1. Contribution from the Department of Applied Science, University of California, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, and JASRI, SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679...