Orientations of Water Molecules Surrounding B-DNA Observed by Neutron Crystallographic Analysis

By neutron diffraction measurements of B-DNA duplex, we have succeeded in determining the D positions in 27 D2O molecules. Moreover, the complex water network in the minor groove has been observed in detail. By a combined structural analysis using X-ray and neutron data, it is clear that the spine of hydration is built up, not only by a simple hexagonal hydration pattern, but also by many other water bridges hydrogen-bonded to the DNA strands. The complexity of the hydration pattern in the minor groove is derived from an extraordinary variety of orientations displayed by the water molecules.