Second virial coefficient:: variations with lysozyme crystallization conditions

Interparticle lysozyme interactions in solution have been studied by small angle X-ray scattering (SAXS) as a function of salt type (NaCl, NaNO3, NaSCN and NaOAc), salt concentration, and as a function of temperature between 30 degrees C and 10 degrees C. The choice of conditions was made to cover variations from (undersaturated) solutions to (supersaturated) crystallization conditions. The second virial coefficients (A(2)) were determined from the X-ray structure factors extrapolated to the origin, as a function of protein concentration. The A(2) values which correspond to lysozyme crystallization conditions were found to be in a range from about zero to -8.0 x 10(-4) mol ml g(-2), in agreement with previous determinations by other groups. The variations of the second virial coefficient from positive (repulsive interactions) to negative (attractive interactions) were found to follow the efficiency of salts to induce crystallization. The choice of the second virial coefficient as a tool to predict crystallization conditions is discussed. (C) 1999 Elsevier Science B.V. All rights reserved.