| half cystine | Refers to one-half of a cystine molecule or of a cystinyl residue in a protein or peptide. (05 Mar 2000) |
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| half and half nail | Division of the nail by a transverse line into a proximal dull white part and a distal pink or brown part; seen in uraemia. (05 Mar 2000) |
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| meso-cystine | An isomer of cystine in which the configuration about one of the alpha-carbons is d, about the other, l, so that the molecule as a whole possesses a plane of symmetry and is optically inactive. Note that meso-cystine is not dl-cystine. Dl-cystine is a racaemic mixture of dd-cystine and ll-cystine. (05 Mar 2000) |
| cystine | <amino acid> The amino acid formed by linking two cysteine residues with a disulphide linkage between the two SH groups. The analagous compound present within proteins is termed two half cysteines. (18 Nov 1997) |
| cystine bridge | A disulfide linkage between two cysteinyl residues in a poly-or oligopeptide or in a protein, any disulfide linkage between any thiol-containing moieties of a larger molecule. Synonym: cystine bridge. (05 Mar 2000) |
| cystine calculus | A calculus composed of cystine, soft and faintly radiopaque. (05 Mar 2000) |
| cystine desulfhydrase | <enzyme> A multifunctional pyridoxal phosphate enzyme. In the final step in the biosynthesis of cysteine it catalyses the cleavage of cystathionine to yield cysteine, ammonia, and 2-ketobutyrate. Chemical name: L-Cystathionine cysteine-lyase (deaminating) Registry number: EC 4.4.1.1 (12 Dec 1998) |
| cystine disease | Lysosomal storage disorders of unknown molecular defect, characterised by widespread deposition of cystine crystals in reticuloendothelial cells. (12 Dec 1998) |
| cystine lyase | <enzyme> An enzyme catalyzing the hydrolysis of l-cystathionine to pyruvate, l-homocysteine, and NH3. See: cystathionine gamma-lyase. Synonym: beta-cystathionase, cystine lyase. (05 Mar 2000) |
| cystine storage disease | Lysosomal storage disorders of unknown molecular defect, characterised by widespread deposition of cystine crystals in reticuloendothelial cells. (12 Dec 1998) |
| L-cysteine-cystine C-S lyase | <enzyme> C-des - cysteine desulfhydrase; a pyridoxal phosphate- containing enzyme from synechocystis involved information of fe-s cluster of ferredoxin; catalyses the breakdown of l-cysteine to yield sulfide, pyruvate and ammonia; increased activity with cystine, yielding cysteine persulfide as the primary product; mw about 43 kD Registry number: EC 4.4.1.- Synonym: c-des lyase (26 Jun 1999) |
| biological half-life | <biochemistry, biology> This is the time required for one-half of the total amount of a particular substance in a biological system to be consumed or broken down by biological processes when the rate of removal is approximately exponential. Toxic chemicals with a long biological half-life (such as some pesticides) will tend to accumulate in the body and are, therefore, more likely to be harmful. A substance with a short biological half-life may still accumulate if a portion of it it becomes tightly bound to bone or other tissues, even if most of it is quickly cleared from the body. (21 Mar 1998) |
| red half-moon | <clinical sign> Irregular red discoloration of the usually pale demilune at the base of the fingernail; may be seen in congestive failure, malignant disease, or liver disease, but not specific for any of these. (05 Mar 2000) |
| physical half-life | The time required for half the atoms of a radionuclide to undergo disintegration. (05 Mar 2000) |
| half | In an equal part or degree; in some pa appromating a half; partially; imperfectly; as, half-coloured, half done, half-hearted, half persuaded, half conscious. "Half loth and half consenting." "Their children spoke halfin the speech of Ashdod." (Neh. Xiii. 24) 1. Consisting of a moiety, or half; as, a half bushel; a half hour; a half dollar; a half view. The adjective and noun are often united to form a compound. 2. Consisting of some indefinite portion resembling a half; approximately a half, whether more or less; partial; imperfect; as, a half dream; half knowledge. "Assumed from thence a half consent." (Tennyson) Half ape, a middle or intermediate tint, as in drawing or painting. See Demitint. Half truth, a statement only partially true, or which gives only a part of the truth. Half year, the space of six moths; one term of a school when there are two terms in a year. Origin: AS. Healf, half, half; as a noun, half, side, part; akin to OS, OFries, & D. Half, G. Halb, Sw. Half, Dan. Halv, Icel. Halfr, Goth. Halbs. Cf. Halve, Behalf. Source: Websters Dictionary (01 Mar 1998) |
| half-a-gram stain | <technique> A lab technique used to detect the presence of members from the bacterial family Legionellaceae in samples of sputum. (09 Oct 1997) |