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Taurine Metabolism
Taurine (), or 2-aminoethanesulfonic acid, is an organic compound that is widely distributed in animal tissues. It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight. It is named after Latin (cognate to Ancient Greek ταῦρος, ''taûros'') meaning bull or ox, as it was first isolated from ox bile in 1827 by German scientists Friedrich Tiedemann and Leopold Gmelin. It was discovered in human bile in 1846 by Edmund Ronalds. It has many biological roles, such as conjugation of bile acids, antioxidation, osmoregulation, membrane stabilization, and modulation of calcium signaling. It is essential for cardiovascular function, and development and function of skeletal muscle, the retina, and the central nervous system. It is an unusual example of a naturally occurring sulfonic acid. Chemical and biochemical features Taurine exists as a zwitterion , as verified by X-ray crystallography. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfamic Acid
Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, sulphamic acid and sulfamidic acid, is a molecular compound with the formula H3NSO3. This colourless, water-soluble compound finds many applications. Sulfamic acid melts at 205 °C before decomposing at higher temperatures to water, sulfur trioxide, sulfur dioxide and nitrogen. Sulfamic acid (H3NSO3) may be considered an intermediate compound between sulfuric acid (H2SO4), and sulfamide (H4N2SO2), effectively replacing a hydroxyl (–OH) group with an amine (–NH2) group at each step. This pattern can extend no further in either direction without breaking down the sulfonyl (–SO2–) moiety. Sulfamates are derivatives of sulfamic acid. Production Sulfamic acid is produced industrially by treating urea with a mixture of sulfur trioxide and sulfuric acid (or oleum). The conversion is conducted in two stages, the first being sulfamation: :OC(NH2)2 + SO3 → OC(NH2)(NHSO3H) :OC(NH2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Signaling
Calcium signaling is the use of calcium ions (Ca2+) to communicate and drive intracellular processes often as a step in signal transduction. Ca2+ is important for cellular signalling, for once it enters the cytosol of the cytoplasm it exerts allosteric regulatory effects on many enzymes and proteins. Ca2+ can act in signal transduction resulting from activation of ion channels or as a second messenger caused by indirect signal transduction pathways such as G protein-coupled receptors. Concentration regulation The resting concentration of Ca2+ in the cytoplasm is normally maintained around 100 nM. This is 20,000- to 100,000-fold lower than typical extracellular concentration. To maintain this low concentration, Ca2+ is actively pumped from the cytosol to the extracellular space, the endoplasmic reticulum (ER), and sometimes into the mitochondria. Certain proteins of the cytoplasm and organelles act as buffers by binding Ca2+. Signaling occurs when the cell is stimulated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfurous Acid
Sulfurous acid (also sulfuric(IV) acid, sulphurous acid (UK), sulphuric(IV) acid (UK)) is the chemical compound with the formula . There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase. The conjugate bases of this elusive acid are, however, common anions, bisulfite (or hydrogen sulfite) and sulfite. Sulfurous acid is an intermediate species in the formation of acid rain from sulfur dioxide. Raman spectra of solutions of sulfur dioxide in water show only signals due to the molecule and the bisulfite ion, . The intensities of the signals are consistent with the following equilibrium: 17O NMR spectroscopy provided evidence that solutions of sulfurous acid and protonated sulfites contain a mixture of isomers, which is in equilibrium: Attempts to concentrate the solutions of sulfurous acid simply reverses the equilibrium, producing sulfur dioxde and water vapor. A clathrate with the formul a has been crystallised. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aziridine
Aziridine is an organic compound consisting of the three-membered heterocycle . It is a colorless, toxic, volatile liquid that is of significant practical interest. Aziridine was discovered in 1888 by the chemist Siegmund Gabriel. Its derivatives, also referred to as aziridines, are of broader interest in medicinal chemistry. Structure The bond angles in aziridine are approximately 60°, considerably less than the normal hydrocarbon bond angle of 109.5°, which results in angle strain as in the comparable cyclopropane and ethylene oxide molecules. A banana bond model explains bonding in such compounds. Aziridine is less basic than acyclic aliphatic amines, with a pKa of 7.9 for the conjugate acid, due to increased s character of the nitrogen free electron pair. Angle strain in aziridine also increases the barrier to nitrogen inversion. This barrier height permits the isolation of separate ''invertomers'', for example the ''cis'' and ''trans'' invertomers of ''N''-chloro- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Bisulfite
Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO3. Sodium bisulfite in fact is not a real compound, but a mixture of salts that dissolve in water to give solutions composed of sodium and bisulfite ions. It appears in form of white or yellowish-white crystals with an odor of sulfur dioxide. For properties of sodium bisulfite, refer to the table located to the right. Regardless of its ill-defined nature, sodium bisulfite is used in many different industries such a food additive with E number E222 in the food industry, a reducing agent in the cosmetic industry, and a decomposer of residual hypochlorite used in the bleaching industry. Synthesis Sodium bisulfite solutions can be prepared by treating a solution of suitable base, such as sodium hydroxide or sodium bicarbonate with sulfur dioxide. :SO2 + NaOH → NaHSO3 :SO2 + NaHCO3 → NaHSO3 + CO2 Attempts to crystallize the product yield Sodium me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethylene Oxide
Ethylene oxide is an organic compound with the chemical formula, formula . It is a cyclic ether and the simplest epoxide: a three-membered Ring (chemistry), ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sweet odor. Because it is a strained ring, ethylene oxide easily participates in a number of addition reactions that result in ring-opening. Ethylene oxide is isomeric with acetaldehyde and with vinyl alcohol. Ethylene oxide is industrially produced by oxidation of ethylene in the presence of silver catalyst. The reactivity that is responsible for many of ethylene oxide's hazards also makes it useful. Although too dangerous for direct household use and generally unfamiliar to consumers, ethylene oxide is used for making many consumer products as well as non-consumer chemicals and intermediates. These products include detergents, thickeners, solvents, plastics, and various organic chemicals such as ethylene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isethionic Acid
Isethionic acid is an organosulfur compound containing an alkane, alkylsulfonic acid located beta to a hydroxyl, hydroxy group. Its discovery is generally attributed to Heinrich Gustav Magnus, who prepared it by the action of solid sulfur trioxide on ethanol in 1833. It is a white solubility, water-soluble solid used in the manufacture of certain surfactants and in the industrial production of taurine. It is most commonly available in the form of its sodium salt (Sodium 2-hydroxyethyl sulfonate, sodium isethionate). Synthesis Its original synthesis, by the reaction of sulfur trioxide on ethanol, has largely been surpassed. It may be produced by the hydrolysis of carbyl sulfate, which is obtained by the sulfonation of ethylene. : However the most common route is the reaction of ethylene oxide with aqueous sodium bisulfite, which produces the sodium salt (Sodium 2-hydroxyethyl sulfonate, sodium isethionate): : Reactions Isethionic acid is used as a starting material in the indust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonolysis
In chemistry, ammonolysis (/am·mo·nol·y·sis/) is the process of splitting ammonia into NH2- + H+. Ammonolysis reactions can be conducted with organic compounds to produce amines (molecules containing a nitrogen atom with a lone pair, :N), or with inorganic compounds to produce nitrides. This reaction is analogous to hydrolysis in which water molecules are split. Similar to water, liquid ammonia also undergoes auto-ionization, , where the rate constant is k = 1.9*10^-38. Organic compounds such as alkyl halides, hydroxyls (hydroxyl nitriles and carbohydrates), carbonyl (aldehydes/ketones/esters/alcohols), and sulfur (sulfonyl derivatives) can all undergo ammonolysis in liquid ammonia. Organic synthesis Mechanism: ammonolysis of esters This mechanism is similar to the hydrolysis of esters, the ammonia attacks the electrophilic carbonyl carbon forming a tetrahedral intermediate. The reformation of the C-O double bond ejects the ester. The alkoxide deprotonates the ammonia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among various mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zwitterion
In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively-charged functional groups. : With amino acids, for example, in solution a chemical equilibrium will be established between the "parent" molecule and the zwitterion. Betaines are zwitterions that cannot isomerize to an all-neutral form, such as when the positive charge is located on a quaternary ammonium group. Similarly, a molecule containing a phosphonium group and a carboxylate group cannot isomerize. Amino acids The equilibrium is established in two stages. In the first stage, a proton is transferred from the carboxyl group to a water molecule: :H2N(R)CO2H + H2O H2N(R)CO2- + H3O+ In the second stage, a proton is transferred from the hydronium ion to the amine group: :H2N(R)CO2- + H3O+ H3N+ (R)CO2- + H2O Overall, the reaction is an isomerization reaction :H2N(R)CO2H H3N+ (R)CO2- The ratio of the concentrations of the two spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfonic Acid
In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound (with the organic substituent replaced by hydrogen) is the parent sulfonic acid, , a tautomer of sulfurous acid, . Salt (chemistry), Salts or esters of sulfonic acids are called sulfonates. Preparation Aryl sulfonic acids are produced by the process of sulfonation. Usually the sulfonating agent is sulfur trioxide. A large scale application of this method is the production of alkylbenzenesulfonic acids: :RC6H5 + SO3 -> RC6H4SO3H In this reaction, sulfur trioxide is an electrophile and the arene is the nucleophile. The reaction is an example of electrophilic aromatic substitution. Alkyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central Nervous System
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric and triploblastic animals—that is, all multicellular animals except sponges and diploblasts. It is a structure composed of nervous tissue positioned along the rostral (nose end) to caudal (tail end) axis of the body and may have an enlarged section at the rostral end which is a brain. Only arthropods, cephalopods and vertebrates have a true brain (precursor structures exist in onychophorans, gastropods and lancelets). The rest of this article exclusively discusses the vertebrate central nervous system, which is radically distinct from all other animals. Overview In vertebrates, the brain and spinal cord are both enclosed in the meninges. The meninges provide a barrier to chemicals dissolv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
