1. State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian, P. R. China, Department of Chemistry and Biochemistry and Nanocenter, University of South Carolina, Columbia, South Carolina 29208, Atlanta Research & Educational Foundation, Atlanta VA Medical Center 1670, Clairmont Road, Decatur, Georgia 30033, and Botulinum Research Center, University of Massachusetts, Dartmouth, 285 Old Westport Road, Dartmouth, Massachusetts 02747