X-ray crystallographic analysis of the hydration of A- and B-form DNA at atomic resolution.

We have determined single crystal structures of an A-DNA decamer and a B-DNA dodecamer at 0.83 and 0.95 A, respectively. The resolution of the former is the highest reported thus far for any right-handed nucleic acid duplex and the quality of the diffraction data allowed determination of the structure with direct methods. The structures reveal unprecedented details of DNA fine structure and hydration; in particular, we have reexamined the overall hydration of A- and B-form DNA, the distribution of water around phosphate groups, and features of the water structure that may underlie the B to A transition. Copyright 2000 John Wiley & Sons, Inc.