High Quality Content by WIKIPEDIA articles! A hydrogen bond is the electromagnetic attractive interaction of a polar hydrogen atom in a molecule or chemical group and an electronegative atom, such as nitrogen, oxygen or fluorine, from another molecule or chemical group. It is not a covalent chemical bond. The hydrogen atom has an attraction to another electronegative atom. These attractions can occur between molecules (intermolecularly), or within different parts of a single molecule (intramolecularly). The hydrogen bond (5 to 30 kJ/mole) is stronger than a van der Waals interaction, but weaker than covalent or ionic bonds. This type of bond occurs in both inorganic molecules such as water and organic molecules like DNA and proteins.
High Quality Content by WIKIPEDIA articles! In chemistry, a hydronium ion is the cation H3O+, a type of oxonium ion produced by protonation of water. This cation is often used to represent the nature of the proton in aqueous solution, where the proton is highly solvated (bound to a solvent). The reality is far more complicated, and a proton is bound to several molecules of water, such that other descriptions such as H5O2+, H7O3+ and H9O4+ are increasingly accurate description of the environment of a proton in water. The ion H3O+ has been detected in the gas phase.
High Quality Content by WIKIPEDIA articles! (2S,4R)-4-Hydroxyproline, or L-hydroxyproline (C5H9O3N), is a common non-proteinogenic amino acid, abbreviated as HYP, e.g., in Protein Data Bank.
High Quality Content by WIKIPEDIA articles! A hydroxyanthraquinone is any of several organic compounds with formula C14H9O2(OH), which can be viewed as derivatives of an anthraquinone through replacement of one hydrogen atom (H) by an hydroxyl group (-OH). The IUPAC nomenclature recommends hydroxyanthracenedione.
High Quality Content by WIKIPEDIA articles! Hydroxy-1,4-benzoquinone, also called hydroxy-para-benzoquinone, is an organic compound with formula C6H4O3, formally derived from 1,4-Benzoquinone by replacing one hydrogen atom with a hydroxyl (OH) group. It is one of three hydroxybenzoquinone isomers and one of the simplest hydroxyquinones.
High Quality Content by WIKIPEDIA articles! Hydroxycarbamide (INN) or hydroxyurea (brand names include Hydrea and Droxia) is an antineoplastic drug, first synthesized in 1869, used in myeloproliferative disorders, specifically polycythemia vera and essential thrombocythemia. It is also used to reduce the rate of painful attacks in sickle-cell disease and has antiretroviral properties in diseases such as AIDS.
High Quality Content by WIKIPEDIA articles! A hydrogen infrastructure is the infrastructure of pipes and stations for distribution and sale of hydrogen fuel.
High Quality Content by WIKIPEDIA articles! The hydroxyl radical, •HO, is the neutral form of the hydroxide ion (HO–). Hydroxyl radicals are highly reactive and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides (ROHO) or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. It is also an important radical formed in radiation chemistry, since it leads to the formation of hydrogen peroxide and oxygen, which can enhance corrosion and SCC in coolant systems subjected to radioactive environments. Hydroxyl radicals are also produced during UV-light dissociation of H2O2 (suggested in 1879) and...
High Quality Content by WIKIPEDIA articles! A hydroxynaphthoquinone is any of several organic compounds with formula C10H6O3, which can be viewed as derivatives of a naphthoquinone through replacement of one hydrogen atom (H) by an hydroxyl group (-OH).
High Quality Content by WIKIPEDIA articles! Hydroxymethylfurfural (HMF), also 5-(Hydroxymethyl)furfural, is an organic compound derived from dehydration of certain sugars. This yellow low-melting solid is highly water-soluble. The molecule consists of a furan ring, containing both aldehyde and alcohol functional groups. HMF has been identified in a wide variety of heat-processed foods including milk, fruit juices, spirits, honey, etc. HMF, which is derived from cellulose without use of fermentation, is a potential "carbon-neutral" feedstock for fuels and chemicals.
High Quality Content by WIKIPEDIA articles! Hydrogenolysis is a chemical reaction whereby a carbon–carbon or carbon–heteroatom single bond is cleaved or undergoes "lysis" by hydrogen. The heteroatom may vary, but it usually is oxygen, nitrogen, or sulfur. A related reaction is hydrogenation, where hydrogen is added to the molecule, without cleaving bonds. Usually hydrogenolysis is conducted catalytically using hydrogen gas.
High Quality Content by WIKIPEDIA articles! Hydroxychloroquine is an antimalarial drug, sold under the trade names Plaquenil,Axemal(In India), Dolquine, and Quensyl, also used to reduce inflammation in the treatment of rheumatoid arthritis (see disease-modifying antirheumatic drugs) and lupus. Hydroxychloroquine differs from chloroquine by the presence of a hydroxyl group at the end of the side chain: The N-ethyl substituent is beta-hydroxylated. It is available for oral administration as hydroxychloroquine sulfate (plaquenil) of which 200 mg contains 155 mg base in chiral form. Hydroxychloroquine has similar pharmacokinetics to chloroquine, with quick gastrointestinal absorption and is eliminated by the kidney. Cytochrome P450 enzymes...
High Quality Content by WIKIPEDIA articles! The hydrogen economy is a proposed system of delivering energy using hydrogen. The term hydrogen economy was coined by John Bockris during a talk he gave in 1970 at General Motors (GM) Technical Center.
High Quality Content by WIKIPEDIA articles! A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in different chemical combinations.
High Quality Content by WIKIPEDIA articles! In particle physics, a hyperon is any baryon containing one or more strange quarks, but no charm quarks or bottom quarks.
High Quality Content by WIKIPEDIA articles! Hypercalcaemia (British English) or hypercalcemia (American English) is an elevated calcium level in the blood. (Normal range: 9–10.5 mg/dL or 2.2–2.6 mmol/L). It can be an asymptomatic laboratory finding, but because an elevated calcium level is often indicative of other diseases, a workup should be undertaken if it persists. It can be due to excessive skeletal calcium release, increased intestinal calcium absorption, or decreased renal calcium excretion.
High Quality Content by WIKIPEDIA articles! In medicine, hypocalcaemia (or hypocalcemia) is the presence of low serum calcium levels in the blood, usually taken as less than 2.1 mmol/L or 9 mg/dl or an ionized calcium level of less than 1.1 mmol/L or 4.5 mg/dL. It is a type of electrolyte disturbance. In the blood, about half of all calcium is bound to proteins such as serum albumin, but it is the unbound, or ionized, calcium that the body regulates. If a person has abnormal levels of blood proteins, then the plasma calcium may be inaccurate. The ionized calcium level is considered more clinically accurate in this case. In the setting of low serum albumin (frequently seen in patients with chronic diseases, hepatic disease or even...
High Quality Content by WIKIPEDIA articles! Hypokalemia (American English) or hypokalaemia (British English), also hypopotassemia or hypopotassaemia (ICD-9), refers to the condition in which the concentration of potassium (K+) in the blood is low. The prefix hypo- means "under" (contrast with hyper-, meaning "over"); kal- refers to kalium, the Neo-Latin for potassium, and -emia means "condition of the blood."
High Quality Content by WIKIPEDIA articles! Hypomagnesemia (or hypomagnesaemia) is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.7 mmol/L is used as reference. The prefix hypo- means low (contrast with hyper-, meaning high). The middle `magnes` refers to magnesium. The end portion of the word, -emia, means `in the blood.`
High Quality Content by WIKIPEDIA articles! Hypomagnesemia with secondary hypocalcemia (HSH) is an autosomal recessive genetic disorder affecting intestinal magnesium absorption. Decreased intestinal magnesium reabsorption and the resulting decrease in serum magnesium levels is believed to cause lowered parathyroid hormone (PTH) output by the parathyroid gland. This results in decreased PTH and decreased serum calcium levels (hypocalcemia). This manifests in convulsions and spasms in early infancy which, if left untreated, can lead to mental retardation or death. HSH is caused by mutations in the TRPM6 gene.