1. Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
2. Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
3. Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
4. Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.