The proton exchange cross-relaxation model of water relaxation in biopolymer systems

Abstract

A general theory of water proton relaxation in aqueous biopolymer systems is presented which includes the effects of fast exchange between water and biopolymer protons as well as secular dipolar cross-relaxation. Transverse, longitudinal and rotating frame relaxation are treated under conditions of selective or non-selective excitation. It is argued that in dilute globular protein solutions the contribution of hydration (or ‘bound’) water to the relaxation is minor compared with the dominant effects of fast proton exchange. The problems arising in gels and water-poor systems are discussed.