Unified theory for a receptor system with a distributed binding affinity to substrates

Abstract

We present a theory for a unified characterization of a substrate-receptor system with an arbitrary binding affinity distribution. On the basis of a universal expression obtained for the bound fraction isotherm of a monovalent receptor system, we propose a novel experimental analysis method for characterization of the receptor system, introducing a new type of experimental plot. From our analysis method, one can extract key physical parameters that mostly determine the shape of bound fraction isotherm, which include the mean binding affinity, the mean binding free energy, and the parameters that measure the magnitude of fluctuation and the asymmetry of the binding free energy distribution for receptor-substrate system, without any bias that can be introduced by presuming a particular functional form for the binding free energy distribution or for the bound fraction isotherm. (C) 2011 Elsevier B.V. All rights reserved.