期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1979
卷号：76
期号：8
页码：3580-3584
DOI：10.1073/pnas.76.8.3580
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Proton magnetic resonance has been used to monitor binding of choline, a known partial agonist, to acetylcholine receptor-enriched membrane preparations from Torpedo californica electroplax. The interaction between choline and receptor led to a broadening of the resonance of the choline methyl groups and this effect was reversed by alpha-bungarotoxin, a quasi-irreversible antagonist of the acetylcholine receptor. From the concentration dependence of line broadening the equilibrium dissociation constant for choline was obtained (Kd = 190 +/- 65 microM). The temperature dependence of the parameters observed in the choline titrations gave an enthalpy of binding delta H less than 1.5 kcal/mol and allowed estimates for the dissociation rate constant of the receptor-choline complex (kdiss greater than 1.6 x 10(3) S(1) and the respective activation energy, Ea (Kdiss) approximately 5.5 kcal/mol. The association of other ligands with the membrane-bound receptor could also be studied by observing effects of varying concentrations of such ligands on the choline methyl group linewidth at a constant choline concentration.
