1. Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA
2. Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, 800 Rose St. MS-415 Medical Center, Lexington, KY 40536-0298, USA
3. Department of Biology, 101 T. H. Morgan Building, Lexington, KY 40506-0225, USA