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If a drug has already been identified for a target, that target is by definition druggable. If no known drugs bind to a target, then druggability is implied or predicted using different methods that rely on evolutionary relationships, 3D-structural properties or other descriptors. | 1 | Applied and Interdisciplinary Chemistry |
As dissimilatory nitrate reduction to ammonium is an anaerobic respiration process, marine microorganisms capable of performing DNRA are most commonly found in environments low in O, such as oxygen minimum zones (OMZs) in the water column, or sediments with steep O gradients.
DNRA has been documented in prokaryotes inhabiting the upper layer of marine sediments. For example, benthic sulfur bacteria in genera such as Beggiatoa and Thioploca inhabit anoxic sediments on continental shelves and obtain energy by oxidizing sulfide via DNRA. These bacteria are able to carry out DNRA using intracellular nitrate stored in vacuoles. The direct reduction of nitrate to ammonium via dissimilatory nitrate reduction, coupled with the direct conversion of ammonium to dinitrogen via Anammox, has been attributed to significant nitrogen loss in certain parts of the ocean; this DNRA-Anammox coupling by DNRA and Anammox bacteria can account for nitrate loss in areas with no detectable denitrification, such as in OMZs off the coast of Chile, Peru, and Namibia, as well as OMZs over the Omani Shelf in the Arabian Sea. While denitrification is more energetically favourable than DNRA, there is evidence that bacteria using DNRA conserve more energy than denitrifiers, allowing them to grow faster. Thus, via DNRA-Anammox coupling, bacteria using DNRA and Anammox may be stronger competitors for substrates than denitrifiers.
While dissimilatory nitrate reduction to ammonium is more commonly associated with prokaryotes, recent research has found increasing evidence of DNRA in various eukaryotic microorganisms. Of the known DNRA-capable fungal species, one is found in marine ecosystems; an isolate of ascomycete Aspergillus terreus from an OMZ of the Arabian Sea has been found to be capable of performing DNRA under anoxic conditions. Evidence of DNRA has also been found in marine foraminifers.
More recently, it has been discovered that using intracellular nitrate stores, diatoms can carry out dissimilatory nitrate reduction to ammonium, likely for short-term survival or for entering resting stages, thereby allowing them to persist in dark and anoxic conditions. However, their metabolism is probably not sustained by DNRA for long-term survival during resting stages, as these resting stages often can be much longer than their intracellular nitrate supply would last. The use of DNRA by diatoms is a possible explanation for how they can survive buried in dark, anoxic sediment layers on the ocean floor, without being able to carry out photosynthesis or aerobic respiration. Currently, DNRA is known to be carried out by the benthic diatom Amphora coffeaeformis, as well as the pelagic diatom Thalassiosira weissflogii. As diatoms are a significant source of oceanic primary production, the ability for diatoms to perform DNRA has major implications on their ecological role, as well as their role in the marine nitrogen cycle. | 1 | Applied and Interdisciplinary Chemistry |
The capacity of some compounds to change in function of the pH was known since the sixteenth century. This effect was even known before the development of acid-base theory. Those are found in a wide range of plants like roses, cornflowers, primroses and violets. Robert Boyle was the first person to describe this effect, employing plant juices (in the forms of solution and impregnated paper).
Molecular switches are most commonly used as pH indicators, which are molecules with acidic or basic properties. Their acidic and basic forms have different colors. When an acid or a base is added, the equilibrium between the two forms is displaced. | 0 | Theoretical and Fundamental Chemistry |
In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. The RNA world hypothesis holds that in the primordial soup there existed free-floating pyrimidine and purine ribonucleotides, the fundamental molecules that combine in series to form RNA. Complex molecules such as RNA must have emerged from relatively small molecules whose reactivity was governed by physico-chemical processes. RNA is composed of pyrimidine and purine nucleotides, both of which are necessary for reliable information transfer, and thus natural selection and Darwinian evolution. Becker et al. showed how pyrimidine nucleosides can be synthesized from small molecules and ribose, driven solely by wet-dry cycles. | 1 | Applied and Interdisciplinary Chemistry |
The colloidal probe technique is commonly used to measure interaction forces acting between colloidal particles and/or planar surfaces in air or in solution. This technique relies on the use of an atomic force microscope (AFM). However, instead of a cantilever with a sharp AFM tip, one uses the colloidal probe. The colloidal probe consists of a colloidal particle of few micrometers in diameter that is attached to an AFM cantilever. The colloidal probe technique can be used in the sphere-plane or sphere-sphere geometries (see figure). One typically achieves a force resolution between 1 and 100 pN and a distance resolution between 0.5 and 2 nm.
The colloidal probe technique has been developed in 1991 independently by Ducker and Butt. Since its development this tool has gained wide popularity in numerous research laboratories, and numerous reviews are available in the scientific literature.
Alternative techniques to measure force between surfaces involve the surface forces apparatus, total internal reflection microscopy, and optical tweezers techniques to with video microscopy. | 0 | Theoretical and Fundamental Chemistry |
Other methods available for the preparation of 2,3-epoxy alcohols have the advantage that they do not begin with an existing 2,3-epoxy alcohol; however, they tend to involve more steps than epoxide migration. Asymmetric dihydroxylation may be used to synthesize epoxy alcohols with high stereoselectivity, and some of the methods relying on dihydroxylation avoid the use of strongly basic conditions.
An alternative method that leads to retention of configuration at C-2 involves mesylation of an epoxy alcohol, epoxide opening, and re-closing by displacement of the mesylate. | 0 | Theoretical and Fundamental Chemistry |
In the 1990s, India stopped its research in cold fusion at the Bhabha Atomic Research Centre because of the lack of consensus among mainstream scientists and the US denunciation of the research. Yet, in 2008, the National Institute of Advanced Studies recommended that the Indian government revive this research. Projects were commenced at Chennais Indian Institute of Technology, the Bhabha Atomic Research Centre and the Indira Gandhi Centre for Atomic Research. However, there is still skepticism among scientists and, for all practical purposes, research has stalled since the 1990s. A special section in the Indian multidisciplinary journal Current Science' published 33 cold fusion papers in 2015 by major cold fusion researchers including several Indian researchers. | 0 | Theoretical and Fundamental Chemistry |
The ability of Lewis acids to coordinate to transition metals as σ-acceptor ligands was recognized as early as in the 1970s, but the so-called Z-type ligands remained curiosities until the early 2000s. Over the last decade, significant progress has been made in this area, especially via the incorporation of Lewis acid moieties into multidentate, ambiphilic ligands. The understanding of the nature and influence of metal→Z-ligand interactions has considerably improved and the scope of Lewis acids susceptible to behave as σ-acceptor ligands has been significantly extended. | 0 | Theoretical and Fundamental Chemistry |
A somatomedin receptor is a receptor which binds the somatomedins (IGFs). Somatomedin is abbreviated to IGF, in reference to insulin-like growth factor.
There are two types:
* Insulin-like growth factor 1 receptor (IGF-1R)
* Insulin-like growth factor 2 receptor (IGF-2R) | 1 | Applied and Interdisciplinary Chemistry |
Microbial protein (MP) can be created with micro-algae, bacteria, yeasts and microfungi (mycoprotein).
Examples of already available (commercialized) MP products include:
* Quorn
* Solein by Solar Foods
It can substitute meat and feed, mitigating environmental impacts of meat and other animal-based products. It could also substite animal-based protein supplements.
Researchers are working on improving the sustainability and economics of microbial protein production and on solving challenges in scaling up to industrial production. | 1 | Applied and Interdisciplinary Chemistry |
* Electrolysis of water for hydrogen production combined with solar photovoltaics using alkaline, PEM, and SOEC electrolyzers; This basic use of solar light generated electric power to separate water into hydrogen and oxygen has proven a little bit more efficient than for example hydrogen capture by steam reforming. The alkaline production technology of hydrogen has low costs and is considered mature. This has a consequence that the yield per unit of time is significantly higher than when using PEM technology. However, PEM technology has no corrosion issues and is more efficient, whereas alkaline production technology has the disadvantage of corrosion and worse efficiency. In addition to that, PEM technology has a fast start-up and simple maintenance. Though, in bulk production the alkaline hydrogen production technology is superior.
* Heliogen claims success in the use of solar heliostats used to direct sunlight to a tower, to reach temperatures over 1000°C in the production of hydrogen. Temperatures above 2500°C can thermochemically split water into hydrogen and oxygen without the use of electricity. This can be done using the heat of nuclear power plants or by adaptive solar mirror fields to redirect the sunlight to reach high temperatures needed for these thermochemical processes. However, this way of producing hydrogen is in its infancy and it has not yet been proven that this production hydrogen is profitable and efficient, because it has to compete with other, mature technologies. | 0 | Theoretical and Fundamental Chemistry |
Hari Punja, OF, OBE (born 1936) is an Indo-Fijian businessman and Chairman of Hari Punja Group of Companies. Hari Punja and Sons Limited is a very diversified (and probably the largest) company in Fiji.
Hari Punja was born in
Fiji and received his education in Fiji and Australia. He trained as a chemical engineer. Punja joined the business in 1960. He has served as a mayor of Lautoka and on a number of prestigious boards such as Fiji Broadcasting Commission and Fiji Sugar Corporation. He served as a Senator from 1996 to 1999.
Following the passage of the Media Industry Development Decree 2010 by the military regime, Punja resigned from the board of Fiji Television and sold his stake in radio company Communications Fiji Limited. | 1 | Applied and Interdisciplinary Chemistry |
When only the static magnetic field (B) is turned on, the spin will precess around it with Larmor frequency ν and the corresponding angular frequency is ω.
According to mechanics, the equation of motion of the spin J is:
where μ is the magnetic moment.
g is g-factor, which is dimensionless and reflecting the environmental effect on the spin.
Solving gives the angular frequency (Larmor frequency) with the magnetic field pointing on z-axis:
The minus sign is necessary. It reflects that the J is rotating in left-hand when the thumb is pointing as the H field.
when turned on the rotating magnetic field (B), with angular frequency ω. In the rotating frame of the rotating field, the equation of motion is:
or
if , the static field is cancelled, and the spin now precesses around H with angular frequency Rabi frequency
Since the rotating field is perpendicular to the static field, the spin in rotating frame is now able to flip between up and down.
By sweeping ω, one can obtain a maximum flipping and determine the magnetic moment. | 0 | Theoretical and Fundamental Chemistry |
Apart from being as a general tumor suppressor gene, p53 also plays an important part in regulating of metabolism. p53 activates hexokinase 2 (HK2) that converts glucose to glucose-6-phosphate (G6P) which enters glycolysis to produce ATP, or enters the pentose phosphate pathway (PPP). It therefore, supports macromolecular biosynthesis by producing reducing potential in the form of reduced Nicotinamide adenine dinucleotide phosphate (NADPH) and/or ribose that are used for nucleotide synthesis. p53 inhibits the glycolytic pathway by upregulating the expression of TP53-induced glycolysis and apoptosis regulator. Wild-type p53 supports the expression of PTEN (gene), which inhibits the PI3K pathway, thereby suppressing glycolysis. POU2F1 also cooperate with p53 in regulating the balance between oxidative and glycolytic metabolism. It provides resistance to oxidative stress that would regulates a set of genes that increase glucose metabolism and reduce mitochondrial respiration. This will provide additive force when the p53 is lost. Mutated Ras also enhances glycolysis, partly through increasing the activity of Myc and hypoxia-inducible factors. Although HIF-1 inhibits Myc, HIF-2 activates Myc causing the multiplicity of the tumor cells. | 1 | Applied and Interdisciplinary Chemistry |
The reaction occurring between double bonds and ozone is known as ozonolysis when one molecule of the gas reacts with the double bond:
The immediate result is formation of an ozonide, which then decomposes rapidly so that the double bond is cleaved. This is the critical step in chain breakage when polymers are attacked. The strength of polymers depends on the chain molecular weight or degree of polymerization, the higher the chain length, the greater the mechanical strength (such as tensile strength). By cleaving the chain, the molecular weight drops rapidly and there comes a point when it has little strength whatsoever, and a crack forms. Further attack occurs in the freshly exposed crack surfaces and the crack grows steadily until it completes a circuit and the product separates or fails. In the case of a seal or a tube, failure occurs when the wall of the device is penetrated.
The carbonyl end groups which are formed are usually aldehydes or ketones, which can oxidise further to carboxylic acids. The net result is a high concentration of elemental oxygen on the crack surfaces, which can be detected using energy-dispersive X-ray spectroscopy in the environmental SEM, or ESEM. The spectrum at left shows the high oxygen peak compared with a constant sulfur peak. The spectrum at right shows the unaffected elastomer surface spectrum, with a relatively low oxygen peak compared with the sulfur peak. | 0 | Theoretical and Fundamental Chemistry |
Compounds that contain sulfur exhibit unique chemistry due to sulfur's ability to form more bonds than oxygen, its lighter analogue on the periodic table. Substitutive nomenclature (marked as prefix in table) is preferred over functional class nomenclature (marked as suffix in table) for sulfides, disulfides, sulfoxides and sulfones. | 0 | Theoretical and Fundamental Chemistry |
Legonmycin is a compound that belongs to the pyrrolizidine backbone of naturally occurring alkaloids. Discovered by a joint team of researchers from University of Ghana, University of Aberdeen and Wuhan University, the compound was isolated from microorganisms at Legon (a suburb of Accra), and occurs in two forms; Legonmycin A and Legonmycin B. | 1 | Applied and Interdisciplinary Chemistry |
During enzyme catalytic reaction, the substrate and active site are brought together in a close proximity. This approach has various purposes. Firstly, when substrates bind within the active site the effective concentration of it significantly increases than in solution. This means the number of substrate molecules involved in the reaction is also increased. This process also reduces the desolvation energy required for the reaction to occur. In solution substrate molecules are surrounded by solvent molecules and energy is required for enzyme molecules to replace them and contact with the substrate. Since bulk molecules can be excluded from the active site this energy output can be minimised. Next, the active site is designed to reorient the substrate to reduce the activation energy for the reaction to occur. The alignment of the substrate, after binding, is locked in a high energy state and can proceed to the next step. In addition, this binding is favoured by entropy as the energy cost associated with solution reaction is largely eliminated since solvent cannot enter active site. In the end, the active site may manipulate the Molecular orbital of the substrate into a suitable orientation to reduce activation energy.
The electrostatic states of substrate and active site must be complementary to each other. A polarized negatively charged amino acid side chain will repel uncharged substrate. But if the transition state involves the formation of an ion centre then the side chain will now produce a favourable interaction. | 1 | Applied and Interdisciplinary Chemistry |
There is a negative correlation between the frequency of mimics and the "survivability" of both species involved. This implies that it is reproductively beneficial for both species if the models outnumber the mimics; this increases the negative interactions between predator and prey. | 1 | Applied and Interdisciplinary Chemistry |
Many optical applications of fused quartz exploit its wide transparency range, which can extend well into the ultraviolet and into the near-mid infrared. Fused quartz is the key starting material for optical fiber, used for telecommunications.
Because of its strength and high melting point (compared to ordinary glass), fused quartz is used as an envelope for halogen lamps and high-intensity discharge lamps, which must operate at a high envelope temperature to achieve their combination of high brightness and long life. Some high-power vacuum tubes used silica envelopes whose good transmission at infrared wavelengths facilitated radiation cooling of their incandescent anodes.
Because of its physical strength, fused quartz was used in deep diving vessels such as the bathysphere and benthoscope and in the windows of crewed spacecraft, including the Space Shuttle and International Space Station. Fused quartz was used also in composite armour development.
In the semiconductor industry, its combination of strength, thermal stability, and UV transparency makes it an excellent substrate for projection masks for photolithography. Its UV transparency also finds use as windows on EPROMs (erasable programmable read only memory), a type of non-volatile memory chip which is erased by exposure to strong ultraviolet light. EPROMs are recognizable by the transparent fused quartz (although some later models use UV-transparent resin) window which sits on top of the package, through which the silicon chip is visible, and which transmits UV light for erasing.
Due to the thermal stability and composition, it is used in 5D optical data storage and in semiconductor fabrication furnaces.
Fused quartz has nearly ideal properties for fabricating first surface mirrors such as those used in telescopes. The material behaves in a predictable way and allows the optical fabricator to put a very smooth polish onto the surface and produce the desired figure with fewer testing iterations. In some instances, a high-purity UV grade of fused quartz has been used to make several of the individual uncoated lens elements of special-purpose lenses including the Zeiss 105 mm f/4.3 UV Sonnar, a lens formerly made for the Hasselblad camera, and the Nikon UV-Nikkor 105 mm f/4.5 (presently sold as the Nikon PF10545MF-UV) lens. These lenses are used for UV photography, as the quartz glass can be transparent at much shorter wavelengths than lenses made with more common flint or crown glass formulas.
Fused quartz can be metallised and etched for use as a substrate for high-precision microwave circuits, the thermal stability making it a good choice for narrowband filters and similar demanding applications. The lower dielectric constant than alumina allows higher impedance tracks or thinner substrates. | 1 | Applied and Interdisciplinary Chemistry |
Interferome is managed by a team at Monash University :Monash Institute of Medical Research and the University of Cambridge | 1 | Applied and Interdisciplinary Chemistry |
Two adjacent structural units in a polymer molecule constitute a diad. Diads overlap: each structural unit is considered part of two diads, one diad with each neighbor. If a diad consists of two identically oriented units, the diad is called a meso diad (abbreviated m) as in a meso compound. If a diad consists of units oriented in opposition, the diad is called a racemo diad (r) as in a racemic compound. In the case of vinyl polymer molecules, a meso diad is one in which the substituents are oriented on the same side of the polymer backbone: in the Natta projection they both point into the plane, or both point out of the plane. | 0 | Theoretical and Fundamental Chemistry |
H-2 and H-6 in any 1,4-heterodisubstituted benzene are related by a mirror plane of symmetry passing through C-1 and C-4. They are therefore chemically equivalent (and magnetically equivalent by the chemical shift criterion) but, because they have different spatial and connectivity relations to H-3 (with 3-bond vs. 5-bond coupling constants of different strengths), they are magnetically inequivalent by the coupling criterion. The same is true with respect to their coupling relationships with H-5. Similarly, H-3 and H-5 are chemically equivalent but magnetically inequivalent owing to their different coupling relationships with H-2 (or H-6).
An example is provided by 4-nitroaniline. Although each signal retains the gross doublet shape predicted by first-order analysis, a close-up view of each reveals additional peaks. | 0 | Theoretical and Fundamental Chemistry |
Ferritin is a hollow globular protein of mass 474 kDa and comprising 24 subunits. Typically it has internal and external diameters of about 8 and 12 nm, respectively. The nature of these subunits varies by class of organism:
* In vertebrates, the subunits are of two types, light (L) and heavy (H), which have apparent molecular mass of 19 kDa and 21 kDa, respectively; their sequences are homologous (about 50% identical).
* Amphibians have an additional ("M") type of ferritin.
* Plants and bacteria have a single ferritin; it most closely resembles the vertebrate H-type.
* In the gastropods of the genus Lymnaea, two types have been recovered, from somatic cells and the yolk, respectively (see below).
* In the pearl oyster Pinctada fucata, an additional subunit resembling Lymnaea soma ferritin is associated with shell formation.
* In the parasite Schistosoma, two types are present: one in males, the other in females.
All the aforementioned ferritins are similar, in terms of their primary sequence, with the vertebrate H-type. In E. coli, a 20% similarity to human H-ferritin is observed.
Some ferritin complexes in vertebrates are hetero-oligomers of two highly related gene products with slightly different physiological properties. The ratio of the two homologous proteins in the complex depends on the relative expression levels of the two genes.
Inside the ferritin shell, iron ions form crystallites together with phosphate and hydroxide ions. The resulting particle is similar to ferrihydrite. Each ferritin complex can store about 4500 iron (Fe) ions.
A human mitochondrial ferritin, MtF, was found to express as a pro-protein. When a mitochondrion takes it up, it processes it into a mature protein similar to the ferritins found in the cytoplasm, which it assembles to form functional ferritin shells. Unlike other human ferritins, it appears to have no introns in its genetic code. An X-ray diffraction study has revealed that its diameter is 1.70 angstroms (0.17 nm), it contains 182 residues, and is 67% helical. The mitochondrial ferritin's Ramachandran plot shows its structure to be mainly alpha helical with a low prevalence of beta sheets. | 1 | Applied and Interdisciplinary Chemistry |
Androsterone sulfate, also known as 3α-hydroxy-5α-androstan-17-one 3α-sulfate, is an endogenous, naturally occurring steroid and one of the major urinary metabolites of androgens. It is a steroid sulfate which is formed from sulfation of androsterone by the steroid sulfotransferase SULT2A1 and can be desulfated back into androsterone by steroid sulfatase. | 1 | Applied and Interdisciplinary Chemistry |
The movement of so many chloroplast genes to the nucleus means that many chloroplast proteins that were supposed to be translated in the chloroplast are now synthesized in the cytoplasm. This means that these proteins must be directed back to the chloroplast, and imported through at least two chloroplast membranes.
Curiously, around half of the protein products of transferred genes arent even targeted back to the chloroplast. Many became exaptations, taking on new functions like participating in cell division, protein routing, and even disease resistance. A few chloroplast genes found new homes in the mitochondrial genome—most became nonfunctional pseudogenes, though a few tRNA genes still work in the mitochondrion. Some transferred chloroplast DNA protein products get directed to the secretory pathway (though many secondary plastids are bounded by an outermost membrane derived from the hosts cell membrane, and therefore topologically outside of the cell, because to reach the chloroplast from the cytosol, you have to cross the cell membrane, just like if you were headed for the extracellular space. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway).
Because the cell acquiring a chloroplast already had mitochondria (and peroxisomes, and a cell membrane for secretion), the new chloroplast host had to develop a unique protein targeting system to avoid having chloroplast proteins being sent to the wrong organelle. | 0 | Theoretical and Fundamental Chemistry |
The Dahms pathway starts as the Weimberg pathway but the 2-keto-3 deoxy-xylonate is split by an aldolase to pyruvate and glycolaldehyde. | 1 | Applied and Interdisciplinary Chemistry |
The individual hearths are lined with refractory brick, and the rabble arms are typically a force-cooled metal alloy. The entire structure is enclosed in a cylindrical brick-lined steel shell. | 1 | Applied and Interdisciplinary Chemistry |
The Macromolecular Interpenetration theory, also known as the diffusion theory, states that the mucoadhesive molecules and mucus glycoproteins mutually interact by means of interpenetration of their chains and the forming of secondary semi-permanent adhesive bonds. It is necessary that the mucoadhesive device has features or properties that favor both chemical and mechanical interactions for the macromolecular interpenetration theory to take place. Molecules that can present mucoadhesive properties are molecules with hydrogen bond building groups, high molecular weight, flexible chains, and surface active properties.
It is perceived that increase in adhesion force is associated with the degree of penetration of polymer chains. Literature states that the degree of penetration required for efficient bioadhesive bonds lies in the range of 0.2-0.5μm. The following equation can be used to estimate the degree of penetration of polymer and mucus chains:
with as contact time and as the diffusion coefficient of the mucoadhesive material in the mucus. Maximum adhesion strength is reached when penetration depth is approximately equal to polymer chain size. Properties of mutual solubility and structural similarity will improve the mucoadhesive bond. | 1 | Applied and Interdisciplinary Chemistry |
Lysine is a proteinaceous diamino acid (i.e. a component of proteins), and is accordingly coded by codons of the genetic material. In the pH range found inside living cells, both the amino groups are protonated, and they can be classified therefore as cationic amino acids.
Ornithine is a non-proteinaceous diamino acid.
In biochemistry, diamino acids are of particular interest. Diamino acids are used for the synthesis of specific peptide nucleic acids, such as daPNA. Artificial peptide nucleic acids are capable of forming duplex structures with individual DNA- and RNA-strands and are, therefore, not only called DNA-analog, but also they are considered as candidates for the first genetic material on Earth. The corresponding diamino acids such as 2,3-diaminopropanoic acid were detected in the Murchison meteorite and in a simulated comet. | 1 | Applied and Interdisciplinary Chemistry |
Latent heat storage can be achieved through changes in the state of matter from liquid→solid, solid→liquid, solid→gas and liquid→gas. However, only solid→liquid and liquid→solid phase changes are practical for PCMs. Although liquid–gas transitions have a higher heat of transformation than solid–liquid transitions, liquid→gas phase changes are impractical for thermal storage because large volumes or high pressures are required to store the materials in their gas phase. Solid–solid phase changes are typically very slow and have a relatively low heat of transformation.
Initially, solid–liquid PCMs behave like sensible heat storage (SHS) materials; their temperature rises as they absorb heat. Unlike conventional SHS materials, however, when PCMs reach their phase change temperature (their melting point) they absorb large amounts of heat at an almost constant temperature until all the material is melted. When the ambient temperature around a liquid material falls, the PCM solidifies, releasing its stored latent heat. A large number of PCMs are available in any required temperature range from −5 up to 190 °C. Within the human comfort range between 20 and 30 °C, some PCMs are very effective, storing over 200 kJ/kg of latent heat, as against a specific heat capacity of around one kJ/(kg*°C) for masonry. The storage density can therefore be 20 times greater than masonry per kg if an temperature swing of 10 °C is allowed. However, since the mass of the masonry is far higher than that of PCM this specific (per mass) heat capacity is somewhat offset. A masonry wall might have a mass of 200 kg/m, so to double the heat capacity one would require additional 10 kg/m of PCM. | 0 | Theoretical and Fundamental Chemistry |
The journal publishes original research papers that include developments in analytical techniques, studies of geological-environmental reference materials, advances in statistical analysis of geoanalytical data, as well as data compilations, contributions to the characterisation of reference materials, as well as review articles and topical commentaries. It also publishes an annual bibliographic review article of the geoanalytical literature and a biennial series of critical reviews of analytical developments. | 0 | Theoretical and Fundamental Chemistry |
In this biological process, which is a redox comproportionation reaction, nitrite and ammonium ions are converted directly into a diatomic molecule of nitrogen and water.
: (ΔG° = ).
Globally, this process may be responsible for 30–50% of the gas produced in the oceans. It is thus a major sink for fixed nitrogen and so limits oceanic primary productivity.
The bacteria that perform the anammox process belong to the bacterial phylum Planctomycetota. Currently, five anammox genera have been discovered: Brocadia, Kuenenia, Anammoxoglobus, Jettenia (all fresh water species), and Scalindua (marine species). The anammox bacteria are characterized by several striking properties:
* They all possess one anammoxosome, a membrane bound compartment inside the cytoplasm which is the locus of anammox catabolism. Further, the membranes of these bacteria mainly consist of ladderane lipids so far unique in biology.
* Of special interest is the conversion to hydrazine (normally used as a high-energy rocket fuel, and poisonous to most living organisms) as an intermediate.
* A final striking feature of the organism is the extremely slow growth rate; the doubling time is anywhere from 7–22 days.
The anammox bacteria are geared towards converting their substrates at very low concentrations; in other words, they have a very high affinity to their substrates ammonium and nitrite (sub-micromolar range). Anammox cells are packed with cytochrome c type proteins (≈30% of the protein complement), including the enzymes that perform the key catabolic reactions of the anammox process, making the cells remarkably red. The anammox process was originally found to occur only from 20 °C to 43 °C but more recently, anammox has been observed at temperatures from 36 °C to 52 °C in hot springs and 60 °C to 85 °C at hydrothermal vents located along the Mid-Atlantic Ridge. | 1 | Applied and Interdisciplinary Chemistry |
Thrombin is in the serine protease family. It has 3 binding domains in which thrombin-inhibition drugs bind to. Those proteases have a deep narrow gap as an active binding site that consists of two β-barrel subdomains that make up the surface gap which binds substrate peptides. The surface in the gap seems to have limiting access to molecules by steric hindrance, this binding site consists of 3 amino acids, Asp-102, His-57 and Ser-195. Thrombin also has two exosites (1 and 2). Thrombin is a little different from other serine proteases as exosite 1 is anion-binding and binds to fibrin and other similar substrates while exosite 2 is a heparin-binding domain. | 1 | Applied and Interdisciplinary Chemistry |
Wet granulation is a process of using a liquid binder to lightly agglomerate the powder mixture. The amount of liquid has to be properly controlled, as over-wetting will cause the granules to be too hard and under-wetting will cause them to be too soft and friable. Aqueous solutions have the advantage of being safer to deal with than solvent-based systems but may not be suitable for drugs which are degraded by hydrolysis.
;Procedure
# The active ingredient and excipients are weighed and mixed.
# The wet granulate is prepared by adding the liquid binder–adhesive to the powder blend and mixing thoroughly. Examples of binders/adhesives include aqueous preparations of cornstarch, natural gums such as acacia, cellulose derivatives such as methyl cellulose, gelatin, and povidone.
# Screening the damp mass through a mesh to form pellets or granules.
# Drying the granulation. A conventional tray-dryer or fluid-bed dryer are most commonly used.
# After the granules are dried, they are passed through a screen of smaller size than the one used for the wet mass to create granules of uniform size.
Low shear wet granulation processes use very simple mixing equipment, and can take a considerable time to achieve a uniformly mixed state. High shear wet granulation processes use equipment that mixes the powder and liquid at a very fast rate, and thus speeds up the manufacturing process. Fluid bed granulation is a multiple-step wet granulation process performed in the same vessel to pre-heat, granulate, and dry the powders. It is used because it allows close control of the granulation process. | 1 | Applied and Interdisciplinary Chemistry |
TOXMAP was a geographic information system (GIS) from the United States National Library of Medicine (NLM) that was deprecated on December 16, 2019. The application used maps of the United States to help users explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory (TRI) and Superfund programs with visual projections and maps. | 1 | Applied and Interdisciplinary Chemistry |
Confusion arises from the different meanings of the term "disulfide". Molybdenum disulfide (MoS) consists of separated sulfide centers, in association with molybdenum in the formal +4 oxidation state (that is, Mo and two S). Iron disulfide (pyrite, FeS) on the other hand consists of , or S–S dianion, in association with divalent iron in the formal +2 oxidation state (ferrous ion: Fe). Dimethyldisulfide has the chemical binding CH–S–S–CH, whereas carbon disulfide has no S–S bond, being S=C=S (linear molecule analog to CO). Most often in sulfur chemistry and in biochemistry, the disulfide term is commonly ascribed to the sulfur analogue of the peroxide –O–O– bond. The disulfide bond (–S–S–) plays a major role in the conformation of proteins and in the catalytic activity of enzymes. | 0 | Theoretical and Fundamental Chemistry |
The oxidation of propionyl-CoA to form pyruvate is influenced by its necessity in Mycobacterium tuberculosis. Accumulation of propionyl-CoA can lead to toxic effects. In Mycobacterium tuberculosis, it has been suggested that the metabolism of propionyl-CoA is involved in cell wall biogenesis. A lack of such catabolism would therefore increase the susceptibility of the cell to various toxins, particularly to macrophage antimicrobial mechanisms. Another hypothesis regarding the fate of propionyl-CoA, in M. tuberculosisis, is that since propionyl-CoA is produced by beta odd chain fatty acid catabolism, the methylcitrate cycle is activated subsequently to negate any potential toxicity, acting as a buffering mechanism. | 1 | Applied and Interdisciplinary Chemistry |
Organic compounds featuring two or more 2- and 3-aminocarboxylate groups are ligands of extensive use in nature, industry, and research. Famous examples include EDTA and NTA. | 0 | Theoretical and Fundamental Chemistry |
The Si-V center is a single-hole (spin-1/2) system with ground and excited electronic states located within the diamond bandgap. The ground and excited electronic states have two orbital states split by spin–orbit coupling. Each of these spin–orbit states is doubly degenerate by spin, and this splitting can be affected by lattice strain. Phonons in the diamond lattice drive transitions between these orbital states, causing rapid equilibration of the orbital population at temperatures above ca. 1 K.
All four transitions between the two ground and two excited orbital states are dipole allowed with a sharp zero-phonon line (ZPL) at 738 nm (1.68 eV) and minimal phononic sideband in a roughly 20 nm window around 766 nm. The Si-V center emits much more of its emission into its ZPL, approximately 70% (Debye–Waller factor of 0.7), than most other optical centers in diamond, such as the nitrogen-vacancy center (Debye–Waller factor ~ 0.04). The Si-V center also has higher excited states that relax quickly to the lowest excited states, allowing off-resonant excitation.
The Si-V center has an inversion symmetry, and no static electric dipole moment (to the first order); it is therefore insensitive to the Stark shift that could result from inhomogeneous electric fields within the diamond lattice. This property, together with the weak electron-phonon coupling, results in a narrow ZPL in the Si-V center, which is mostly limited by its intrinsic lifetime. Bright photoluminescence, narrow optical lines, and ease of finding optically indistinguishable Si-V centers favor them for applications in solid-state quantum optics. | 0 | Theoretical and Fundamental Chemistry |
Molar refractivity, , is a measure of the total polarizability of a mole of a substance and is dependent on the temperature, the index of refraction, and the pressure.
The molar refractivity is defined as
where is the Avogadro constant and is the mean polarizability of a molecule.
Substituting the molar refractivity into the Lorentz-Lorenz formula gives, for gasses
where is the refractive index, is the pressure of the gas, is the universal gas constant, and is the (absolute) temperature. For a gas, , so the molar refractivity can be approximated by
In SI units, has units of J mol K, has units K, has no units, and has units of Pa, so the units of are m mol.
In terms of density ρ, molecular weight M, it can be shown that: | 0 | Theoretical and Fundamental Chemistry |
Currently, it is highly unlikely that the presence of unexpected or even unknown GMOs will be detected, since either the DNA sequence of the transgene or its product, the protein, must be known for detection. In addition, even testing for known GMOs is time-consuming and costly, as current reliable detection methods can test for only one GMO at a time. Therefore, research programmes such as Co-Extra are developing improved and alternative testing methods, for example DNA microarrays. | 1 | Applied and Interdisciplinary Chemistry |
Silver ions have been shown to have potent antibacterial activity, and have been shown to affect the growth of Gram-positive and Gram-negative bacteria. This is due to their ability to form ligand complexes with proteins or enzymes in bacterial cells. Due to this unique property, these nanofoams create excellent air filters designed to filter out bacteria and other microorganisms, this level of filtration was shown to be more effective than tradition HCl analogues.
These silver nanofoams have also been used as electrocatalysts for the reduction reaction of to CO. It was found that on average silver nanofoams can maintain over 90% FECO in a wide potential window (−0.5 to −1.2 VRHE), enabling the maximum CO selective current density of 33 mA cm−2 and the mass activity of 23.5 A gAg−1, which are the highest values among recently reported metal foam-based electrocatalysts. | 0 | Theoretical and Fundamental Chemistry |
There are many different pharmaceutical drugs that can produce adverse effects after biotransformation, interaction with alternate targets, or through drug-drug interactions. All pharmaceuticals can be toxic, depending on the dose. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a carbodiimide (systematic IUPAC name: methanediimine) is a functional group with the formula RN=C=NR. On Earth they are exclusively synthetic, but in interstellar space the parent compound HN=C=NH has been detected by its maser emissions.
A well known carbodiimide is dicyclohexylcarbodiimide, which is used in peptide synthesis. Dialkylcarbodiimides are stable. Some diaryl derivatives tend to convert to dimers and polymers upon standing at room temperature, though this mostly occurs with low melting point carbodiimides that are liquids at room temperature. Solid diaryl carbodiimides are more stable, but can slowly undergo hydrolysis in the presence of water over time. | 0 | Theoretical and Fundamental Chemistry |
The previous derivations assumed that there is only one species, A, adsorbing onto the surface. This section considers the case when there are two distinct adsorbates present in the system. Consider two species A and B that compete for the same adsorption sites. The following hypotheses are made here:
# All the sites are equivalent.
# Each site can hold at most one molecule of A, or one molecule of B, but not both simultaneously.
# There are no interactions between adsorbate molecules on adjacent sites.
As derived using kinetic considerations, the equilibrium constants for both A and B are given by
and
The site balance states that the concentration of total sites [S] is equal to the sum of free sites, sites occupied by A and sites occupied by B:
Inserting the equilibrium equations and rearranging in the same way we did for the single-species adsorption, we get similar expressions for both θ and θ: | 0 | Theoretical and Fundamental Chemistry |
Drosha shares striking structural similarity with the downstream ribonuclease Dicer, suggesting an evolutionary relationship, though Drosha and related enzymes are found only in animals while Dicer relatives are widely distributed, including among protozoans. Both components of the microprocessor complex are conserved among the vast majority of metazoans with known genomes. Mnemiopsis leidyi, a ctenophore, lacks both Drosha and DGCR8 homologs, as well as recognizable miRNAs, and is the only known metazoan with no detectable genomic evidence of Drosha. In plants, the miRNA biogenesis pathway is somewhat different; neither Drosha nor DGCR8 has a homolog in plant cells, where the first step in miRNA processing is usually executed by a different nuclear ribonuclease, DCL1, a homolog of Dicer.
It has been suggested based on phylogenetic analysis that the key components of RNA interference based on exogenous substrates were present in the ancestral eukaryote, likely as an immune mechanism against viruses and transposable elements. Elaboration of this pathway for miRNA-mediated gene regulation is thought to have evolved later. | 1 | Applied and Interdisciplinary Chemistry |
Nanocrystalline materials can be prepared in several ways. Methods are typically categorized based on the phase of matter the material transitions through before forming the nanocrystalline final product. | 1 | Applied and Interdisciplinary Chemistry |
Fuculose or 6-deoxy-tagatose is a ketohexose deoxy sugar. Fuculose is involved in the process of sugar metabolism. -Fuculose can be formed from -fucose by -fucose isomerase and converted to L-fuculose-1-phosphate by -fuculose kinase. | 1 | Applied and Interdisciplinary Chemistry |
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape (conformation) and reactivity of ions and molecules. Steric effects complement electronic effects, which dictate the shape and reactivity of molecules. Steric repulsive forces between overlapping electron clouds result in structured groupings of molecules stabilized by the way that opposites attract and like charges repel. | 0 | Theoretical and Fundamental Chemistry |
There are numerous mosses or bog habitats in Scotland, many of them situated also in Aberdeenshire, including the Cookney Moss, Leuchar Moss and Red Moss of Netherley nearby. There are also many other shires within Scotland that contain mosses such as Fife, Angus, Morayshire and Lanarkshire. Some of these are lowland bogs and others, like Portlethen Moss, are raised bogs. There are other similar acidic peat bogs in the northern part of North America, Russia and northern Europe, but in those locations they are usually called "bogs". | 1 | Applied and Interdisciplinary Chemistry |
Block copolymers can "microphase separate" to form periodic nanostructures, such as styrene-butadiene-styrene block copolymer. The polymer is known as Kraton and is used for shoe soles and adhesives. Owing to the microfine structure, transmission electron microscope or TEM was used to examine the structure. The butadiene matrix was stained with osmium tetroxide to provide contrast in the image. The material was made by living polymerization so that the blocks are almost monodisperse to create a regular microstructure. The molecular weight of the polystyrene blocks in the main picture is 102,000; the inset picture has a molecular weight of 91,000, producing slightly smaller domains.
Microphase separation is a situation similar to that of oil and water. Oil and water are immiscible (i.e., they can phase separate). Due to the incompatibility between the blocks, block copolymers undergo a similar phase separation. Since the blocks are covalently bonded to each other, they cannot demix macroscopically like water and oil. In "microphase separation," the blocks form nanometer-sized structures. Depending on the relative lengths of each block, several morphologies can be obtained. In diblock copolymers, sufficiently different block lengths lead to nanometer-sized spheres of one block in a matrix of the second (e.g., PMMA in polystyrene). Using less different block lengths, a "hexagonally packed cylinder" geometry can be obtained. Blocks of similar length form layers (often called lamellae in the technical literature). Between the cylindrical and lamellar phase is the gyroid phase. The nanoscale structures created from block copolymers can potentially be used to create devices for computer memory, nanoscale-templating, and nanoscale separations. Block copolymers are sometimes used as a replacement for phospholipids in model lipid bilayers and liposomes for their superior stability and tunability.
Polymer scientists use thermodynamics to describe how the different blocks interact. The product of the degree of polymerization, n, and the Flory-Huggins interaction parameter, , gives an indication of how incompatible the two blocks are and whether they will microphase separate. For example, a diblock copolymer of symmetric composition will microphase separate if the product is greater than 10.5. If is less than 10.5, the blocks will mix and microphase separation is not observed. The incompatibility between the blocks also affects the solution behavior of these copolymers and their adsorption behavior on various surfaces.
Block copolymers are able to self-assemble in selective solvents to form micelles among other structures.
In thin films, block copolymers are of great interest as masks in the lithographic patterning of semiconductor materials for applications in high density data storage. A key challenge is to minimise the feature size and much research is in progress on this. | 0 | Theoretical and Fundamental Chemistry |
The Michaelis–Becker reaction is the reaction of a hydrogen phosphonate with a base, followed by a nucleophilic substitution of phosphorus on a haloalkane, to give an alkyl phosphonate. Yields of this reaction are often lower than the corresponding Michaelis–Arbuzov reaction. | 0 | Theoretical and Fundamental Chemistry |
The Canadian Headache Society guideline for migraine prophylaxis recommends, based on low-quality evidence, that 300 mg of CoQ be offered as a choice for prophylaxis. | 1 | Applied and Interdisciplinary Chemistry |
Testing for gold with acid capitalizes on gold's status as a noble metal, resistant to corrosion, oxidation, or acid. The procedure includes rubbing the gold-colored item on black stone, leaving a visible mark. The mark undergoes scrutiny by applying nitric acid, which dissolves the mark of any item not gold, stainless steel, zinc, tungsten, aluminum, platinum, or palladium. If the mark persists, further testing involves aqua regia (nitric acid and hydrochloric acid). If the mark dissolves, the item proves to be genuine gold. More precise assessment of fineness or purity is achieved using varying strengths of aqua regia and comparative testing against known fineness. | 0 | Theoretical and Fundamental Chemistry |
Stable isotope ratios can be used to infer the environmental conditions during the formation of sedimentary rock. Using stoichiometry and knowledge of redox pathways, paleogeologists can use isotopes ratios of elements to determine the chemical composition of the water and sediments when burial occurred.
Sulfur isotopes are frequently used to look for evidence of ancient euxinia. Low δS in black shales and sedimentary rocks provides positive evidence for euxinic formation conditions. The pyrite (FeS) in euxinic basins typically has higher concentrations of light sulfur isotopes than pyrite in the modern ocean. The reduction of sulfate to sulfide favors the lighter sulfur isotopes (S) and becomes depleted in the heavier isotopes (S). This lighter sulfide then bonds with Fe to form FeS which is then partially preserved in the sediments. In most modern systems, sulfate eventually becomes limiting, and the isotopic weights of sulfur in both sulfate and sulfide (preserved as FeS) become equal.
Molybdenum (Mo), the most common transition metal ion in modern seawater, is also used to look for evidence for euxinia. Weathering of rocks provides an input of MoO into oceans. Under oxic conditions, MoO is very unreactive, but in modern euxinic environments such as the Black Sea, molybdenum precipitates out as oxythiomolybdate (MoOS ). The isotope ratio for Molybdenum (δ Mo) in euxinic sediments appears to be higher than in oxic conditions. Additionally, the concentration of molybdenum is frequently correlated with the concentration of organic matter in euxinic sediments. The use of Mo to indicate euxinia is still under debate. | 0 | Theoretical and Fundamental Chemistry |
The tricarboxylic acid cycle (TCA) and glutaminolysis can also be targeted for cancer treatment, since they are essential for the survival and proliferation of cancer cells. Ivosidenib and Enasidenib, two FDA-approved cancer treatments, can arrest the TCA cycle of cancer cells by inhibiting isocitrate dehydrogenase-1 (IDH1) and isocitrate dehydrogenase-2 (IDH2), respectively. Ivosidenib is specific to acute myeloid leukemia (AML) and cholangiocarcinoma, whereas Enasidenib is specific to just acute myeloid leukemia (AML).
In a clinical trial consisting of 185 adult patients with cholangiocarcinoma and an IDH-1 mutation, there was a statistically significant improvement (p<0.0001; HR: 0.37) in patients randomized to Ivosidenib. Still, some of the adverse side effects in these patients included fatigue, nausea, diarrhea, decreased appetite, ascites, and anemia. In a clinical trial consisting of 199 adult patients with AML and an IDH2 mutation, 23% of patients experienced complete response (CR) or complete response with partial hematologic recovery (CRh) lasting a median of 8.2 months while on Enasidenib. Of the 157 patients who required transfusion at the beginning of the trial, 34% no longer required transfusions during the 56-day time period on Enasidenib. Of the 42% of patients who did not require transfusions at the beginning of the trial, 76% still did not require a transfusion by the end of the trial. Side effects of Enasidenib included nausea, diarrhea, elevated bilirubin and most notably, differentiation syndrome.
Glutaminase (GLS), the enzyme responsible for converting glutamine to glutamate via hydrolytic deamidation during the first reaction of glutaminolysis, can also be targeted. In recent years, many small molecules, such as azaserine, acivicin, and CB-839 have been shown to inhibit glutaminase, thus reducing cancer cell viability and inducing apoptosis in cancer cells. Due to its effective antitumor ability in several cancer types such as ovarian, breast and lung cancers, CB-839 is the only GLS inhibitor currently undergoing clinical studies for FDA-approval. | 1 | Applied and Interdisciplinary Chemistry |
In 2001, Gal Bitan, Aleksey Lomakin, and David B. Teplow applied PICUP to study amyloid β-protein (Aβ) oligomerization, which is observed in Alzheimer's disease. PICUP allowed for identifying and quantifying the Aβ oligomers that are metastable because of its ability to rapidly cross-link. Coupling PICUP with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), the distribution of oligomers in rapid equilibrium was quantified. This application allowed for the study of amyloidogenic proteins associated with neurodegenerative diseases and opened doors for possible future therapeutic mechanisms. Neurodegenerative diseases are currently suggested to be the result of neurotoxic proteins, so the ability to study their oligomer distribution is effective in understanding how and under what conditions these oligomers are formed. | 1 | Applied and Interdisciplinary Chemistry |
* Metal - Free Synthetic Organic Dyes, Ghodsi Mohammadi Ziarani, Razieh Moradi, Negar Lashgari, Hendrik G. Kruger, Elsevier 2018, ISBN 9780128156476 | 0 | Theoretical and Fundamental Chemistry |
Butyric acid (; from , meaning "butter"), also known under the systematic name butanoic acid, is a straight-chain alkyl carboxylic acid with the chemical formula . It is an oily, colorless liquid with an unpleasant odor. Isobutyric acid (2-methylpropanoic acid) is an isomer. Salts and esters of butyric acid are known as butyrates or butanoates. The acid does not occur widely in nature, but its esters are widespread. It is a common industrial chemical and an important component in the mammalian gut. | 1 | Applied and Interdisciplinary Chemistry |
Altszyler et al. (2017) have shown that these ultrasensitivity measures can be linked by the following equation:
where denoted the mean value of the variable x over the range [a,b]. | 1 | Applied and Interdisciplinary Chemistry |
Nature can be used to provide important services for communities by protecting them against flooding or excessive heat, or helping to improve air, soil and water quality. When nature is harnessed by people and used as an infrastructural system it is called “green infrastructure”. Many such efforts take as their model prairies, where absorbent soil prevents runoff and vegetation filters out pollutants. Green infrastructure occurs at all scales. It is most often associated with green stormwater management systems, which are smart and cost-effective. However, green infrastructure acts as a supplemental component to other related concepts, and ultimately provides an ecological framework for social, economic, and environmental health of the surroundings. | 1 | Applied and Interdisciplinary Chemistry |
In 2005 and again in 2011, the compound was prepared by total synthesis together with the unstrained compound riccardin C. In 2013, several other syntheses were reported for it and a racemic synthesis. | 0 | Theoretical and Fundamental Chemistry |
A stereogenic center (or stereocenter) is an atom such that swapping the positions of two ligands (connected groups) on that atom results in a molecule that is stereoisomeric to the original. For example, a common case is a tetrahedral carbon bonded to four distinct groups a, b, c, and d (Cabcd), where swapping any two groups (e.g., Cbacd) leads to a stereoisomer of the original, so the central C is a stereocenter. Many chiral molecules have point chirality, namely a single chiral stereogenic center that coincides with an atom. This stereogenic center usually has four or more bonds to different groups, and may be carbon (as in many biological molecules), phosphorus (as in many organophosphates), silicon, or a metal (as in many chiral coordination compounds). However, a stereogenic center can also be a trivalent atom whose bonds are not in the same plane, such as phosphorus in P-chiral phosphines (PRR′R″) and sulfur in S-chiral sulfoxides (OSRR′), because a lone-pair of electrons is present instead of a fourth bond.
Similarly, a stereogenic axis (or plane) is defined as an axis (or plane) in the molecule such that the swapping of any two ligands attached to the axis (or plane) gives rise to a stereoisomer. For instance, the C-symmetric species 1,1′-bi-2-naphthol (BINOL) and 1,3-dichloroallene have stereogenic axes and exhibit axial chirality, while (E)-cyclooctene and many ferrocene derivatives bearing two or more substituents have stereogenic planes and exhibit planar chirality.
Chirality can also arise from isotopic differences between atoms, such as in the deuterated benzyl alcohol PhCHDOH; which is chiral and optically active ([α] = 0.715°), even though the non-deuterated compound PhCHOH is not.
If two enantiomers easily interconvert, the pure enantiomers may be practically impossible to separate, and only the racemic mixture is observable. This is the case, for example, of most amines with three different substituents (NRR′R″), because of the low energy barrier for nitrogen inversion.
It is not necessary for the chiral substance to have a stereogenic element. Examples include certain helicenes, calixarenes and fullerenes, which have inherent chirality. Moreover, it is possible for a molecule to have a center of chirality that sits in a position that does not correspond to an atom. Such a molecule may be chiral without having any stereogenic centers. Examples include 1,3,5(,7)-substituted adamantanes such as (1S,3R,5R,7S)-3-methyl-5-phenyladamantane-1-carboxylic acid (pictured).
When the optical rotation for an enantiomer is too low for practical measurement, the species is said to exhibit cryptochirality.
Chirality is an intrinsic part of the identity of a molecule, so the systematic name includes details of the absolute configuration (R/S, , or other designations). | 0 | Theoretical and Fundamental Chemistry |
Nucleosides are molecules formed by attaching a nucleobase to a ribose or deoxyribose ring. Examples of these include cytidine (C), uridine (U), adenosine (A), guanosine (G), and thymidine (T).
Nucleosides can be phosphorylated by specific kinases in the cell, producing nucleotides.
Both DNA and RNA are polymers, consisting of long, linear molecules assembled by polymerase enzymes from repeating structural units, or monomers, of mononucleotides. DNA uses the deoxynucleotides C, G, A, and T, while RNA uses the ribonucleotides (which have an extra hydroxyl(OH) group on the pentose ring) C, G, A, and U. Modified bases are fairly common (such as with methyl groups on the base ring), as found in ribosomal RNA or transfer RNAs or for discriminating the new from old strands of DNA after replication.
Each nucleotide is made of an acyclic nitrogenous base, a pentose and one to three phosphate groups. They contain carbon, nitrogen, oxygen, hydrogen and phosphorus. They serve as sources of chemical energy (adenosine triphosphate and guanosine triphosphate), participate in cellular signaling (cyclic guanosine monophosphate and cyclic adenosine monophosphate), and are incorporated into important cofactors of enzymatic reactions (coenzyme A, flavin adenine dinucleotide, flavin mononucleotide, and nicotinamide adenine dinucleotide phosphate). | 0 | Theoretical and Fundamental Chemistry |
Typical genera include:
* Citrobacter are peritrichous facultative anaerobic bacilli between 0.6–6 μm in length. Citrobacter species inhabit intestinal flora without causing harm, but can lead to urinary tract infections, bacteremia, brain abscesses, pneumonia, intra abdominal sepsis, meningitis, and joint infections if they are given the opportunity. Infections of a Citrobacter species has a mortality rate between 33–48%, with infants and immunocompromised individuals being more susceptible.
* Enterobacter are motile, flagellated bacilli known for causing infections such as bacteremia, respiratory tract infections, urinary tract infections, infections of areas where surgery occurred, and in extreme cases meningitis, sinusitis and osteomyelitis. To determine the presence of Enterobacter in a sample, they are first grown on MacConkey agar to confirm they are lactose fermenting. An indole test will differentiate Enterobacter from Escherichia, as Enterobacter are indole negative and Escherichia is positive. Enterobacter are distinguished from Klebsiella because of their differences in motility.
* Klebsiella are non-motile, Gram-negative bacilli ranging from 1–2 μm in length. They are facultative anaerobes with a capsule composed of complex acid polysaccharides that allows them to withstand drying for several months. Klebsiella pneumoniae is the most common Klebsiella species found in humans, the gastrointestinal tracts of animals, in sewage and in soil. On carbohydrate-rich media, Klebsiella colonies appear greyish-white in colour with a mucosal outer surface. The media used for selecting for Klebsiella species in a mixed sample is an agar including ornithine, raffinose, and Koser citrate, where members of this genus will form yellow, wet-looking colonies.
* Escherichia species normally inhabit the human intestine and those of other warm-blooded animals, and are the most commonly responsible for causing disease in humans. E. coli specifically is the most common organism seen in the human intestine and are known to cause a variety of diseases in humans. Most E. coli strains are motile and have obtained many of their virulence features from horizontal gene transfer. There are several different pathotypes of E. coli causing gastrointestinal syndromes: diarrheagenic E. coli (DEC), enterotoxigenic E. coli (ETEC); EPEC; Shiga toxin–producingE. coli (STEC), which includes EHEC; enteroaggregative E. coli (EAEC); and enteroinvasive E. coli (EIEC). There are different ways to identify E. coli based on variation of their O, H and K polysaccharides on their cell surface or by using selective medias.
Escherichia coli (E. coli) can be distinguished from most other coliforms by its ability to ferment lactose at 44 °C in the fecal coliform test, and by its growth and color reaction on certain types of culture media. When cultured on an eosin methylene blue (EMB) plate, a positive result for E. coli is metallic green colonies on a dark purple medium. Also can be cultured on Tryptone Bile X-Glucuronide (TBX) to appear as blue or green colonies after incubation period of 24 hours. Escherichia coli have an incubation period of 12–72 hours with the optimal growth temperature being 37 °C. Unlike the general coliform group, E. coli are almost exclusively of fecal origin and their presence is thus an effective confirmation of fecal contamination. Most strains of E. coli are harmless, but some can cause serious illness in humans. Infection symptoms and signs include bloody diarrhea, stomach cramps, vomiting and occasionally, fever. The bacteria can also cause pneumonia, other respiratory illnesses and urinary tract infections.
An easy way to differentiate between different types of coliform bacteria is by using an eosin methylene blue agar plate. This plate is partially inhibitory to Gram (+) bacteria, and will produce a color change in the Gram (-) bacterial colonies based on lactose fermentation abilities. Strong lactose fermenters will appear as dark blue/purple/black, and E.coli (which also ferments lactose) colonies will be dark colored, but will also appear to have a metallic green sheen. Other coliform bacteria will appear as thick, slimy colonies, with non-fermenters being colorless, and weak fermenters being pink. | 0 | Theoretical and Fundamental Chemistry |
* To increase pulmonary compliance.
* To prevent atelectasis (collapse of the alveoli or atriums) at the end of expiration.
* To facilitate recruitment of collapsed airways.
Alveoli can be compared to gas in water, as the alveoli are wet and surround a central air space. The surface tension acts at the air-water interface and tends to make the bubble smaller (by decreasing the surface area of the interface). The gas pressure (P) needed to keep an equilibrium between the collapsing force of surface tension (γ) and the expanding force of gas in an alveolus of radius r is expressed by the Young–Laplace equation: | 0 | Theoretical and Fundamental Chemistry |
Many different illnesses can cause an increase in metabolic activity as the body combats illness and disease in order to heal itself.
Hypermetabolism is a common symptom of various pathologies. Some of the most prevalent diseases characterized by hypermetabolism are listed below.
* Hyperthyroidism: Manifestation: An overactive thyroid often causes a state of increased metabolic activity.
* Friedreich's ataxia: Manifestation: Local cerebral metabolic activity is increased extensively as the disease progresses.
* Fatal familial insomnia: Manifestation: Hypermetabolism in the thalamus occurs and disrupts sleep spindle formation that occurs there.
* Graves' disease: Manifestation: Excess hypermetabolically-induced thyroid hormone activates sympathetic pathways, causing the eyelids to retract and remain constantly elevated.
* Anorexia and bulimia: Manifestation: The prolonged stress put on the body as a result of these eating disorders forces the body into starvation mode. Some patients recovering from these disorders experience hypermetabolism until they resume normal diets.
* Astrocytoma: Manifestation: Causes hypermetabolic lesions in the brain | 1 | Applied and Interdisciplinary Chemistry |
The timeline of physical chemistry lists the sequence of physical chemistry theories and discoveries in chronological order. | 1 | Applied and Interdisciplinary Chemistry |
Chelation therapy is an antidote for poisoning by mercury, arsenic, and lead. Chelating agents convert these metal ions into a chemically and biochemically inert form that can be excreted. Chelation using calcium disodium EDTA has been approved by the U.S. Food and Drug Administration (FDA) for serious cases of lead poisoning. It is not approved for treating "heavy metal toxicity". Although beneficial in cases of serious lead poisoning, use of disodium EDTA (edetate disodium) instead of calcium disodium EDTA has resulted in fatalities due to hypocalcemia. Disodium EDTA is not approved by the FDA for any use, and all FDA-approved chelation therapy products require a prescription. | 0 | Theoretical and Fundamental Chemistry |
Alkylation is the addition of alkyl groups to molecules, often by alkylating agents such as alkyl halides.
Alkylating antineoplastic agents are a class of compounds that are used to treat cancer. In such case, the term alkyl is used loosely. For example, nitrogen mustards are well-known alkylating agents, but they are not simple hydrocarbons.
In chemistry, alkyl is a group, a substituent, that is attached to other molecular fragments. For example, alkyl lithium reagents have the empirical formula Li(alkyl), where alkyl = methyl, ethyl, etc. A dialkyl ether is an ether with two alkyl groups, e.g., diethyl ether . | 0 | Theoretical and Fundamental Chemistry |
TPV cells have been proposed as auxiliary power conversion devices for capture of otherwise lost heat in other power generation systems, such as steam turbine systems or solar cells. | 0 | Theoretical and Fundamental Chemistry |
Not all amino acid replacements have the same effect on function or structure of protein. The magnitude of this process may vary depending on how similar or dissimilar the replaced amino acids are, as well as on their position in the sequence or the structure. Similarity between amino acids can be calculated based on substitution matrices, physico-chemical distance, or simple properties such as amino acid size or charge (see also amino acid chemical properties). Usually amino acids are thus classified into two types:
* Conservative replacement - an amino acid is exchanged into another that has similar properties. This type of replacement is expected to rarely result in dysfunction in the corresponding protein .
* Radical replacement - an amino acid is exchanged into another with different properties. This can lead to changes in protein structure or function, which can cause potentially lead to changes in phenotype, sometimes pathogenic. A well known example in humans is sickle cell anemia, due to a mutation in beta globin where at position 6 glutamic acid (negatively charged) is exchanged with valine (not charged). | 1 | Applied and Interdisciplinary Chemistry |
To date, ATM techniques have utilized THz time-domain spectroscopy (THz-TDS) because of historical scarcity of strong THz sources and highly sensitive THz detectors that operate at room temperature. Many samples of interest contain large amounts of water that strongly absorb THz radiation, thus requiring a very strong THz source. This requirement is exacerbated when attempting to use highly sensitive THz detectors that conventionally require supercooling to liquid helium temperatures. Worse, the need for supercooling these detectors has made THz detection unavailable to many researchers around the world due to recent sharp rises in the price of liquid helium due to its scarcity.
To circumvent THz detection hurdles, THz-TDS is utilized as it requires commonly available infrared detectors sensitive in the near infrared region of the electromagnetic spectrum — most commonly around a wavelength of 800 nm. In this case, an electro-optic (EO) crystal, such as gallium nitride (GaN), zinc telluride (ZnTe), is commonly used to detect changes in the THz light after it has passed through a sample. The polarization properties of a synchronized infrared beam of light passing through the EO crystal are changed. This polarization change is detected by an infrared detector, called a [https://www.rp-photonics.com/balanced_photodetection.html balanced detector], that compares the magnitude of two perpendicular polarization components of the infrared beam.
Until more powerful THz sources that provide a wide frequency range and more sensitive room temperature THz detectors are realized, THz-TDS remains a reliable technique for ATM.
The THz-TDS techniques used in ATM may be divided into two categories: rotated sample and stationary sample. Historically, the former technique involved rotation of the sample at the focus of a THz beam while the detector is placed far from the sample in the far-field. For many mechanical reasons, however, a stationary sample technique is preferred. In stationary sample ATM, a polarized THz beam is rotated through 360° in a plane perpendicular to the propagation direction of the beam and typically utilizes a near-field detection scheme in which the sample is mounted in direct contact with an EO crystal that is subsequently analyzed by the infrared beam in a THz-TDS configuration. | 0 | Theoretical and Fundamental Chemistry |
The shutter in the closed position fits within the window casement. This was the prevalent approach in the Colonies from New York and south. An advantage is the additional security because the shutters can not be lifted from the pintles in the closed position. A disadvantage is that the shutters must be matched closely to the inside dimension of the casing and the shutter rabbet should match the thickness of the shutters.
Any surface mounted hinge and pintle can be used, assuming there is sufficient width to the casing to accept the pintle. The hinge has a minimal standoff and the pintle would have the same matching standoff. Together an offset of 1–1½ inches will hold the shutter at the same distance from the structure and not quite parallel to the wall. | 1 | Applied and Interdisciplinary Chemistry |
Magnetic isotope effects arise when a chemical reaction involves spin-selective processes, such as the radical pair mechanism. The result is that some isotopes react preferentially, depending on their nuclear spin quantum number I. This is in contrast to more familiar mass-dependent isotope effects. | 0 | Theoretical and Fundamental Chemistry |
The anion is prepared by treatment of phosphorus pentachloride with tetrachlorocatechol followed by a tertiary amine gives the anion:
:PCl + 3 CCl(OH) → H[P(OCCl)] + 5 HCl
:H[P(OCCl)] + BuN → BuNH [P(OCCl)]
Using a chiral amine, the anion can be readily resolved. | 0 | Theoretical and Fundamental Chemistry |
In the fields of medicine, biotechnology, and pharmacology, drug discovery is the process by which new drugs are discovered.
Historically, drugs were discovered by identifying the active ingredient from traditional remedies or by serendipitous discovery. Later chemical libraries of synthetic small molecules, natural products, or extracts were screened in intact cells or whole organisms to identify substances that have a desirable therapeutic effect in a process known as classical pharmacology. Since sequencing of the human genome which allowed rapid cloning and synthesis of large quantities of purified proteins, it has become common practice to use high throughput screening of large compound libraries against isolated biological targets which are hypothesized to be disease-modifying in a process known as reverse pharmacology. Hits from these screens are then tested in cells and then in animals for efficacy. Even more recently, scientists have been able to understand the shape of biological molecules at the atomic level and to use that knowledge to design (see drug design) drug candidates.
Modern drug discovery involves the identification of screening hits, medicinal chemistry, and optimization of those hits to increase the affinity, selectivity (to reduce the potential of side effects), efficacy/potency, metabolic stability (to increase the half-life), and oral bioavailability. Once a compound that fulfills all of these requirements has been identified, it will begin the process of drug development prior to clinical trials. One or more of these steps may, but not necessarily, involve computer-aided drug design.
Despite advances in technology and understanding of biological systems, drug discovery is still a lengthy, "expensive, difficult, and inefficient process" with a low rate of new therapeutic discovery. In 2010, the research and development cost of each new molecular entity (NME) was approximately US$1.8 billion. Drug discovery is done by pharmaceutical companies, sometimes with research assistance from universities. The "final product" of drug discovery is a patent on the potential drug. The drug requires very expensive Phase I, II, and III clinical trials, and most of them fail. Small companies have a critical role, often then selling the rights to larger companies that have the resources to run the clinical trials.
Drug discovery is different from Drug Development. Drug Discovery is often considered the process of identifying new medicine. At the same time, Drug development is delivering a new drug molecule into clinical practice. In its broad definition, this encompasses all steps from the basic research process of finding a suitable molecular target to supporting the drug's commercial launch. | 1 | Applied and Interdisciplinary Chemistry |
The Montreal Protocol targeted 1,1,1-trichloroethane as one of those compounds responsible for ozone depletion and banned its use beginning in 1996. Since then, its manufacture and use have been phased out throughout most of the world. Its atmospheric presence has declined rapidly due to its relatively short atmospheric lifetime of about 5 years. | 1 | Applied and Interdisciplinary Chemistry |
These proteins are synthesized in the cell bodies of the supraoptic and paraventricular regions of the hypothalamus.
The disulfide-rich neurophysin protein is suggested to be congruent with the synthesis of insulin in which a precursor molecule of higher molecular weight is proteolytically cleaved and forms disulfide linkages.
Although not enough data has been obtained, it is hypothesized that there is a common precursor molecule between neurophysin and the two hormones it stabilizes. | 1 | Applied and Interdisciplinary Chemistry |
No applications have been identified for ferrocene-containing dendrimers. They exhibit multielectron redox indicating that the ferrocenyl moieties are essentially noninteracting redox centers. | 0 | Theoretical and Fundamental Chemistry |
The Serine octamer cluster in physical chemistry is an unusually stable cluster consisting of eight serine molecules (Ser) implicated in the origin of homochirality. This cluster was first discovered in mass spectrometry experiments. Electrospray ionization of an aerosol of serine in methanol results in a mass spectrum with a prominent ion peak of 841 corresponding to the Ser+H cation. The smaller and larger clusters are virtually absent in the spectrum and therefore the number 8 is called a magic number. The same octamer ions are also produced by rapid evaporation of a serine solution on a hot (200-250 °C) metal surface or by sublimation of solid serine. After production, detection again is by mass-spectroscopic means. For the discussion of homochirality, these laboratory production methods are designed to mimic prebiotic conditions.
The cluster is not only unusually stable but also unusual because the clusters have a strong homochiral preference. A racemic serine solution produces a minimum amount of cluster and with solutions of both enantiomers a maximum amount is formed of both homochiral D-Ser and L-Ser. In another experiment cluster formation of a racemic mixture with deuterium enriched L-serine results in a product distribution with hardly any 50/50 D/L clusters but a preference for either D or L enantioenriched clusters.
A model for chiral amplification is proposed whereby enantioenriched clusters are formed from a non-racemic mixture already enriched by L-serine as a result of a mirror-symmetry breaking process. Cluster formation is followed by isolation and on subsequent dissociation of the cluster a serene solution forms with a higher concentration of L-serine than in the original mixture. A cycle can be maintained in which each turn results in an incremental enrichment in L-serine. Many such cycles eventually result in enantiopure L-serine. This model has been experimentally verified.
Chiral transmission is assumed to take place through so-called substitution reactions of serine clusters. In these reactions, a serine monomer in a cluster can be replaced by another small biologically relevant molecule. For instance Ser reacts with glucose (Glc) to the Ser + Glc + Na cluster. Moreover, the cluster of synthetic L-glucose with Ser is less abundant than that with the biological D-glucose. | 0 | Theoretical and Fundamental Chemistry |
Mg is the coordinating metal ion in the chlorophyll molecule, and in plants where the ion is in high supply about 6% of the total Mg is bound to chlorophyll. Thylakoid stacking is stabilised by Mg and is important for the efficiency of photosynthesis, allowing phase transitions to occur.
Mg is probably taken up into chloroplasts to the greatest extent during the light-induced development from proplastid to chloroplast or etioplast to chloroplast. At these times, the synthesis of chlorophyll and the biogenesis of the thylakoid membrane stacks absolutely require the divalent cation.
Whether Mg is able to move into and out of chloroplasts after this initial developmental phase has been the subject of several conflicting reports. Deshaies et al. (1984) found that Mg did move in and out of isolated chloroplasts from young pea plants, but Gupta and Berkowitz (1989) were unable to reproduce the result using older spinach chloroplasts. Deshaies et al. had stated in their paper that older pea chloroplasts showed less significant changes in Mg content than those used to form their conclusions. The relative proportion of immature chloroplasts present in the preparations may explain these observations.
The metabolic state of the chloroplast changes considerably between night and day. During the day, the chloroplast is actively harvesting the energy of light and converting it into chemical energy. The activation of the metabolic pathways involved comes from the changes in the chemical nature of the stroma on the addition of light. H is pumped out of the stroma (into both the cytoplasm and the lumen) leading to an alkaline pH. Mg (along with K) is released from the lumen into the stroma, in an electroneutralisation process to balance the flow of H. Finally, thiol groups on enzymes are reduced by a change in the redox state of the stroma. Examples of enzymes activated in response to these changes are fructose 1,6-bisphosphatase, sedoheptulose bisphosphatase and ribulose-1,5-bisphosphate carboxylase. During the dark period, if these enzymes were active a wasteful cycling of products and substrates would occur.
Two major classes of the enzymes that interact with Mg in the stroma during the light phase can be identified. Firstly, enzymes in the glycolytic pathway most often interact with two atoms of Mg. The first atom is as an allosteric modulator of the enzymes' activity, while the second forms part of the active site and is directly involved in the catalytic reaction. The second class of enzymes includes those where the Mg is complexed to nucleotide di- and tri-phosphates (ADP and ATP), and the chemical change involves phosphoryl transfer. Mg may also serve in a structural maintenance role in these enzymes (e.g., enolase). | 1 | Applied and Interdisciplinary Chemistry |
Initially, fifteen companies signed agreements with FRI and grew to 37 by the first stockholder meeting in November 1952. Membership continued to grow to a peak of 94 companies in 1995. Membership declined thereafter to 67 in 2008, primarily due to mergers. At first, nearly all members were U. S. companies; but by 2008 a majority of the members were not based in the U. S. | 1 | Applied and Interdisciplinary Chemistry |
The Okorokov effect () or resonant coherent excitation, occurs when heavy ions move in crystals under channeling conditions. V. Okorokov predicted this effect in 1965 and it was first observed by Sheldon Datz in 1978. | 0 | Theoretical and Fundamental Chemistry |
Environmental engineering is a professional engineering discipline related to environmental science. It encompasses broad scientific topics like chemistry, biology, ecology, geology, hydraulics, hydrology, microbiology, and mathematics to create solutions that will protect and also improve the health of living organisms and improve the quality of the environment. Environmental engineering is a sub-discipline of civil engineering and chemical engineering. While on the part of civil engineering, the Environmental Engineering is focused mainly on Sanitary Engineering.
Environmental engineering applies scientific and engineering principles to improve and maintain the environment to protect human health, protect nature's beneficial ecosystems, and improve environmental-related enhancement of the quality of human life.
Environmental engineers devise solutions for wastewater management, water and air pollution control, recycling, waste disposal, and public health. They design municipal water supply and industrial wastewater treatment systems, and design plans to prevent waterborne diseases and improve sanitation in urban, rural and recreational areas. They evaluate hazardous-waste management systems to evaluate the severity of such hazards, advise on treatment and containment, and develop regulations to prevent mishaps. They implement environmental engineering law, as in assessing the environmental impact of proposed construction projects.
Environmental engineers study the effect of technological advances on the environment, addressing local and worldwide environmental issues such as acid rain, global warming, ozone depletion, water pollution and air pollution from automobile exhausts and industrial sources.
Most jurisdictions impose licensing and registration requirements for qualified environmental engineers. | 1 | Applied and Interdisciplinary Chemistry |
With diffusion together with a uniform flow with velocity in the lateral direction, the autocorrelation is:
where is the average residence time if there is only a flow (no diffusion). | 0 | Theoretical and Fundamental Chemistry |
Cold vapour atomic fluorescence spectroscopy (CVAFS) is a subset of the analytical technique known as atomic fluorescence spectroscopy (AFS). | 0 | Theoretical and Fundamental Chemistry |
Another application is in radiochemistry, where this may refer to isotopic ratios or isotopic abundances. Mathematically, the isotopic abundance is
where N are the number of atoms of the isotope of interest and N is the total number of atoms, while the atomic ratio is
For example, the isotopic ratio of deuterium (D) to hydrogen (H) in heavy water is roughly (corresponding to an isotopic abundance of 0.00014%). | 0 | Theoretical and Fundamental Chemistry |
Oxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre. Oxidative addition is often a step in catalytic cycles, in conjunction with its reverse reaction, reductive elimination. | 0 | Theoretical and Fundamental Chemistry |
miCLIP (Methylation induced crosslinking immunoprecipitation) was used to detect NSUN2 targets, which were found to be mostly non-coding RNAs such as tRNA. An induced mutation of C271A in NSUN2 inhibits release of enzyme from RNA target. This mutation was over-expressed in the cells of interest, and the mutated NSUN2 was also tagged with the Myc epitope. The covalently linked RNA-protein complexes are isolated via immunoprecipitation for a Myc-specific antibody. These complexes are confirmed and detected by radiolabeling with phosphorus-32. The RNA is then extracted from the complex, reverse-transcribed, amplified with PCR, and sequenced using next-generation platforms.
Both miCLIP and Aza-IP, though limited by specific targeting of enzymes, can allow for the detection of low-abundance methylated RNA without deep sequencing. | 1 | Applied and Interdisciplinary Chemistry |
In 1993, the IUPAC proposed the shorter name "dalton" (with symbol "Da") for the unified atomic mass unit. As with other unit names such as watt and newton, "dalton" is not capitalized in English, but its symbol, "Da", is capitalized. The name was endorsed by the International Union of Pure and Applied Physics (IUPAP) in 2005.
In 2003 the name was recommended to the BIPM by the Consultative Committee for Units, part of the CIPM, as it "is shorter and works better with [SI] prefixes". In 2006, the BIPM included the dalton in its 8th edition of the SI brochure of formal definitions as a non-SI unit accepted for use with the SI. The name was also listed as an alternative to "unified atomic mass unit" by the International Organization for Standardization in 2009. It is now recommended by several scientific publishers, and some of them consider "atomic mass unit" and "amu" deprecated. In 2019, the BIPM retained the dalton in its 9th edition of the SI brochure, while dropping the unified atomic mass unit from its table of non-SI units accepted for use with the SI, but secondarily notes that the dalton (Da) and the unified atomic mass unit (u) are alternative names (and symbols) for the same unit. | 0 | Theoretical and Fundamental Chemistry |
Most eukaryotic cells have mitochondria, which produce ATP from reactions of oxygen with products of the citric acid cycle, fatty acid metabolism, and amino acid metabolism. At the inner mitochondrial membrane, electrons from NADH and FADH pass through the electron transport chain to oxygen, which provides the energy driving the process as it is reduced to water. The electron transport chain comprises an enzymatic series of electron donors and acceptors. Each electron donor will pass electrons to an acceptor of higher redox potential, which in turn donates these electrons to another acceptor, a process that continues down the series until electrons are passed to oxygen, the terminal electron acceptor in the chain. Each reaction releases energy because a higher-energy donor and acceptor convert to lower-energy products. Via the transferred electrons, this energy is used to generate a proton gradient across the mitochondrial membrane by "pumping" protons into the intermembrane space, producing a state of higher free energy that has the potential to do work. This entire process is called oxidative phosphorylation since ADP is phosphorylated to ATP by using the electrochemical gradient that the redox reactions of the electron transport chain have established driven by energy-releasing reactions of oxygen. | 1 | Applied and Interdisciplinary Chemistry |
Scientists agree that the event that separated myoglobin from hemoglobin occurred after lampreys diverged from jawed vertebrates. This separation of myoglobin and hemoglobin allowed for the different functions of the two molecules to arise and develop: myoglobin has more to do with oxygen storage while hemoglobin is tasked with oxygen transport. The α- and β-like globin genes encode the individual subunits of the protein. The predecessors of these genes arose through another duplication event also after the gnathosome common ancestor derived from jawless fish, approximately 450–500 million years ago. Ancestral reconstruction studies suggest that the preduplication ancestor of the α and β genes was a dimer made up of identical globin subunits, which then evolved to assemble into a tetrameric architecture after the duplication. The development of α and β genes created the potential for hemoglobin to be composed of multiple distinct subunits, a physical composition central to hemoglobins ability to transport oxygen. Having multiple subunits contributes to hemoglobins ability to bind oxygen cooperatively as well as be regulated allosterically. Subsequently, the α gene also underwent a duplication event to form the HBA1 and HBA2 genes. These further duplications and divergences have created a diverse range of α- and β-like globin genes that are regulated so that certain forms occur at different stages of development.
Most ice fish of the family Channichthyidae have lost their hemoglobin genes as an adaptation to cold water. | 0 | Theoretical and Fundamental Chemistry |
The thylakoid ATP synthase is a CF1FO-ATP synthase similar to the mitochondrial ATPase. It is integrated into the thylakoid membrane with the CF1-part sticking into the stroma. Thus, ATP synthesis occurs on the stromal side of the thylakoids where the ATP is needed for the light-independent reactions of photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
One aim of the Manhattan Project was increasing the availability of concentrated radioactive and stable isotopes, in particular C, S, P, and deuterium for heavy water. Harold Urey, Nobel laureate physical chemist known for his discovery of deuterium, became its head of isotope separation research while a professor at Columbia University. In 1945, he joined The Institute for Nuclear Studies at the University of Chicago, where he continued to work with chemist Jacob Bigeleisen and physicist Maria Mayer, both also veterans of isotopic research in the Manhattan Project. In 1946, Urey delivered the Liversidge lecture at the then-Royal Institute of Chemistry, where he outlined his proposed model of stable isotope fractionation. Bigeleisen and Mayer had been working on similar work since at least 1944 and, in 1947, published their model independently from Urey. Their calculations were mathematically equivalent to a 1943 derivation of the reduced partition function by German physicist Ludwig Waldmann. | 0 | Theoretical and Fundamental Chemistry |
* Ekman transport leads to coastal upwelling, which provides the nutrient supply for some of the largest fishing markets on the planet and can impact the stability of the Antarctic Ice Sheet by pulling warm deep water onto the continental shelf. Wind in these regimes blows parallel to the coast (such as along the coast of Peru, where the wind blows out of the southeast, and also in California, where it blows out of the northwest). From Ekman transport, surface water has a net movement of 90° to right of wind direction in the northern hemisphere (left in the southern hemisphere). Because the surface water flows away from the coast, the water must be replaced with water from below. In shallow coastal waters, the Ekman spiral is normally not fully formed and the wind events that cause upwelling episodes are typically rather short. This leads to many variations in the extent of upwelling, but the ideas are still generally applicable.
* Ekman transport is similarly at work in equatorial upwelling, where, in both hemispheres, a trade wind component towards the west causes a net transport of water towards the pole, and a trade wind component towards the east causes a net transport of water away from the pole.
* On smaller scales, cyclonic winds induce Ekman transport which causes net divergence and upwelling, or Ekman suction, while anti-cyclonic winds cause net convergence and downwelling, or Ekman pumping
* Ekman transport is also a factor in the circulation of the ocean gyres and garbage patches. Ekman transport causes water to flow toward the center of the gyre in all locations, creating a sloped sea-surface, and initiating geostrophic flow (Colling p 65). Harald Sverdrup applied Ekman transport while including pressure gradient forces to develop a theory for this (see Sverdrup balance). | 1 | Applied and Interdisciplinary Chemistry |
Butterfly wings possess not only ultra-hydrophobic trait but also directional adhesive characteristics. If the water bead is along the radial outward (RO) direction from the body’s central axis, it rolls off and cleans the dirt away, leading to self-cleaning. On the other hand, if droplets stand against the opposite direction, they are pinned at the surface, leading adhesion and securing the flight stability of the butterfly by preventing deposit of dirt on the wings near the center of the body. SEM micrographs of wings exhibit hierarchy along the RO direction, arising from aligned microgrooves, covered by fine lamella-stacking nanostripes. | 0 | Theoretical and Fundamental Chemistry |
The slow block to polyspermy in the sea urchin is mediated by the PIP secondary messenger system. Activation of the binding receptors activates PLC, which cleaves PIP in the egg plasma membrane, releasing IP into the egg cell cytoplasm. IP diffuses to the ER, where it opens Ca channels. | 1 | Applied and Interdisciplinary Chemistry |
Nitrile ylides can be obtained by the addition of electrophilic carbenes to nitriles, by the photochemical ring opening of azirines and by dehydrochlorination of imidoyl chlorides. The latter is the most reliable method. | 0 | Theoretical and Fundamental Chemistry |
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