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.
Likhitsup
Asawin
A
Department of Chemistry, University of Warwick, Coventry, United Kingdom CV4 7AL.
Deeth
Robert J
RJ
Otto
Sijbren
S
Marsh
Andrew
A
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