1. Center for Theoretical Biological Physics and Department of Physics, University of California, San Diego, California 92093, USA
2. Department of Physics, University of California, Santa Barbara, California 93106, USA
3. Department of Physics and Astronomy, Earlham College, Richmond, Indiana 47374, USA
4. Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
5. Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA