1. Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2 Canada, School of Chemistry, University of Melbourne, Victoria 3010, Australia, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, California 94025, and Department of Applied Science, University of California, Davis, California 95616