| amino acid substitution | The naturally occurring or experimentally induced replacement of one or more amino acids in a protein with another. If a functionally equivalent amino acid is substituted, the protein may retain wild-type activity. Substitution may also diminish or eliminate protein function. Experimentally induced substitution is often used to study enzyme activities and binding site properties. (12 Dec 1998) |
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| base substitution | <molecular biology> One nucleotide base is replaced by another in a DNA molecule. This is also called a point mutation. (09 Oct 1997) |
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| conservative substitution | In a gene product, a substitution of one amino acid with another with generally similar properties (size, hydrophobicity, etc), such that the overall functioning is likely not to be seriously affected. (18 Nov 1997) |
| stimulus substitution | <psychology> Learning that takes place when a conditioned stimulus is paired with an unconditioned stimulus. (12 Dec 1998) |
| substitution | 1. The act of putting one thing in the place of another, especially the chemical replacement of one element or radical by some other. 2. A defense mechanism, operating unconsciously, in which an unattainable or unacceptable goal, emotion or object is replaced by one that is attainable or acceptable. Origin: L. Substitutio, from statuere = to place (18 Nov 1997) |
| substitution mutation | A mutation caused by a nucleotide base being replaced by a different one. (09 Oct 1997) |
| substitution product | A product obtained by replacing one atom or group in a molecule with another atom or group. (05 Mar 2000) |
| substitution therapy | Replacement therapy, particularly when replacement is not physiological but entails administration of a substitute. (05 Mar 2000) |
| substitution transfusion | Removal of most of a patient's blood followed by introduction of an equal amount from donors. Synonym: exsanguination transfusion, substitution transfusion, total transfusion. (05 Mar 2000) |
| symptom substitution | An unconscious psychological process by which a repressed impulse is indirectly manifested through a particular symptom, e.g., anxiety, compulsion, depression, hallucination, obsession. Synonym: symptom formation. (05 Mar 2000) |
| freeze substitution | A modification of the freeze-drying method in which the ice within the frozen tissue is replaced by alcohol or other solvent at a very low temperature. (12 Dec 1998) |
| acidic amino acid | An Amino acid with a second acid moiety, e.g., glutamic acid, aspartic acid, cysteic acid. (05 Mar 2000) |
| activated amino acid | The product formed by the condensation of the acyl radical of an amino acid and adenosine 5'-monophosphate (originally in the form of adenosine 5'-triphosphate, with elimination of a pyrophosphoric group). Formed in the first step of protein biosynthesis. Synonym: activated amino acid. (05 Mar 2000) |
| alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid | <chemical> Alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropanoic acid. An ibotenic acid homolog and glutamate agonist. The compound is the defining agonist for the ampa subtype of glutamate receptors (receptors, ampa). It has been used as a radionuclide imaging agent but is more commonly used as an experimental tool in cell biological studies. Pharmacological action: excitatory amino acid agonists. Chemical name: 4-Isoxazolepropanoic acid, alpha-amino-2,3-dihydro-5-methyl-3-oxo- (12 Dec 1998) |
| alpha-amino acid | Typically, an amino acid of the general formula R-CHNH2-COOH (i.e., the NH2 in the a position); the l forms of these are the hydrolysis products of proteins. In rarer usages, this class of molecules also includes alpha-amino phosphoric acids and alpha-aminosulfonic acids. (05 Mar 2000) |
| alpha-amino acid esterase | <enzyme> Converts alpha-amino acid esters and water to alpha-amino acids and alcohol Registry number: EC 3.1.1.43 Synonym: alpha-amino acid ester hydrolase (26 Jun 1999) |