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Ca ions are usually kept at nanomolar levels in the cytosol of plant cells, and act in a number of signal transduction pathways as second messengers. | 1 | Biochemistry |
* 24 August 2007: A large buildup of sea foam occurred on the coast of Yamba, northern New South Wales.
* January–February 2008: Sea foam occurrences at Caloundra and Point Cartwright on Queensland's Sunshine Coast attracted world-wide media attention.
* December 2011: The coast road at Cleveleys, Lancashire was swamped by meter-high drifts of sea foam.
* 2012: During live coverage of Hurricane Irene in Ocean City, Maryland, Tucker Barnes was covered in sea foam.
* 24–25 September 2012: Following storms and high winds, the beach front of the Footdee area of Aberdeen was engulfed with sea foam.
* 27–28 January 2013: The Sunshine Coast in Queensland, Australia had masses of foam wash up on land from ex-tropical cyclone Oswald.
* June 2016: Sea foam occurred across the East coast of Australia, whipped up by storms.
* 28 March 2017: Sea foam was generated by Cyclone Debbie at Sarina Beach in Queensland, Australia.
* 16 October 2017: Hurricane Ophelia covered Cleveleys, Lancashire with spume.
* January 2018: Storm Eleanor causes widespread foam to appear across coastal Europe.
* 11 October 2019: Subtropical storm Melissa brought sea foam to Nantasket Beach in Hull, Massachusetts.
* 21 January 2020: Storm Gloria floods Tossa de Mar, Spain, with thick sea foam on top of major flooding.
* 11 May 2020: Five surfers die in The Netherlands, presumably upon drowning after becoming disoriented in over 2 meters thick sea foam.
* 13 July 2020: The Cape Town storm, South Africa | 9 | Geochemistry |
There are four commonly used types of applications for nitinol:
; Free recovery
: Nitinol is deformed at a low temperature, remains deformed, and then is heated to recover its original shape through the shape memory effect.
; Constrained recovery
: Similar to free recovery, except that recovery is rigidly prevented and thus a stress is generated.
; Work production
: The alloy is allowed to recover, but to do so it must act against a force (thus doing work).
; Superelasticity
: Nitinol acts as a super spring through the superelastic effect.
Superelastic materials undergo stress-induced transformation and are commonly recognized for their "shape-memory" property. Due to its superelasticity, NiTi wires exhibit "elastocaloric" effect, which is stress-triggered heating/cooling. NiTi wires are currently under research as the most promising material for the technology. The process begins with tensile loading on the wire, which causes fluid (within the wire) to flow to HHEX (hot heat exchanger). Simultaneously, heat will be expelled, which can be used to heat the surrounding. In the reverse process, tensile unloading of the wire leads to fluid flowing to CHEX (cold heat exchanger), causing the NiTi wire to absorb heat from the surrounding. Therefore, the temperature of the surrounding can be decreased (cooled).
Elastocaloric devices are often compared with magnetocaloric devices as new methods of efficient heating/cooling. Elastocaloric device made with NiTi wires has an advantage over magnetocaloric device made with gadolinium due to its specific cooling power (at 2 Hz), which is 70X better (7 kWh/kg vs. 0.1 kWh/kg). However, elastocaloric device made with NiTi wires also have limitations, such as its short fatigue life and dependency on large tensile forces (energy consuming).
In 1989 a survey was conducted in the United States and Canada that involved seven organizations. The survey focused on predicting the future technology, market, and applications of SMAs. The companies predicted the following uses of nitinol in a decreasing order of importance: (1) Couplings, (2) Biomedical and medical, (3) Toys, demonstration, novelty items, (4) Actuators, (5) Heat Engines, (6) Sensors, (7) Cryogenically activated die and bubble memory sockets, and finally (8) lifting devices. | 8 | Metallurgy |
In the early 2000s, Zhao's group reported that visible light can accelerate the degradation of organic pollutants with aqueous
solutions of iron tetrasulfophthalocyanine ([Fe(PcS)]) and Hydrogen peroxide|. They also found out FeBR (Fe complex of 2,2′-bipyridine) is efficient in eliminating organic pollutants such as rhodamine B (RhB), malachite green (MG) and N, N-dimethylaniline (DMA). They did several control experiments, in the dark or under irradiation, with or without irradiation. They proposed that when light is introduced, excitation of [Fe(PcS)] can result in electron transfer from ligand(L) to Fe, then Fe can be reduced to Fe. The Fe-L complex can react with to produce HO, leading to the degradation of pollutants. | 2 | Environmental Chemistry |
Kendomycin is an anticancer macrolide first isolated from Streptomyces violaceoruber. It has potent activity as an endothelin receptor antagonist and anti-osteoporosis agent.
It also has strong cytotoxicity against various tumor cell lines. | 0 | Organic Chemistry |
Combining operando Raman, UV–Vis and ATR-IR is particularly useful for studying homogeneous catalysis in solution. Transition-metal complexes can perform catalytic oxidation reactions on organic molecules; however, much of the corresponding reaction pathways are still unclear. For example, an operando study of the oxidation of veratryl alcohol by salcomine catalyst at high pH determined that the initial oxidation of the two substrate molecules to aldehydes is followed by the reduction of molecular oxygen to water, and that the rate determining step is the detachment of the product. Understanding organometallic catalytic activity on organic molecules is incredibly valuable for the further development of material science and pharmaceuticals. | 7 | Physical Chemistry |
Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting. | 7 | Physical Chemistry |
This method tries to identify 4-bp long end motifs from each stands 5 end on bisulfite sequencing reads of plasma cfDNAs. Hierarchical clustering of the motifs is done to detect any under/overrepresentation of these motifs due to cancer existence. The method incorporates Support Vector Machines and Logistic Regression to predict cancer patients from healthy ones. The method is also applied to transplant patients with clustering and multidimensional scaling (MDS) analysis and shows applicability. The same analysis types also proved that this method applies to prenetal testing. This method is also informative for cell type origins. | 1 | Biochemistry |
Glycobiology is a monthly peer-reviewed scientific journal covering all aspects of the field of glycobiology and the official journal of the Society for Glycobiology. It is published by Oxford University Press. The journal was established in September 1990. It publishes primary research on the "biological functions of glycans, including glycoproteins, glycolipids, proteoglycans and free oligosaccharides, and on proteins that specifically interact with glycans." | 1 | Biochemistry |
The δSi value of sediment porewater may be affected by post-depositional (diagenetic) precipitation or dissolution of Si. It is important to understand the extent and isotopic fractionations of these processes, as they alter the δSi values of the originally deposited sediments, and determine the δSi preserved in the rock record. Generally, precipitation of Si prefers the light isotope (Si) and leads to Si-enriched dissolved Si in the hosting solution. The isotopic effect of Si dissolution in porewater is yet to be clear, as some studies report a preference for Si during dissolution, while other studies document that isotopic fractionation was not expressed during dissolution of sediments. | 9 | Geochemistry |
Pletz grouped the explosophores into eight distinct categories.
;I.
:These represent:
:* the nitro group, a nitrogen atom bound to two oxygen atoms as well as an organic molecule (e.g. TNT, RDX)
:* the nitrate ion, a nitrogen atom bound to three oxygen atoms, (e.g. nitroglycerin, ANFO)
:* the nitrite ion, a nitrogen atom bound to two oxygen atoms
:Most commercially used explosives include the nitrate ion or the nitro group.
;II.
:The azo and azide groups respectively, connected to organic/inorganic compounds (e.g. silver azide , lead azide , ammonium azide )
;III.
:The halogenated nitrogen group X:halogen (e.g. nitrogen triiodide and nitrogen trichloride )
;IV.
:The fulminate group (e.g. fulminic acid HONC and mercury fulminate )
;V.
:The chlorate and perchlorate groups respectively, connected to organics/inorganics (e.g. potassium chlorate , fluorine perchlorate )
;VI.
:The peroxide and ozonide groups respectively, connected to organics/inorganics (e.g. acetone peroxide, butanone peroxide)
;VII.
:The acetylide group with its metal derivatives (e.g. silver acetylide , copper acetylide )
;VIII. A metal atom connected by an unstable bond to the carbon of certain organic radicals
:This class contains for instance organic compounds of mercury, thallium, and lead.
;Other
:Other substances have been characterised as explosophores outside of the eight classes as defined by Pletz. | 0 | Organic Chemistry |
Annonins are a group of chemical compounds classified as acetogenins. They are found in the extracts of Annona seeds (A. squamosa and A. muricata). Annonin-based bioinsecticides are used to control Coleoptera (beetle) pests commonly found in stored organic cereal and beans in the country of Brazil. Other different types of annonin-based insecticides, derived from A. mucosa, fight off lepidopteran (moth) pests that infest cabbage leaves, also found in the tropical climates of Brazil. The benefit of using these bioinsecticides is their relatively low cost and no phytotoxicity. These annonin molecules act as overpowering inhibitors of complex I (NADH: ubiquinone oxidoreductase) in the electron-transport chain in the mitochondria of quarry pests. In cell membranes of these same pests, annonins also inhibit coenzyme NADH, causing these arthropods to die. | 1 | Biochemistry |
The Schikorr reaction formally describes the conversion of the iron(II) hydroxide (Fe(OH)) into iron(II,III) oxide (FeO). This transformation reaction was first studied by Gerhard Schikorr. The global reaction follows:
It is of special interest in the context of the serpentinization, the formation of hydrogen by the action of water on a common mineral. | 8 | Metallurgy |
Volatile phenolic compounds are found in plant resin where they may attract benefactors such as parasitoids or predators of the herbivores that attack the plant.
In the kelp species Alaria marginata, phenolics act as chemical defence against herbivores. In tropical Sargassum and Turbinaria species that are often preferentially consumed by herbivorous fishes and echinoids, there is a relatively low level of phenolics and tannins. Marine allelochemicals generally are present in greater quantity and diversity in tropical than in temperate regions. Marine algal phenolics have been reported as an apparent exception to this biogeographic trend. High phenolic concentrations occur in brown algae species (orders Dictyotales and Fucales) from both temperate and tropical regions, indicating that latitude alone is not a reasonable predictor of plant phenolic concentrations. | 0 | Organic Chemistry |
The scientific work of Leonidas Zervas had a global resonance and his contribution was recognised by multiple awards throughout his life. In 1960 he received an honorary doctorate from the University of Basel on the occasion of the university's 500th anniversary, upon recommendation of Hans Erlenmeyer and Nobel laureate Tadeusz Reichstein. In 1969 he was bestowed honorary membership of the American Society of Biological Chemists. In 1976 he was conferred the (1st class) by the Socialist Republic of Romania. In the same year Zervas was made Foreign Member of the USSR Academy of Sciences, an indication of the great respect for his work in the Eastern Block, too. The Max-Bergmann-Kreis company of German peptide chemists planned to present Zervas with the first Max Bergmann golden medal for peptide chemistry in 1980, but his sudden death necessitated a posthumous award ceremony.
In honour of Zervas, a commemorative bust has been unveiled in his birthtown Megalopolis in 1991 and the main conference hall of the National Hellenic Research Foundation is called the "Leonidas Zervas amphitheatre".
The European Peptide Society has established the Leonidas Zervas Award "in commemoration of his outstanding contributions to peptide science", awarded biennially since 1988. The award is given to the "scientist who has made the most outstanding contributions to the chemistry, biochemistry and/or biology of peptides in the five years preceding the date of selection". | 0 | Organic Chemistry |
Tools and weapons, chisels and axe-heads, spearheads or dagger-blades, are the only surviving artifacts of the Copper Age, and do not show artistic treatment. But some Early Minoan pottery forms are plainly copied from metal prototypes, cups and jugs of simple construction and rather elaborate design. The cups are conical and sometimes a stem-foot; there are oval jars with long tubular spouts, and beaked jugs with round shoulders set on conical bodies. Heads of rivets which tie the metal parts together are often reproduced as a decorative element in clay. The spouted jars and pierced type of axe-head indicate that metallurgical connections of Early Minoan Crete were partly Mesopotamian. | 8 | Metallurgy |
Museomics is the study of genomic data obtained from ancient DNA (aDNA) and historic DNA (hDNA) specimens in museum collections.
Early research in this area focused on short sequences of DNA from mitochondrial genes, but sequencing of whole genomes has become possible.
Next-generation sequencing (NGS) and high-throughput sequencing (HTS) methods can be applied to the analysis of genetic datasets extracted from collections materials. Such techniques have been described as a "third revolution in sequencing technology". Like radiocarbon dating, the techniques of museomics are a transformative technology. Results are revising and sometimes overturning previously accepted theories about a wide variety of topics such as the domestication of the horse.
Museum collections contain unique resources such as natural history specimens, which can be used for genome-scale examinations of species, their evolution, and their responses to environmental change. Ancient DNA provides a unique window into genetic change over time. It enables scientists to directly study evolutionary and ecological processes, comparing ancient and modern populations, identifying distinct populations, and revealing patterns of change such as extinctions and migrations. Research may be used to identify isolated populations and inform conservation priorities.
However, museum specimens can be poorly preserved and are subject to degradation and contamination. Genomic analyses face considerable challenges as a result of the highly degraded DNA typical of museum specimens. DNA from such samples is often subject to post-mortem nucleotide damage such as the hydrolytic deamination of cytosine (C) to uracil (U) residues. PCR amplification of damaged templates can further substitute uracils with thymine (T), completing a C to T substitution path. Such errors tend to occur towards the ends of molecules, accumulate with time, and can be significant in specimens a century-old or later. Robust genomic and statistical techniques are needed to rigorously detect and avoid errors and genotyping uncertainties when carrying out analyses based on museum collections. Optimal methods for working with hDNA and aDNA can differ as a result of differences in their DNA degradation history.
Museomics also involves destructive sampling, irreversibly removing parts of sometimes rare specimens to obtain DNA. This can be contentious for curators and collection staff, involving a variety of ethical issues around the handling and destruction of objects, colonial acquisition and repatriation practices, and present-day social and political implications of research. Museums, universities and journals are increasingly developing ethics statements, best practices and guidelines for such work. | 3 | Analytical Chemistry |
In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.
When two diastereoisomers differ from each other at only one stereocenter, they are epimers. Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two.
Diastereomers differ from enantiomers in that the latter are pairs of stereoisomers that differ in all stereocenters and are therefore mirror images of one another.
Enantiomers of a compound with more than one stereocenter are also diastereomers of the other stereoisomers of that compound that are not their mirror image (that is, excluding the opposing enantiomer).
Diastereomers have different physical properties (unlike most aspects of enantiomers) and often different chemical reactivity.
Diastereomers differ not only in physical properties but also in chemical reactivity — how a compound reacts with others. Glucose and galactose, for instance, are diastereomers. Even though they share the same molar weight, glucose is more stable than galactose. This difference in stability causes galactose to be absorbed slightly faster than glucose in human body.
Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction. In general, stereoselectivity is attributed to torsional and steric interactions in the stereocenter resulting from electrophiles approaching the stereocenter in reaction. | 4 | Stereochemistry |
Ashing is a test to deduce the amount of ash forming material present in a petroleum product so as to decide its use in certain applications. Ash-forming materials are considered to be undesirable impurities or contaminants.
In the ash analysis of petroleum products, ash content represents the incombustible component remaining after a sample of the furnace oil is completely burned. The ash content of petroleum products is generally low. It is defined as the inorganic residue that remains after combustion of the oil in air at specific high temperature. Ash typically ranges from 0.1 to 0.2% in oil. Some of the ash forming constituents occur naturally in crude oil; others are present as a result of refining or contamination during storage or distribution. Knowledge of the amount of ash-forming material present in a product can provide information as to whether or not the product is suitable application.
In the ash analysis of coal and other solid fuels, the amount of sulfur retained in the ash during the ashing process is not constant, but rather is dependent upon the conditions of ashing as well as the other inorganic constituents in the ash that may form sulfates during the ashing procedure. As such, different ashing procedures may yield different ash contents. | 3 | Analytical Chemistry |
Lipidology is the scientific study of lipids. Lipids are a group of biological macromolecules that have a multitude of functions in the body. Clinical studies on lipid metabolism in the body have led to developments in therapeutic lipidology for disorders such as cardiovascular disease. | 1 | Biochemistry |
Response regulator proteins typically consist of a receiver domain and one or more effector domains, although in some cases they possess only a receiver domain and exert their effects through protein-protein interactions. In two-component signaling, a histidine kinase responds to environmental changes by autophosphorylation on a histidine residue, following which the response regulator receiver domain catalyzes transfer of the phosphate group to its own recipient aspartate residue. This induces a conformational change that alters the function of the effector domains, usually resulting in increased transcription of target genes. The mechanisms by which this occurs are diverse and include allosteric activation of the effector domain or oligomerization of phosphorylated response regulators. In a common variation on this theme, called a phosphorelay, a hybrid histidine kinase possesses its own receiver domain, and a histidine phosphotransfer protein performs the final transfer to a response regulator.
In many cases, histidine kinases are bifunctional and also serve as phosphatases, catalyzing the removal of phosphate from response regulator aspartate residues, such that the signal transduced by the response regulator reflects the balance between kinase and phosphatase activity. Many response regulators are also capable of autodephosphorylation, which occurs on a wide range of time scales. In addition, phosphoaspartate is relatively chemically unstable and may be hydrolyzed non-enzymatically.
Histidine kinases are highly specific for their cognate response regulators; there is very little cross-talk between different two-component signaling systems in the same cell. | 1 | Biochemistry |
Schwabs research interests seem to have switched to kinetics under the guidance of Max Bodenstein while at Nernsts Institute of Physical Chemistry in Berlin. Some of the problems on which Schwab worked on his own in this period included the thermal decomposition of methane, chemical reactions taking place during a cold cathode discharge, and the speed of dissolution of gases.
In Würzburg, he continued along a similar line of work studying gas dissolution, the thermal decomposition of ammonia, and the kinetics of photochlorination reactions. | 7 | Physical Chemistry |
PECO has also shown promise as a means of air purification. For people with severe allergies, air purifiers are important to protect them from allergens within their own homes. However, some allergens are too small to be removed by normal purification methods. Air purifiers using PECO filters are able to remove particles as small as 0.1 nm.
These filters work as photons excite a photocatalyst, creating hydroxyl free radicals, which are extremely reactive and oxidize organic material and microorganisms that cause allergy symptoms, forming harmless products like carbon dioxide and water. Researchers testing this technology with patients suffering from allergies drew promising conclusions from their studies, observing significant reductions in total symptom scores (TSS) for both nasal (TNSS) and ocular (TOSS) allergies after just 4 weeks of using the PECO filter. This research demonstrates strong potential for impactful health improvements who suffer from severe allergies and asthma. | 5 | Photochemistry |
* Contrast in Ramsey fringes
** The coherence time is the time at which the contrast in Ramsey fringes drops to 1/e.
* Damping of Rabi oscillations
** The coherence time is the time at which the amplitude of the Rabi oscillation has dropped to 1/e. | 7 | Physical Chemistry |
Researchers at Sandia Labs, Ames National Laboratory and Iowa State University reported a 3D-printed superalloy composed of 42% aluminum, 25% titanium, 13% niobium, 8% zirconium, 8% molybdenum and 4% tantalum. Most alloys are made chiefly of one primary element, combined with low amounts of other elements. In contrast MPES have substantial amounts of three or more elements.
Such alloys promise improvements on high-temperature applications, strength-to-weight, fracture toughness, corrosion and radiation resistance, wear resistance, and others. They reported hardness and density of 1.8–2.6 GPa-cm/g, which surpasses all known alloys, including intermetallic compounds, titanium aluminides, refractory MPEAs, and conventional Ni-based superalloys. This represents a 300% improvement over Inconel 718 based on measured peak hardness of 4.5 GPa and density of 8.2 g/cm, (0.55 GPa-cm/g).
The material is stable at 800 °C, hotter than the 570+ °C found in typical coal-based power plants.
The researchers acknowledged that the 3D printing process produces microscopic cracks when forming large parts, and that the feedstock includes metals that limit applicability in cost-sensitive applications. | 8 | Metallurgy |
In vivo ultrasound mediated drug delivery was first reported in 1991 and many other preclinical studies involving sonoporation have followed. This method is being used to deliver therapeutic drugs or genes to treat a variety of diseases including: Stroke, Cancer, Parkinsons, Alzheimers... The preclinical utility of sonoporation is well illustrated through past tumor radiation treatments which have reported a more than 10-fold cellular destruction when ionizing radiation is coupled with ultrasound-mediated microbubble vascular disruption. This increase in delivery efficiency could allow for the appropriate reduction in therapeutic dosing. | 1 | Biochemistry |
The modern X-ray fluorescence (XRF) is also a non-destructive technique that is suitable for normal assaying requirements. It typically has an accuracy of 2 to 5 parts per thousand and is well-suited to relatively flat and large surfaces. It is a quick technique taking about three minutes, and the results can be automatically printed out by computer.
One process for X-ray fluorescence assay involves melting the material in a furnace and stirring to make a homogeneous mix. Following this, a sample is taken from the centre of the molten sample. Samples are typically taken using a vacuum pin tube. The sample is then tested by X-ray fluorescence spectroscopy. Metallurgical assay is typically completed in this way to ensure that an accurate assay is performed. | 8 | Metallurgy |
In analytical and organic chemistry, elution is the process of extracting one material from another by washing with a solvent: washing of loaded ion-exchange resins to remove captured ions, or eluting proteins or other biopolymers from a gel electrophoresis or chromatography column.
In a liquid chromatography experiment, for example, an analyte is generally adsorbed by ("bound to") an adsorbent in a liquid chromatography column. The adsorbent, a solid phase, called a "stationary phase", is a powder which is coated onto a solid support. Based on an adsorbent's composition, it can have varying affinities to "hold onto" other molecules—forming a thin film on the surface of its particles. Elution then is the process of removing analytes from the adsorbent by running a solvent, called an "eluent", past the adsorbent-analyte complex. As the solvent molecules "elute", or travel down through the chromatography column, they can either pass by the adsorbent-analyte complex or displace the analyte by binding to the adsorbent in its place. After the solvent molecules displace the analyte, the analyte can be carried out of the column for analysis. This is why as the mobile phase, called an "eluate", passes out of the column, it typically flows into a detector or is collected by a fraction collector for compositional analysis.
Predicting and controlling the order of elution is a key aspect of column chromatographic and column electrophoretic methods. | 3 | Analytical Chemistry |
In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne () is added to a carbonyl group () to form an α-alkynyl alcohol ().
When the acetylide is formed from acetylene (), the reaction gives an α-ethynyl alcohol. This process is often referred to as ethynylation. Such processes often involve metal acetylide intermediates. | 0 | Organic Chemistry |
Basically there are five types of discharge that are used for the rotary vacuum drum filter such as belt, scraper, roll, string and pre coat discharge. | 3 | Analytical Chemistry |
The shape of the zero-phonon line is Lorentzian with a width determined by the excited state lifetime T according to the Heisenberg uncertainty principle. Without the influence of the lattice, the natural line width (full width at half maximum) of the chromophore is γ = 1/T . The lattice reduces the lifetime of the excited state by introducing radiationless decay mechanisms. At absolute zero the lifetime of the excited state influenced by the lattice is T. Above absolute zero, thermal motions will introduce random perturbations to the chromophores local environment. These perturbations shift the energy of the electronic transition, introducing a temperature dependent broadening of the line width. The measured width of a single chromophores zero phonon line, the homogeneous line width, is then γ(T) ≥ 1/T' .
The line shape of the phonon side band is that of a Poisson distribution as it expresses a discrete number of events, electronic transitions with phonons, during a period of time. At higher temperatures, or when the chromophore interacts strongly with the matrix, the probability of multiphonon is high and the phonon side band approximates a Gaussian distribution.
The distribution of intensity between the zero-phonon line and the phonon sideband is characterized by the Debye-Waller factor α. | 7 | Physical Chemistry |
Glycorandomization, is a drug discovery and drug development technology platform to enable the rapid diversification of bioactive small molecules, drug leads and/or approved drugs through the attachment of sugars. Initially developed as a facile method to manipulate carbohydrate substitutions of naturally occurring glycosides to afford the corresponding differentially glycosylated natural product libraries, glycorandomization applications have expanded to include both small molecules (drug leads and approved drugs) and even macromolecules (proteins). Also referred to as glycodiversification, glycorandomization has led to the discovery of new glycoside analogs which display improvements in potency, selectivity and/or ADMET as compared to the parent molecule. | 0 | Organic Chemistry |
The same process of photoemission can be used to produce electricity from any spectrum, although the number of semiconductor materials that will have just the right bandgap for an arbitrary hot object is limited. Instead, semiconductors that have tuneable bandgaps are needed. It is also difficult to produce solar-like thermal output; an oxyacetylene torch is about 3400 K (~3126 °C), and more common commercial heat sources like coal and natural gas burn at much lower temperatures around 900 °C to about 1300 °C. This further limits the suitable materials. In the case of TPV most research has focused on gallium antimonide (GaSb), although germanium (Ge) is also suitable.
Another problem with lower-temperature sources is that their energy is more spread out, according to Wien's displacement law. While one can make a practical solar cell with a single bandgap tuned to the peak of the spectrum and just ignore the losses in the IR region, doing the same with a lower temperature source will lose much more of the potential energy and result in very low overall efficiency. This means TPV systems almost always use multi-junction cells in order to reach reasonable double-digit efficiencies. Current research in the area aims at increasing system efficiencies while keeping the system cost low, but even then their roles tend to be niches similar to those of multi-junction solar cells. | 7 | Physical Chemistry |
The suffix -one is used in organic chemistry to form names of organic compounds containing the -C(=O)- group: see ketone. Sometimes a number between hyphens is inserted before it to state which atom the =O atom is attached to. This suffix was extracted from the word acetone. The final "-e" disappears if it is followed by another suffix that starts with a vowel. | 0 | Organic Chemistry |
The Danheiser benzannulation is a regiocontrolled phenol annulation. This annulation provides an efficient route to form an aromatic ring in one step. It is a thermal combination of a substituted cyclobutenones with heterosubstituted acetylenes to produce highly substituted aromatic compounds, specifically phenols or resorcinols (Scheme 1). This benzannulation reaction creates previously unaccessed aromatic substitution patterns. A variety of substituted aromatic rings can be prepared using this method including: phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles.
The modified Danheiser benzannulation allows the synthesis of polycyclic aromatic and heteroaromatic systems. This also includes napthalenes, benzofurans and indoles. This second generation aromatic annulation is achieved by irradiation of a solution of acetylene and a vinyl or aryl α-diazo ketone in dichloroethane. This reaction utilizes the photochemical Wolff rearrangement of a diazoketone to generate an aryl or vinylketene. These ketene intermediates cannot be isolated due to their high reactivity to form diketenes. These rearrangements are performed in the presence of unsaturated compounds which undergo [2+2] cycloadditions with the in situ generated ketenes. When ketenes are formed in the presence of alkynes they proceed through pericyclic reactions to generate a substituted aromatic ring (Scheme 2). Avoiding the use of the high energy cyclobutenone starting materials provides access to a wider variety of substituted aromatic compounds.
This reaction is quite complementary to the Wulff–Dötz reaction. This is a [2+1] cycloaddition of a carbene to an alkyne or alkene (more specifically in the Dӧtz reaction a carbene coordinated to a metal carbonyl group) to produce substituted aromatic phenols. | 0 | Organic Chemistry |
When a cluster of microparticles are trapped within a monochromatic laser beam, the organization of the microparticles within the optical trapping is heavily dependent on the redistributing of the optical trapping forces amongst the microparticles. This redistribution of light forces amongst the cluster of microparticles provides a new force equilibrium on the cluster as a whole. As such we can say that the cluster of microparticles are somewhat bound together by light. One of the first experimental evidence of optical binding was reported by Michael M. Burns, Jean-Marc Fournier, and Jene A. Golovchenko, though it was originally predicted by T. Thirunamachandran. One of the many recent studies on optical binding has shown that for a system of chiral nanoparticles, the magnitude of the binding forces are dependent on the polarisation of the laser beam and the handedness of interacting particles themselves, with potential applications in areas such as enantiomeric separation and optical nanomanipulation. | 1 | Biochemistry |
Cyclic AMP-dependent protein kinases (protein kinase A) are activated by the signal chain coming from the G protein (that was activated by the receptor) via adenylate cyclase and cyclic AMP (cAMP). In a feedback mechanism, these activated kinases phosphorylate the receptor. The longer the receptor remains active the more kinases are activated and the more receptors are phosphorylated. In β-adrenoceptors, this phosphorylation results in the switching of the coupling from the G class of G-protein to the G class. cAMP-dependent PKA mediated phosphorylation can cause heterologous desensitisation in receptors other than those activated. | 1 | Biochemistry |
The Qubit fluorometer is a laboratory instrument developed and distributed by Invitrogen, which is now a part of Thermo Fisher. It is used for the quantification of DNA, RNA, and protein. | 7 | Physical Chemistry |
Merrilactone A was found to exhibit a significant neurotrophic activity, such as greatly promoting neurite outgrowth in the primary cultures of fetal rat cortical neurons at concentrations from 10 to 0.1 μmol/L. It was also found that this compound had a property of neuroprotection at same concentration. | 0 | Organic Chemistry |
Online non-intrusive ultrasonic thickness sensors are a popular choice for corrosion monitoring in various industries, including oil and gas, chemical processing, and power generation. These sensors can provide accurate and reliable thickness measurements of metal structures without requiring physical access or disruption to the equipment. The sensors can be installed permanently and remotely connected to a monitoring system, allowing for continuous data collection and analysis. With the ability to detect corrosion early on, online ultrasonic thickness sensors can help prevent equipment failure, reduce downtime, and improve overall safety and efficiency. | 8 | Metallurgy |
* F. Geiss (1987): Fundamentals of thin layer chromatography planar chromatography, Heidelberg, Hüthig,
* Justus G. Kirchner (1978): Thin-layer chromatography, 2nd edition, Wiley
* Joseph Sherma, Bernard Fried (1991): Handbook of Thin-Layer Chromatography (= Chromatographic Science. Bd. 55). Marcel Dekker, New York NY, .
* Elke Hahn-Deinstorp: Applied Thin-Layer Chromatography. Best Practice and Avoidance of Mistakes. Wiley-VCH, Weinheim u. a. 2000, | 3 | Analytical Chemistry |
* Books (chronological order):
** Tanner, Brian: X-ray diffraction topography. Pergamon Press (1976)..
** Authier, André and Lagomarsino, Stefano and Tanner, Brian K. (editors): X-Ray and Neutron Dynamical Diffraction – Theory and Applications. Plenum Press / Kluwer Academic Publishers (1996). .
** Bowen, Keith and Tanner, Brian: High Resolution X-Ray Diffractometry and Topography. Taylor and Francis (1998). .
** Authier, André: Dynamical theory of X-ray diffraction. IUCr monographs on crystallography, no. 11. Oxford University Press (1st edition 2001/ 2nd edition 2003). .
* Reviews
** Lang, A. R.: Techniques and interpretation in X-ray topography. In: Diffraction and Imaging Techniques in Materials Science (edited by Amelinckx S., Gevers R. and Van Landuyt J.) 2nd ed. rev. (1978), pp 623–714. Amsterdam: North Holland.
** Klapper, Helmut: X-ray topography of organic crystals. In: Crystals: Growth, Properties and Applications, vol. 13 (1991), pp 109–162. Berlin-Heidelberg: Springer.
** Lang, A. R.: Topography. In: International Tables for Crystallography, Vol. C (1992), Section 2.7, p. 113. Kluwer, Dordrecht.
** Tuomi, T: Synchrotron X-ray topography of electronic materials. Journal of Synchrotron Radiation (2002) 9, 174-178.
** Baruchel, J. and Härtwig, J. and Pernot-Rejmánková, P.: Present state and perspectives of synchrotron radiation diffraction imaging. Journal of Synchrotron Radiation (2002) 9, 107-114.
* Selected original articles (chronological order):
** X-ray topography
*** T. Tuomi, K. Naukkarinen, E. Laurila, P. Rabe: Rapid high resolution X-ray topography with synchrotron radiation. Acta Polytechnica Scandinavica, Ph. Incl. Nucleonics Series No. 100, (1973), 1-8.
** Special applications:
** Instrumentation and beamlines for topography: | 3 | Analytical Chemistry |
Landes was an undergraduate student in chemistry at George Mason University. She moved to Georgia Tech for her doctoral research, where she majored in physical chemistry under the supervision of Mostafa El-Sayed. After earning her doctorate, Landes joined the University of Oregon as a postdoctoral researcher with Geraldine L. Richmond, where she spent one year before joining the University of Texas at Austin with Paul Barbara. | 7 | Physical Chemistry |
For double bonded molecules, Cahn–Ingold–Prelog priority rules (CIP rules) are followed to determine the priority of substituents of the double bond. If both of the high priority groups are on the same side of the double bond (cis configuration), then the stereoisomer is assigned the configuration Z (zusammen, German word meaning "together"). If the high priority groups are on opposite sides of the double bond ( trans configuration ), then the stereoisomer is assigned the configuration E (entgegen, German word meaning "opposed") | 4 | Stereochemistry |
In chemistry, a C–H···O interaction is occasionally described as a special type of weak hydrogen bond. These interactions frequently occur in the structures of important biomolecules like amino acids, proteins, sugars, DNA and RNA. | 0 | Organic Chemistry |
The zooplanktonic Calanus spp. are not only important for moving carbon out of the photic zone and into the deep ocean, but these lipid-rich organisms play a critical role in the success of many marine species that depend on them as food. They comprise the majority of diets for fishes, seabirds and even large mammals such as whales. Copepods can account for about 70–90% of total zooplankton biomass, depending on region. Additionally, their eggs are a main source of food for commercially important fish stocks. The copepod eggs are buoyant and will rise to the sea surface, but are susceptible to predation by fish and other organisms. Copepods also provide the benthic community with food via sinking fecal pellets, meaning that as fish and smaller invertebrates excrete waste, that waste falls to the sea floor and organisms on the sea floor compete for the pellets as food. The role of copepods in the food web is crucially intertwined amongst other organisms.
Copepod abundance, specifically the C. finmarchicus, has a direct impact on the endangered right whales of the North Atlantic. North Atlantic right whales rely on copepods as their primary prey in order to meet their nutritional needs. To meet the right whales energetic requirements they need about 500 kg of C. finmarchicus a day. Each copepod measures about 2–4 millimetres long which is about the size of a grain of rice and they weigh, on average, between 1.0274 and 1.0452 g cm. A loss in C. finmarchicus has the potential to affect the right whales migration, reproduction, and/or ability to successfully nurse their young (only for lactating females). | 9 | Geochemistry |
In chemistry, the Terrace Ledge Kink model (TLK), which is also referred to as the Terrace Step Kink model (TSK), describes the thermodynamics of crystal surface formation and transformation, as well as the energetics of surface defect formation. It is based upon the idea that the energy of an atom’s position on a crystal surface is determined by its bonding to neighboring atoms and that transitions simply involve the counting of broken and formed bonds. The TLK model can be applied to surface science topics such as crystal growth, surface diffusion, roughening, and vaporization. | 7 | Physical Chemistry |
Two of the drugs three components were originally developed at the Public Health Agency of Canadas National Microbiology Laboratory (NML), and a third at the U.S. Army Medical Research Institute of Infectious Diseases; the cocktail was optimized by Gary Kobinger, then branch chief of the NML, and is undergoing further development by Leaf Biopharmaceutical (LeafBio, Inc.), a San Diego-based arm of Mapp Biopharmaceutical. LeafBio created ZMapp in collaboration with its parent and Defyrus Inc., each of which had licensed its own cocktail of antibodies, called MB-003 and ZMab. | 1 | Biochemistry |
In inorganic chemistry, metal–metal bonds describe attractive interactions between metal centers. The simplest examples are found in bimetallic complexes. Metal–metal bonds can be "supported", i.e. be accompanied by one or more bridging ligands, or "unsupported". They can also vary according to bond order. The topic of metal–metal bonding is usually discussed within the framework of coordination chemistry, but the topic is related to extended metallic bonding, which describes interactions between metals in extended solids such as bulk metals and metal subhalides. | 7 | Physical Chemistry |
Nanorods, similar in size to quantum dots, have tunable optical and electronic properties. Based on their size and material composition, it is possible to tune the maximum absorption peak for nanorods during their synthesis. This control has led to the creation of photosensitizing nanorods. | 5 | Photochemistry |
The BBE-like enzyme's optimum pH is 8.9, this means it works in an alkaline medium, but the isoelectric point of the homogeneous enzyme is located at pH 4.9, which is a rather an acid medium. This value was obtained with isoelectric focusing and chromatofocusing techniques.
The enzyme broad temperature range is between 40-50 degrees Celsius. The molecular weight of the protein was determined by two processes that show two different results: by SDS gel electrophoresis comes to be 54 kD, and by gel filtration on AcA 54 the enzyme corresponds to a molecular weight of 49 kD, adopting globular shape. A purification study shows that the true molecular weight is in the range of 52 ±4 kD.
On the other hand, total activity decreases drastically during the stationary phase. | 1 | Biochemistry |
* Lactase (breaks down lactose into glucose and galactose)
* Maltase (breaks down maltose into 2 glucoses)
* Sucrase (breaks down sucrose into glucose and fructose)
* Trehalase (breaks down trehalose into 2 glucoses)
<br />For a thorough scientific overview of small-intestinal disaccharidases, one can consult chapter 75 of OMMBID. For more online resources and references, see inborn error of metabolism. | 1 | Biochemistry |
A major pathway of induced health effects arises from spills or leaks of solvents, especially chlorinated solvents, that reach the underlying soil. Since solvents readily migrate substantial distances, the creation of widespread soil contamination is not uncommon; this is particularly a health risk if aquifers are affected. Vapor intrusion can occur from sites with extensive subsurface solvent contamination. | 2 | Environmental Chemistry |
Diamonds cubic structure is in the Fdm space group (space group 227), which follows the face-centered cubic Bravais lattice. The lattice describes the repeat pattern; for diamond cubic crystals this lattice is "decorated" with a motif of two tetrahedrally bonded atoms in each primitive cell, separated by of the width of the unit cell in each dimension. The diamond lattice can be viewed as a pair of intersecting face-centered cubic lattices, with each separated by of the width of the unit cell in each dimension. Many compound semiconductors such as gallium arsenide, β-silicon carbide, and indium antimonide adopt the analogous zincblende structure, where each atom has nearest neighbors of an unlike element. Zincblendes space group is F3m, but many of its structural properties are quite similar to the diamond structure.
The atomic packing factor of the diamond cubic structure (the proportion of space that would be filled by spheres that are centered on the vertices of the structure and are as large as possible without overlapping) is significantly smaller (indicating a less dense structure) than the packing factors for the face-centered and body-centered cubic lattices. Zincblende structures have higher packing factors than 0.34 depending on the relative sizes of their two component atoms.
The first-, second-, third-, fourth-, and fifth-nearest-neighbor distances in units of the cubic lattice constant are respectively. | 3 | Analytical Chemistry |
Soldiers can be exposed to a wide variety of chemical hazards. These threats are mostly invisible but detectable by hyperspectral imaging technology. The Telops Hyper-Cam, introduced in 2005, has demonstrated this at distances up to 5 km. | 7 | Physical Chemistry |
The Henrys law constants mentioned so far do not consider any chemical equilibria in the aqueous phase. This type is called the intrinsic, or physical, Henrys law constant. For example, the intrinsic Henry's law solubility constant of formaldehyde can be defined as
In aqueous solution, formaldehyde is almost completely hydrated:
The total concentration of dissolved formaldehyde is
Taking this equilibrium into account, an effective Henry's law constant can be defined as
For acids and bases, the effective Henrys law constant is not a useful quantity because it depends on the pH of the solution. In order to obtain a pH-independent constant, the product of the intrinsic Henrys law constant and the acidity constant is often used for strong acids like hydrochloric acid (HCl):
Although is usually also called a Henrys law constant, it is a different quantity and it has different units than . | 7 | Physical Chemistry |
A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds.
Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for water is HO: this means that each molecule of water is constituted by 2 atoms of hydrogen (H) and 1 atom of oxygen (O). The chemical composition of water may be interpreted as a 2:1 ratio of hydrogen atoms to oxygen atoms. Different types of chemical formulas are used to convey composition information, such as an empirical or molecular formula.
Nomenclature can be used to express not only the elements present in a compound but their arrangement within the molecules of the compound. In this way, compounds will have unique names which can describe their elemental composition. | 3 | Analytical Chemistry |
Interchange pathways apply to substitution reactions where intermediates are not observed, which is more common than pure dissociative pathways. If the reaction rate is insensitive to the nature of the attacking nucleophile, the process is called dissociative interchange, abbreviated I. An illustrative process comes from the "anation" (reaction with an anion) of cobalt(III) complexes: | 0 | Organic Chemistry |
The thermodynamics of the host and guest interaction can be assessed by NMR spectroscopy, UV/visible spectroscopy, and isothermal titration calorimetry. Quantitative analysis of binding constant values provides useful thermodynamic information.
An association constant, can be defined by the expression
where {HG} is the thermodynamic activity of the complex at equilibrium. {H} represents the activity of the host and {G} the activity of the guest. The quantities , and are the corresponding concentrations and is a quotient of activity coefficients.
In practice the equilibrium constant is usually defined in terms of concentrations.
When this definition is used, it is implied that the quotient of activity coefficients has a numerical value of one. It then appears that the equilibrium constant, has the dimension 1/concentration, but that cannot be true since the standard Gibbs free energy change, is proportional to the logarithm of K.
This apparent paradox is resolved when the dimension of is defined to be the reciprocal of the dimension of the quotient of concentrations. The implication is that is regarded as having a constant value under all relevant experimental conditions. Nevertheless it is common practice to attach a dimension, such as millimole per litre or micromole per litre, to a value of K that has been determined experimentally.
A Large value indicates that host and guest molecules interact strongly to form the host–guest complex. | 6 | Supramolecular Chemistry |
Coherent anti-Stokes Raman spectroscopy (CARS) is a non-
linear process in which the energy difference of a pair of incoming photons
matches the energy of the vibrational mode of a molecular bond of interest.
This phonon population is coherently probed by a third photon and anti-
Stokes radiation is emitted. | 3 | Analytical Chemistry |
In 1957, Ronald Breslow proposed that a relatively stable nucleophilic carbene, a thiazol-2-ylidene derivative of vitamin B (thiamine), was the catalyst involved in the benzoin condensation that yields furoin from furfural.
In this cycle, the vitamin's thiazolium ring exchanges a hydrogen atom (attached to carbon 2 of the ring) for a furfural residue. In deuterated water, the C2-proton was found to rapidly exchange for a deuteron in a statistical equilibrium.
This exchange was proposed to proceed via intermediacy of a thiazol-2-ylidene. In 2012 the isolation of the so-called Breslow intermediate was reported.
In 1960, Hans-Werner Wanzlick and coworkers conjectured that carbenes derived from dihydroimidazol-2-ylidene were produced by vacuum pyrolysis of the corresponding 2-trichloromethyl dihydroimidazole compounds with the loss of chloroform.
They conjectured that the carbene existed in equilibrium with its dimer, a tetraaminoethylene derivative, the so-called Wanzlick equilibrium. This conjecture was challenged by Lemal and coworkers in 1964, who presented evidence that the dimer did not dissociate; and by Winberg in 1965. However, subsequent experiments by Denk, Herrmann and others have confirmed this equilibrium, albeit in specific circumstances. | 0 | Organic Chemistry |
The principles involved can be understood by considering the most efficient way of packing together equal-sized spheres and stacking close-packed atomic planes in three dimensions. For example, if plane A lies beneath plane B, there are two possible ways of placing an additional atom on top of layer B. If an additional layer were placed directly over plane A, this would give rise to the following series:
:...ABABABAB...
This arrangement of atoms in a crystal structure is known as hexagonal close packing (hcp).
If, however, all three planes are staggered relative to each other and it is not until the fourth layer is positioned directly over plane A that the sequence is repeated, then the following sequence arises:
:...ABCABCABC...
This type of structural arrangement is known as cubic close packing (ccp).
The unit cell of a ccp arrangement of atoms is the face-centered cubic (fcc) unit cell. This is not immediately obvious as the closely packed layers are parallel to the {111} planes of the fcc unit cell. There are four different orientations of the close-packed layers. | 3 | Analytical Chemistry |
IBX is notable for oxidizing vicinal diols (or glycols) to diketones without cleavage of the carbon-carbon bond, but oxidative cleavage of glycols to two aldehydes or ketones can occur when modified conditions are used (elevated temperatures or trifluoroacetic acid solvent).
The reaction mechanism for this glycol cleavage is based on initial formation of an adduct between 10-I-4 IBX and DMSO to a 12-I-5 intermediate 3 in which DMSO acts as a leaving group for incoming alcohol 4 to intermediate 5. One equivalent of water is split off forming 12-I-5 spirobicyclic periodinane 6 setting the stage for fragmentation to 7. With hydroxyl alpha protons present, oxidation to the acyloin competes. Trifluoroacetic acid is found to facilitate the overall reaction. | 0 | Organic Chemistry |
The furanose ring is a cyclic hemiacetal of an aldopentose or a cyclic hemiketal of a ketohexose.
A furanose ring structure consists of four carbon and one oxygen atom with the anomeric carbon to the right of the oxygen. The highest numbered chiral carbon (typically to the left of the oxygen in a Haworth projection) determines whether or not the structure has a -configuration or -configuration. In an -configuration furanose, the substituent on the highest numbered chiral carbon is pointed downwards out of the plane, and in a -configuration furanose, the highest numbered chiral carbon is facing upwards.
The furanose ring will have either alpha or beta configuration, depending on which direction the anomeric hydroxy group is pointing. In a -configuration furanose, alpha configuration has the hydroxy pointing down, and beta has the hydroxy pointing up. It is the opposite in an -configuration furanose. Typically, the anomeric carbon undergoes mutarotation in solution, and the result is an equilibrium mixture of α and β configurations. | 0 | Organic Chemistry |
Another family of carbonyl-based PPGs exists that is structurally like the phenacyl motif, but which reacts through a separate mechanism. As the name suggests, these PPGs react through abstraction of the carbonyl's γ-hydrogen. The compound is then able to undergo a photoenolization, which is mechanistically like a keto-enol tautomerization. From the enol form, the compound can finally undergo a ground-state transformation that releases the substrate. The quantum yield of this mechanism directly corresponds to the ability of the protected substrate to be a good leaving group. For good leaving groups, the rate-determining step is either hydrogen abstraction or isomerization; however, if the substrate is a poor leaving group, release is the rate-determining step. | 5 | Photochemistry |
Ortho esters can be prepared by the Pinner reaction, in which nitriles react with alcohols in the presence of one equivalent of hydrogen chloride. The reaction proceeds by formation of imido ester hydrochloride:
:RCN + R′OH + HCl → [RC(OR′)=NH]Cl
Upon standing in the presence of excess alcohol, this intermediate converts to the ortho ester:
:[RC(OR′)=NH]Cl + 2R′OH → RC(OR′) + NHCl
The reaction requires anhydrous conditions.
Although a less common method, ortho esters were first produced by reaction of 1,1,1-trichloroalkanes with sodium alkoxide:
:RCCl + 3NaOR′ → RC(OR′) + 3NaCl | 0 | Organic Chemistry |
Illustrative of their alkylating activity are reactions with potassium iodide in acetone, chloroacetone reacts faster than 1-chloropropane by a factor of 36,000. Halo ketones react with phosphites in the Perkow reaction.
The halo group can be removed in reductive dehalogenation of halo ketones. α-Halo ketones can also be converted to alkenes by treatment with hydrazine.
Due to the presence of two electron withdrawing groups (carbonyl and halide), the α-hydrogen is acidic. This property is exploited in the Favorskii rearrangement, where base abstracts first an acidic α-hydrogen and the resulting carbanion then displaces the halogen.
In crossed aldol reactions between halo ketones and aldehydes, the initial reaction product is a halohydrin which can subsequently form an oxirane in the presence of base.
α-Halo ketones can react with amines to form an α-halo imine, which can be converted back to the parent halo ketone by hydrolysis, so that halo imines may be used as masked versions of halo ketones. This allows some chemical transformations to be achieved that are not possible with the parent halo ketones directly. | 0 | Organic Chemistry |
Plasmid preparation can be divided into five main categories based on the scale of the preparation: minipreparation, midipreparation, maxipreparation, megapreparation, and gigapreparation. The choice of which method to use will depend on the amount of plasmid DNA required, as well as the specific application for which it will be used.
Kits are available from varying manufacturers to purify plasmid DNA, which are named by size of bacterial culture and corresponding plasmid yield. In increasing order they are: miniprep, midiprep, maxiprep, megaprep, and gigaprep. The plasmid DNA yield will vary depending on the plasmid copy number, type and size, the bacterial strain, the growth conditions, and the kit. | 1 | Biochemistry |
The term is used in pathology, for example in calcareous conjunctivitis, and when referring to calcareous metastasis or calcareous deposits, which may both be removed surgically. | 9 | Geochemistry |
Sphingosine is synthesized from palmitoyl CoA and serine in a condensation required to yield dihydrosphingosine.
Dehydrosphingosine is then reduced by NADPH to dihydrosphingosine (sphinganine), acylated to dihydroceramide finally oxidized by FAD to ceramide. Sphingosine is then solely formed via degradation of sphingolipid in the lysosome. | 1 | Biochemistry |
Several methods are being pursued for controlling gene expression spatially, temporally and in different degrees. One method is by using operon inducer/repressor system which provides temporal control of gene expression. To control gene expression spatially inkjet printers are under development for printing ligands on gel culture. Other popular method involves use of light to control gene expression in spatiotemporal fashion. Since light can also be controlled easily in space, time and degree, several methods of controlling gene expression at DNA and RNA level have been developed and are under study. For example, RNA interference can be controlled using light and also patterning of gene expression has been performed in cell monolayer and in zebrafish embryos using caged morpholino or peptide nucleic acid demonstrating the control of gene expression spatiotemporally. Recently light based control has been shown at DNA level using transgene based system or caged triplex forming oligos | 1 | Biochemistry |
Back-of-house testing is more restrictive. The substances tested do not come directly from event participants. Instead, they may come from samples confiscated by police or event security or samples that are disposed of via drug amnesty bins. The results may not be available to event attendees. | 3 | Analytical Chemistry |
K2.3 contains 6 transmembrane domains, a pore-forming region, and intracellular N- and C- termini and is readily blocked by apamin. The gene for K2.3, KCNN3, is located on chromosome 1q21. | 1 | Biochemistry |
There is a half-life describing any exponential-decay process. For example:
*As noted above, in radioactive decay the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay. It varies depending on the atom type and isotope, and is usually determined experimentally. See List of nuclides.
*The current flowing through an RC circuit or RL circuit decays with a half-life of or , respectively. For this example the term half time tends to be used rather than "half-life", but they mean the same thing.
*In a chemical reaction, the half-life of a species is the time it takes for the concentration of that substance to fall to half of its initial value. In a first-order reaction the half-life of the reactant is , where (also denoted as ) is the reaction rate constant. | 7 | Physical Chemistry |
Many reactions in organic chemistry can occur in either an intramolecular or intermolecular senses. Some reactions are by definition intramolecular or are only practiced intramolecularly, e.g.,
* Dieckmann condensation of diesters is the intramolecular version of aldol condensation.
* Madelung synthesis of indoles
* Smiles rearrangement
* Hydroacylation is almost invariably practiced intramolecularly to produce ketones.
:RCHO + CH=CHR → RC(O)CHCHR
* Nazarov cyclization reaction for the synthesis of cyclopentenones
*The Wurtz reaction, involving reductive coupling of alkyl halides, essentially is only useful when conducted intramolecularly. Its utility is illustrated with the synthesis of strained rings:
Some transformations that are enabled or enhanced intramolecularly. For example, the acyloin condensation of diesters almost uniquely produces 10-membered carbocycles, which are difficult to construct otherwise. Another example is the 2+2 cycloaddition of norbornadiene to give quadricyclane. | 0 | Organic Chemistry |
In accordance with the terms of IOP purchase, Fulmer's capital investment in new facilities was expected to be financed from profit and Fulmer would make a modest annual contribution to IOP funds.
However, Fulmer's recent expansion and its large investment in capital equipment required increasing bank borrowing. Considerable management effort and other resources had been taken up with the transfer of facilities between Fulmer, Chessington, Ashtead, Redhill and Slough and there had been a damaging fire at Ashtead.
It was clear that alternative sources of finance were needed. A management buyout was explored and found to be not feasible. Preparations were made for a stock exchange flotation but, in the late 1980s Fulmer sustained large losses and plans to float were postponed.
The balance of Fulmer's activities had changed. Academic research was now a minor part of its work. Most of its income came from testing, consultancy and small scale manufacture. The IOP were becoming concerned that their ownership of Fulmer as a commercial organization might be judged incompatible with their charitable status as a learned society. They were also concerned that Fulmer was making losses and had a growing overdraft. The IOP Council finally decided to sell Fulmer. | 8 | Metallurgy |
Although Jaffes name is synonymous with clinical creatinine testing, his paper only described the principle behind what would later become the enduring method. It was Otto Folin (1867–1934), a Harvard biochemist, who adapted Jaffes research—abandoning the standard Neubauer reaction of the time—and published several papers using the Jaffe reaction to analyze creatinine levels in both blood and urine. Folin began using the picric acid procedure in 1901 and included it in his 1916 Lab Manual of Biological Chemistry. During his career, Folin modified and improved several quantitative colorimetric procedures, the first of which was for creatinine. He took advantage of technology available at the time, using a Duboscq colorimeter for measurement precision, and is credited for introducing colorimetry into modern biochemical analysis.
Folin's research did not focus on creatinine as a renal function indicator. Since the precursors of creatinine are synthesized in the liver, at this point in history, creatinine was considered indicative of liver function. It was not until 1926 that Poul Kristian Brandt Rehberg suggested creatinine was a significant marker for renal function. | 1 | Biochemistry |
The defensive spray of skunks consists mainly of low-molecular-weight thiols and derivatives with a foul odor, which protects the skunk from predators. Owls are able to prey on skunks, as they lack a sense of smell. | 0 | Organic Chemistry |
When a heat ray arrives at a body they may interact in three different ways:
# The body may absorb the heat
# The body may reflect the heat
# The heat may transmit through the body
Absorption and reflection are typically modeled as surface phenomena that occur within a fraction of a micrometer of the surface. For example, a highly polished piece of steel will be highly reflective, regardless of the material under the surface. Transmission on the other hand is a volumetric phenomena that is dependent on the properties of the entire thickness of the body. A glass window for instance must be translucent through its entire thickness for radiation to get through.
The term absorption is used to describe the change of heat into other forms of energy when it contacts particle or body. Only material particles can absorb heat rays, not elements of surfaces. For a given frequency of radiation, all mediums have a coefficient of absorption, that represents how much heat will be absorbed per unit distance through a medium. | 7 | Physical Chemistry |
In Sisyphus cooling, the two hyperfine ground states of experience equal and opposite AC Stark shifts from the near-resonant counter-propagating beams. The beams also effect a polarization gradient, alternating between linear and circular polarizations. The potential energy maxima of one coincide with pure circular polarization, which optically pumps atoms to the other , which experiences its minima in the same location. Over time, the atoms expend their kinetic energy traversing the potential energy landscape and transferring the potential energy difference between the crests and troughs of the AC-Stark-shifted ground state levels to emitted photons.
In contrast, gray molasses only has one sinusoidally light-shifted ground state; optical pumping at the peaks of this potential energy landscape takes atoms to the dark state, which can selectively evolve to the bright state and re-enter the cycle with sufficient momentum. Sisyphus cooling is difficult to implement when the excited state manifold is poorly-resolved (i.e. whose hyperfine spacing is comparable to or less than the constituent linewidths); in these atomic species, the Raman-type gray molasses is preferable. | 7 | Physical Chemistry |
Analogous to sulfamic acid (HNSO) and as is the case generally for amino acids, HOSA exists in the solid state as a zwitterion: HNOSO. It resembles an ammonia molecule coordinate covalently bonded to a sulfate group. | 0 | Organic Chemistry |
Resazurin can be used as one of a series of rapid tests to determine the quality of a milk sample. In this test, resazurin is added as a violet redox dye which turns mauvish-pink due to conversion to resorufin and then to colourless dihydroresorufin. This happens due to lowering of the oxidation-reduction potential in the milk sample caused by presence of bacteria which utilize available oxygen present in the milk for aerobic respiration. The rate of the colour change is used as an index for the number of bacteria present in the milk sample. | 3 | Analytical Chemistry |
Fulgurites have been classified by Pasek et al. (2012) into five types related to the type of sediment in which the fulgurite formed, as follows:
* Type I – sand fulgurites with tubaceous structure; their central axial void may be collapsed
* Type II – soil fulgurites; these are glass-rich, and form in a wide range of sediment compositions, including clay-rich soils, silt-rich soils, gravel-rich soils, and loessoid; these may be tubaceous, branching, vesicular, irregular/slaggy, or may display a combination of these structures, and can produce exogenic fulgurites (droplet fulgurites)
* Type III – caliche or calcic sediment fulgurites, having thick, often surficially glazed granular walls with calcium-rich vitreous groundmass with little or no lechatelierite glass; their shapes are variable, with multiple narrow central channels common, and can span the entire range of morphological and structural variation for fulguritic objects
* Type IV – rock fulgurites, which are either crusts on minimally altered rocks, networks of tunneling within rocks, vesicular outgassed rocks (often glazed by a silicide-rich and/or metal oxide crust), or completely vitrified and dense rock material and masses of these forms with little sedimentary groundmass
* Type V – [droplet] fulgurites (exogenic fulgurites), which show evidence of ejection (e.g. spheroidal, filamentous, or aerodynamic), related by composition to Type II and Type IV fulgurites
* phytofulgurite – a proposed class of objects resulting from partial to total alteration of biomass (e.g. grasses, lichens, moss, wood) by lightning. Pasek et al. (2012) described fulgurites as "natural glasses formed by cloud-to-ground lightning." Pasek et al. excluded phytofulgurites from their classification scheme because they are not glasses, so classifying them as a subset of fulgurites is debatable. | 9 | Geochemistry |
The receptor has a broad tissue distribution but is especially abundant in the cerebellum. Most of the InsP3Rs are found integrated into the endoplasmic reticulum. | 1 | Biochemistry |
* Wide range of genomic applications and scientific questions, including de novo genome assembly, haplotype phasing, structural variant analysis, and transcriptome and epigenetic analysis.
* Accuracy and scalability.
* Method requires small quantities of input DNA, which can be beneficial for small samples or single cell studies.
* More cost effective per sample in comparison with long-read technologies such as Oxford Nanopore sequencing.
* Libraries produced by linked-read can be processed using Illumina short read sequencing, increasing accessibility. | 1 | Biochemistry |
Kode FSL constructs consist of three components; a functional moiety (F), a spacer (S) and a lipid (L).
Function groups on FSL constructs that can be used to create kodecytes include saccharides (including ABO blood group-related determinants, sialic acids, hyaluronin polysaccharides), fluorophores, biotin, and a range of peptides.
Although kodecytes are created by modifying natural cells, they are different from natural cells. For example, FSL constructs, influenced by the composition of the lipid tail, are laterally mobile in the membrane and some FSL constructs may also cluster due to the characteristics of the functional group (F). As FSL constructs are anchored in the membrane via a lipid tail (L) it is believed they do not participate in signal transduction, but may be designed to act as agonists or antagonists of the initial binding event. FSL constructs will not actively pass through the plasma membrane but may enter the cell via membrane invagination and endocytosis.
The "koding" of cells is stable (subject to the rate of turnover of the membrane components). FSL constructs will remain in the membrane of inactive cells (e.g. red blood cells) for the life of the cell provided it is stored in lipid free media. In the peripheral circulation FSL constructs are observed to be lost from red cell kodecytes at a rate of about 1% per hour. The initial "koding" dose and the minimum level required for detection determine how long the presence of "kodecytes" in the circulation can be monitored. For red blood "kodecytes" reliable monitoring of the presence of the "kodecytes" for up to 3 days post intravenous administration has been demonstrated in small mammals.
The spacer (S) of a FSL construct has been selected so as to have negligible cross-reactivity with serum antibodies so kodecytes can be used with undiluted serum. By increasing the length of the FSL spacer from 1.9 to 7.2 nm it has been shown sensitivity can improve two-fold in red cell agglutination based kodecyte assays. However, increasing the size of the spacer further from 7.2 to 11.5 nm did not result in any further enhancement. | 1 | Biochemistry |
With the development of bioconjugation technology, there are plenty of options to covalently ligating an artificial metal cofactor onto a protein: i) cysteine residue based chemistry like: Cys-meleimide, Cys-α-haloketone, Cys-benzylhalide chemistry and disulfide formation, ii) post-translational bioorthogonal modification based on Amber suppression (e.g., Click chemistry) and iii) enzyme active site modification (e.g., covalent bond formation between lipase and lipase inhibitor).
The video shows an example using reaction between cysteine residue and α-haloketone to introduce a phenanthroline ligand into an adipocyte lipid binding protein. In this context, the ArM can selectively hydrolyze certain racemic esters. | 0 | Organic Chemistry |
The Dallol area lies up to below sea level, and has been repeatedly flooded in the past when waters from the Red Sea have flowed into the depression. The last separation from the Red Sea was about 30,000 years ago.
The discovery of the volcano by the first European settlers certainly dates from the first colonization and expeditions in the region, in the 17th or 18th century. But the hostility of the depression, the unbearable heat which reigns there, and the dangers of the site (acid basins, toxic fumes), did not favour the exploration of the zones close to the crater. On the contrary, the Erta Ale was much more accessible, especially because the part of the rift where it is located (called the Erta Ale Range), is significantly higher. The last eruption of this phreato-magmatic volcano dates back to 2011. | 9 | Geochemistry |
Members of the MAPK family can be found in every eukaryotic organism examined so far. In particular, both classical and atypical MAP kinases can be traced back to the root of the radiation of major eukaryotic groups. Terrestrial plants contain four groups of classical MAPKs (MAPK-A, MAPK-B, MAPK-C and MAPK-D) that are involved in response to myriads of abiotic stresses. However, none of these groups can be directly equated to the clusters of classical MAPKs found in opisthokonts (fungi and animals). In the latter, the major subgroups of classical MAPKs form the ERK/Fus3-like branch (that is further sub-divided in metazoans into ERK1/2 and ERK5 subgroups), and the p38/Hog1-like kinases (that has also split into the p38 and the JNK subgroups in multicellular animals). In addition, there are several MAPKs in both fungi and animals, whose origins are less clear, either due to high divergence (e.g. NLK), or due to possibly being an early offshoot to the entire MAPK family (ERK3, ERK4, ERK7). In vertebrates, due to the twin whole genome duplications after the cephalochordate/vertebrate split, there are several paralogs in every group. Thus ERK1 and ERK2 both correspond to the Drosophila kinase rolled, JNK1, JNK2 and JNK3 are all orthologous to the gene basket in Drosophila. Although among the p38 group, p38 alpha and beta are clearly paralogous pairs, and so are p38 gamma and delta in vertebrates, the timing of the base split is less clear, given that many metazoans already possess multiple p38 homologs (there are three p38-type kinases in Drosophila, Mpk2(p38a), p38b and p38c). The single ERK5 protein appears to fill a very specialized role (essential for vascular development in vertebrates) wherever it is present. This lineage has been deleted in protostomes, together with its upstream pathway components (MEKK2/3, MKK5), although they are clearly present in cnidarians, sponges and even in certain unicellular organisms (e.g. the choanoflagellate Monosiga brevicollis) closely related to the origins of multicellular animals.
The split between classical and some atypical MAP kinases happened quite early. This is suggested not just by the high divergence between extant genes, but also recent discoveries of atypical MAPKs in primitive, basal eukaryotes. The genome sequencing of Giardia lamblia revealed the presence of two MAPK genes, one of them similar to the already-well-known mammalian MAPKs (ERKs, p38s, etc.), the other one showing similarities to the mammalian ERK7 protein. The situation is similar in the multicellular amoeba Dictyostelium discoideum, where the ddERK1 protein appears to be a classical MAPK, while ddERK2 more closely resembles our ERK7 and ERK3/4 proteins. Atypical MAPKs can also be found in higher plants, although they are poorly known. Similar to the situation in mammals, most aspects of atypical MAPKs are uncharacterized due to the lack of research focus on this area. | 1 | Biochemistry |
Tumor necrosis factor receptor 2 (TNFR2), also known as tumor necrosis factor receptor superfamily member 1B (TNFRSF1B) and CD120b, is one of two membrane receptors that binds tumor necrosis factor-alpha (TNFα). Like its counterpart, tumor necrosis factor receptor 1 (TNFR1), the extracellular region of TNFR2 consists of four cysteine-rich domains which allow for binding to TNFα. TNFR1 and TNFR2 possess different functions when bound to TNFα due to differences in their intracellular structures, such as TNFR2 lacking a death domain (DD). | 1 | Biochemistry |
Levofloxacin and later generation fluoroquinolones are collectively referred to as "respiratory quinolones" to distinguish them from earlier fluoroquinolones which exhibited modest activity toward the important respiratory pathogen Streptococcus pneumoniae.
The drug exhibits enhanced activity against the important respiratory pathogen Streptococcus pneumoniae relative to earlier fluoroquinolone derivatives like ciprofloxacin. For this reason, it is considered a "respiratory fluoroquinolone" along with more recently developed fluoroquinolones such as moxifloxacin and gemifloxacin. It is less active than ciprofloxacin against Gram-negative bacteria, especially Pseudomonas aeruginosa, and lacks the anti-methicillin-resistant Staphylococcus aureus (MRSA) activity of moxifloxacin and gemifloxacin. Levofloxacin has shown moderate activity against anaerobes, and is about twice as potent as ofloxacin against Mycobacterium tuberculosis and other mycobacteria, including Mycobacterium avium complex.
Its spectrum of activity includes most strains of bacterial pathogens responsible for respiratory, urinary tract, gastrointestinal, and abdominal infections, including Gram negative (Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Moraxella catarrhalis, Proteus mirabilis, and Pseudomonas aeruginosa), Gram positive (methicillin-sensitive but not methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, Staphylococcus epidermidis, Enterococcus faecalis, and Streptococcus pyogenes), and atypical bacterial pathogens (Chlamydophila pneumoniae and Mycoplasma pneumoniae). Compared to earlier antibiotics of the fluoroquinoline class such as ciprofloxacin, levofloxacin exhibits greater activity towards Gram-positive bacteria but lesser activity toward Gram-negative bacteria, especially Pseudomonas aeruginosa. | 4 | Stereochemistry |
For pure elements or compounds, e.g. pure copper, pure water, etc. the liquidus and solidus are at the same temperature, and the term melting point may be used.
There are also some mixtures which melt at a particular temperature, known as congruent melting. One example is eutectic mixture. In a eutectic system, there is particular mixing ratio where the solidus and liquidus temperatures coincide at a point known as the invariant point. At the invariant point, the mixture undergoes a eutectic reaction where both solids melt at the same temperature. | 7 | Physical Chemistry |
Artists and metalworkers often deliberately add patinas as a part of the original design and decoration of art and furniture, or to simulate antiquity in newly made objects. The process is often called distressing.
A wide range of chemicals, both household and commercial, can give a variety of patinas. They are often used by artists as surface embellishments either for color, texture, or both. Patination composition varies with the reacted elements and these will determine the color of the patina. For copper alloys, such as bronze, exposure to chlorides leads to green, while sulfur compounds (such as "liver of sulfur") tend to brown. The basic palette for patinas on copper alloys includes chemicals like ammonium sulfide (blue-black), liver of sulfur (brown-black), cupric nitrate (blue-green), and ferric nitrate (yellow-brown). For artworks, patination is often deliberately accelerated by applying chemicals with heat. Colors range from matte sandstone yellow to deep blues, greens, whites, reds, and various blacks. Some patina colors are achieved by the mixing of colors from the reaction with the metal surface with pigments added to the chemicals. Sometimes the surface is enhanced by waxing, oiling, or other types of lacquers or clear-coats. More simply, the French sculptor Auguste Rodin used to instruct assistants at his studio to urinate over bronzes stored in the outside yard. A patina can be produced on copper by the application of vinegar (acetic acid). This patina is water-soluble and will not last on the outside of a building like a "true" patina. It is usually used as pigment.
Patina is also found on slip rings and commutators. This type of patina is formed by corrosion, what elements the air might hold, residue from the wear of the carbon brush, and moisture; thus, the patina needs special conditions to work as intended.
Patinas can also be found in woks or other metal baking dishes. The process of applying patinas to cookware is known as seasoning. The patina on a wok is a dark coating of oils that have been polymerized onto it to prevent food from sticking. Scrubbing or using soap on a wok or other dishware could damage the patina and possibly allow rust.
Knife collectors that own carbon steel blades sometimes force a patina onto the blade to help protect it and give it a more personalized look. This can be done using various chemicals and substances such as muriatic acid, apple cider vinegar, or mustard. It can also be done by sticking the blade into any acidic vegetable or fruit such as an orange or an apple. | 8 | Metallurgy |
Mixtures of complex acids can be resolved by thermometric titration with standard NaOH in aqueous solution. In a mixture of nitric, acetic and phosphoric acids used in the fabrication of semi-conductors, three endpoints could be predicted on the basis of the dissociation constants of the acids:
The key to determine the amount of each acid present in the mixture is the ability to obtain an accurate value for the amount of phosphoric acid present, as revealed by titration of the third proton of HPO.
Figure 10 illustrates a titration plot of this mixture, showing 3 sharp endpoints. | 3 | Analytical Chemistry |
Thiourea is a planar molecule. The C=S bond distance is 1.71 Å. The C-N distances average 1.33 Å. The weakening of the C-S bond by C-N pi-bonding is indicated by the short C=S bond in thiobenzophenone, which is 1.63 Å.
Thiourea occurs in two tautomeric forms, of which the thione form predominates in aqueous solutions. The equilibrium constant has been calculated as K is . The thiol form, which is also known as an isothiourea, can be encountered in substituted compounds such as isothiouronium salts. | 0 | Organic Chemistry |
The ICP-AES is composed of two parts: the ICP and the optical spectrometer. The ICP torch consists of 3 concentric quartz glass tubes. The output or "work" coil of the radio frequency (RF) generator surrounds part of this quartz torch. Argon gas is typically used to create the plasma.
The ICPs have two operation modes, called capacitive (E) mode with low plasma density and inductive (H) mode with high plasma density, and E to H heating mode transition occurs with external inputs. The torch is operated in the H mode.
When the torch is turned on, an intense electromagnetic field is created within the coil by the high power radio frequency signal flowing in the coil. This RF signal is created by the RF generator which is, effectively, a high power radio transmitter driving the "work coil" the same way a typical radio transmitter drives a transmitting antenna. Typical instruments run at either 27 or 40 MHz. The argon gas flowing through the torch is ignited with a Tesla unit that creates a brief discharge arc through the argon flow to initiate the ionization process. Once the plasma is "ignited", the Tesla unit is turned off.
The argon gas is ionized in the intense electromagnetic field and flows in a particular rotationally symmetrical pattern towards the magnetic field of the RF coil. A stable, high temperature plasma of about 7000 K is then generated as the result of the inelastic collisions created between the neutral argon atoms and the charged particles.
A peristaltic pump delivers an aqueous or organic sample into an analytical nebulizer where it is changed into mist and introduced directly inside the plasma flame. The sample immediately collides with the electrons and charged ions in the plasma and is itself broken down into charged ions. The various molecules break up into their respective atoms which then lose electrons and recombine repeatedly in the plasma, giving off radiation at the characteristic wavelengths of the elements involved.
In some designs, a shear gas, typically nitrogen or dry compressed air is used to cut the plasma at a specific spot. One or two transfer lenses are then used to focus the emitted light on a diffraction grating where it is separated into its component wavelengths in the optical spectrometer. In other designs, the plasma impinges directly upon an optical interface which consists of an orifice from which a constant flow of argon emerges, deflecting the plasma and providing cooling while allowing the emitted light from the plasma to enter the optical chamber. Still other designs use optical fibers to convey some of the light to separate optical chambers.
Within the optical chamber(s), after the light is separated into its different wavelengths (colours), the light intensity is measured with a photomultiplier tube or tubes physically positioned to "view" the specific wavelength(s) for each element line involved, or, in more modern units, the separated colors fall upon an array of semiconductor photodetectors such as charge coupled devices (CCDs). In units using these detector arrays, the intensities of all wavelengths (within the system's range) can be measured simultaneously, allowing the instrument to analyze for every element to which the unit is sensitive all at once. Thus, samples can be analyzed very quickly.
The intensity of each line is then compared to previously measured intensities of known concentrations of the elements, and their concentrations are then computed by interpolation along the calibration lines (use of a calibration curve).
In addition, special software generally corrects for interferences caused by the presence of different elements within a given sample matrix. | 3 | Analytical Chemistry |
As voltage is applied, the anions (and negatively charged sample molecules) migrate toward the positive electrode (anode) in the lower chamber, the leading ion is Cl ( high mobility and high concentration); glycinate is the trailing ion (low mobility and low concentration). SDS-protein particles do not migrate freely at the border between the Cl of the gel buffer and the Gly of the cathode buffer. Friedrich Kohlrausch found that Ohm's law also applies to dissolved electrolytes. Because of the voltage drop between the Cl and Glycine-buffers, proteins are compressed (stacked) into micrometer thin layers. The boundary moves through a pore gradient and the protein stack gradually disperses due to a frictional resistance increase of the gel matrix. Stacking and unstacking occurs continuously in the gradient gel, for every protein at a different position. For a complete protein unstacking the polyacrylamide-gel concentration must exceed 16% T. The two-gel system of "Laemmli" is a simple gradient gel. The pH discontinuity of the buffers is of no significance for the separation quality, and a "stacking-gel" with a different pH is not needed. | 1 | Biochemistry |
Another classic but elusive family of targets are silylenes, analogues of carbenes. It was proposed that dechlorination of dimethyldichlorosilane generates dimethylsilylene:
:SiCl(CH) + 2 K → Si(CH) + 2 KCl
This inference is supported by conducting the dechlorination in the presence of trimethylsilane, the trapped product being pentamethyldisilane:
:Si(CH) + HSi(CH) → (CH)Si(H)-Si(CH)
Not that the trapping agent does not react with dimethyldichlorosilane or potassium metal. | 3 | Analytical Chemistry |
Chaotropicity describes the entropic disordering of lipid bilayers and other biomacromolecules which is caused by substances dissolved in water. According to the original usage and work carried out on cellular stress mechanisms and responses, chaotropic substances do not necessarily disorder the structure of water.
The chaotropic activities of solutes in the aqueous phase (e.g. ethanol, butanol, urea, MgCl, and phenol) have been quantified using an agar-gelation assay. Whereas chaotropicity was first applied to studies of ions, it is equally applicable to alcohols, aromatics, ion mixtures, and other solutes. Furthermore, hydrophobic substances known to stress cellular systems (including benzene and toluene) can chaotropically disorder macromolecules and induce a chaotrope-stress response in microbial cells, even though they partition into the hydrophobic domains of macromolecular systems. | 1 | Biochemistry |
RNA therapeutics are a new class of medications based on ribonucleic acid (RNA). Research has been working on clinical use since the 1990s, with significant success in cancer therapy in the early 2010s. In 2020 and 2021, mRNA vaccines have been developed globally for use in combating the coronavirus disease (COVID-19 pandemic). The Pfizer–BioNTech COVID-19 vaccine was the first mRNA vaccine approved by a medicines regulator, followed by the Moderna COVID-19 vaccine, and others.
The main types of RNA therapeutics are those based on messenger RNA (mRNA), antisense RNA (asRNA), RNA interference (RNAi), and RNA aptamers. Of the four types, mRNA-based therapy is the only type which is based on triggering synthesis of proteins within cells, making it particularly useful in vaccine development. Antisense RNA is complementary to coding mRNA and is used to trigger mRNA inactivation to prevent the mRNA from being used in protein translation. RNAi-based systems use a similar mechanism, and involve the use of both small interfering RNA (siRNA) and micro RNA (miRNA) to prevent mRNA translation and/or degrade mRNA. However, RNA aptamers are short, single stranded RNA molecules produced by directed evolution to bind to a variety of biomolecular targets with high affinity thereby affecting their normal in vivo activity.
RNA is synthesized from template DNA by RNA polymerase with messenger RNA (mRNA) serving as the intermediary biomolecule between DNA expression and protein translation. Because of its unique properties (such as its typically single-stranded nature and its 2' OH group) and its ability to adopt many different secondary/tertiary structures, both coding and noncoding RNAs have attracted attention in medicine. Research has begun to explore RNAs potential to be used for therapeutic benefit, and unique challenges have occurred during drug discovery and implementation of RNA therapeutics. | 1 | Biochemistry |
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