title: The size of the hydroxyl group and its contribution to the affinity of atropine for muscarine-sensitive acetylcholine receptors.
abstract: 1 From measurements of the affinity constants of hydratropyltropine and its methiodide for muscarine-sensitive acetylcholine receptors in the guinea-pig ileum, the increment in log K for the hydroxyl group in atropine is 2.06 and in the methiodide it is 2.16. These effects are slightly bigger than any so far recorded with these receptors. 2 The estimate of the increment in apparent molal volume for the hydroxyl group is 1.1 cm3/mol in atropine and 1.0 cm3/mol in the methobromide. 3 The large effect of the group on affinity may be linked to its small apparent size in water as suggested in the previous paper.
mesh_terms: D000818:Animals; D001285:Atropine / Q000378:metabolism*; D006168:Guinea Pigs; D006900:Hydroxylation; D066298:In Vitro Techniques; D007700:Kinetics; D009116:Muscarine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011950:Receptors, Cholinergic; D001285:Atropine; D009116:Muscarine