title: Biophysical studies on molecular mechanisms of abortifacient action of prostaglandins. V. CNDO/2 estimation of the relative affinities of the cations Na+, Mg2+ and Ca2+ to the carboxylic group.
abstract: The paper describes the study of relative affinities of the cations Na+, Mg2+ and Ca2+ to the carboxylic group, their electronic structure and optimum binding positions on the basis of the CNDO/2 technique, using the well known supramolecular approach. The cation for this purpose was made to approach the carboxylic group in various possible directions in and out of the plane C1O1AO1B and the final parameters were evaluated for the optimum planar as well as nonplanar geometries. With the exception of Ca2+ the nonplanar geometries were always favoured over the planar ones for binding at O1A and O1B, whereas for symmetric binding between O1A and O1B planar geometries were favoured for Mg2+ and Ca2+. The distance between the cation and oxygen was slightly larger for this geometry and Etot which followed the order Mg2+ less than Ca2+ less than Na+ had the lowest value.
mesh_terms: D000019:Abortifacient Agents / Q000378:metabolism*; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D002118:Calcium / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008956:Models, Chemical; D011453:Prostaglandins / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
chemical_list: D000019:Abortifacient Agents; D011453:Prostaglandins; D012964:Sodium; D008274:Magnesium; D002118:Calcium