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Chemical mimicry of an organism's pheromones allows predators with this ability to draw select prey to them, rather than spend their energy finding and attempting to capture these organisms with varied success. The pheromones are typically used by the prey species to attract members of their own species as potential mates. In the case of predatory chemical mimicry, the predator has evolved to emit chemicals that are structurally similar and will cause the same behavioural reactions to be displayed by the prey. However, the mimicked pheromones will draw the animal toward the predator rather than a potential mate.
One group of organisms that use this method are Bolas spiders (genus: Mastophora). Bolas spiders emit chemicals that attract their prey, noctuid moths. These spiders have replaced the need to spin elaborate webs to capture prey by mimicking the pheromones emitted by female moths to attract males of the species effectively. In studies conducted on this spider it has been found that the moths only approach from downwind of the spider and that all of the moths captured were, in fact, male. | 1 | Applied and Interdisciplinary Chemistry |
A common way to produce the 3-azidocoumarin is by condensation of salicylaldehyde and N-acetylglycine or nitroacetate. The intermediate is trapped with sodium azide to produce the 3-azidocoumarin. The isomeric 4-azidocoumarin (CAS# 42373-56-8) product can also be prepared from 4-hydroxycoumarin via the 4-chloro derivative, which reacts with sodium azide. | 1 | Applied and Interdisciplinary Chemistry |
Performance requirements can include:
#Optical performance (image quality): This is quantified by various metrics, including encircled energy, modulation transfer function, Strehl ratio, ghost reflection control, and pupil performance (size, location and aberration control); the choice of the image quality metric is application specific.
#Physical requirements such as weight, static volume, dynamic volume, center of gravity and overall configuration requirements.
#Environmental requirements: ranges for temperature, pressure, vibration and electromagnetic shielding.
Design constraints can include realistic lens element center and edge thicknesses, minimum and maximum air-spaces between lenses, maximum constraints on entrance and exit angles, physically realizable glass index of refraction and dispersion properties.
Manufacturing costs and delivery schedules are also a major part of optical design. The price of an optical glass blank of given dimensions can vary by a factor of fifty or more, depending on the size, glass type, index homogeneity quality, and availability, with BK7 usually being the cheapest. Costs for larger and/or thicker optical blanks of a given material, above 100–150 mm, usually increase faster than the physical volume due to increased blank annealing time required to achieve acceptable index homogeneity and internal stress birefringence levels throughout the blank volume. Availability of glass blanks is driven by how frequently a particular glass type is made by a given manufacturer, and can seriously affect manufacturing cost and schedule. | 0 | Theoretical and Fundamental Chemistry |
In a stripping reaction, the metal strips a neutron from accelerated deuteron and fuses it with the metal, yielding a different isotope of the metal. If the produced metal isotope is radioactive, it may decay into another element, releasing energy in the form of ionizing radiation in the process. | 0 | Theoretical and Fundamental Chemistry |
2,2-Dimethylpropanoyl chloride is a branched-chain acyl chloride. It was first made by Aleksandr Butlerov in 1874 by reacting pivalic acid with phosphorus pentachloride.
Pivaloyl chloride is used as an input in the manufacture of some drugs, insecticides and herbicides. | 0 | Theoretical and Fundamental Chemistry |
Following the 120 kg/h test work, MIM decided to proceed to install a 5 t/h lead ISASMELT pilot plant in its Mount Isa lead smelter. It bought Aberfoyle's matte fuming furnace and transported it from Kalgoorlie to Mount Isa, where it was rebuilt and commissioned in 1983 to demonstrate the first stage of the process in continuous operation and for testing the reduction step using batches of high-lead slag.
One of the key features of the pilot plant was that it was run by operations’ personnel in the lead smelter as though it was an operations’ plant. The high lead slag produced by the continuous smelting of the lead concentrate was subsequently treated in the sinter plant, thus increasing the production of the lead smelter by up to 17%. This gave the operations’ people ownership of the plant and an incentive to make it work, thus ensuring management and maintenance priority. It also gave MIM assurance that the process simple enough to be operable in a production environment, with normal staff and supervision, and that it was robust enough to withstand normal control excursions. In addition to the continuous operation of lead concentrate to produce high-lead slag, the pilot plant was used to produce lead metal from batches of the slag, investigate the wear rates of the furnace's refractory lining and lances, and initial work aimed at developing a low-pressure version of the Sirosmelt lance. The result was a lance design that allowed operation at significantly lower pressure than the initial values of about 250 kilopascal (gauge) ("kPag"), thus reducing operating costs.
MIM built a second, identical furnace next to the first, and commissioned it in August 1985. This combination of furnaces was used to demonstrate the two-stage process in continuous operation in mid-1987. However, for most of the time the two furnaces were not able to operate simultaneously due to a constraint in the capacity of the baghouse used to filter the lead dust from the waste gas.
A series of process improvements, particularly in the waste gas handling system, resulted in increasing the throughput of the plant from the initial design of 5 t/h to 10 t/h. The pilot plant had treated more than 125,000 t of lead concentrate by April 1989.
The two furnaces were also used to develop a process to recover lead from the Mount Isa lead smelter's drossing operations. | 1 | Applied and Interdisciplinary Chemistry |
The PKS of phoslactomycin has one loading domain, 7 modules and 6 proteins that encode PnA, PnB, PnC, PnD, PnE, and PnF. The biosynthesis starts the loading with the cyclohexyl- CoA. Stepping in each module, there always need the keto synthase (KS) to create the new linkage of carbon-carbon to elongate the chain, the acyl transferase to transfer acyl to ACP domain. Then ACP serves as the acyl carrier protein to the further reaction, and each module has the keto reductase at the end to reduce the ketone to hydroxyl group with more stable. Module 1 uses the precursor malonyl-CoA and dehydrase domain to create the double bond.
Similarly, module 2, module 5, and module 7 have the same 5 domains KS-AT-ACP-DH-KR, but module 7 has one more domain at the end is thioesterase (TE) to create the ring member of the phoslactomycin product. Module 4 and module 6 have 4 domains which are KS-AT-ACP-KR and use the precursor ethylmalonyl-CoA. The final product is phoslactomycin.
<br /> | 1 | Applied and Interdisciplinary Chemistry |
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. | 0 | Theoretical and Fundamental Chemistry |
An effusive limit in ultra-low pressure fluid flow is the limit at which a gas of certain molecular weight is able to expand into a vacuum such as a molecular beam line. | 1 | Applied and Interdisciplinary Chemistry |
An active moiety is a molecule or ion, excluding those appended portions of the molecule that cause the drug to be an ester, salt (including a salt with hydrogen or coordination bonds), or other noncovalent derivative (such as a complex, chelate, or clathrate) of the molecule, responsible for the physiological or pharmacological action of the drug substance.
An NCE is a molecule developed by the innovator company in the early drug discovery stage, which after undergoing clinical trials could translate into a drug that could be a treatment for some disease. Synthesis of an NCE is the first step in the process of drug development. Once the synthesis of the NCE has been completed, companies have two options before them. They can either go for clinical trials on their own or license the NCE to another company. In the latter option, companies can avoid the expensive and lengthy process of clinical trials, as the licensee company would be conducting further clinical trials and subsequently launching the drug. Companies adopting this model of business would be able to generate high margins as they get a huge one-time payment for the NCE as well as entering into a revenue sharing agreement with the licensee company.
Under the Food and Drug Administration Amendments Act of 2007, all new chemical entities must first be reviewed by an advisory committee before the FDA can approve these products. | 1 | Applied and Interdisciplinary Chemistry |
The principal reaction of interest involves the addition of the acetylene () to a ketone () or aldehyde ():
The reaction proceeds with retention of the triple bond. For aldehydes and unsymmetrical ketones, the product is chiral, hence there is interest in asymmetric variants. These reactions invariably involve metal-acetylide intermediates.
This reaction was discovered by chemist John Ulric Nef in 1899 while experimenting with reactions of elemental sodium, phenylacetylene, and acetophenone. For this reason, the reaction is sometimes referred to as Nef synthesis. Sometimes this reaction is erroneously called the Nef reaction, a name more often used to describe a different reaction (see Nef reaction). Chemist Walter Reppe coined the term ethynylation during his work with acetylene and carbonyl compounds.
In the following reaction (scheme 1), the alkyne proton of ethyl propiolate is deprotonated by n-butyllithium at -78 °C to form lithium ethyl propiolate to which cyclopentanone is added forming a lithium alkoxide. Acetic acid is added to remove lithium and liberate the free alcohol. | 0 | Theoretical and Fundamental Chemistry |
Methylthioninium chloride, commonly called methylene blue, is a salt used as a dye and as a medication. As a medication, it is mainly used to treat methemoglobinemia by chemically reducing the ferric iron in hemoglobin to ferrous iron. Specifically, it is used to treat methemoglobin levels that are greater than 30% or in which there are symptoms despite oxygen therapy. It has previously been used for treating cyanide poisoning and urinary tract infections, but this use is no longer recommended.
Methylene blue is typically given by injection into a vein. Common side effects include headache and vomiting. While use during pregnancy may harm the baby, not using it in methemoglobinemia is likely more dangerous.
Methylene blue was first prepared in 1876, by Heinrich Caro. It is on the World Health Organization's List of Essential Medicines. | 0 | Theoretical and Fundamental Chemistry |
N-heterocyclic carbenes (NHCs) have become one of the most important ligands in transition-metal catalysis. The success of normal NHCs is greatly attributed to their superior σ-donating capabilities as compared to phosphines, which is even greater in abnormal NHC counterparts. Employed as ligands in palladium complexes, NHCs contributed greatly to the stabilization and activation of precatalysts and have therefore found application in many areas of organometallic homogeneous catalysis, including Sonogashira couplings.
Interesting examples of abnormal NHCs are based on the mesoionic 1,2,3-triazol-5-ylidene structure.
An efficient, cationic palladium catalyst of PEPPSI type, i.e., iPEPPSI (internal pyridine-enhanced precatalyst preparation stabilization and initiation) was demonstrated to efficiently catalyse the copper-free Sonogashira reaction in water as the only solvent, under aerobic conditions, in the absence of copper, amines, phosphines and other additives. | 0 | Theoretical and Fundamental Chemistry |
LC–MS is frequently used in drug development because it allows quick molecular weight confirmation and structure identification. These features speed up the process of generating, testing, and validating a discovery starting from a vast array of products with potential application. LC–MS applications for drug development are highly automated methods used for peptide mapping, glycoprotein mapping, lipodomics, natural products dereplication, bioaffinity screening, in vivo drug screening, metabolic stability screening, metabolite identification, impurity identification, quantitative bioanalysis, and quality control. | 0 | Theoretical and Fundamental Chemistry |
The immune system plays an important role in monitoring and destroying abnormal or cancerous cells. Telomere extension may affect the immune system's ability to recognize and eliminate cells with long telomeres, potentially compromising immune surveillance. It is very important to ensure the ability of the immune system to effectively identify and fight against pathogens and abnormal cells. | 1 | Applied and Interdisciplinary Chemistry |
To a large extent, portions of nucleotide repeats are quite often observed as part of rare DNA combinations. The three main repeats which are largely found in particular DNA constructs include the closely precise homopurine-homopyrimidine inverted repeats, which is otherwise referred to as H palindromes, a common occurrence in triple helical H conformations that may comprise either the TAT or CGC nucleotide triads. The others could be described as long inverted repeats having the tendency to produce hairpins and cruciform, and finally direct tandem repeats, which commonly exist in structures described as slipped-loop, cruciform and left-handed Z-DNA. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a staggered conformation is a chemical conformation of an ethane-like moiety abcX–Ydef in which the substituents a, b, and c are at the maximum distance from d, e, and f; this requires the torsion angles to be 60°. It is the opposite of an eclipsed conformation, in which those substituents are as close to each other as possible.
Such a conformation exists in any open chain single chemical bond connecting two sp-hybridised atoms, and is normally a conformational energy minimum. For some molecules such as those of n-butane, there can be special versions of staggered conformations called gauche and anti; see first Newman projection diagram in Conformational isomerism.
Staggered/eclipsed configurations also distinguish different crystalline structures of e.g. cubic/hexagonal boron nitride, and diamond/lonsdaleite. | 0 | Theoretical and Fundamental Chemistry |
In two tandem Letters to the Editor (1936), Wrinch and Frank addressed the question of whether the cyclol form of the peptide group was indeed more stable than the amide form. A relatively simple calculation showed that the cyclol form is significantly less stable than the amide form. Therefore, the cyclol model would have to be abandoned unless a compensating source of energy could be identified. Initially, Frank proposed that the cyclol form might be stabilized by better interactions with the surrounding solvent; later, Wrinch and Irving Langmuir hypothesized that hydrophobic association of nonpolar sidechains provides stabilizing energy to overcome the energetic cost of the cyclol reactions.
The lability of the cyclol bond was seen as an advantage of the model, since it provided a natural explanation for the properties of denaturation; reversion of cyclol bonds to their more stable amide form would open up the structure and allows those bonds to be attacked by proteases, consistent with experiment. Early studies showed that proteins denatured by pressure are often in a different state than the same proteins denatured by high temperature, which was interpreted as possibly supporting the cyclol model of denaturation.
The Langmuir-Wrinch hypothesis of hydrophobic stabilization shared in the downfall of the cyclol model, owing mainly to the influence of Linus Pauling, who favored the hypothesis that protein structure was stabilized by hydrogen bonds. Another twenty years had to pass before hydrophobic interactions were recognized as the chief driving force in protein folding. | 1 | Applied and Interdisciplinary Chemistry |
Usual Rankine cycles are thermodynamic cycles that employ water as a working fluid to produce electric power from thermal sources. In Organic Rankine cycles, by contrast, water is substituted by molecularly complex organic compounds. Since the vaporization temperature of these kinds of fluids is lower than that of water at atmospheric pressure, low-to-medium temperature sources can be exploited allowing for heat recovery, for example, from biomass combustion, industrial waste heat, or geothermal heat. For these reasons, ORC technology belongs to the class of renewable energies.
For the design of mechanical components, such as turbines, working in ORC plants, it is fundamental to take into account typical non-ideal gas-dynamic phenomena. In fact, the single-phase vapor at the inlet of an ORC turbine stator usually evolves in the non-ideal thermodynamic region close to the liquid-vapor saturation curve and critical point. Moreover, due to the high molecular mass of the complex organic compounds employed, the speed of sound in these fluids is low compared to that of air and other simple gases. Therefore, turbine stators are very likely to involve supersonic flows even if rather low flow velocities are reached. High supersonic flows can produce large losses and mechanical stresses in the turbine blades due to the occurrence of shock waves, which cause a strong pressure raise. However, when working fluids of the BZT class are employed, expander performances could be improved by exploiting some non-classical phenomena. | 0 | Theoretical and Fundamental Chemistry |
Nitrogen fixation is a chemical process by which molecular nitrogen (), which has a strong triple covalent bond, is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N) gas to ammonia (NH) using the nitrogenase protein complex (Nif).
Nitrogen fixation is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds, such as amino acids and proteins, nucleoside triphosphates and nucleic acids. As part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all nitrogen chemical compounds, which include some explosives, pharmaceuticals, and dyes.
Nitrogen fixation is carried out naturally in soil by microorganisms termed diazotrophs that include bacteria, such as Azotobacter and Rhizobia, and archaea. Some nitrogen-fixing bacteria have symbiotic relationships with plant groups, especially legumes. Looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. Nitrogen fixation occurs between some termites and fungi. It occurs naturally in the air by means of NO production by lightning.
All biological reactions involving the process of nitrogen fixation are catalyzed by enzymes called nitrogenases. These enzymes contain iron, often with a second metal, usually molybdenum but sometimes vanadium. | 1 | Applied and Interdisciplinary Chemistry |
Modular screen media is typically 1 foot large by 1 or 2 feet long (4 feet long for ISEPREN WS 85 ) steel reinforced polyurethane or rubber panels. They are installed on a flat deck (no crown) that normally has a larger surface than a tensioned deck. This larger surface design compensates for the fact that rubber and polyurethane modular screen media offers less open area than wire cloth. Over the years, numerous ways have been developed to attach modular panels to the screen deck stringers (girders). Some of these attachment systems have been or are currently patented. Self-cleaning screen media is also available on this modular system.
<br /> | 1 | Applied and Interdisciplinary Chemistry |
An example of a transversely isotropic material is the so-called on-axis unidirectional fiber composite lamina where the fibers are circular in cross section. In a unidirectional composite, the plane normal to the fiber direction can be considered as the isotropic plane, at long wavelengths (low frequencies) of excitation. In the figure to the right, the fibers would be aligned with the axis, which is normal to the plane of isotropy.
In terms of effective properties, geological layers of rocks are often interpreted as being transversely isotropic. Calculating the effective elastic properties of such layers in petrology has been coined Backus upscaling, which is described below. | 0 | Theoretical and Fundamental Chemistry |
Most low-beam headlamps produce an asymmetrical light suitable for use on only one side of the road. Low beam headlamps in LHT jurisdictions throw most of their light forward-leftward; those for RHT throw most of their light forward-rightward, thus illuminating obstacles and road signs while minimising glare for oncoming traffic.
In Europe, headlamps approved for use on one side of the road must be adaptable to produce adequate illumination with controlled glare for temporarily driving on the other side of the road,. This may be achieved by affixing masking strips or prismatic lenses to a part of the lens or by moving all or part of the headlamp optic so all or part of the beam is shifted or the asymmetrical portion is occluded. Some varieties of the projector-type headlamp can be fully adjusted to produce a proper LHT or RHT beam by shifting a lever or other movable element in or on the lamp assembly. Some vehicles adjust the headlamps automatically when the car's GPS detects that the vehicle has moved from LHT to RHT and vice versa. | 0 | Theoretical and Fundamental Chemistry |
Pyruvate kinase catalyzes the last step within the glycolytic sequence, the dephosphorylation of phosphoenolpyruvate to pyruvate and is responsible for net energy production within the glycolytic pathway. Depending upon the different metabolic functions of the tissues, different isoenzymes of pyruvate kinase are expressed.
M2-PK (PKM2) is the predominant pyruvate kinase isoform in proliferating cells, such as fibroblasts, embryonic cells and adult stem cells and most human tissue, including lung, bladder, kidney and thymus; M2-PK is upgregulated in many human tumors.
M2-PK can occur in two different forms in proliferating cells:
* a tetrameric form, which consists of four subunits
* a dimeric form, consisting of two subunits.
The tetrameric form of M2-PK has a high affinity to its substrate, phosphoenolpyruvate (PEP), and is highly active at physiological PEP concentrations. Furthermore, the tetrameric form of M2-PK is associated with several other glycolytic enzymes within the so-called glycolytic enzyme complex. Due to the close proximity of the enzymes, the association within the glycolytic enzyme complex leads to a highly effective conversion of glucose to lactate.
When M2-PK is mainly in the highly active tetrameric form, which is the case in most normal cells, glucose is mostly converted to lactate, with the attendant production of energy.
In contrast, the dimeric form of M2-PK has a low affinity for phosphoenolpyruvate, being nearly inactive at physiological PEP concentrations. When M2-PK is mainly in the dimeric form, which is the case in tumor cells, all phosphometabolites above pyruvate kinase accumulate and are channelled into synthetic processes which branch off from glycolytic intermediates, such as nucleic acids, phospholipids and amino acids, important cell building blocks for highly proliferating cells such as tumor cells.
As a consequence of the key position of pyruvate kinase within glycolysis, the tetramer : dimer ratio of M2-PK determines whether glucose carbons are converted to pyruvate and lactate, along with the production of energy (tetrameric form), or channelled into synthetic processes (dimeric form). In tumor cells M2-PK is mainly in the dimeric form. Therefore, the dimeric form of M2-PK has been termed Tumor M2-PK.
The dimerization of M2-PK in tumor cells is induced by the direct interaction of M2-PK with different oncoproteins.
However, the tetramer : dimer ratio of M2-PK is not constant.
Oxygen starvation or highly accumulated glycolytic intermediates, such as fructose 1,6-bisphosphate (fructose 1,6-P2) or the amino acid serine, induce the reassociation of the dimeric form of M2-PK to the tetrameric form. Consequently, due to the activation of M2-PK, glucose is converted to pyruvate and lactate under the production of energy until the fructose 1,6-P2 levels drop below a certain threshold value, which allows the dissociation of the tetrameric form of M2-PK to the dimeric form. Thereafter, the cycle of oscillation starts again when the fructose 1,6-P2 levels reach a certain upper threshold value which induces the tetramerization of M2-PK.
When M2-PK is mainly in the less active dimeric form, energy is produced by the degradation of the amino acid glutamine to aspartate, pyruvate and lactate, which is termed glutaminolysis.
In tumor cells the increased rate of lactate production in the presence of oxygen is termed the Warburg effect. | 1 | Applied and Interdisciplinary Chemistry |
Levomilnacipran was developed by Forest Laboratories and Pierre Fabre Group, and was approved by the Food and Drug Administration in July 2013. | 0 | Theoretical and Fundamental Chemistry |
Currently, there are several NRTIs in various stages of clinical and preclinical development. The main reasons for continuing the search for new NRTIs against HIV-1 are to decrease toxicity, increase efficiency against resistant viruses, and simplify anti-HIV-1 treatment. | 1 | Applied and Interdisciplinary Chemistry |
The imine condensation reaction which eliminates water (exemplified by reacting aniline with benzaldehyde using an acid catalyst) can be used as a synthetic route to reach a new class of COFs. The 3D COF called COF-300 and the 2D COF named TpOMe-DAQ are good examples of this chemistry. When 1,3,5-triformylphloroglucinol (TFP) is used as one of the SBUs, two complementary tautomerizations occur (an enol to keto and an imine to enamine) which result in a β-ketoenamine moiety as depicted in the DAAQ-TFP framework. Both DAAQ-TFP and TpOMe-DAQ COFs are stable in acidic aqueous conditions and contain the redox active linker 2,6-diaminoanthroquinone which enables these materials to reversibly store and release electrons within a characteristic potential window. Consequently, both of these COFs have been investigated as electrode materials for potential use in supercapacitors. | 0 | Theoretical and Fundamental Chemistry |
By definition, these compounds occur in nature, but the subfield includes anthropogenic species, such as pollutants (e.g., methylmercury) and drugs (e.g., Cisplatin). The field, which incorporates many aspects of biochemistry, includes many kinds of compounds, e.g., the phosphates in DNA, and also metal complexes containing ligands that range from biological macromolecules, commonly peptides, to ill-defined species such as humic acid, and to water (e.g., coordinated to gadolinium complexes employed for MRI). Traditionally bioinorganic chemistry focuses on electron- and energy-transfer in proteins relevant to respiration. Medicinal inorganic chemistry includes the study of both non-essential and essential elements with applications to diagnosis and therapies.
* Examples: hemoglobin, methylmercury, carboxypeptidase | 0 | Theoretical and Fundamental Chemistry |
(+)-Discodermolide is able to induce the senescence phenotype. (+)-Discodermolide treated Hela, MDA-MB-231, HCT-116, and A549 cells exhibited moderated to high levels of β-galactosidase activity in all four cell lines. The β-galactosidase activity is one of the hallmarks of senescence. Other common features include a cessation of proliferation and an increased cytoplasmic area. (+)-Discodermolide also induced up-regulation and activation in three proteins (p66Shc, Erk1, and Erk2). | 0 | Theoretical and Fundamental Chemistry |
In chemical kinetics, the elementary reactions are represented by the stoichiometric equations
where are the components and are the stoichiometric coefficients. Here, the reverse reactions with positive constants are included in the list separately. We need this separation of direct and reverse reactions to apply later the general formalism to the systems with some irreversible reactions. The system of stoichiometric equations of elementary reactions is the reaction mechanism.
The stoichiometric matrix is , (gain minus loss). This matrix need not be square. The stoichiometric vector is the rth row of with coordinates .
According to the generalized mass action law, the reaction rate for an elementary reaction is
where is the activity (the "effective concentration") of .
The reaction mechanism includes reactions with the reaction rate constants . For each r the following notations are used: ; ; is the reaction rate constant for the reverse reaction if it is in the reaction mechanism and 0 if it is not; is the reaction rate for the reverse reaction if it is in the reaction mechanism and 0 if it is not. For a reversible reaction, is the equilibrium constant.
The principle of detailed balance for the generalized mass action law is: For given values there exists a positive equilibrium that satisfies detailed balance, that is, . This means that the system of linear detailed balance equations
is solvable (). The following classical result gives the necessary and sufficient conditions for the existence of a positive equilibrium with detailed balance (see, for example, the textbook).
Two conditions are sufficient and necessary for solvability of the system of detailed balance equations:
# If then and, conversely, if then (reversibility);
# For any solution of the system
the Wegscheider's identity holds:
Remark. It is sufficient to use in the Wegscheider conditions a basis of solutions of the system .
In particular, for any cycle in the monomolecular (linear) reactions the product of the reaction rate constants in the clockwise direction is equal to the product of the reaction rate constants in the counterclockwise direction. The same condition is valid for the reversible Markov processes (it is equivalent to the "no net flow" condition).
A simple nonlinear example gives us a linear cycle supplemented by one nonlinear step:
There are two nontrivial independent Wegscheider's identities for this system:
and
They correspond to the following linear relations between the stoichiometric vectors:
and
The computational aspect of the Wegscheider conditions was studied by D. Colquhoun with co-authors.
The Wegscheider conditions demonstrate that whereas the principle of detailed balance states a local property of equilibrium, it implies the relations between the kinetic constants that are valid for all states far from equilibrium. This is possible because a kinetic law is known and relations between the rates of the elementary processes at equilibrium can be transformed into relations between kinetic constants which are used globally. For the Wegscheider conditions this kinetic law is the law of mass action (or the generalized law of mass action). | 0 | Theoretical and Fundamental Chemistry |
At high pressure, zirconium tungstate undergoes a series of phase transitions, first to an amorphous phase, and then to a UO-type phase, in which the zirconium and tungsten atoms are disordered. | 0 | Theoretical and Fundamental Chemistry |
In the early 2000s, handling genetic information as exceptional, including legal or regulatory protections, garnered strong support. It was argued that genomic information may need special policy and practice protections within the context of electronic health records (EHRs). In 2008, the Genetic Information Nondiscrimination Act (GINA) was enacted to protect patients from health insurance companies discriminating against an individual based on genetic information.
More recently it has been argued that genetic exceptionalism is past its expiration date as we move into a blended genomic/big data era of medicine, yet exceptionalism practices continue to permeate clinical healthcare today. Garrison et al. recently relayed a call to action to update verbiage from genetic exceptionalism to genomic contextualism in that we recognize a fundamental duality of genetic information. This allows room in the argument for different types of genetic information to be handled differently while acknowledging that genomic information is similar and yet distinct from other health-related information. Genomic contextualism would allow for a case-by-case analysis of the technology and the context of its use (e.g., clinical practice, research, secondary findings).
Others argue that genetic information is indeed distinct from other health-related information but not to the extent of requiring legal/regulatory protections, similar to other sensitive health-related data such as HIV status. Additionally, Evans et al. argue that the EHR has sufficient privacy standards to hold other sensitive information such as social security numbers and that the fundamental nature of an EHR is to house highly personal information. Similarly, a systematic review reported that the public had concern over privacy of genetic information, with 60% agreeing that maintaining privacy was not possible; however, 96% agreed that a direct-to-consumer testing company had protected their privacy, with 74% saying their information would be similarly or better protected in an EHR. With increasing technological capabilities in EHRs, it is possible to mask or hide genetic data from subsets of providers and there is not consensus on how, when, or from whom genetic information should be masked. Rigorous protection and masking of genetic information is argued to impede further scientific progress and clinical translation into routine clinical practices. | 1 | Applied and Interdisciplinary Chemistry |
Fragmented genomic DNA or complementary DNA (cDNA) of interest is cloned into plasmid vectors. The cloning sites are flanked with adaptor sequences that contain restriction sites for endonucleases (discussed below). Inserts are ligated to the plasmid vectors and individual vectors are then transformed into E. coli making the PET library. PET sequences are obtained by purifying plasmid and digesting with specific endonuclease leaving two short sequences on the ends of the vectors. Under intramolecular (dilute) conditions, vectors are re-circularized and ligated, leaving only the ditags in the vector. The sequences unique to the clone are now paired together. Depending on the next-generation sequencing technique, PET sequences can be left singular, dimerized, or concatenated into long chains. | 1 | Applied and Interdisciplinary Chemistry |
Dark fermentation reactions do not require light energy. These are capable of constantly producing hydrogen from organic compounds throughout the day and night. Typically these reactions are coupled to the formation of carbon dioxide or formate. Important reactions that result in hydrogen production start with glucose, which is converted to acetic acid:
:CHO + 2 HO → 2 CHCOH + 2 CO + 4 H
A related reaction gives formate instead of carbon dioxide:
:CHO + 2 HO → 2 CHCOH + 2 HCOH + 2 H
These reactions are exergonic by 216 and 209 kcal/mol, respectively.
Using synthetic biology, bacteria can be genetically altered to enhance this reaction.
Photofermentation differs from dark fermentation, because it only proceeds in the presence of light. Electrohydrogenesis is used in microbial fuel cells. | 1 | Applied and Interdisciplinary Chemistry |
Site-directed spin labeling (SDSL) was pioneered in the laboratory of Dr. W.L. Hubbell. In SDSL, sites for attachment of spin labels are introduced into recombinantly expressed proteins by site-directed mutagenesis. Functional groups contained within the spin label determine their specificity. At neutral pH, protein thiol groups specifically react with the functional groups methanethiosulfonate, maleimide, and iodoacetamide, creating a covalent bond with the amino acid Cys.
Spin labels are a unique molecular reporter, in that they are paramagnetic (contain an unpaired electron). Spin labels were first synthesized in the laboratory of H. M. McConnell in 1965. Since then, a variety of nitroxide spin labels have enjoyed widespread use for the study of macromolecular structure and dynamics because of their stability and simple EPR signal.
The nitroxyl radical (N-O) is usually incorporated into a heterocyclic ring (e.g. pyrrolidine), and the unpaired electron is predominantly localized to the N-O bond. Once incorporated into the protein, a spin label's motions are dictated by its local environment. Because spin labels are exquisitely sensitive to motion, this has profound effects on its EPR spectrum.
The assembly of multi-subunit membrane protein complexes has also been studied using spin labeling. The binding of the PsaC subunit to the PsaA and PsaB subunits of the photosynthetic reaction center, Photosystem I, has been analyzed in great detail using this technique.
Dr. Ralf Langens group showed that SDSL with EPR (University of Southern California, Los Angeles) can be used to understand the structure of amyloid fibrils and the structure of membrane bound Parkinsons disease protein alpha-synuclein. A 2012 study generated a high resolution structure of IAPP fibrils using a combination of SDSL, pulse EPR and computational biology.
<br /> | 0 | Theoretical and Fundamental Chemistry |
For many systems of physical and chemical kinetics, detailed balance provides sufficient conditions for the strict increase of entropy in isolated systems. For example, the famous Boltzmann H-theorem states that, according to the Boltzmann equation, the principle of detailed balance implies positivity of entropy production. The Boltzmann formula (1872) for entropy production in rarefied gas kinetics with detailed balance served as a prototype of many similar formulas for dissipation in mass action kinetics and generalized mass action kinetics with detailed balance.
Nevertheless, the principle of detailed balance is not necessary for entropy growth. For example, in the linear irreversible cycle , entropy production is positive but the principle of detailed balance does not hold.
Thus, the principle of detailed balance is a sufficient but not necessary condition for entropy increase in Boltzmann kinetics. These relations between the principle of detailed balance and the second law of thermodynamics were clarified in 1887 when Hendrik Lorentz objected to the Boltzmann H-theorem for polyatomic gases. Lorentz stated that the principle of detailed balance is not applicable to collisions of polyatomic molecules.
Boltzmann immediately invented a new, more general condition sufficient for entropy growth. Boltzmann's condition holds for all Markov processes, irrespective of time-reversibility. Later, entropy increase was proved for all Markov processes by a direct method. These theorems may be considered as simplifications of the Boltzmann result. Later, this condition was referred to as the "cyclic balance" condition (because it holds for irreversible cycles) or the "semi-detailed balance" or the "complex balance". In 1981, Carlo Cercignani and Maria Lampis proved that the Lorentz arguments were wrong and the principle of detailed balance is valid for polyatomic molecules. Nevertheless, the extended semi-detailed balance conditions invented by Boltzmann in this discussion remain the remarkable generalization of the detailed balance. | 0 | Theoretical and Fundamental Chemistry |
Trifluoroperacetic acid is primarily used as an oxidising agent. In September 1953, the Journal of the American Chemical Society published work by William D. Emmons and Arthur F. Ferris reporting that this reagent, generated in situ, was capable of oxidising aniline to nitrobenzene. Over the following two years, Emmons reported a preparative method for this reagent and published six further manuscripts in this journal on its applications; Emmons is remembered in part as the pioneer and developer of trifluoroperacetic acid as a laboratory reagent, which has since become useful as a reagent for many different types of synthetic reactions.
One example is the formation of the hypervalent iodine compound , which is used to carry out the Hofmann rearrangement under acidic conditions. The hypervalent compound is accessible in two ways, and which is chosen usually depends on what materials are available: it can be prepared from its acetate analogue by an exchange reaction, or by reacting iodobenzene with a combination of trifluoroperacetic acid and trifluoroacetic acid: | 0 | Theoretical and Fundamental Chemistry |
Kendal Black Drop was a drug based on opium. Named after Kendal on the edge of the Lake District, England, it is associated with the romantic poet, Samuel Taylor Coleridge. | 1 | Applied and Interdisciplinary Chemistry |
Joseph Howard Mathews (October 15, 1881 – April 15, 1970) was an American physical chemist, university professor, and expert on firearm identification. Mathews was Chair of the Department of Chemistry at the University of Wisconsin–Madison for 33 years (1919–1952). | 0 | Theoretical and Fundamental Chemistry |
Arsaalkynes are produced by dehydrohalogenation or related base-induced elimination reactions. The case of HCAs is illustrative:
Owing to the principles of the double bond rule, arsaalkynes tend to oligomerize more readily than the phosphorus analogues. Thus attempts to prepare AsCCMe produce the tetramer, which has a cubane structure. The very bulky substituent CH-2,4,6-(t-Bu) does however allow the crystallization of the monomeric arsaalkyne. Its As-C bond length is 1.657(7) Å. | 0 | Theoretical and Fundamental Chemistry |
Senapathy proposed that the gene-expression regulatory sequences (promoter and poly-A addition site sequences) also could have originated from stop codons. A conserved sequence, AATAAA, exists in almost every gene a short distance downstream from the end of the protein-coding message and serves as a signal for the addition of poly(A) in the mRNA copy of the gene. This poly(A) sequence signal contains a stop codon, TAA. A sequence shortly downstream from this signal, thought to be part of the complete poly(A) signal, also contains the TAG and TGA stop codons.
Eukaryotic RNA-polymerase-II-dependent promoters can contain a TATA box (consensus sequence TATAAA), which contains the stop codon TAA. Bacterial promoter elements at ~10 bases exhibits a TATA box with a consensus of TATAAT (which contains the stop codon TAA), and at -35 bases exhibits a consensus of TTGACA (containing the stop codon TGA). Thus, the evolution of the whole RNA processing mechanism seems to have been influenced by the too-frequent occurrence of stop codons, thus making the stop codons the focal points for RNA processing. | 1 | Applied and Interdisciplinary Chemistry |
Isotopes naturally found on earth are usually those that are stable or have a decay time larger than, or at least a significant fraction of the age of the Earth (about 5 x 10 years). Isotopes with shorter halflifes mainly exist as decay products from longer lived isotopes, and, as in C14, from irradiation of the upper atmosphere.
Radioisotopes with a sufficiently long halflife, and whose decay produces an appreciable amount of gamma rays are:
* Potassium K with half-life of 1.3 x 10 years, which emits 0 α, 1 β, and 1 γ-ray
* Thorium Th with half-life of 1.4 x 10 years, which emits 7 α, 5 β, and numerous γ-ray with different energies
* Uranium U with half-life of 4.4 x 10 years, which emits 8 α, 6 β, and numerous γ-ray with different energies
Each of these elements emits gamma-rays with distinctive energy. Figure 1 shows the energies of emitted gamma-ray from the three main isotopes. Potassium 40 decays directly to stable argon 40 with the emission of 1.46 MeV gamma-ray. Uranium 238 and thorium 232 decay sequentially through a long sequence of various isotopes until a final stable isotope. The spectrum of the gamma-rays emitted by these two isotopes consists of gamma-ray of many different energies and form a complete spectra. The peak of thorium series can be found at 2.62 MeV and the Uranium series at 1.76 MeV. | 0 | Theoretical and Fundamental Chemistry |
Photoinhibition can be measured from isolated thylakoid membranes or their subfractions, or from intact cyanobacterial cells by measuring the light-saturated rate of oxygen evolution in the presence of an artificial electron acceptor (quinones and dichlorophenol-indophenol have been used).
The degree of photoinhibition in intact leaves can be measured using a fluorimeter to measure the ratio of variable to maximum value of chlorophyll a fluorescence (F/F). This ratio can be used as a proxy of photoinhibition because more energy is emitted as fluorescence from Chlorophyll a when many excited electrons from PSII are not captured by the acceptor and decay back to their ground state.
When measuring F/F, the leaf must be incubated in the dark for at least 10 minutes, preferably longer, before the measurement, in order to let non-photochemical quenching relax. | 0 | Theoretical and Fundamental Chemistry |
In Africa, the Adal Empire and the Abyssinian Empire both deployed gunpowder weapons during the Adal-Abyssinian War. Imported from Arabia, and the wider Islamic world, the Adalites, led by Ahmed ibn Ibrahim al-Ghazi, were the first African power to introduce cannon warfare to the African continent. Later on as the Portuguese Empire entered the war it would supply and train the Abyssinians with cannon and muskets, while the Ottoman Empire sent soldiers and cannon to back Adal. The conflict proved, through their use on both sides, the value of firearms such as the matchlock musket, cannon, and the arquebus over traditional weapons.
Ernest Gellner in his book Nations and Nationalism argues that the centralizing potential of the gun and the book, enabled both the Somali people and the Amhara people to dominate the political history of a vast area in Africa, despite neither of them being numerically predominant. | 1 | Applied and Interdisciplinary Chemistry |
FeTAML(=O), TAML = tetra-amido macrocyclic ligand, is formed by the reaction of [Fe(TAML)(HO)](PPh) with 2-5 equivalents of meta-chloroperbenzoic acid at -60 ˚C in n-butyronitrile. This deep green compound (two λ at 445 and 630 nm respectively) is stable at 77 K. The stabilization of Fe(V) is attributed to the strong π–donor capacity of deprotonated amide nitrogens. | 0 | Theoretical and Fundamental Chemistry |
Benzenediazonium chloride heated with cuprous chloride or cuprous bromide respectively dissolved in HCl or HBr yield chlorobenzene or bromobenzene, respectively. | 0 | Theoretical and Fundamental Chemistry |
The CRC Handbook of Chemistry and Physics defines specific rotation as:
= α/γl, where α is the angle through which plane polarized light is rotated by a solution of mass concentration γ and path length l. Here θ is the Celsius temperature and λ the wavelength of the light at which the measurement is carried out.</blockquote>
Values for specific rotation are reported in units of deg·mL·g·dm, which are typically shortened to just degrees, wherein the other components of the unit are tacitly assumed. These values should always be accompanied by information about the temperature, solvent and wavelength of light used, as all of these variables can affect the specific rotation. As noted above, temperature and wavelength are frequently reported as a superscript and subscript, respectively, while the solvent is reported parenthetically, or omitted if it happens to be water. | 0 | Theoretical and Fundamental Chemistry |
*Production and distribution of radioisotopes for civilian research and medical use at the Oak Ridge National Laboratory in 1946
*Development of deep-tank fermentation for the mass production of penicillin by Pfizer in the 1940s
*Development of acrylic emulsion technology for the production of acrylic paint by Rohm and Haas in 1953 | 1 | Applied and Interdisciplinary Chemistry |
Zinc is normally associated with metal mining, especially Lead and Silver mining but is also a component pollutant associated with a variety of other metal mining activities and with Coal mining. Zinc is toxic at relatively low concentrations to many aquatic organisms. Microregma starts to show a toxic reaction at concentrations as low as 0.33 mg/L. | 1 | Applied and Interdisciplinary Chemistry |
In May 2022, scientists at University of Cambridge announced they created an algae energy harvester, that uses natural sunlight to power a small microprocessor, initially powering the processor for six months, and then kept going for a full year. The device, which is about the size of AA battery, is a small container with water and blue green algae. The device does not generate a huge amount of power, but it can be used for Internet of Things devices, eliminating the need for traditional batteries such as lithium ion batteries. The goal is to have more a environmentally friendly power source that can be used in remote areas. | 1 | Applied and Interdisciplinary Chemistry |
Bioretrosynthesis is a technique for synthesizing organic chemicals from inexpensive precursors and evolved enzymes. The technique builds on the retro-evolution hypothesis proposed in 1945 by geneticist Norman Horowitz. | 0 | Theoretical and Fundamental Chemistry |
A number of proteins are known to be associated with TAD formation including the protein CTCF and the protein complex cohesin. It is also unknown what components are required at TAD boundaries; however, in mammalian cells, it has been shown that these boundary regions have comparatively high levels of CTCF binding. In addition, some types of genes (such as transfer RNA genes and housekeeping genes) appear near TAD boundaries more often than would be expected by chance.
Computer simulations have shown that chromatin loop extrusion driven by cohesin motors can generate TADs. In the loop extrusion model, cohesin binds chromatin, pulls it in, and extrudes chromatin to progressively grow a loop. Chromatin on both sides of the cohesin complex is extruded until cohesin encounters a chromatin-bound CTCF protein, typically located at the boundary of a TAD. In this way, TAD boundaries can be brought together as the anchors of a chromatin loop. Indeed, in vitro, cohesin has been observed to processively extrude DNA loops in an ATP-dependent manner and stall at CTCF. However, some in vitro data indicates that the observed loops may be artifacts. Importantly, since cohesins can dynamically unbind from chromatin, this model suggests that TADs (and associated chromatin loops) are dynamic, transient structures, in agreement with in vivo observations.
Other mechanisms for TAD formation have been suggested. For example, some simulations suggest that transcription-generated supercoiling can relocalize cohesin to TAD boundaries or that passively diffusing cohesin “slip links” can generate TADs. | 1 | Applied and Interdisciplinary Chemistry |
Passive daytime radiative cooling is referred to as more stable, adaptable, and reversible when compared to stratospheric aerosol injection, which proposes injecting particles into the atmosphere to increase radiative forcing to reduce temperatures. Studies have warned against stratospheric aerosol injections potential to contribute to further ozone loss and heat the Earths lower stratosphere further, stating that the injection of sulfate particles "would reflect more of the incoming solar radiation back into space, but it would also capture more of the outgoing thermal radiation back to the Earth" and therefore accelerate warming.
Wang et al. states that stratospheric aerosol injection "might cause potentially dangerous threats to the Earth’s basic climate operations" that may not be reversible, and thus put forth a preference for passive radiative cooling. Munday noted that although "unexpected effects will likely occur" with the global implementation of PDRC, that "these structures can be removed immediately if needed, unlike methods that involve dispersing particulate matter into the atmosphere, which can last for decades."
When compared to the reflective surfaces approach of increasing the reflectivity or albedo of surfaces, such as through painting roofs white, or the space mirror proposals of "deploying giant reflective surfaces in space," Munday states that "the increased reflectivity likely falls short of what is needed and comes at a high financial cost." PDRC differs from the reflective surfaces approach by "increasing the radiative heat emission from the Earth rather than merely decreasing its solar absorption." | 0 | Theoretical and Fundamental Chemistry |
The mechanisms of chemical reactions can be investigated by observing how the kinetics of a reaction is changed by making an isotopic modification of a substrate, known as the kinetic isotope effect. This is now a standard method in organic chemistry. Briefly, replacing normal hydrogen (protons) by deuterium within a molecule causes the molecular vibrational frequency of X-H (for example C-H, N-H and O-H) bonds to decrease, which leads to a decrease in vibrational zero-point energy. This can lead to a decrease in the reaction rate if the rate-determining step involves breaking a bond between hydrogen and another atom. Thus, if the reaction changes in rate when protons are replaced by deuteriums, it is reasonable to assume that the breaking of the bond to hydrogen is part of the step which determines the rate. | 0 | Theoretical and Fundamental Chemistry |
Apamin is the smallest neurotoxin polypeptide known, and the only one that passes the blood-brain barrier. Apamin thus reaches its target organ, the central nervous system. Here it inhibits small-conductance Ca-activated K channels (SK channels) in neurons. These channels are responsible for the afterhyperpolarizations that follow action potentials, and therefore regulate the repetitive firing frequency.
Three different types of SK channels show different characteristics. Only SK2 and SK3 are blocked by apamin, whereas SK1 is apamin insensitive. SK channels function as a tetramer of subunits. Heteromers have intermediate sensitivity. SK channels are activated by the binding of intracellular Ca to the protein calmodulin, which is constitutively associated to the channel. Transport of potassium ions out of the cell along their concentration gradient causes the membrane potential to become more negative. The SK channels are present in a wide range of excitable and non-excitable cells, including cells in the central nervous system, intestinal myocytes, endothelial cells, and hepatocytes.
Binding of apamin to SK channels is mediated by amino acids in the pore region as well as extracellular amino acids of the SK channel. It is likely that the inhibition of SK channels is caused by blocking of the pore region, which hinders the transport of potassium ions. This will increase the neuronal excitability and lower the threshold for generating an action potential. Other toxins that block SK channels are tamapin and scyllatoxin. | 1 | Applied and Interdisciplinary Chemistry |
Agmatine has been discussed as a putative neurotransmitter. It is synthesized in the brain, stored in synaptic vesicles, accumulated by uptake, released by membrane depolarization, and inactivated by agmatinase. Agmatine binds to α-adrenergic receptor and imidazoline receptor binding sites, and blocks NMDA receptors and other cation ligand-gated channels. However, while agmatine binds to α-adrenergic receptors, it exerts neither an agonistic nor antagonistic effect on these receptors, lacking any intrinsic activity. Short only of identifying specific ("own") post-synaptic receptors, agmatine fulfills Henry Dale's criteria for a neurotransmitter and is hence considered a neuromodulator and co-transmitter. The existence of theoretical agmatinergic-mediated neuronal systems has not yet been demonstrated although the existence of such receptors is implied by its prominence in the mediation of both the central and peripheral nervous systems. Research into agmatine-specific receptors and transmission pathways continues.
Due to its ability to pass through open cationic channels, agmatine has also been used as a surrogate metric of integrated ionic flux into neural tissue upon stimulation. When neural tissue is incubated in agmatine and an external stimulus is applied, only cells with open channels will be filled with agmatine, allowing identification of which cells are sensitive to that stimuli and the degree to which they opened their cationic channels during the stimulation period. | 1 | Applied and Interdisciplinary Chemistry |
The RNA polymerase II transcribes U1, U2, U4, U5 and the less abundant U11, U12 and U4atac (snRNAs) acquire a m7G-cap which serves as an export signal. Nuclear export is mediated by CRM1. | 1 | Applied and Interdisciplinary Chemistry |
The added complexity of generating a eukaryotic cell carries with it an increase in the complexity of transcriptional regulation. Eukaryotes have three RNA polymerases, known as Pol I, Pol II, and Pol III. Each polymerase has specific targets and activities, and is regulated by independent mechanisms. There are a number of additional mechanisms through which polymerase activity can be controlled. These mechanisms can be generally grouped into three main areas:
*Control over polymerase access to the gene. This is perhaps the broadest of the three control mechanisms. This includes the functions of histone remodeling enzymes, transcription factors, enhancers and repressors, and many other complexes
*Productive elongation of the RNA transcript. Once polymerase is bound to a promoter, it requires another set of factors to allow it to escape the promoter complex and begin successfully transcribing RNA.
*Termination of the polymerase. A number of factors which have been found to control how and when termination occurs, which will dictate the fate of the RNA transcript.
All three of these systems work in concert to integrate signals from the cell and change the transcriptional program accordingly.
While in prokaryotic systems the basal transcription state can be thought of as nonrestrictive (that is, “on” in the absence of modifying factors), eukaryotes have a restrictive basal state which requires the recruitment of other factors in order to generate RNA transcripts. This difference is largely due to the compaction of the eukaryotic genome by winding DNA around histones to form higher order structures. This compaction makes the gene promoter inaccessible without the assistance of other factors in the nucleus, and thus chromatin structure is a common site of regulation. Similar to the sigma factors in prokaryotes, the general transcription factors (GTFs) are a set of factors in eukaryotes that are required for all transcription events. These factors are responsible for stabilizing binding interactions and opening the DNA helix to allow the RNA polymerase to access the template, but generally lack specificity for different promoter sites. A large part of gene regulation occurs through transcription factors that either recruit or inhibit the binding of the general transcription machinery and/or the polymerase. This can be accomplished through close interactions with core promoter elements, or through the long distance enhancer elements.
Once a polymerase is successfully bound to a DNA template, it often requires the assistance of other proteins in order to leave the stable promoter complex and begin elongating the nascent RNA strand. This process is called promoter escape, and is another step at which regulatory elements can act to accelerate or slow the transcription process. Similarly, protein and nucleic acid factors can associate with the elongation complex and modulate the rate at which the polymerase moves along the DNA template. | 1 | Applied and Interdisciplinary Chemistry |
Since semi-displacement and planing hulls generate a significant amount of lift in operation, they are capable of breaking the barrier of the wave propagation speed and operating in realms of much lower drag, but to do this they must be capable of first pushing past that speed, which requires significant power. This stage is called the transition stage and at this stage the rate of wave-making resistance is the highest. Once the hull gets over the hump of the bow wave, the rate of increase of the wave drag will start to reduce significantly. The planing hull will rise up clearing its stern off the water and its trim will be high. Underwater part of the planing hull will be small during the planing regime.
A qualitative interpretation of the wave resistance plot is that a displacement hull resonates with a wave that has a crest near its bow and a trough near its stern, because the water is pushed away at the bow and pulled back at the stern. A planing hull simply pushed down on the water under it, so it resonates with a wave that has a trough under it. If it has about twice the length it will therefore have only square root (2) or 1.4 times the speed. In practice most planing hulls usually move much faster than that. At four times hull speed the wavelength is already 16 times longer than the hull. | 1 | Applied and Interdisciplinary Chemistry |
The Cieplak effect relies on the stabilizing interaction of mixing full and empty orbitals to delocalize electrons, known as hyperconjugation. When the highest occupied molecular orbital (HOMO) of one system and the lowest unoccupied molecular orbital (LUMO) of another system have comparable energies and spatial overlap, the electrons can delocalize and sink into a lower energy level. Often, the HOMO of a system is a full σ (bonding) orbital and the LUMO is an empty σ* (antibonding) orbital. This mixing is a stabilizing interaction and has been widely used to explain such phenomena as the anomeric effect. A common requirement of hyperconjugation is that the bonds donating and accepting electron density are antiperiplanar to each other, to allow for maximum orbital overlap.
The Cieplak effect uses hyperconjugation to explain the face-selective addition of nucleophiles to carbonyl carbons. Specifically, donation into the low-lying σ* bond by antiperiplanar electron-donating substituents is the stabilizing interaction which lowers the transition state energy of one stereospecific reaction pathway and thus increases the rate of attack from one side. In the simplest model, a conformationally constrained cyclohexanone is reduced to the corresponding alcohol. Reducing agents add a hydride to the carbonyl carbon via attack along the Burgi–Dunitz angle, which can come from the top along a pseudo-axial trajectory or from below, along a pseudo-equatorial trajectory. It has long been known that large reducing agents add hydride to the equatorial position to avoid steric interactions with axial hydrogens on the ring. Small hydride sources, however, add hydride to an axial position for reasons which are still disputed.
The Cieplak effect explains this phenomenon by postulating that hyperconjugation of the forming σ* orbital with geometrically aligned σ orbitals is the stabilizing interaction that controls stereoselectivity. In an equatorial approach, the bonds that are geometrically aligned antiperiplanar to the forming C–H bond are the C–C bonds of the ring, so they donate electron density to σ*. In an axial approach, the neighboring axial C–H bonds are aligned antiperiplanar to the forming C–H bond, so they donate electron density to σ*. Because C-H bonds are better electron donors than C–C bonds, they are better able to participate in this stabilizing interaction and so this pathway is favored. | 0 | Theoretical and Fundamental Chemistry |
In cell biology, chromosome territories are regions of the nucleus preferentially occupied by particular chromosomes.
Interphase chromosomes are long DNA strands that are extensively folded, and are often described as appearing like a bowl of spaghetti. The chromosome territory concept holds that despite this apparent disorder, chromosomes largely occupy defined regions of the nucleus. Most eukaryotes are thought to have chromosome territories, although the budding yeast S. cerevisiae is an exception to this. | 1 | Applied and Interdisciplinary Chemistry |
Molecular self-assembly underlies the construction of biologic macromolecular assemblies and biomolecular condensates in living organisms, and so is crucial to the function of cells. It is exhibited in the self-assembly of lipids to form the membrane, the formation of double helical DNA through hydrogen bonding of the individual strands, and the assembly of proteins to form quaternary structures. Molecular self-assembly of incorrectly folded proteins into insoluble amyloid fibers is responsible for infectious prion-related neurodegenerative diseases. Molecular self-assembly of nanoscale structures plays a role in the growth of the remarkable β-keratin lamellae/setae/spatulae structures used to give geckos the ability to climb walls and adhere to ceilings and rock overhangs. | 0 | Theoretical and Fundamental Chemistry |
Association theory (also aggregate theory) is a theory first advanced by chemist Thomas Graham in 1861 to describe the molecular structure of colloidal substances such as cellulose and starch, now understood to be polymers. Association theory postulates that such materials are solely composed of a collection of smaller molecules bound together by an unknown force. Graham termed these materials colloids. Prior to the development of macromolecular theory by Hermann Staudinger in the 1920s, which stated that individual polymers are composed of chains of covalently bonded monomers, association theory remained the most prevalent model of polymer structure in the scientific community.
Importantly, although polymers consist of long chains of covalently linked molecules, the individual polymer chains can often still associate and undergo phase transitions and phase separation to form colloids, liquid crystals, solid crystals, or aggregates. For biopolymers, association leads to formation of biomolecular condensates, micelles and other examples of molecular self-assembly. | 0 | Theoretical and Fundamental Chemistry |
The rare earth element lutetium was independently discovered by three scientists at around the same time in 1907: French scientist Georges Urbain, Austrian Auer von Welsbach, and American Charles James.
All three were successful in separating the substance then known as ytterbium into two new fractions. To name the newly discovered fraction,
Urbain suggested the name "lutecium", for the Roman city of Lutetia that preceded Paris. Auer von Welsbach suggested the name "cassiopeium". James work was not yet published when the others work appeared, and he did not involve himself in subsequent disputes. Lutetium, a slight modification of Urbain's name, was eventually accepted after a long battle between Urbain and Welsbach. | 1 | Applied and Interdisciplinary Chemistry |
When examining a system computationally one may be interested in knowing how the free energy changes as a function of some inter- or intramolecular coordinate (such as the distance between two atoms or a torsional angle). The free energy surface along the chosen coordinate is referred to as the potential of mean force (PMF). If the system of interest is in a solvent, then the PMF also incorporates the solvent effects. | 0 | Theoretical and Fundamental Chemistry |
Assuming that the liquid is a Newtonian fluid, the incompressible Navier–Stokes equation in spherical coordinates for motion in the radial direction gives
Substituting kinematic viscosity and rearranging gives
whereby substituting from mass conservation yields
Note that the viscous terms cancel during substitution. Separating variables and integrating from the bubble boundary to gives | 1 | Applied and Interdisciplinary Chemistry |
Tetrathionate's structure can be visualized by following three edges of a rectangular cuboid, as in the diagram below. The structure shown is the configuration of in BaSO·2HO and NaSO·2HO. Dihedral S–S–S–S angles approaching 90° are common in polysulfides. | 1 | Applied and Interdisciplinary Chemistry |
The particular series of amino acids that form a protein is known as that protein's primary structure. This sequence is determined by the genetic makeup of the individual. It specifies the order of side-chain groups along the linear polypeptide "backbone".
Proteins have two types of well-classified, frequently occurring elements of local structure defined by a particular pattern of hydrogen bonds along the backbone: alpha helix and beta sheet. Their number and arrangement is called the secondary structure of the protein. Alpha helices are regular spirals stabilized by hydrogen bonds between the backbone CO group (carbonyl) of one amino acid residue and the backbone NH group (amide) of the i+4 residue. The spiral has about 3.6 amino acids per turn, and the amino acid side chains stick out from the cylinder of the helix. Beta pleated sheets are formed by backbone hydrogen bonds between individual beta strands each of which is in an "extended", or fully stretched-out, conformation. The strands may lie parallel or antiparallel to each other, and the side-chain direction alternates above and below the sheet. Hemoglobin contains only helices, natural silk is formed of beta pleated sheets, and many enzymes have a pattern of alternating helices and beta-strands. The secondary-structure elements are connected by "loop" or "coil" regions of non-repetitive conformation, which are sometimes quite mobile or disordered but usually adopt a well-defined, stable arrangement.
The overall, compact, 3D structure of a protein is termed its tertiary structure or its "fold". It is formed as result of various attractive forces like hydrogen bonding, disulfide bridges, hydrophobic interactions, hydrophilic interactions, van der Waals force etc.
When two or more polypeptide chains (either of identical or of different sequence) cluster to form a protein, quaternary structure of protein is formed. Quaternary structure is an attribute of polymeric (same-sequence chains) or heteromeric (different-sequence chains) proteins like hemoglobin, which consists of two "alpha" and two "beta" polypeptide chains. | 0 | Theoretical and Fundamental Chemistry |
ATSDR represents the Department of Health and Human Services on the National Response Team and works with other agencies to provide technical assistance during emergencies involving hazardous substances, such as chemical spills. In July 2007, for example, ATSDR responded to the Verdigris River flood in Coffeyville, Kansas, after an oil refinery spilled crude oil into the floodwaters, contaminating many homes in the city. ATSDR worked with EPA and state and local authorities to provide health information to local residents and advised those agencies during the clean-up process. ATSDR also assists with responding to terrorism incidents, which have included the September 11 attacks and the 2001 anthrax attacks. ATSDR responded to 132 chemical emergency events in 2008.
In addition to working with communities and other agencies in the aftermath of chemical emergencies, ATSDR has developed the Managing Hazardous Materials Incidents series, which includes several tools to assist emergency medical services personnel and hospital emergency departments during chemical emergencies. This includes important information on emergency planning, emergency response, and rescuer protection. Another tool is the Medical Management Guidelines, which summarize important information on exposure to common chemicals and provide suggestions for safely treating and decontaminating patients. | 1 | Applied and Interdisciplinary Chemistry |
Macronutrients are defined in several ways.
* The chemical elements humans consume in the largest quantities are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur, summarized as CHNOPS.
* The chemical compounds that humans consume in the largest quantities and provide bulk energy are classified as carbohydrates, proteins, and fats. Water must be also consumed in large quantities but does not provide caloric value.
* Calcium, sodium, potassium, magnesium, and chloride ions, along with phosphorus and sulfur, are listed with macronutrients because they are required in large quantities compared to micronutrients, i.e., vitamins and other minerals, the latter often described as trace or ultratrace minerals.
Macronutrients provide energy:
* Carbohydrates are compounds made up of types of sugar. Carbohydrates are classified according to their number of sugar units: monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).
* Proteins are organic compounds that consist of amino acids joined by peptide bonds. Since the body cannot manufacture some of the amino acids (termed essential amino acids), the diet must supply them. Through digestion, proteins are broken down by proteases back into free amino acids.
* Fats consist of a glycerin molecule with three fatty acids attached. Fatty acid molecules contain a -COOH group attached to unbranched hydrocarbon chains connected by single bonds alone (saturated fatty acids) or by both double and single bonds (unsaturated fatty acids). Fats are needed for construction and maintenance of cell membranes, to maintain a stable body temperature, and to sustain the health of skin and hair. Because the body does not manufacture certain fatty acids (termed essential fatty acids), they must be obtained through one's diet.
* Ethanol is not an essential nutrient, but it does provide calories.The United States Department of Agriculture uses a figure of per gram of alcohol ( per ml) for calculating food energy. For distilled spirits, a standard serving in the U.S. is , which at 40% ethanol (80 proof) would be 14 grams and 98 calories. | 0 | Theoretical and Fundamental Chemistry |
The sources of silica can be divided into two categories: silica in organic and inorganic materials. The former category is also known as biogenic silica, which is a ubiquitous material in animals and plants. The latter category is the second most abundant element in Earth's crust. Silicate minerals are the major components of 95% of presently identified rocks. | 0 | Theoretical and Fundamental Chemistry |
From the titration of protonatable group, one can read the so-called pK which is equal to the pH value where the group is half-protonated (i.e. when 50% such groups would be protonated). The pK is equal to the Henderson–Hasselbalch pK (pK) if the titration curve follows the Henderson–Hasselbalch equation. Most pK calculation methods silently assume that all titration curves are Henderson–Hasselbalch shaped, and pK values in pK calculation programs are therefore often determined in this way. In the general case of multiple interacting protonatable sites, the pK value is not thermodynamically meaningful. In contrast, the Henderson–Hasselbalch pK value can be computed from the protonation free energy via
and is thus in turn related to the protonation free energy of the site via
The protonation free energy can in principle be computed from the protonation probability of the group (pH) which can be read from its titration curve
Titration curves can be computed within a continuum electrostatics approach with formally exact but more elaborate analytical or Monte Carlo (MC) methods, or inexact but fast approximate methods. MC methods that have been used to compute titration curves are Metropolis MC or Wang–Landau MC. Approximate methods that use a mean-field approach for computing titration curves are the Tanford–Roxby method and hybrids of this method that combine an exact statistical mechanics treatment within clusters of strongly interacting sites with a mean-field treatment of intercluster interactions.
In practice, it can be difficult to obtain statistically converged and accurate protonation free energies from titration curves if is close to a value of 1 or 0. In this case, one can use various free energy calculation methods to obtain the protonation free energy such as biased Metropolis MC, free-energy perturbation, thermodynamic integration, the non-equilibrium work method or the Bennett acceptance ratio method.
Note that the pK value does in general depend on the pH value.
This dependence is small for weakly interacting groups like well solvated amino acid side chains on the protein surface, but can be large for strongly interacting groups like those buried in enzyme active sites or integral membrane proteins.
While many protein pKa prediction methods are available, their accuracies often differ significantly due to subtle and often drastic differences in strategy. | 0 | Theoretical and Fundamental Chemistry |
Tripotassium phosphate has few industrial applications.
It is used as an inert, easily removed proton acceptor in organic synthesis. Some of the reactions are listed below:
# The hydrate () has been used to catalyze the deprotection of BOC amines. Microwave radiation is used to aid the reaction.
# As a catalyst for the synthesis of unsymmetrical diaryl ethers using [Bmim] as the solvent. Aryl methane-sulfonates are deprotected and then followed by a nucleophilic aromatic substitution (SAr) with activated aryl halides.
# As a base in the cross-coupling reaction of aryl halides with terminal alkynes. It also plays a role in the deacetonation of 4-aryl-2-methylbut-3-yn-2-ol intermediates.
# As the base in the cross-coupling reaction between aryl halides and phenols or aliphatic alcohols. | 0 | Theoretical and Fundamental Chemistry |
The semiconductor material gallium arsenide (GaAs) is also used for single-crystalline thin film solar cells. Although GaAs cells are very expensive, they hold the world's record in efficiency for a single-junction solar cell at 28.8%. Typically fabricated on crystalline silicon wafer with a 41% fill factor, by moving to porous silicon fill factor can be increased to 56% with potentially reduced cost. Using less active GaAs material by fabricating nanowires is another potential pathway to cost reduction. GaAs is more commonly used in multijunction photovoltaic cells for concentrated photovoltaics (CPV, HCPV) and for solar panels on spacecraft, as the industry favours efficiency over cost for space-based solar power. Based on the previous literature and some theoretical analysis, there are several reasons why GaAs has such high power conversion efficiency. First, GaAs bandgap is 1.43ev which is almost ideal for solar cells. Second, because Gallium is a by-product of the smelting of other metals, GaAs cells are relatively insensitive to heat and it can keep high efficiency when temperature is quite high. Third, GaAs has the wide range of design options. Using GaAs as active layer in solar cell, engineers can have multiple choices of other layers which can better generate electrons and holes in GaAs. | 0 | Theoretical and Fundamental Chemistry |
The bis-nido- is formed by the edge-sharing condensation of a nido- unit and a nido- unit. The m + n + o + p − q count of 16 SEPs are satisfied by ten BH units which provide 10 pairs, two shared boron atoms which provide 3 pairs, and six bridging H atoms which provide 3 pairs. | 0 | Theoretical and Fundamental Chemistry |
This technique is commonly used in conjunction with green fluorescent protein (GFP) fusion proteins, where the studied protein is fused to a GFP. When excited by a specific wavelength of light, the protein will fluoresce. When the protein that is being studied is produced with the GFP, then the fluorescence can be tracked. Photodestroying the GFP, and then watching the repopulation into the bleached area can reveal information about protein interaction partners, organelle continuity and protein trafficking.
If after some time the fluorescence doesn't reach the initial level anymore, then some part of the fluorescence is caused by an immobile fraction (that cannot be replenished by diffusion). Similarly, if the fluorescent proteins bind to static cell receptors, the rate of recovery will be retarded by a factor related to the association and disassociation coefficients of binding. This observation has most recently been exploited to investigate protein binding. Similarly, if the GFP labeled protein is constitutively incorporated into a larger complex, the dynamics of fluorescence recovery will be characterized by the diffusion of the larger complex. | 1 | Applied and Interdisciplinary Chemistry |
The École Nationale Supérieure dÉlectrochimie et dÉlectrométallurgie de Grenoble, or ENSEEG, was one of the French Grandes écoles of engineering (engineering schools). It has been created in 1921 under the name Institut d’électrochimie et d’électrométallurgie (IEE) (Institute of Electrochemistry and Electrometallurgy). The name ENSEEG has been chosen in 1948 and ENSEEG has been part of Grenoble Institute of Technology (INPG or GIT) since its creation in 1971. Therefore, the name INPG-ENSEEG has also been commonly used.
ENSEEG delivered a multidisciplinary education in physical chemistry. The ENSEEG engineers are especially competent in materials science, process engineering and electrochemistry. From September 2008, ENSEEG merged with two other Grandes écoles to create Phelma. | 1 | Applied and Interdisciplinary Chemistry |
The rotating-wave approximation is an approximation used in atom optics and magnetic resonance. In this approximation, terms in a Hamiltonian that oscillate rapidly are neglected. This is a valid approximation when the applied electromagnetic radiation is near resonance with an atomic transition, and the intensity is low. Explicitly, terms in the Hamiltonians that oscillate with frequencies are neglected, while terms that oscillate with frequencies are kept, where is the light frequency, and is a transition frequency.
The name of the approximation stems from the form of the Hamiltonian in the interaction picture, as shown below. By switching to this picture the evolution of an atom due to the corresponding atomic Hamiltonian is absorbed into the system ket, leaving only the evolution due to the interaction of the atom with the light field to consider. It is in this picture that the rapidly oscillating terms mentioned previously can be neglected. Since in some sense the interaction picture can be thought of as rotating with the system ket only that part of the electromagnetic wave that approximately co-rotates is kept; the counter-rotating component is discarded.
The rotating-wave approximation is closely related to, but different from, the secular approximation. | 0 | Theoretical and Fundamental Chemistry |
Photochromic lenses were developed by William H. Armistead and Stanley Donald Stookey at the Corning Glass Works Inc. in the 1960s. | 0 | Theoretical and Fundamental Chemistry |
The concept of the DNA of Things (DoT) was introduced in 2019 by a team of researchers from Israel and Switzerland, including Yaniv Erlich and Robert Grass. DoT encodes digital data into DNA molecules, which are then embedded into objects. This gives the ability to create objects that carry their own blueprint, similar to biological organisms. In contrast to Internet of things, which is a system of interrelated computing devices, DoT creates objects which are independent storage objects, completely off-grid.
As a proof of concept for DoT, the researcher 3D-printed a Stanford bunny which contains its blueprint in the plastic filament used for printing. By clipping off a tiny bit of the ear of the bunny, they were able to read out the blueprint, multiply it and produce a next generation of bunnies. In addition, the ability of DoT to serve for steganographic purposes was shown by producing non-distinguishable lenses which contain a YouTube video integrated into the material. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, dioxirane (systematically named dioxacyclopropane, also known as methylene peroxide or peroxymethane) is an organic compound with formula . The molecule consists of a ring with one methylene and two oxygen atoms. It is of interest as the smallest cyclic organic peroxide, but otherwise it is of little practical value. | 0 | Theoretical and Fundamental Chemistry |
In March 1996, a group of scientists at Lawrence Livermore National Laboratory reported that they had serendipitously produced the first identifiably metallic hydrogen for about a microsecond at temperatures of thousands of kelvins, pressures of over , and densities of approximately . The team did not expect to produce metallic hydrogen, as it was not using solid hydrogen, thought to be necessary, and was working at temperatures above those specified by metallization theory. Previous studies in which solid hydrogen was compressed inside diamond anvils to pressures of up to , did not confirm detectable metallization. The team had sought simply to measure the less extreme electrical conductivity changes they expected. The researchers used a 1960s-era light-gas gun, originally employed in guided missile studies, to shoot an impactor plate into a sealed container containing a half-millimeter thick sample of liquid hydrogen. The liquid hydrogen was in contact with wires leading to a device measuring electrical resistance. The scientists found that, as pressure rose to , the electronic energy band gap, a measure of electrical resistance, fell to almost zero. The band gap of hydrogen in its uncompressed state is about , making it an insulator but, as the pressure increases significantly, the band gap gradually fell to . Because the thermal energy of the fluid (the temperature became about due to compression of the sample) was above , the hydrogen might be considered metallic. | 0 | Theoretical and Fundamental Chemistry |
Runoff across some land uses may become contaminated, where pollutant concentrations exceed those typically found in stormwater. These "hot spots" include commercial plant nurseries, recycling facilities, fueling stations, industrial storage, marinas, some outdoor loading facilities, public works yards, hazardous materials generators (if containers are exposed to rainfall), vehicle service, washing, and maintenance areas, and steam cleaning facilities. Since porous pavement is an infiltration practice, it should not be applied at stormwater hot spots due to the potential for groundwater contamination. All contaminated runoff should be prevented from entering municipal storm drain systems by using best management practices (BMPs) for the specific industry or activity. | 1 | Applied and Interdisciplinary Chemistry |
The name lactone derives from the ring compound called lactide, which is formed from the dehydration of 2-hydroxypropanoic acid (lactic acid) CH-CH(OH)-COOH. Lactic acid, in turn, derives its name from its original isolation from soured milk (Latin: lac, lactis). The name was coined in 1844 by the French chemist Théophile-Jules Pelouze, who first obtained it as a derivative of lactic acid. An internal dehydration reaction within the same molecule of lactic acid would have produced alpha-propiolactone, a lactone with a 3-membered ring.
In 1880 the German chemist Wilhelm Rudolph Fittig extended the name "lactone" to all intramolecular carboxylic esters. | 0 | Theoretical and Fundamental Chemistry |
This type of categorisation of drugs is from a chemical perspective and categorises them by their chemical structure. Examples of drug classes that are based on chemical structures include:
* Benzodiazepine
* Cardiac glycoside
* Fibrate
* Steroid
* Thiazide diuretic
* Triptan
* β-lactam antibiotic | 1 | Applied and Interdisciplinary Chemistry |
The AMNet consists of approximately 15 sites across the U.S. and Canada. The function of these sites is to measure ambient air concentrations of gaseous oxidized mercury (GOM), particulate bound mercury (PBM), and gaseous elemental mercury (GEM). This network works to monitor and report atmospheric mercury that causes dry and total deposition of mercury at select MDN sites. AMNet produces high-resolution data to determine atmospheric mercury trends and models, the ecological consequences of mercury discharging sources, and how to adequately control mercury levels. | 1 | Applied and Interdisciplinary Chemistry |
Rhodizonic acid is a chemical compound with formula or . It can be seen as a twofold enol and fourfold ketone of cyclohexene, more precisely 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone.
Rhodizonic acid is usually obtained in the form of a dihydrate . The latter is actually 2,3,5,5,6,6-hexahydroxycyclohex-2-ene-1,4-dione, where two of the original ketone groups are replaced by two pairs of geminal diols. The orange to deep-red and highly hygroscopic anhydrous acid can be obtained by low-pressure sublimation of the dihydrate.
Like many other enols, rhodizonic acid can lose the hydrogen cations from the hydroxyls (pK = , pK = at 25 °C), yielding the hydrogen rhodizonate anion and the rhodizonate anion . The latter is aromatic and symmetric, as the double bond and the negative charges are delocalized and evenly distributed over the six CO units. Rhodizonates tend to have various shades of red, from yellowish to purplish.
Rhodizonic acid has been used in chemical assays for barium, lead, and other metals. In particular, the sodium rhodizonate test can be used to detect gunshot residue (which contains lead) in a subject's hands, and to distinguish arrow wounds from gunshot wounds for hunting regulation enforcement. | 0 | Theoretical and Fundamental Chemistry |
Phosgene is an organic chemical compound with the formula . It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of carbonic acid, or structurally as formaldehyde with the hydrogen atoms replaced by chlorine atoms. Phosgene is a valued and important industrial building block, especially for the production of precursors of polyurethanes and polycarbonate plastics.
Phosgene is extremely poisonous and was used as a chemical weapon during World War I, where it was responsible for 85,000 deaths. It is a highly potent pulmonary irritant and quickly filled enemy trenches due to it being a heavy gas.
It is classified as a Schedule 3 substance under the Chemical Weapons Convention. In addition to its industrial production, small amounts occur from the breakdown and the combustion of organochlorine compounds, such as chloroform. | 0 | Theoretical and Fundamental Chemistry |
In civil engineering (specifically hydraulic engineering), a hydrodynamic separator (HDS) is a stormwater management device that uses cyclonic separation to control water pollution. They are designed as flow-through structures with a settling or separation unit to remove sediment and other pollutants. HDS are considered structural best management practices (BMPs), and are used to treat and pre-treat stormwater runoff. | 1 | Applied and Interdisciplinary Chemistry |
Perera is a Chartered Chemist (CChem.)by profession and a Registered Analytical Chemist of the Royal Society of Chemistry (RSC) in the United Kingdom. He is a Fellow (FRSC) of the RSC of which he is an honorary life member and the former hony. secretary / treasurer (1984–1992) of its section in Sri Lanka.
He is also a life member and a Fellow (FIChemC) of the Institute of Chemistry Ceylon and a Fellow (FIQA) of the Institute of Quality Assurance UK.
His professional career started in August 1978 as an assistant lecturer at the department of Chemistry, University of Colombo. His work thereafter in the multinational pharmaceutical manufacturing industry extended for almost 14 years, from September 1978 until July 1992.
Perera started his career in industry as a production executive with Glaxo Ceylon Limited and stayed until March 1982.
Mackwoods-Winthrop Limited then hired hm as the senior manager in charge of their quality assurance and analytical control divisions until March 1989, and thereafter as the senior manager of the newly established technical services department.
Perera then changed over to the cosmetics and healthcare industry when Hemas Manufacturing Limited invited him to join them in August 1992 as the Director – Senior Manager of quality assurance and product development.
But it was only 14 weeks service there for Perera, as a freak road accident on 12 November 1992 made him instantaneously a paraplegic for life and cut short tragically, at the age of 36, his professional career that was just blossoming out. | 0 | Theoretical and Fundamental Chemistry |
Nickel is both naturally abundant – it is the fifth most common element on earth – and widely used in industry and commercial goods. Workplace nickel exposure is common in many industries, and the performance of normal work tasks can result in nickel skin levels sufficient to elicit dermatitis. Within the workplace, individuals may be exposed to significant amounts of nickel, airborne from the combustion of fossil fuels or from contact with tools that are nickel plated. Historically, workplaces where prolonged contact with soluble nickel has been high have shown high risks for allergic contact nickel dermatitis. For example, nickel dermatitis was common in the past among nickel platers. Outbreaks of nickel allergy from consumer goods have been documented throughout the 20th century, with jewelry, stocking suspenders, and metallic buttons on blue jeans each resulting in dermatitis at the point of contact. Nickel can also be present in food and drinking water; ingestion of increased nickel is not associated with systemic allergic disease, but is associated with flare-ups of dermatitis or aggravation of vesicular hand eczema. Similarly, aggravation of dermatitis has been reported in response to nickel-containing surgical implants or dental gear.
The risk of an object eliciting nickel allergy is linked to the amount of nickel released by its surface (and not to its total nickel content). Suspected objects can be screened by wiping the surface with a 1% dimethylglyoxime solution that turns pink if more than 0.5 μg/cm per week is released by the surface. Various methods exist to test the skin or nails for nickel exposure, typically relying on wiping the skin, then quantifying the nickel on the wipe via mass spectrometry.
Dietary nickel exposure may come from high-nickel foods, possibly canned food (via the packaging), possibly stainless steel cookware (whereas some grades of stainless steel contain more nickel than others), or plumbing (especially the first water run from the tap in the morning). | 1 | Applied and Interdisciplinary Chemistry |
In ecological terms, because of its important role in biological systems, phosphate is a highly sought after resource. Once used, it is often a limiting nutrient in environments, and its availability may govern the rate of growth of organisms. This is generally true of freshwater environments, whereas nitrogen is more often the limiting nutrient in marine (seawater) environments. Addition of high levels of phosphate to environments and to micro-environments in which it is typically rare can have significant ecological consequences. For example, blooms in the populations of some organisms at the expense of others, and the collapse of populations deprived of resources such as oxygen (see eutrophication) can occur. In the context of pollution, phosphates are one component of total dissolved solids, a major indicator of water quality, but not all phosphorus is in a molecular form that algae can break down and consume.
Calcium hydroxyapatite and calcite precipitates can be found around bacteria in alluvial topsoil. As clay minerals promote biomineralization, the presence of bacteria and clay minerals resulted in calcium hydroxyapatite and calcite precipitates.
Phosphate deposits can contain significant amounts of naturally occurring heavy metals. Mining operations processing phosphate rock can leave tailings piles containing elevated levels of cadmium, lead, nickel, copper, chromium, and uranium. Unless carefully managed, these waste products can leach heavy metals into groundwater or nearby estuaries. Uptake of these substances by plants and marine life can lead to concentration of toxic heavy metals in food products. | 0 | Theoretical and Fundamental Chemistry |
TCF7L2 is the symbol officially approved by the HUGO Gene Nomenclature Committee for the Transcription Factor 7-Like 2 gene. | 1 | Applied and Interdisciplinary Chemistry |
In 1956, after a final convalescent period in the French Alps, Joliot-Curie was admitted to the Curie Hospital in Paris, where she died on 17 March at the age of 58 from leukemia, possibly due to radiation from polonium-210. Frédéric's health was also declining, and he died in 1958 from liver disease, which too was said to be the result of overexposure to radiation.
Joliot-Curie was an atheist and anti-war. When the French government held a national funeral in her honor, Irène's family asked to have the religious and military portions of the funeral omitted. Frédéric was also given a national funeral by the French government.
Joliot-Curies daughter, Hélène Langevin-Joliot, went on to become a nuclear physicist and professor at the University of Paris. Joliot-Curies son, Pierre Joliot, went on to become a biochemist at Centre National de la Recherche Scientifique. | 0 | Theoretical and Fundamental Chemistry |
Between 1995 and 2004 in the United States, an average of 1560 cold-related emergency department visits occurred per year and in the years 1999 to 2004, an average of 647 people died per year due to hypothermia. Of deaths reported between 1999 and 2002 in the US, 49% of those affected were 65 years or older and two-thirds were male. Most deaths were not work related (63%) and 23% of affected people were at home. Hypothermia was most common during the autumn and winter months of October through March. In the United Kingdom, an estimated 300 deaths per year are due to hypothermia, whereas the annual incidence of hypothermia-related deaths in Canada is 8000. | 1 | Applied and Interdisciplinary Chemistry |
There are different chemical families of corrosion inhibitors used in the oil industry, among them are the following:
Fatty Imidazolines: These are imidazole-based compounds, usually with a long unsaturated chain length, derived mainly from oleic acid. They are very effective in preventing acid corrosion of carbon steel (Figure 1).
Fatty amines: These corrosion inhibitors are organic compounds that contain an amino group and an alkyl group. They act as cathodic inhibitors and form a protective layer on the metal surface.They work efficiently against corrosion brought about by carbon dioxide (CO2) and hydrogen sulfide (H2S). Also, ethoxylated amines are widely applied for the same purpose (Figure 2).
Organic Acids: Organic acids such as acetic acid, formic aci,d and citric acid are used as corrosion inhibitors. These acids react with metal ions to form insoluble compounds that protect the metal surface. These inhibitors are often used in combination with other corrosion inhibitors and techniques, such as cathodic protection and coatings, to provide comprehensive corrosion protection. CO2 and H2S are regularly seen in oilfields and are notorious for causing corrosion of metal sections. Fortunately, they can be kept under control with measures that have been found to be effective (Figure 3).
Pyridines: Some studies have shown that certain pyridines can inhibit corrosion caused by the presence of acid gases, such as carbon dioxide and hydrogen sulfide, which are common in the oil industry. Pyridine and its derivatives have been shown to be effective inhibitors for a wide range of metals, such as carbon steel, stainless steel, and copper alloys. They act by adsorbing to the metal surface and forming a protective film, which can be physical or chemical in nature. Pyridine and its derivatives are also effective in inhibiting localized corrosion, such as pitting and crevice corrosion (Figure 4).
Azoles: Azoles, such as triazole and benzotriazole, oxazole and benzoxazoles, thioazoles, and benzothioazoles, are organic compounds used as corrosion inhibitors in the petroleum industry. They act as anodic inhibitors and form a protective layer on the metal surface (Figure 5).
Polymers: Polymers are large molecules used in the petroleum industry as corrosion inhibitors. These polymers can adsorb onto the metal surface and form a protective coating. They can also be used as dispersants to prevent the formation of corrosive deposits. Some examples are:
Aminated polymers: These polymers are used for corrosion protection of metal surfaces in the oil industry. They are highly effective in preventing salt water and hydrogen sulfide (H2S) corrosion.
Acrylic polymers: These polymers are used as corrosion inhibitors in the industry due to their good compatibility with oil and drilling fluids. They are effective against corrosion caused by the presence of hydrochloric acid (HCl) in drilling fluids.
Maleate polymers: These polymers are used as corrosion inhibitors in the industry due to their good adsorption capacity on metal surfaces and their high solubility in oil and drilling fluids. They offer protection against the corrosive effects of hydrogen sulfide (H2S) present in the drilling fluid. (Figure 6).
Other organic products used as corrosion inhibitors in the oil industry are nitriles, amides, oximes, ureas and, thioureas, and phosphonate salts. Inorganic inhibitors such as lanthanides, molybdates, silicates, boric and phosphoric acids, and combinations of nitrates and nitrites are also widely employed. Environmentally friendly inhibitors such as some biomass wastes, amino acids, and ionic liquids have been investigated.
It is critical to choose the right corrosion inhibitor based on environmental conditions (temperature, pressure, and type of metal to be protected) and to ensure that the right amount is applied for maximum protection. The corrosion progress should also be monitored periodically to adjust the dosage of the inhibitor if necessary. | 0 | Theoretical and Fundamental Chemistry |
As described in the work of E. Tenailleau and S. Akoka, an optimization of the technique parameters have enabled to reach a better accuracy for the C NMR measurements).
The C-SNIF-NMR method is called method “new frontier” because it is the first analytical method that can differentiate sugars coming from C4-metabolism plants (cane, maize, etc.) and some crassulacean acid metabolism plants (CAM-metabolism) like pineapple or agave.
This method can also be applied to tequila products, where it can differentiate authentic 100% agave tequila, misto tequila (made from at least 51% agave), and products made from a larger proportion of cane or maize sugar and therefore not complying with the legal definition of tequila.
This method will certainly have further applications in future, in the field of food and beverage analysis authenticity. | 0 | Theoretical and Fundamental Chemistry |
After Rangs resignation, the Chair of Pharmacology became vacant. The Head of department from 1983 to 1987 was Donald.H Jenkinson He had done his PhD under Bernard Katz. in UCLs famous Department of Biophysics, and was yet another member of staff who had been invited to join the Department by Heinz Schild. During his tenure the Middlesex Hospital Medical School was merged with UCL's, including the two Departments of Pharmacology.
During the 1980s the traditional role of Heads of department was replaced by rotating headships that were no longer associated necessarily with an established chair. Established chairs were, de facto, abolished as part of the move to corporatise universities.
David Colquhoun FRS was appointed to the established chair in 1985. It was subsequently dubbed the A.J. Clark chair, in honour of Clarks role in the establishment of quantitative pharmacology. His work, with statistician Alan Hawkes and Bert Sakmann (Nobel prize 1991) established the department as the world leader in the theory and experiment of single ion channels. After retiring from the A.J.Clark chair in 2004, he worked on the misinterpretation of p' values and its contribution to the irreproducibility that has come to light in some areas of science.
D. A. Brown FRS (1936 - 2023) was appointed in 1987 as head of department (he had previously held the same position at the School of Pharmacy). In 1987, the merger with the Middlesex Hospital Medical School was completed and David Brown inherited the title Astor Chair of Pharmacology from Professor F Hobbiger who had held that title at the Middlesex.
Browns appointment was intended initially to be the start of a 5-year rotating headship, but when Colquhouns turn became due, he decided that the job of Head of department would not allow enough time to do the algebra and program development with which he was involved. Donald Jenkinson likewise declined to take another turn. Luckily David Brown agreed to continue and he remained Head of department until 2002. His tenure saw a second merger, this time with the Department of Pharmacology at the Royal Free Medical School, headed by Professor Annette Dolphin, FRS. David Brown is renowned for his discovery of the acetylcholine (muscarinic)-sensitive potassium channel (M channel).
The Wellcome Lab for Molecular Pharmacology
The growing importance of molecular biology led Brown & Colquhoun to apply to the Wellcome Trust in 1990. They funded the building of the Lab for Molecular Pharmacology which Colquhoun directed until his retirement in 2004.
Trevor G. Smart became Head of department in 2002, with the title of Schild Chair of Pharmacology. He also works in the ion channel field. After the demise of the department in 2007. Smart became head of the new Research Department of Neuroscience, Physiology and Pharmacology.
Stephanie Schorge. In 2021, Professor Schorge succeeded Trevor Smart as head of the Research Department of Neuroscience, Physiology and Pharmacology. She is the first female head of pharmacology since 1905.
Stuart Cull-Candy FRS. Stuart G. Cull-Candy works on glutamate-activated ion channels. He joined the Department from UCL's Department of Biophysics and holds the Gaddum Chair of Pharmacology.
Lucia Sivilotti was appointed to the A.J. Clark chair in 2014. She has run the UCL Single Ion Channel group after Colquhouns retirement in 2004. She continued and greatly extended the work in the field of single channel kinetics. She owns the web site OneMol [http://www.onemol.org.uk/] where the groups analysis programs and publications can be downloaded. The association of the A.J. Clark chair with quantitative work on receptors has thus continued to the present day.
The first of the nationwide Research Assessment Exercises took place in 1986. The UCL Department headed the list. It continued to be rated as the top Department of Pharmacology in each of the four research assessments that followed in 1989, 1992, 1996 and 2002. But this performance was not enough to save the department. | 1 | Applied and Interdisciplinary Chemistry |
The GYG1 gene is located on the long arm of the chromosome 3, between positions 24 and 25, from base pair 148,709,194 to base pair 148,745,455.
Transcription of human glycogenin-1 is mainly initiated at 80bp and 86bp upstream the translator’s codon beginning. Transcriptions factors have different binding sites for its development, some examples are: GATA, activator protein 1 and 2 (AP-1 and AP-2), and numerous potential Octamer-1 binding sites. | 1 | Applied and Interdisciplinary Chemistry |
In organosulfur chemistry, sulfinamide is a functional group with the structure (where R = alkyl or aryl). This functionality is composed of a sulfur-carbon () and sulfur-nitrogen () single bonds, as well as a sulfur-oxygen double bond (), resulting in a tetravalent sulfur centre (in resonance with its zwitterionic form). As a non-bonding electron pair is also present on the sulfur, these compounds are also chiral. They are sometimes referred to as S-chiral sulfinamides. Sulfinamides are amides of sulfinic acid (). | 0 | Theoretical and Fundamental Chemistry |
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