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Binary ethylenimine (BEI) is a preparation of aziridine. It can be produced by heating bromoethylamine hydrobromide or 2-aminoethyl hydrogen sulfate in the presence of sodium hydroxide (Gabriel method). It contains at least one three-membered ring which is very reactive because of the ring strain.
It is used to inactivate the foot-and-mouth disease virus in vaccines for cattle, as well as other viruses and mycoplasma in blood samples.
Contrary to early assumptions that ethylenimines only modified nucleic acids, it was found that trimeric ethylenimine also alters proteins in virus preparations, especially at higher pH values. The modification of the proteins affected viral particle uptake into cells. This should be taken into consideration when using BEI and other ethyleneimines as well. | 0 | Organic Chemistry |
In 2010, Dunne was elected a Fellow of the Royal Academy of Engineering (FREng). In 2016, he was awarded the Institute of Materials, Minerals and Mining (IoM3) Harvey Flower Titanium Prize. In 2017, Dunnes Engineering Alloys team shared the Imperial Presidents Award for Outstanding Research Team with Professor Chris Phillips’s team. | 8 | Metallurgy |
In type II reactions, the Sens* transfers its energy directly with O via a radiation-less transition to create O. O then adds to the substrate in a variety of ways including: cycloadditions (most commonly [4+2]), addition to double bonds to yield 1,2-dioxetanes, and ene reactions with olefins. | 5 | Photochemistry |
Ethylene receptors are functionally similar to bacterial two-component system which has two activation sites named response regulator and histidine kinase. The cytoplasmic carboxy-terminal part of ethylene receptor is similar in amino acid sequence to these response regulator and histidine kinase in bacteria; although the N-terminal region is altogether different. Such genetic and protein relationships indicate that receptors and bacterial two-component receptors as well as phytochromes and cytokinin receptors in plants evolved from and were acquired by plants from a cyanobacterium that gave rise to plastids, the power organelles in plants and protists.
Phylogenetic analysis also shows the common origin of the ethylene receptor in plants and ethylene-binding domain in cyanobacteria. In 2016, Randy F. Lacey and Brad M. Binder at the University of Tennessee discovered that a cyanobacterium, Synechocystis sp. PCC 6803 response to ethylene signal and has a functional ethylene receptor, which they named Synechocystis Ethylene Response1 (SynEtr1). They further showed that SynEtr1 acts similar to plant ethylene receptor in binding ethylene, indicating the origin of ethylene receptor from Synechocystis-related cyanobacterium. The functional difference however is that kinase activity is not compulsory for ethylene binding in plants, but is the key role of SynEtr1. | 1 | Biochemistry |
Oxidative deamination is a form of deamination that generates α-keto acids and other oxidized products from amine-containing compounds, and occurs primarily in the liver. Oxidative deamination is stereospecific, meaning it contains different stereoisomers as reactants and products; this process is either catalyzed by L or D- amino acid oxidase and L-amino acid oxidase is present only in the liver and kidney. Oxidative deamination is an important step in the catabolism of amino acids, generating a more metabolizable form of the amino acid, and also generating ammonia as a toxic byproduct. The ammonia generated in this process can then be neutralized into urea via the urea cycle.
Much of the oxidative deamination occurring in cells involves the amino acid glutamate, which can be oxidatively deaminated by the enzyme glutamate dehydrogenase (GDH), using NAD or NADP as a coenzyme. This reaction generates α-ketoglutarate (α-KG) and ammonia. Glutamate can then be regenerated from α-KG via the action of transaminases or aminotransferase, which catalyze the transfer of an amino group from an amino acid to an α-keto acid. In this manner, an amino acid can transfer its amine group to glutamate, after which GDH can then liberate ammonia via oxidative deamination. This is a common pathway during amino acid catabolism.
Another enzyme responsible for oxidative deamination is monoamine oxidase, which catalyzes the deamination of monoamines via addition of oxygen. This generates the corresponding ketone- or aldehyde-containing form of the molecule, and generates ammonia. Monoamine oxidases MAO-A and MAO-B play vital roles in the degradation and inactivation of monoamine neurotransmitters such as serotonin and epinephrine. Monoamine oxidases are important drug targets, targeted by MAO inhibitors (MAOIs) such as selegiline. Glutamate dehydrogenase play an important role in oxidative deamination. | 1 | Biochemistry |
It is used to determine the ability of an organism to produce mixed acids by fermentation of glucose and to overcome the buffering capacity of the medium. | 3 | Analytical Chemistry |
The simplest equation for the rate of an enzyme-catalysed reaction as a function of the substrate concentration is the Michaelis-Menten equation, which can be written as follows:
in which is the rate at substrate saturation (when approaches infinity, or limiting rate, and is the value of at half-saturation, i.e. for , known as the Michaelis constant. Eadie and Hofstee independently transformed this into straight-line relationships, as follows: Taking reciprocals of both sides of the equation gives the equation underlying the Lineweaver–Burk plot:
: ·
This can be rearranged to express a different straight-line relationship:
: ·
which shows that a plot of against is a straight line with intercept on the ordinate, and slope (Hofstee plot). In the Eadie plot the axes are reversed, but the principle is the same. These plots are kinetic versions of the Scatchard plot used in ligand-binding experiments. | 1 | Biochemistry |
Regular pulses of glucocorticoids, mainly cortisol in the case of humans, are released regularly from the adrenal cortex following a circadian pattern in addition to their release as a part of the stress response. Cortisol release follows a high frequency of pulses forming an ultradian rhythm, with amplitude being the primary variation in its release, so that the signal is amplitude modulated. Glucocorticoid pulsatlity has been observed to follow a circadian rhythm, with highest levels observed before waking and before anticipated mealtimes. This pattern in amplitude of release is observed to be consistent across vertebrates. Studies done in humans, rats, and sheep have also observed a similar circadian pattern of release of adrenocorticotropin (ACTH) shortly preceding the pulse in the resulting corticosteroid. It is currently hypothesized that the observed pulsatility of ACTH and glucocorticoids is driven via pulsatility of corticotropin-releasing hormone (CRH), however there exists little data to support this due to difficulty in measuring CRH. | 1 | Biochemistry |
Electric sonic amplitude or electroacoustic sonic amplitude is an electroacoustic phenomenon that is the reverse to colloid vibration current. It occurs in colloids, emulsions and other heterogeneous fluids under the influence of an oscillating electric field. This field moves particles relative to the liquid, which generates ultrasound.
Electric sonic amplitude was experimentally discovered by Oja and co-authors in the early 1980s. It is also widely used for characterizing zeta potential in dispersions and emulsions. There is review of the theory of this effect, its experimental verification, and multiple applications published by Hunter. | 7 | Physical Chemistry |
Faulds worked as a postdoctoral researcher for on the detection of DNA using surface-enhanced resonant Raman spectroscopy (SERRS). She became increasingly interested in the use of analytical chemistry to improve people's lives. Faulds was appointed as a lecturer in 2006.
Faulds was promoted to Reader in 2012 and Professor in 2015. Faulds works on the development of surface-enhanced Raman spectroscopy (SERS) for analytical detection. SERSs permits multiplexed and sensitive biological analysis. Her work uses signal amplification methods for the quantitative analysis of biomolecules, as the sensitivity allows her to detect target DNA and proteins. SERS also allows Faulds to make multiple measurements of different analytes in one sample. In 2015 she was the first woman and youngest person to ever be elected chair of the Infrared and Raman Discussion Group (IRDG). She has described C. V. Raman as her "hero of spectroscopy".
Her recent work has looked at the optical detection of Listeria using bionanosensors. The bionanosensors permit the multiplexed detection of pathogens, which can remove the risk of infectious diseases without the need for antimicrobial drugs. She covers SERS active magnetic nanoparticles with lectins, which can recognise and bind to carbohydrates in bacteria. These nanoparticles can collect and concentrate bacteria from production lines. Silver nanoparticles are functionalised with a biorecognition molecule, such as an aptamer, and Raman reporter, resulting in a SERS signal when a nanoparticle binds to the bacterial target. The magnetic component can then be studied further using portable Raman spectrometers.
Faulds is a founding member of Renishaw plc diagnostics, a University of Strathclyde spin-off company, and serves as its Director of Research. Faulds joined the editorial board of RSC Advances in November 2016 and as Associate Editor of Analyst in August 2020. She co-directs the Engineering and Physical Sciences Research Council (EPSRC) and Medical Research Council (MRC) Centre for Doctoral Training (CDT) in Optical Medical Imaging, shared between the University of Edinburgh and the University of Strathclyde. | 3 | Analytical Chemistry |
The targeted DamID (TaDa) approach uses the phenomenon of ribosome reinitiation to express Dam-fusion proteins at appropriately low levels for DamID (i.e. Dam is non-saturating, thus avoiding toxicity). This construct can be combined with cell-type specific promoters resulting in tissue-specific methylation. This approach can be used to assay transcription factor binding in a cell type of interest or alternatively, dam can be fused to Pol II subunits to determine binding of RNA polymerase and thus infer cell-specific gene expression. Targeted DamID has been demonstrated in Drosophila and mouse cells. | 1 | Biochemistry |
PECO may be useful in treating both air and water, as well as producing hydrogen as a source of renewable energy. | 5 | Photochemistry |
Existing metabolic networks control the movement of molecules through their enzymatic steps by regulating enzymes that catalyze irreversible reactions. The movement of molecules through reversible steps is generally unregulated by enzymes, but rather regulated by the concentration of products and reactants. Irreversible reactions at regulated steps of a pathway have a negative free energy change, thereby promoting spontaneous reactions in one direction only. Reversible reactions have no or very small free energy change. As a result, the movement of molecules through a metabolic network is governed by simple chemical equilibria (at reversible steps), with specific key enzymes that are subject to regulation (at irreversible steps). This enzymatic regulation may be indirect, in the case of an enzyme being regulated by some cell signalling mechanism (like phosphorylation), or it may be direct, as in the case of allosteric regulation, where metabolites from a different portion of a metabolic network bind directly to and affect the catalytic function of other enzymes in order to maintain homeostasis.
A result that may seem at first counter intuitive, is that regulated steps tends to have small flux control coefficients. The reason is that these steps are part of a control system that stabilizes fluxes, hence a perturbation in the activity of a regulated step will inevitably trigger the control system to resist the perturbation, hence the flux control coefficients will tend to be small. This explains why, for example, that phosphofructokinase in glycolysis has such as small flux control coefficient. | 1 | Biochemistry |
The entire process of rolling hairpin replication, which has distinct, sequential stages, can be summarized as follows:
*1. The coding portion of the genome is replicated, starting from the 3′-end of the 3′ hairpin, which acts as a primer, and continues until the newly synthesized strand is connected to the 5′-end of the 5′ hairpin, producing a duplex DNA molecule that has two strands of the coding portion of the genome.
*2. mRNA that encodes the viral replication initiator protein is transcribed and subsequently translated to synthesize the protein.
*3. The initiator protein binds to and cleaves the DNA within a region called the origin, which results in the hairpin unfolding into a linear, extended form. At the same time, the initiator protein establishes a replication fork with its helicase activity.
*4. The extended-form hairpin is replicated to create an inverted copy of the telomere on the newly synthesized strand.
*5. The two strands of that end refold back into two hairpins, which repositions the replication fork to switch templates and move in the opposite direction.
*6. DNA replication continues in a linear manner from one end to the other using the opposite strand as a template.
*7. Upon reaching the other end, that end's hairpin is unfolded and refolded to replicate the terminus and once again swap templates and change the direction of replication. This back-and-forth replication is continually repeated, producing a concatemer of multiple copies of the genome.
*8. The viral initiator protein periodically excises individual genomic strands of DNA from the replicative concatemer.
*9. Excised ssDNA genomes are packaged into newly constructed viral capsids. | 1 | Biochemistry |
The water vapor, carbon dioxide and other products can be separated via gas chromatography and analysed via a thermal conductivity detector. | 0 | Organic Chemistry |
Tactic and stereoselective polymerizations are traditionally catalyzed by metal-organic complexes. Topochemical polymerization provides an additional choice. In addition, by changing the alignment of the monomer within the crystal, the tacticity/stereochemistry of the polymer product could be easily controlled. An intuitive example is shown in the figure. In topochemical polymerization of 1,3-diene carboxylic acid derivatives, polymers with four different configurations can be prepared. Their structural relationships with the monomer packing are also shown in the figure. | 7 | Physical Chemistry |
User submission to the database is encouraged. To contribute to the database, one must submit: contact info, PubMed identifier and the two molecules that interact. The person who submits a record is the owner of it. All records are validated before being made public and BIND is curated for quality assurance. BIND curation has two tracks: high-throughput (HTP) and low-throughput (LTP). HTP records are from papers which have reported more than 40 interaction results from one experimental methodology. HTP curators typically have a bioinformatics backgrounds. The HTP curators are responsible for the collection of storage of experimental data and they also create scripts to update BIND based on new publications. LTP records are curated by individuals with either an MSc or PhD and laboratory experience in interaction research. LTP curators are given further training through the Canadian Bioinformatics Workshops. Information on small molecule chemistry is curated separately by chemists to ensure the curator is knowledgeable about the subject. The priority for BIND curation is to focus on LTP to collect information as it is published. Although, HTP studies provide more information at once, there are more LTP studies being reported and similar numbers of interactions are being reported by both tracks. In 2004, BIND collected data from 110 journals. | 1 | Biochemistry |
Evans married Tommie Johnson in 1967. They had two children. Evans died on March 24, 2001, in Chapel Hill. The Slayton A. Evans Jr. Memorial Lecture Fund and the Slayton Evans Research Award were both named in his honor post-humously. | 4 | Stereochemistry |
This investigation has shown how conventional chemistry, i.e. internal recombination of hydrogen and oxygen, accounted for the entire amount of apparent excess heat. The investigators concluded their publication with the following word of advice:
Jones et al. have confirmed the Shkedi et al. findings with the same conclusion: | 7 | Physical Chemistry |
The citric acid cycle (Krebs cycle) is a good example of an amphibolic pathway because it functions in both the degradative (carbohydrate, protein, and fatty acid) and biosynthetic processes. The citric acid cycle occurs on the cytosol of bacteria and within the mitochondria of eukaryotic cells. It provides electrons to the electron transport chain which is used to drive the production of ATP in oxidative phosphorylation. Intermediates in the citric acid cycle, such as oxaloacetate, are used to synthesize macromolecule constituents such as amino acids, e.g. glutamate and aspartate.
The first reaction of the cycle, in which oxaloacetate (a four-carbon compound) condenses with acetate (a two-carbon compound) to form citrate (a six-carbon compound) is typically anabolic. The next few reactions, which are intramolecular rearrangements, produce isocitrate. The following two reactions, namely the conversion of D-isocitrate to α-Ketoglutarate followed by its conversion to succinyl-CoA, are typically catabolic. Carbon dioxide is lost in each step and succinate (a four-carbon compound) is produced.
There is an interesting and critical difference in the coenzymes used in catabolic and anabolic pathways; in catabolism NAD+ serves as an oxidizing agent when it is reduced to NADH. Whereas in anabolism the coenzyme NADPH serves as the reducing agent and is converted to its oxidized form NADP.
Citric acid cycle has two modes that play two roles, the first being energy production produced by the oxidative mode, as the acetyl group of acetyl-coA is fully oxidized to CO. This produces most of the ATP in the metabolism of aerobic heterotrophic metabolism, as this energy conversion in the membrane structure (cytoplasmic membrane in bacteria and mitochondria in eukaryotes) by oxidative phosphorylation by moving electron from donor (NADH and FADH) to the acceptor O. Every cycle give 3 NADH, 1 FADH, CO and GTP. The second role is biosynthetic, as citric acid cycle regenerate oxaloacetate when cycle intermediates are removed for biosynthesis. | 1 | Biochemistry |
Nuclear magnetic resonance (NMR) spectroscopy is known as the most widely applied and “one of the most powerful techniques” for the sequence analysis of synthetic copolymers. NMR spectroscopy allows determination of the relative abundance of comonomer sequences at the level of dyads and in cases of small repeat units even triads or more. It also allows the detection and quantification of chain defects and chain end groups, cyclic oligomers and by-products. However, limitations of NMR spectroscopy are that it cannot, so far, provide information about the sequence distribution along the chain, like gradients, clusters or a long-range order. | 7 | Physical Chemistry |
In chemistry, phosphorochloridites are a class of organophosphorus compound with the formula (RO)PCl (R = organic substituent). They are pyramidal in shape, akin to regular phosphites (P(OR)). They are usually colorless and sensitive toward hydrolysis and, to some extent, oxidation to the corresponding phosphorochloridates ((RO)P(O)Cl). | 0 | Organic Chemistry |
Barbara Cannon is a British-Swedish biochemist, physiologist and an academic. She is an emeritus professor at Stockholm University as well as the chairman of the scientific advisory board at The Helmholtz Centre. She is also a consultant at Combigene.
Cannon is most known for her work on mammalian thermogenesis, primarily focusing on the function of brown adipose tissue. She is the recipient of the 2014 King's Medal from the Order of the Seraphims, Sweden.
Cannon is a Fellow of the Royal Swedish Academy of Sciences. | 1 | Biochemistry |
As widely reported in the scientific literature, bone density is just one of the components of bone strength thus it only partially predicts bone fragility. In order to overcome this limitation, a novel parameter, Fragility Score, has been developed. Fragility Score evaluates bone microstructural features independently from BMD and it is based on the assumption that a fragile bone structure has microstructural features which, in turn, influence the spectral characteristics of the acquired ultrasound signal, being different from those reflecting a robust bone structure. Fragility Score is an adimensional parameter, ranging from 0 to 100, obtained by comparing the spectra of the acquired ultrasound signals with the spectral reference models obtained from patients who did, or did not, developed an osteoporotic fracture. This parameter has been validated through clinical studies and its accuracy has demonstrated a performance similar to DXA BMD. | 7 | Physical Chemistry |
The barrier for the rotation of the alkene about the M-centroid vector is a measure of the strength of the M-alkene pi-bond. Low symmetry complexes are suitable for analysis of these rotational barriers associated with the metal-ethene bond.In CpRh(CH)(CF), the ethene ligand is observed to rotate with a barrier near 12 kcal/mol but no rotation is observed for about the Rh-CF bond. | 0 | Organic Chemistry |
Hydrogen sulfide chemosynthesis is a form of chemosynthesis which uses hydrogen sulfide. It is common in hydrothermal vent microbial communities Due to the lack of light in these environments this is predominant over photosynthesis
Giant tube worms use bacteria in their trophosome to fix carbon dioxide (using hydrogen sulfide as their energy source) and produce sugars and amino acids. Some reactions produce sulfur:
: hydrogen sulfide chemosynthesis:
:: 18H + 6CO + 3 → CHO (carbohydrate) + 12H + 18
In the above process, hydrogen sulfide serves as a source of electrons for the reaction. Instead of releasing oxygen gas while fixing carbon dioxide as in photosynthesis, hydrogen sulfide chemosynthesis produces solid globules of sulfur in the process.
Mechanism of Action
In deep sea environments, different organisms have been observed to have the ability to oxidize reduced compounds such as hydrogen sulfide. Oxidation is the loss of electrons in a chemical reaction. Most chemosynthetic bacteria form symbiotic associations with other small eukaryotes The electrons that are released from hydrogen sulfide will provide the energy to sustain a proton gradient across the bacterial cytoplasmic membrane. This movement of protons will eventually result in the production of adenosine triphosphate. The amount of energy derived from the process is also dependent on the type of final electron acceptor.
Other Examples Of Chemosynthetic Organisms (using HS as electron donor)
Across the world, researchers have observed different organisms in various locations capable of carrying out the process. Yang and colleagues in 2011 surveyed five Yellowstone thermal springs of varying depths and observed that the distribution of chemosynthetic microbes coincided with temperature as Sulfurihydrogenibiom was found at higher temperatures while Thiovirga inhabited cooler waters Miyazaki et al., in 2020 also found an endosymbiont capable of hydrogen sulfide chemosynthesis which contained campylobacter species and a gastropod from the genus Alviniconcha oxidise hydrogen sulfide in the Indian Ocean Furthermore, chemosynthetic bacteria such as purple sulfur bacteria have yellow globules of sulfur visible in their cytoplasm. | 1 | Biochemistry |
A purpose for introducing spiciness is to decrease the amount of state variables needed; the density at constant depth is a function of potential temperature and salinity and of using both, spiciness can be used. If the goal is to only quantify the variation of water parcels along isopycnals, the variation in absolute salinity or temperature can be used instead because it gives the same information with the same amount of variables.
Another purpose is to examine how the stability ratio varies vertically on a water column. The stability ratio is a number determining the involvement of temperature changes relative to the involvement salinity changes in a vertical profile, which yields relevant information about the stability of the water column:
The vertical variation of this number is often shown in a spiciness-potential density diagram and/or plot, where the angle shows the stability. | 7 | Physical Chemistry |
Lisinopril is the lysine-analog of enalapril. Unlike other ACE inhibitors, it is not a prodrug, is not metabolized by the liver, and is excreted unchanged in the urine. | 4 | Stereochemistry |
Temperature dependent loop formations introduce temperature-dependence in the expression of downstream operons. All such elements act in a translation-dependent manner by controlling the accessibility of the Shine-Dalgarno sequence, for example the expression of pathogenicity islands of some bacteria upon entry to a host. Recent data predict the existence of temperature-dependent alternative secondary structures (including Rho-independent terminators) upstream of cold shock proteins in E. coli. | 1 | Biochemistry |
Galvanization consists of an application on the object to be protected of a layer of metallic zinc by either hot-dip galvanizing or electroplating. Zinc is traditionally used because it is cheap, adheres well to steel, and provides cathodic protection to the steel surface in case of damage of the zinc layer. In more corrosive environments (such as salt water), cadmium plating is preferred instead of the underlying protected metal. The protective zinc layer is consumed by this action, and thus galvanization provides protection only for a limited period of time.
More modern coatings add aluminium to the coating as zinc-alume; aluminium will migrate to cover scratches and thus provide protection for a longer period. These approaches rely on the aluminium and zinc oxides protecting a once-scratched surface, rather than oxidizing as a sacrificial anode as in traditional galvanized coatings. In some cases, such as very aggressive environments or long design life, both zinc and a coating are applied to provide enhanced corrosion protection.
Typical galvanization of steel products that are to be subjected to normal day-to-day weathering in an outside environment consists of a hot-dipped 85 µm zinc coating. Under normal weather conditions, this will deteriorate at a rate of 1 µm per year, giving approximately 85 years of protection. | 8 | Metallurgy |
This shell is related to solid state physics and structural chemistry. The program [http://www.cryst.ehu.es/cryst/pseudosymmetry.html PSEUDO] performs an evaluation of the pseudosymmetry of a given structure with respect to supergroups of its space group. [http://www.cryst.ehu.es/cryst/amplimodes.html AMPLIMODES] performs the symmetry-mode analysis of any distorted structure of displacive type. The analysis consists in decomposing the symmetry-breaking distortion present in the distorted structure into contributions from different symmetry-adapted modes. Given the high and low symmetry structures, the program calculates the amplitudes and polarization vectors of the distortion modes of different symmetry frozen in the structure. The program [http://www.cryst.ehu.es/rep/sam.html SAM] calculates symmetry-adapted modes for the centre of the Brillouin zone and classifies them according to their infrared and Raman activity. [http://www.cryst.ehu.es/rep/neutron.html NEUTRON] computes the phonon extinction rules in inelastic neutron scattering. Its results are also relevant for diffuse-scattering experiments. | 3 | Analytical Chemistry |
Bili light. A type of phototherapy that uses blue light with a range of 420–470 nm, used to treat neonatal jaundice. | 5 | Photochemistry |
Recent works have shown that plants can respond to airborne sounds at audible frequencies and that they also produce airborne sounds at the ultrasonic range, presumably audible to multiple organisms including bats, mice, moths and other insects. | 1 | Biochemistry |
Hydrogen lowers tensile ductility in many materials. In ductile materials, like austenitic stainless steels and aluminium alloys, no marked embrittlement may occur, but may exhibit significant lowering in tensile ductility (% elongation or % reduction in area) in tensile tests. | 8 | Metallurgy |
The synthesis of the D ring (scheme 6) started from 44 with allylic bromination with copper(I) bromide and benzoyl tert-butyl peroxide to bromide 45. By adding even more bromide, another bromide 46 formed (both compounds are in chemical equilibrium) with the bromine atom in an axial position. Osmium tetroxide added two hydroxyl groups to the exocyclic double bond in diol 47 and oxetane ring-closure to 48 took place with DBU in a nucleophilic substitution. Then, acylation of the C4 hydroxyl group (acetic anhydride, DMAP, pyridine) resulted in acetate 49. In the final steps phenyllithium opened the ester group to form hydroxy carbonate 50, both TES groups were removed (HF, pyr) to triol 51 (baccatin III) and the C7 hydroxyl group was back-protected to 52. | 0 | Organic Chemistry |
The micelle velocity is defined by:
where is the electrophoretic velocity of a micelle.
The retention time of a given sample should depend on the capacity factor, :
where is the total number of moles of solute in the micelle and is the total moles in the aqueous phase. The retention time of a solute should then be within the range:
Charged analytes have a more complex interaction in the capillary because they exhibit electrophoretic mobility, engage in electrostatic interactions with the micelle, and participate in hydrophobic partitioning.
The fraction of the sample in the aqueous phase, , is given by:
where is the migration velocity of the solute. The value can also be expressed in terms of the capacity factor:
Using the relationship between velocity, tube length from the injection end to the detector cell (), and retention time, , and , a relationship between the capacity factor and retention times can be formulated:
The extra term enclosed in parentheses accounts for the partial mobility of the hydrophobic phase in MEKC. This equation resembles an expression derived for in conventional packed bed chromatography:
A rearrangement of the previous equation can be used to write an expression for the retention factor:
From this equation it can be seen that all analytes that partition strongly into the micellar phase (where is essentially ∞) migrate at the same time, . In conventional chromatography, separation of similar compounds can be improved by gradient elution. In MEKC, however, techniques must be used to extend the elution range to separate strongly retained analytes.
Elution ranges can be extended by several techniques including the use of organic modifiers, cyclodextrins, and mixed micelle systems. Short-chain alcohols or acetonitrile can be used as organic modifiers that decrease and to improve the resolution of analytes that co-elute with the micellar phase. These agents, however, may alter the level of the EOF. Cyclodextrins are cyclic polysaccharides that form inclusion complexes that can cause competitive hydrophobic partitioning of the analyte. Since analyte-cyclodextrin complexes are neutral, they will migrate toward the cathode at a higher velocity than that of the negatively charged micelles. Mixed micelle systems, such as the one formed by combining SDS with the non-ionic surfactant Brij-35, can also be used to alter the selectivity of MEKC. | 3 | Analytical Chemistry |
pIII is the protein that determines the infectivity of the virion. pIII is composed of three domains (N1, N2 and CT) connected by glycine-rich linkers. The N2 domain binds to the F pilus during virion infection freeing the N1 domain which then interacts with a TolA protein on the surface of the bacterium. Insertions within this protein are usually added in position 249 (within a linker region between CT and N2), position 198 (within the N2 domain) and at the N-terminus (inserted between the N-terminal secretion sequence and the N-terminus of pIII). However, when using the BamHI site located at position 198 one must be careful of the unpaired Cysteine residue (C201) that could cause problems during phage display if one is using a non-truncated version of pIII.
An advantage of using pIII rather than pVIII is that pIII allows for monovalent display when using a phagemid (plasmid derived from Ff phages) combined with a helper phage. Moreover, pIII allows for the insertion of larger protein sequences (>100 amino acids) and is more tolerant to it than pVIII. However, using pIII as the fusion partner can lead to a decrease in phage infectivity leading to problems such as selection bias caused by difference in phage growth rate or even worse, the phage's inability to infect its host. Loss of phage infectivity can be avoided by using a phagemid plasmid and a helper phage so that the resultant phage contains both wild type and fusion pIII.
cDNA has also been analyzed using pIII via a two complementary leucine zippers system, Direct Interaction Rescue or by adding an 8-10 amino acid linker between the cDNA and pIII at the C-terminus. | 1 | Biochemistry |
It is commonly known that drug addiction involves permanent synaptic plasticity of various neuronal circuits. Neuroproteomics is being applied to study the effect of drug addiction across the synapse. Research is being conducted by isolating distinct regions of the brain in which synaptic transmission takes place and defining the proteome for that particular region. Different stages of drug abuse must be studied, however, in order to map out the progression of protein changes along the course of the drug addiction. These stages include enticement, ingesting, withdrawal, addiction, and removal. It begins with the change in the genome through transcription that occurs due to the abuse of drugs. It continues to identify the most likely proteins to be affected by the drugs and focusing in on that area.
For drug addiction, the synapse is the most likely target as it involves communication between neurons. Lack of sensory communication in neurons is often an outward sign of drug abuse, and so neuroproteomics is being applied to find out what proteins are being affected to prevent the transport of neurotransmitters. In particular, the vesicle releasing process is being studied to identify the proteins involved in the synapse during drug abuse. Proteins such as synaptotagmin and synaptobrevin interact to fuse the vesicle into the membrane. Phosphorylation also has its own set of proteins involved that work together to allow the synapse to function properly. Drugs such as morphine change properties such as cell adhesion, neurotransmitter volume, and synaptic traffic. After significant morphine application, tyrosine kinases received less phosphorylation and thus send fewer signals inside the cell. These receptor proteins are unable to initiate the intracellular signaling processes that enable the neuron to live, and necrosis or apoptosis may be the result. With more and more neurons affected along this chain of cell death, permanent loss of sensory or motor function may be the result. By identifying the proteins that are changed with drug abuse, neuroproteomics may give clinicians even earlier biomarkers to test for to prevent permanent neurological damage.
Recently, a novel terminology (Psychoproteomics) has been coined by the University of Florida researchers from Dr. Mark S Gold Lab. Kobeissy et al. defined Psychoproteomics as integral proteomics approach dedicated to studying proteomic changes in the field of psychiatric disorders, particularly substance-and drug-abuse neurotoxicity. | 1 | Biochemistry |
Electrocatalysts are used to promote certain chemical reactions to obtain synthetic products. Graphene and graphene oxides have shown promise as electrocatalytic materials for synthesis. Electrocatalytic methods also have potential for polymer synthesis. Electrocatalytic synthesis reactions can be performed under a constant current, constant potential, or constant cell-voltage conditions, depending on the scale and purpose of the reaction. | 7 | Physical Chemistry |
Following phenotypic selection, genomic DNA is extracted from the selected clones, alongside a control cell population. In the most common protocols for genome-wide knockouts, a Next-generation sequencing (NGS) library is created by a two step polymerase chain reaction (PCR). The first step amplifies the sgRNA region, using primers specific to the lentiviral integration sequence, and the second step adds Illumina i5 and i7 sequences. NGS of the PCR products allows the recovered sgRNAs to be identified, and a quantification step can be used to determine the relative abundance of each sgRNA.
The final step in the screen is to computationally evaluate the significantly enriched or depleted sgRNAs, trace them back to their corresponding genes, and in turn determine which genes and pathways could be responsible for the observed phenotype. Several algorithms are currently available for this purpose, with the most popular being the Model-based Analysis of Genome-wide CRISPR/Cas9 Knockout (MAGeCK) method. Developed specifically for CRISPR/Cas9 knockout screens in 2014, MAGeCK demonstrated better performance compared with alternative algorithms at the time, and has since demonstrated robust results and high sensitivity across different experimental conditions. As of 2015, the MAGeCK algorithm has been extended to introduce quality control measurements, and account for the previously overlooked sgRNA knockout efficiency. A web-based visualisation tool (VISPR) was also integrated, allowing users to interactively explore the results, analysis, and quality controls. | 1 | Biochemistry |
Larry Paul Kelley established ICT (International Crystal Technology) in 1970 with Craig Hardy and Tom VanBergen. Kelley had worked for Dow Chemical in Ludington and at a factory in Ann Arbor that produced laser crystals. The facility was sited in Shelby because the town had a new industrial park. By 2015, Kelley was ICT's sole owner.
The Shelby Gem Factory initially produced only synthetic ruby, with ruby lasers being the principal application, primarily sold to firms in California. However, laser technology was in its infancy, and the far greater profit potential of converting ruby rods into a variety of artificial gemstones of various colors led to a change in the factorys focus. Larry Kelley built on Soviet research into cubic zirconia and became its first commercial producer, having solved issues of temperature control that had impeded its production. For a time, cubic zirconia was a lucrative product line; Shelby opened factories outside the United States to keep up with demand. However, the value of cubic zirconia soon declined to the point that it was used as fill when the factory was expanded. In 1983, ICT opened a faceting factory in southern China to create gemstones for jewelry use from the crystals produced in Shelby; this closed in 1991, and separate companies in China and South Korea were contracted to continue faceting. The South Korean market represented up to 40 percent of the factorys sales until a precipitous decline caused by the 1997 Asian financial crisis. In 1994, the factory entered the business of recrystallizing rubies, buying low-grade gems from Myanmar to be melted down in the process.
A 50-seat theater ran a presentation for visitors, and jewelry was sold on site.
The factory closed in 2019 after Kelley was diagnosed in 2017 with Alzheimer's disease. Other issues that contributed to the closing were worldwide competition and online markets. Larry Kelley died on October 24, 2020. | 7 | Physical Chemistry |
Diethyl dixanthogen disulfide is a component for froth flotations used, inter alia, for the separation of sulfide minerals like pyrrhotite. Diisopropyl dixanthogen disulfide is a reagent in the synthesis of sulfur heterocycles.
Dialkoxy dixanthogen disulfides undergo desulfurization by cyanide to give bis(alkoxythiocarbonyl)sulfides:
Dixanthogens are also ectoparasiticides. | 0 | Organic Chemistry |
After crystallization, often some solidified flux remains on the surface or inside the desired crystal. This flux may cause defects in the crystal due to the different thermal expansivities of the flux and crystal. A solvent (typically an acid or a base) can dissolve the flux, but its difficult to find a solvent that doesnt also dissolve the crystal. The flux can be removed mechanically using a blade or drill. If the crystal and flux have significantly different boiling points, the flux may be removed with evaporation. Flux can also be removed through recrystallization through use of a seed in the liquid phase, leaving the flux behind as the crystals accumulate.
The removal of excess flux is important to assess a crystals properties, as the flux can affect measurements. For example, tin and lead super conduct at low temperatures, if a sample has tin or lead flux superconductivity can be observed even if the desired crystal is not a superconductor. | 3 | Analytical Chemistry |
Two-component systems accomplish signal transduction through the phosphorylation of a response regulator (RR) by a histidine kinase (HK). Histidine kinases are typically homodimeric transmembrane proteins containing a histidine phosphotransfer domain and an ATP binding domain, though there are reported examples of histidine kinases in the atypical [http://pfam.xfam.org/family/PF07536 HWE] and [http://pfam.xfam.org/family/PF07568 HisKA2] families that are not homodimers. Response regulators may consist only of a receiver domain, but usually are multi-domain proteins with a receiver domain and at least one effector or output domain, often involved in DNA binding. Upon detecting a particular change in the extracellular environment, the HK performs an autophosphorylation reaction, transferring a phosphoryl group from adenosine triphosphate (ATP) to a specific histidine residue. The cognate response regulator (RR) then catalyzes the transfer of the phosphoryl group to an aspartate residue on the response regulators receiver domain. This typically triggers a conformational change that activates the RRs effector domain, which in turn produces the cellular response to the signal, usually by stimulating (or repressing) expression of target genes.
Many HKs are bifunctional and possess phosphatase activity against their cognate response regulators, so that their signaling output reflects a balance between their kinase and phosphatase activities. Many response regulators also auto-dephosphorylate, and the relatively labile phosphoaspartate can also be hydrolyzed non-enzymatically. The overall level of phosphorylation of the response regulator ultimately controls its activity. | 1 | Biochemistry |
Art in bronze and brass dates from remote antiquity. These important metals are alloys, bronze composed of copper and tin and brass of copper and zinc.
Proportions of each alloy vary slightly. Bronze may be normally considered as nine parts of copper to one of tin. Other ingredients which are occasionally found are more or less accidental. The result is a metal of a rich golden brown colour, capable of being worked by casting — a process little applicable to its component parts, but peculiarly successful with bronze, the density and hardness of the metal allowing it to take any impression of a mould, however delicate. It is thus possible to create ornamental work of various kinds. | 8 | Metallurgy |
ATP is the phosphorylated version of adenosine diphosphate (ADP), which stores energy in a cell and powers most cellular activities. ATP is the energized form, while ADP is the (partially) depleted form. NADP is an electron carrier which ferries high energy electrons. In the light reactions, it gets reduced, meaning it picks up electrons, becoming NADPH. | 5 | Photochemistry |
Reactions on surfaces are reactions in which at least one of the steps of the reaction mechanism is the adsorption of one or more reactants. The mechanisms for these reactions, and the rate equations are of extreme importance for heterogeneous catalysis. Via scanning tunneling microscopy, it is possible to observe reactions at the solid gas interface in real space, if the time scale of the reaction is in the correct range. Reactions at the solid–gas interface are in some cases related to catalysis. | 7 | Physical Chemistry |
A lot of research has been conducted on Vectorette PCR and the applications it has in the field of biology. Scientists used Vectorette PCR to take the transgene flanking DNA and isolate it. They used this technique on the DNA belonging to mice that was next to transgene sections. From this the scientists were able to show that the use of Vectorettes is capable of facilitating the recovery and mapping of sequences in complex genomes. They have also found that Vectorette PCR can help in the analysis of sequences by subvectoretting when PCR products of a large size are the subject at hand.
Other work has looked at developing a method using Vectorette PCR in order to accomplish genomic walking. By using Vectorette PCR, scientists were able to acquire single-stranded DNA which were obtained from PCR products in order to sequence them. From this an approach was identified in which the amplification of sequences which were previously uncharacterized was possible. This research demonstrates how novel sequences can be rapidly developed when only a known sequence of DNA is used to start.
Further research has experimented with the creation of a method that progresses the isolation of microsatellite repeats. By using Vectorette PCR, researchers have found a rapid technique to accomplish this with novel, microsatellite repeats. They have attempted and succeeded in using this technique to isolate an amount of six microsatellite repeats.
Vectorette PCR has also been used to not only identify genomic positions of insertion sequences (IS) but also to map them. Research on this has shed light on a way to complete the typing of microbial stains and the identification and mapping of things like IS insertion sites that reside in microbial genomes. Vectorette PCR proves useful when it comes to rapidly and simply surveying genomes’ IS elements.
Transposable element, transposon, or TE is a variation of genetic elements that is capable of changing its location in a genome by a process called “jumping”. TE display is designed to present the different variations of TE insertion sites which helps to make numerous dominant markers. A problem that arose in the original method was finding a PCR method that was capable of being specific and efficient in its output of the transposon within the genome. Researchers have found a solution for this problem by using Vectorette PCR as the PCR method. Since Vectorette PCR is capable of being specific with its isolation and amplification of genes, this helped with their research and aided in improving the method of TE display by saving both time and costs. The researchers were then able to produce numerous dominant markers with the use of Vectorette PCR that is based on a TE display that is nonradioactive.
Thyroid lymphoma is an illness which leads to the transformation of the lymphocytes belonging to the thyroid into cells of a cancerous nature. Researchers have tested a new method that aids in the diagnosis of this condition. The use of Vectorette PCR was combined with restriction enzyme digestion, and it was found that Vectorette PCR proved to be useful in their study and aided in the diagnosis of thyroid lymphoma.
Researchers have looked into the potential use of Vectorette PCR in the examination of the genes of diseases. They have taken two methods, trinucleotide repeats which are specifically used for the targeting of transcribed regions and Vectorette PCR, to obtain simple sequence repeats or SSRs. It is believed that genetic markers can be made from these SSRs. The outcome from this research is hoped to aid researchers attempt the derivation of genetic markers which are transportable from unknown genomes. Vectorette PCR was used to uncover SSRs which flank the trinucleotide repeat that was targeted for testing. This is also known as TNR or trinucleotide Vectorette PCR. They believe that their TNR method combined with the amplification provided by Vectorette PCR can be used in eukaryotes to create molecular markers that are based on simple repeat sequences. The researchers also think that this method will be of value when attempting to isolate genes that are able to bring about diseases. | 1 | Biochemistry |
The research of Kuipers and his research group is focused on curiosity driven research with a keen eye on biotechnological applications. Kuipers has so far supervised 21 postdoctoral researchers and 35 PhD students in their doctorate research. At the moment (October 2015) he supervises 18 PhD students and 7 postdoctoral researchers. He has been invited more than 180 times to national and international conferences, seminars and congresses to give a lecture.
An important topic of research is the study of the genetics and physiology of bacteria. Among others, the cellular differentiation of bacteria is investigated. Bacteria growing in a culture can develop different characteristics, while their genome remains unchanged. Kuipers stated: ‘Our research has many applications, for example the improvement of protein production in industrial fermentation'.
Another important subject is the production and modification of peptides. These modified peptides (called lantibiotics), are made by bacteria, and can serve as antibiotic. Modified peptides are chemically more stable and retain their function longer than unmodified peptides. This is beneficial for medical applications as a novel class of antibiotics.
Further areas of focus are the molecular biology of: competence, sporulation and bistability in Bacillus subtilis, the reconstruction of gene networks, antimicrobial peptides, antibiotics, mechanisms of pathogenesis, cell wall anchoring, controlled gene expression systems, the subcellular localization of protein, stress response, quorum sensing, regulation of the C- and N-metabolism, natural gene transfer methodologies, plant-biocontrol by Bacilli and Biotechnology applications. | 0 | Organic Chemistry |
* Epitope – the distinct surface features of an antigen, its antigenic determinant.<br />Antigenic molecules, normally "large" biological polymers, usually present surface features that can act as points of interaction for specific antibodies. Any such feature constitutes an epitope. Most antigens have the potential to be bound by multiple antibodies, each of which is specific to one of the antigen's epitopes. Using the "lock and key" metaphor, the antigen can be seen as a string of keys (epitopes) each of which matches a different lock (antibody). Different antibody idiotypes, each have distinctly formed complementarity-determining regions.
* Allergen – A substance capable of causing an allergic reaction. The (detrimental) reaction may result after exposure via ingestion, inhalation, injection, or contact with skin.
* Superantigen – A class of antigens that cause non-specific activation of T-cells, resulting in polyclonal T-cell activation and massive cytokine release.
* Tolerogen – A substance that invokes a specific immune non-responsiveness due to its molecular form. If its molecular form is changed, a tolerogen can become an immunogen.
* Immunoglobulin-binding protein – Proteins such as protein A, protein G, and protein L that are capable of binding to antibodies at positions outside of the antigen-binding site. While antigens are the "target" of antibodies, immunoglobulin-binding proteins "attack" antibodies.
* T-dependent antigen – Antigens that require the assistance of T cells to induce the formation of specific antibodies.
* T-independent antigen – Antigens that stimulate B cells directly.
* Immunodominant antigens – Antigens that dominate (over all others from a pathogen) in their ability to produce an immune response. T cell responses typically are directed against a relatively few immunodominant epitopes, although in some cases (e.g., infection with the malaria pathogen Plasmodium spp.) it is dispersed over a relatively large number of parasite antigens.
Antigen-presenting cells present antigens in the form of peptides on histocompatibility molecules. The T cells selectively recognize the antigens; depending on the antigen and the type of the histocompatibility molecule, different types of T cells will be activated. For T-cell receptor (TCR) recognition, the peptide must be processed into small fragments inside the cell and presented by a major histocompatibility complex (MHC). The antigen cannot elicit the immune response without the help of an immunologic adjuvant. Similarly, the adjuvant component of vaccines plays an essential role in the activation of the innate immune system.
An immunogen is an antigen substance (or adduct) that is able to trigger a humoral (innate) or cell-mediated immune response. It first initiates an innate immune response, which then causes the activation of the adaptive immune response. An antigen binds the highly variable immunoreceptor products (B-cell receptor or T-cell receptor) once these have been generated. Immunogens are those antigens, termed immunogenic, capable of inducing an immune response.
At the molecular level, an antigen can be characterized by its ability to bind to an antibody's paratopes. Different antibodies have the potential to discriminate among specific epitopes present on the antigen surface. A hapten is a small molecule that can only induce an immune response when attached to a larger carrier molecule, such as a protein. Antigens can be proteins, polysaccharides, lipids, nucleic acids or other biomolecules. This includes parts (coats, capsules, cell walls, flagella, fimbriae, and toxins) of bacteria, viruses, and other microorganisms. Non-microbial non-self antigens can include pollen, egg white, and proteins from transplanted tissues and organs or on the surface of transfused blood cells. | 1 | Biochemistry |
* Durable water repellent This being used for fabrics in order to protect them from water.
* Rain repellent This is made for car windshield for repelling rain water during rain in order to improve driving visibility. | 7 | Physical Chemistry |
Kujawinski was an undergraduate student at Massachusetts Institute of Technology (MIT). She was awarded the undergraduate teaching award from the Department of Chemistry. She moved to the Woods Hole Oceanographic Institution (WHOI) as a doctoral researcher, where she worked in chemical oceanography. Her doctoral research considered the effect of protozoan grazers on polychlorinated biphenyl cycling. After graduating Kujawinski joined the Ohio State University as a postdoctoral scholar. | 9 | Geochemistry |
Food Standards Australia New Zealand develops the standards for levels of pesticide residues in foods through a consultation process. The New Zealand Food Safety Authority publishes the maximum limits of pesticide residues for foods produced in New Zealand. | 2 | Environmental Chemistry |
Miraculin, unlike curculin (another taste-modifying agent), is not sweet by itself, but it can change the perception of sourness to sweetness, even for a long period after consumption. The duration and intensity of the sweetness-modifying effect depends on various factors, such as miraculin concentration, duration of contact of the miraculin with the tongue, and acid concentration. Miraculin reaches its maximum sweetness with a solution containing at least 4*10 mol/L miraculin, which is held in the mouth for about 3 minutes. Maximum is equivalent in sweetness to a 0.4 mol/L solution of sucrose. Miraculin degrades permanently via denaturation at high temperatures, at pH below 3 or above 12.
Although the detailed mechanism of the taste-inducing behavior is unknown, it appears the sweet receptors are activated by acids which are related to sourness, an effect remaining until the taste buds perceive a neutral pH. Sweeteners are perceived by the human sweet taste receptor, hT1R2-hT1R3, which belongs to G protein-coupled receptors, modified by the two histidine residues (i.e. His30 and His60) which participate in the taste-modifying behavior. One site maintains the attachment of the protein to the membranes while the other (with attached xylose or arabinose) activates the sweet receptor membrane in acid solutions. | 1 | Biochemistry |
Iron is a popular research target for many catalytic processes, owing largely to its low cost and low toxicity relative to other transition metals. Asymmetric hydrogenation methods using iron have been realized, although in terms of rates and selectivity, they are inferior to catalysts based on precious metals. In some cases, structurally ill-defined nanoparticles have proven to be the active species in situ and the modest selectivity observed may result from their uncontrolled geometries. | 0 | Organic Chemistry |
In the human, the uterine lining (endometrium) needs to be appropriately prepared so that the embryo can implant. In a natural cycle the embryo transfer takes place in the luteal phase at a time where the lining is appropriately undeveloped in relation to the status of the present Luteinizing Hormone. In a stimulated or cycle where a "frozen" embryo is transferred, the recipient woman could be given first estrogen preparations (about 2 weeks), then a combination of estrogen and progesterone so that the lining becomes receptive for the embryo. The time of receptivity is the implantation window. A scientific review in 2013 came to the conclusion that it is not possible to identify one method of endometrium preparation in frozen embryo transfer as being more effective than another.
Limited evidence also supports removal of cervical mucus before transfer. | 1 | Biochemistry |
One of ATSDR’s primary responsibilities is conducting public health assessments and health consultations. The agency conducts public health assessments for all current or proposed sites on the National Priorities List (commonly known as Superfund sites). The purpose of public health assessments is to examine whether hazardous substances at a site pose a human health hazard and to issue recommendations about limiting or stopping exposure to those substances. ATSDR also conducts health consultations, often in response to requests from EPA and state and local agencies. Health consultations examine specific health questions, such as the health effects of exposure to a specific chemical at a site. Health consultations are more limited in scope than public health assessments. ATSDR also conducts public health assessments and health consultations in response to petitions from members of the public. To conduct public health assessments and health consultations, ATSDR relies on its own scientists or establishes cooperative agreements with states, providing technical assistance to state health departments. ATSDR issued more than 200 public health assessments in 2009 and provides about 1,000 health consultations each year.
When investigating sites, ATSDR examines environmental data, health data, and information from community members about how the site affects their quality of life. ATSDR normally does not collect its own environmental data; rather, it usually relies on partner organizations, such as EPA, to conduct testing and gather data. This environmental data provides information on the amount of contamination and possible ways humans could be exposed to the hazardous substances at the site. The health data provides information on rates of illness, disease, and death in the local community. Since ATSDR is an advisory agency, the conclusions in its public health assessments and health consultations are often in the form of recommendations to state and national environmental and health agencies, such as EPA, that have regulatory authority. Other agencies and the general public rely on ATSDR to provide trusted information on the health effects of hazardous substances at contaminated sites. | 1 | Biochemistry |
* In the "Liquid Solar Fuel Production demonstration Project" in 2020 the large-scale production of renewable methanol with sun power with a 10 MW electrolyzer was demonstrated.
* More than 20 000 taxis are operated in China with methanol (as of 2020)
* End of 2021 in Henan province the world's largest plant for production of methanol from CO with a capacity of 110 000 t/a shall be commissioned in "Shunli CO-To-Methanol Plant" with assistance of Carbon Recycling International.
* Several major Chinese automakers such as FAW Group, Shanghai Huapu (Shanghai Maple), Geely Group, Chang’an and SAIC prepare for mass production of methanol capable vehicles and fleets of taxis and buses.
* In Shanxi province there exist more than 1000 petrol stations that sell M15 and further 40 M85-M100 refueling points. Until 2025 the government of Shanxi wants to convert more than 2000 refueling stations for methanol fuel as well as 200 000 vehicles for operation with methanol. | 2 | Environmental Chemistry |
COX assembly in yeast are a complex process that is not entirely understood due to the rapid and irreversible aggregation of hydrophobic subunits that form the holoenzyme complex, as well as aggregation of mutant subunits with exposed hydrophobic patches. COX subunits are encoded in both the nuclear and mitochondrial genomes. The three subunits that form the COX catalytic core are encoded in the mitochondrial genome. Over 30 different nuclear-encoded chaperone proteins are required for COX assembly.
Cofactors, including hemes, are inserted into subunits I & II. The two heme molecules reside in subunit I, helping with transport to subunit II where two copper molecules aid with the continued transfer of electrons. Subunits I and IV initiate assembly. Different subunits may associate to form sub-complex intermediates that later bind to other subunits to form the COX complex. In post-assembly modifications, COX will form a homodimer. This is required for activity. Dimers are connected by a cardiolipin molecule, which has been found to play a key role in stabilization of the holoenzyme complex. The dissociation of subunits VIIa and III in conjunction with the removal of cardiolipin results in total loss of enzyme activity. Subunits encoded in the nuclear genome are known to play a role in enzyme dimerization and stability. Mutations to these subunits eliminate COX function.
Assembly is known to occur in at least three distinct rate-determining steps. The products of these steps have been found, though specific subunit compositions have not been determined.
Synthesis and assembly of COX subunits I, II, and III are facilitated by translational activators, which interact with the 5’ untranslated regions of mitochondrial mRNA transcripts. Translational activators are encoded in the nucleus. They can operate through either direct or indirect interaction with other components of translation machinery, but exact molecular mechanisms are unclear due to difficulties associated with synthesizing translation machinery in-vitro. Though the interactions between subunits I, II, and III encoded within the mitochondrial genome make a lesser contribution to enzyme stability than interactions between bigenomic subunits, these subunits are more conserved, indicating potential unexplored roles for enzyme activity. | 1 | Biochemistry |
The amount of methane in the atmosphere is the result of a balance between the production of methane on the Earth's surfaceits sourceand the destruction or removal of methane, mainly in the atmosphereits sink in an atmospheric chemical process.
Another major natural sink is through oxidation by methanotrophic or methane-consuming bacteria in Earth's soils.
These 2005 NASA computer model simulationscalculated based on data available at that timeillustrate how methane is destroyed as it rises.
As air rises in the tropics, methane is carried upwards through the tropospherethe lowest portion of Earths atmosphere which is to from the Earths surface, into the lower stratospherethe ozone layerand then the upper portion of the stratosphere.
This atmospheric chemical process is the most effective methane sink, as it removes 90% of atmospheric methane. This global destruction of atmospheric methane mainly occurs in the troposphere.
Methane molecules react with hydroxyl radicals (OH)the "major chemical scavenger in the troposphere" that "controls the atmospheric lifetime of most gases in the troposphere". Through this CH oxidation process, atmospheric methane is destroyed and water vapor and carbon dioxide are produced.
While this decreases the concentration of methane in the atmosphere, it also increases radiative forcing because both water vapor and carbon dioxide are more powerful GHGs factors in terms of affecting the warming of Earth.
This additional water vapor in the stratosphere caused by CH oxidation, adds approximately 15% to methane's radiative forcing effect.
By the 1980s, the global warming problem had been transformed by the inclusion of methane and other non-CO trace-gasesCFCs, NO, and O on global warming, instead of focusing primarily on carbon dioxide. Both water and ice clouds, when formed at cold lower stratospheric temperatures, have a significant impact by increasing the atmospheric greenhouse effect. Large increases in future methane could lead to a surface warming that increases nonlinearly with the methane concentration.
Methane also affects the degradation of the ozone layerthe lowest layer of the stratosphere from about above Earth, just above the troposphere. NASA researchers in 2001, had said that this process was enhanced by global warming, because warmer air holds more water vapor than colder air, so the amount of water vapor in the atmosphere increases as it is warmed by the greenhouse effect. Their climate models based on data available at that time, had indicated that carbon dioxide and methane enhanced the transport of water into the stratosphere.
Atmospheric methane could last about 120 years in the stratosphere until it is eventually destroyed through the hydroxyl radicals oxidation process. | 2 | Environmental Chemistry |
The Lippmann–Schwinger equation is useful in a very large number of situations involving two-body scattering. For three or more colliding bodies it does not work well because of mathematical limitations; Faddeev equations may be used instead. However, there are approximations that can reduce a many-body problem to a set of two-body problems in a variety of cases. For example, in a collision between electrons and molecules, there may be tens or hundreds of particles involved. But the phenomenon may be reduced to a two-body problem by describing all the molecule constituent particle potentials together with a pseudopotential. In these cases, the Lippmann–Schwinger equations may be used. Of course, the main motivations of these approaches are also the possibility of doing the calculations with much lower computational efforts. | 7 | Physical Chemistry |
The operational proof for the flux connectivity theorem relies on making perturbations to enzyme levels such that the pathway flux is unchanged but a single metabolite level is changed. This can be illustrated with the following pathway:
Let us make a change to the rate through by increasing the concentration of enzyme . Assume is increased by an amount, . This will result in a change to the steady-state of the pathway. The concentrations of , and the flux, through the pathway will increase, and the concentration of will decrease because it is upstream of the disturbance.
Impose a second change to the pathway such that the flux, is restored to what it was before the original change. Since the flux increased when was changed, the flux can be decreased by decreasing one of the other enzyme levels. If the concentration of is decreased, this will reduce the flux. Decreasing will also cause the concentration of to further increase. However, and will change in the opposite direction compared to when was increased.
When is sufficiently changed so that the flux is restored to its original value, the concentrations of and will also be restored to their original values. It is only that will differ. This is true because the flux through is now the same as it was originally (since we’ve restored the flux), and has not been manipulated in anyway. This means that the concentration of and all
species upstream of must be the same as they were before the modulations occurred. The same arguments apply to and all species downstream of .
The net result is that has been increased by resuling a change in flux of . The concentration of was decreased such that the flux was restored to it original value, . In the process, changed by but neither or . In fact no other species in the entire system has changed other than .
This thought experiment can be expressed mathematically as follows. The system equations in terms of the flux control coefficients can be written as:
There are only two terms because only and were changed.
The local change at each step can be written for and in terms of elasticities:
Note that won't necessarily equal and by construction both rates, and showed no change. Also by construction only changed.
The local equation can be rearranged as:
The right-hand sides can be inserted into the system equation the change in flux:
Therefore:
However, by construction of the perturbations, does not equal zero, hence we arrive at the connectivity theorem:
The operational method can also be used for systems where a given metabolite can influence multiple steps. This would apply to cases such as branched systems or systems with negative feedback loops.
The same approach can be used to derive the concentration connectivity theorems except one can consider either the case that focuses on a single species or a second case where the system equation is written to consider the effect on a distance species. | 1 | Biochemistry |
* Instead of relying on standard diffusion to transfer the proteins from the gel to the filter, electroblotting is commonly used because it removes the denaturing agent SDS thereby allowing the proteins to renature as they move to the filter.
* Skim milk is added to the filter before hybridizing with probes as it contains Bovine Serum Albumin (BSA) which prevents any unwanted or weak interactions of DNA to the nitrocellulose membrane.
* A rapid dimethylsulphate (DMS) protection assay can be used to identify non-specific binding vs. specific binding on blots.
* During the DNA probe hybridization step, defined amounts of salt are used to enhance specific interactions that occur between the DNA and proteins. | 1 | Biochemistry |
The stabilization of bismuth's +3 oxidation state due to the inert pair effect yields a plethora of organometallic bismuth-transition metal compounds and clusters with interesting electronics and 3D structures. | 0 | Organic Chemistry |
Intercepting an intercontinental ballistic missile (ICBM) in its boost phase requires imaging of the hard body as well as the rocket plumes. MWIR presents a strong signal from highly heated objects including rocket plumes, while LWIR produces emissions from the missile's body material. The US Army Research Laboratory reported that with their dual-band MWIR/LWIR technology, tracking of the Atlas 5 Evolved Expendable Launch Vehicles, similar in design to ICBMs, picked up both the missile body and plumage. | 7 | Physical Chemistry |
Agricultural chemistry often aims at preserving or increasing the fertility of soil with the goals of maintaining or improving the agricultural yield and improving the quality of the crop. Soils are analyzed with attention to the inorganic matter (minerals), which comprise most of the mass of dry soil, and organic matter, which consists of living organisms, their degradation products, humic acids and fulvic acids.
Fertilizers are a major consideration. While organic fertilizers are time-honored, their use has largely been displaced by chemicals produced from mining (phosphate rock) and the Haber-Bosch process. The use of these materials dramatically increased the rate at which crops are produced, which is able to support the growing human population. Common fertilizers include urea, ammonium sulphate, diammonium phosphate, and calcium ammonium phosphate. | 1 | Biochemistry |
Carbon sequestration is the process of storing carbon in a carbon pool. It plays a crucial role in mitigating climate change by reducing the amount of carbon dioxide in the atmosphere. There are two main types of carbon sequestration: biologic (also called biosequestration) and geologic. Biologic carbon sequestration is a naturally occurring process as part of the carbon cycle. Humans can enhance it through deliberate actions and use of technology. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These processes can be accelerated for example through changes in land use and agricultural practices, called carbon farming. Artificial processes have also been devised to produce similar effects. This approach is called carbon capture and storage. It involves using technology to capture and sequester (store) that is produced from human activities underground or under the sea bed.
Forests, kelp beds, and other forms of plant life absorb carbon dioxide from the air as they grow, and bind it into biomass. However, these biological stores are considered impermanent carbon sinks as the long-term sequestration cannot be guaranteed. For example, natural events, such as wildfires or disease, economic pressures and changing political priorities can result in the sequestered carbon being released back into the atmosphere.
Carbon dioxide that has been removed from the atmosphere can also be stored in the Earths crust by injecting it into the subsurface, or in the form of insoluble carbonate salts. The latter process is called mineral sequestration. These methods are considered non-volatile' because they not only remove carbon dioxide from the atmosphere but also sequester it indefinitely. This means the carbon is "locked away" for thousands to millions of years.
To enhance carbon sequestration processes in oceans the following technologies have been proposed: Seaweed farming, ocean fertilization, artificial upwelling, basalt storage, mineralization and deep sea sediments, adding bases to neutralize acids. However, none have achieved large scale application so far. | 5 | Photochemistry |
When comparing initiation in eukaryotes to prokaryotes, perhaps one of the first noticeable differences is the use of a larger 80S ribosome. Regulation of this process begins with the supply of methionine by a tRNA anticodon that basepairs AUG. This base pairing comes about by the scanning mechanism that ensues once the small 40S ribosomal subunit binds the 5 untranslated region (UTR) of mRNA. The usage of this scanning mechanism, in opposition to the Shine-Dalgarno sequence that was referenced in prokaryotes, is the ability to regulate translation through upstream RNA secondary structures. This inhibition of initiation through complex RNA structures may be circumvented in some cases by way of internal ribosomal entry sites (IRESs) that localize pre-initiation complexes (PIC) to the start site. In addition to this, the guidance of the PIC to the 5 UTR is coordinated by subunits of the PIC, known as eukaryotic initiation factors (eIFs). When some of these proteins are down-regulated through stresses, translation initiation is reduced by inhibiting cap dependent initiation, the activation of translation by binding eIF4E to the 5' 7-methylguanylate cap. eIF2 is responsible for coordinating the interaction between the Met-tRNA and the P-site of the ribosome. Regulation by phosphorylation of eIF2 is largely associated with the termination of translation initiation. Serine kinases, GCN2, PERK, PKR, and HRI are examples of detection mechanisms for differing cellular stresses that respond by slowing translation through eIF2 phosphorylation. | 1 | Biochemistry |
As mentioned earlier, the requirement for an atom to be a chirality center is that the atom must be sp hybridized with four different attachments. Because of this, all chirality centers are stereocenters. However, only under some conditions is the reverse true. Recall that a point can be considered a sterocenter with a minimum of three attachment points; stereocenters can be either sp or sp hybridized, as long as the interchanging any two different groups creates a new stereoisomer. This means that although all chirality centers are stereocenters, not every stereocenter is a chirality center.
Stereocenters are important identifiers for chiral or achiral molecules. As a general rule, if a molecule has no stereocenters, it is considered achiral. If it has at least one stereocenter, the molecule has the potential for chirality. However, there are some exceptions like meso compounds that make molecules with multiple stereocenters considered achiral. | 4 | Stereochemistry |
Some other plants live in association with a cyanobiont (cyanobacteria such as Nostoc) which fix nitrogen for them:
* Some lichens such as Lobaria and Peltigera
* Mosquito fern (Azolla species)
* Cycads
* Gunnera
* Blasia (liverwort)
* Hornworts
Some symbiotic relationships involving agriculturally-important plants are:
* Sugarcane and unclear endophytes
* Foxtail millet and Azospirillum brasilense
* Kallar grass and Azoarcus sp. strain BH72
* Rice and Herbaspirillum seropedicae
* Wheat and Klebsiella pneumoniae
* Maize landrace Sierra Mixe / olotón and various Bacteroidota and Pseudomonadota | 1 | Biochemistry |
Probably the most well-known receptors of peptidoglycan are the NOD-like receptors (NLRs), mainly NOD1 and NOD2. The NOD1 receptor is activated after iE-DAP (γ-d-glutamyl-meso-diaminopimelic acid) binding, while NOD2 recognizes MDP (muramyl dipeptide), by their LRR domains. Activation leads to self-oligomerization, resulting in activation of two signalling cascades. One triggers activation of NF-κB (through RIP2, TAK1 and IKK), second leads to MAPK signalling cascade. Activation of these pathways induces production of inflammatory cytokines and chemokines.
NOD1 is expressed by diverse cell types, including myeloid phagocytes, epithelial cells and neurons. NOD2 is expressed in monocytes and macrophages, epithelial intestinal cells, Paneth cells, dendritic cells, osteoblasts, keratinocytes and other epithelial cell types. As cytosolic sensors, NOD1 and NOD2 must either detect bacteria that enter the cytosol, or peptidoglycan must be degraded to generate fragments that must be transported into the cytosol for these sensors to function.
Recently, it was demonstrated that NLRP3 is activated by peptidoglycan, through a mechanism that is independent of NOD1 and NOD2. In macrophages, N-acetylglucosamine generated by peptidoglycan degradation was found to inhibit hexokinase activity and induce its release from the mitochondrial membrane. It promotes NLRP3 inflammasome activation through a mechanism triggered by increased mitochondrial membrane permeability.
NLRP1 is also considered as a cytoplasmic sensor of peptidoglycan. It can sense MDP and promote IL-1 secretion through binding NOD2. | 1 | Biochemistry |
The harmful effects of glutamate on the central nervous system were first observed in 1954 by T. Hayashi, a Japanese scientist who stated that direct application of glutamate caused seizure activity, though this report went unnoticed for several years. D. R. Lucas and J. P. Newhouse, after noting that "single doses of [20–30 grams of sodium glutamate in humans] have ... been administered intravenously without permanent ill-effects", observed in 1957 that a subcutaneous dose described as "a little less than lethal", destroyed the neurons in the inner layers of the retina in newborn mice. In 1969, John Olney discovered that the phenomenon was not restricted to the retina, but occurred throughout the brain, and coined the term excitotoxicity. He also assessed that cell death was restricted to postsynaptic neurons, that glutamate agonists were as neurotoxic as their efficiency to activate glutamate receptors, and that glutamate antagonists could stop the neurotoxicity.
In 2002, Hilmar Bading and co-workers found that excitotoxicity is caused by the activation of NMDA receptors located outside synaptic contacts. The molecular basis for toxic extrasynaptic NMDA receptor signaling was uncovered in 2020 when Hilmar Bading and co-workers described a death signaling complex that consists of extrasynaptic NMDA receptor and TRPM4. Disruption of this complex using NMDAR/TRPM4 interface inhibitors (also known as ‚interface inhibitors‘) renders extrasynaptic NMDA receptor non-toxic. | 1 | Biochemistry |
Mutatochrome (5,8-epoxy-β-carotene) is a carotenoid. It is the predominant carotenoid in the cap of the bolete mushroom Boletus luridus. | 1 | Biochemistry |
The following are reference ranges for D-dimer:
D-dimer increases with age. It has therefore been suggested to use a cutoff equal to patient’s age in years × 10 µg/L (or x 0.056 nmol/L) for patients aged over 50 years for the suspicion of venous thromboembolism (VTE), as it decreases the false positive rate without substantially increasing the false negative rate.
An alternative measurement of D-dimer is in fibrinogen equivalent units (FEU). The molecular weight of the fibrinogen molecule is about twice the size of the D-dimer molecule, and therefore 1.0 mcg/mL FEU is equivalent to 0.5 mcg/mL of d-dimer. | 1 | Biochemistry |
Plasmids are double-stranded extra chromosomal and generally circular DNA sequences that are capable of replication using the host cells replication machinery. Plasmid vectors minimalistically consist of an origin of replication that allows for semi-independent replication of the plasmid in the host. Plasmids are found widely in many bacteria, for example in Escherichia coli, but may also be found in a few eukaryotes, for example in yeast such as Saccharomyces cerevisiae'. Bacterial plasmids may be conjugative/transmissible and non-conjugative:
* conjugative - mediate DNA transfer through conjugation and therefore spread rapidly among the bacterial cells of a population; e.g., F plasmid, many R and some col plasmids.
* nonconjugative - do not mediate DNA through conjugation, e.g., many R and col plasmids.
Plasmids with specially-constructed features are commonly used in laboratory for cloning purposes. These plasmid are generally non-conjugative but may have many more features, notably a "multiple cloning site" where multiple restriction enzyme cleavage sites allow for the insertion of a transgene insert. The bacteria containing the plasmids can generate millions of copies of the vector within the bacteria in hours, and the amplified vectors can be extracted from the bacteria for further manipulation. Plasmids may be used specifically as transcription vectors and such plasmids may lack crucial sequences for protein expression. Plasmids used for protein expression, called expression vectors, would include elements for translation of protein, such as a ribosome binding site, start and stop codons. | 1 | Biochemistry |
DNA is a major example of a supramolecular polymer. protein Much effort has been develoted to related but synthetic materials. At the same time, their reversible and dynamic nature make supramolecular polymers bio-degradable, which surmounts hard-to-degrade issue of covalent polymers and makes supramolecular polymers a promising platform for biomedical applications. Being able to degrade in biological environment lowers potential toxicity of polymers to a great extent and therefore, enhances biocompatibility of supramolecular polymers. | 6 | Supramolecular Chemistry |
Several methods are known to recover carbonyl compounds from N,N-dialkylhydrazones. Procedures include oxidative, hydrolytic or reductive cleavage conditions and can be compatible with a wide range of functional groups. | 0 | Organic Chemistry |
Depletion gilding is a decorative process, with no significant industrial applications. It is not widely used in modern times, having been superseded by processes more suited to mass production, such as electroplating. Some individual artisans and small shops continue to practice it.
However, depletion gilding was widely used in antiquity. While it requires skill to execute it well, the process itself is technologically simple, and uses materials that are readily available to most ancient civilizations. Some form of depletion gilding has been used by nearly every culture that developed metalworking. The South American Sican culture in particular developed depletion gilding to a high art. Some ancient alloys, such as tumbaga, may have been developed specifically for use in depletion gilding. The technique was not known to be used by Anglo-Saxons until detailed examination with electron microscopes of treasures such as the Staffordshire Hoard revealed its use in the twenty-first century.
Certain cultures are thought to have attached mythical or spiritual significance to the process. Gold was considered sacred in many early civilizations and was highly valued in nearly all of them, and anything relating to it had the potential to take on cultural importance. Moreover, the ability to turn what appeared to be an object made of copper into what seemed to be pure gold would be very impressive. There is some speculation that depletion gilding may have contributed to the concepts of alchemy, a major goal of which was to physically transform one metal into another. | 8 | Metallurgy |
The bioavailability of levonorgestrel is approximately 95% (range 85 to 100%). The plasma protein binding of levonorgestrel is about 98%. It is bound 50% to albumin and 48% to SHBG. Levonorgestrel is metabolized in the liver, via reduction, hydroxylation, and conjugation (specifically glucuronidation and sulfation). Oxidation occurs primarily at the C2α and C16β positions, while reduction occurs in the A ring. 5α-Dihydrolevonorgestrel is produced as an active metabolite of levonorgestrel by 5α-reductase. The elimination half-life of levonorgestrel is 24 to 32 hours, although values as short as 8 hours and as great as 45 hours have been reported. About 20 to 67% of a single oral dose of levonorgestrel is eliminated in urine and 21 to 34% in feces. | 4 | Stereochemistry |
Phytoplankton are mostly made up of lignin and cellulose, which are broken down by oxidative mechanism, which consume oxygen. | 9 | Geochemistry |
The Tolman length (also known as Tolmans delta) measures the extent by which the surface tension of a small liquid drop deviates from its planar value. It is conveniently defined in terms of an expansion in , with the equimolar radius (defined below) of the liquid drop, of the pressure difference across the droplets surface:
In this expression, is the pressure difference between the (bulk) pressure of the liquid inside and the pressure of the vapour outside, and is the surface tension of the planar interface, i.e. the interface with zero curvature . The Tolman length is thus defined as the leading order correction in an expansion in .
The equimolar radius is defined so that the superficial density is zero, i.e., it is defined by imagining a sharp mathematical dividing surface with a uniform internal and external density, but where the total mass of the pure fluid is exactly equal to the real situation. At the atomic scale in a real drop, the surface is not sharp, rather the density gradually drops to zero, and the Tolman length captures the fact that the idealized equimolar surface does not necessarily coincide with the idealized tension surface.
Another way to define the Tolman length is to consider the radius dependence of the surface tension, . To leading order in one has:
Here denotes the surface tension (or (excess) surface free energy) of a liquid drop with radius , whereas denotes its value in the planar limit.
In both definitions (1) and (2) the Tolman length is defined as a coefficient in an expansion in and therefore does not depend on .
Furthermore, the Tolman length can be related to the radius of spontaneous curvature when one compares the free energy method of Helfrich with the method of Tolman:
Any result for the Tolman length therefore gives information about the radius of spontaneous curvature, . If the Tolman length is known to be positive (with ) the interface tends to curve towards the liquid phase, whereas a negative Tolman length implies a negative and a preferred curvature towards the vapour phase.
Apart from being related to the radius of spontaneous curvature, the Tolman length can be linked to the surface of tension. The surface of tension, positioned at , is defined as the surface for which the Young-Laplace equation holds exactly for all droplet radii:
where is the surface tension at the surface of tension. Using the Gibbs adsorption equation, Tolman himself showed that the Tolman length can be expressed in terms of the adsorbed amount at the surface of tension at coexistence
where ; the subscript zero to the density denotes the value at two-phase coexistence. It can be shown that the difference between the location of the surface of tension and of the equimolar dividing surface proposed by Gibbs yields the value of the Tolman length:
where the denote the locations of the corresponding surfaces making the magnitude of the Tolman length in the order of nanometers. | 7 | Physical Chemistry |
In the context of sputtering, the gas in the tube is called "carrier gas," because it carries the particles from the cathode. | 3 | Analytical Chemistry |
Prior to HPLC, scientists used benchtop column liquid chromatographic techniques. Liquid chromatographic systems were largely inefficient due to the flow rate of solvents being dependent on gravity. Separations took many hours, and sometimes days to complete. Gas chromatography (GC) at the time was more powerful than liquid chromatography (LC), however, it was obvious that gas phase separation and analysis of very polar high molecular weight biopolymers was impossible. GC was ineffective for many life science and health applications for biomolecules, because they are mostly non-volatile and thermally unstable at the high temperatures of GC. As a result, alternative methods were hypothesized which would soon result in the development of HPLC.
Following on the seminal work of Martin and Synge in 1941, it was predicted by Calvin Giddings, Josef Huber, and others in the 1960s that LC could be operated in the high-efficiency mode by reducing the packing-particle diameter substantially below the typical LC (and GC) level of 150 μm and using pressure to increase the mobile phase velocity. These predictions underwent extensive experimentation and refinement throughout the 60s into the 70s until these very days. Early developmental research began to improve LC particles, for example the historic Zipax, a superficially porous particle.
The 1970s brought about many developments in hardware and instrumentation. Researchers began using pumps and injectors to make a rudimentary design of an HPLC system. Gas amplifier pumps were ideal because they operated at constant pressure and did not require leak-free seals or check valves for steady flow and good quantitation. Hardware milestones were made at Dupont IPD (Industrial Polymers Division) such as a low-dwell-volume gradient device being utilized as well as replacing the septum injector with a loop injection valve.
While instrumentation developments were important, the history of HPLC is primarily about the history and evolution of particle technology. After the introduction of porous layer particles, there has been a steady trend to reduced particle size to improve efficiency. However, by decreasing particle size, new problems arose. The practical disadvantages stem from the excessive pressure drop needed to force mobile fluid through the column and the difficulty of preparing a uniform packing of extremely fine materials. Every time particle size is reduced significantly, another round of instrument development usually must occur to handle the pressure. | 3 | Analytical Chemistry |
The electric effect can be classified into two types, namely the +E effect and the -E effect. This classification is based on the direction of electron pair transfer. When the attacking reagent is electrophile, the +E effect is generally observed and π-electrons are transferred to the positively charged atom. When the attacking reagent is a nucleophile, there is generally an -E effect, where π electrons are transferred to atoms to which the attacking reagent will not bind. | 7 | Physical Chemistry |
In 2010, exometabolomics analysis of the cyanobacterium, Synechococcus sp. PCC 7002 by Baran, et al. revealed that this photoautotroph could deplete a diverse pool of exogenous metabolites. A follow-up exometabolomics study on sympatric microbial isolates from biological soil crust, which exist in communities with cyanobacteria in the desert soils of the Colorado Plateau, suggested that metabolite niche partitioning exists in these communities, where each isolate only utilizes 13-26% of metabolites from the soil | 1 | Biochemistry |
Paucimannosidic glycans span the base composition ManGlcNAc. Additional modifications with Fuc, Xyl and/or Galactose (Gal) are common in mammals ref, plants and invertebrates, respectively. Paucimannosidic glycans expressed by insects and nematodes are particularly rich in structural diversity. | 1 | Biochemistry |
Scintillation properties of organic-inorganic methylamonium (MA) lead halide perovskites under proton irradiation were first reported by Shibuya et al. in 2002 and the first γ-ray pulse height spectrum, although still with poor energy resolution, was reported on () by van Eijk et al. in 2008 . Birowosuto at al. studied the scintillation properties of 3-D and 2-D layered perovskites under X-ray excitation. MAPbBr () emits at 550 nm and MAPbI () at 750 nm which is attributed to exciton emission near the band gap of the compounds. In this first generation of Pb-halide perovskites the emission is strongly quenched at room temperature and less than 1 000 ph/MeV survive. At 10 K however intense emission is observed and write about yields up to 200 000 ph/MeV. The quenching is attributed to the small e-h binding energy in the exciton that decreases for Cl to Br to I . Interestingly one may replace the organic MA group with Cs+ to obtain full inorganic CsPbX halide perovskites. Depending on the Cl, Br, I content the triplet X-ray excited exciton emission can be tuned from 430 nm to 700 nm . One may also dilute Cs with Rb to obtain similar tuning. Above very recent developments demonstrate that the organic-inorganic and all inorganic Pb-halide perovskites have various interesting scintillation properties. However, the recent two-dimensional perovskite single crystals with light yields between 10 000 and 40 000 ph/MeV and decay times below 10 ns at room temperature will be more favorable as they may have much larger Stokes shift up to 200 nm in comparison with CsPbBr quantum dot scintillators and this is essential to prevent self reabsorption for scintillators.
More recently, a new material class first reported by Professor [https://www.chem.fsu.edu/~ma/ Biwu Ma's] research group, called 0D organic metal halide hybrid (OMHH), an extension of the perovskite materials. This class of materials exhibits strong exciton binding of hundreds of meV, resulting in their high photoluminescent quantum efficiency of almost unity. Their large stoke shift and reabsorption-free properties make them desirable. Their potential applications for scintillators have been reported by the same group, and others. In 2020,(C38H34P2)MnBr4 was reported to have a light yield up to 80 000 Photon/MeV despite its low Z compared to traditional all inorganic. Impressive light yields from other 0D OMHH have been reported. There is a great potential to realize new generation scintillators from this material class. However, they are limited by their relatively long response time in microseconds, which is an area of intense research. | 5 | Photochemistry |
Hydrides add to give hydroxylamines. Reducing Lewis acids (e.g. metals, Sulfur dioxide|) deoxygenate to the imine instead. | 0 | Organic Chemistry |
Most commonly used post treatment, where chlorine is dissolved in water to form and hydrochloric acid hypochlorous acid. The latter act as a disinfectant that is able to eliminate pathogens such as bacteria, viruses and protozoa by penetrating the cell walls. | 3 | Analytical Chemistry |
Broadening in laser physics is a physical phenomenon that affects the spectroscopic line shape of the laser emission profile. The laser emission is due to the (excitation and subsequent) relaxation of a quantum system (atom, molecule, ion, etc.) between an excited state (higher in energy) and a lower one. These states can be thought of as the eigenstates of the energy operator. The difference in energy between these states is proportional to the frequency/wavelength of the photon emitted. Since this energy difference has a fluctuation, then the frequency/wavelength of the "macroscopic emission" (the beam) will have a certain width (i.e. it will be "broadened" with respect to the "ideal" perfectly monochromatic emission).
Depending on the nature of the fluctuation, there can be two types of broadening. If the fluctuation in the frequency/wavelength is due to a phenomenon that is the same for each quantum emitter, there is homogeneous broadening, while if each quantum emitter has a different type of fluctuation, the broadening is inhomogeneous.
Examples of situations where the fluctuation is the same for each system (homogeneous broadening) are natural or lifetime broadening, and collisional or pressure broadening. In these cases each system is affected "on average" in the same way (e.g. by the collisions due to the pressure).
The most frequent situation in solid state systems where the fluctuation is different for each system (inhomogeneous broadening) is when because of the presence of dopants, the local electric field is different for each emitter, and so the Stark effect changes the energy levels in an inhomogeneous way. The homogeneous broadened emission line will have a Lorentzian profile (i.e. will be best fitted by a Lorentzian function), while the inhomogeneously broadened emission will have a Gaussian profile. One or more phenomena may be present at the same time, but if one has a wider fluctuation, it will be the one responsible for the character of the broadening.
These effects are not limited to laser systems, or even to optical spectroscopy. They are relevant in magnetic resonance as well, where the frequency range is in the radiofrequency region for NMR, and one can also refer to these effects in EPR where the lineshape is observed at fixed (microwave) frequency and in a magnetic field range. | 7 | Physical Chemistry |
The Hill reaction is the light-driven transfer of electrons from water to Hill reagents (non-physiological oxidants) in a direction against the chemical potential gradient as part of photosynthesis. Robin Hill discovered the reaction in 1937. He demonstrated that the process by which plants produce oxygen is separate from the process that converts carbon dioxide to sugars. | 5 | Photochemistry |
;AVS: Assignment validation suite ([https://www.ncbi.nlm.nih.gov/pubmed/14872126 AVS]) checks the chemical shifts list in BioMagResBank (BMRB) format for problems.
;PSVS: Protein Structure Validation Server at the NESG based on information retrieval statistics
;PROSESS: PROSESS (Protein Structure Evaluation Suite & Server) is a new web server that offers an assessment of protein structural models by NMR chemical shifts as well as NOEs, geometrical, and knowledge-based parameters.
;LACS:Linear analysis of chemical shifts is used for absolute referencing of chemical shift data. | 1 | Biochemistry |
Superconductivity in UPdAl has a critical temperature of 2.0K and a critical field around 3T. The critical field does not show anisotropy despite the hexagonal crystal structure.
For heavy-fermion superconductors it is generally believed that the coupling mechanism cannot be phononic in nature. In contrast to many other unconventional superconductors, for UPdAl there actually exists strong experimental evidence (namely from neutron scattering and tunneling spectroscopy ) that superconductivity is magnetically mediated.
In the first years after the discovery of UPdAl it was actively discussed whether its superconducting state can support a Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase, but this suggestion was later refuted. | 8 | Metallurgy |
Methyl vinyl ketone, ethyl acetoacetate, and diethyl-methyl-(3-oxo-butyl)-ammonium iodide react to form a cyclic aldol product. Sodium methoxide is added to generate Hagemann's ester. | 0 | Organic Chemistry |
DiffractGUI allows for an automated analysis of diffraction patterns and high-resolution images of single crystal or limited number of crystallites. It is able to determine crystal orientation, index individual diffraction spots and measure interplanar angles and distances in picometric precision. The input image may depict:
* selected area diffraction pattern,
* high-resolution image,
* nanodiffraction pattern or
* convergent beam electron diffraction.
The input image is processed in the following steps:
# Preprocessing with accordance to the settings and image nature (resolution and noise reduction, Fourier transform for direct space images etc.).
# Detection of diffraction reflections at various scales (difference of Gaussians typically used for spot detection, Hough transform for CBED disk detection).
# The strongest detections are selected across the scale space.
# A regular lattice is fit to the set of the strongest detections using RANSAC algorithm.
# Lengths and angles of the lattice basis vectors are measured.
# Crystal lattice orientation is determined and diffraction reflections are identified using theoretical parameters of the sample material.
Compared to human evaluation, considers tens or even hundreds of diffraction spots at once and, therefore, can localize the pattern with sub-pixel precision. | 3 | Analytical Chemistry |
SahysMod is a computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including the use of ground water for irrigation, and several crop rotation schedules, whereby the spatial variations are accounted for through a network of polygons. | 9 | Geochemistry |
Metals, and specifically rare-earth elements, form numerous chemical complexes with boron. Their crystal structure and chemical bonding depend strongly on the metal element M and on its atomic ratio to boron. When B/M ratio exceeds 12, boron atoms form B icosahedra which are linked into a three-dimensional boron framework, and the metal atoms reside in the voids of this framework. Those icosahedra are basic structural units of most allotropes of boron and boron-rich rare-earth borides. In such borides, metal atoms donate electrons to the boron polyhedra, and thus these compounds are regarded as electron-deficient solids.
The crystal structures of many boron-rich borides can be attributed to certain types including MgAlB, YB, REBSi, BC and other, more complex types such as REBCSi. Some of these formulas, for example BC, YB and MgAlB, historically reflect the idealistic structures, whereas the experimentally determined composition is nonstoichiometric and corresponds to fractional indexes. Boron-rich borides are usually characterized by large and complex unit cells, which can contain more than 1500 atomic sites and feature extended structures shaped as "tubes" and large modular polyhedra ("superpolyhedra"). Many of those sites have partial occupancy, meaning that the probability to find them occupied with a certain atom is smaller than one and thus that only some of them are filled with atoms. Scandium is distinguished among the rare-earth elements by that it forms numerous borides with uncommon structure types; this property of scandium is attributed to its relatively small atomic and ionic radii.
Crystals of the specific rare-earth boride YB are used as X-ray monochromators for selecting X-rays with certain energies (in the 1–2 keV range) out of synchrotron radiation. Other rare-earth borides may find application as thermoelectric materials, owing to their low thermal conductivity; the latter originates from their complex, "amorphous-like", crystal structure. | 3 | Analytical Chemistry |
Dynamic systems are collections of discrete molecular components that can reversibly assemble and disassemble. Systems may include multiple interacting species leading to competing reactions. | 6 | Supramolecular Chemistry |
Plastoglobuli (singular plastoglobulus, sometimes spelled plastoglobule(s)), are spherical bubbles of lipids and proteins about 45–60 nanometers across. They are surrounded by a lipid monolayer. Plastoglobuli are found in all chloroplasts, but become more common when the chloroplast is under oxidative stress, or when it ages and transitions into a gerontoplast. Plastoglobuli also exhibit a greater size variation under these conditions. They are also common in etioplasts, but decrease in number as the etioplasts mature into chloroplasts.
Plastoglobuli contain both structural proteins and enzymes involved in lipid synthesis and metabolism. They contain many types of lipids including plastoquinone, vitamin E, carotenoids and chlorophylls.
Plastoglobuli were once thought to be free-floating in the stroma, but it is now thought that they are permanently attached either to a thylakoid or to another plastoglobulus attached to a thylakoid, a configuration that allows a plastoglobulus to exchange its contents with the thylakoid network. In normal green chloroplasts, the vast majority of plastoglobuli occur singularly, attached directly to their parent thylakoid. In old or stressed chloroplasts, plastoglobuli tend to occur in linked groups or chains, still always anchored to a thylakoid.
Plastoglobuli form when a bubble appears between the layers of the lipid bilayer of the thylakoid membrane, or bud from existing plastoglobuli—though they never detach and float off into the stroma. Practically all plastoglobuli form on or near the highly curved edges of the thylakoid disks or sheets. They are also more common on stromal thylakoids than on granal ones. | 5 | Photochemistry |
Gases will dissolve in liquids to an extent that is determined by the equilibrium between the undissolved gas and the gas that has dissolved in the liquid (called the solvent). The equilibrium constant for that equilibrium is:
where:
* = the equilibrium constant for the solvation process
* = partial pressure of gas in equilibrium with a solution containing some of the gas
* = the concentration of gas in the liquid solution
The form of the equilibrium constant shows that the concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution. This statement is known as Henrys law and the equilibrium constant is quite often referred to as the Henrys law constant.
Henry's law is sometimes written as:
where is also referred to as the Henrys law constant. As can be seen by comparing equations () and () above, is the reciprocal of . Since both may be referred to as the Henrys law constant, readers of the technical literature must be quite careful to note which version of the Henry's law equation is being used.
Henry's law is an approximation that only applies for dilute, ideal solutions and for solutions where the liquid solvent does not react chemically with the gas being dissolved. | 7 | Physical Chemistry |
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