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The Size of the Hydroxyl Group and Its Contribution to the Affinity of Atropine for Muscarine-sensitive Acetylcholine Receptors

Overview
Journal Br J Pharmacol
Publisher Wiley
Specialty Pharmacology
Date 1980 Jan 1
PMID 7470742
Citations 5
Authors
R B Barlow
S Ramtoola
Affiliations
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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.

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References
1.
Barlow R, Franks F, Pearson J . Studies on the stereospecificity of closely related compounds which block postganglionic acetylcholine receptors in the guinea-pig ileum. J Med Chem. 1973; 16(5):439-46. DOI: 10.1021/jm00263a003. View
2.
Armstrong J, Barlow R . The ionization of phenolic amines, including apomorphine, dopamine and catecholamines and an assessment of zwitterion constants. Br J Pharmacol. 1976; 57(4):501-16. PMC: 1667040. DOI: 10.1111/j.1476-5381.1976.tb10377.x. View
3.
Barlow R, Burston K . Temperature coefficients of affinity and entropies of adsorption from enantiomeric pairs of compounds acting at muscarinic receptors in the guinea-pig ileum. Br J Pharmacol. 1979; 66(4):581-5. PMC: 2043587. DOI: 10.1111/j.1476-5381.1979.tb13697.x. View
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Barlow R, Birdsall N, Hulme E . Temperature coefficients of affinity constants for the binding of antagonists to muscarinic receptors in the rat cerebral cortex. Br J Pharmacol. 1979; 66(4):587-90. PMC: 2043583. DOI: 10.1111/j.1476-5381.1979.tb13698.x. View
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Barlow R, Burston K . The ionization of 5-hydroxytryptamine and related compounds and an appraisal of methods for the estimation of zwitterion constants. Br J Pharmacol. 1980; 69(4):587-95. PMC: 2044315. DOI: 10.1111/j.1476-5381.1980.tb07908.x. View