DYNAMIC LIGHT-SCATTERING STUDY OF PRECRYSTALLIZING RIBONUCLEASE SOLUTIONS

The translational diffusion coefficient of bovine pancreatic ribonucle ase A, a globular protein, has been measured by dynamic light scatteri ng under various conditions related to the crystallization process. In all cases, a monomodal light scattering autocorrelation function was observed. The diffusion coefficient exhibited a linear dependence on p rotein concentration and an interaction parameter could be calculated. Attractive interactions were found to increase with salt concentratio n and to decrease with pH in the presence of salts. Finally, optimal c rystallization conditions correspond to moderate attractive interactio ns.