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A tetrose diphosphate molecule, D-threose 2,4-diphosphate, was discovered to be an inhibitor of glyceraldehyde 3-phosphate dehydrogenase. Glyceraldehyde 3-phosphate dehydrogenase is the sixth enzyme used in the glycolysis pathway, and its function is to convert glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate. This tetrose diphosphate molecule inhibits the G3P dehydrogenase from performing catalysis because it oxidizes the enzyme by binding to it at the active site. When tetrose diphosphate is bound to the enzyme, the active site of the enzyme is blocked; therefore phosphorolysis of G3P is unable to occur. High concentrations of tetrose diphosphate must be used to outcompete the substrate, G3P, and block the function of G3P dehydrogenase. With the function of glyceraldehyde 3-phosphate dehydrogenase lost, glycolysis cannot proceed.
D-erythrose 4-phosphate was found to be an inhibitor of phosphoglucose isomerase. Phosphoglucose isomerase is the second enzyme in the glycolysis pathway, and its role is to convert glucose 6-phosphate into fructose 6-phosphate.
In both of these cases, the tetrose is an inhibitor of an enzyme in the glycolysis pathway, preventing it from proceeding onward. | 1 | Biochemistry |
Low-speed rear-stage turbining occurs with excessive negative incidence leading to a pressure ratio less than one and the compressor stage absorbing power from the airflow.
Two examples where crossing the surge line prevented accelerating to high speed occurred with the first designs of the Rolls-Royce Avon and the IAE V2500 and required major compressor redesigns. Rotating stall at low corrected speeds caused blade failures on early axial compressors. | 7 | Physical Chemistry |
Because primers are designed to have low complementarity to each other, they may anneal (step I in the figure) only at low temperature, e.g. room temperature, such as during the preparation of the reaction mixture. Although DNA polymerases used in PCR are most active around 70 °C, they have some polymerizing activity also at lower temperatures, which can cause DNA synthesis from primers after annealing to each other. Several methods have been developed to prevent PDs formation until the reaction reaches working temperature (60-70 °C), and these include initial inhibition of the DNA polymerase, or physical separation of reaction components reaction until the reaction mixture reaches the higher temperatures. These methods are referred to as hot-start PCR.
Wax: in this method the enzyme is spatially separated from the reaction mixture by wax that melts when the reaction reaches high temperature.
Slow release of magnesium: DNA polymerase requires magnesium ions for activity, so the magnesium is chemically separated from the reaction by binding to a chemical compound, and is released into the solution only at high temperature
Non-covalent binding of inhibitor: in this method a peptide, antibody or aptamer are non-covalently bound to the enzyme at low temperature and inhibit its activity. After an incubation of 1–5 minutes at 95 °C, the inhibitor is released and the reaction starts.
Cold-sensitive Taq polymerase: is a modified DNA polymerase with almost no activity at low temperature.
Chemical modification: in this method a small molecule is covalently bound to the side chain of an amino acid in the active site of the DNA polymerase. The small molecule is released from the enzyme by incubation of the reaction mixture for 10–15 minutes at 95 °C. Once the small molecule is released, the enzyme is activated. | 1 | Biochemistry |
The "diarylethenes" were first introduced by Irie and have since gained widespread interest, largely on account of their high thermodynamic stability. They operate by means of a 6-pi electrocyclic reaction, the thermal analog of which is impossible due to steric hindrance. Pure photochromic dyes usually have the appearance of a crystalline powder, and in order to achieve the color change, they usually have to be dissolved in a solvent or dispersed in a suitable matrix. However, some diarylethenes have so little shape change upon isomerization that they can be converted while remaining in crystalline form. | 5 | Photochemistry |
As the Haber–Weiss reaction depends on the presence of both Fe and Fe in solution, its kinetics is influenced by the respective solubilities of both species whose are directly function of the solution pH. As Fe is about 100 times less soluble than Fe in natural waters at near-neutral pH, the ferric ion concentration is the limiting factor for the reaction rate. The reaction can only proceed with a fast enough rate under sufficiently acidic conditions. At high pH, under alkaline conditions, the reaction considerably slows down because of the precipitation of Fe(OH) which notably lowers the concentration of the Fe species in solution.
Moreover, the pH value also directly influences the acid-base dissociation equilibrium involving the hydroperoxyl and the superoxide radicals (pK = 4.7) as mentioned above. | 2 | Environmental Chemistry |
Traditionally, chemical sensing has been approached with a system that contains a covalently bound indicator to a receptor though a linker. Once the analyte binds, the indicator changes color or fluoresces. This technique is called the indicator-spacer-receptor approach (ISR). In contrast to ISR, indicator-displacement assay (IDA) utilizes a non-covalent interaction between a receptor (the host), indicator, and an analyte (the guest). Similar to ISR, IDA also utilizes colorimetric (C-IDA) and fluorescence (F-IDA) indicators. In an IDA assay, a receptor is incubated with the indicator. When the analyte is added to the mixture, the indicator is released to the environment. Once the indicator is released it either changes color (C-IDA) or fluoresces (F-IDA).
IDA offers several advantages versus the traditional ISR chemical sensing approach. First, it does not require the indicator to be covalently bound to the receptor. Secondly, since there is no covalent bond, various indicators can be used with the same receptor. Lastly, the media in which the assay may be used is diverse.
Chemical sensing techniques such as C-IDA have biological implications. For example, protamine is a coagulant that is routinely administered after cardiopulmonary surgery that counter acts the anti-coagulant activity of herapin. In order to quantify the protamine in plasma samples, a colorimetric displacement assay is used. Azure A dye is blue when it is unbound, but when it is bound to herapin, it shows a purple color. The binding between Azure A and heparin is weak and reversible. This allows protamine to displace Azure A. Once the dye is liberated it displays a purple color. The degree to which the dye is displaced is proportional to the amount of protamine in the plasma.
F-IDA has been used by Kwalczykowski and co-workers to monitor the activities of helicase in E.coli. In this study they used thiazole orange as the indicator. The helicase unwinds the dsDNA to make ssDNA. The fluorescence intensity of thiazole orange has a greater affinity for dsDNA than ssDNA and its fluorescence intensity increases when it is bound to dsDNA than when it is unbound. | 6 | Supramolecular Chemistry |
The phrase "cell engineering" was first used in a published paper in 1968 to describe the process of improving fuel cells. The term was then adopted by other papers until the more specific "fuel-cell engineering" was used.
The first use of the term in a biological context was in 1971 in a paper which describes methods to graft reproductive caps between algae cells. Despite the rising popularity of the phrase, there remains unclear boundaries between cell engineering and other forms of biological engineering. | 1 | Biochemistry |
Carbolithiation is the addition of an organolithium reagent across a carbon-carbon pi-bond. The organolithium reagents used in this transformation can be commercial (such as n-butyllithium) or can be generated through deprotonation or lithium-halogen exchange. Both inter- and intramolecular examples of carbolithiation exist and can be used in synthesis to generate complexity. Organolithiums are highly reactive chemicals and often the resulting organolithium reagent generated from the carbolithiation can continue to react with electrophiles or remaining starting material (resulting in polymerization). This reaction has been rendered enantioselective through the use of sparteine, which can chelate the lithium ion and induce chirality. Today, this is not a common strategy due to a shortage of natural sparteine. However, recent advances in the synthesis of sparteine surrogates and their effective application in carbolithiation have reactivated interest in this strategy.
Another demonstration of this reaction type is an alternative route to tamoxifen starting from diphenylacetylene and ethyllithium: The capturing electrophile here is triisopropyl borate forming the boronic acid R–B(OH). The second step completing tamoxifen is a Suzuki reaction.
As a consequence of the high reactivity of organolithiums as strong bases and strong nucleophiles, the substrate scope of the carbolithiation is generally limited to chemicals that do not contain acidic or electrophilic functional groups. | 0 | Organic Chemistry |
Starting with a technique commonly used to deposit molecules on a solid surface, Langmuir–Blodgett deposition, scientists are able to assemble phospholipid membranes of arbitrary complexity layer by layer. These artificial phospholipid membranes support functional insertion both of purified and of in situ expressed membrane proteins. The technique could help astrobiologists understand how the first living cells originated. | 9 | Geochemistry |
The fraction of absorbed photosynthetically active radiation (FAPAR, sometimes also noted fAPAR or fPAR) is the fraction of the incoming solar radiation in the photosynthetically active radiation spectral region that is absorbed by a photosynthetic organism, typically describing the light absorption across an integrated plant canopy.
This biophysical variable is directly related to the primary productivity of photosynthesis and some models use it to estimate the assimilation of carbon dioxide in vegetation in conjunction with the leaf area index. FAPAR can also be used as an indicator of the state and evolution of the vegetation cover; with this function, it advantageously replaces the Normalized Difference Vegetation Index (NDVI), provided it is itself properly estimated.
FAPAR can be directly measured on the ground, by putting a spectrometer above and below canopy cover. On a larger scale, however, it is estimated from space measurements in the solar spectral range and a number of state of the art algorithms have been proposed to derive this important environmental variable. Currently, there are some remote sensing products of FAPAR, such as AVHRR and MODIS.
FAPAR is one of the 50 Essential Climate Variables recognized by the UN Global Climate Observing System (GCOS) as necessary to characterize the climate of the Earth. GCOS has issued specific recommendations to monitor this variable systematically, both through a reanalysis of existing databases and in the future with current and forthcoming instruments. | 5 | Photochemistry |
N1-methyladenosine is a modified nucleoside in which a methyl group is added to N1 of the adenosine base. This modification introduces a positive charge on the nitrogen atom to which the methyl group is added, because the modified nitrogen donates its lone pair to the carbon atom of the methyl group in order to form a bond. N1-methyladenosine modification is thought to regulate tRNA and rRNA stability, as well as potentially alter protein-RNA interactions or RNA secondary structures. This modification results in the melting of double-stranded RNA, due to alterations in the RNA structure. The N1-methyladenosine modification is less common than the mA modification, with modified transcripts usually only containing a single mA modification, whereas they may contain several mA residues.
Studies of these modifications have been slow to advance due to a lack of sound methodology to locate and identify them. A few methods, such as MeRIP-seq and mA-ID-seq, have been developed, but the particular adenosine that is modified still cannot be identified. A computational tool based on the data generated from these methods called RAMPed has been developed to try to identify these particular modifications.
Disease
Modification of m1a is of interest regarding its considerable correlation with cancer biology and tumorigenesis. Involvement of m1a may be organized under the categories of proliferation, invasion, cell death, tumor microenvironment, or cancer metabolism. Cancer cell proliferation has been found to be promoted by specific m1a “writers”. For example, the regulator TRMT6 has been found to be overexpressed in individuals with glioma, a cancer marked by the inappropriate proliferation of glial cells of the brain or spinal cord. Additionally, regulation of ALKBH3 has been found to support and bolster cancer cell invasiveness in certain breast and ovarian cancers. | 1 | Biochemistry |
Le Bel-vant Hoff rule states that for a structure with n asymmetric carbon atoms, there is a maximum of 2 different stereoisomers possible. As an example, -glucose is an aldohexose and has the formula CHO. Four of its six carbon atoms are stereogenic, which means -glucose is one of 2=16 possible stereoisomers. | 4 | Stereochemistry |
Upon initial binding to the LRR region of FSHR, FSH reshapes its conformation to form a new pocket. FSHR then inserts its sulfotyrosine from the hinge loop into the pockets and activates the 7-helical transmembrane domain. This event leads to a transduction of the signal that activates the G protein that is bound to the receptor internally. With FSH attached, the receptor shifts conformation and, thus, mechanically activates the G protein, which detaches from the receptor and activates the cAMP system.
It is believed that a receptor molecule exists in a conformational equilibrium between active and inactive states. The binding of FSH to the receptor shifts the equilibrium between active and inactive receptors. FSH and FSH-agonists shift the equilibrium in favor of active states; FSH antagonists shift the equilibrium in favor of inactive states. For a cell to respond to FSH, only a small percentage (~1%) of receptor sites need to be activated. | 1 | Biochemistry |
The developing embryo expresses cannabinoid receptors early in development that are responsive to anandamide secreted in the uterus. This signaling is important in regulating the timing of embryonic implantation and uterine receptivity. In mice, it has been shown that anandamide modulates the probability of implantation to the uterine wall. For example, in humans, the likelihood of miscarriage increases if uterine anandamide levels are too high or low. These results suggest that intake of exogenous cannabinoids (e.g., cannabis) can decrease the likelihood for pregnancy for women with high anandamide levels, and alternatively, it can increase the likelihood for pregnancy in women whose anandamide levels were too low. | 1 | Biochemistry |
The biosynthesis of BC200 RNA occurs at the cell body of a neuron and requires upstream promoter elements, downstream internal promoter elements (intragenic A and B boxes), at least two transcription factor binding sites, a TATA-like sequence, TATA-box binding protein (TBP), and RNA polymerase III.
There is a deletion of sequences between -100 and -1 in the DNA that blocks transcription activity, revealing that the transcription complex must interact with this 100-bp sequence of the upstream region for proper synthesis of BC200 RNA. The TATA-box binding protein (TBP) binds here, and when inhibited, BC200 RNA levels decrease, indicating that the 100 base pair region and TBP are critical players in the biosynthesis of BC200 RNA.
In addition to upstream elements, there is an upstream TATGAAA sequence (similar to TATA box sequence) at positions -28 to -22 which, when deleted, compromises transcription, revealing this TATA-like sequence as another critical player in the synthesis of BC200 RNA. However, transcription is not dependent on the TATA-box binding protein binding to the TATA-like sequence.
Both upstream and internal promoter elements are also essential for BC200 RNA synthesis. There are two types of upstream promoter elements in the 100 base pair region: one proximal to the transcription start site and associated with downstream transcription factor binding sites, and the other between nucleotides -36 and -100 and not associated with downstream binding sites. The internal promoter elements are intragenic A and B boxes with A located at position +5 to +15 and B located at position +78 to +88. Any mutation in these boxes can result in a decrease of BC200 RNA.
Because BC200 RNA acts as a translational regulator, it is then transported to the dendrites to bind to specific proteins involved in translation and inhibit their activity (see next section). | 1 | Biochemistry |
Applied spectroscopy is the application of various spectroscopic methods for the detection and identification of different elements or compounds to solve problems in fields like forensics, medicine, the oil industry, atmospheric chemistry, and pharmacology. | 7 | Physical Chemistry |
In the Arctic, commercial fisheries are threatened because acidification harms calcifying organisms which form the base of the Arctic food webs (pteropods and brittle stars, see above). Acidification threatens Arctic food webs from the base up. Arctic food webs are considered simple, meaning there are few steps in the food chain from small organisms to larger predators. For example, pteropods are "a key prey item of a number of higher predators – larger plankton, fish, seabirds, whales". Both pteropods and sea stars serve as a substantial food source and their removal from the simple food web would pose a serious threat to the whole ecosystem. The effects on the calcifying organisms at the base of the food webs could potentially destroy fisheries. | 9 | Geochemistry |
Monoclonal antibodies are structurally identical immunoglobulin molecules with identical epitope-specificity (all of them bind with the same epitope with same affinity) as against their polyclonal counterparts which have varying affinities for the same epitope.
They are usually not produced in a natural immune response, but only in diseased states like multiple myeloma, or through specialized laboratory techniques. Because of their specificity, monoclonal antibodies are used in certain applications to quantify or detect the presence of substances (which act as antigen for the monoclonal antibodies), and for targeting individual cells (e.g. cancer cells). Monoclonal antibodies find use in various diagnostic modalities (see: western blot and immunofluorescence) and therapies—particularly of cancer and diseases with autoimmune component. But, since virtually all responses in nature are polyclonal, it makes production of immensely useful monoclonal antibodies less straightforward. | 1 | Biochemistry |
*[http://nanocrystallography.research.pdx.edu/search/edu/ Educational Subset of the Crystallography Open Database (EDU-COD)] (specialization: crystal and molecule structures for college education, access: free, size: medium)
*[https://web.archive.org/web/20070403082355/http://xpdb.nist.gov:8060/BMCD4/ Biological Macromolecule Crystallization Database (BMCD)] (specialization: crystallization of biological macromolecules, access: free, size: medium)
*[http://nanocrystallography.research.pdx.edu/search/cmd/ Crystal Morphology Database (CMD)] (specialization: morphology of crystals, access: free, size: very small)
*[http://www.hypotheticalzeolites.net/DATABASE/DEEM_REFINED/ Database of Hypothetical Structures] (specialization: predicted zeolite-like crystal structures, access: free, size: large)
*[http://www.iza-structure.org/databases/ Database of Zeolite Structures] (specialization: crystal structures of zeolites, access: free, size: small)
*[http://hmofs.northwestern.edu/hc/crystals.php Hypothetical MOFs Database] (specialization: predicted metal-organic framework crystal structures, access: free, size: large)
*[http://www.cryst.ehu.es/icsdb/index.html Incommensurate Structures Database] (specialization: incommensurate structures, access: free, size: small)
*[https://web.archive.org/web/20130515052529/http://www.cinam.univ-mrs.fr/mpcd/ Marseille Protein Crystallization Database (MPCD)] (specialization: crystallization of biological macromolecules, access: free, size: medium)
*[https://web.archive.org/web/20120806204613/http://helios.princeton.edu/mofomics/ MOFomics] (specialization: pore structures of metal-organic frameworks, access: free, size: medium)
*[http://nanocrystallography.research.pdx.edu/search/ncd/ Nano-Crystallography Database (NCD)] (specialization: crystal structures of nanometer sized crystallites, access: free, size: small)
*[https://web.archive.org/web/20120112115407/http://www.nist.gov/srd/nist42.cfm NIST Surface Structure Database] (specialization: surface and interface structures, access: restricted, size: small-medium)
*[http://cod.ibt.lt/pcod/index.html Predicted Crystallography Open Database (PCOD)] (spezialization: predicted crystal structures of organics, metal-organics, metals, alloys, intermetallics, and inorganics, access: free, size: very large)
*[http://www.crystallography.net/tcod/ Theoretical Crystallography Open Database (TCOD)] (spezialization: crystal structures of organics, metal-organics, metals, alloys, intermetallics, and inorganics that were refined or predicted from density functional theory with some experimental input, access: free, size: small)
*[https://web.archive.org/web/20140524081408/http://helios.princeton.edu/zeomics/ ZEOMICS] (specialization: pore structures of zeolites, access: free, size: small) | 7 | Physical Chemistry |
Cyclooxygenase and cytochrome P450 oxidase act upon docosatetraenoic acid to produce dihomoprostaglandins, dihomo-epoxyeicosatrienoic acids, and dihomo-EETs. | 1 | Biochemistry |
The substitution of all electronegative substituents in trichloroacetonitrile by nucleophilic attack of alkoxide anions produces orthocarbonic acid esters in high yield.
Due to the high reactivity of the chlorine atoms, trichloroacetonitrile can be used (especially in combination with triphenylphosphine) to convert allylic alcohols into the corresponding allylic chlorides.
With carboxylic acids, acyl chlorides are obtained.
Due to the mild reaction conditions, the ClCCN/PPh system is also suitable for the activation of carboxylic acids and their linkage with supported amino compounds to amides (peptides) in solid-phase syntheses. From sulfonic acids, the corresponding sulfochlorides are formed analogously. In an analogous manner, the activation of diphenylphosphoric acid with ClCCN/PPh and reaction with alcohols or amines proceeds to the corresponding phosphoric acid esters or amides in a gentle and efficient one-pot reaction.
Also, phenolic hydroxy groups in nitrogen-containing aromatics can be converted into the chlorine compounds.
In a Hoesch reaction, aromatic hydroxyketones are formed in the reaction of substituted phenols with trichloroacetonitrile, for example from 2-methyl phenol the 2-trichloroacyl derivative in 70% yield.
The electron-withdrawing effect of the trichloromethyl group activates the nitrile group of trichloroacetonitrile for the attack of nucleophilic oxygen, nitrogen and sulfur compounds. For example, alcohols give O-alkyltrichloroacetimidates under basic catalysis in a direct and reversible addition, which can be isolated as stable and less hydrolysis-sensitive adducts.
With primary and secondary amines, N-substituted trichloroacetamidines are formed in a smooth reaction with good yields, which can be purified by vacuum distillation and are obtained as colorless, malodorous liquids. Reaction with ammonia and then with anhydrous hydrogen chloride gives the solid trichloroacetamidine hydrochloride, the starting compound for the fungicide etridiazole.
In academic research, trichloroacetonitrile is used as a reagent in the Overman rearrangement, converting allylic alcohols into allylic amines. The reaction is based on a [3,3]-sigmatropic and diastereoselective rearrangement.
Benzyl trichloroacetimidate is easily accessible from benzyl alcohol and trichloroacetonitrile. Benzyl trichloroacetimidate is useful as a benzylating reagent for sensitive alcohols under mild conditions and to preserve chirality. | 0 | Organic Chemistry |
For most clinical methods using ICP-MS, there is a relatively simple and quick sample prep process. The main component to the sample is an internal standard, which also serves as the diluent. This internal standard consists primarily of deionized water, with nitric or hydrochloric acid, and Indium and/or Gallium. The addition of volatile acids allows for the sample to decompose into its gaseous components in the plasma which minimizes the ability for concentrated salts and solvent loads to clog the cones and contaminate the instrument. Depending on the sample type, usually 5 mL of the internal standard is added to a test tube along with 10–500 microliters of sample. This mixture is then vortexed for several seconds or until mixed well and then loaded onto the autosampler tray.
For other applications that may involve very viscous samples or samples that have particulate matter, a process known as sample digestion may have to be carried out, before it can be pipetted and analyzed. This adds an extra first step to the above process, and therefore makes the sample prep more lengthy. | 3 | Analytical Chemistry |
Compared with vertebrates, insects and crustaceans possess a number of structurally unusual hormones such as the juvenile hormone, a sesquiterpenoid. | 1 | Biochemistry |
Introduced in 2007, ChIP sequencing (ChIP-seq) is a technology that uses chromatin immunoprecipitation to crosslink the proteins of interest to the DNA but then instead of using a micro-array, it uses the more accurate, higher throughput method of sequencing to localize interaction points.
DamID is an alternative method that does not require antibodies.
ChIP-exo uses exonuclease treatment to achieve up to single base pair resolution.
CUT&RUN sequencing uses antibody recognition with targeted enzymatic cleavage to address some technical limitations of ChIP. | 1 | Biochemistry |
Hot corrosion can affect gas turbines operating in high salt environments (e.g., near the ocean). Salts, including chlorides and sulfates, are ingested by the turbines and deposited in the hot sections of the engine; other elements present in fuels also form salts, e.g. vanadates. The heat from the engine melts these salts which then can flux the passivating oxide layers on the metal components of the engine, allowing corrosion to occur at an accelerated rate. | 8 | Metallurgy |
Zinc has been recognized as a messenger, able to activate signalling pathways. Many of these pathways provide the driving force in aberrant cancer growth. They can be targeted through ZIP transporters. | 1 | Biochemistry |
Zinc is an efficient Lewis acid, making it a useful catalytic agent in hydroxylation and other enzymatic reactions. The metal also has a flexible coordination geometry, which allows proteins using it to rapidly shift conformations to perform biological reactions. Two examples of zinc-containing enzymes are carbonic anhydrase and carboxypeptidase, which are vital to the processes of carbon dioxide () regulation and digestion of proteins, respectively.
In vertebrate blood, carbonic anhydrase converts into bicarbonate and the same enzyme transforms the bicarbonate back into for exhalation through the lungs. Without this enzyme, this conversion would occur about one million times slower at the normal blood pH of 7 or would require a pH of 10 or more. The non-related β-carbonic anhydrase is required in plants for leaf formation, the synthesis of indole acetic acid (auxin) and alcoholic fermentation.
Carboxypeptidase cleaves peptide linkages during digestion of proteins. A coordinate covalent bond is formed between the terminal peptide and a C=O group attached to zinc, which gives the carbon a positive charge. This helps to create a hydrophobic pocket on the enzyme near the zinc, which attracts the non-polar part of the protein being digested. | 1 | Biochemistry |
Aminomethanol or methanolamine is the amino alcohol with the chemical formula of HNCHOH. With an amino group and an alcohol group on the same carbon atom, the compound is also an hemiaminal.
In aqueous solution, methanolamine exists in equilibrium with formaldehyde and ammonia. It is an intermediate en route to hexamethylenetetramine. The reaction can be conducted in gas phase and in solution. | 0 | Organic Chemistry |
The conversion to mole fraction is given by
where is the average molar mass of the solution, is the density of the solution.
A simpler relation can be obtained by considering the total molar concentration, namely, the sum of molar concentrations of all the components of the mixture: | 3 | Analytical Chemistry |
Electrochemical regeneration of activated carbon adsorbents such as granular activated carbon present an alternative to thermal regeneration or land filling at the end of useful adsorbent life. Continuous adsorption-electrochemical regeneration encompasses the adsorption and regeneration steps, typically separated in the bulk of industrial processes due to long adsorption equilibrium times (ranging from hours to months), into one continuous system. This is possible using a non-porous, electrically conducting carbon derivative called Nyex. The non-porosity of Nyex allows it to achieve its full adsorptive capacity within a few minutes and its electrical conductivity allows it to form part of the electrode in an electrochemical cell. As a result of its properties Nyex can undergo quick adsorption and fast electrochemical regeneration in a combined adsorption-electrochemical regeneration cell achieving 100% regeneration efficiency. | 7 | Physical Chemistry |
Amylase also has medical applications in the use of pancreatic enzyme replacement therapy (PERT). It is one of the components in Sollpura (liprotamase) to help in the breakdown of saccharides into simple sugars. | 1 | Biochemistry |
Organic matter that is deposited in marine sediments contains a key indicator as to its source and the processes it underwent before reaching the floor as well as after deposition, its carbon to nitrogen ratio. In the global oceans, freshly produced algae in the surface ocean typically have a carbon to nitrogen ratio of about 4 to 10. However, it has been observed that only 10% of this organic matter (algae) produced in the surface ocean sinks to the deep ocean without being degraded by bacteria in transit, and only about 1% is permanently buried in the sediment. An important process called sediment diagenesis accounts for the other 9% of organic carbon that sank to the deep ocean floor, but was not permanently buried, that is 9% of the total organic carbon produced is degraded in the deep ocean. The microbial communities utilizing the sinking organic carbon as an energy source, are partial to nitrogen-rich compounds because much of these bacterium are nitrogen-limited and much prefer it over carbon. As a result, the carbon to nitrogen ratio of sinking organic carbon in the deep ocean is elevated compared to fresh surface ocean organic matter that had not been degraded. An exponential increase in C/N ratios is observed with increasing water depth—with C/N ratios reaching 10 at intermediate water depths of about 1000 meters, and up to 15 in the deep ocean (deeper than about 2500 meters) . This elevated C/N signature is preserved in the sediment, until another form of diagenesis, post-depositional diagenesis, alters its C/N signature once again. Post-depositional diagenesis occurs in organic-carbon-poor marine sediments where bacteria are able to oxidize organic matter in aerobic conditions as an energy source. The oxidation reaction proceeds as follows: CHO + HO → CO + 4H + 4e, with a standard free energy of –27.4 kJ mol (half reaction). Once all of the oxygen is used up, bacteria are able to carry out an anoxic sequence of chemical reactions as an energy source, all with negative ∆G°r values, with the reaction becoming less favorable as the chain of reactions proceeds.
The same principle described above explaining the preferential degradation of nitrogen-rich organic matter occurs within the sediments, as they are more labile and are in higher demand. This principle has been utilized in paleoceanographic studies in order to identify core sites that have not experienced much microbial activity, or contamination by terrestrial sources with much higher C/N ratios.
Lastly, ammonia, the product of the second reduction reaction, which reduces nitrate and produces nitrogen gas and ammonia, is easily adsorbed on clay mineral surfaces and protected from bacteria. This has been proposed as an explanation for lower than expected C/N signatures of organic carbon in sediments that have undergone post-depositional diagenesis.
Ammonium produced from the remineralisation of organic material, exists in elevated concentrations (1 - >14μM) within cohesive shelf sea sediments found in the Celtic Sea (depth: 1–30 cm). The depth of sediment exceeds 1m and would be a suitable study site to carry out paleolimnology experiments with C:N. | 9 | Geochemistry |
Phosgene oxime, or CX, is an organic compound with the formula . It is a potent chemical weapon, specifically a nettle agent, which is a type of blister agent. The compound itself is a colorless solid, but impure samples are often yellowish liquids. It has a strong, disagreeable and irritating odor. It is used as a reagent in organic chemistry. | 1 | Biochemistry |
In general, children, the elderly, and immunocompromised individuals require a lower dose of a pathogenic organism in order to contract an infection. Presently there are very few studies which are able to quantify the amount of time people are likely to spend in recreational waters and how much water they are likely to ingest. In general, children swim more often, stay in the water longer, submerge their heads more often, and swallow more water. This makes people more fearful of water in the sea as more bacteria will be growing on and around them. | 3 | Analytical Chemistry |
The self-information, also known as the information content of a signal, random variable, or event is defined as the negative logarithm of the probability of the given outcome occurring.
When applied to a discrete random variable, the self-information can be represented as
is the relative entropy of the probability distribution from a Kronecker delta representing certainty that — i.e. the number of extra bits that must be transmitted to identify if only the probability distribution is available to the receiver, not the fact that . | 7 | Physical Chemistry |
Peter Trefonas is a son of Louis Marco Trefonas, also a chemist, and Gail Thames. He was inspired by Star Trek and the writings of Isaac Asimov, and created his own chemistry lab at home.
Trefonas attended the University of New Orleans, receiving his Bachelor of Science in chemistry in 1980.
While an undergraduate, Trefonas earned money by writing video games for early personal computers. These included Worm, a clone of the 1976 arcade video game Blockade, and a clone of the arcade game Hustle (1977), which itself was based on Blockcade. Worm was the first of what would become many games in the snake video game genre for home computers. Trefonas also wrote a game based on Dungeons & Dragons.
Trefonas studied at the University of Wisconsin-Madison with Robert West, completing a Ph.D. in inorganic chemistry in late 1984. Trefonas became interested in electronic materials after working with West and chip makers from IBM to create organosilicon bilayer photoresists. His thesis topic was "Synthesis, properties and chemistry of organosilane and organogermane high polymers" (1985). | 5 | Photochemistry |
The term restriction enzyme originated from the studies of phage λ, a virus that infects bacteria, and the phenomenon of host-controlled restriction and modification of such bacterial phage or bacteriophage. The phenomenon was first identified in work done in the laboratories of Salvador Luria, Jean Weigle and Giuseppe Bertani in the early 1950s. It was found that, for a bacteriophage λ that can grow well in one strain of Escherichia coli, for example E. coli C, when grown in another strain, for example E. coli K, its yields can drop significantly, by as much as 3-5 orders of magnitude. The host cell, in this example E. coli K, is known as the restricting host and appears to have the ability to reduce the biological activity of the phage λ. If a phage becomes established in one strain, the ability of that phage to grow also becomes restricted in other strains. In the 1960s, it was shown in work done in the laboratories of Werner Arber and Matthew Meselson that the restriction is caused by an enzymatic cleavage of the phage DNA, and the enzyme involved was therefore termed a restriction enzyme.
The restriction enzymes studied by Arber and Meselson were type I restriction enzymes, which cleave DNA randomly away from the recognition site. In 1970, Hamilton O. Smith, Thomas Kelly and Kent Wilcox isolated and characterized the first type II restriction enzyme, HindII, from the bacterium Haemophilus influenzae. Restriction enzymes of this type are more useful for laboratory work as they cleave DNA at the site of their recognition sequence and are the most commonly used as a molecular biology tool. Later, Daniel Nathans and Kathleen Danna showed that cleavage of simian virus 40 (SV40) DNA by restriction enzymes yields specific fragments that can be separated using polyacrylamide gel electrophoresis, thus showing that restriction enzymes can also be used for mapping DNA. For their work in the discovery and characterization of restriction enzymes, the 1978 Nobel Prize for Physiology or Medicine was awarded to Werner Arber, Daniel Nathans, and Hamilton O. Smith. The discovery of restriction enzymes allows DNA to be manipulated, leading to the development of recombinant DNA technology that has many applications, for example, allowing the large scale production of proteins such as human insulin used by diabetic patients. | 1 | Biochemistry |
The AFM was invented by IBM scientists in 1985. The precursor to the AFM, the scanning tunneling microscope (STM), was developed by Gerd Binnig and Heinrich Rohrer in the early 1980s at IBM Research – Zurich, a development that earned them the 1986 Nobel Prize for Physics. Binnig invented the atomic force microscope and the first experimental implementation was made by Binnig, Quate and Gerber in 1986.
The first commercially available atomic force microscope was introduced in 1989. The AFM is one of the foremost tools for imaging, measuring, and manipulating matter at the nanoscale. | 6 | Supramolecular Chemistry |
Sperm DNA fragmentation appears to be an important factor in the cause of male infertility, since men with high DNA fragmentation levels have significantly lower odds of conceiving. Oxidative stress is the major cause of DNA fragmentation in spermatozoa. A high level of the oxidative DNA damage 8-oxo-2'-deoxyguanosine is associated with abnormal spermatozoa and male infertility. | 1 | Biochemistry |
Signal transducing histidine kinases are the key elements in two-component signal transduction systems. Examples of histidine kinases are EnvZ, which plays a central role in osmoregulation, and CheA, which plays a central role in the chemotaxis system. Histidine kinases usually have an N-terminal ligand-binding domain and a C-terminal kinase domain, but other domains may also be present. The kinase domain is responsible for the autophosphorylation of the histidine with ATP, the phosphotransfer from the kinase to an aspartate of the response regulator, and (with bifunctional enzymes) the phosphotransfer from aspartyl phosphate to water. The kinase core has a unique fold, distinct from that of the Ser/Thr/Tyr kinase superfamily.
HKs can be roughly divided into two classes: orthodox and hybrid kinases. Most orthodox HKs, typified by the E. coli EnvZ protein, function as periplasmic membrane receptors and have a signal peptide and transmembrane segment(s) that separate the protein into a periplasmic N-terminal sensing domain and a highly conserved cytoplasmic C-terminal kinase core. Members of this family, however, have an integral membrane sensor domain. Not all orthodox kinases are membrane bound, e.g., the nitrogen regulatory kinase NtrB (GlnL) is a soluble cytoplasmic HK. Hybrid kinases contain multiple phosphodonor and phosphoacceptor sites and use multi-step phospho-relay schemes instead of promoting a single phosphoryl transfer. In addition to the sensor domain and kinase core, they contain a CheY-like receiver domain and a His-containing phosphotransfer (HPt) domain. | 1 | Biochemistry |
While there are many methods of detecting fake precious metals, there are realistically only two options available for verifying the marked fineness of metal as being reasonably accurate: assaying the metal (which requires destroying it), or using X-ray fluorescence (XRF). XRF will measure only the outermost portion of the piece of metal and so may get misled by thick plating.
That becomes a concern because it would be possible for an unscrupulous refiner to produce precious metals bars that are slightly less pure than marked on the bar. A refiner doing $1 billion of business each year that marked .980 pure bars as .999 fine would make about an extra $20 million in profit. In the United States, the actual purity of gold articles must be no more than .003 less than the marked purity (e.g. .996 fine for gold marked .999 fine), and the actual purity of silver articles must be no more than .004 less than the marked purity. | 8 | Metallurgy |
Biotribocorrosion covers the science of surface transformations resulting from the interactions of mechanical loading and chemical/electrochemical reactions that occur between elements of a tribological system exposed to biological environments. It has been studied for artificial joint prostheses. It is important to understand material degradation processes for joint implants to achieve longer service life and better safety issues for such devices. | 8 | Metallurgy |
Aggregates that sink more quickly to the bottom of the ocean have a greater chance of exporting carbon to the deep sea floor. The longer the residence time in the water column the greater the chance of being grazed upon. Aggregates formed in high dust areas are able to increase their densities faster and in more superficial layers compared to aggregates formed without dust particles present and these aggregates with increased lithogenic material have also been correlated with particulate organic carbon fluxes, however when they become heavily ballasted with lithogenic material they cannot scavenge any additional minerals during their descent, which suggests that carbon export to the deep ocean in regions with high dust deposition is strongly controlled by dust input to the surface ocean while suspended dust particles in deeper water layers do not significantly interact with sinking aggregates. | 9 | Geochemistry |
Other common ylides include sulfonium ylides and sulfoxonium ylides; for instance, the Corey-Chaykovsky reagent used in the preparation of epoxides or in the Stevens rearrangement. | 0 | Organic Chemistry |
* Nano- and bio-organic materials: production, synthesis, structure and properties, diagnostic methods using X-ray and synchrotron radiation, electrons, neutrons and atomic force microscopy
* Fundamental aspects of the formation of crystalline materials and nanosystems, their real structure and properties
* Creation and study of new crystalline and functional materials | 3 | Analytical Chemistry |
The Zimmermann reagent is used as a simple spot-test used in chromatography to presumptively identify alkaloids, especially benzodiazepines, as well as other compounds. It is therefore used in drugs testing.
It is a two-component reagent, with the first component composed of 1,3-dinitrobenzene (1% w/v) in methanol and the second component composed of 15% potassium hydroxide in water.
One drop of each component is added to the sample being tested and the resulting colour change is observed to give an indication of the identity of the compound.
The reagent works by forming a reddish-purple Meisenheimer complex at C3 for diazepines with a carbonyl at C2 and an alkyl group at N1. Without these groups it is not possible to form the methylene compound which reacts with dinitrobenzene but triazolo compounds may react.
It is named for the American biochemist Robert Zimmermann (b.1937). | 3 | Analytical Chemistry |
The isolobal analogy can also be used with isoelectronic fragments having the same coordination number, which allows charged species to be considered. For example, Re(CO) is isolobal with CH and therefore, [Ru(CO)] and [Mo(CO)] are also isolobal with CH. Any 17-electron metal complex would be isolobal in this example.
In a similar sense, the addition or removal of electrons from two isolobal fragments results in two new isolobal fragments. Since Re(CO) is isolobal with CH, [Re(CO)] is isolobal with . | 0 | Organic Chemistry |
As DNA printing and DNA assembly methods have allowed commercial gene synthesis to become progressively and exponentially cheaper over the past years, artificial gene synthesis represents a powerful and flexible engineering tool for creating and designing new DNA sequences and protein functions. Besides synthetic biology, various research areas like those involving heterologous gene expression, vaccine development, gene therapy and molecular engineering, would benefit greatly from having fast and cheap methods to synthesise DNA to code for proteins and peptides. The methods used for DNA printing and assembly have even enabled the use of DNA as an information storage medium. | 1 | Biochemistry |
A (water-splitting) photoelectrolytic cell electrolizes water into hydrogen and oxygen gas by irradiating the anode with electromagnetic radiation, that is, with light. This has been referred to as artificial photosynthesis and has been suggested as a way of storing solar energy in hydrogen for use as fuel.
Incoming sunlight excites free electrons near the surface of the silicon electrode. These electrons flow through wires to the stainless steel electrode, where four of them react with four water molecules to form two molecules of hydrogen and 4 OH groups. The OH groups flow through the liquid electrolyte to the surface of the silicon electrode. There they react with the four holes associated with the four photoelectrons, the result being two water molecules and an oxygen molecule. Illuminated silicon immediately begins to corrode under contact with the electrolytes. The corrosion consumes material and disrupts the properties of the surfaces and interfaces within the cell.
Two types of photochemical systems operate via photocatalysis. One uses semiconductor surfaces as catalysts. In these devices the semiconductor surface absorbs solar energy and acts as an electrode for water splitting. The other methodology uses in-solution metal complexes as catalysts.
Photoelectrolytic cells have passed the 10 percent economic efficiency barrier. Corrosion of the semiconductors remains an issue, given their direct contact with water. Research is now ongoing to reach a service life of 10000 hours, a requirement established by the United States Department of Energy. | 5 | Photochemistry |
In a system of Euclidean spatial dimension that has an arbitrary number of components, the sum is made over all the constituents. and are respectively the fraction and the conductivity of each component, and is the effective conductivity of the medium. (The sum over the 's is unity.) | 7 | Physical Chemistry |
The following excerpt from Takashi Fujii (1960) summarises well the limits of the Vegard’s law in the context of mineralogy and also makes the link with the Gladstone–Dale equation: | 8 | Metallurgy |
CSPD ([3-(1-chloro-3-methoxyspiro[adamantane-4,4-dioxetane]-3'-yl)phenyl] dihydrogen phosphate) is a chemical substance with formula CHClOP. It is a component of enhanced chemiluminescence enzyme-linked immunosorbent assay (ELISA) kits, used for the detection of minute amounts of various substances such as proteins. | 1 | Biochemistry |
Vomiting agents are chemical weapon agents causing vomiting. Prolonged exposure can be lethal. They were used for the first time during WWI. | 1 | Biochemistry |
In photosynthesis, state transitions are rearrangements of the photosynthetic apparatus which occur on short time-scales (seconds to minutes). The effect is prominent in cyanobacteria, whereby the phycobilisome light-harvesting antenna complexes alter their preference for transfer of excitation energy between the two reaction centers, PS I and PS II. This shift helps to minimize photodamage caused by reactive oxygen species (ROS) under stressful conditions such as high light, but may also be used to offset imbalances between the rates of generating reductant and ATP.
The phenomenon was first discovered in unicellular green algae, and may also occur in plants. However, in these organisms it occurs by a different mechanism, which is not as well understood. The plant/algal mechanism is considered functionally analogous to the cyanobacterial mechanism but involves completely different components. The foremost difference is the presence of fundamentally different types of light-harvesting antenna complexes: plants and green algae use an intrinsically-bound membrane complex of chlorophyll a/b binding proteins for their antenna, instead of the soluble phycobilisome complexes used by cyanobacteria (and certain algae). | 1 | Biochemistry |
Bioinformatic analysis identified four methyltransferases within the cluster. Bioinformatics suggest that btmB, is an O-methyltransferase, while the other three, btmC, G and K, are radical S-adenosyl methionine (SAM) methyltransferases. The radical SAM methyltransferases are believed to β-methylate amino acid residues within the precursor peptide. btmC is believed to methylate phenylalanine, btmG is believed to methylate both valines, and btmK is believed to methylate proline based on gene deletion studies.
The three putative radical SAM methyltransferases encoded within the pathway are interesting for both mechanistic and biosynthetic reasons. Radical SAM methyltransferases are likely to methylate substrates by an unusual mechanism. Biosynthetically, β-methylations of amino acids are highly unusual in natural products. Polytheonamide B, a peptide natural product produced by a marine symbiont, is the only other structurally characterized example of direct β-methylation of a peptide natural product. The proposed methyl transfer from a SAM-utilizing enzyme was supported by earlier feeding studies with labeled methionine; labeled methionine is used because methionine is converted into SAM within cells. Even further, this study used stereospecifically labeled methionine ([methyl-(H-H)]-(2S, methyl-R)-methionine) to show that methylation occurred with a net retention of stereochemistry at the methyl group. The author speculated that net retention indicated a radical mechanism with a B12 intermediate. Radical transfer with a Cobalamin B12 cofactor and SAM has been shown with the few characterized radical SAM methyltransferases. Although the evidence points to radical β-methylation during bottromycin biosynthesis, it remains to be seen whether bioinformatic hypothesis and feeding studies will be supported by in vitro activity assays.
The Val3Ala substitution in bottromycin D does not change the β-methylation pattern between bottromycin A2 and D because Val3 is the only valine not methylated in bottromycin A2. As such, there are still three predicted radical SAM dependent enzymes in the bottromycin D biosynthetic cluster: bstC, bstF, and bstJ.
As of 2013, all published biosynthetic studies have been bioinformatic or cell-based. No biochemical assays directly demonstrating protein function have yet been published. It is likely that in vitro mechanistic studies to better elucidate the biosynthetic pathway will be forthcoming. | 0 | Organic Chemistry |
Mediator was originally discovered because it was important for RNA polymerase II function, but it has many more functions than just interactions at the transcription start site. | 1 | Biochemistry |
There are two types of target peptides directing to peroxisome, which are called peroxisomal targeting signals (PTS). One is PTS1, which is made of three amino acids on the C-terminus. The other is PTS2, which is made of a 9-amino-acid sequence often present on the N-terminus of the protein. | 1 | Biochemistry |
The gene for EH4, EPHX4, is projected to encode an epoxide hydrolase closely related in amino acid sequence and structure to mEH, sEH, and EH3. The activity and function of EH4 has not yet been defined. | 1 | Biochemistry |
In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product. The result of this is that the genes contained in the operon are either expressed together or not at all. Several genes must be co-transcribed to define an operon.
Originally, operons were thought to exist solely in prokaryotes (which includes organelles like plastids that are derived from bacteria), but their discovery in eukaryotes was shown in the early 1990s, and are considered to be rare. In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNAs.
Operons are also found in viruses such as bacteriophages. For example, T7 phages have two operons. The first operon codes for various products, including a special T7 RNA polymerase which can bind to and transcribe the second operon. The second operon includes a lysis gene meant to cause the host cell to burst. | 1 | Biochemistry |
While univesicular release is still believed to make up a substantial portion of transmitter release events, large fluctuations in postsynaptic cell current measurements and high transmitter concentration in some synapses have led to the hypothesis that multiple vesicles can be released per active zone with each action potential. Since vesicular release happens on the scale of microseconds, it has been difficult to capture direct electron microscopic evidence of this phenomenon. There is however considerable functional data that supports MVR throughout much of the brain and sensory neuron synapses. | 1 | Biochemistry |
PABPII, or polyadenine binding protein II, is a protein involved in the assembly of the polyadenine tail added to newly synthesized pre-messenger RNA (mRNA) molecules during the process of gene transcription. It is a regulatory protein that controls the rate at which polyadenine polymerase (PAP) adds adenine nucleotides to the 3' end of the growing tail within the nucleus of the cell. In the absence of PABPII, PAP adds adenines slowly, typically about 12. PABPII then binds to the short polyadenine tail and induces an acceleration in the rate of addition by PAP until the tail has grown to about 200 adenines long. The mechanism by which PABPII signals the termination of the polymerization reaction once the tail has reached its required length is not clearly understood.
PABPII is distinct from the related protein PABPI in being localized to the cell nucleus rather than the cytoplasm. | 1 | Biochemistry |
Chloromethane and bromomethane are used to introduce methyl groups in organic synthesis. Chlorodifluoromethane is the main precursor of tetrafluoroethylene, which is the monomeric precursor to Teflon. | 2 | Environmental Chemistry |
Within a homogeneous media such as a solution, there is no scatter. For this case, the function is linear with both the concentration of the absorbing species and the path-length. Additionally, the contributions of individual absorbing species are additive. For samples which scatter light, absorbance is defined as "the negative logarithm of one minus absorptance (absorption fraction: ) as measured on a uniform sample". For decadic absorbance, this may be symbolized as: . Even though this absorbance function is useful with scattering samples, the function does not have the same desirable characteristics as it does for non-scattering samples. There is, however, a property called absorbing power which may be estimated for these samples. The absorbing power of a single unit thickness of material making up a scattering sample is the same as the absorbance of the same thickness of the materiel in the absence of scatter. | 7 | Physical Chemistry |
IEC/RP MMC combines the advantages of RPLC and IEC. For example, WAX/RP has increased separation power and degree of freedom in adjusting the separation selectivity when compared with single WAX or RPLC. | 3 | Analytical Chemistry |
There is significant correlation of phosphorylated mTOR with the survival rate for patients with stages I and II TNBC. A patient-derived xenograft TNBC model testing the mTOR inhibitor rapamycin showed 77–99% tumor-growth inhibition, which is significantly more than has been seen with doxorubicin; protein phosphorylation studies indicated that constitutive activation of the mTOR pathway decreased with treatment. | 1 | Biochemistry |
Biological probe or bio-probes are used to collect samples for microbiological analysis. Microorganisms can accelerate the corrosion process, so monitoring the corrosion caused by them is effective in timely notification and preventive measures. | 8 | Metallurgy |
The photosynthesis process in chloroplasts begins when an electron of P680 of PSII attains a higher-energy level. This energy is used to reduce a chain of electron acceptors that have subsequently higher redox potentials. This chain of electron acceptors is known as an electron transport chain. When this chain reaches PSI, an electron is again excited, creating a high redox-potential. The electron transport chain of photosynthesis is often put in a diagram called the Z-scheme, because the redox diagram from P680 to P700 resembles the letter Z.
The final product of PSII is plastoquinol, a mobile electron carrier in the membrane. Plastoquinol transfers the electron from PSII to the proton pump, cytochrome b6f. The ultimate electron donor of PSII is water. Cytochrome bf transfers the electron chain to PSI through plastocyanin molecules. PSI can continue the electron transfer in two different ways. It can transfer the electrons either to plastoquinol again, creating a cyclic electron flow, or to an enzyme called FNR (Ferredoxin—NADP(+) reductase), creating a non-cyclic electron flow. PSI releases FNR into the stroma, where it reduces to NADPH.
Activities of the electron transport chain, especially from cytochrome bf, lead to pumping of protons from the stroma to the lumen. The resulting transmembrane proton gradient is used to make ATP via ATP synthase.
The overall process of the photosynthetic electron transport chain in chloroplasts is: | 5 | Photochemistry |
The Couette flow orientation system is the most widely used method of sample orientation for UV LD. It has a number of characteristics which make it highly suitable as a method of sample alignment. Couette flow is currently the only established means of orientating molecules in the solution phase. This method also requires only very small amounts of analysis sample ( 20 - 40 µl) in order to generate an LD spectrum. The constant recirculation of sample is another useful property of the system, allowing many repeat measurements to be taken of each sample, decreasing the effect of noise on the final recorded spectrum.
Its mode of operation is very simple, with the sample sandwiched between a spinning tube and a stationary rod. As the sample is spun inside the cell, the light beam is shone through the sample, the parallel absorbance calculated from horizontally polarised light, the perpendicular absorbance from the vertically polarised light.
Couette flow UV LD is currently the only commercially available means of LD orientation. | 7 | Physical Chemistry |
Since Ca is a common second messenger, GCaMP has been used to monitor the activation of signaling pathways. For instance, Bonder and McCarthy (2014) used GCaMP to show that astrocytic G-protein coupled receptor (GPCR) signaling and subsequent Ca release was not responsible for neurovascular coupling, the process by which changes in neuronal activity lead to changes in local blood flow. Similarly, Greer and Bear et al. (2016) used GCaMP to characterize the dynamics of Ca influx in necklace olfactory neuron signaling, which uses transmembrane MS4A proteins as chemoreceptors. | 1 | Biochemistry |
Both singlet oxygen states have no unpaired electrons and therefore no net electron spin. The Δ is however paramagnetic as shown by the observation of an electron paramagnetic resonance (EPR) spectrum. The paramagnetism of the Δ state is due to a net orbital (and not spin) electronic angular momentum. In a magnetic field the degeneracy of the levels is split into two levels with z projections of angular momenta +1ħ and −1ħ around the molecular axis. The magnetic transition between these levels gives rise to the EPR transition. | 7 | Physical Chemistry |
*Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, .
*Beattie, J.A., Oppenheim, I. (1979). Principles of Thermodynamics, Elsevier, Amsterdam, .
*Born, M. (1921). Kritische Betrachtungen zur traditionellen Darstellung der Thermodynamik, Physik. Zeitschr. 22: 218–224.
*Bryan, G.H. (1907). Thermodynamics. An Introductory Treatise dealing mainly with First Principles and their Direct Applications, B.G. Teubner, Leipzig.
*Buchdahl, H.A. (1957/1966). The Concepts of Classical Thermodynamics, Cambridge University Press, London.
* A translation may be found [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/caratheodory_-_thermodynamics.pdf here]. A partly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA.
*Haase, R. (1971). Survey of Fundamental Laws, chapter 1 of Thermodynamics, pages 1–97 of volume 1, ed. W. Jost, of Physical Chemistry. An Advanced Treatise, ed. H. Eyring, D. Henderson, W. Jost, Academic Press, New York, lcn 73–117081.
*Kirkwood, J.G., Oppenheim, I. (1961). Chemical Thermodynamics, McGraw–Hill, New York.
*Planck. M. (1914). [https://archive.org/details/theoryofheatradi00planrich The Theory of Heat Radiation], a translation by Masius, M. of the second German edition, P. Blakiston's Son & Co., Philadelphia. | 7 | Physical Chemistry |
Harris was elected a member of the National Academy of Sciences in 2002. Besides, he is also a member the American Association for the Advancement of Science, the American Academy of Arts and Sciences, the American Physical Society, and the Optical Society of America. | 7 | Physical Chemistry |
Similarity between enzymatic reactions ([http://www.chem.qmul.ac.uk/iubmb/enzyme/ EC]) can be calculated by using bond changes, reaction centres or substructure metrics ([http://www.ebi.ac.uk/thornton-srv/software/rbl/ EC-BLAST] ). | 1 | Biochemistry |
The reagent is prepared from trimethylsilyl chloride and bromotrifluoromethane in the presence of a phosphorus(III) reagent that serves as a halogen acceptor. | 0 | Organic Chemistry |
The dimer, digold hexabromide, has structural properties similar to those of the other gold trihalide dimeric compounds, such as gold(III) chloride. The gold centers exhibit square planar coordination with bond angles of roughly 90 degrees.
Calculations indicate that in the hypothetical monomeric forms of the gold trihalides, the Jahn-Teller effect causes differences to arise in the structures of the gold halide complexes. For instance, gold(III) bromide contains one long and two short gold-bromine bonds whereas gold(III) chloride and gold(III) fluoride consist of two long and one short gold-halogen bonds. Moreover, gold tribromide does not exhibit the same coordination around the central gold atom as gold trichloride or gold trifluoride. In the latter complexes, the coordination exhibits a T-conformation, but in gold tribromide the coordination exists as more of a dynamic balance between a Y-conformation and a T-conformation. This coordination difference can be attributed to the Jahn-Teller effect but more so to the decrease in π-back bonding of the gold atoms with the bromine ligands compared to the π-back bonding found with fluorine and chlorine ligands. It is also this decrease in π-back bonding which explains why gold tribromide is less stable than its trifluoride and trichloride counterparts. | 3 | Analytical Chemistry |
Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connections that allow cells to connect to one another to form tissues. Glycolipids are found on the surface of all eukaryotic cell membranes, where they extend from the phospholipid bilayer into the extracellular environment. | 0 | Organic Chemistry |
Schisandrins (schizandrins) are a group of bioactive chemical compounds found in Schisandra rubriflora, Schisandra sphenanthera, and Schisandra chinensis. Schizandrin is a tannin. | 0 | Organic Chemistry |
Compounds derived from various transition metal carbonyl complexes are organometallic representatives with somewhat unusual cyclic structure and electronics. Such a representative is given in the form of the paramagnetic, ten-electron, tetrahedral [CpCo][Bi{Co(CO)}] complex.
Additionally, clusters like closo-[BiCr(CO)] and [BiMo(CO)] have been reported to stabilize the ozone-like structure of [Bi]. The [Bi] species, isostructural and isoelectronic with ozone, can be analyzed independently as a moiety bound to the metal carbonyl complexes. The reported Bi-Bi distance falls in between the single and double bond region and is elongated compared to Bi=Bi bond in the [Bi] cluster, the later displaying a bond order of 1.25. This experimental observation is being rationalized by some amount of π-donation to the metal carbonyl center and simultaneously π* back-bonding to the bismuth cluster from the metallocene complex.
In 2009, Pearl et al. described the synthesis and isomerization of heterometallic complexes containing bismuth and rhenium. The precursors used in synthesis were an alkene-coordinated carbonyl rhenium complex and BiPh. The reaction yields two types of heteronuclear bismuth-rhenium complexes and a homodinuclear rhenium one as a side product. Upon heating, the hexametallic tribismuth-trirhenium heteronuclear complex undergoes isomerization to cis- and trans-clusters containing the bicyclo [3.3.0] core (see scheme below). Under subsequent irradiation both stereoisomers convert to a common spiro [4.3] cluster compound. | 0 | Organic Chemistry |
Panel edge staining is the by-product of the build-up of dirt and pollution. It is especially more noticeable on buildings using metallic façades in Asia, and regions close to the equator (such as Florida or South East Asia), as higher rates of air pollution, high levels of humidity and consistent rainfall encourage panel edge staining to develop.
The unique top-to-bottom stain pattern of panel edge staining is caused when the build-up of dirt and pollution is washed from the higher panels to the lower panels of a surface by natural precipitation. | 8 | Metallurgy |
The isotope-ratio mass spectrometer (IRMS) allows the precise measurement of mixtures of naturally occurring isotopes. Most instruments used for precise determination of isotope ratios are of the magnetic sector type. This type of analyzer is superior to the quadrupole type in this field of research for two reasons. First, it can be set up for multiple-collector analysis, and second, it gives high-quality peak shapes. Both of these considerations are important for isotope-ratio analysis at very high precision and accuracy.
The sector-type instrument designed by Alfred Nier was such an advance in mass spectrometer design that this type of instrument is often called the Nier type. In the most general terms the instrument operates by ionizing the sample of interest, accelerating it over a potential in the kilo-volt range, and separating the resulting stream of ions according to their mass-to-charge ratio (m/z). Beams with lighter ions bend at a smaller radius than beams with heavier ions. The current of each ion beam is then measured using a Faraday cup or multiplier detector.
Many radiogenic isotope measurements are made by ionization of a solid source, whereas stable isotope measurements of light elements (e.g. H, C, O) are usually made in an instrument with a gas source. In a "multicollector" instrument, the ion collector typically has an array of Faraday cups, which allows the simultaneous detection of multiple isotopes. | 9 | Geochemistry |
The dienone–phenol rearrangement is a reaction in organic chemistry first reported in 1921 by Karl von Auwers and Karl Ziegler. A common example of dienone–phenol rearrangement is 4,4-disubstituted converting into a stable 3,4-disubstituted phenol in presence of acid. A similar rearrangement is possible with a 2,2-disubstituted cyclohexadienone to its corresponding disubstituted phenol. Usually this type of rearrangement is spontaneous unless a dichloromethyl group is present at the 4th position or the process is otherwise blocked. | 0 | Organic Chemistry |
The expression vector is transformed or transfected into the host cell for protein synthesis. Some expression vectors may have elements for transformation or the insertion of DNA into the host chromosome, for example the vir genes for plant transformation, and integrase sites for chromosomal integration .
Some vectors may include targeting sequence that may target the expressed protein to a specific location such as the periplasmic space of bacteria. | 1 | Biochemistry |
The non-ribosomal peptide synthase (NRPS) is encoded by three genes: CepA, CepB, and CepC. CepA links the first three amino acids; CepB adds the fourth to sixth amino acids; CepC adds the last amino acid and includes a thioesterase domain to release the heptapeptide from the NRPS complex. The growing peptide chain is passed through modules for each amino acid. The basic organization of each module is A-PCP-C. The A, or adenylation, region activates the domain's amino acid to allow transfer to the PCP, or peptide carrying protein, region. The activated amino acid is transferred to a cysteine residue in the PCP region, which anchors the amino acid and prepares the amino acid to be added to the polypeptide. The C, or condensation, region attaches the amino acid to the polypeptide. In addition, modules 2, 4, and 5 have E regions that epimerize (switch the stereochemistry) of the added amino acid to produce the correct configuration. Module 7, the last module, has an X and TE region. The X region is responsible for recruiting several of the tailoring enzymes that will perform the necessary reactions (halogenation, glycosylation, methylation, oxidative cross-linking, and hydroxylations) to produce chloroeremomycin. Finally, the TE, or thioesterase, region releases chloroeremomycin from the NRPS complex. | 0 | Organic Chemistry |
Similarly to the resolving power of a diffraction grating, which is determined by the number of the illuminated grating elements and the order of diffraction, the resolving power of a VIPA is determined by the reflectivity of the back surface of the VIPA and the thickness of the glass plate. For a fixed thickness, a high reflectivity causes light to stay longer in the VIPA. This creates more virtual sources of light and thus increases the resolving power. On the other hand, with a lower reflectivity, the light in the VIPA is quickly lost, meaning fewer virtual sources of light are superimposed. This results in lower resolving power.
For large angular dispersion with high resolving power, the dimensions of the VIPA should be accurately controlled. Fine tuning of the VIPA characteristics was demonstrated by developing an elastomer-based structure (Metz, 2013).
A constant reflectivity of the partially transmissive mirror in the VIPA produces a Lorentzian power distribution when the output light is imaged onto a screen, which has a negative effect on the wavelength selectivity. This can be improved by providing the partially transmissive mirror with a linearly decreasing reflectivity. This leads to a Gaussian-like power distribution on a screen and improves the wavelength selectivity or the resolving power. | 7 | Physical Chemistry |
A group of distinguished scientists from the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) did a recent study on how laminin-111 interacts with the cytoplasmic protein, actin. Their study gave the following conclusions:
The biological process in which a cell ceases to continue growing and dividing is called quiescence (the opposite of cancer). ECM laminin-111 sends chemical signals that promotes adhesion of a cell and its ECM. Although the mechanism is unknown, these signals have also been linked to cell quiescence. Adding laminin-111 to breast epithelial cells leads to quiescence by altering nuclear actin. High levels of laminin-111 deplete nuclear actin which induces quiescence of cells. However, when an isoform of actin, that cannot exit a cell’s nucleus, is active, cells continue to grow and divide even when laminin levels are high. ECM laminin-111 levels in a normal breast cell are significantly higher than laminin-111 levels in tissues of cancerous breast tissue. Simply increasing laminin levels in the ECM of cancerous breast cells is not enough to lead to quiescence. Therefore, it is implied that there are multiple factors working together influencing cell-to-cell communication. How laminin-111 and nuclear actin communicate is one of these factors. Laminin-111 could be the physiological regulator of nuclear actin which would suggest that depleting nuclear actin could be a key to achieving cell quiescence and returning to homeostatic operating conditions. Decreased expression of laminin-111 and the growth-inhibitory signals that it produces in malignant myoepithelial cells begs for further investigation with regard to cancer research. Therefore, further exploration of laminin-111 and nuclear actin interaction could be a target for future experimental therapeutic investigations. | 0 | Organic Chemistry |
Widely known methods of structural investigation, such as mass-spectrometry and X-ray analysis are only limitedly applicable to carbohydrates. Such structural studies, such as sequence determination or identification of new monosaccharides, benefit the most from the NMR spectroscopy.
Absolute configuration and polymerization degree are not always determinable using NMR only, so the process of structural elucidation may require additional methods. Although monomeric composition can be solved by NMR, chromatographic and mass-spectroscopic methods provide this information sometimes easier. The other structural features listed above can be determined solely by the NMR spectroscopic methods.
The limitation of the NMR structural studies of carbohydrates is that structure elucidation can hardly be automatized and require a human expert to derive a structure from NMR spectra. | 0 | Organic Chemistry |
A "photoelectrochemical cell" is one of two distinct classes of device. The first produces electrical energy similarly to a dye-sensitized photovoltaic cell, which meets the standard definition of a photovoltaic cell. The second is a photoelectrolytic cell, that is, a device which uses light incident on a photosensitizer, semiconductor, or aqueous metal immersed in an electrolytic solution to directly cause a chemical reaction, for example to produce hydrogen via the electrolysis of water.
Both types of device are varieties of solar cell, in that a photoelectrochemical cell's function is to use the photoelectric effect (or, very similarly, the photovoltaic effect) to convert electromagnetic radiation (typically sunlight) either directly into electrical power, or into something which can itself be easily used to produce electrical power (hydrogen, for example, can be burned to create electrical power, see photohydrogen). | 5 | Photochemistry |
In polymer chemistry, branching is the regular or irregular attachment of side chains to a polymer's backbone chain. It occurs by the replacement of a substituent (e.g. a hydrogen atom) on a monomer subunit by another covalently-bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type. Branched polymers have more compact and symmetrical molecular conformations, and exhibit intra-heterogeneous dynamical behavior with respect to the unbranched polymers. In crosslinking rubber by vulcanization, short sulfur branches link polyisoprene chains (or a synthetic variant) into a multiple-branched thermosetting elastomer. Rubber can also be so completely vulcanized that it becomes a rigid solid, so hard it can be used as the bit in a smoking pipe. Polycarbonate chains can be crosslinked to form the hardest, most impact-resistant thermosetting plastic, used in safety glasses.
Branching may result from the formation of carbon-carbon or various other types of covalent bonds. Branching by ester and amide bonds is typically by a condensation reaction, producing one molecule of water (or HCl) for each bond formed.
Polymers which are branched but not crosslinked are generally thermoplastic. Branching sometimes occurs spontaneously during synthesis of polymers; e.g., by free-radical polymerization of ethylene to form polyethylene. In fact, preventing branching to produce linear polyethylene requires special methods. Because of the way polyamides are formed, nylon would seem to be limited to unbranched, straight chains. But "star" branched nylon can be produced by the condensation of dicarboxylic acids with polyamines having three or more amino groups. Branching also occurs naturally during enzymatically-catalyzed polymerization of glucose to form polysaccharides such as glycogen (animals), and amylopectin, a form of starch (plants). The unbranched form of starch is called amylose.
The ultimate in branching is a completely crosslinked network such as found in Bakelite, a phenol-formaldehyde thermoset resin. | 7 | Physical Chemistry |
The principle of the electron was first theorised in the period of 1838-1851 by a natural philosopher by the name of Richard Laming who speculated the existence of sub-atomic, unit charged particles; he also pictured the atom as being an electrosphere of concentric shells of electrical particles surrounding a material core.
It is generally accepted that J. J. Thomson first discovered the electron in 1897, although other notable members in the development in charged particle theory are George Johnstone Stoney (who coined the term "electron"), Emil Wiechert (who was first to publish his independent discovery of the electron), Walter Kaufmann, Pieter Zeeman and Hendrik Lorentz.
Compton scattering was first observed at Washington University in St. Louis in 1923 by Arthur Compton who earned the 1927 Nobel Prize in Physics for the discovery; his graduate student Y. H. Woo who further verified the results is also of mention. Compton scattering is usually cited in reference to the interaction involving the electrons of an atom, however nuclear Compton scattering does exist.
The first electron diffraction experiment was conducted in 1927 by Clinton Davisson and Lester Germer using what would come to be a prototype for modern LEED system. The experiment was able to demonstrate the wave-like properties of electrons, thus confirming the de Broglie hypothesis that matter particles have a wave-like nature. However, after this the interest in LEED diminished in favour of High-energy electron diffraction until the early 1960s when an interest in LEED was revived; of notable mention during this period is H. E. Farnsworth who continued to develop LEED techniques.
High energy electron-electron colliding beam history begins in 1956 when K. O'Neill of Princeton University became interested in high energy collisions, and introduced the idea of accelerator(s) injecting into storage ring(s). While the idea of beam-beam collisions had been around since approximately the 1920s, it was not until 1953 that a German patent for colliding beam apparatus was obtained by Rolf Widerøe. | 7 | Physical Chemistry |
It is useful to distinguish between global and local thermodynamic equilibrium. In thermodynamics, exchanges within a system and between the system and the outside are controlled by intensive parameters. As an example, temperature controls heat exchanges. Global thermodynamic equilibrium (GTE) means that those intensive parameters are homogeneous throughout the whole system, while local thermodynamic equilibrium (LTE) means that those intensive parameters are varying in space and time, but are varying so slowly that, for any point, one can assume thermodynamic equilibrium in some neighborhood about that point.
If the description of the system requires variations in the intensive parameters that are too large, the very assumptions upon which the definitions of these intensive parameters are based will break down, and the system will be in neither global nor local equilibrium. For example, it takes a certain number of collisions for a particle to equilibrate to its surroundings. If the average distance it has moved during these collisions removes it from the neighborhood it is equilibrating to, it will never equilibrate, and there will be no LTE. Temperature is, by definition, proportional to the average internal energy of an equilibrated neighborhood. Since there is no equilibrated neighborhood, the concept of temperature doesn't hold, and the temperature becomes undefined.
It is important to note that this local equilibrium may apply only to a certain subset of particles in the system. For example, LTE is usually applied only to massive particles. In a radiating gas, the photons being emitted and absorbed by the gas do not need to be in a thermodynamic equilibrium with each other or with the massive particles of the gas for LTE to exist. In some cases, it is not considered necessary for free electrons to be in equilibrium with the much more massive atoms or molecules for LTE to exist.
As an example, LTE will exist in a glass of water that contains a melting ice cube. The temperature inside the glass can be defined at any point, but it is colder near the ice cube than far away from it. If energies of the molecules located near a given point are observed, they will be distributed according to the Maxwell–Boltzmann distribution for a certain temperature. If the energies of the molecules located near another point are observed, they will be distributed according to the Maxwell–Boltzmann distribution for another temperature.
Local thermodynamic equilibrium does not require either local or global stationarity. In other words, each small locality need not have a constant temperature. However, it does require that each small locality change slowly enough to practically sustain its local Maxwell–Boltzmann distribution of molecular velocities. A global non-equilibrium state can be stably stationary only if it is maintained by exchanges between the system and the outside. For example, a globally-stable stationary state could be maintained inside the glass of water by continuously adding finely powdered ice into it to compensate for the melting, and continuously draining off the meltwater. Natural transport phenomena may lead a system from local to global thermodynamic equilibrium. Going back to our example, the diffusion of heat will lead our glass of water toward global thermodynamic equilibrium, a state in which the temperature of the glass is completely homogeneous. | 7 | Physical Chemistry |
The technology is designed primarily for government use, specifically on equipment such as tactical vehicles, ship surfaces, and weapons. The primary objective of CIDAS is the capability to detect trace levels of chemical warfare agents on surfaces before and after personnel decontaminate the surfaces "during Detailed Equipment Decontamination (DED) operations." One component of CIDAS is an applicator that is used to show chemical agents, specifically nerve and blister agents. | 1 | Biochemistry |
The first organoniobium compound fully characterized was , however the paramagnetic Nb(IV) metallocenes such as niobocene dichloride are more prevalent. Complexes are typically prepared by treatment of with NaCp to form the bis(cyclopentadienyl) complex followed by further functionalization. Derivatives of pentamethylcyclopentadiene are also known, such as .
Niobium carbonyls supported by Cp ligands can be prepared at various oxidation states of Nb and serve as useful precursors in niobium carbonyl chemistry. | 0 | Organic Chemistry |
The EPA National Exposure Research Laboratory can designate a measurement device using an established technological basis as a Federal Reference Method (FRM) to certify that the device has undergone a testing and analysis protocol, and can be used to monitor NAAQS compliance. Devices based on new technologies can be designated as a Federal Equivalent Method (FEM). FEMs are based on different sampling and/or analyzing technologies than FRMs, but are required to provide the same decision making quality when making NAAQS attainment determinations. Approved new methods are formally announced through publication in the Federal Register. A complete list of FRMs and FEMs is available. | 2 | Environmental Chemistry |
Primary Infrastructure
The primary infrastructure of RSN consists of seven primary nodes which were installed in 2012 by [http://www.l-3mps.com/maripro/index.aspx L-3 Maripro]. They are terminal points which help distribute power and bandwidth to the networks of deployed sensors.
Approximately 900 kilometers of cable (referred to as backbone cable) have been used to connect the primary nodes together. These cables make landfall at the shore station in Pacific, City, Oregon.
In 2005, over 175 scientists across the United States responded to a Request for Assistance from the National Science Foundation to develop a cabled observatory on the Juan de Fuca Plate. Nodes are located at pre-selected experimental sites throughout the Juan de Fuca plate. Axial Seamount, Hydrate Ridge on the Cascadia Margin and shallow water sites west of Newport, Oregon (the Endurance Array) all have primary nodes installed. The primary nodes are all located in environmentally benign areas.
Nodes also convert the 10kVdc voltage levels from the backbone cable to 375Vdc which is then directed to the secondary infrastructure. The 375V switching systems and Node telemetry systems were designed and manufactured by Texcel Technology Plc based in England. The software to manage the ports and telemetry protection systems was also supplied by Texcel as an element manager sitting under a Network Management System (NMS).
The primary nodes have a number of extra ports which offer the potential for large-scale future expansion (>100 kilometers).
Secondary Infrastructure
The converted 375Vdc voltage from the primary nodes is then directed at low-and medium-power nodes and junction boxes. The nodes and junction boxes (similar to power strips) offer direct power and communications to the instruments at the experimental sites. In concert, these parts make up the RSN secondary infrastructure.
Extension cables are used to link the primary nodes to the secondary infrastructure, providing power and communications.
Equipment is linked using wet-mate connectors. Different types of cable were installed depending on load requirements. Bandwidth from these cables ranges from 10 Gbit/s to 1 Gbit/s.
During the VISIONS ’13 expedition to continue construction of RSN, over 22,000 meters of extension cables were installed on the ocean floor. The cables all successfully went online.
Upon completion in 2014, over 100 cabled seafloor and water column instruments will be operational. These instruments will allow monitoring of biological, chemical, geological, and geophysical processes in the ocean. The secondary infrastructure will also include six mooring systems for water-column profilers.
Cables are frequently deployed all across the world in ocean basins and margins. They have considerably long lifetimes. The backbone cable was installed in the summer of 2011. The commercial cable-laying ship, [http://www.subcom.com/process/install-and-test/fleet.aspx TE SubCom Dependable], carried out this phase of the project.
Special environmental requirements were also taken into account. Certain cables are substantially well-armored, especially those deployed in volcanic areas, such as Axial Seamount. | 9 | Geochemistry |
The modifications try to account for the points mentioned in above section like surface roughness, inhomogeneity, and adsorbate–adsorbate interactions. | 7 | Physical Chemistry |
* Ammonium dichromate on heating yields nitrogen, water and chromium(III) oxide.
* Ammonium nitrate on strong heating yields dinitrogen oxide ("laughing gas") and water.
* Ammonium nitrite on heating yields nitrogen gas and water.
* Barium azide on heating yields barium metal and nitrogen gas.
* Sodium azide on heating at violently decomposes to nitrogen and metallic sodium.
* Sodium nitrate on heating yields sodium nitrite and oxygen gas.
* Organic compounds like tertiary amines on heating undergo Hofmann elimination and yield secondary amines and alkenes. | 7 | Physical Chemistry |
The L-A dsRNA virus of the yeast Saccharomyces cerevisiae has a single 4.6 kb genomic segment that encodes its major coat protein, Gag (76 kDa) and a Gag-Pol fusion protein (180 kDa) formed by a -1 ribosomal frameshift. L-A can support the replication and encapsidation in separate viral particles of any of several satellite dsRNAs, called M dsRNAs, each of which encodes a secreted protein toxin (the killer toxin) and immunity to that toxin. L-A and M are transmitted from cell to cell by the cytoplasmic mixing that occurs in the process of mating. Neither is naturally released from the cell or enters cells by other mechanisms, but the high frequency of yeast mating in nature results in the wide distribution of these viruses in natural isolates. Moreover, the structural and functional similarities with dsRNA viruses of mammals has made it useful to consider these entities as viruses. | 1 | Biochemistry |
Several sources have reported that Fraser-Reid was nominated in 1998 for a Nobel Prize in chemistry for his work on oligosaccharides and immune responses. This statement cannot be verified since the names of the nominees are never publicly announced, and neither are they told that they have been considered for the Prize. Nomination records are sealed for fifty years.
The Institute of Jamaica awarded Fraser-Reid the 2007 Musgrave Medal (Gold) for his work in chemistry, noting that during his career he co-authored over 330 peer-reviewed publications and supervised 85 post-doctoral fellows and 55 PhD students. | 0 | Organic Chemistry |
Following application of the patch to humans, an average of 25% to 30% of the selegiline content is delivered systemically over 24 hours. Transdermal dosing results in significantly higher exposure to selegiline and lower exposure to all metabolites when compared to oral dosing; this is due to the extensive first-pass metabolism of the pill form and low first-pass metabolism of the patch form. The site of application is not a significant factor in how the drug is distributed. In humans, selegiline does not accumulate in the skin, nor is it metabolized there. | 4 | Stereochemistry |
Besides the motor proteins above, there are many more types of proteins capable of generating forces and torque in the cell. Many of these molecular motors are ubiquitous in both prokaryotic and eukaryotic cells, although some, such as those involved with cytoskeletal elements or chromatin, are unique to eukaryotes. The motor protein prestin, expressed in mammalian cochlear outer hair cells, produces mechanical amplification in the cochlea. It is a direct voltage-to-force converter, which operates at the microsecond rate and possesses piezoelectric properties. | 6 | Supramolecular Chemistry |
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