1. Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6083, Department of Chemistry, Trent University, 1600 West Bank Drive, Peterborough, Ontario, Canada, K9J 7B8, and U.S. Geological Survey-WRD, 8505 Research Way, Middleton, Wisconsin 53562