Assesment of protein reorientational diffusion in solution by 13C off‐resonance rotating frame spin–lattice relaxation: Effect of polydispersity

Abstract

The ¹³C off‐resonance rotating frame spin‐lattice relaxation technique is applicable to the study of protein rotational diffusion behavior in both model in vitro and in vivo systems. The original formalism of James and co‐workers [(1978) J. Am. Chem. Soc.100, 3590–3594] was constrained by the assumption of random isotropic reorientational motion of a monodisperse protein population. Here we extend the formalism to include polydispersity. Application is made to the alkaline pH induced association of lysozyme, lysozyme–bovine serum albumin mixtures, and to the phase separation of lysozyme salt–water mixtures induced by low temperature.