POTENTIAL OF MEAN FORCE TREATMENT OF SALT-MEDIATED PROTEIN CRYSTALLIZATION

In the initial stages of crystallization of proteins, monomers aggrega te rapidly and form nuclei and large fractal clusters, as previously s hown by dynamic light scattering experiments (Georgalis, Y., J. Schule r, J. Frank, D. M. Soumpasis, and W. Saenger. 1995. Protein crystalliz ation screening through scattering techniques. Adv. Colloid Interface Sci. 58:57-86). In this communication we initiate an effort to underst and the effective interactions controlling charged protein aggregation and crystallization using the potential of mean force (PMF) theory. W e compute the PMFs of the system lysozyme-water-NaCl within the framew ork of the hypernetted chain approximation for a wide range of protein and salt concentrations. We show that the computed effective interact ions can rationalize the experimentally observed aggregation behavior of lysozyme under crystallization conditions.