Apparent non-statistical binding in a ditopic receptor for guanosine.
Analysis of stepwise association constants for guests binding to more than one site in a receptor is expected to give a ratio of the first association constant to the second of about 4 : 1 on statistical grounds (since a second guest should have an equal chance of binding to a different site on the same, or a new molecule). Taking account of self-association in our analysis of a system in which the binding sites are close together, we observe a ratio closer to 1 : 1, indicative of non-statistical, or cooperative binding. The longer homologue built around two alkynes displays a very different ratio of stepwise association constants of about 7 : 1. We discuss the origins of this unusual behaviour in terms of steric interactions within the receptors and their corresponding complexes with guanosine derivatives.
Department of Chemistry, University of Warwick, Coventry, United Kingdom CV4 7AL.
Asawin
A
Likhitsup
Robert J
RJ
Deeth
Sijbren
S
Otto
Andrew
A
Marsh
D000480:Alkynes / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology*; D001667:Binding, Competitive; D006690:Bisbenzimidazole / Q000737:chemistry; D003562:Cytidine / Q000737:chemistry / Q000378:metabolism*; D006151:Guanosine / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D008954:Models, Biological; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000737:chemistry / Q000378:metabolism
D000480:Alkynes; D011956:Receptors, Cell Surface; D011950:Receptors, Cholinergic; D006151:Guanosine; D003562:Cytidine; D006690:Bisbenzimidazole