text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
Carbon catabolite repression, or simply catabolite repression, is an important part of global control system of various bacteria and other microorganisms. Catabolite repression allows microorganisms to adapt quickly to a preferred (rapidly metabolizable) carbon and energy source first. This is usually achieved through inhibition of synthesis of enzymes involved in catabolism of carbon sources other than the preferred one. The catabolite repression was first shown to be initiated by glucose and therefore sometimes referred to as the glucose effect. However, the term "glucose effect" is actually a misnomer since other carbon sources are known to induce catabolite repression. | 1 | Biochemistry |
The theoretically predicted maximum of the melting curve (the prerequisite for the liquid metallic hydrogen) was discovered by Shanti Deemyad and Isaac F. Silvera by using pulsed laser heating. Hydrogen-rich molecular silane () was claimed to be metallized and become superconducting by M.I. Eremets et al.. This claim is disputed, and their results have not been repeated. | 7 | Physical Chemistry |
When two or more sites in an asymmetrical molecule may be involved in an equilibrium reaction there are more than one possible equilibrium constants. For example, the molecule -DOPA has two non-equivalent hydroxyl groups which may be deprotonated. Denoting -DOPA as LH, the following diagram shows all the species that may be formed (X = ).
The concentration of the species LH is equal to the sum of the concentrations of the two micro-species with the same chemical formula, labelled LH and LH. The constant K is for a reaction with these two micro-species as products, so that [LH] = [LH] + [LH] appears in the numerator, and it follows that this macro-constant is equal to the sum of the two micro-constants for the component reactions.
:K = k + k
However, the constant K is for a reaction with these two micro-species as reactants, and [LH] = [LH] + [LH] in the denominator, so that in this case
:1/K =1/ k + 1/k,
and therefore K =k k / (k + k).
Thus, in this example there are four micro-constants whose values are subject to two constraints; in consequence, only the two macro-constant values, for K and K can be derived from experimental data.
Micro-constant values can, in principle, be determined using a spectroscopic technique, such as infrared spectroscopy, where each micro-species gives a different signal. Methods which have been used to estimate micro-constant values include
* Chemical: blocking one of the sites, for example by methylation of a hydroxyl group, followed by determination of the equilibrium constant of the related molecule, from which the micro-constant value for the "parent" molecule may be estimated.
* Mathematical: applying numerical procedures to C NMR data.
Although the value of a micro-constant cannot be determined from experimental data, site occupancy, which is proportional to the micro-constant value, can be very important for biological activity. Therefore, various methods have been developed for estimating micro-constant values. For example, the isomerization constant for -DOPA has been estimated to have a value of 0.9, so the micro-species LH and LH have almost equal concentrations at all pH values. | 7 | Physical Chemistry |
Diphenylphosphoryl azide (DPPA) is an organic compound. It is widely used as a reagent in the synthesis of other organic compounds. | 0 | Organic Chemistry |
Metabolic flexibility is the capacity to alter metabolism in response to exercise or available fuel (especially fats and carbohydrates). Metabolic inflexibility was first described as the ability to generate energy through either aerobic or anaerobic respiration or as the inability of muscle to increase glucose oxidation in response to insulin.
An organism can also be said to have metabolic flexibility if it is capable of metabolizing either carbohydrate or fat efficiently, depending on availability of those fuels. By this definition, metabolic flexibility can be quantified using respiratory quotient. This form of metabolic flexibility is reduced by insulin resistance.
With aging there is a decrease in metabolic flexibility due to a decline in pyruvate dehydrogenase activity which results in pyruvate increasingly being anaerobically converted to lactate rather than aerobically converted to acetyl-CoA. Similarly, a virus-induced cytokine storm can compromise metabolic flexibility by inactivating the pyruvate dehydrogenase complex and other enzymes. | 1 | Biochemistry |
The first type of photocyte granule has been found to contain between two and twelve microtubules. In addition, the matrix of the type I granule lacks a uniform shape or structure with ferritin distributed throughout. | 1 | Biochemistry |
During physical exertion or moderate intensity exercise lactate released from working muscle and other tissue beds is the primary fuel source for the heart, exiting the muscles through monocarboxylate transport protein (MCT). This evidence is supported by an increased amount of MCT shuttle proteins in the heart and muscle in direct proportion to exertion as measured through muscular contraction.
Furthermore, both neurons and astrocytes have been shown to express MCT proteins, suggesting that the lactate shuttle may be involved in brain metabolism. Astrocytes express MCT4, a low affinity transporter for lactate (Km = 35mM), suggesting its function is to export lactate produced by glycolysis. Conversely, neurons express MCT2, a high affinity transporter for lactate (Km = 0.7mM). Thus, it is hypothesized that the astrocytes produce lactate which is then taken up by the adjacent neurons and oxidized for fuel. | 1 | Biochemistry |
Victor Snieckus (August 1, 1937 - December 18, 2020) was a synthetic organic chemist and professor emeritus at Queen's University in Kingston, Ontario. He was known for his influential research on directed ortho metalation. | 0 | Organic Chemistry |
Coordination cages are used to study guest-guest and host–guest interactions and reactions.
In some instance, planar aromatic molecules stack inside of metalloprisms, as can be observed by UV-visible spectroscopy. Metal-metal interactions can also be observed. Mixed valence species have also been trapped inside of coordination cages. | 6 | Supramolecular Chemistry |
MDS has been used to characterise interactions between biomolecules under native conditions, and has been demonstrated to detect specific interactions within complex mixtures. It has also been used in detecting and quantifying protein-ligand interactions and protein-lipid interactions. | 1 | Biochemistry |
The growing knowledge behind the mechanism of autocrine signaling in cancer progression has revealed new approaches for therapeutic treatment. For example, autocrine Wnt signaling could provide a novel target for therapeutic intervention by means of Wnt antagonists or other molecules that interfere with ligand-receptor interactions of the Wnt pathway. In addition, VEGF-A production and VEGFR-2 activation on the surface of breast cancer cells indicates the presence of a distinct autocrine signaling loop that enables breast cancer cells to promote their own growth and survival by phosphorylation and activation of VEGFR-2. This autocrine loop is another example of an attractive therapeutic target.
In HER2 overexpressing breast cancers, the HER2–IL-6–STAT3 signaling relationship could be targeted to develop new therapeutic strategies. HER2 kinase inhibitors, such as lapatinib, have also demonstrated clinical efficacy in HER2 overexpressing breast cancers by disrupting a neuregulin-1 (NRG1)-mediated autocrine loop.
In the case of PDGFR signalling, overexpression of a dominant-negative PDGFR or application of the cancer drug STI571 are both approaches being explored to therapeutically interference with metastasis in mice.
In addition, drugs may be developed that activate autocrine signaling in cancer cells that would not otherwise occur. For example, a small-molecule mimetic of Smac/Diablo that counteracts the inhibition of apoptosis has been shown to enhance apoptosis caused by chemotherapeutic drugs through autocrine-secreted tumor necrosis factor alpha (TNFα). In response to autocrine TNFα signaling, the Smac mimetic promotes formation of a RIPK1-dependent caspase-8-activating complex, leading to apoptosis. | 1 | Biochemistry |
The non-enzymatic glycosylation is also known as glycation or non-enzymatic glycation. It is a spontaneous reaction and a type of post-translational modification of proteins meaning it alters their structure and biological activity. It is the covalent attachment between the carbonil group of a reducing sugar (mainly glucose and fructose) and the amino acid side chain of the protein. In this process the intervention of an enzyme is not needed. It takes place across and close to the water channels and the protruding tubules.
At first, the reaction forms temporary molecules which later undergo different reactions (Amadori rearrangements, Schiff base reactions, Maillard reactions, crosslinkings...) and form permanent residues known as Advanced Glycation end-products (AGEs).
AGEs accumulate in long-lived extracellular proteins such as collagen which is the most glycated and structurally abundant protein, especially in humans. Also, some studies have shown lysine may trigger spontaneous non-enzymatic glycosylation. | 0 | Organic Chemistry |
Chlorprothixene's principal indications are the treatment of psychotic disorders (e.g. schizophrenia) and of acute mania occurring as part of bipolar disorders.
Other uses are pre- and postoperative states with anxiety and insomnia, severe nausea / emesis (in hospitalized patients), the amelioration of anxiety and agitation due to use of selective serotonin reuptake inhibitors for depression and, off-label, the amelioration of alcohol and opioid withdrawal. It may also be used cautiously to treat nonpsychotic irritability, aggression, and insomnia in pediatric patients.
An intrinsic antidepressant effect of chlorprothixene has been discussed, but not proven. Likewise, it is unclear if chlorprothixene has genuine (intrinsic) analgesic effects. However, chlorprothixene can be used as co-medication in severe chronic pain. Also, like most antipsychotics, chlorprothixene has antiemetic effects. | 4 | Stereochemistry |
FASTpp measures the quantity of protein that resists digestion under various conditions. To this end, a thermostable protease is used, which cleaves specifically at exposed hydrophobic residues. The FASTpp assay combines the thermal unfolding, specificity of a thermostable protease for the unfolded fraction with the separation power of SDS-PAGE. Due to this combination, FASTpp can detect changes in the fraction folded over a large physico-chemical range of conditions including temperatures up to 85 °C, pH 6–9, presence or absence of the whole proteome. Applications range from biotechnology to study of point mutations and ligand binding assays. | 1 | Biochemistry |
Other flow-type batteries include the zinc–cerium battery, the zinc–bromine battery, and the hydrogen–bromine battery. | 7 | Physical Chemistry |
In 1941, Kharash discovered that Grignard reagents add to cyclohexenone in presence of Cu(I) resulting in 1,4-addition instead of 1,2-addition. This work foreshadowed extensive studies on the conjugate additions to enones with organocuprates. Note that if a Grignard reagent (such as RMgBr) is used, the reaction with an enone would instead proceed through a 1,2-addition. The 1,4-addition mechanism of cuprates to enones goes through the nucleophilic addition of the Cu(I) species at the beta-carbon of the alkene to form a Cu(III) intermediate, followed by reductive elimination of Cu(I). In the original paper describing this reaction, methylmagnesium bromide is reacted with isophorone with and without 1 mole percent of added copper(I) chloride (see figure).
Without added salt the main products are alcohol B (42%) from nucleophilic addition to the carbonyl group and diene C (48%) as its dehydration reaction product. With added salt the main product is 1,4-adduct A (82%) with some C (7%).
A 1,6-addition is also possible, for example in one step of the commercial-scale production of fulvestrant: | 0 | Organic Chemistry |
Heat and light stabilizers are added to plastics because they ensure safe processing and protect products against aging and weathering. The trend is towards fluid systems, pellets, and increased use of masterbatches. There are monofunctional, bifunctional, and polyfunctional stabilizers. In economic terms the most important product groups on the market for stabilizers are compounds based on calcium (calcium-zinc and organo-calcium), lead, and tin stabilizers as well as liquid and light stabilizers (HALS, benzophenone, benzotriazole). Cadmium-based stabilizers largely vanished in the last years due to health and environmental concerns. | 7 | Physical Chemistry |
The method is amenable to a range of different templates: PCR products, plasmids and mRNA. Additional components can be included during synthesis to adjust the environment for protein folding, disulfide bond formation, modification or protein activity. | 1 | Biochemistry |
A viral titer is the lowest concentration of a virus that still infects cells. To determine the titer, several dilutions are prepared, such as 10, 10, 10, ... 10.
The titer of a fat is the temperature, in degrees Celsius, at which it solidifies. The higher the titer, the harder the fat. This titer is used in determining whether an animal fat is considered tallow (titer higher than 40 °C) or a grease (titer below 40 °C). | 1 | Biochemistry |
Wittig was born in Berlin, Germany and shortly after his birth moved with his family to Kassel, where his father was professor at the applied arts high school. He attended school in Kassel and started studying chemistry at the University of Tübingen 1916. He was drafted and became a lieutenant in the cavalry of Hesse-Kassel (or Hesse-Cassel). After being an Allied prisoner of war from 1918 until 1919, Wittig found it hard to restart his chemistry studies owing to overcrowding at the universities. By a direct plea to Karl von Auwers, who was professor for organic chemistry at the University of Marburg at the time, he was able to resume university study and after 3 years was awarded the Ph.D. in organic chemistry.
Karl von Auwers was able to convince him to start an academic career, leading to his habilitation in 1926. He became a close friend of Karl Ziegler, who was also doing his habilitation with Auwers during that time. The successor of Karl von Auwers, Hans Meerwein, accepted Wittig as lecturer, partly because he was impressed by the new 400-page book on stereochemistry that Wittig had written. In 1931 Wittig married Waltraud Ernst, a colleague from the Auwers working group. The invitation of Karl Fries brought him as professor to the TU Braunschweig in 1932. The time in Braunschweig became more and more problematic as the Nazis tried to get rid of Karl Fries and Wittig showed solidarity with him. After the forced retirement of Fries, in 1937 Hermann Staudinger offered Wittig a position at the University of Freiburg, partly because he knew Wittig from his book on stereochemistry in which he supported Staudingers highly criticized theory of macromolecules. The foundations of carbanion chemistry were laid during Wittigs time in Freiburg.
In 1944 he succeeded the head of the organic chemistry department Wilhelm Schlenk at the University of Tübingen. Most of his scientific work, including the development of the Wittig reaction, was performed during this time in Tübingen. The 1956 appointment of the nearly sixty-year-old Wittig as head of the organic chemistry department at the University of Heidelberg as successor of Karl Freudenberg was exceptional even at that time. The newly built department and the close connection to the BASF convinced Wittig to take this opportunity. He worked at the University of Heidelberg even after his retirement in 1967 and published papers until 1980. Most of his awards were presented during this time at Heidelberg, such as the honorary doctorate of the Sorbonne in 1956 and the Nobel Prize in Chemistry in 1979. | 4 | Stereochemistry |
In 2019, Stephan and co-workers at the University of Toronto reported the first examples of di-vinyl-substituted diphosphenes via a ring opening/dimerization process from kinetically unstable 2H-phosphirenes. | 0 | Organic Chemistry |
Gel electrophoresis is a technique which separates molecules by their size using an agarose or polyacrylamide gel. This technique is one of the principal tools of molecular biology. The basic principle is that DNA fragments can be separated by applying an electric current across the gel - because the DNA backbone contains negatively charged phosphate groups, the DNA will migrate through the agarose gel towards the positive end of the current. Proteins can also be separated on the basis of size using an SDS-PAGE gel, or on the basis of size and their electric charge by using what is known as a 2D gel electrophoresis. | 1 | Biochemistry |
The halogens, nitrogen, and sulfur are covalently bonded to the organic compounds are converted to various sodium salts formed during the fusion. Typically proposed reactions are:
:Na + C + N → NaCN
:Na + C + N + S → NaSCN
:2Na + S → NaS
:Na + X → NaX
The fate of the hydrocarbon portion of the sample is disregarded.
The aqueous extract is called sodium fusion extract or Lassaigne's extract. | 3 | Analytical Chemistry |
Stereographic projection plots can be carried out by a computer using the explicit formulas given above. However, for graphing by hand these formulas are unwieldy. Instead, it is common to use graph paper designed specifically for the task. This special graph paper is called a stereonet or Wulff net, after the Russian mineralogist George (Yuri Viktorovich) Wulff.
The Wulff net shown here is the stereographic projection of the grid of parallels and meridians of a hemisphere centred at a point on the equator (such as the Eastern or Western hemisphere of a planet).
In the figure, the area-distorting property of the stereographic projection can be seen by comparing a grid sector near the center of the net with one at the far right or left. The two sectors have equal areas on the sphere. On the disk, the latter has nearly four times the area of the former. If the grid is made finer, this ratio approaches exactly 4.
On the Wulff net, the images of the parallels and meridians intersect at right angles. This orthogonality property is a consequence of the angle-preserving property of the stereographic projection. (However, the angle-preserving property is stronger than this property. Not all projections that preserve the orthogonality of parallels and meridians are angle-preserving.)
For an example of the use of the Wulff net, imagine two copies of it on thin paper, one atop the other, aligned and tacked at their mutual center. Let be the point on the lower unit hemisphere whose spherical coordinates are (140°, 60°) and whose Cartesian coordinates are (0.321, 0.557, −0.766). This point lies on a line oriented 60° counterclockwise from the positive -axis (or 30° clockwise from the positive -axis) and 50° below the horizontal plane . Once these angles are known, there are four steps to plotting :
#Using the grid lines, which are spaced 10° apart in the figures here, mark the point on the edge of the net that is 60° counterclockwise from the point (1, 0) (or 30° clockwise from the point (0, 1)).
#Rotate the top net until this point is aligned with (1, 0) on the bottom net.
#Using the grid lines on the bottom net, mark the point that is 50° toward the center from that point.
#Rotate the top net oppositely to how it was oriented before, to bring it back into alignment with the bottom net. The point marked in step 3 is then the projection that we wanted.
To plot other points, whose angles are not such round numbers as 60° and 50°, one must visually interpolate between the nearest grid lines. It is helpful to have a net with finer spacing than 10°. Spacings of 2° are common.
To find the central angle between two points on the sphere based on their stereographic plot, overlay the plot on a Wulff net and rotate the plot about the center until the two points lie on or near a meridian. Then measure the angle between them by counting grid lines along that meridian. | 3 | Analytical Chemistry |
The anthocyanin biosynthesis pathway is now well known and most of the enzymes are characterised. In the formation of blue pigments a few enzymes have particularly important roles, in particular flavonoid 35-hydroxylase (F35H) and dihydroflavonol 4-reductase (DFR).
The flavonoid 35H-hydroxylase is responsible for the introduction of the second and third hydroxyl group in the B-ring of dihydrokaempferol (DHK) or naringenin which are regarded as the main substrates of the reaction. Product of the reaction with DHK is dihydromyricetin (DHM), precursor for synthesis of all delphinidin type anthocyanin. Enzyme is a member of cytochrome P450 protein family (P450s). It is a very diverse group of heme-containing oxidases, which catalyse NADPH- or NADH-dependent oxidation. F35H was classified into CYP75A subfamily. This enzyme this is regarded as necessary for the blue pigment formation.
Dihydroflavonol 4-reductase is the oxidoreductase that catalyses in the presence of NADPH the stereospecific reduction of the keto group in position 4 of dihydroflavonols producing colourless leucoanthocyanidins as a precursor for anthocyanin formation. Enzyme can show substrate specificity with respect to the B-ring hydroxylation pattern of the dihydroflavonol and can therefore have an influence on the type of formed anthocyanin. For the blue pigment formation, necessary is enzyme, which accept dihydromyricetin (DHM) as a substrate. Product of DFR reaction with DHM in the following steps of the pathway is converted to delphinidin type blue pigments. | 1 | Biochemistry |
The aerobic onia idation process is also know, as the ANAMMOX process, an abbreviation coined by joining the first syllables of each of these three words. This biological process is a redox comproportionation reaction, in which ammonia (the reducing agent giving electrons) and nitrite (the oxidizing agent accepting electrons) transfer three electrons and are converted into one molecule of diatomic nitrogen () gas and two water molecules. This process makes up a major proportion of nitrogen conversion in the oceans. The stoichiometrically balanced formula for the ANAMMOX chemical reaction can be written as following, where an ammonium ion includes the ammonia molecule, its conjugated base:
: (ΔG° = ).
This an exergonic process (here also an exothermic reaction) releasing energy, as indicated by the negative value of ΔG°, the difference in Gibbs free energy between the products of reaction and the reagents. | 1 | Biochemistry |
In the US, individual states are allowed to develop their own water quality standards based on EPA's recommendations under the Clean Water Act of 1977. Once water quality standards are approved, states are tasked with monitoring their surface waters to determine where impairments occur, and watershed plans called Total Maximum Daily Loads (TMDLs) are developed to direct water quality improvement efforts including changes to allowable bacteria loading by point sources and recommendations for changes to practices that reduce nonpoint-source contributions to bacteria loads. Also, many states have beach monitoring programs to warn swimmers when high levels of indicator bacteria are detected. | 3 | Analytical Chemistry |
Osteryoung was appointed to the faculty at Montana State University in 1967. She moved to Colorado State University a year later, where she worked in the Departments of Civil Engineering and Microbiology. In 1977, Osteryoung moved to the National Science Foundation, where she was the program director for chemical analysis.
Osteryoung was made associate professor at the State University of New York at Buffalo in 1979 and professor in 1982. In 1985 Osteryoung was awarded a Guggenheim Fellowship and spent a year at the University of Southampton, where she investigated the fundamentals of solid electrodes.
Osteryoung moved to North Carolina State University in 1992, where she served as head of department for two years. In 1994, she returned to the National Science Foundation, where she was made director of the division of chemistry. She was the first woman to win the Jacob F. Schoellkopf medal in 1992. | 3 | Analytical Chemistry |
The 16th century marked the beginning of scientific understanding of electricity and magnetism that culminated with the production of electric power and the industrial revolution in the late 19th century.
In the 1550s, English scientist William Gilbert spent 17 years experimenting with magnetism and, to a lesser extent, electricity. For his work on magnets, Gilbert became known as "The Father of Magnetism." His book De Magnete quickly became the standard work throughout Europe on electrical and magnetic phenomena, and made a clear distinction between magnetism and what was then called the "amber effect" (static electricity).
In 1663, German physicist Otto von Guericke created the first electrostatic generator, which produced static electricity by applying friction. The generator was made of a large sulfur ball inside a glass globe, mounted on a shaft. The ball was rotated by means of a crank and a static electric spark was produced when a pad was rubbed against the ball as it rotated. The globe could be removed and used as an electrical source for experiments with electricity. Von Guericke used his generator to show that like charges repelled each other. | 7 | Physical Chemistry |
In polymer chemistry, a comonomer refers to a polymerizable precursor to a copolymer aside from the principal monomer. In some cases, only small amounts of a comonomer are employed, in other cases substantial amounts of comonomers are used. Furthermore, in some cases, the comonomers are statistically incorporated within the polymer chain, whereas in other cases, they aggregate. The distribution of comonomers is referred to as the "blockiness" of a copolymer. | 7 | Physical Chemistry |
War sand is sand contaminated by remains of projectiles used in war. This kind of sand has been found in Normandy, since the invasion of Normandy, among other places. In 1988, the sand on Omaha Beach was discovered to contain man-made metal and glass particles deriving from shrapnel; 4% of the sand in the sample was composed of shrapnel particles ranging in size between and . Researchers also discovered trace amounts of iron and glass beads in the sand, originating from the intense heat unleashed by munitions explosions in the air and sand. | 2 | Environmental Chemistry |
To perform SCODA concentration of DNA molecules, the sample must be embedded in the separation media (gel) in locations where the electrophoretic field is of optimal intensity. This initial translocation of the sample into the optimal concentration position is referred to as "injection". The optimal position is determined by the gel geometry and location of the SCODA driving electrodes. Initially the sample is located in a buffer solution in the sample chamber, adjacent to the concentration gel. Injection is achieved by the application of a controlled DC electrophoretic field across the sample chamber which results in all charged particles being transferred into the concentration gel. To obtain a good stacking of the sample (i.e. tight DNA band) multiple methods can be employed. One example is to exploit the conductivity ratio between the sample chamber buffer and the concentration gel buffer. If the sample chamber buffer has a low conductivity and the concentration gel buffer has a high conductivity this results in a sharp drop off in electric field at the gel-buffer interface which promotes stacking. | 1 | Biochemistry |
Chaotropic agents include:
* Urea 6–8 mol/L
* Guanidinium chloride 6 mol/L
* Lithium perchlorate 4.5 mol/L
* Sodium dodecyl sulfate | 1 | Biochemistry |
Estimation of V̇O max from a timed one-mile track walk in decimal minutes (, e.g.: 20:35 would be specified as 20.58), sex, age in years, body weight in pounds (, lbs), and 60-second heart rate in beats-per-minute (, bpm) at the end of the mile. The constant is 6.3150 for males, 0 for females. | 1 | Biochemistry |
Janot was a French Government Overseas Fellow in 1981 at Churchill College, University of Cambridge. He was also a visiting professor at Sapienza University of Rome. | 8 | Metallurgy |
In 1960, Haines married painter Adrienne Rappaport, who used the name Adrian Rappin professionally. They had one daughter, Avril Haines, an attorney who is serving as the current Director of National Intelligence in the Biden administration. Rappaport died in 1985 after developing chronic obstructive pulmonary disease and later contracting avian tuberculosis.
In 1986, Haines married his current wife, economist [http://www.mcleveland.org/ Mary "Polly" Cleveland].
In 1964, Haines and Rappaport purchased two small run-down rent-controlled apartment buildings on New York's Upper West Side for $140,000, $10,000 down and for a time employed Al Pacino as the building superintendent.
When Haines and Cleveland sold the buildings for many millions of dollars in 2009, they put half the net proceeds into a foundation for the benefit of scientific and economic education. | 1 | Biochemistry |
Plasmalysis is a electrochemical process that requires a voltage source. On the one hand, it describes the plasma-chemical dissociation of organic and inorganic compounds (e.g. C-H and N-H compounds) in interaction with a thermal/non-thermal plasma between two electrodes. On the other hand, it describes the synthesis, i.e. the combination of two or more elements to form a new molecule (e.g. methane synthesis/methanation). Plasmalysis is an artificial word made of plasma and lysis (Greek λύσις, "[dissolution]"). | 7 | Physical Chemistry |
Two dimensional correlation analysis is a mathematical technique that is used to study changes in measured signals. As mostly spectroscopic signals are discussed, sometime also two dimensional correlation spectroscopy is used and refers to the same technique.
In 2D correlation analysis, a sample is subjected to an external perturbation while all other parameters of the system are kept at the same value. This perturbation can be a systematic and controlled change in temperature, pressure, pH, chemical composition of the system, or even time after a catalyst was added to a chemical mixture. As a result of the controlled change (the perturbation), the system will undergo variations which are measured by a chemical or physical detection method. The measured signals or spectra will show systematic variations that are processed with 2D correlation analysis for interpretation.
When one considers spectra that consist of few bands, it is quite obvious to determine which bands are subject to a changing intensity. Such a changing intensity can be caused for example by chemical reactions. However, the interpretation of the measured signal becomes more tricky when spectra are complex and bands are heavily overlapping. Two dimensional correlation analysis allows one to determine at which positions in such a measured signal there is a systematic change in a peak, either continuous rising or drop in intensity. 2D correlation analysis results in two complementary signals, which referred to as the 2D synchronous and 2D asynchronous spectrum. These signals allow amongst others
#to determine the events that are occurring at the same time (in phase) and those events that are occurring at different times (out of phase)
#to determine the sequence of spectral changes
#to identify various inter- and intramolecular interactions
#band assignments of reacting groups
#to detect correlations between spectra of different techniques, for example near infrared spectroscopy (NIR) and Raman spectroscopy | 7 | Physical Chemistry |
One of the first in vitro tests for aspirin was through the Trinder reaction. Aqueous ferric chloride was added to a urine sample, and the formation of the iron complex turned the solution purple. This test was not specific to acetylsalicylic acid but would occur in the presence of any phenol or enol. The downfall of this test occurs in the presence of hyperbilirubinemia or elevated bilirubin. When the level of bilirubin exceeds 1 mg/dl, a false positive could occur. | 3 | Analytical Chemistry |
Most protein separations are performed using a "discontinuous" (or DISC) buffer system that significantly enhances the sharpness of the bands within the gel. During electrophoresis in a discontinuous gel system, an ion gradient is formed in the early stage of electrophoresis that causes all of the proteins to focus into a single sharp band. The formation of the ion gradient is achieved by choosing a pH value at which the ions of the buffer are only moderately charged compared to the SDS-coated proteins. These conditions provide an environment in which Kohlrausch's reactions determine the molar conductivity. As a result, SDS-coated proteins are concentrated to several fold in a thin zone of the order of 19 μm within a few minutes. At this stage all proteins migrate at the same migration speed by isotachophoresis. This occurs in a region of the gel that has larger pores so that the gel matrix does not retard the migration during the focusing or "stacking" event. Separation of the proteins by size is achieved in the lower, "resolving" region of the gel. The resolving gel typically has a much smaller pore size, which leads to a sieving effect that now determines the electrophoretic mobility of the proteins. At the same time, the separating part of the gel also has a pH value in which the buffer ions on average carry a greater charge, causing them to "outrun" the SDS-covered proteins and eliminate the ion gradient and thereby the stacking effect.
A very widespread discontinuous buffer system is the tris-glycine or "Laemmli" system that stacks at a pH of 6.8 and resolves at a pH of ~8.3-9.0. A drawback of this system is that these pH values may promote disulfide bond formation between cysteine residues in the proteins because the pKa of cysteine ranges from 8-9 and because reducing agent present in the loading buffer doesn't co-migrate with the proteins. Recent advances in buffering technology alleviate this problem by resolving the proteins at a pH well below the pKa of cysteine (e.g., bis-tris, pH 6.5) and include reducing agents (e.g. sodium bisulfite) that move into the gel ahead of the proteins to maintain a reducing environment. An additional benefit of using buffers with lower pH values is that the acrylamide gel is more stable at lower pH values, so the gels can be stored for long periods of time before use. | 1 | Biochemistry |
In the investigation of the infrared spectrum of the Galactic Center of the Milky Way, monoxide vibrations of iron carbonyls in interstellar dust clouds were detected. Iron carbonyl clusters were also observed in Jiange H5 chondrites identified by infrared spectroscopy. Four infrared stretching frequencies were found for the terminal and bridging carbon monoxide ligands.
In the oxygen-rich atmosphere of the Earth, metal carbonyls are subject to oxidation to the metal oxides. It is discussed whether in the reducing hydrothermal environments of the prebiotic prehistory such complexes were formed and could have been available as catalysts for the synthesis of critical biochemical compounds such as pyruvic acid. Traces of the carbonyls of iron, nickel, and tungsten were found in the gaseous emanations from the sewage sludge of municipal treatment plants.
The hydrogenase enzymes contain CO bound to iron. It is thought that the CO stabilizes low oxidation states, which facilitates the binding of hydrogen. The enzymes carbon monoxide dehydrogenase and acetyl-CoA synthase also are involved in bioprocessing of CO. Carbon monoxide containing complexes are invoked for the toxicity of CO and signaling. | 0 | Organic Chemistry |
Hormonal imprinting (HI) is a phenomenon which takes place at the first encounter between a hormone and its developing receptor in the critical periods of life (in unicellulars during the whole life) and determines the later signal transduction capacity of the cell. The most important period in mammals is the perinatal one, however this system can be imprinted at weaning, at puberty and in case of continuously dividing cells during the whole life. Faulty imprinting is caused by drugs, environmental pollutants and other hormone-like molecules present in excess at the critical periods with lifelong receptorial, morphological, biochemical and behavioral consequences. HI is transmitted to the hundreds of progeny generations in unicellulars and (as proved) to a few generations also in mammals. | 1 | Biochemistry |
The fluorescent species used in FCS is typically a biomolecule of interest that has been tagged with a fluorophore (using immunohistochemistry for instance), or is a naked fluorophore that is used to probe some environment of interest (e.g. the cytoskeleton of a cell). The following table gives diffusion coefficients of some common fluorophores in water at room temperature, and their excitation wavelengths. | 7 | Physical Chemistry |
Reductive elimination can be induced by oxidizing the metal center to a higher oxidation state via light or an oxidant. | 0 | Organic Chemistry |
Due to its unique stability, chemical properties, and outstanding tunability and reactivity, PPA has been employed in a variety of applications. | 7 | Physical Chemistry |
This method is able to detect as low as 25 μg/ml and up to 2000 μg/ml of protein in a 65 ul sample, using standard protocol.
This method may be preferred for samples containing detergents or other reducing agents.
This method has a fast detection speed and low protein-to-protein variability in comparison to the BCA or Coomassie (Bradford) Assays.
This method has a stable end point. | 1 | Biochemistry |
Poolman pursued studies in Biochemistry and Microbiology at the University of Groningen, the Netherlands, and the University of Bern (Switzerland), obtaining a MSc degree in 1984. He gained his PhD in 1987 with a thesis on bioenergetics of streptococci, under the supervision of Wil Konings and Hans Veldkamp.
After a brief stint as a scientist at Genencor Inc (now Dupont Industrial Biosciences) in San Francisco (USA), he returned to the Netherlands in the end of 1989 to start his own research group on biochemistry and molecular biology of membrane transport at the University of Groningen, supported by a fellowship from the Royal Netherlands Academy of Arts and Sciences. He has been professor of biochemistry at the Groningen since 1998. In 2008 he was appointed Program Director of its Centre for Synthetic Biolog), and in 2013 he became Scientific Director of its Biomolecular Sciences and Biotechnology Institute.
In 1993 Poolman has done a sabbatical at Transgene SA, Strasbourg (France). Thanks to a Fulbright fellowship, he was visiting professor in biochemistry at California Institute of Technology, Pasadena (USA) in 2003.
Poolman has been Chair of the KNAW Earth and Life Sciences Board, and has been vice-chair of KNAW Council for Natural and Technical Sciences since 2017.
From 2016 to 2018, he was a member of the Dutch Council for Physics and Chemistry, and currently he is a member of the core team of the Council for Chemistry.
Since 2009 he led the focus area on ‘Biomolecular and Bioinspired Functionality’ at the Zernike Institute for Advanced Materials (University of Groningen, together with Nobel laureate Ben Feringa, and, from 2010 to 2017, he managed a national Synthetic Biology program of the University of Groningen. | 0 | Organic Chemistry |
Using the KRAKEN autonomous qPCR device, Kraken Sense monitored airport wastewater for the presence of SARS-CoV-2 variants, such as Omicron, and Monkeypox to act as an early warning system for infectious diseases entering the country. This program was funded in part by the National Research Council Canada Industrial Research Assistance Program (NRC IRAP). | 3 | Analytical Chemistry |
While Be(II) is one of the more common oxidation states, there is also further research on a Be(I) and Be(0) complex. Low-valent main group compounds have recently become desirable synthetic targets due to their interesting reactivity comparable to transition metal complexes. In one work, stabilized cyclic (alkyl)(amino)carbene ligands were used to isolate and characterize the first neutral compounds containing beryllium, with the Be(0) compound stabilized by a strongly σ-donating and π-accepting cyclic CAAC ligand.
Be(I) is another example of a rare phenomenon and few publications were reported, but one example of a Be(I) was a CAAC ligand already coordinated with Be. Gilliard and his group created a more stable beryllium radical cation. Because of well-established challenges concerning the reduction of Be(II) to Be(I), they pursued the radical via an oxidation strategy using TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl) oxyl). This reaction resulted in a Be(I) compound just by stabilizing the Be radical. | 0 | Organic Chemistry |
The term blue carbon was coined in 2009. At the time, the term was coined to highlight that coastal vegetated ecosystems have a disproportionately large contribution to global carbon sequestration. Others use the term to describe the carbon captured by the entire ocean, not just the coastal ecosystems. The role of blue carbon in climate change mitigation and adaptation has now reached international prominence.
The vegetated coastal ecosystems of tidal marshes, mangroves and seagrasses (which are grouped as "blue carbon") have high carbon burial rates. This is because they accumulate carbon in their soils and sediments.
Such ecosystems can contribute to climate change mitigation and also to ecosystem-based adaptation. However, when coastal blue carbon ecosystems are degraded or lost they release carbon back to the atmosphere.
Mangroves, salt marshes and seagrasses can store carbon and are highly efficient carbon sinks. They capture from the atmosphere by sequestering the carbon in their underlying sediments, in underground and below-ground biomass, and in dead biomass.
Although vegetated coastal ecosystems cover less area and have less aboveground biomass than terrestrial plants they have the potential to impact long term C sequestration, particularly in sediment sinks.
One of the main concerns with blue carbon is that the rate of loss of these important marine ecosystems is much higher than any other ecosystem on the planet, even compared to rainforests. Current estimates suggest a loss of 2-7% per year, which is not only lost carbon sequestration, but also lost habitat that is important for managing climate, coastal protection, and health.
As habitats that sequester carbon are altered and decreased, that stored amount of C is being released into the atmosphere, continuing the current accelerated rate of climate change. Impacts on these habitats globally will directly and indirectly release the previously stored carbon, which had been sequestered in the sediments of these habitats. Declines in vegetated coastal habitats are seen worldwide.
Quantifying rates of decrease are difficult to calculate, however measurements have been estimated by researchers indicating that if blue carbon ecosystems continue to decline, for any number of reasons, 30-40% of tidal marshes and seagrasses and approximately 100% of mangroves could be gone in the next century.
Reasons for the decline of mangroves, seagrass, and marshes include land use changes, climate and drought related effects, dams built in the watershed, convergence to aquaculture and agriculture, land development and sea-level rise due to climate change. Increases in these activities can lead to significant decreases in habitat availability and thus increases in released C from sediments.
As anthropogenic effects and climate change are heightened, the effectiveness of blue carbon sinks will diminish and CO emissions will be further increased. Data on the rates at which CO is being released into the atmosphere is not robust currently; however, research is being conducted to gather better information to analyze trends. Loss of underground biomass (roots and rhizomes) will allow for CO to be emitted changing these habitats into sources rather than carbon sinks. | 9 | Geochemistry |
As shown in Scheme 1, the ring synthesis of ring C began with a Diels-Alder reaction between diene 1.3 and dienophile 1.1 in the presence of phenylboronic acid (1.2), which, after addition of 2,2-dimethyl-1,3-propanediol, gave five-membered lactone 1.8 in 62% yield. Boron served as a molecular tether and aligned both diene and dienophile for this endo Diels-Alder cycloaddition. After protection of the hydroxyl groups as tert-butyldimethylsilyl ethers, reduction of the ester with lithium aluminium hydride and selective deprotection of the secondary hydroxyl group gave lactone diol 1.11. The unusual lactone hydrates 1.9 and 1.10 were isolated as synthetic intermediates in this process.
Lactone diol 2.1, after selective protection, was reduced with lithium aluminium hydride to give triol 2.4. This triol, after conversion to the acetonide, was selectively oxidized to the aldehyde using tetrapropylammonium perruthenate (TPAP) and N-methylmorpholine N-oxide. Aldehyde 2.6 served as a starting point for the construction of ring B (Scheme 4, compound 4.2). | 0 | Organic Chemistry |
"Radon therapy" is an intentional exposure to radon via inhalation or ingestion. Nevertheless, epidemiological evidence shows a clear link between breathing high concentrations of radon and incidence of lung cancer. | 2 | Environmental Chemistry |
Chitosan is a linear polysaccharide containing linked chitin-derived residues and is widely studied as a biomaterial due to its high compatibility with numerous proteins in the body. Chitosan is cationic and thus electrostatically reacts with numerous proteoglycans, anionic GAGs, and other molecules possessing a negative charge. Since many cytokines and growth factors are linked to GAG, scaffolds with the chitosan-GAG complexes are able to retain these proteins secreted by the adhered cells. Another quality of chitosan that gives it good biomaterial potential is its high charge density in solutions. This allows chitosan to form ionic complexes with many water-soluble anionic polymers, expanding the range of proteins that are able to bind to it and thus expanding its possible uses.
Table 1: Structures, target tissues, and application cell types of chitosan-based scaffolds | 1 | Biochemistry |
Three extreme possibilities have been proposed for the mechanism of NPP-catalyzed phosphoryl transfer. They are distinguished by the sequence in which bonds to phosphorus are made and broken. Though this phenomenon is subtle, it is important for understanding the physiological roles of AP superfamily enzymes, and also to molecular dynamic modeling.
1) A two-step "dissociative" (elimination-addition or D + A) mechanism that proceeds via a trigonal metaphosphate intermediate. This mechanism is represented by the red dashed lines in the figure at right.
2) A two-step "associative" (addition-elimination or A + D) mechanism that proceeds via a pentavalent phosphorane intermediate. This is represented by the blue dashed lines in the figure at right.
3) A one-step fully synchronous mechanism analogous to S2 substitution. Bond formation and breakage occur simultaneously and at the same rate. This is represented by the black dashed line in the figure at right.
The above three cases represent archetypes for the reaction mechanism, and the actual mechanism probably falls somewhere in between them. The red and blue dotted lines in Fig. 2a represent more realistic "concerted" mechanisms in which addition and elimination overlap, but are not fully synchronous. The difference in initial rates of the two steps implies different charge distribution in the transition state (TS).
When the addition step occurs more quickly than elimination (an AD mechanism), more positive charge develops on the nucleophile, and the transition state is said to be "tight." Conversely, if elimination occurs more quickly than addition (DA), the transition state is considered "loose."
López-Canut et al. modeled substitution of a phosphodiester substrate using a hybrid quantum mechanics/molecular mechanics model. Notably, the model predicted an AD concerted mechanism in aqueous solution, but a DA mechanism in the active site of Xac NPP. | 1 | Biochemistry |
Liquid chromatography–mass spectrometry (LC–MS) is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography (or HPLC) with the mass analysis capabilities of mass spectrometry (MS). Coupled chromatography – MS systems are popular in chemical analysis because the individual capabilities of each technique are enhanced synergistically. While liquid chromatography separates mixtures with multiple components, mass spectrometry provides spectral information that may help to identify (or confirm the suspected identity of) each separated component. MS is not only sensitive, but provides selective detection, relieving the need for complete chromatographic separation. LC–MS is also appropriate for metabolomics because of its good coverage of a wide range of chemicals. This tandem technique can be used to analyze biochemical, organic, and inorganic compounds commonly found in complex samples of environmental and biological origin. Therefore, LC–MS may be applied in a wide range of sectors including biotechnology, environment monitoring, food processing, and pharmaceutical, agrochemical, and cosmetic industries. Since the early 2000s, LC–MS (or more specifically LC–MS–MS) has also begun to be used in clinical applications.
In addition to the liquid chromatography and mass spectrometry devices, an LC–MS system contains an interface that efficiently transfers the separated components from the LC column into the MS ion source. The interface is necessary because the LC and MS devices are fundamentally incompatible. While the mobile phase in a LC system is a pressurized liquid, the MS analyzers commonly operate under high vacuum. Thus, it is not possible to directly pump the eluate from the LC column into the MS source. Overall, the interface is a mechanically simple part of the LC–MS system that transfers the maximum amount of analyte, removes a significant portion of the mobile phase used in LC and preserves the chemical identity of the chromatography products (chemically inert). As a requirement, the interface should not interfere with the ionizing efficiency and vacuum conditions of the MS system. Nowadays, most extensively applied LC–MS interfaces are based on atmospheric pressure ionization (API) strategies like electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI). These interfaces became available in the 1990s after a two decade long research and development process. | 3 | Analytical Chemistry |
For an endothermic reaction, heat is absorbed, making the net enthalpy change positive. Thus, according to the definition of the slope:
When the reaction is endothermic, (and the gas constant ), so
Thus, for an endothermic reaction, the Van 't Hoff plot should always have a negative slope. | 7 | Physical Chemistry |
δ-Carotene (delta-carotene) or ε,ψ-carotene is a form of carotene with an ε-ring at one end, and the other uncyclized, labelled ψ (psi). It is an intermediate synthesis product in some photosynthetic plants between lycopene and α-carotene (β,ε-carotene) or ε-carotene (ε,ε-carotene). δ-Carotene is fat soluble. Delta-carotene contains an alpha-ionone instead of a beta-ionone ring; this conversion is carried out by the gene Del which shifts the position of the double bond in the ring structure. The formation delta-carotene under the presence of the Del gene is sensitive to high temperatures. | 1 | Biochemistry |
A sperm donor will usually be required to enter into a contract with a sperm bank to supply their semen, typically for a period of six to twenty-four months depending on the number of pregnancies which the sperm bank intends to produce from the donor. If a sperm bank has access to world markets e.g. by direct sales, or sales to clinics outside their own jurisdiction, a man may donate for a longer period than two years, as the risk of consanguinity is reduced (although local laws vary widely). Some sperm banks with access to world markets impose their own rules on the number of pregnancies which can be achieved in a given regional area or a state or country, and these sperm banks may permit donors to donate for four or five years, or even longer.
The contract may also specify the place and hours for donation, a requirement to notify the sperm bank in the case of acquiring a sexual infection, and the requirement not to have intercourse or to masturbate for a period of usually 2–3 days before making a donation.
The contract may also describe the types of treatment for which the donated sperm may be used, such as artificial insemination and IVF, and whether the donors sperm may be used in surrogacy arrangements. It may also stipulate whether the sperm may be used for research or training purposes. In certain cases, a sperm donor may specify the maximum number of offspring or families which may be produced from the donors sperm. Family may be defined as a couple who may each bear children from the same donor. The contract may also require consent if the donor's samples are to be exported. In the United Kingdom, for example, the maximum number of families for which a donor is permitted to bear children is ten, but a sperm bank or fertility center in the UK may export sperm to other fertility centers so that this may be used to produce more pregnancies abroad. Where this happens, consent must be provided by the donor. Faced with a growing demand for donor sperm, sperm banks may try to maximize the use of a donor whilst still reducing the risk of consanguinity. In legislations with a national register of sperm donors or a national regulatory body, a sperm donor may be required to fill in a separate form of consent which will be registered with the regulatory authority. In the United Kingdom this body is the HFEA.
A sperm donor generally produces and collects sperm at a sperm bank or clinic by masturbation in a private room or cabin, known as a mens production room (UK), donor cabin' (DK) or a masturbatorium (US). Many of these facilities contain pornography such as videos/DVD, magazines, and/or photographs which may assist the donor in becoming aroused in order to facilitate production of the ejaculate, also known as the "semen sample" but the increasing usage of porn in the U.S. has dulled many men to its effects. Often, using any type of personal lubricant, saliva, oil or anything else to lubricate and stimulate the genitals is prohibited as it can contaminate the semen sample and have negative impacts on the quality and health of sperm. In some circumstances, it may also be possible for semen from donors to be collected during sexual intercourse with the use of a collection condom which results in higher sperm counts. | 1 | Biochemistry |
Spinodal decomposition can be modeled using a generalized diffusion equation:
for the chemical potential and the mobility. As pointed out by Cahn, this equation can be considered as a phenomenological definition of the mobility M, which must by definition be positive.
It consists of the ratio of the flux to the local gradient in chemical potential. The chemical potential is a variation of the free energy and when this is the Cahn–Hilliard free energy this is
and so
and now we want to see what happens to a small concentration fluctuation - note that now it has time dependence as a wavevector dependence. Here is a growth rate. If then the perturbation shrinks to nothing, the system is stable with respect to small perturbations or fluctuations, and there is no spinodal decomposition. However, if then the perturbation grows and the system is unstable with respect to small perturbations or fluctuations: There is spinodal decomposition.
Substituting in this concentration fluctuation, we get
This gives the same expressions for the stability as above, but it also gives an expression for the growth rate of concentration perturbations
which has a maximum at a wavevector
So, at least at the beginning of spinodal decomposition, we expect the growing concentrations to mostly have this wavevector. | 7 | Physical Chemistry |
The presence of waters near the freezing point alters the balance of the relative effects of contrasts in salinity and temperature on sea water density. This is described in the equation,
where is the thermal expansion coefficient and is the haline contraction coefficient. In particular, the ratio is crucial. Using the observed temperatures and salinities, in the modern ocean, is about 10 whilst at the LGM it is estimated to have been closer to 25. The modern thermohaline circulation is thus more controlled by density contrasts due to thermal differences, whereas during the LGM the oceans were more than twice as sensitive to differences in salinity rather than temperature. In this way, the thermohaline circulation can be considered to have been less "thermo" and more "haline". | 9 | Geochemistry |
Vesicular monoamine transporter 1 (VMAT1) also known as chromaffin granule amine transporter (CGAT) or solute carrier family 18 member 1 (SLC18A1) is a protein that in humans is encoded by the SLC18A1 gene. VMAT1 is an integral membrane protein, which is embedded in synaptic vesicles and serves to transfer monoamines, such as norepinephrine, epinephrine, dopamine, and serotonin, between the cytosol and synaptic vesicles. SLC18A1 is an isoform of the vesicular monoamine transporter. | 1 | Biochemistry |
The relationship between telomeres and longevity and changing the length of telomeres is one of the new fields of research on increasing human lifespan and even human immortality. Telomeres are sequences at the ends of chromosomes that shorten with each cell division and determine the lifespan of cells. The telomere was first discovered by biologist Hermann Joseph Muller in the early 20th century. However, experiments by Elizabeth Blackburn, Carol Greider, and Jack Szostak in the 1980s led to the successful discovery of telomerase (the enzyme responsible for maintaining telomere length) and a better understanding of telomeres.
Telomeres play essential roles in the stability and control of cell division. Telomeres protect chromosomes from deterioration and fusion with neighboring chromosomes and act as a buffer zone, preventing the loss of essential genetic information during cell division.
It is predicted that the knowledge of methods to increase the length of cell telomeres (Stem cell and quasi-stem cells, control the regeneration and rebuilding of different tissues of the body) will pave the way for increasing human lifespan. Examining telomeres is one of the most important fields of research related to aging. It is also very important to investigate the mechanisms of maintaining telomerase, cell cleansing (old cells that accumulate in tissues and sometimes cause cancer and inflammation) and the production of new cells in long-lived organisms. However, this idea faces major challenges such as increased cancer incidence, immune system problems, and unwanted long-term consequences. | 1 | Biochemistry |
(+)-Discodermolide has also been found to be neuroprotective in recent Alzheimer research. The microtubule-stabilizing feature of (+)-discodermolide was used to restore neuron functions that have been disrupted by the amyloid induced sequestration. Tau protein is known to stabilize the microtubule network in healthy neurons. It served as the “railroad track” upon which actin, tubulin, mitochondria, neurotransmitter-related enzymes and vesicles carrying messenger proteins are delivered. The presence of Amyloid in the cell could lead to tau protein aggregation and microtubule numbers reduction. In transgenic mouse model for human tauopathy, (+)-discodermolide stabilizes microtubules and restores fast axonal transport in cells, offsetting the loss of function caused by aggregation of tau protein. The motor-impaired mice exhibited a full restoration of normal movement with (+)-discodermolide treatment. | 0 | Organic Chemistry |
A variety of non-biological methods can remove nitrate. These include methods that can destroy nitrogen compounds, such as chemical and electrochemical methods, and those that selectively transfer nitrate to a concentrated waste stream, such as ion exchange or reverse osmosis. Chemical removal of nitrate can occur through advanced oxidation processes, although it may produce hazardous byproducts. Electrochemical methods can remove nitrate by via a voltage applied across electrodes, with degradation usually occurring at the cathode. Effective cathode materials include transition metals, post transition metals, and semi-conductors like TiO. Electrochemical methods can often avoid requiring costly chemical additives, but their effectiveness can be constrained by the pH and ions present. Reverse osmosis is highly effective in removing small charged solutes like nitrate, but it may also remove desirable nutrients, create large volumes of wastewater, and require increased pumping pressures. Ion exchange can selectively remove nitrate from water without large waste streams, but do require regeneration and may face challenges with absorption of undesired ions. | 1 | Biochemistry |
Rutledge has held college lectureships at Magdalen College, Oxford, from 2000 to 2001 and Somerville College, Oxford, from 2001 to 2002. In 2003, he moved to become a lecturer at the Centre for Synthesis and Chemical Biology at University College Dublin. In 2006, he relocated to the University of Sydney and was an associate professor during the years 2014 to 2019. In 2019, he was promoted to a full professor of chemistry. At the University of Sydney, Rutledge regularly collaborated with the group of Matthew H. Todd until his departure to University College London in 2018. | 0 | Organic Chemistry |
If the specific rotation, of a pure chiral compound is known, it is possible to use the observed specific rotation, to determine the enantiomeric excess (ee), or "optical purity", of a sample of the compound, by using the formula:
For example, if a sample of bromobutane measured under standard conditions has an observed specific rotation of −9.2°, this indicates that the net effect is due to (9.2°/23.1°)(100%) = 40% of the R enantiomer. The remainder of the sample is a racemic mixture of the enantiomers (30% R and 30% S), which has no net contribution to the observed rotation. The enantiomeric excess is 40%; the total concentration of R is 70%.
However, in practice the utility of this method is limited, as the presence of small amounts of highly rotating impurities can greatly affect the rotation of a given sample. Moreover, the optical rotation of a compound may be non-linearly dependent on its enantiomeric excess because of aggregation in solution. For these reasons other methods of determining the enantiomeric ratio, such as gas chromatography or HPLC with a chiral column, are generally preferred. | 4 | Stereochemistry |
Enterococcus faecalis is an opportunistic, Gram-positive bacteria that forms biofilm in glass. This process is also known as forming a biofilm in vitro. The presence of (Esp), a certain cell surface protein, aids the formation of a biofilm by Enterococcus faecalis. | 1 | Biochemistry |
Chemokine receptors are G protein-coupled receptors containing 7 transmembrane domains that are found on the surface of leukocytes. Approximately 19 different chemokine receptors have been characterized to date, which are divided into four families depending on the type of chemokine they bind; CXCR that bind CXC chemokines, CCR that bind CC chemokines, CX3CR1 that binds the sole CX3C chemokine (CX3CL1), and XCR1 that binds the two XC chemokines (XCL1 and XCL2). They share many structural features; they are similar in size (with about 350 amino acids), have a short, acidic N-terminal end, seven helical transmembrane domains with three intracellular and three extracellular hydrophilic loops, and an intracellular C-terminus containing serine and threonine residues important for receptor regulation. The first two extracellular loops of chemokine receptors each has a conserved cysteine residue that allow formation of a disulfide bridge between these loops. G proteins are coupled to the C-terminal end of the chemokine receptor to allow intracellular signaling after receptor activation, while the N-terminal domain of the chemokine receptor determines ligand binding specificity. | 1 | Biochemistry |
The Society’s alignment groups represent the wide range of interests of the electrochemical and solid state science and technology community. | 7 | Physical Chemistry |
It is the recombinant form of factor VIII, a blood-clotting protein that is administered to patients with the bleeding disorder hemophilia, who are unable to produce factor VIII in quantities sufficient to support normal blood coagulation. Before the development of recombinant factor VIII, the protein was obtained by processing large quantities of human blood from multiple donors, which carried a very high risk of transmission of blood borne infectious diseases, for example HIV and hepatitis B. | 1 | Biochemistry |
Specific techniques must be chosen for the isolation of DNA from some samples. Typical samples with complicated DNA isolation are:
* archaeological samples containing partially degraded DNA, see ancient DNA
* samples containing inhibitors of subsequent analysis procedures, most notably inhibitors of PCR, such as humic acid from the soil, indigo and other fabric dyes or haemoglobin in blood
* samples from microorganisms with thick cellular walls, for example, yeast
*samples containing mixed DNA from multiple sources
Extrachromosomal DNA is generally easy to isolate, especially plasmids may be easily isolated by cell lysis followed by precipitation of proteins, which traps chromosomal DNA in insoluble fraction and after centrifugation, plasmid DNA can be purified from soluble fraction.
A Hirt DNA Extraction is an isolation of all extrachromosomal DNA in a mammalian cell. The Hirt extraction process gets rid of the high molecular weight nuclear DNA, leaving only low molecular weight mitochondrial DNA and any viral episomes present in the cell. | 1 | Biochemistry |
Surface freezing is the appearance of long-range crystalline order in a near-surface layer of a liquid. The surface freezing effect is opposite to a far more common surface melting, or premelting. Surface Freezing was experimentally discovered in melts of alkanes and related chain molecules in the early 1990s independently by two groups. John Earnshaw and his group (Queens University of Belfast) used light scattering, which did not allow a determination of the frozen layers thickness, and whether or not it is laterally ordered. A group led by Ben Ocko (Brookhaven National Laboratory), Eric Sirota (Exxon) and Moshe Deutsch (Bar-Ilan University, Israel) discovered independently the same effect, using x-ray surface diffraction which allowed them to show that the frozen layer is a crystalline monolayer, with molecules oriented roughly along the surface normal, and ordered in an hexagonal lattice. A related effect, the existence of a smectic phase at the surface of a nematic liquid bulk was observed in liquid crystals by Jens Als-Nielsen (Risø National Laboratory, Denmark) and Peter Pershan (Harvard University) in the early 1980s. However, the surface layer there was neither ordered, nor confined to a single layer. Surface freezing has since been found in a wide range of chain molecules and at various interfaces: liquid-air, liquid-solid and liquid-liquid. | 7 | Physical Chemistry |
In order to qualify for SQT assessment chemistry, toxicity, and in situ measurements must be collected synoptically using standardized methods of sediment quality. A control sample is necessary to evaluate impact of contaminated sites. An appropriate reference is a whole sediment sample (particles and associated pore water) collected near area of concern and is representative of background conditions in the absence of contaminants. Evidence of contaminant exposure and biological effect is required in order to assign a site as chemically impacted. | 2 | Environmental Chemistry |
An example of a simple, well-studied sulfinic acid is phenylsulfinic acid. A commercially important sulfinic acid is thiourea dioxide, which is prepared by the oxidation of thiourea with hydrogen peroxide.
:(NH)CS + 2HO → (NH)(NH)CSOH + 2HO
Another commercially important sulfinic acid is hydroxymethyl sulfinic acid, which is usually employed as its sodium salt (HOCHSONa). Called Rongalite, this anion is also commercially useful as a reducing agent. | 0 | Organic Chemistry |
Nod factors (nodulation factors or NF), are signaling molecules produced by soil bacteria known as rhizobia in response to flavonoid exudation from plants under nitrogen limited conditions. Nod factors initiate the establishment of a symbiotic relationship between legumes and rhizobia by inducing nodulation. Nod factors produce the differentiation of plant tissue in root hairs into nodules where the bacteria reside and are able to fix nitrogen from the atmosphere for the plant in exchange for photosynthates and the appropriate environment for nitrogen fixation. One of the most important features provided by the plant in this symbiosis is the production of leghemoglobin, which maintains the oxygen concentration low and prevents the inhibition of nitrogenase activity. | 1 | Biochemistry |
Roasting is a process of heating a sulfide ore to a high temperature in the presence of air. It is a step in the processing of certain ores. More specifically, roasting is often a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component(s). Often before roasting, the ore has already been partially purified, e.g. by froth flotation. The concentrate is mixed with other materials to facilitate the process. The technology is useful in making certain ores usable but it can also be a serious source of air pollution.
Roasting consists of thermal gas–solid reactions, which can include oxidation, reduction, chlorination, sulfation, and pyrohydrolysis. In roasting, the ore or ore concentrate is treated with very hot air. This process is generally applied to sulfide minerals. During roasting, the sulfide is converted to an oxide, and sulfur is released as sulfur dioxide, a gas. For the ores CuS (chalcocite) and ZnS (sphalerite), balanced equations for the roasting are:
:2 CuS + 3 O → 2 CuO + 2 SO
:2 ZnS + 3 O → 2 ZnO + 2 SO
The gaseous product of sulfide roasting, sulfur dioxide (SO) is often used to produce sulfuric acid. Many sulfide minerals contain other components such as arsenic that are released into the environment.
Up until the early 20th century, roasting was started by burning wood on top of ore. This would raise the temperature of the ore to the point where its sulfur content would become its source of fuel, and the roasting process could continue without external fuel sources. Early sulfide roasting was practiced in this manner in "open hearth" roasters, which were manually stirred (a practice called "rabbling") using rake-like tools to expose unroasted ore to oxygen as the reaction proceeded.
This process released large amounts of acidic, metallic, and other toxic compounds. Results of this include areas that even after 60–80 years are still largely lifeless, often exactly corresponding to the area of the roast bed, some of which are hundreds of metres wide by kilometres long. Roasting is an exothermic process. | 8 | Metallurgy |
While most heme proteins are attached to the prosthetic group through iron ion ligation and tertiary interactions, the heme group of cytochrome c makes thioether bonds with two cysteine side chains of the protein. One of the main properties of heme c, which allows cytochrome c to have variety of functions, is its ability to have different reduction potentials in nature. This property determines the kinetics and thermodynamics of an electron transfer reaction. | 1 | Biochemistry |
A solution of 13.0 g (0.1 mol) of 1-octanol in 25 mL of dichloromethane was added dropwise to a solution of 16.1 g (0.1 mol) of diethylaminosulfur trifluoride in 60 mL of dichloromethane cooled to –70° to –65°. The reaction mixture was warmed to 25°, 50 mL of water was added, and the lower organic layer was separated and dried with anhydrous magnesium sulfate and distilled to give 12.0 g (90%) of 1-fluorooctane as a colorless liquid, bp 42–43° (20 mm). F NMR (CClF): -218.8 ppm (tt, J = 49 Hz, J = 25 Hz). | 0 | Organic Chemistry |
1-(4-Chlorophenyl)silatrane is a GABA receptor antagonist and it destroys nervous functions in the central nervous system of vertebrates, primarily in the brain and possibly in the brain stem. It's a rapid acting convulsant, causing convulsions within 1 minute in mice and rats. Death occurred within 5 minutes. It is therefore likely to induce poison shyness. In field trials, it was less effective than zinc phosphide against wild rats. | 1 | Biochemistry |
Graphene membranes are meant to take advantage of their thinness to increase efficiency. Graphene is a singular layer of carbon atoms, so it is about 1000 times thinner than existing membranes. Graphene membranes are around 100 nm thick while current membranes are about 100 µm. Many researchers were concerned with the durability of graphene and if it would be able to handle RO pressures. New research finds that depending on the substrate (a supporting layer that does no filtration and only provides structural support), graphene membranes can withstand 57MPa of pressure which is about 10 times the typical pressures for seawater RO.
Batch RO may offer increased energy efficiency, more durable equipment and higher salinity limits.
The conventional approach claimed that molecules cross the membrane individually. A research team devised a "solution-friction" theory, claiming that molecules in groups through transient pores. Characterizing that process could guide membrane development. The accepted theory is that individual water molecules diffuse through the membrane, termed the "solution-diffusion" model. | 3 | Analytical Chemistry |
In chemistry, a carbazide is a functional group with the general formula RNH-NH(C=O)NH-NHR. They can be derived from the condensation of carbonic acid with a hydrazine. Carbohydrazide is the simplest carbazide, with another common carbazide being diphenylcarbazide, which is used as an analytical reagent.
Diphenylcarbazide forms an intense blue color with chromium in the hexavalent state. It has an absorptivity coefficient of about 3400. That means very small amounts of chromium can be detected; 25 micrograms in 25 mL of solution are too dark to read on a spectral device, so concentrations well below that can be detected. | 0 | Organic Chemistry |
Most class III adenylyl cyclases are transmembrane proteins with 12 transmembrane segments. The protein is organized with 6 transmembrane segments, then the C1 cytoplasmic domain, then another 6 membrane segments, and then a second cytoplasmic domain called C2. The important parts for function are the N-terminus and the C1 and C2 regions. The C1a and C2a subdomains are homologous and form an intramolecular dimer that forms the active site. In Mycobacterium tuberculosis and many other bacterial cases, the AC-III polypeptide is only half as long, comprising one 6-transmembrane domain followed by a cytoplasmic domain, but two of these form a functional homodimer that resembles the mammalian architecture with two active sites. In non-animal class III ACs, the catalytic cytoplasmic domain is seen associated with other (not necessarily transmembrane) domains.
Class III adenylyl cyclase domains can be further divided into four subfamilies, termed class IIIa through IIId. Animal membrane-bound ACs belong to class IIIa. | 1 | Biochemistry |
Several methods of RNA splicing occur in nature; the type of splicing depends on the structure of the spliced intron and the catalysts required for splicing to occur. | 1 | Biochemistry |
The structure has full tetrahedral symmetry and is composed of one heteroatom surrounded by four oxygen atoms to form a tetrahedron. The heteroatom is located centrally and caged by 12 octahedral units linked to one another by the neighboring oxygen atoms. There are a total of 24 bridging oxygen atoms that link the 12 addenda atoms. The metal centres in the 12 octahedra are arranged on a sphere almost equidistant from each other, in four units, giving the complete structure an overall tetrahedral symmetry. The bond length between atoms varies depending on the heteroatom (X) and the addenda atoms (M). For the 12–phosphotungstic acid, Keggin determined the bond length between the heteroatom and each the four central oxygen atoms to be 1.5 Å. The bond length form the central oxygen to the addenda atoms is 2.43 Å. The bond length between the addenda atoms and each of the bridging oxygen is 1.9 Å. The remaining 12 oxygen atoms that are each double bonded to an addenda atom have a bond length of 1.70 Å. The octahedra are therefore distorted. This structure allows the molecule to hydrate and dehydrate without significant structural changes and the molecule is thermally stable in the solid state for use in vapor phase reactions at high temperatures (400−500 °C). | 7 | Physical Chemistry |
This element describes the impedance of a finite-length diffusion with reflective boundary. It is described by the following equation: | 7 | Physical Chemistry |
Dexmethylphenidate has a 4–6 hour duration of effect. A long-acting formulation, Focalin XR, which spans 12 hours is also available and has been shown to be as effective as -TMP (threo-methylphenidate) XR (extended release) (Concerta, Ritalin LA), with flexible dosing and good tolerability. It has also been demonstrated to reduce ADHD symptoms in both children and adults. d-MPH has a similar side-effect profile to MPH and can be administered without regard to food intake. | 4 | Stereochemistry |
For a chemical reaction , the rate equation or rate law is a mathematical expression used in chemical kinetics to link the rate of a reaction to the concentration of each reactant. For a closed system at constant volume, this is often of the form
For reactions that go to completion (which implies very small ), or if only the initial rate is analyzed (with initial vanishing product concentrations), this simplifies to the commonly quoted form
For gas phase reaction the rate equation is often alternatively expressed in terms of partial pressures.
In these equations is the reaction rate coefficient or rate constant, although it is not really a constant, because it includes all the parameters that affect reaction rate, except for time and concentration. Of all the parameters influencing reaction rates, temperature is normally the most important one and is accounted for by the Arrhenius equation.
The exponents and are called reaction orders and depend on the reaction mechanism. For an elementary (single-step) reaction, the order with respect to each reactant is equal to its stoichiometric coefficient. For complex (multistep) reactions, however, this is often not true and the rate equation is determined by the detailed mechanism, as illustrated below for the reaction of H and NO.
For elementary reactions or reaction steps, the order and stoichiometric coefficient are both equal to the molecularity or number of molecules participating. For a unimolecular reaction or step, the rate is proportional to the concentration of molecules of reactant, so the rate law is first order. For a bimolecular reaction or step, the number of collisions is proportional to the product of the two reactant concentrations, or second order. A termolecular step is predicted to be third order, but also very slow as simultaneous collisions of three molecules are rare.
By using the mass balance for the system in which the reaction occurs, an expression for the rate of change in concentration can be derived. For a closed system with constant volume, such an expression can look like | 7 | Physical Chemistry |
SAMP can be prepared in six steps from (S)-proline, and RAMP can be prepared in six steps from (R)-glutamic acid.
<br /> | 4 | Stereochemistry |
Histone Acetyltransferases, also known as HATs, are a family of enzymes that acetylate the histone tails of the nucleosome. This, and other modifications, are expressed based on the varying states of the cellular environment. Many proteins with acetylating abilities have been documented and, after a time, were categorized based on sequence similarities between them. These similarities are high among members of a family, but members from different families show very little resemblance. Some of the major families identified so far are as follows. | 0 | Organic Chemistry |
In physics, colloids are an interesting model system for atoms. Micrometre-scale colloidal particles are large enough to be observed by optical techniques such as confocal microscopy. Many of the forces that govern the structure and behavior of matter, such as excluded volume interactions or electrostatic forces, govern the structure and behavior of colloidal suspensions. For example, the same techniques used to model ideal gases can be applied to model the behavior of a hard sphere colloidal suspension. Phase transitions in colloidal suspensions can be studied in real time using optical techniques, and are analogous to phase transitions in liquids. In many interesting cases optical fluidity is used to control colloid suspensions. | 7 | Physical Chemistry |
The redox (reduction–oxidation) cell is a reversible cell in which redox-active species are in fluid (liquid or gas) media. Redox flow batteries are rechargeable (secondary) cells. Because they employ heterogeneous electron transfer rather than solid-state diffusion or intercalation they are more similar to fuel cells rather than to conventional batteries (such as lead–acid or lithium-ion). The main reason fuel cells are not considered to be batteries, is because originally (in the 1800s) fuel cells emerged as a means to produce electricity directly from fuels (and air) via a non-combustion electrochemical process. Later, particularly in the 1960s and 1990s, rechargeable fuel cells (i.e. /, such as unitized regenerative fuel cells in NASA's Helios Prototype) were developed.
Examples of redox flow batteries are the vanadium redox flow battery, polysulfide–bromide battery (Regenesys), iron redox flow battery (IRFB), and uranium redox flow battery. Redox fuel cells are less common commercially although many systems have been proposed.
Vanadium redox flow batteries are the most marketed flow batteries at present, due to the advantages they provide over other chemistries, despite limited energy and power densities. Since they use vanadium at both electrodes, they do not suffer cross-contamination. The limited solubility of vanadium salts, however, offsets this advantage in practice. More importantly for the commercial success of VRFBs is actually an almost perfect match of the voltage window of carbon/aqueous acid interface with the working voltage range of the vanadium redox-couples. This assures the durability of the low-cost carbon electrodes and low-impact of side reactions, such as H2 and O2 evolutions, resulting in record-long calendar (many years) and cycle(15,000–20,000 cycles) lives, which in turn results in a record low levelized cost of energy (LCOE, i.e. the system cost divided by the usable energy, the cycle life, and round-trip efficiency). The long lifetimes of flow batteries allow for the amortization of their relatively high capital cost (due to vanadium, carbon felts, bipolar plates, membranes). The levelized cost of energy for VRFBs is in the order of a few tens of $ cents or € cents per kWh, much lower than of solid-state batteries and not so far from the targets of $0.05 and €0.05, stated by US and EC government agencies. The major challenges for the broad implementation include: low abundance and high costs of VO (> $30 / Kg), the raw materials for VRFB; parasite reactions including hydrogen and oxygen evolution; and precipitation of VO during cycling. It is the major driving force to develop alternative flow battery technologies.
Traditional flow battery chemistries have both low specific energy (which makes them too heavy for fully electric vehicles) and low specific power (which makes them too expensive for stationary energy storage). However a high power of 1.4 W/cm was demonstrated for hydrogen–bromine flow batteries, and a high specific energy (530 Wh/kg at the tank level) was shown for hydrogen–bromate flow batteries | 7 | Physical Chemistry |
Carbon steels exposed to hydrogen at high temperatures experience high temperature hydrogen attack which leads to internal decarburization and weakening. | 8 | Metallurgy |
A case study by Beale et al. involved preparation of iron phosphates and bismuth molybdate catalysts from an amorphous precursor gel. The study found that there were no intermediate phases in the reaction, and helped to determine kinetic and structural information. The article uses the dated term in-situ, but the experiment uses, in essence, an operando method. Although x-ray diffraction does not count as a spectroscopy method, it is often being used as an operando method in various fields, including catalysis. | 7 | Physical Chemistry |
Specific weight is often used as a property of soil to solve earthwork problems.
In soil mechanics, specific weight may refer to: | 7 | Physical Chemistry |
As PECT materials exhibit a change in voltage upon application of strain, it is possible to calibrate this change in voltage to the level of strain in a material. This has been proposed for applications in battery health monitoring, as well as structural health monitoring. | 7 | Physical Chemistry |
Silicon carbide is used in carborundum printmaking – a collagraph printmaking technique. Carborundum grit is applied in a paste to the surface of an aluminium plate. When the paste is dry, ink is applied and trapped in its granular surface, then wiped from the bare areas of the plate. The ink plate is then printed onto paper in a rolling-bed press used for intaglio printmaking. The result is a print of painted marks embossed into the paper.
Carborundum grit is also used in stone Lithography. Its uniform particle size allows it to be used to "Grain" a stone which removes the previous image. In a similar process to sanding, coarser grit Carborundum is applied to the stone and worked with a Levigator, typically a round plate eccentric on a perpendicular shaft, then gradually finer and finer grit is applied until the stone is clean. This creates a grease sensitive surface. | 8 | Metallurgy |
Once a substitution is made on a parent molecule, its structural symmetry is usually reduced, meaning that atoms that were formerly equivalent may no longer be so. Thus substitution of two or more equivalent atoms by the same element may generate more than one positional isomer.
The classical example is the derivatives of benzene. Its six hydrogens are all structurally equivalent, and so are the six carbons; because the structure is not changed if the atoms are permuted in ways that correspond to flipping the molecule over or rotating it by multiples of 60 degrees. Therefore, replacing any hydrogen by chlorine yields only one chlorobenzene. However, with that replacement, the atom permutations that moved that hydrogen are no longer valid. Only one permutation remains, that corresponds to flipping the molecule over while keeping the chlorine fixed. The five remaining hydrogens then fall into three different equivalence classes: the one opposite to the chlorine is a class by itself (called the para position), the two closest to the chlorine form another class (ortho), and the remaining two are the third class (meta). Thus a second substitution of hydrogen by chlorine can yield three positional isomers: 1,2- or ortho-, 1,3- or meta-, and 1,4- or para-dichlorobenzene.
For the same reason, there is only one phenol (hydroxybenzene), but three benzenediols; and one toluene (methylbenzene), but three toluols, and three xylenes.
On the other hand, the second replacement (by the same substituent) may preserve or even increase the symmetry of the molecule, and thus may preserve or reduce the number of equivalence classes for the next replacement. Thus, the four remaining hydrogens in meta-dichlorobenzene still fall into three classes, while those of ortho- fall into two, and those of para- are all equivalent again. Still, some of these 3 + 2 + 1 = 6 substitutions end up yielding the same structure, so there are only three structurally distinct trichlorobenzenes: 1,2,3-, 1,2,4-, and 1,3,5-.
If the substituents at each step are different, there will usually be more structural isomers. Xylenol, which is benzene with one hydroxyl substituent and two methyl substituents, has a total of 6 isomers: | 4 | Stereochemistry |
NMOR is generally not used intentionally, but is instead created by the nitrosation of morpholine or morpholine derivatives which are used for several industrial purposes. | 0 | Organic Chemistry |
UV curing is used for converting or curing inks, adhesives, and coatings. UV-cured adhesive has become a high speed replacement for two-part adhesives, eliminating the need for solvent removal, ratio mixing, and potential life concern. It is used in flexographic, offset, pad, and screen printing processes; where UV curing systems are used to polymerize images on screen-printed products, ranging from T-shirts to 3D and cylindrical parts. It is used in fine instrument finishing (guitars, violins, ukuleles, etc.), pool cue manufacturing and other wood craft industries. Printing with UV curable inks provides the ability to print on a very wide variety of substrates such as plastics, paper, canvas, glass, metal, foam boards, tile, films, and many other materials.
Industries that use UV curing include medicine, automobiles, cosmetics (for example artificial fingernails and gel nail polish), food, science, education, and art. UV curable inks have successfully met the demands of the publication sector in terms of print quality, durability, and compatibility with different substrates, making them a suitable choice for printing applications in this industry. | 5 | Photochemistry |
László Tisza (July 7, 1907 – April 15, 2009) was a Hungarian-born American physicist who was Professor of Physics Emeritus at MIT. He was a colleague of famed physicists Edward Teller, Lev Landau and Fritz London, and initiated the two-fluid theory of liquid helium. | 7 | Physical Chemistry |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.