1. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599,Department of Chemistry, Franklin and Marshall College, P.O. Box 3003, Lancaster, Pennsylvania, 17604,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599