1. Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
2. Curriculum in Bioinformatics and Computational Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
3. MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, U.K.
4. Department of Pharmacology and Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, Pennsylvania 17033, United States
5. Department of Chemistry and Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
6. Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States