptors TLR1, TLR2, TLR4, TLR5, TLR6, and TLR10 are located on the cell membrane, whereas TLR3, TLR7, TLR8, and TLR9 are located in intracellular vesicles (because they are sensors of nucleic acids).
TLRs received their name from their similarity to the protein coded by the toll gene. | 1 | Biochemistry |
A molecule is composed of one or more chemical bonds between molecular orbitals of different atoms. A molecule may be polar either as a result of polar bonds due to differences in electronegativity as described above, or as a result of an asymmetric arrangement of nonpolar covalent bonds and non-bonding pairs of electrons known as a full molecular orbital.
While the molecules can be described as "polar covalent", "nonpolar covalent", or "ionic", this is often a relative term, with one molecule simply being more polar or more nonpolar than another. However, the following properties are typical of such molecules. | 7 | Physical Chemistry |
Integrated discrete Multiple Organ Culture (IdMOC) is an in vitro, cell culture based experimental model for the study of intercellular communication. In conventional in vitro systems, each cell type is studied in isolation ignoring critical interactions between organs or cell types. IdMOC technology is based on the concept that multiple organs signal or communicate via the systemic circulation (i.e., blood).
The IdMOC plate consists of multiple inner wells within a large interconnecting chamber. Multiple cell types are first individually seeded in the inner wells and, when required, are flooded with an overlying medium to facilitate well-to-well communication. Test material can be added to the overlying medium and both media and cells can be analyzed individually. Plating of hepatocytes with other organ-specific cells allows evaluation of drug metabolism and organotoxicity.
The IdMOC system has numerous applications in drug development, such as the evaluation of drug metabolism and toxicity. It can simultaneously evaluate the toxic potential of a drug on cells from multiple organs and evaluate drug stability, distribution, metabolite formation, and efficacy. By modeling multiple-organ interactions, IdMOC can examine the pharmacological effects of a drug and its metabolites on target and off-target organs as well as evaluate drug-drug interactions by measuring cytochrome P450 (CYP) induction or inhibition in hepatocytes.
IdMOC can also be used for routine and high throughput screening of drugs with desirable ADME or ADME-Tox properties. In vitro toxicity screening using hepatocytes in conjunction with other primary cells such as cardiomyocytes (cardiotoxicity model), kidney proximal tubule epithelial cells (nephrotoxicity model), astrocytes (neurotoxicity model), endothelial cells (vascular toxicity model), and airway epithelial cells (pulmonary toxicity model) is invaluable to the drug design and discovery process.
The IdMOC was patented by Dr. Albert P. Li in 2004. | 1 | Biochemistry |
In practice, the osmotic pressure produced by an ideally dilute solution would be too small to be accurately measured. For accurate measurements, solutions are not ideally dilute and a virial equation is used to account for deviations from ideal behavior and allow the calculation of . The virial equation takes a form similar to van ‘t Hoff's law of osmotic pressure, but contains additional constants to account for non-ideal behavior:
where are constants and is still the concentration of polymer 1. This virial equation may be represented in different additional forms:
where and are constants and . | 7 | Physical Chemistry |
Stringing is perhaps the most crucial of these effects, and is often seen on adhesive tapes. Stringing occurs when a separation of two surfaces is beginning and molecules at the interface bridge out across the gap, rather than cracking like the interface itself. The most significant consequence of this effect is the restraint of the crack. By providing the otherwise brittle interfacial bonds with some flexibility, the molecules that are stringing across the gap can stop the crack from propagating. Another way to understand this phenomenon is by comparing it to the stress concentration at the point of failure mentioned earlier. Since the stress is now spread out over some area, the stress at any given point has less of a chance of overwhelming the total adhesive force between the surfaces. If failure does occur at an interface containing a viscoelastic adhesive agent, and a crack does propagate, it happens by a gradual process called “fingering”, rather than a rapid, brittle fracture.
Stringing can apply to both the diffusive bonding regime and the chemical bonding regime. The strings of molecules bridging across the gap would either be the molecules that had earlier diffused across the interface or the viscoelastic adhesive, provided that there was a significant volume of it at the interface. | 6 | Supramolecular Chemistry |
For more complex systems that are representative of water-surface interactions in nature, the Cassie-Baxter model is used. This model takes into consideration the fact that a water droplet may trap air between itself and the surface that it is on. The Cassie-Baxter model is described by the following equation:
= Contact angle of water predicted by Cassie-Baxter's model
= Liquid-air fraction, the fraction of the liquid droplet that is in contact with air | 7 | Physical Chemistry |
Polluted effluent is added into the bottom of the cell and mixed with the adsorbent in the adsorption zone 1.1 where adsorption of the pollutants onto the surface of the adsorbent occurs. Mixing between the adsorbent and the polluted effluent is promoted by air spargers at the base of the cell which also facilitate the migration of the adsorbent upwards and into the cell's sedimentation zone. | 7 | Physical Chemistry |
Homeobox protein NANOG (hNanog) is a transcriptional factor that helps embryonic stem cells (ESCs) maintain pluripotency by suppressing cell determination factors. hNanog is encoded in humans by the NANOG gene. Several types of cancer are associated with NANOG. | 1 | Biochemistry |
Selenium yeast is a feed additive for livestock, used to increase the selenium content in their fodder. It is a form of selenium currently approved for human consumption in the EU and Britain. Inorganic forms of selenium are used in feeds (namely sodium selenate and sodium selenite, which appear to work in roughly the same manner). Since these products can be patented, producers can demand premium prices. It is produced by fermenting Saccharomyces cerevisiae (baker's yeast) in a selenium-rich media.
There is considerable variability in products described as Se-yeast and the selenium compounds found within. Many manufacturers and products on the market are simply mixtures of largely inorganic selenium and some yeast. Selenium is found in different forms based upon the food in which it is found. For instance, the form found in mustard and garlic is different from the form found in wheat or corn. In some products, the added selenium is structurally substituted for sulfur in the amino acid methionine, thus forming an organic chemical called selenomethionine via the same pathways and enzymes. Owing to its similarity to sulfur-containing methionine, selenomethionine is mistaken for an amino acid by the yeast anabolism and incorporated in its proteins. It has been claimed that selenomethionine makes a better source of dietary selenium in animal nutrition, since it is an organic chemical compound sometimes found in some common crops such as wheat. | 1 | Biochemistry |
It was first shown by Faraday that optical activity (the Faraday effect) could be induced in matter by a longitudinal magnetic field (a field in the direction of light propagation). The development of MCD really began in the 1930s when a quantum mechanical theory of MOR (magnetic optical rotatory dispersion) in regions outside absorption bands was formulated. The expansion of the theory to include MCD and MOR effects in the region of absorptions, which were referred to as "anomalous dispersions" was developed soon thereafter. There was, however, little effort made to refine MCD as a modern spectroscopic technique until the early 1960s. Since that time there have been numerous studies of MCD spectra for a very large variety of samples, including stable molecules in solutions, in isotropic solids, and in the gas phase, as well as unstable molecules entrapped in noble gas matrices. More recently, MCD has found useful application in the study of biologically important systems including metalloenzymes and proteins containing metal centers. | 7 | Physical Chemistry |
Tantalum anodizes similarly to titanium and niobium with a range of attractive colours being formed by interference at different film thicknesses. Again the film thickness is dependent on the anodizing voltage and typically ranges from 18 to 23 Angstroms per volt depending on electrolyte and temperature. Uses include tantalum capacitors. | 8 | Metallurgy |
The partial molar volume is broadly understood as the contribution that a component of a mixture makes to the overall volume of the solution. However, there is more to it than this:
When one mole of water is added to a large volume of water at 25 °C, the volume increases by 18 cm. The molar volume of pure water would thus be reported as 18 cm mol. However, addition of one mole of water to a large volume of pure ethanol results in an increase in volume of only 14 cm. The reason that the increase is different is that the volume occupied by a given number of water molecules depends upon the identity of the surrounding molecules. The value 14 cm is said to be the partial molar volume of water in ethanol.
In general, the partial molar volume of a substance X in a mixture is the change in volume per mole of X added to the mixture.
The partial molar volumes of the components of a mixture vary with the composition of the mixture, because the environment of the molecules in the mixture changes with the composition. It is the changing molecular environment (and the consequent alteration of the interactions between molecules) that results in the thermodynamic properties of a mixture changing as its composition is altered.
If, by , one denotes a generic extensive property of a mixture, it will always be true that it depends on the pressure (), temperature (), and the amount of each component of the mixture (measured in moles, n). For a mixture with q components, this is expressed as
Now if temperature T and pressure P are held constant, is a homogeneous function of degree 1, since doubling the quantities of each component in the mixture will double . More generally, for any :
By Euler's first theorem for homogeneous functions, this implies
where is the partial molar of component defined as:
By Euler's second theorem for homogeneous functions, is a homogeneous function of degree 0 (i.e., is an intensive property) which means that for any :
In particular, taking where , one has
where is the concentration expressed as the mole fraction of component .
Since the molar fractions satisfy the relation
the x are not independent, and the partial molar property is a function of only mole fractions:
The partial molar property is thus an intensive property - it does not depend on the size of the system.
The partial volume is not the partial molar volume. | 7 | Physical Chemistry |
The post-termination complex formed by the end of the termination step consists of mRNA with the termination codon at the A-site, an uncharged tRNA in the P site, and the intact 70S ribosome. Ribosome recycling step is responsible for the disassembly of the post-termination ribosomal complex. Once the nascent protein is released in termination, Ribosome Recycling Factor and Elongation Factor G (EF-G) function to release mRNA and tRNAs from ribosomes and dissociate the 70S ribosome into the 30S and 50S subunits. IF3 then replaces the deacylated tRNA releasing the mRNA. All translational components are now free for additional rounds of translation.
Depending on the tRNA, IF1–IF3 may also perform recycling. | 1 | Biochemistry |
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, describes a collection of related techniques to separate proteins according to their electrophoretic mobility (a function of the molecular weight of a polypeptide chain) while in the denatured (unfolded) state. In most proteins, the binding of SDS to the polypeptide chain imparts an even distribution of charge per unit mass, thereby resulting in a fractionation by approximate size during electrophoresis.
SDS is a strong detergent agent used to denature native proteins to unfolded, individual polypeptides. When a protein mixture is heated to 100 °C in presence of SDS, the detergent wraps around the polypeptide backbone. In this process, the intrinsic charges of polypeptides becomes negligible when compared to the negative charges contributed by SDS. Thus polypeptides after treatment become rod-like structures possessing a uniform charge density, that is same net negative charge per unit length. The electrophoretic mobilities of these proteins will be a linear function of the logarithms of their molecular weights. | 1 | Biochemistry |
Laser diffraction analysis, also known as laser diffraction spectroscopy, is a technology that utilizes diffraction patterns of a laser beam passed through any object ranging from nanometers to millimeters in size to quickly measure geometrical dimensions of a particle. This particle size analysis process does not depend on volumetric flow rate, the amount of particles that passes through a surface over time. | 7 | Physical Chemistry |
Various chemistries can be considered when dealing with reversible solid oxide cells, which in turn can influence their operating conditions and overall efficiency. | 7 | Physical Chemistry |
The 6-phosphogluconic acid is converted to 2-keto-3-deoxy-6-phosphogluconate (KDPG) in the presence of enzyme 6-phosphogluconate dehydratase; in the process, a water molecule is released to the surroundings. | 1 | Biochemistry |
Human cells require iron in order to obtain energy as ATP from a multi-step process known as cellular respiration, more specifically from oxidative phosphorylation at the mitochondrial cristae. Iron is present in the iron–sulfur cluster and heme groups of the electron transport chain proteins that generate a proton gradient that allows ATP synthase to synthesize ATP (chemiosmosis).
Heme groups are part of hemoglobin, a protein found in red blood cells that serves to transport oxygen from the lungs to other tissues. Heme groups are also present in myoglobin to store and diffuse oxygen in muscle cells. | 1 | Biochemistry |
Esters derived from carboxylic acids and alcohols are more polar than ethers but less polar than alcohols. They participate in hydrogen bonds as hydrogen-bond acceptors, but cannot act as hydrogen-bond donors, unlike their parent alcohols. This ability to participate in hydrogen bonding confers some water-solubility. Because of their lack of hydrogen-bond-donating ability, esters do not self-associate. Consequently, esters are more volatile than carboxylic acids of similar molecular weight. | 0 | Organic Chemistry |
The BCS formalism is applicable without modifications to the description of quark matter with color group SU(2), where Cooper pairs are colorless. The Nambu–Jona-Lasinio model
predicts the existence of the superconducting phase of SU(2) color quark matter at high densities
This physical picture is confirmed in the Polyakov–Nambu–Jona-Lasinio model,
and also in lattice QCD models
in which the properties of cold quark matter can be described based on the first principles of quantum chromodynamics.
The possibility of modeling on the lattices of two-color QCD at finite chemical potentials for even numbers of the quark flavors is associated with the positive-definiteness
of the integral measure and the absence of a sign problem. | 7 | Physical Chemistry |
Energy homeostasis is the homeostatic control of energy balance – the difference between energy obtained through food consumption and energy expenditure – in living systems. | 1 | Biochemistry |
The method developed by Bjerrum is still the main method in use today, though the precision of the measurements has greatly increased. Most commonly, a solution containing the metal ion and the ligand in a medium of high ionic strength is first acidified to the point where the ligand is fully protonated. This solution is then titrated, often by means of a computer-controlled auto-titrator, with a solution of CO-free base. The concentration, or activity, of the hydrogen ion is monitored by means of a glass electrode. The data set used for the calculation has three components: a statement defining the nature of the chemical species that will be present, called the model of the system, details concerning the concentrations of the reagents used in the titration, and finally the experimental measurements in the form of titre and pH (or emf) pairs.
Other ion-selective electrodes (ISE) may be used. For example, a fluoride electrode may be used with the determination of stability complexes of fluoro-complexes of a metal ion.
It is not always possible to use an ISE. If that is the case, the titration can be monitored by other types of measurement. Ultraviolet–visible spectroscopy, fluorescence spectroscopy and NMR spectroscopy are the most commonly used alternatives. Current practice is to take absorbance or fluorescence measurements at a range of wavelengths and to fit these data simultaneously. Various NMR chemical shifts can also be fitted together.
The chemical model will include values of the protonation constants of the ligand, which will have been determined in separate experiments, a value for log K and estimates of the unknown stability constants of the complexes formed. These estimates are necessary because the calculation uses a non-linear least-squares algorithm. The estimates are usually obtained by reference to a chemically similar system. The stability constant databases can be very useful in finding published stability constant values for related complexes.
In some simple cases the calculations can be done in a spreadsheet. Otherwise, the calculations are performed with the aid of a general-purpose computer programs. The most frequently used programs are:
* Potentiometric and/or spectrophotometric data: PSEQUAD
*Potentiometric data: [http://www.hyperquad.co.uk/HQ2013.htm HYPERQUAD], BEST, [http://jplusconsulting.com/products/reactlab-equilibria/ ReactLab pH PRO]
* Spectrophotometric data: [http://www.hyperquad.co.uk/HypSpec.htm HypSpec], SQUAD, SPECFIT, [http://jplusconsulting.com/products/reactlab-equilibria/ ReactLab EQUILIBRIA].
* NMR data [http://www.hyperquad.co.uk/hypnmr.htm HypNMR], [http://www.nuigalway.ie/chem/Mike/wineqnmr.htm WINEQNMR2]
In biochemistry, formation constants of adducts may be obtained from Isothermal titration calorimetry (ITC) measurements. This technique yields both the stability constant and the standard enthalpy change for the equilibrium. It is mostly limited, by availability of software, to complexes of 1:1 stoichiometry. | 7 | Physical Chemistry |
Stray light is unwanted wavelength radiation reaching the incorrect detector element. It generates erroneous electronic counts not related to designed spectral signal for the pixel or element of the detector array. It can come from light scatter and reflection of imperfect optical elements as well as higher order diffraction effects. The second order effect can be removed or at least dramatically reduced, by installing order sorting filters before the detector.
A Si detectors sensitivity to visible and NIR is nearly an order of magnitude larger than that in the UV range. This means that the pixels at the UV spectral position respond to stray light in visible and NIR much more strongly than to their own designed spectral signal. Therefore, the stray light impacts in UV region are much more significant as compared to visible and NIR pixels. This situation gets worse the shorter the wavelength.
When measuring broad band light with small fraction of UV signals, the stray light impact can sometimes be dominant in the UV range since the detector pixels are already struggling to get enough UV signals from the source. For this reason, calibration using QTH standard lamp can have huge errors (more than 100%) below 350 nm and Deuterium standard lamp is required for more accurate calibration in this region. In fact, absolute light measurement in the UV region can have large errors even with the correct calibration when majority of the electronic counts in these pixels is result of the stray light (longer wavelength strikes instead of the actual UV light). | 7 | Physical Chemistry |
Persistent carbenes tend to exist in the singlet, dimerizing when forced into triplet states. Nevertheless, Hideo Tomioka and associates used electron delocalization to produce a comparatively stable triplet carbene (bis(9-anthryl)carbene) in 2001. It has an unusually long half-life of 19 minutes.
Although the figure below shows the two parts of the molecule in one flat plane, molecular geometry puts the two aromatic parts in orthogonal positions with respect to each other.
In 2006 a triplet carbene was reported by the same group with a half-life of 40 minutes. This carbene is prepared by a photochemical decomposition of a diazomethane precursor by 300 nm light in benzene with expulsion of nitrogen gas.
Again the figure below is not an adequate representation of the actual molecular structure: both phenyl rings are positioned orthogonal with respect to each other. The carbene carbon has an sp-hybridisation, the two remaining orthogonal p-orbitals each conjugating with one of the aromatic rings.
Exposure to oxygen (a triplet diradical) converts this carbene to the corresponding benzophenone. The diphenylmethane compound is formed when it is trapped by cyclohexa-1,4-diene. As with the other carbenes, this species contains large bulky substituents, namely bromine and the trifluoromethyl groups on the phenyl rings, that shield the carbene and prevent or slow down the process of dimerization to a 1,1,2,2-tetra(phenyl)alkene. Based on computer simulations, the distance of the divalent carbon atom to its neighbors is claimed to be 138 picometers with a bond angle of 158.8°. The planes of the phenyl groups are almost at right angles to each other (the dihedral angle being 85.7°). | 0 | Organic Chemistry |
The purpose of single cell transcriptomics is to determine what genes are being expressed in each cell. The transcriptome is often used to quantify the gene expression instead of the proteome because of the difficulty currently associated with amplifying protein levels.
There are three major reasons gene expression has been studied using this technique: to study gene dynamics, RNA splicing, and cell typing. Gene dynamics are usually studied to determine what changes in gene expression affect different cell characteristics. For example, this type of transcriptomic analysis has often been used to study embryonic development. RNA splicing studies are focused on understanding the regulation of different transcript isoforms. Single cell transcriptomics has also been used for cell typing, where the genes expressed in a cell are used to identify types of cells. The main goal in cell typing is to find a way to determine the identity of cells that don't have known genetic markers.
RNA expression can serve as a proxy for protein abundance. However, protein abundance is governed by the complex interplay between RNA expression and post-transcriptional processes. While more challenging technically, translation can be monitored by ribosome profiling in single cells. | 1 | Biochemistry |
The phosphaethynolate anion, also referred to as PCO, is the phosphorus-containing analogue of the cyanate anion with the chemical formula or . The anion has a linear geometry and is commonly isolated as a salt. When used as a ligand, the phosphaethynolate anion is ambidentate in nature meaning it forms complexes by coordinating via either the phosphorus or oxygen atoms. This versatile character of the anion has allowed it to be incorporated into many transition metal and actinide complexes but now the focus of the research around phosphaethynolate has turned to utilising the anion as a synthetic building block to organophosphanes. | 7 | Physical Chemistry |
The hydrogen evolution reaction in alkaline conditions starts with water adsorption and dissociation in the Volmer step and either hydrogen desorption in the Tafel step or Heyrovsky step. | 7 | Physical Chemistry |
A vacuum Rabi oscillation is a damped oscillation of an initially excited atom coupled to an electromagnetic resonator or cavity in which the atom alternately emits photon(s) into a single-mode electromagnetic cavity and reabsorbs them. The atom interacts with a single-mode field confined to a limited volume V in an optical cavity. Spontaneous emission is a consequence of coupling between the atom and the vacuum fluctuations of the cavity field. | 7 | Physical Chemistry |
Hydrofluorocarbons (HFCs) contain no chlorine. They are composed entirely of carbon, hydrogen, and fluorine. They have no known effects on the ozone layer; fluorine itself is not ozone-toxic. However, HFCs and perfluorocarbons (PFCs) are greenhouse gases, which cause global warming. Two groups of haloalkanes, hydrofluorocarbons (HFCs) and perfluorocarbons, are targets of the Kyoto Protocol. Allan Thornton, President of the Environmental Investigation Agency, a non-governmental, environmental watchdog, says that HFCs are up to 12,500 times as potent as carbon dioxide in global warming. The higher global warming potential has two causes: HFCs remain in the atmosphere for long periods of time, and they have more chemical bonds than , which means that they are able to absorb more solar energy per molecule than carbon dioxide. Wealthy countries are clamping down on these gases. Thornton says that many countries are needlessly producing these chemicals just to get the carbon credits. Thus, as a result of carbon trading rules under the Kyoto Protocol, nearly half the credits from developing countries are from HFCs, with China scoring billions of dollars from catching and destroying HFCs that would be in the atmosphere as industrial byproducts. | 2 | Environmental Chemistry |
Intravenous magnesium sulphate is used in treating pre-eclampsia. For other than pregnancy-related hypertension, a meta-analysis of 22 clinical trials with dose ranges of 120 to 973 mg/day and a mean dose of 410 mg, concluded that magnesium supplementation had a small but statistically significant effect, lowering systolic blood pressure by 3–4 mm Hg and diastolic blood pressure by 2–3 mm Hg. The effect was larger when the dose was more than 370 mg/day. | 1 | Biochemistry |
In order to read a compressibility chart, the reduced pressure and temperature must be known. If either the reduced pressure or temperature is unknown, the reduced specific volume must be found. Unlike the reduced pressure and temperature, the reduced specific volume is not found by using the critical volume. The reduced specific volume is defined by,
where is the specific volume.
Once two of the three reduced properties are found, the compressibility chart can be used. In a compressibility chart, reduced pressure is on the x-axis and Z is on the y-axis. When given the reduced pressure and temperature, find the given pressure on the x-axis. From there, move up on the chart until the given reduced temperature is found. Z is found by looking where those two points intersect. the same process can be followed if reduced specific volume is given with either reduced pressure or temperature. | 7 | Physical Chemistry |
Most production, use, and emissions of HFC-152a have occurred within Earths more industrialized and populated northern hemisphere following the substances introduction in the 1990s. Its concentration in the northern troposphere reached an annual average of about 10 parts per trillion by year 2011. The concentration of HFC-152a in the southern troposphere is about 50% lower due to its removal rate (i.e. lifetime) of about 1.5 years being similar in magnitude to the global atmospheric mixing time of one to two years. | 2 | Environmental Chemistry |
Cholesteryl ester, a dietary lipid, is an ester of cholesterol. The ester bond is formed between the carboxylate group of a fatty acid and the hydroxyl group of cholesterol. Cholesteryl esters have a lower solubility in water due to their increased hydrophobicity. Esters are formed by replacing at least one –OH (hydroxyl) group with an –O–alkyl (alkoxy) group. They are hydrolyzed by pancreatic enzymes, cholesterol esterase, to produce cholesterol and free fatty acids. They are associated with atherosclerosis.
Cholesteryl ester is found in human brains as lipid droplets which store and transport cholesterol. Increased levels of cholesteryl ester have been found in certain parts of the brain of people with Huntington disease. Higher concentrations of cholesteryl ester have been found in the caudate and putamen, but not the cerebellum, of people with Huntington disease compared with levels in controls. Increase in cholesteryl ester has also been found in other neurological disorders like multiple sclerosis and Alzheimer's disease. | 1 | Biochemistry |
Pseudoenzymes are variants of enzymes (usually proteins) that are catalytically-deficient (usually inactive), meaning that they perform little or no enzyme catalysis. They are believed to be represented in all major enzyme families in the kingdoms of life, where they have important signaling and metabolic functions, many of which are only now coming to light. Pseudoenzymes are becoming increasingly important to analyse, especially as the bioinformatic analysis of genomes reveals their ubiquity. Their important regulatory and sometimes disease-associated functions in metabolic and signalling pathways are also shedding new light on the non-catalytic functions of active enzymes, of moonlighting proteins, the re-purposing of proteins in distinct cellular roles (Protein moonlighting). They are also suggesting new ways to target and interpret cellular signalling mechanisms using small molecules and drugs. The most intensively analyzed, and certainly the best understood pseudoenzymes in terms of cellular signalling functions are probably the pseudokinases, the pseudoproteases and the pseudophosphatases. Recently, the pseudo-deubiquitylases have also begun to gain prominence. | 1 | Biochemistry |
The third edition of the Green Book () was first published by IUPAC in 2007. A second printing of the third edition was released in 2008; this printing made several minor revisions to the 2007 text. A third printing of the third edition was released in 2011. The text of the third printing is identical to that of the second printing.
A Japanese translation of the third edition of the Green Book () was published in 2009. A French translation of the third edition of the Green Book () was published in 2012. A [http://www.sbq.org.br/livroverde/ Portuguese translation] (Brazilian Portuguese and European Portuguese) of the third edition of the Green Book () was published in 2018, with updated values of the physical constants and atomic weights; it is referred to as the "Livro Verde".
A concise four-page summary of the most important material in the Green Book was published in the July–August 2011 issue of Chemistry International, the IUPAC news magazine.
The second edition of the Green Book () was first published in 1993. It was reprinted in 1995, 1996, and 1998.
The Green Book is a direct successor of the Manual of Symbols and Terminology for Physicochemical Quantities and Units, originally prepared for publication on behalf of IUPACs Physical Chemistry Division by M. L. McGlashen in 1969. A full history of the Green Books various editions is provided in the historical introduction to the third edition.
The second edition and the third edition (second printing) of the Green Book have both been made available online as PDF files; the PDF version of the third edition is fully searchable. The four-page concise summary is also available online as a PDF file. External Links (below). | 3 | Analytical Chemistry |
Only small amount of SNPs in the human genome may have impact on human diseases. Large scale GWAS has been done for the most important human diseases, including heart diseases, metabolic diseases, autoimmune diseases, and neurodegenerative and psychiatric disorders. Most of the SNPs with relatively large effects on these diseases have been identified. These findings have significantly improved understanding of disease pathogenesis and molecular pathways, and facilitated development of better treatment. Further GWAS with larger samples size will reveal the SNPs with relatively small effect on diseases. For common and complex diseases, such as type-2 diabetes, rheumatoid arthritis, and Alzheimer's disease, multiple genetic factors are involved in disease etiology. In addition, gene-gene interaction and gene-environment interaction also play an important role in disease initiation and progression. | 1 | Biochemistry |
The first and most important of the complementary organizations to link with Fulmer was Yarsley, whose expertise was particularly strong in plastics and polymers and their applications. The Yarsley organization was founded by Dr Victor Yarsley a pioneer expert in plastics and an entrepreneur. Before the Second World War he had been a consultant in this new field and, starting in 1941 he had built a series of laboratories, mostly by converting and extending domestic premises, just as in the case of Fulmer. By 1970 his group consisted of Yarsley Research Laboratories (YRL) at Chessington, Surrey and Yarsley Testing Laboratories (YTL) at Ashtead, Surrey. A collaboration agreement was signed in 1970 and in 1973 Fulmer purchased Yarsley. By early 1974, most of the Chessington activities had been moved to another new building on the Stoke Poges site and the others to Ashtead.
Also in 1973 Fulmer purchased the engineering activities of Aeon Laboratories, Englefield Green, Surrey. Aeon's engineering work focussed on the manufacture of ancillary equipment for electron microscopes and for computers.
In 1975 Fulmer strengthened Yarsleys plastics processing capability by acquiring IPEC (Independent Plastics Engineering Centre) of Newhaven, Sussex. The Newhaven activities were combined with Yarsleys own plastics processing operation to form a new company: Yarsley Polymer Engineering Centre (YPEC).
In 1977 a new site was acquired at Redhill, Surrey to accommodate YPEC and the Yarsley research and testing facilities. This involved progressively transferring all the staff and equipment from Newhaven and Ashtead and the polymer facilities from Stoke Poges. A new company Yarsley Technical Centre Limited (YTEC) was set up to embrace all the activities carried out by YRL, YTL and YPEC.
In 1982 Fulmer established Fulmer Research & Development (Singapore) Pte Ltd, a joint venture with the Singapore-based company Chemical Laboratories Pte Ltd. The joint venture offered metallurgical and polymer-based technical services.
A second overseas company Fulmer Research (SA) Pty Ltd was set up in Johannesburg, South Africa in 1985. This was not successful and was closed after a few years. | 8 | Metallurgy |
Dendrimers have been prepared via click chemistry, employing Diels-Alder reactions, thiol-ene and thiol-yne reactions and azide-alkyne reactions.
There are ample avenues that can be opened by exploring this chemistry in dendrimer synthesis. | 6 | Supramolecular Chemistry |
N-Heterocyclic carbenes (NHCs) are particularly common carbene ligands. They are popular because they are more readily prepared than Schrock and Fischer carbenes. In fact, many NHCs are isolated as the free ligand, since they are persistent carbenes. Being strongly stabilized by π-donating substituents, NHCs are powerful σ-donors but π-bonding with the metal is weak. For this reason, the bond between the carbon and the metal center is often represented by a single dative bond, whereas Fischer and Schrock carbenes are usually depicted with double bonds to metal. Continuing with this analogy, NHCs are often compared with trialkylphosphine ligands. Like phosphines, NHCs serve as spectator ligands that influence catalysis through a combination of electronic and steric effects, but they do not directly bind substrates. | 0 | Organic Chemistry |
On September 3, 1992, Man died of lung cancer in her home in West Hartford, Connecticut. Man was 87 years old at the time of her death. | 1 | Biochemistry |
Brand names of flutamide include or have included Cebatrol, Cytomid, Drogenil, Etaconil, Eulexin, Flucinom, Flumid, Flutacan, Flutamid, Flutamida, Flutamin, Flutan, Flutaplex, Flutasin, Fugerel, Profamid, and Sebatrol, among others. | 4 | Stereochemistry |
RNA interference(RNAi) is a process that occurs naturally within the cytoplasm inhibiting gene expression at specific sequences. Regulation of gene expression through RNAi is possible by introducing small interfering RNAs(siRNAs), which effectively silence expression of a targeted gene. RNAi activates the RNA-induced silencing complex(RISC) containing siRNA, siRNA derived from cleaved dsRNA. The siRNA guides the RISC complex to a specific sequence on the mRNA that is cleaved by RISC and, consequently, silences those genes.
However, without modifications to the RNA backbone or inclusion of inverted bases at either end, siRNA instability in the plasma makes it extremely difficult to apply this technique in vivo. Pattern recognition receptors(PRRs), which can be grouped as endocytic PRRs or signaling PRRs, are expressed in all cells of the innate immune system. Signaling PRRs, in particular, include Toll-like receptors(TLRs) and are involved primarily with identifying pathogen-associated molecular patterns(PAMPs). For example, TLRs can recognize specific regions conserved in various pathogens, recognition stimulating an immune response with potentially devastating effects to the organism. In particular, TLR 3 recognizes both dsRNA characteristic of viral replication and siRNA, which is also double-stranded. In addition to this instability, another limitation of siRNA therapy concerns the inability to target a tissue with any specificity.
SNALPs, though, may provide the stability and specificity required for this mode of RNAi therapy to be effective. Consisting of a lipid bilayer, SNALPs are able to provide stability to siRNAs by protecting them from nucleases within the plasma that would degrade them. In addition, delivery of siRNAs is subject to endosomal trafficking, potentially exposing them to TLR3 and TLR7, and can lead to activation of interferons and proinflammatory cytokines. However, SNALPs allow siRNA uptake into the endosome without activating Toll-like receptors and consequently stimulating an impeding immune response, thus enabling siRNA escape from the endosome. | 1 | Biochemistry |
In 1987 Canada witnessed a crisis in the seafood industry. Shellfish toxins present in PEI mussels caused amnesic shellfish poisoning taking several lives. In response, shellfish toxin research was initiated at NRC Canada. Today, NRC remains the premier producer of biotoxin CRMs in the world and is recognized for its expertise.
* Amnesic shellfish poisoning toxins
** ASP-Mus-d, mussel tissue for domoic acid and its isomers
** DA-f, domoic acid standard
* Diarrhetic shellfish poisoning and other lipophilic toxins
** AZA, azaspiracid standards
** DSP-Mus, mussel tissue for okadaic acid
** OA, okadaic acid standard
** DTX, dinophysistoxin standards
** GYM, gymnodimine standards
** YTX and , yessotoxin standards
** PTX, pectenotoxin-2 standard
** SPX, 13-desmethyl spirolide C standard
* Microcystins
** and MCLR, microcystin-LR standards
** MCRR, microcystin-RR standard
** NODR, nodularin-R standard
* Paralytic shellfish poisoning toxins
** C1&2, N-sulfocarbamoyl-gonyautoxin standard
** and GTX, decarbamoyl-gonyautoxin and gonyautoxin standards
** and NEO, decarbamoyl-neosaxitoxin and neosaxitoxin standards
** and STX, decarbamoyl-saxitoxin and saxitoxin standards
* Cyanobacterial toxins
** ATX, anatoxin-a standard
** CYN, cylindrospermopsin standard | 1 | Biochemistry |
The discovery of this type of mechanism to control the expression of genes in a biosynthetic operon lead to its identification in a wide variety of such operons for which repressors had never been discovered. For example: | 1 | Biochemistry |
The words "paracrystallinity" and "paracrystal" were coined by the late Friedrich Rinne in the year 1933. Their German equivalents, e.g. "Parakristall", appeared in print one year earlier.
A general theory of paracrystals has been formulated in a basic textbook, and then further developed/refined by various authors.
Rolf Hosemann's definition of an ideal paracrystal is: "The electron density distribution of any material is equivalent to that of a paracrystal when there is for every building block one ideal point so that the distance statistics to other ideal points are identical for all of these points. The electron configuration of each building block around its ideal point is statistically independent of its counterpart in neighboring building blocks. A building block corresponds then to the material content of a cell of this "blurred" space lattice, which is to be considered a paracrystal." | 7 | Physical Chemistry |
The temperature of a body of water directly affects the amount of dissolved oxygen it can hold. Following Henry's law, as water becomes warmer, oxygen becomes less soluble in it. This property leads to daily anoxic cycles on small geographic scales and seasonal cycles of anoxia on larger scales. Thus, bodies of water are more vulnerable to anoxic conditions during the warmest period of the day and during summer months. This problem can be further exacerbated in the vicinity of industrial discharge where warm water used to cool machinery is less able to hold oxygen than the basin to which it is released.
Daily cycles are also influenced by the activity of photosynthetic organisms. The lack of photosynthesis during nighttime hours in the absence of light can result in anoxic conditions intensifying throughout the night with a maximum shortly after sunrise. | 9 | Geochemistry |
The touchdown polymerase chain reaction or touchdown style polymerase chain reaction is a method of polymerase chain reaction by which primers avoid amplifying nonspecific sequences. The annealing temperature during a polymerase chain reaction determines the specificity of primer annealing. The melting point of the primer sets the upper limit on annealing temperature. At temperatures just above this point, only very specific base pairing between the primer and the template will occur. At lower temperatures, the primers bind less specifically. Nonspecific primer binding obscures polymerase chain reaction results, as the nonspecific sequences to which primers anneal in early steps of amplification will "swamp out" any specific sequences because of the exponential nature of polymerase amplification. | 1 | Biochemistry |
Established in 1972, the focus of the research is on cryoinjury, cryosurgery, cryopreservation, lyophilization and hypothermia. Since 1985 the Institute has published the open access peer-reviewed scientific journal Problems of Cryobiology and Cryomedicine. | 1 | Biochemistry |
DNA footprinting is a method of investigating the sequence specificity of DNA-binding proteins in vitro. This technique can be used to study protein-DNA interactions both outside and within cells.
The regulation of transcription has been studied extensively, and yet there is still much that is unknown. Transcription factors and associated proteins that bind promoters, enhancers, or silencers to drive or repress transcription are fundamental to understanding the unique regulation of individual genes within the genome. Techniques like DNA footprinting help elucidate which proteins bind to these associated regions of DNA and unravel the complexities of transcriptional control. | 1 | Biochemistry |
Fougèrite is a relatively recently described naturally occurring green rust mineral. It is the archetype of the fougèrite group in the larger hydrotalcite supergroup of naturally occurring layered double hydroxides. The structure is based on brucite-like layers containing Fe and Fe cations, O and OH anions, with loosely bound [CO] groups and HO molecules between the layers. Fougèrite crystallizes in trigonal system. The ideal formula for fougèrite is [FeFe(OH)][CO]·3HO. Higher degrees of oxidation produce the other members of the fougèrite group, namely trébeurdenite, [FeFeO(OH)][CO]·3HO and mössbauerite, [FeO(OH)][CO]·3HO.
Fougèrite was first found in forested soils near Fougères, Brittany, France, and recognised as a valid mineral species by the International Mineralogical Association in 2002. It is blue-green to bluish-gray in colour, and resembles clay minerals in habit, forming hexagonal platelets of submicron diameter. In this environment, it is intimately intergrown with trébeurdenite, to give varying overall ratios of Fe:Fe. The existence of two intergrown fixed-composition phases has been demonstrated by Mössbauer spectroscopy. The mineral is unstable in air, and decomposes by oxidation, dehydration and decarbonation, to ferrihydrite, and ultimately to lepidocrocite or goethite, FeO(OH). | 8 | Metallurgy |
Direct application of mirror-chiral organisms can be mass production of enantiomers (mirror-image) of molecules produced by normal life.
*Enantiopure drugs - some pharmaceuticals have known different activity depending on enantiomeric form,
*Aptamers (-ribonucleic acid aptamers): "That makes mirror-image biochemistry a potentially lucrative business. One company that hopes so is Noxxon Pharma in Berlin. It uses laborious chemical synthesis to make mirror-image forms of short strands of DNA or RNA called aptamers, which bind to therapeutic targets such as proteins in the body to block their activity. The firm has several mirror-aptamer candidates in human trials for diseases including cancer; the idea is that their efficacy might be improved because they arent degraded by the bodys enzymes. A process to replicate mirror-image DNA could offer a much easier route to making the aptamers, says Sven Klussmann, Noxxon Pharma's chief scientific officer."
*L-Glucose, enantiomer of standard glucose, for which tests showed that it tastes likes standard sugar, but not being metabolized the same way. However, it was never marketed due to excessive manufacturing costs. More recent research allows cheap production with high yields, however the authors state that it is not usable as a sweetener due to laxative effects. | 4 | Stereochemistry |
The main role of potassium in plants is to provide the ionic environment for metabolic processes in the cytosol, and as such functions as a regulator of various processes including growth regulation. Plants require potassium ions (K) for protein synthesis and for the opening and closing of stomata, which is regulated by proton pumps to make surrounding guard cells either turgid or flaccid. A deficiency of potassium ions can impair a plant's ability to maintain these processes. Potassium also functions in other physiological processes such as photosynthesis, protein synthesis, activation of some enzymes, phloem solute transport of photoassimilates into source organs, and maintenance of cation:anion balance in the cytosol and vacuole. | 1 | Biochemistry |
Orbifold notation for wallpaper groups, advocated by John Horton Conway (Conway, 1992) (Conway 2008), is based not on crystallography, but on topology. One can fold the infinite periodic tiling of the plane into its essence, an orbifold, then describe that with a few symbols.
*A digit, n, indicates a centre of n-fold rotation corresponding to a cone point on the orbifold. By the crystallographic restriction theorem, n must be 2, 3, 4, or 6.
*An asterisk, *, indicates a mirror symmetry corresponding to a boundary of the orbifold. It interacts with the digits as follows:
*#Digits before * denote centres of pure rotation (cyclic).
*#Digits after * denote centres of rotation with mirrors through them, corresponding to "corners" on the boundary of the orbifold (dihedral).
*A cross, ×, occurs when a glide reflection is present and indicates a crosscap on the orbifold. Pure mirrors combine with lattice translation to produce glides, but those are already accounted for so need no notation.
*The "no symmetry" symbol, o, stands alone, and indicates there are only lattice translations with no other symmetry. The orbifold with this symbol is a torus; in general the symbol o denotes a handle on the orbifold.
The group denoted in crystallographic notation by cmm will, in Conway's notation, be 2*22. The 2 before the * says there is a 2-fold rotation centre with no mirror through it. The * itself says there is a mirror. The first 2 after the * says there is a 2-fold rotation centre on a mirror. The final 2 says there is an independent second 2-fold rotation centre on a mirror, one that is not a duplicate of the first one under symmetries.
The group denoted by pgg will be 22×. There are two pure 2-fold rotation centres, and a glide reflection axis. Contrast this with pmg, Conway 22*, where crystallographic notation mentions a glide, but one that is implicit in the other symmetries of the orbifold.
Coxeter's bracket notation is also included, based on reflectional Coxeter groups, and modified with plus superscripts accounting for rotations, improper rotations and translations. | 3 | Analytical Chemistry |
The Dulong–Petit law, a thermodynamic law proposed by French physicists Pierre Louis Dulong and Alexis Thérèse Petit, states that the classical expression for the molar specific heat capacity of certain chemical elements is constant for temperatures far from the absolute zero.
In modern terms, Dulong and Petit found that the heat capacity of a mole of many solid elements is about 3R, where R is the universal gas constant. The modern theory of the heat capacity of solids states that it is due to lattice vibrations in the solid. | 3 | Analytical Chemistry |
*In the United States, the CDC first tested samples from the general population for lead and a few pesticides in 1976. In the late 1990s, the National Health and Nutrition Examination Survey (NHANES) program had a major expansion.
*National Report on Human Exposure to Environmental Chemicals
The CDCs Division of Laboratory Sciences within the National Center for Environmental Health has developed a National Biomonitoring Program, and has published the biennial National Report on Human Exposure to Environmental Chemicals' since 2001. As the selection of chemicals is controversial, the CDC has identified influential criteria:Evidence of exposure in a U.S. population, presence and significance of health effects after a given level of exposure, desire to track public health initiatives to reduce exposure to a given agent, existing method for accurately measuring biologically relevant concentrations of the chemical, sufficient tissue specimens, in particular, blood and/or urine samples and cost-effectiveness.
CDC established three criteria for removing chemicals from future surveys: a new replacement chemical (i.e., a metabolite or other chemical) is more representative of exposure than the chemical currently measured, or if after three survey periods, detection rates for all chemicals within a method-related group are less than 5 percent for all population subgroups (i.e., two sexes, three race/ethnicity groups, and the age groups used in the National Report), or if after three survey periods, levels of chemicals within a method-related group are unchanged or declining in all demographic subgroups documented in the National Report.
* The National Childrens Study plans to follow 100,000 children across the United States from birth until age 21. The study was authorized as part of the Childrens Health Act of 2000 as the largest effort undertaken to address the effects of social, economic and environmental factors on a childs health. the CDCs Environmental Health Laboratory announced in 2009 it would play a key role in the biomonitoring of the ongoing National Children's Study. In collaboration with the National Institute of Child Health and Development, National Institute of Environmental Health Sciences and U.S. Environmental Protection Agency.
*Some U.S. states have received federal support and established biomonitoring programs. In 2001, the CDC awarded planning grants to 33 states to assist in capacity building for expanding biomonitoring.
**The California Environmental Contaminant Biomonitoring Program (CECBP) was established by law in 2006 and is administered by the California Department of Public Health.
**Minnesota's Biomonitoring Pilot Program was established by law in 2007 and is run by the Minnesota Department of Health. | 2 | Environmental Chemistry |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.