Progress in the development of an alternative approach to macromolecular crystallization

We are developing an alternate strategy for the crystallization of macromolecules that does not, like current methods, depend on the optimization of traditional variables such as pH and precipitant concentration, but is based on the hypothesis that many conventional small molecules might establish stabilizing, intermolecular,. noncovalent cross-links in crystals', and thereby promote lattice formation. Earlier experiments provided encouraging results that suggested further research was warranted (Larson, S. B.; Day, J. S.; Cudney, R.; McPherson, A. A novel strategy for the crystallization of proteins: X-ray diffraction validation. Acta Crystallogr., D: Biol. Crystallogr. 2007, 63, 310-318. McPherson, A.; Cudney, B. Searching for silver bullets: an alternative strategy for crystallizing macromolecules. J. Struct. Biol. 2006, 156, 387-406). Here we report additional, large-scale crystallization screening experiments that lend further support, though they suggest that additional mechanisms may play a positive role as well. As before, we accompanied the crystallization experiments with X-ray diffraction analyses of some of the crystals grown. A number of these showed incorporation of conventional molecules into protein crystal lattices, and further validated the underlying hypothesis. The strategy we are pursuing is essentially orthogonal to current approaches and has an objective of doubling the success rate of today.