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There are numerous companies that offer calibration for spectrometers, but not all are equal. It is important to find a traceable, certified laboratory to perform calibration. The calibration certificate should state the light source used (ex: Halogen, Deuterium, Xenon, LED), and the uncertainty of the calibration for each band (UVC, UVB, VIS..), each wavelength in nm, or for the full spectrum measured. It should also list the confidence level for the calibration uncertainty. | 7 | Physical Chemistry |
Propidium monoazide (PMA) is a photoreactive DNA-binding dye that preferentially binds to dsDNA. It is used to detect viable microorganisms by qPCR. Visible light (high power halogen lamps or specific LED devices) induces a photoreaction of the chemical that will lead to a covalent bond with PMA and the dsDNA. The mechanism of DNA modification by PMA can be seen in this protocol. This process renders the DNA insoluble and results in its loss during subsequent genomic DNA extraction. Theoretically, dead microorganisms lose their capability to maintain their membranes intact, which leaves the "naked" DNA in the cytosol ready to react with PMA. DNA of living organisms are not exposed to the PMA, as they have an intact cell membrane. After treatment with the chemical, only the DNA from living bacteria is usable in qPCR, allowing to obtain only the amplified DNA of living organisms. This is helpful in determining which pathogens are active in specific samples. The main use of PMA is in Viability PCR but the same principle can be applied in flow cytometry or fluorescence microscopy.
However, the ability of PMA in differentiating viable and non-viable cells varies for different bacteria. An example is that the permeability of PMA to gram-positive and gram-negative cell membranes is different. Therefore, the application of PMA to mixed communities is still limited.
PMA was developed at Biotium, Inc. as an improvement on ethidium monoazide (EMA). PMA provides better discrimination between live and dead bacteria because it is excluded from live cells more efficiently than EMA. | 1 | Biochemistry |
*Promoter (genetics), a sequence of DNA to which proteins bind to initiate transcription
*Protomer (structural biology), a structural unit of an oligomeric protein | 7 | Physical Chemistry |
Superconductivity was discovered on April 8, 1911, by Heike Kamerlingh Onnes, who was studying the resistance of solid mercury at cryogenic temperatures using the recently produced liquid helium as a refrigerant. At the temperature of 4.2 K, he observed that the resistance abruptly disappeared. In the same experiment, he also observed the superfluid transition of helium at 2.2 K, without recognizing its significance. The precise date and circumstances of the discovery were only reconstructed a century later, when Onnes's notebook was found. In subsequent decades, superconductivity was observed in several other materials. In 1913, lead was found to superconduct at 7 K, and in 1941 niobium nitride was found to superconduct at 16 K.
Great efforts have been devoted to finding out how and why superconductivity works; the important step occurred in 1933, when Meissner and Ochsenfeld discovered that superconductors expelled applied magnetic fields, a phenomenon which has come to be known as the Meissner effect. In 1935, Fritz and Heinz London showed that the Meissner effect was a consequence of the minimization of the electromagnetic free energy carried by superconducting current. | 7 | Physical Chemistry |
Enzymatically active lactate dehydrogenase is consisting of four subunits (tetramer). The two most common subunits are the LDH-M and LDH-H peptides, named for their discovery in muscle and heart tissue, and encoded by the LDHA and LDHB genes, respectively. These two subunits can form five possible tetramers (isoenzymes): LDH-1 (4H), LDH-5 (4M), and the three mixed tetramers (LDH-2/3H1M, LDH-3/2H2M, LDH-4/1H3M). These five isoforms are enzymatically similar but show different tissue distribution.
* LDH-1 (4H)—in the heart and in RBC (red blood cells), as well as the brain
* LDH-2 (3H1M)—in the reticuloendothelial system
* LDH-3 (2H2M)—in the lungs
* LDH-4 (1H3M)—in the kidneys, placenta, and pancreas
* LDH-5 (4M)—in the liver and striated muscle, also present in the brain
LDH-2 is usually the predominant form in the serum. An LDH-1 level higher than the LDH-2 level (a "flipped pattern") suggests myocardial infarction (damage to heart tissues releases heart LDH, which is rich in LDH-1, into the bloodstream). The use of this phenomenon to diagnose infarction has been largely superseded by the use of Troponin I or T measurement.
There are two more mammalian LDH subunits that can be included in LDH tetramers: LDHC and LDHBx. LDHC is a testes-specific LDH protein, that is encoded by the LDHC gene. LDHBx is a peroxisome-specific LDH protein. LDHBx is the readthrough-form of LDHB. LDHBx is generated by translation of the LDHB mRNA, but the stop codon is interpreted as an amino acid-encoding codon. In consequence, translation continues to the next stop codon. This leads to the addition of seven amino acid residues to the normal LDH-H protein. The extension contains a peroxisomal targeting signal, so that LDHBx is imported into the peroxisome. | 1 | Biochemistry |
All eukaryotes use G proteins for signaling and have evolved a large diversity of G proteins. For instance, humans encode 18 different G proteins, 5 G proteins, and 12 G proteins. | 1 | Biochemistry |
* In boronic ester homologization an alkyl group shifts from boron in a boronate to carbon:
In this reaction dichloromethyllithium converts the boronic ester into a boronate. A Lewis acid then induces a rearrangement of the alkyl group with displacement of the chlorine group. Finally an organometallic reagent such as a Grignard reagent displaces the second chlorine atom effectively leading to insertion of an RCH group into the C-B bond. Another reaction featuring a boronate alkyl migration is the Petasis reaction. | 0 | Organic Chemistry |
From the preceding discussion, it should be apparent that the decay rate, the fractal dimension and the Lyapunov exponents are all related. The large Lyapunov exponent, for instance, tells us how fast a trajectory in the invariant set will diverge if perturbed. Similarly, the fractal dimension will give us information about the density of orbits in the invariant set. Thus we can see that both will affect the decay rate as captured in the following conjecture for a two-dimensional scattering system:
where D is the information dimension and h and h are the small and large Lyapunov exponents, respectively. For an attractor, and it reduces to the Kaplan–Yorke conjecture. | 7 | Physical Chemistry |
The technology was licensed from DNA Electronics Ltd, developed by Ion Torrent Systems Inc. and was released in February 2010. Ion Torrent have marketed their machine as a rapid, compact and economical sequencer that can be utilized in a large number of laboratories as a bench top machine. Roche's 454 Life Sciences is partnering with DNA Electronics on the development of a long-read, high-density semiconductor sequencing platform using this technology. | 1 | Biochemistry |
A Fischer–Tropsch-type process has also been suggested to have produced a few of the building blocks of DNA and RNA within asteroids. Similarly, the hypothetical abiogenic petroleum formation requires some naturally occurring FT-like processes.
Biological Fischer-Tropsch-type chemistry can be carried out by the enzyme nitrogenase at ambient conditions. | 0 | Organic Chemistry |
An example of an alcoholic glycoside is salicin, which is found in the genus Salix. Salicin is converted in the body into salicylic acid, which is closely related to aspirin and has analgesic, antipyretic, and anti-inflammatory effects. | 0 | Organic Chemistry |
Vervet monkeys (Chlorocebus Pygerythus) are some of the most studied monkeys when it comes to vocalization and alarm calls within the nonhuman primates. They are most known for making alarm calls in the presence of their most common predators (leopards, eagles, and snakes). The alarm calls of the Vervet monkey are considered arbitrary in relation to the predator that it signifies. In the sense that the calls may be distinct to the threat that the monkeys are seeing but arbitrary in that it does not mimic the sounds of the predator. This is like yelling "Danger!" when seeing an angry dog instead of making barking sounds. This type of alarm calls is seen as the earliest example of symbolic communication (the relationship between signifier and signified is arbitrary and purely conventional) in nonhuman primates.
However, there is much debate on whether the vervet monkeys alarm calls are actual "words" in the sense of purposely manipulating sounds to communicate specific meaning or are unintentional sounds that are made when interacting with an outside stimulus. Like small children who cannot communicate words effectively make random noises when being played with or are stimulated by something in their immediate environment. As children grow and begin learning how to communicate the noises, they make are very broad in relation to their environment. They begin to recognize the things in their environment but there more things than known words or noises so a certain sound may reference multiple things. As children get older, they can become more specific about the noises and words made in relation to the things in their environment. It is thought that as Vervet monkeys get older they are able to learn and break the broad categories into more specific sub categories to a specific context.
In an experiment conducted by Dr. Tabitha Price, they used custom software to gather the acoustic sounds of male and female Vervet monkeys from East Africa and male Vervet monkey from South Africa. The point of the experiment was to gather the acoustic sounds of these monkeys when stimulated by the presence of snakes (mainly Python), raptors, terrestrial animals (mostly Leopards), and aggression. Then to determine if the calls could be distinguished with a known context.
The experiment determined that while the Vervet monkeys were able to categorize different predators and members of different social groups, however their ability to communicate specific threats is not proven. The chirps and barks that Vervet monkeys make as an eagle swoops in are the same chirps and barks that are made in moments of high arousal. Similarly, the barks made for leopards are the same that are made during aggressive interactions. The environment that they exist in is too complex for their ability to communicate about everything in their environment specifically..
In an experiment conducted by Dr. Julia Fischer, a drone was flown over Vervet monkeys and recorded the sounds produced. The Vervet monkeys made alarm calls that were almost identical to the eagle calls of East African Vervets. When a sound recording of the drone was played back a few days later to a monkey that was alone and away from the main group it looked up and scanned the sky. Dr. Fischer concluded that Vervet monkeys can be exposed to a new threat once and understand what it means.
It is still debated whether or not Vervet monkeys are actually aware of what the alarm calls mean. One side of the argument is that the monkeys give alarm calls because they are simply excited. The other side of the argument is that the alarm calls create mental representation of predators in the listeners minds. The common middle ground argument is that they give alarm calls because they want others to elicit a certain response, not necessarily because they want the group to think that there is a specific threat near.
Ultimately there is not enough evidence to support whether or not the calls are simply identifying a threat or calling for specific action due to the threat. | 1 | Biochemistry |
The charge transfer coefficient signifies the fraction of the interfacial potential at an electrode-electrolyte interface that helps in lowering the free energy barrier for the electrochemical reaction. The electroactive ion present in the interfacial region experiences the interfacial potential and electrostatic work is done on the ion by a part of the interfacial electric field. It is charge transfer coefficient that signifies this part that is utilized in activating the ion to the top of the free energy barrier. | 7 | Physical Chemistry |
Retinalophototrophs are found across all domains of life but predominantly in the Bacteria and Archaea taxonomic groups. Scientists believe retinalophototroph’s general ecological abundance correlates to horizontal gene transfer since only two genes are required for retinalophototrophy to occur: essentially, one gene for retinal-binding protein synthesis (bop) and one for retinal chromophore synthesis (blh). | 5 | Photochemistry |
Binding curves describe the binding behavior of ligand to a protein. Curves can be characterized by their shape, sigmoidal or hyperbolic, which reflect whether or not the protein exhibits cooperative or noncooperative binding behavior respectively. Typically, the x-axis describes the concentration of ligand and the y-axis describes the fractional saturation of ligands bound to all available binding sites. The Michaelis Menten equation is usually used when determining the shape of the curve. The Michaelis Menten equation is derived based on steady-state conditions and accounts for the enzyme reactions taking place in a solution. However, when the reaction takes place while the enzyme is bound to a substrate, the kinetics play out differently.
Modeling with binding curves are useful when evaluating the binding affinities of oxygen to hemoglobin and myoglobin in the blood. Hemoglobin, which has four heme groups, exhibits cooperative binding. This means that the binding of oxygen to a heme group on hemoglobin induces a favorable conformation change that allows for increased binding favorability of oxygen for the next heme groups. In these circumstances, the binding curve of hemoglobin will be sigmoidal due to its increased binding favorability for oxygen. Since myoglobin has only one heme group, it exhibits noncooperative binding which is hyperbolic on a binding curve. | 1 | Biochemistry |
Most photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide and water using energy from light. However, not all organisms use carbon dioxide as a source of carbon atoms to carry out photosynthesis; photoheterotrophs use organic compounds, rather than carbon dioxide, as a source of carbon.
In plants, algae, and cyanobacteria, photosynthesis releases oxygen. This oxygenic photosynthesis is by far the most common type of photosynthesis used by living organisms. Some shade-loving plants (sciophytes) produce such low levels of oxygen during photosynthesis that they use all of it themselves instead of releasing it to the atmosphere.
Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also many varieties of anoxygenic photosynthesis, used mostly by bacteria, which consume carbon dioxide but do not release oxygen.
Carbon dioxide is converted into sugars in a process called carbon fixation; photosynthesis captures energy from sunlight to convert carbon dioxide into carbohydrates. Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration: while photosynthesis is a process of reduction of carbon dioxide to carbohydrates, cellular respiration is the oxidation of carbohydrates or other nutrients to carbon dioxide. Nutrients used in cellular respiration include carbohydrates, amino acids and fatty acids. These nutrients are oxidized to produce carbon dioxide and water, and to release chemical energy to drive the organism's metabolism.
Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments.
The general equation for photosynthesis as first proposed by Cornelis van Niel is:
Since water is used as the electron donor in oxygenic photosynthesis, the equation for this process is:
This equation emphasizes that water is both a reactant in the light-dependent reaction and a product of the light-independent reaction, but canceling n water molecules from each side gives the net equation:
Other processes substitute other compounds (such as arsenite) for water in the electron-supply role; for example some microbes use sunlight to oxidize arsenite to arsenate: The equation for this reaction is:
: + + → + (used to build other compounds in subsequent reactions)
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
Most organisms that use oxygenic photosynthesis use visible light for the light-dependent reactions, although at least three use shortwave infrared or, more specifically, far-red radiation.
Some organisms employ even more radical variants of photosynthesis. Some archaea use a simpler method that employs a pigment similar to those used for vision in animals. The bacteriorhodopsin changes its configuration in response to sunlight, acting as a proton pump. This produces a proton gradient more directly, which is then converted to chemical energy. The process does not involve carbon dioxide fixation and does not release oxygen, and seems to have evolved separately from the more common types of photosynthesis. | 5 | Photochemistry |
Phosphodiesterase enzymes have been shown to be different in different types of cells, including normal and leukemic lymphocytes and are often targets for pharmacological inhibition due to their unique tissue distribution, structural properties, and functional properties.
Inhibitors of PDE can prolong or enhance the effects of physiological processes mediated by cAMP or cGMP by inhibition of their degradation by PDE.
Sildenafil (Viagra) is an inhibitor of cGMP-specific phosphodiesterase type 5, which enhances the vasodilatory effects of cGMP in the corpus cavernosum and is used to treat erectile dysfunction. Sildenafil is also currently being investigated for its myo- and cardioprotective effects, with particular interest being given to the compound's therapeutic value in the treatment of Duchenne muscular dystrophy and benign prostatic hyperplasia.
Paraxanthine, the main metabolite of caffeine, is another cGMP-specific phosphodiesterase inhibitor which inhibits PDE9, a cGMP preferring phosphodiesterase. PDE9 is expressed as high as PDE5 in the corpus cavernosum. | 1 | Biochemistry |
Electrons that are bound in atoms, molecules and solids each occupy distinct states of well-defined binding energies. When light quanta deliver more than this amount of energy to an individual electron, the electron may be emitted into free space with excess (kinetic) energy that is higher than the electron's binding energy. The distribution of kinetic energies thus reflects the distribution of the binding energies of the electrons in the atomic, molecular or crystalline system: an electron emitted from the state at binding energy is found at kinetic energy . This distribution is one of the main characteristics of the quantum system, and can be used for further studies in quantum chemistry and quantum physics. | 7 | Physical Chemistry |
Normal serum levels of ketone bodies are less than 0.5 mM. Hyperketonemia is conventionally defined as levels in excess of 1 mM. | 1 | Biochemistry |
GnRH is released by the hypothalamus in a pulsatile fashion; this causes the anterior pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH stimulates the testes to produce testosterone, which is metabolized to DHT by the enzyme 5α-reductase.
DHT, and to a significantly smaller extent, testosterone, stimulate prostate cancer cells to grow. Therefore, blocking these androgens can provide powerful treatment for prostate cancer, especially metastatic disease. Normally administered are GnRH analogues, such as leuprorelin or cetrorelix. Although GnRH agonists stimulate the same receptors that GnRH does, since they are present continuously and not in a pulsatile manner, they serve to inhibit the pituitary gland and therefore block the whole chain. However, they initially cause a surge in activity; this is not solely a theoretical risk but may cause the cancer to flare. Flutamide was initially used at the beginning of GnRH agonist therapy to block this surge, and it and other NSAAs continue in this use. In contrast to GnRH agonists, GnRH antagonists don't cause an initial androgen surge, and are gradually replacing GnRH agonists in clinical use.
There have been studies to investigate the benefit of adding an antiandrogen to surgical orchiectomy or its continued use with a GnRH analogue (combined androgen blockade (CAB)). Adding antiandrogens to orchiectomy showed no benefit, while a small benefit was shown with adding antiandrogens to GnRH analogues.
Unfortunately, therapies which lower testosterone levels, such as orchiectomy or GnRH analogue administration, also have significant side effects. Compared to these therapies, treatment with antiandrogens exhibits "fewer hot flashes, less of an effect on libido, less muscle wasting, fewer personality changes, and less bone loss." However, antiandrogen therapy alone is less effective than surgery. Nevertheless, given the advanced age of many with prostate cancer, as well as other features, many men may choose antiandrogen therapy alone for a better quality of life.
Flutamide has been found to be similarly effective in the treatment of prostate cancer to bicalutamide, although indications of inferior efficacy, including greater compensatory increases in testosterone levels and greater reductions in PSA levels with bicalutamide, were observed. The medication, at a dosage of 750 mg/day (250 mg three times daily), has also been found to be equivalent in effectiveness to 250 mg/day oral cyproterone acetate as a monotherapy in the treatment of prostate cancer in a large-scale clinical trial of 310 patients, though its side effect and toxicity profiles (including gynecomastia, diarrhea, nausea, loss of appetite, and liver disturbances) were regarded as considerably worse than those of cyproterone acetate.
A dosage of 750 mg/day flutamide (250 mg/three times a day) is roughly equivalent in terms of effectiveness to 50 mg/day bicalutamide when used as the antiandrogen component in combined androgen blockade in the treatment of advanced prostate cancer.
Flutamide has been used to prevent the effects of the testosterone flare at the start of GnRH agonist therapy in men with prostate cancer.
The combination of flutamide with an estrogen such as ethinylestradiol sulfonate has been used as a form of combined androgen blockade and as an alternative to the combination of flutamide with surgical or medical castration. | 4 | Stereochemistry |
ILs can act as dispersing agents in paints to enhance finish, appearance and drying properties. ILs are used for dispersing nanomaterials at IOLITEC. | 7 | Physical Chemistry |
The pharmaceutical industry constitutes the most important customer base for the fine chemical industry (see Table 4). The largest companies are Pfizer, USA; Roche, Switzerland, GlaxoSmithKline, UK; Sanofi Aventis, France, and Novartis, Switzerland. All are active in R&D, manufacturing and marketing. Pharmaceuticals containing more than 2000 different active ingredients are in commerce today; a sizable number of them are sourced from the fine chemical industry. The industry also has a track record of above-average growth.
The fine chemical industry has a keen interest in the top-selling or "blockbuster drugs", i.e. those with worldwide annual sales in excess of $1 billion. Their number has increased steadily, from 27 in 1999 to 51 in 2001, 76 in 2003, and then levelled off.
Sales of the top 20 blockbuster drugs are reported in Table 6. The APIs of 12 of them are "small" (LMW) molecules. Averaging a MW of 477, they have quite complex structures. They typically show three cyclic moieties. 10 of them exhibit at least one N-heterocyclic moiety. Five of the top 10, up from none in 2005, are biopharmaceuticals. The largest-selling non-proprietary drugs are paracetamol, omeprazole, ethinylestradiol, amoxicillin, pyridoxine, and ascorbic acid.
The innovator pharma companies require mainly custom manufacturing services for their proprietary drug substances. The demand is driven primarily by the number of new drug launches, the volume requirements and the industrys "make or buy" strategy. A summary of the pros and cons for outsourcing from the pharma industrys perspective is given in Table 7. As extended studies at the Stern Business School of the New York City University have shown, financial considerations clearly favor the "buy" option.
Teva and Sandoz are by far the largest generics companies (see also chapter 6.3.2). They differ from their competitors not only in sales revenues but also because they are strongly backwards integrated and have proprietary drugs in their portfolios. They also vie for the promising biosimilars market.
Several thousand small or virtual pharma companies focus on R&D. albeit on just a few lead compounds. They typically originate mostly from academia. Therefore, their R&D strategy is more focused on the elucidation of the biological roots of diseases rather than developing synthesis methods. | 0 | Organic Chemistry |
p75NTR is a member of the tumor necrosis factor receptor superfamily. p75NTR/LNGFR was the first member of this large family of receptors to be characterized, that now contains about 25 receptors, including tumor necrosis factor 1 (TNFR1) and TNFR2, Fas, RANK, and CD40.
All members of the TNFR superfamily contain structurally related cysteine-rich modules in their ECDs. p75NTR is an unusual member of this family due to its propensity to dimerize rather than trimerize, because of its ability to act as a tyrosine kinase co-receptor, and because the neurotrophins are structurally unrelated to the ligands, which typically bind TNFR family members. Indeed, with the exception of p75NTR, essentially all members of the TNFR family preferentially bind structurally related trimeric Type II transmembrane ligands, members of the TNF ligand superfamily. | 1 | Biochemistry |
Many women of sub-Saharan Africa choose to foster their children to infertile women. IVF enables these infertile women to have their own children, which imposes new ideals to a culture in which fostering children is seen as both natural and culturally important. Many infertile women are able to earn more respect in their society by taking care of the children of other mothers, and this may be lost if they choose to use IVF instead. As IVF is seen as unnatural, it may even hinder their societal position as opposed to making them equal with fertile women. It is also economically advantageous for infertile women to raise foster children as it gives these children greater ability to access resources that are important for their development and also aids the development of their society at large. If IVF becomes more popular without the birth rate decreasing, there could be more large family homes with fewer options to send their newborn children. This could result in an increase of orphaned children and/or a decrease in resources for the children of large families. This would ultimately stifle the childrens and the communitys growth.
In the US, the pineapple has emerged as a symbol of IVF users, possibly because some people thought, without scientific evidence, that eating pineapple might slightly increase the success rate for the procedure. | 1 | Biochemistry |
The surface processes that HeSE can measure can be broadly divided into elastic, quasielastic and inelastic processes. Measurements in which the predominant signal is elastically scattered include standard helium diffraction and the measurement of selective adsorption resonances. Quasielastic measurements generally correspond to measurements of microscopic surface diffusion in which the Doppler-like energy gain and loss of the helium atoms is small compared to the beam energy. More strongly inelastic measurements can provide information about energy loss channels on the surface such as surface phonons. | 7 | Physical Chemistry |
Although RNA enzymes were discovered before DNA enzymes, the latter have some distinct advantages. DNA is more cost-effective, and DNA can be made with longer sequence length and can be made with higher purity in solid-phase synthesis. Several studies have shown the usage of DNAzymes to inhibit influenza A and B virus replication in host cells. DNAzymes have also been shown to inhibit the replication of SARS coronavirus (SARS-CoV), Respiratory syncytial virus (RSV), human rhinovirus 14 and HCV | 7 | Physical Chemistry |
Fifty-six new copper discoveries have been made during the three decades 1975–2005. World discoveries of new copper deposits are said to have peaked in 1996. However, according to the US Geological Survey (USGS), remaining world copper reserves have more than doubled since then, from 310 million metric tons in 1996 to 890 million metric tons in 2022. | 8 | Metallurgy |
Non-essential trace elements include silver (Ag), cadmium (Cd), mercury (Hg), and lead (Pb). They have no known biological function in mammals, with toxic effects even at low concentration.
The structural components of cells and tissues that are required in the diet in gram quantities daily are known as bulk elements. | 9 | Geochemistry |
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.
The anhydrous form is important commercially. It has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature. | 0 | Organic Chemistry |
One common criticism of the hyperconjugation theory is that it fails to explain why the anomeric effect is not observed when substituted tetrahydropyran molecules are placed in polar solvents, and the equatorial position is once again preferred. It has been shown, however, that hyperconjugation does depend on the solvent in the system. Each of the substituted systems described above were tested in the gas phase (i.e. with no solvent) and in aqueous solution (i.e. polar solvent). When X=F, the anomeric effect was observed in both media, and the axial position was always preferred. This is attributed to hyperconjugation. When X=OH or CN, the anomeric effect was seen in the gas phase, when the axial position was preferred. However, in aqueous solutions, both substituents preferred the equatorial position. This is attributed to the fact that there are more electrostatic repulsions with the axial positioned substituent and the polar solvent, causing the equatorial position to be preferred. When X=NH, again, no anomeric effect was observed and the equatorial position was always preferred. | 7 | Physical Chemistry |
Isaac Asimov, in a 1963 humorous essay entitled "You, too, can speak Gaelic", reprinted in the anthology Adding a Dimension among others, traces the etymology of each component of the chemical name "para-di-methyl-amino-benz-alde-hyde" (e.g. the syllable "-benz-" ultimately derives from the Arabic lubān jāwī (لبان جاوي, "frankincense from Java"). Asimov points out that the name can be pronounced to the tune of the familiar jig "The Irish Washerwoman", and relates an anecdote in which a receptionist of Irish descent, hearing him singing the syllables thus, mistook them for the original Gaelic words to the jig. This essay inspired Jack Carrolls 1963 filk song "The Chemists Drinking Song," (NESFA Hymnal Vol. 2 2nd ed. p. 65) set to the tune of that jig, which begins "Paradimethylaminobenzaldehyde, / Sodium citrate, ammonium cyanide, / ..." | 3 | Analytical Chemistry |
In a cascade mediated by a GPCR known as β adrenoceptor, activated by catecholamines (notably norepinephrine), PKA gets activated and phosphorylates numerous targets, namely: L-type calcium channels, phospholamban, troponin I, myosin binding protein C, and potassium channels. This increases inotropy as well as lusitropy, increasing contraction force as well as enabling the muscles to relax faster. | 1 | Biochemistry |
Kirsch and co-workers were able to hydroxylate keto compounds with IBX in α-position under mild conditions. This method could be extended to β-keto esters. | 0 | Organic Chemistry |
Peroxisome proliferator activated receptor gamma 1-alpha coactivator (PGC-1 alpha) is a specific myokine since it stimulates satellite cells, but stimulates M1 and M2 macrophages; M1 macrophages release interleukin 6 (IL-6), Insulin growth factor type 1 (IGF-1) and vascular endothelial growth factor (VEGF), while M2 macrophages mainly secrete IGF-1, VEGF and monocyte chemoattractant protein 1 (MCP-1)) and all this process the muscle becomes muscle hypertrophy.
Macrophages M2 stimulate satellite cells for proliferation and growth but M1 stimulates blood vessels and produces pro-inflammatory cytokines only M2 produces anti-inflammatory in muscles. | 1 | Biochemistry |
RNA interference (RNAi) methods can be used to transiently silence or knockdown gene expression using ~20 base-pair double-stranded RNA typically delivered by transfection of synthetic ~20-mer short-interfering RNA molecules (siRNAs) or by virally encoded short-hairpin RNAs (shRNAs). RNAi screens, typically performed in cell culture-based assays or experimental organisms (such as C. elegans) can be used to systematically disrupt nearly every gene in a genome or subsets of genes (sub-genomes); possible functions of disrupted genes can be assigned based on observed phenotypes. | 1 | Biochemistry |
Most processed polymer mixes consist of a dispersed phase in a more continuous matrix of the other component. The formation, size, and concentration of this disperse phase are typically optimized for specific mechanical properties. If the morphology is not stabilized, the dispersed phase may coalesce under heat or stress from the environment or further processing. This coalescence may result in diminished properties (brittleness and discoloration) due to the induced phase separation. These morphologies can be stabilized by sufficient interfacial adhesion or lowered interfacial tension between the two phases.
A common technique involves functionalizing one monomer. For example, Nylon-rubber bands are polymerized with functionalized rubber to produce graft or block copolymers. The added structures make it no longer favorable to coalesce and/or increase the steric hindrance in the interfacial area where phase separation would occur. | 7 | Physical Chemistry |
She was born in Iași, in the Moldavia region of Romania; her parents were Constantin and Smaranda Ripan, both originally from Huși. She attended the local girl's high school, after which she enrolled in the Faculty of Science of the University of Iași, graduating in 1919. For her graduate studies she went to the University of Cluj in Transylvania, obtaining her PhD in 1922 under the direction of Gheorghe Spacu, with thesis "Double amines corresponding to double sulphates in the magnesium series". She is recognized as the first woman from Romania to earn a Ph.D. in the chemical sciences.
After obtaining in 1930 her Habilitation and the title of Docent, Ripan became an associate professor of analytic chemistry at the Faculty of Science of the University of Cluj. During World War II, when Cluj passed under Hungarian administration under the terms of the Second Vienna Award, the university moved to Timișoara. In July 1942 (by which time she had 53 publications), she was promoted to full professor through a decree published in Monitorul Oficial. After the war she returned to Cluj, where she served as Dean of the Faculty of Chemistry from 1948 to 1952.
In 1948, Ripan was elected titular member of the Romanian Academy, thus becoming the first woman to be inducted in that academy. In 1951 she founded the Institute of Chemistry, consisting of three sections (inorganic chemistry, organic chemistry, and physical chemistry); she headed the institute until 1970. From 1951 to 1955 she served as Rector of the University of Cluj, the first woman to hold a rectorship in Romania. In 1952 she was elected deputy to the Great National Assembly for the Cluj-Nord constituency of the Cluj Region, serving in this capacity until 1957. In 1963 she was awarded an honorary degree by the Nicolaus Copernicus University in Toruń.
Ripan worked in the domain of complex combinations and their use in analytical chemistry. She discovered and studied new classes of complex combinations used in the determination of metals, as well as new methods of assay for thallium, lead, tellurium, selenic acid, and selenocyanates. One of her students at the University of Cluj was Ionel Haiduc (a future President of the Romanian Academy), who wrote an undergraduate thesis on polyoxometalates under her direction in 1959.
She died in Cluj-Napoca in 1972, and is buried at the city's Hajongard Cemetery. The "Raluca Ripan Institute for Research in Chemistry" is now part of Babeș-Bolyai University. A vocational high school in Cluj-Napoca also bears her name, as does a national Chemistry competition for high school students. | 3 | Analytical Chemistry |
Alkyl sulfonates are esters of alkane sulfonic acids with the general formula R-SO-O-R'. They act as alkylating agents, some of them are used as alkylating antineoplastic agents in the treatment of cancer, e.g. Busulfan. | 0 | Organic Chemistry |
It is a method used to obtain aluminium of very high purity. The metal obtained in the Hall–Héroult process is about 99.5% pure, and for most purposes it is taken as pure metal.
However, further purification of aluminium can be carried out by the Hoopes process. This is an electrolytic process. | 8 | Metallurgy |
Oxocarbenium ions have been utilized in total synthesis on several occasions. A major subunit of (+)-clavosolide was synthesized with a reduction of a six-membered oxocarbenium ring. All the large substituents were found in an equatorial position, and the transformation went through the chair transition state, as predicted.
A second example is seen in the key step of the synthesis of (−)-neopeltolide, which uses another six-membered oxocarbenium ring reduction for a diastereoselective hydride addition. | 0 | Organic Chemistry |
The primary tool for small-scale cupellation was the cupel. Cupels were manufactured in a careful manner. They used to be small vessels shaped in the form of an inverted truncated cone, made of bone ashes. According to Georg Agricola, the best material was obtained from burned antlers of deer, although fish spines could also work. Ashes have to be ground into a fine and homogeneous powder and mixed with some sticky substance to mould the cupels. Moulds were made out of copper with no bottoms, so that the cupels could be taken off. A shallow depression in the centre of the cupel was made with a rounded pestle. Cupel sizes depend on the amount of material to be assayed. This same shape has been maintained until the present.
Archaeological investigations as well as archaeometallurgical analysis and written texts from the Renaissance have demonstrated the existence of different materials for their manufacture; they could be made also with mixtures of bones and wood ashes, of poor quality, or moulded with a mixture of this kind in the bottom with an upper layer of bone ashes. Different recipes depend on the expertise of the assayer or on the special purpose for which it was made (assays for minting, jewelry, testing purity of recycled material or coins). Archaeological evidence shows that at the beginnings of small-scale cupellation, potsherds or clay cupels were used. | 8 | Metallurgy |
Many of the crystallographic point groups share the same internal structure. For example, the point groups , 2, and m contain different geometric symmetry operations, (inversion, rotation, and reflection, respectively) but all share the structure of the cyclic group C. All isomorphic groups are of the same order, but not all groups of the same order are isomorphic. The point groups which are isomorphic are shown in the following table:
This table makes use of cyclic groups (C, C, C, C, C), dihedral groups (D, D, D, D), one of the alternating groups (A), and one of the symmetric groups (S). Here the symbol " × " indicates a direct product. | 3 | Analytical Chemistry |
TRPA1 (Transient Receptor Potential-Ankyrin 1) ion channel expressed on nociceptors (especially trigeminal) has been implicated as the site of action for CS gas in rodent models.
Although described as a non-lethal weapon for crowd control, studies have raised doubts about this classification. CS can cause severe pulmonary damage and can also significantly damage the heart and liver.
On 28 September 2000, Prof. Dr. Uwe Heinrich released a study commissioned by John C. Danforth, of the United States Office of Special Counsel, to investigate the use of CS by the FBI at the Branch Davidians' Mount Carmel compound. He said no human deaths had been reported, but concluded that the lethality of CS used would have been determined mainly by two factors: whether gas masks were used and whether the occupants were trapped in a room. He suggests that if no gas masks were used and the occupants were trapped, then, "there is a distinct possibility that this kind of CS exposure can significantly contribute to or even cause lethal effects".
CS gas can have a clastogenic effect (abnormal chromosome change) on mammalian cells, but no studies have linked it to miscarriages or stillbirths. In Egypt, CS gas was reported to be the cause of death of several protesters in Mohamed Mahmoud Street near Tahrir square during the November 2011 protests. The solvent in which CS is dissolved, methyl isobutyl ketone (MIBK), is classified as harmful by inhalation; irritating to the eyes and respiratory system; and repeated exposure may cause skin dryness or cracking. | 1 | Biochemistry |
Antibody Solutions was founded in 1995 by current president, John Kenney, PhD, Judith Lynch-Kenney, and Dennis and Bette Gould. Dr. Kenney previously managed the monoclonal antibody (MAb) development laboratory for Syntex Research (Roche) in Palo Alto, while Gould managed the MAb production facility for Syva Diagnostics. Gould left Antibody Solutions in 1997, eventually becoming a vice president for Sepragen Corporation. Kenney and Gould were assisted in the startup of the company by Barry Bredt, who had the foresight to acquire the domain name, [https://www.antibody.com www.antibody.com], for the company. Bredt later became director of the University of California at San Francisco’s General Clinical Research Center, and was a pioneer of the HIV/AIDS Diagnostics EasyCD4; he died on April 8, 2007.
Antibody Solutions was incorporated in 1998 with Dr. Kenney as president and Judith Lynch-Kenney as chief financial officer. One of the first independent antibody discovery companies, the firm focused on custom antibody discovery for therapeutics, diagnostics and critical reagents. The company pioneered the use of bioreactors in antibody research by becoming the first CRO to produce antibodies in CELLine flasks in 2000.
From 2004 to 2011, Antibody Solutions was headquartered in Mountain View, a short distance from Shoreline Park, Moffett Field and the Googleplex. In 2011, the company moved to new facilities in Sunnyvale. It moved to its current 33,300-square-foot location at 3033 Scott Blvd. in Santa Clara near the San Tomas Expressway in mid-2019. A grand opening for the Scott Blvd. facility was held on January 30, 2020, to coincide with the company's Silver Anniversary. | 1 | Biochemistry |
In ammoxidation, a hydrocarbon is partially oxidized in the presence of ammonia. This conversion is practiced on a large scale for acrylonitrile:
In the production of acrylonitrile, a side product is acetonitrile. On an industrial scale, several derivatives of benzonitrile, phthalonitrile, as well as Isobutyronitrile are prepared by ammoxidation. The process is catalysed by metal oxides and is assumed to proceed via the imine. | 0 | Organic Chemistry |
An excimer lamp (or excilamp) is a source of ultraviolet light based on spontaneous emission of excimer (exciplex) molecules. | 5 | Photochemistry |
* Physisorption is a general phenomenon and occurs in any solid/fluid or solid/gas system. Chemisorption is characterized by chemical specificity.
* In physisorption, perturbation of the electronic states of adsorbent and adsorbate is minimal. The adsorption forces include London Forces, dipole-dipole attractions, dipole-induced attraction and "hydrogen bonding." For chemisorption, changes in the electronic states may be detectable by suitable physical means, in other words, chemical bonding.
* Typical binding energy of physisorption is about 10–300 meV and non-localized. Chemisorption usually forms bonding with energy of 1–10 eV and localized.
* The elementary step in physisorption from a gas phase does not involve an activation energy. Chemisorption often involves an activation energy.
* For physisorption gas phase molecules, adsorbates, form multilayer adsorption unless physical barriers, such as porosity, interfere. In chemisorption, molecules are adsorbed on the surface by valence bonds and only form monolayer adsorption.
* A direct transition from physisorption to chemisorption has been observed by attaching a CO molecule to the tip of an atomic force microscope and measuring its interaction with a single iron atom. This effect was observed in the late 1960s for benzene from field emission as reported by Condon and ESR measurements as reported by Moyes and Wells.
* Another way of looking at this is that chemisorption alters the of the electrons in the adsorbate molecule (by the process of chemical reaction) but physisorption does not. | 7 | Physical Chemistry |
Carcinogens are known to cause a number of DNA lesions, such as single-strand breaks, double- strand breaks, and covalently bound chemical DNA adducts. Tobacco products are one of the most prevalent cancer-causing agents of today. Other DNA damaging, cancer-causing agents include asbestos, which can cause damage through physical interaction with DNA or by indirectly setting off a reactive oxygen species, excessive nickel exposure, which can repress the DNA damage-repair pathways, aflatoxins, which are found in food, and many more. | 1 | Biochemistry |
In 1737 Andrew Rodger, a farmer on the estate of Cavers in Roxburghshire, developed a winnowing machine for corn, called a Fanner. These were successful and the family sold them throughout Scotland for many years. Some Scottish Presbyterian ministers saw the fanners as sins against God, for the wind was a thing specially made by him and an artificial wind was a daring and impious attempt to usurp what belonged to God alone. As the Industrial Revolution progressed, the winnowing process was mechanized by the invention of additional winnowing machines, such as fanning mills. | 3 | Analytical Chemistry |
Ethyl chloroformate is a highly toxic, flammable, corrosive substance. It causes severe burns when comes in contact with eyes and/or skin, can be harmful if swallowed or inhaled. | 0 | Organic Chemistry |
Digestion is a complex process controlled by several factors. pH plays a crucial role in a normally functioning digestive tract. In the mouth, pharynx and esophagus, pH is typically about 6.8, very weakly acidic. Saliva controls pH in this region of the digestive tract. Salivary amylase is contained in saliva and starts the breakdown of carbohydrates into monosaccharides. Most digestive enzymes are sensitive to pH and will denature in a high or low pH environment.
The stomach's high acidity inhibits the breakdown of carbohydrates within it. This acidity confers two benefits: it denatures proteins for further digestion in the small intestines, and provides non-specific immunity, damaging or eliminating various pathogens.
In the small intestines, the duodenum provides critical pH balancing to activate digestive enzymes. The liver secretes bile into the duodenum to neutralize the acidic conditions from the stomach, and the pancreatic duct empties into the duodenum, adding bicarbonate to neutralize the acidic chyme, thus creating a neutral environment. The mucosal tissue of the small intestines is alkaline with a pH of about 8.5. | 1 | Biochemistry |
Over the decades that pheromone pest programs have been used several disadvantages have been argued when compared to the use of conventional pesticides. Most pheromones target a single species, so a specific mating disruption formulation controls only the species that uses that pheromone blend; whereas pesticides usually kill indiscriminately a plethora of species, including multiple species with a single application. Some synthetic pheromones have high developmental and production costs, causing the mating disruption technique to be too costly to be adopted by conventional commercial growers. Furthermore most commercial pheromone mating disruption formulations must be applied by hand, which can be an expensive and time consuming. Novel pheromone formulations recently developed to be mechanically applied provide long lasting mating disruption effects (e.g., depending on the target pest a single application of SPLAT controls the target pest for a complete reproductive cycle, or for the entire season. | 1 | Biochemistry |
Globally, seagrass has been declining rapidly. It is estimated that 21% of the 71 known seagrass species have decreasing population trends and 11% of those species have been designated as threatened on the ICUN Red List. Hypoxia that leads to eutrophication caused form ocean deoxygenation is one of the main underlying factors of these die-offs. Eutrophication causes enhanced nutrient enrichment which can result in seagrass productivity, but with continual nutrient enrichment in seagrass meadows, it can cause excessive growth of microalgae, epiphytes and phytoplankton resulting in hypoxic conditions.
Seagrass is both a source and a sink for oxygen in the surrounding water column and sediments. At night, the inner part of seagrass oxygen pressure is linearly related to the oxygen concentration in the water column, so low water column oxygen concentrations often result in hypoxic seagrass tissues, which can eventually kill off the seagrass. Normally, seagrass sediments must supply oxygen to the below-ground tissue through either photosynthesis or by diffusing oxygen from the water column through leaves to rhizomes and roots. However, with the change in seagrass oxygen balances, it can often result in hypoxic seagrass tissues. Seagrass exposed to this hypoxic water column show increased respiration, reduced rates of photosynthesis, smaller leaves, and reduced number of leaves per shoot. This causes insufficient supply of oxygen to the belowground tissues for aerobic respiration, so seagrass must rely on the less-efficient anaerobic respiration. Seagrass die-offs create a positive feedback loop in which the mortality events cause more death as higher oxygen demands are created when dead plant material decomposes.
Because hypoxia increases the invasion of sulfides in seagrass, this negatively affects seagrass through photosynthesis, metabolism and growth. Generally, seagrass is able to combat the sulfides by supplying enough oxygen to the roots. However, deoxygenation causes the seagrass to be unable to supply this oxygen, thus killing it off.
Deoxygenation reduces the diversity of organisms inhabiting seagrass beds by eliminating species that cannot tolerate the low oxygen conditions. Indirectly, the loss and degradation of seagrass threatens numerous species that rely on seagrass for either shelter or food. The loss of seagrass also effects the physical characteristics and resilience of seagrass ecosystems. Seagrass beds provide nursery grounds and habitat to many harvested commercial, recreational, and subsistence fish and shellfish. In many tropical regions, local people are dependent on seagrass associated fisheries as a source of food and income.
Seagrass also provides many ecosystem services including water purification, coastal protection, erosion control, sequestration and delivery of trophic subsidies to adjacent marine and terrestrial habitats. Continued deoxygenation causes the effects of hypoxia to be compounded by climate change which will increase the decline in seagrass populations. | 9 | Geochemistry |
In medicine, a biomarker is a measurable indicator of the severity or presence of some disease state. It may be defined as a "cellular, biochemical or molecular alteration in cells, tissues or fluids that can be measured and evaluated to indicate normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention." More generally a biomarker is anything that can be used as an indicator of a particular disease state or some other physiological state of an organism. According to the WHO, the indicator may be chemical, physical, or biological in nature - and the measurement may be functional, physiological, biochemical, cellular, or molecular.
A biomarker can be a substance that is introduced into an organism as a means to examine organ function or other aspects of health. For example, rubidium chloride is used in isotopic labeling to evaluate perfusion of heart muscle. It can also be a substance whose detection indicates a particular disease state, for example, the presence of an antibody may indicate an infection. More specifically, a biomarker indicates a change in expression or state of a protein that correlates with the risk or progression of a disease, or with the susceptibility of the disease to a given treatment. Biomarkers can be characteristic biological properties or molecules that can be detected and measured in parts of the body like the blood or tissue. They may indicate either normal or diseased processes in the body. Biomarkers can be specific cells, molecules, or genes, gene products, enzymes, or hormones. Complex organ functions or general characteristic changes in biological structures can also serve as biomarkers. Although the term biomarker is relatively new, biomarkers have been used in pre-clinical research and clinical diagnosis for a considerable time. For example, body temperature is a well-known biomarker for fever. Blood pressure is used to determine the risk of stroke. It is also widely known that cholesterol values are a biomarker and risk indicator for coronary and vascular disease, and that C-reactive protein (CRP) is a marker for inflammation.
Biomarkers are useful in a number of ways, including measuring the progress of disease, evaluating the most effective therapeutic regimes for a particular cancer type, and establishing long-term susceptibility to cancer or its recurrence. Biomarkers characterize disease progression starting from the earliest natural history of the disease. Biomarkers assess disease susceptibility and severity, which allows one to predict outcomes, determine interventions and evaluate therapeutic responses. From a forensics and epidemiologic perspective, biomarkers offer unique insight about the relationships between environmental risk factors. The parameter can be chemical, physical or biological. In molecular terms biomarker is "the subset of markers that might be discovered using genomics, proteomics technologies or imaging technologies. Biomarkers play major roles in medicinal biology. Biomarkers help in early diagnosis, disease prevention, drug target identification, drug response etc. Several biomarkers have been identified for many diseases such as serum LDL for cholesterol, blood pressure, and P53 gene and MMPs as tumor markers for cancer. | 1 | Biochemistry |
Steroid 21-hydroxylase is localized in microsomes of endoplasmic reticulum membranes within adrenal cortex. It is one of three microsomal steroidogenic cytochrome P450 enzymes, the others being steroid 17-hydroxylase and aromatase.
Unlike other enzymes of the cytochrome P450 superfamily of enzymes that are expressed in multiple tissues, with most abundant expression in the liver, in adult humans steroid 21-hydroxylase, along with steroid 11β-hydroxylase and aldosterone synthase, is almost exclusively expressed in the adrenal gland.
the main subcellular location for the encoded protein in human cells is not known, and is pending cell analysis. | 1 | Biochemistry |
The thermic effect of food is increased by both aerobic training of sufficient duration and intensity or by anaerobic weight training. However, the increase is marginal, amounting to 7-8 calories per hour. The primary determinants of daily TEF are the total caloric content of the meals and the macronutrient composition of the meals ingested. Meal frequency has little to no effect on TEF; assuming total calorie intake for the days are equivalent.
Although some believe that TEF is reduced in obesity, discrepant results and inconsistent research methods have failed to validate such claims.
The mechanism of TEF is unknown. TEF has been described as the energy used in the distribution of nutrients and metabolic processes in the liver, but a hepatectomized animal shows no signs of TEF and intravenous injection of amino acids results in an effect equal to that of oral ingestion of the same amino acids. | 1 | Biochemistry |
Epi-lipoxins are trihydroxy (i.e. containing 3 hydroxyl residues) metabolites of arachidonic acid. They are 15R-epimers of their lipoxin counterparts; that is, the epi-lipoxins, 15-epi-lipoxin A4 (15-epi-LxA4) and 15-epi-lipoxin B4 (15-epi-LXB4), differ from their respective lipoxin A4 (LxA4) and lipoxin B4 (LxB4) epimers in that their 15-hydroxy residue has R rather than S chirality. Formulae for these lipoxins (Lx) are:
*LxA4: 5S,6R,15S-trihydroxy-7E,9E,11Z,13E-ETE
*LxB4: 5S,14R,15S-trihydroxy-6E,8Z,10E,12E-ETE
*15-epi-LxA4: 5S,6R,15R-trihydroxy-7E,9E,11Z,13E-eicosatetraenoic acid
*15-epi-LxB4: 5S,14R,15R-trihydroxy-6E,8Z,10E,12E-eicosatrienoic acid
The two-epi-Lxs as well as the two lxs are nonclassic eicosanoids that, like other members of the specialized pro-resolving mediators class of autocoids, form during and act to resolve inflammatory responses. Synthesis of the lipoxins typically involves a lipoxygenase enzyme which acts to add a 15S-hydroxyl residue to the lipoxin precursor, arachidonic acid, whereas synthesis of the epi-lipoxins involves aspirin-pretreated cyclooxygenase 2 or a cytochrome P450 enzyme which adds a 15R-hydroxyl residue to arachidonic acid. In acknowledgement of the role played by aspirin-treated cyclooxygenase 2 in forming these products, the epi-lipoxins are sometimes termed ATL which stands for Aspirin-Triggered Lipoxins.
The counter-regulatory role of the epi-lipoxins in serving as stop signals for diverse inflammation responses is detailed at the lipoxin site. | 1 | Biochemistry |
In chemistry, a resorcinarene (also resorcarene or calix[4]resorcinarene) is a macrocycle, or a cyclic oligomer, based on the condensation of resorcinol (1,3-dihydroxybenzene) and an aldehyde. Resorcinarenes are a type of calixarene. Other types of resorcinarenes include the related pyrogallolarenes and octahydroxypyridines, derived from pyrogallol and 2,6-dihydroxypyridine, respectively.
Resorcinarenes interact with other molecules forming a host–guest complex. Resorcinarenes and pyrogallolarenes self-assemble into larger supramolecular structures. Both in the crystalline state and in organic solvents, six resorcinarene molecules are known to form hexamers with an internal volume of around one cubic nanometer (nanocapsules) and shapes similar to the Archimedean solids. Hydrogen bonds appear to hold the assembly together. A number of solvent or other molecules reside inside. The resorcinarene is also the basic structural unit for other molecular recognition scaffolds, typically formed by bridging the phenolic oxygens with alkyl or aromatic spacers. A number of molecular structures are based on this macrocycle, namely cavitands and carcerands. | 6 | Supramolecular Chemistry |
In host-guest chemistry, cucurbiturils are macrocyclic molecules made of glycoluril () monomers linked by methylene bridges (). The oxygen atoms are located along the edges of the band and are tilted inwards, forming a partly enclosed cavity (cavitand). The name is derived from the resemblance of this molecule with a pumpkin of the family of Cucurbitaceae.
Cucurbiturils are commonly written as cucurbit[n]uril, where n is the number of glycoluril units. Two common abbreviations are CB[n], or simply CBn.
These compounds are particularly interesting to chemists because they are suitable hosts for an array of neutral and cationic species. The binding mode is thought to occur through hydrophobic interactions, and, in the case of cationic guests, through cation-dipole interactions as well. The dimensions of cucurbiturils are generally on the ~10 Å size scale. For instance, the cavity of cucurbit[6]uril has a height ~9.1 Å, an outer diameter ~5.8 Å, and an inner diameter ~3.9 Å.
Cucurbiturils were first synthesized in 1905 by Robert Behrend, by condensing glycoluril with formaldehyde, but their structure was not elucidated until 1981. The field expanded as CB5, CB7, and CB8 were discovered and isolated by Kim Kimoon in the year 2000. To date cucurbiturils composed of 5, 6, 7, 8, 10, and 14 repeat units have all been isolated, which have internal cavity volumes of 82, 164, 279, 479, and 870 Å respectively. A cucurbituril composed of 9 repeat units has yet to be isolated (as of 2009). Other common molecular capsules that share a similar molecular shape with cucurbiturils include cyclodextrins, calixarenes, and pillararenes. | 6 | Supramolecular Chemistry |
Phosphochloridites are precursors to phosphate esters:
:(RO)P(O)Cl + ROH → (RO)(RO)P(O) + HCl
Other nucleophiles have been employed, such as azide. | 0 | Organic Chemistry |
In aquatic organisms the most common form of nitrogen waste is ammonia, whereas land-dwelling organisms convert the toxic ammonia to either urea or uric acid. Urea is found in the urine of mammals and amphibians, as well as some fish. Birds and saurian reptiles have a different form of nitrogen metabolism that requires less water, and leads to nitrogen excretion in the form of uric acid. Tadpoles excrete ammonia, but shift to urea production during metamorphosis. Despite the generalization above, the urea pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, invertebrates, insects, plants, yeast, fungi, and even microorganisms. | 0 | Organic Chemistry |
Two or more equilibria can exist at the same time. When this is so, equilibrium constants can be ascribed to individual equilibria, but they are not always unique. For example, three equilibrium constants can be defined for a dibasic acid, HA.
:A + H HA;
:HA + H HA;
:A + 2 H HA;
The three constants are not independent of each other and it is easy to see that . The constants K and K are stepwise constants and β is an example of an overall constant. | 7 | Physical Chemistry |
The other types of algae are diatoms and dinoflagellates, found primarily in marine environments, such as ocean coastlines or bays, where they can also form algal blooms. Coastal HABs are a natural phenomenon, although in many instances, particularly when they form close to coastlines or in estuaries, it has been shown that they are exacerbated by human-induced eutrophication and/or climate change. They can occur when warmer water, salinity, and nutrients reach certain levels, which then stimulates their growth. Most HAB algae are dinoflagellates. They are visible in water at a concentration of 1,000 algae cells/ml, while in dense blooms they can measure over 200,000/ml.
Diatoms produce domoic acid, another neurotoxin, which can cause seizures in higher vertebrates and birds as it concentrates up the food chain. Domoic acid readily accumulates in the bodies of shellfish, sardines, and anchovies, which if then eaten by sea lions, otters, cetaceans, birds or people, can affect the nervous system causing serious injury or death. In the summer of 2015, the state governments closed important shellfish fisheries in Washington, Oregon and California because of high concentrations of domoic acid in shellfish.
In the marine environment, single-celled, microscopic, plant-like organisms naturally occur in the well-lit surface layer of any body of water. These organisms, referred to as phytoplankton or microalgae, form the base of the food web upon which nearly all other marine organisms depend. Of the 5000+ species of marine phytoplankton that exist worldwide, about 2% are known to be harmful or toxic. Blooms of harmful algae can have large and varied impacts on marine ecosystems, depending on the species involved, the environment where they are found, and the mechanism by which they exert negative effects. | 3 | Analytical Chemistry |
In the field of condensed matter physics, microwave spectroscopy is used to detect dynamic phenomena of either charges or spins at GHz frequencies (corresponding to nanosecond time scales) and energy scales in the µeV regime. Matching to these energy scales, microwave spectroscopy on solids is often performed as a function of temperature (down to cryogenic regimes of a few K or even lower) and/or magnetic field (with fields up to several T).
Spectroscopy traditionally considers the frequency-dependent response of materials, and in the study of dielectrics microwave spectroscopy often covers a large frequency range. In contrast, for conductive samples as well as for magnetic resonance, experiments at a fixed frequency are common (using a highly sensitive microwave resonator), but frequency-dependent measurements are also possible. | 7 | Physical Chemistry |
While this polymerization technique did not typically gain fame and popularity until 2010, it was also reported by Aso and Tagami in 1969. In general, LAP involves the usage of a strong nucleophile to initiate polymerization in addition to the employment of an electrophile as a terminator to endcap the polymer chain. In Tagamis article, PPA was prepared by utilizing tert'-butyllithium as an initiator and acetic anhydride as a terminator. However, the drawbacks faced when utilizing LCP (low polydispersity index (PDI), low yield, and no control over molecular weight) were also encountered in this polymerization technique. | 7 | Physical Chemistry |
BBS has many uses because it is isotonic and has a strong bactericidal effect. It can be used to dilute substances and has applications in coating procedures. Additives such as Polysorbate 20 and milk powder can be used to add to BBS's functionality as a washing buffer or blocking buffer. | 1 | Biochemistry |
Enzymatic browning is one of the most important reactions that takes place in most fruits and vegetables as well as in seafood. These processes affect the taste, color, and value of such foods. Generally, it is a chemical reaction involving polyphenol oxidase (PPO), catechol oxidase, and other enzymes that create melanins and benzoquinone from natural phenols. Enzymatic browning (also called oxidation of foods) requires exposure to oxygen. It begins with the oxidation of phenols by polyphenol oxidase into quinones, whose strong electrophilic state causes high susceptibility to a nucleophilic attack from other proteins. These quinones are then polymerized in a series of reactions, eventually resulting in the formation of brown pigments (melanosis) on the surface of the food. The rate of enzymatic browning is reflected by the amount of active polyphenol oxidases present in the food. Hence, most research into methods of preventing enzymatic browning has been directed towards inhibiting polyphenol oxidase activity. However, not all browning of food produces negative effects.
Examples of beneficial enzymatic browning:
* Developing color and flavor in coffee, cocoa beans, and tea.
* Developing color and flavor in dried fruit such as figs and raisins.
Examples of non-beneficial enzymatic browning:
* Fresh fruit and vegetables, including apples, potatoes, bananas and avocados.
* Oxidation of polyphenols is the major cause of melanosis in crustaceans such as shrimp. | 1 | Biochemistry |
Around 90% of the production is used to make the pigment titanium dioxide (). The conversion involves hydrolysis of , a process that forms hydrogen chloride:
In some cases, is oxidised directly with oxygen: | 0 | Organic Chemistry |
Flotation can be performed in rectangular or cylindrical mechanically agitated cells or tanks, flotation columns, Jameson Cells or deinking flotation machines. Classified by the method of air absorption manner, it is fair to state that two distinct groups of flotation equipment have arisen:pneumatic and mechanical machines. Generally pneumatic machines give a low-grade concentrate and little operating troubles.
Mechanical cells use a large mixer and diffuser mechanism at the bottom of the mixing tank to introduce air and provide mixing action. Flotation columns use air spargers to introduce air at the bottom of a tall column while introducing slurry above. The countercurrent motion of the slurry flowing down and the air flowing up provides mixing action. Mechanical cells generally have a higher throughput rate, but produce material that is of lower quality, while flotation columns generally have a low throughput rate but produce higher quality material.
The Jameson cell uses neither impellers nor spargers, instead combining the slurry with air in a downcomer where high shear creates the turbulent conditions required for bubble particle contacting. | 8 | Metallurgy |
It has been stated that Elias James Corey, also a Nobel Prize winner, feels he is responsible for the ideas that laid the foundation for this research, and that Woodward unfairly neglected to credit him in the discovery. In a 2004 memoir published in the Journal of Organic Chemistry, Corey makes his claim to priority of the idea: "On May 4, 1964, I suggested to my colleague R. B. Woodward a simple explanation involving the symmetry of the perturbed (HOMO) molecular orbitals for the stereoselective cyclobutene to 1,3-butadiene and 1,3,5-hexatriene to cyclohexadiene conversions that provided the basis for the further development of these ideas into what became known as the Woodward–Hoffmann rules".
Corey, then 35, was working into the evening on Monday, May 4, as he and the other driven chemists often did. At about 8:30 p.m., he dropped by Woodward's office, and Woodward posed a question about how to predict the type of ring a chain of atoms would form. After some discussion, Corey proposed that the configuration of electrons governed the course of the reaction. Woodward insisted the solution would not work, but Corey left drawings in the office, sure that he was on to something.
"I felt that this was going to be a really interesting development and was looking forward to some sort of joint undertaking," he wrote. But the next day, Woodward flew into Coreys office as he and a colleague were leaving for lunch and presented Coreys idea as his own – and then left. Corey was stunned.
In a 2004 rebuttal published in the Angewandte Chemie, Roald Hoffmann denied the claim: he quotes Woodward from a lecture given in 1966 saying: "I REMEMBER very clearly—and it still surprises me somewhat—that the crucial flash of enlightenment came to me in algebraic, rather than in pictorial or geometric form. Out of the blue, it occurred to me that the coefficients of the terminal terms in the mathematical expression representing the highest occupied molecular orbital of butadiene were of opposite sign, while those of the corresponding expression for hexatriene possessed the same sign. From here it was but a short step to the geometric, and more obviously chemically relevant, view that in the internal cyclisation of a diene, the top face of one terminal atom should attack the bottom face of the other, while in the triene case, the formation of a new bond should involve the top (or pari passu, the bottom) faces of both terminal atoms."
In addition, Hoffmann points out that in two publications from 1963 and 1965, Corey described a total synthesis of the compound dihydrocostunolide. Although they describe an electrocyclic reaction, Corey has nothing to offer with respect to explaining the stereospecificity of the synthesis.
This photochemical reaction involving 6 = 4×1 + 2 electrons is now recognized as conrotatory. | 7 | Physical Chemistry |
Thermochemistry aside, the rate of metabolism and an amount of energy expenditures can be mistakenly interchanged, for example, when describing RMR and REE. | 1 | Biochemistry |
If a compound has more than one chiral stereocenter, each center is denoted by either R or S. For example, ephedrine exists in (1R,2S) and (1S,2R) stereoisomers, which are distinct mirror-image forms of each other, making them enantiomers. This compound also exists as the two enantiomers written (1R,2R) and (1S,2S), which are named pseudoephedrine rather than ephedrine. All four of these isomers are named 2-methylamino-1-phenyl-1-propanol in systematic nomenclature. However, ephedrine and pseudoephedrine are diastereomers, or stereoisomers that are not enantiomers because they are not related as mirror-image copies. Pseudoephedrine and ephedrine are given different names because, as diastereomers, they have different chemical properties, even for racemic mixtures of each.
More generally, for any pair of enantiomers, all of the descriptors are opposite: (R,R) and (S,S) are enantiomers, as are (R,S) and (S,R). Diastereomers have at least one descriptor in common; for example (R,S) and (R,R) are diastereomers, as are (S,R) and (S,S). This holds true also for compounds having more than two stereocenters: if two stereoisomers have at least one descriptor in common, they are diastereomers. If all the descriptors are opposite, they are enantiomers.
A meso compound is an achiral molecule, despite having two or more stereogenic centers. A meso compound is "superimposable" on its mirror image, therefore it reduces the number of stereoisomers predicted by the 2 rule. This occurs because the molecule obtains a plane of symmetry that causes the molecule to rotate around the central carbon–carbon bond. One example is meso-tartaric acid, in which (R,S) is the same as the (S,R) form. In meso compounds the R and S stereocenters occur in symmetrically positioned pairs. | 4 | Stereochemistry |
The Ecophysiology Department, headed by Lotte Søgaard-Andersen, focuses on understanding how intracellular signalling networks are wired to allow bacteria to adapt and differentiate in response to changes in the environment or in response to self-generated signals. Specifically, the department has two aims. Firstly, they aim to understand how bacteria process information to generate appropriate output responses (e.g. changes in gene expression, changes in motility behavior). Secondly, they aim to understand how molecular machines involved in motility and secretion function and how their activity is regulated. Ecophysiology currently has three research groups led by the following in parentheses:
* Bacterial secretion systems (Andreas Diepold)
* The intracellular organization and differentiation of bacteria (Simon Ringgaard)
* Bacterial development & differentiation (Lotte Søgaard-Andersen) | 9 | Geochemistry |
The interconversion of model cyclobutene and butadiene derivatives under thermal (heating) and photochemical (Ultraviolet irradiation) conditions is illustrative.
The Woodward–Hoffmann rules apply to either direction of a pericyclic process. Due to the inherent ring strain of cyclobutene derivatives, the equilibrium between the cyclobutene and the 1,3-butadiene lies far to the right. Hence, under thermal conditions, the ring opening of the cyclobutene to the 1,3-butadiene is strongly favored by thermodynamics. On the other hand, under irradiation by ultraviolet light, a photostationary state is reached, a composition which depends on both absorbance and quantum yield of the forward and reverse reactions at a particular wavelength. Due to the different degrees of conjugation of 1,3-butadienes and cyclobutenes, only the 1,3-butadiene will have a significant absorbance at higher wavelengths, assuming the absence of other chromophores. Hence, irradiation of the 1,3-butadiene at such a wavelength can result in high conversion to the cyclobutene.
Thermolysis of trans-1,2,3,4-tetramethyl-1-cyclobutene (1) afforded only one geometric isomer, (E,E)-3,4-dimethyl-2,4-hexadiene (2); the (Z,Z) and the (E,Z) geometric isomers were not detected in the product mixture. Similarly, thermolysis of cis-1,2,3,4-tetramethyl-1-cyclobutene (3) afforded only (E,Z) isomer 4. In both ring opening reactions, the carbons on the ends of the breaking σ-bond rotate in the same direction. On the other hand, the opposite stereochemical course was followed under photochemical activation: When the related compound (E,E)-2,4-hexadiene (5) was exposed to light, cis-3,4-dimethyl-1-cyclobutene (6) was formed exclusively as a result of electrocyclic ring closure. This requires the ends of the π-system to rotate in opposite directions to form the new σ-bond. Thermolysis of 6 follows the same stereochemical course as 3: electrocyclic ring opening leads to the formation of (E,Z)-2,4-hexadiene (7) and not 5.
The Woodward-Hoffmann rules explain these results through orbital overlap:In the case of a photochemically driven electrocyclic ring-closure of buta-1,3-diene, electronic promotion causes to become the HOMO and the reaction mechanism must be disrotatory.Conversely in the electrocyclic ring-closure of the substituted hexa-1,3,5-triene pictured below, the reaction proceeds through a disrotatory mechanism. | 7 | Physical Chemistry |
Arginine fingers often work with other features in their assistance of catalysis. For example, in some trimeric dUTPases, such as those of M. tuberculosis, arginine fingers at the 64th and 140th residue can work with magnesium to cleave dUTP into dUMP and a pyrophosphate. The underlying mechanism of action for this is a nucleophilic attack; the positively charged magnesium ion () pulls on an oxygen of the beta and gamma phosphates to allow water to hydrolyze the bond between the beta and alpha phosphates. The arginine fingers help stabilize the transition state. Arginine fingers often interact with other motifs such as the Walker motifs and to perform catalysis more efficiently. | 1 | Biochemistry |
It is often useful to alter the copolymer equation by expressing concentrations in terms of mole fractions. Mole fractions of monomers and in the feed are defined as and where
Similarly, represents the mole fraction of each monomer in the copolymer:
These equations can be combined with the Mayo–Lewis equation to give
This equation gives the composition of copolymer formed at each instant. However the feed and copolymer compositions can change as polymerization proceeds. | 7 | Physical Chemistry |
* Polysorbate 20 (polyoxyethylene (20) sorbitan monolaurate)
* Polysorbate 40 (polyoxyethylene (20) sorbitan monopalmitate)
* Polysorbate 60 (polyoxyethylene (20) sorbitan monostearate)
* Polysorbate 80 (polyoxyethylene (20) sorbitan monooleate)
The number following the polysorbate part is related to the type of major fatty acid associated with the molecule. Monolaurate is indicated by 20, monopalmitate is indicated by 40, monostearate by 60, and monooleate by 80. The number 20 following the polyoxyethylene part refers to the total number of oxyethylene (–CHCHO–) groups found in the molecule. | 0 | Organic Chemistry |
Tetrakis(triphenylphosphine)palladium(0) was first prepared by Lamberto Malatesta et al. in the 1950s by reduction of sodium chloropalladate with hydrazine in the presence of the phosphine. It is commercially available, but can be prepared in two steps from Pd(II) precursors:
:PdCl + 2 PPh → PdCl(PPh)
:PdCl(PPh) + 2 PPh + NH → Pd(PPh) + N + 2 NHCl
Both steps may be carried out in a one-pot reaction, without isolating and purifying the PdCl(PPh) intermediate. Reductants other than hydrazine can be employed, including ascorbic acid. The compound is sensitive to air, but can be purified by washing with methanol to give the desired yellow powder. It is usually stored cold under argon. | 0 | Organic Chemistry |
The area is rich in fossil fuels. Oil wells were being dug in the region as early as the 10th century to reach oil "for use in everyday life, both for medicinal purposes and for heating and lighting in homes". By the 16th century, Europeans were aware of the rich oil and gas deposits locally. English traders Thomas Bannister and Jeffrey Duckett described the area around Baku as "a strange thing to behold, for there issueth out of the ground a marvelous quantity of oil, which serveth all the country to burn in their houses. This oil is black and is called nefte. There is also by the town of Baku, another kind of oil which is white and very precious [i.e., petroleum]."
Today, oil and gas platforms abound along the edges of the sea. | 2 | Environmental Chemistry |
A Coulomb collision is a binary elastic collision between two charged particles interacting through their own electric field. As with any inverse-square law, the resulting trajectories of the colliding particles is a hyperbolic Keplerian orbit. This type of collision is common in plasmas where the typical kinetic energy of the particles is too large to produce a significant deviation from the initial trajectories of the colliding particles, and the cumulative effect of many collisions is considered instead. The importance of Coulomb collisions was first pointed out by Lev Landau in 1936, who also derived the corresponding kinetic equation which is known as the Landau kinetic equation. | 7 | Physical Chemistry |
Tammann was born in Yamburg (now Kingisepp, Leningrad Oblast). His father, Heinrich Tammann (1833–1864) was of Estonian peasant origin and his mother, Matilda Schünmann, was of German origin. Tammann graduated from University of Dorpat in chemistry. He came to Göttingen University in 1903 where he established the first Institute of Inorganic Chemistry in Germany. In 1908 he was appointed director of the Physico-Chemical Institute. His interests focused on the physics and physical chemistry of metals and alloys (metallurgy). In 1925, Tammann was awarded Liebig Medal. On 28 May 1936, Tammann was awarded the Eagle Shield of the German Empire (), with dedication "The Doyen of German Metallurgy". He was also known for the Vogel-Fulcher-Tammann equation, and the Tait-Tammann equation of state which seeks to account for the compressibility of liquids.
Tammann died in Göttingen at age 77. | 7 | Physical Chemistry |
There are two main approaches to definition of the spectral flux density at a measuring point in an electromagnetic radiative field. One may be conveniently here labelled the vector approach, the other the scalar approach. The vector definition refers to the full spherical integral of the spectral radiance (also known as the specific radiative intensity or specific intensity) at the point, while the scalar definition refers to the many possible hemispheric integrals of the spectral radiance (or specific intensity) at the point. The vector definition seems to be preferred for theoretical investigations of the physics of the radiative field. The scalar definition seems to be preferred for practical applications. | 7 | Physical Chemistry |
The Pauly reaction is a chemical test used for detecting the presence of tyrosine or histidine in proteins. It is named after German chemist Hermann Pauly, who first described the reaction. When proteins containing either tyrosine or histidine are reacted with diazotized sulfanilic acid under alkaline conditions, a red color is formed by a coupling reaction. | 3 | Analytical Chemistry |
Such soils natively have little tilth, especially once they have been disturbed. Adding organic matter up to 25% by volume can help compensate. For example, if tilling to a depth of eight inches, add two inches of organic materials. | 9 | Geochemistry |
Vitamins occur in a variety of related forms known as vitamers. The vitamers of a given vitamin perform the functions of that vitamin and prevent symptoms of deficiency of that vitamin. Vitamins are those essential organic molecules that are not classified as amino acids or fatty acids. They commonly function as enzymatic cofactors, metabolic regulators or antioxidants. Humans require thirteen vitamins in their diet, most of which are actually groups of related molecules (e.g. vitamin E includes tocopherols and tocotrienols): vitamins A, C, D, E, K, thiamine (B), riboflavin (B), niacin (B), pantothenic acid (B), pyridoxine (B), biotin (B), folate (B), and cobalamin (B). The requirement for vitamin D is conditional, as people who get sufficient exposure to ultraviolet light, either from the sun or an artificial source, synthesize vitamin D in the skin. | 9 | Geochemistry |
Joule heating can also be calculated at a particular location in space. The differential form of the Joule heating equation gives the power per unit volume.
Here, is the current density, and is the electric field. For a material with a conductivity , and therefore
where is the resistivity. This directly resembles the "" term of the macroscopic form.
In the harmonic case, where all field quantities vary with the angular frequency as , complex valued phasors and are usually introduced for the current density and the electric field intensity, respectively. The Joule heating then reads
where denotes the complex conjugate. | 7 | Physical Chemistry |
* Intracytoplasmic sperm injection (ICSI) is where a single sperm is injected directly into an egg. Its main usage as an expansion of IVF is to overcome male infertility problems, although it may also be used where eggs cannot easily be penetrated by sperm, and occasionally in conjunction with sperm donation. It can be used in teratozoospermia, since once the egg is fertilised abnormal sperm morphology does not appear to influence blastocyst development or blastocyst morphology.
* Additional methods of embryo profiling. For example, methods are emerging in making comprehensive analyses of up to entire genomes, transcriptomes, proteomes and metabolomes which may be used to score embryos by comparing the patterns with ones that have previously been found among embryos in successful versus unsuccessful pregnancies.
* Assisted zona hatching (AZH) can be performed shortly before the embryo is transferred to the uterus. A small opening is made in the outer layer surrounding the egg in order to help the embryo hatch out and aid in the implantation process of the growing embryo.
* In egg donation and embryo donation, the resultant embryo after fertilisation is inserted in another person than the one providing the eggs. These are resources for those with no eggs due to surgery, chemotherapy, or genetic causes; or with poor egg quality, previously unsuccessful IVF cycles or advanced maternal age. In the egg donor process, eggs are retrieved from a donors ovaries, fertilised in the laboratory with sperm, and the resulting healthy embryos are returned to the recipients uterus.
* In oocyte selection, the oocytes with optimal chances of live birth can be chosen. It can also be used as a means of preimplantation genetic screening.
* Embryo splitting can be used for twinning to increase the number of available embryos.
*Cytoplasmic transfer is where the cytoplasm from a donor egg is injected into an egg with compromised mitochondria. The resulting egg is then fertilised with sperm and introduced into a uterus, usually that of the person who provided the recipient egg and nuclear DNA. Cytoplasmic transfer was created to aid those who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm. | 1 | Biochemistry |
Assuming that the concentration is at equilibrium and the flow velocity is zero, meaning that only the ion species moves, the Nernst–Planck equation takes the form:
Rather than a general electric field, if we assume that only the electrostatic component is significant, the equation is further simplified by removing the time derivative of the magnetic vector potential:
Finally, in units of mol/(m·s) and the gas constant , one obtains the more familiar form:
where is the Faraday constant equal to ; the product of Avogadro constant and the elementary charge. | 7 | Physical Chemistry |
The Leimgruber–Batcho, Bartoli and Baeyer–Emmerling indole syntheses begin with aromatic nitro compounds. Indigo can be synthesized in a condensation reaction from ortho-nitrobenzaldehyde and acetone in strongly basic conditions in a reaction known as the Baeyer–Drewson indigo synthesis. | 0 | Organic Chemistry |
Archaeal transcription factor B (ATFB or TFB) is a protein family of extrinsic transcription factors that guide the initiation of RNA transcription in organisms that fall under the domain of Archaea. It is homologous to eukaryotic TFIIB and, more distantly, to bacterial sigma factor. Like these proteins, it is involved in forming transcription preinitiation complexes. Its structure includes several conserved motifs which interact with DNA and other transcription factors, notably the single type of RNA polymerase that performs transcription in Archaea. | 1 | Biochemistry |
An oligosaccharide (; ) is a saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars). Oligosaccharides can have many functions including cell recognition and cell adhesion.
They are normally present as glycans: oligosaccharide chains are linked to lipids or to compatible amino acid side chains in proteins, by N- or O-glycosidic bonds. N-Linked oligosaccharides are always pentasaccharides attached to asparagine via a beta linkage to the amine nitrogen of the side chain. Alternately, O-linked oligosaccharides are generally attached to threonine or serine on the alcohol group of the side chain. Not all natural oligosaccharides occur as components of glycoproteins or glycolipids. Some, such as the raffinose series, occur as storage or transport carbohydrates in plants. Others, such as maltodextrins or cellodextrins, result from the microbial breakdown of larger polysaccharides such as starch or cellulose. | 0 | Organic Chemistry |
For Raman spectra the molecules undergo transitions in which an incident photon is absorbed and another scattered photon is emitted. The general selection rule for such a transition to be allowed is that the molecular polarizability must be anisotropic, which means that it is not the same in all directions. Polarizability is a 3-dimensional tensor that can be represented as an ellipsoid. The polarizability ellipsoid of spherical top molecules is in fact spherical so those molecules show no rotational Raman spectrum. For all other molecules both Stokes and anti-Stokes lines can be observed and they have similar intensities due to the fact that many rotational states are thermally populated. The selection rule for linear molecules is ΔJ = 0, ±2. The reason for the values ±2 is that the polarizability returns to the same value twice during a rotation. The value ΔJ = 0 does not correspond to a molecular transition but rather to Rayleigh scattering in which the incident photon merely changes direction.
The selection rule for symmetric top molecules is
: ΔK = 0
: If K = 0, then ΔJ = ±2
: If K ≠ 0, then ΔJ = 0, ±1, ±2
Transitions with ΔJ = +1 are said to belong to the R series, whereas transitions with belong to an S series. Since Raman transitions involve two photons, it is possible for the molecular angular momentum to change by two units. | 7 | Physical Chemistry |
Extensive research has been carried out on the metallurgical material from Tell Hammeh. Both excavation and archaeometric analyses were carried out by Dr H.A. Veldhuijzen, first at Leiden University, then since 2001 at the UCL Institute of Archaeology, as a part of the joint excavations conducted by Yarmouk University and Leiden University and co-directed by Prof. Dr. Zeidan Kafafi and Dr. Gerrit Van der Kooij. | 8 | Metallurgy |
There is no reported total synthesis of chloroeremomycin, although there are several total syntheses of vancomycin. The structures of vancomycin and chloroeremomycin are very similar, differing only in the glycosylation sites. Vancomycin is glycosylated at aa4 with a (2-beta1)-Glc-vancosamine disaccharide. As mentioned above, chloroeremomycin is glycosylated at aa4 with a (2-beta1)-Glc-epivancosamine disaccharide and at aa6 with a beta1-epivancosamine saccharide. | 0 | Organic Chemistry |
Seraj studied at the University of Dhaka, Bangladesh obtaining a B.Sc. in 1980. She completed her M.Sc. from the same university in 1982. She obtained her PhD in biochemistry from University of Glasgow in 1986 and went to University of Liverpool for post-doctoral work in the following year. After completing her post-doc., she joined the Department of Biochemistry and Molecular Biology, University of Dhaka in 1988. She became an associate professor in 1991 and later a professor in 1997 at the same university. She has been supervising plant biotechnology projects funded by foreign and local grants as a principal investigator since 1991. She is a visiting researcher with UT Austin since 2013 | 1 | Biochemistry |
The active site of PLE facilitates both substrate binding and hydrolysis. A key serine residue in the active site promotes hydrolysis, but the substrate must present an ester group to this residue after binding to the enzyme active site for hydrolysis to take place. Whether the substrate is able to present an ester group to the catalytic serine residue depends on its bound conformation in the active site, which is dictated by amino acid side-chains in the active site. Thus, active site models of PLE have been advanced with the goal of predicting from the structure of the substrate which of two enantiotopic ester groups will be hydrolyzed (or whether hydrolysis is likely to occur at all).
A simple model for the binding conformation of an ester in the active site of PLE is shown below. This model accurately predicts the configuration of hydrolyzed glutarates and similar substrates. | 0 | Organic Chemistry |
Past recipients of the Lilly Award:
*1935 – Willard Myron Allen
*1939 – George Wald
*1941 – David Rittenberg
*1942 – Earl A. Evans, Jr.
*1943 – Herbert E. Carter
*1944 – Joseph S. Fruton
*1946 – John D. Ferry
*1947 – Sidney Colowick
*1948 – Dilworth Wayne Woolley
*1951 – John M. Buchanan
*1953 – Nathan O. Kaplan
*1954 – Harvey A. Itano
*1955 – William F. Neuman
*1956 – Robert A. Alberty
*1957 – Harold A. Scheraga
*1958 – Lester J. Reed
*1959 – Paul Berg
*1960 – James D. Watson
*1962 – Jerard Hurwitz
*1963 – William P. Jencks
*1964 – Bruce N. Ames
*1965 – Gerald M. Edelman
*1966 – Phillips W. Robbins
*1967 – Gordon G. Hammes
*1968 – Charles C. Richardson
*1969 – Mario R. Capecchi
*1970 – Lubert Stryer
*1972 – Bruce M. Alberts
*1974 – James Dahlberg
*1975 – Mark Ptashne
*1976 – Joan A. Steitz
*1977 – Robert G. Roeder
*1978 – Charles R. Cantor
*1979 – Christopher T. Walsh
*1980 – Phillip A. Sharp
*1981 – Roger D. Kornberg
*1982 – Harold M. Weintraub
*1983 – Richard Axel
*1984 – David V. Goeddel
*1985 – Gerald M. Rubin
*1986 – James E. Rothman
*1987 – Jacqueline K. Barton
*1988 – Peter Walter
*1990 – George L. McLendon
*1991 – Peter G. Schultz
*1992 – William DeGrado
*1993 – Stuart L. Schreiber
*1994 – Peter S. Kim
*1995 – Jeremy Berg
*1996 – Gregory L. Verdine
*1997 – Alanna Schepartz
*1998 – John Kuriyan
*1999 – Chaitan Khosla
*2000 – Xiaodong Wang
*2001 – Jennifer Doudna
*2002 – Kevan M. Shokat
*2003 – Andreas Matouschek
*2004 – Benjamin Cravatt III
*2006 – Linda Hsieh-Wilson
*2007 – Anna K. Mapp
*2008 – Paul J. Hergenrother
*2009 – Scott K. Silverman
*2010 – Alice Y. Ting
*2011 – Nathanael Gray
*2012 – Christopher J. Chang
*2016 – Elizabeth Nolan
*2017 – Howard C. Hang
*2018 – Bradley L. Pentelute
*2019 – Neal Devaraj
*2020 – Yimon Aye
*2021 – Jordan L. Meier
*2022 – Lingyin Li
*2023 – Polly Fordyce | 1 | Biochemistry |
Magnussen model is a popular method for computing reaction rates as a function of both mean concentrations and turbulence levels (Magnussen and Hjertager). Originally developed for combustion, it can also be used for liquid reactions by tuning some of its parameters. The model consists of rates calculated by two primary means. An Arrhenius, or kinetic rate, , for species in reaction , is governed by the local mean species concentrations and temperature in the following way:
This expression describes the rate at which species is consumed in reaction . The constants and , the Arrhenius pre-exponential factor and activation energy,
respectively, are adjusted for specific reactions, often as the result of experimental measurements. The stoichiometry for species in reaction is represented by the factor , and is positive or negative, depending upon whether the species serves as a product or reactant. The molecular weight of the species appears as the factor . The temperature, , appears in the exponential term and also as a factor in the rate expression, with an optional exponent, . Concentrations of other species, , involved in the reaction, , appear as factors with optional exponents associated with each. Other factors and terms not appearing in the equation, can be added to include effects such as the presence of non-reacting
species in the rate equation. Such so-called third-body reactions are typical of the effect of a catalyst on a reaction, for example. Many of the factors are often collected into a single rate constant, . | 7 | Physical Chemistry |
Prokaryotes have a prokaryotic cytoskeleton that is more primitive than that of the eukaryotes. Besides homologues of actin and tubulin (MreB and FtsZ), the helically arranged building-block of the flagellum, flagellin, is one of the most significant cytoskeletal proteins of bacteria, as it provides structural backgrounds of chemotaxis, the basic cell physiological response of bacteria. At least some prokaryotes also contain intracellular structures that can be seen as primitive organelles.
Membranous organelles (or intracellular membranes) are known in some groups of prokaryotes, such as vacuoles or membrane systems devoted to special metabolic properties, such as photosynthesis or chemolithotrophy. In addition, some species also contain carbohydrate-enclosed microcompartments, which have distinct physiological roles (e.g. carboxysomes or gas vacuoles).
Most prokaryotes are between 1 µm and 10 µm, but they can vary in size from 0.2 µm (Mycoplasma genitalium) to 750 µm (Thiomargarita namibiensis). | 1 | Biochemistry |
In terms of genomic coverage and accuracy, whole genome sequencing can broadly be classified into either of the following:
* A draft sequence, covering approximately 90% of the genome at approximately 99.9% accuracy
* A finished sequence, covering more than 95% of the genome at approximately 99.99% accuracy
Producing a truly high-quality finished sequence by this definition is very expensive. Thus, most human "whole genome sequencing" results are draft sequences (sometimes above and sometimes below the accuracy defined above). | 1 | Biochemistry |
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