Prediction of a crystallization pathway for Z-DNA hexanucleotides.

Crystallization of macromolecules for structural studies has long been a hit-or-miss process. The crystallization of hexanucleotides as Z-DNA was studied, and it was shown that the cation concentration for crystal formation could be predicted from solvation free energy (SFE) calculations. Solution studies on the conformation and solubilities of the hexanucleotides showed that a critical concentration of the DNA in the Z-conformation must be present in solution to effect crystallization. The SFE calculations therefore predict the propensity of the hexanucleotides to adopt the left-handed conformation and the driving force required to reach this critical concentration relative to the intrinsic solubility of Z-DNA for crystallization.