1. Department of Microbiology and Molecular Genetics, University of Vermont, 95 Carrigan Drive, Burlington, Vermont 05405, United States
2. Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
3. Department of Molecular Physiology and Biophysics, University of Vermont, 149 Beaumont Avenue, Burlington, Vermont 05405, United States