| active metal | <chemistry> Any very reactive metal, such as magnesium or sodium, most are located in the first two columns of the periodic table. (15 Jan 1998) |
|---|---|
| active methionine | S-(5'-deoxy-5'-adenosyl)-l-methionine;condensation product of adenosine and l-methionine involving replacement of the -OPO3H2 of adenylic acid by -S+ (CH3)CH2CH2CH(NH3+)CO 2 of methionine; a sulfonium compound bearing a methyl group that is transferred in transmethylation reactions. See: methionine adenosyltransferase. Synonym: active methionine. Acronym: SAM (05 Mar 2000) |
| active methyl | A methyl group attached to a quaternary ammonium ion or a tertiary sulfonium ion that can take part in transmethylation reactions; e.g., methyl groups in choline and in S-adenosyl-l-methionine, which are thus methyl donors. (05 Mar 2000) |
| active movement | Movement effected by the organism itself, unaided by external influences. (05 Mar 2000) |
| active mutant | A mutant with overt phenotypic expression. (05 Mar 2000) |
| active placebo | <pharmacology> Any dummy medical treatment, originally, a medicinal preparation having no specific pharmacological activity against the patients illness or complaint given solely for the psychophysiological effects of the treatment, more recently, a dummy treatment administered to the control group in a controlled clinical trial in order that the specific and non-specific effects of the experimental treatment can be distinguished i.e., the experimental treatment must produce better results than the placebo in order to be considered effective. (18 Nov 1997) |
| active principle | A constituent of a drug, usually an alkaloid or glycoside, upon the presence of which the characteristic therapeutic action of the substance largely depends. (05 Mar 2000) |
| active prophylaxis | Use of an antigenic (immunogenic) agent to actively stimulate the immunological mechanism. (05 Mar 2000) |
| active psychoanalysis | Psychoanalysis in which the analyst intervenes directly and actively in the patient's life, e.g., by making prohibitions, assigning tasks. (05 Mar 2000) |
| active pyruvate | An intermediate formed in the oxidative decarboxylation of pyruvate. Compare: pyruvate dehydrogenase (lipoamide). Synonym: alpha-lactyl-thiamin pyrophosphate. (05 Mar 2000) |
| active repressor | A repressor that combines directly with an operator gene to repress the operator and its structural genes, thus repressing protein synthesis; active repressor may be repressed by an inducer, with resulting protein synthesis; a homeostatic mechanism for regulation of inducible enzyme systems. (05 Mar 2000) |
| active site | <chemistry> A specific region of an enzyme where a substrate binds and catalysis takes place (binding site). (06 May 1997) |
| active splint | A splint utilizing springs or elastic bands that aids in movements initiated by the patient by controlling the plane and range of motion. Synonym: active splint, functional splint. (05 Mar 2000) |
| active succinate | The condensation product of succinic acid and CoA; one of the intermediates of the tricarboxylic acid cycle and a precursor in the synthesis of haem. Synonym: active succinate, succinyl-CoA. (05 Mar 2000) |
| active sulfate | 3'-phosphoadenosine 5'-phosphosulfate;an intermediate in the formation of urinary ethereal sulfates, notable for containing a "high energy" sulfate bond; the 3'-OH of adenosine is replaced by -OPO3H2, the 5'-OH by -OP(O2H)-OSO3H. Synonym: active sulfate. Acronym: PAPS (05 Mar 2000) |