| peptide chain elongation | The process whereby an amino acid is joined through a substituted amide linkage to a chain of peptides. (12 Dec 1998) |
|---|---|
| peptide chain initiation | The process whereby the formation of a peptide chain is started. This process requires (1) the 30s subunit, (2) the mRNA coding for the polypeptide to be made, (3) met-trnai, (4) initiation factors, and (5) GTP. (12 Dec 1998) |
| peptide chain termination | The process whereby the last amino acid is added to a polypeptide. This termination is signaled by one of three termination triplets in the mRNA, immediately following the last amino acid codon. (12 Dec 1998) |
| chain | 1. In chemistry, a series of atoms held together by one or more covalent bonds. 2. In bacteriology, a linear arrangement of living cells that have divided in one plane and remain attached to each other. Origin: L. Catena (05 Mar 2000) |
| chain-compensated spirometer | A Tissot spirometer in which compensation for change in bell buoyancy is accomplished automatically by a suspending chain of correct mass per unit length. (05 Mar 2000) |
| chain isomer | <chemistry> One of two or more compounds having the same chemical composition but differing in the arrangement of the atoms (usually carbon atoms) forming the backbone of the structure of the compounds. (21 Mar 1998) |
| chain reaction | A reaction in which a product reacts and thus continues the reaction. (09 Oct 1997) |
| chain reflex | A series of reflexs, each serving as a stimulus for the next. (05 Mar 2000) |
| phenylalanyl chain | A polypeptide component of insulin containing 30 amino acyl residues, beginning with a phenylalanyl residue (NH2-terminus); insulin is formed by the linkage of a B chain to an A chain by two disulfide bonds; the amino-acid composition of the B chain is a function of species. Synonym: phenylalanyl chain. (05 Mar 2000) |
| closed chain compound | Any compound in which the constituent atoms, or any part of them, form a ring. Used mainly in organic chemistry where: 1) numerous compound's contain rings of carbon atoms (carbocyclic compound's) or carbon atoms plus one or more atoms of other types (heterocyclic compound's), usually nitrogen, oxygen, or sulfur; 2) where the atoms in the ring are all of the same element (homocyclic or isocyclic compound); 3) where the ring is saturated or contains nonconjugated double bonds (alicyclic compound), the compound is similar in properties to the corresponding acyclic compound (e.g., cyclohexane resembles hexane); 4) where the ring contains conjugated double bonds in a closed loop in which there are 4n + 2 (where n is an integer) delocalised π electrons (Huckel's rule) (aromatic compound; e.g., benzene, pyridine), it is more stable than the corresponding saturated ring and exhibits unusual chemical properties characteristic of itself and not of other types of rings or of acyclic compound's. These aromatic compounds have the ability to sustain an induced ring current. Synonym: closed chain compound, ring compound. (05 Mar 2000) |
| cold chain | A system of protection against high environmental temperatures for heat-labile vaccines, sera and other biological preparations. (05 Mar 2000) |
| corticosteroid side-chain-isomerase | <enzyme> Converts 11-deoxycorticosterone to 20-hydroxy-3-oxypregn-4-en-21-al; also acts as an epimerase at c-20 Registry number: EC 5.3.1.21 Synonym: corticosteroid side chain isomerase, ccsci (26 Jun 1999) |
| polymerase chain reaction | <molecular biology, technique> The first practical system for in vitro amplification of DNA and as such one of the most important recent developments in molecular biology. Two synthetic oligonucleotide primers, which are complementary to two regions of the target DNA (one for each strand) to be amplified, are added to the target DNA (that need not be pure), in the presence of excess deoxynucleotides and Taq polymerase, a heat stable DNA polymerase. In a series (typically 30) of temperature cycles, the target DNA is repeatedly denatured (around 90_C), annealed to the primers (typically at 50-60_C) and a daughter strand extended from the primers (72_C). As the daughter strands themselves act as templates for subsequent cycles, DNA fragments matching both primers are amplified exponentially, rather than linearly. The original DNA need thus be neither pure nor abundant and the polymerase chain reaction has accordingly become widely used not only in research, but in clinical diagnostics and forensic science. Acronym: PCR (14 Oct 1997) |
| haemolytic chain | The haemolysis that occurs when complement is activated by the previously formed union of erythrocytes and specific antibody. (05 Mar 2000) |
| H chain | <protein> Heavy chain of immunoglobulin, see IgG, IgM, etc. (18 Nov 1997) |