side chain
[side n.1]
† 1. A chain mounted at the side of a vehicle for any purpose (see quots.). Obs.
| 1849–50 J. Weale Dict. Terms, Side Chains, chains and hooks fixed to the sides of the tender and engine for safety, should the central drag-bar give way. 1883 W. S. Gresley Gloss. Coal-Mining 221 Side chain, a chain hooked on to the sides of tubs when running upon an engine-plane or jig, to keep all the tubs together in case a coupling breaks. 1886 Encycl. Brit. XX. 247/2 Some [railway] companies have gone further and placed the guard or side chains upon springs. |
2. a. Chem. A chain of atoms attached to the principal part of a molecule.
| 1886 Roscoe & Schorlemmer Treat. Chem. III. iii. 7 If two atoms of hydrogen [in benzene] be replaced by elements or radicals, termed ‘side chains’, three isomeric compounds may be formed whether the entering element or side chain be identical or different. 1927 Haldane & Huxley Animal Biol. ii. 73 The whole [chromosome] is like a gigantic single organic chemical compound, since the molecules of such a chemical compound are all made up of smaller parts—the side-chain and radicals and single atoms. 1974 Sci. Amer. June 59/3 They [sc. the catecholamines] have in common a chemical structure that consists of a benzene ring on which there are two adjacent hydroxyl groups and an ethylamine side chain. |
b. Physiol. A structure postulated to project from the surface of a cell and to constitute a receptor (receptor 3 a) in Ehrlich's theory of immunological action; so side-chain theory.
| 1900 tr. P. Ehrlich in Proc. R. Soc. LXVI. 433 We may assume that the protoplasm consists of a special executive centre..in connection with which are nutritive side-chains, which possess a certain degree of independence, and which may differ from one another according to the requirements of the different cells. Ibid. 440, I have now laid before you the fundamental facts which up to the present constitute our knowledge in the field pertaining to immunity, and which can be most easily and successfully explained through the agency of ‘side-chain theory’. 1911 Rep. Brit. Assoc. Adv. Sci. 1910 635 Ehrlich has given a graphic representation of this process in his side-chain theory. 1935 N. P. Sherwood Immunol. vi. 121 In Ehrlich's theory these free chemical entities or cast-off side chains constitute the antibodies found in the circulation. 1974 Encycl. Brit. Macropædia VI. 510/1 Only if the haptophore group of a toxic molecule combines with the side chain of the cell can a bacterial toxin act upon a cell. The affected organism then produces great quantities of the side chains, all of them ‘gauged’ to the disease-producing agent. These immune bodies prevent a renewed infection. |