SELF-DIFFUSION AND SELF-ASSOCIATION OF LYSOZYME MOLECULES IN SOLUTION

Self-diffusion of lysozyme molecules at the process of their self-asso ciation were studied by pulsed-field gradient nuclear magnetic resonan ce (NMR) at different lysozyme concentrations in solution. It was show n that in the intervals of pH from 1.8 to 4.0 and from 6.5 to 9.0, lys ozyme self-diffusion coefficients were independent of pH value. In the interval of pH from 4.0 to 6.5, they decreased with increasing pH. Us ing self-diffusion data, estimations of the equilibrium constant k of the self-association reaction were made. For the model of indefinite s elf-association, k was found to be 264.5 +/- 0.5 l/M, and for its part icular case - dimerization, 143 +/- 0.5 l/M. The dependence of the con centration of monomers and different associates on the total protein c oncentration was calculated. (C) 1998 Elsevier Science B.V.