The wave vector dependence of diffusion coefficients in photon correlation spectroscopy of protein solutions

摘要

The mutual diffusion coefficientDmwas measured by means of photon correlation spectroscopy (PCS) for bovine serum albumin (BSA) atpH 4.7 and ionic strengthIsime;0.12 M. The BSA concentrations ranged from 1.00 to 10.7 g/dland the magnitude of the scattering wave vector K varied from 3.21times;104to 3.51times;105cmminus;1. It was found thatDm=D0lsqb;1minus;(0.0166plusmn;0.0009)Crsqb;, whereD0=(5.92plusmn;0.04)times;10minus;7cm2/s corrected to water at 20thinsp;deg;C and theCmeasured in units of g/dl. The quantityCn/K3, whereCnis the concentration in number of solute particles per cm3, ranged from 2 to 27 000, but this had no influence on the measured values ofDm. This work does not support the idea that the small size ofKminus;1or the small number of molecules contained in the volumeKminus;3affects the magnitudes of diffusion coefficients determined by PCS for proteins at moderate ionic strengths.