Stabilization of the left-handed Z-DNA with monoamines and polyamines.

It is known that the crystal structure of d(CG)3 become left-handed Z-DNA under high salt concentration and various polyamines stabilize the Z-DNA structure. We have structurally investigated how polyamines stabilize the Z-DNA by the X-ray crystallographic analysis of d(CG)3-polyamine cocrystals. In this study, we determined the Z-DNA structures with di- to pentavalent polyamines at high resolution. Comparison with the structures revealed that the valence of polyamine determined number of the polyamine(s) and metal ion(s) chelating to the Z-DNA. Furthermore, we succeeded in crystallizing d(CG)3-monoamine (methylamine and ethylamine) complexes.