1. Protein Nucleic Acid Interaction Section, Biophysics Resource, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, SAIC-Frederick, Inc., National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, Department of Structural Biology, University of Pittsburgh School of Medicine, 1050 BST3, Pittsburgh, Pennsylvania 15261, X-ray Science Division, Advanced Photon Source, Argonne National...