Effects of Solubilizers On Crystallization of Human Gamma D-Crystallin

Crystallization of proteins is thought to begin with stochastic aggregation of protein monomers. The effects of alpha A-crystallin and NDSB-201 on solutions of human gamma D-crystallin (HGD) were examined. Alpha A-crystallin is naturally occurring in the lens of the eye, while NDSB-201 is a synthetic commercially available solubilizer. Conditions in the solutions were tuned to induce aggregation and crystallization of HGD by addition of CaCl2 to solutions of the protein. Aggregation of HGD was tracked by dynamic light scattering.

While alpha A-crystallin and NDSB-201 reduced both both the rate and occurrence of crystallization, the solubilizing properties of alpha A-crystallin were far superior to those of NDSB-201. Alpha A-crystallin decreased the size of aggregates in solution and, in the case examined, prevented crystallization from occurring. On the other hand, NDSB-201 did not decrease the size of the aggregates but it reduced the sizes of crystals obtained and increased the energy barrier to nucleation when compared to HGD-CaCl2 solutions with no NDSB-201.