LYSOZYME CRYSTAL-GROWTH, AS OBSERVED BY SMALL-ANGLE X-RAY-SCATTERING,PROCEEDS WITHOUT CRYSTALLIZATION INTERMEDIATES

A combination of small angle X-ray scattering and gel techniques was u sed to follow the kinetics of protein crystal growth as a function of time. Hen egg white lysozyme, at different protein concentrations, was used as a model system. A new sample holder was designed, in which su persaturation is induced in the presence of salt by decreasing the tem perature. It had been shown previously that a decrease in temperature and/or an increase in crystallizing agent induces an increase in the a ttractive interactions present in the lysozyme solutions, the lysozyme remaining monomeric. In the present paper we show that similar behavi our is observed in NaCl when agarose gels are used. During crystal gro wth, special attention was paid to determine whether oligomers were fo rmed as the protein in solution was incorporated in the newly formed c rystals. From these first series of experiments, we did not find any i ndication of oligomer formation between monomer in solution and crysta l. The results obtained are in agreement with the hypothesis that lyso zyme crystals in NaCl grow by addition of monomeric particles.