Organic silicon derivatives used to characterize hydroxysteroids, nucleosides, and related compounds. Trimethylsilyl esters of amino acids are used in peptide synthesis.

A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.

Fractionation of a vaporized sample as a consequence of partition between a mobile gaseous phase and a stationary phase held in a column. Two types are gas-solid chromatography, where the fixed phase is a solid, and gas-liquid, in which the stationary phase is a nonvolatile liquid supported on an inert solid matrix.

Acetals are chemical compounds formed when a carbonyl group (aldehyde or ketone) reacts with two equivalents of alcohol in the presence of a strong acid, resulting in the formation of a stable carbon-carbon bond and producing water as a byproduct.

Compounds similar to hydrocarbons in which a tetravalent silicon atom replaces the carbon atom. They are very reactive, ignite in air, and form useful derivatives.

Iodinated hydrocarbons are organic compounds containing carbon and hydrogen atoms, with iodine atoms covalently bonded to them, which are used in medical imaging as radiocontrast agents.

Organic compounds containing the carboxy group (-COOH). This group of compounds includes amino acids and fatty acids. Carboxylic acids can be saturated, unsaturated, or aromatic.

Microbial, plant, or animal cells which are immobilized by attachment to solid structures, usually a column matrix. A common use of immobilized cells is in biotechnology for the bioconversion of a substrate to a particular product. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)

Neutral glycosphingolipids that contain a monosaccharide, normally glucose or galactose, in 1-ortho-beta-glycosidic linkage with the primary alcohol of an N-acyl sphingoid (ceramide). In plants the monosaccharide is normally glucose and the sphingoid usually phytosphingosine. In animals, the monosaccharide is usually galactose, though this may vary with the tissue and the sphingoid is usually sphingosine or dihydrosphingosine. (From Oxford Dictionary of Biochemistry and Molecular Biology, 1st ed)

A trace element that constitutes about 27.6% of the earth's crust in the form of SILICON DIOXIDE. It does not occur free in nature. Silicon has the atomic symbol Si, atomic number 14, and atomic weight [28.084; 28.086].

'Ketones' are organic compounds with a specific structure, characterized by a carbonyl group (a carbon double-bonded to an oxygen atom) and two carbon atoms, formed as byproducts when the body breaks down fats for energy due to lack of glucose, often seen in diabetes and starvation states.

The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)

A plant genus of the family MYRTACEAE that bears an edible fruit and contains guavin B and quercetin glycosides.

Salts that melt below 100 C. Their low VOLATILIZATION can be an advantage over volatile organic solvents.

An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.

'Ethers' in a medical context are a class of organic compounds used as medication, particularly as an inhalational agent to induce and maintain general anesthesia, characterized by their ability to produce a state of unconsciousness while providing muscle relaxation and analgesia.

Chromatography on thin layers of adsorbents rather than in columns. The adsorbent can be alumina, silica gel, silicates, charcoals, or cellulose. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.

Pyrolysis of organic compounds at the temperature of a hydrogen-air flame to produce ionic intermediates which can be collected and the resulting ion current measured by gas chromatography.

Alkyl compounds containing a hydroxyl group. They are classified according to relation of the carbon atom: primary alcohols, R-CH2OH; secondary alcohols, R2-CHOH; tertiary alcohols, R3-COH. (From Grant & Hackh's Chemical Dictionary, 5th ed)

Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)

Analogs or derivatives of morphine.

CHOLESTENES with one or more double bonds and substituted by any number of keto groups.

Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)

Derivatives of BENZOIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxybenzene structure.

Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).

Detection of drugs that have been abused, overused, or misused, including legal and illegal drugs. Urine screening is the usual method of detection.

A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.

A series of steps taken in order to conduct research.

The composition, conformation, and properties of atoms and molecules, and their reaction and interaction processes.