1. Biophysics Graduate Group, University of California – Berkeley, Berkeley, CA 94720-3220, USA
2. Department of Integrative Biology, University of California – Berkeley, Berkeley, CA 94720-3140, USA
3. Department of Biology, University of Washington, Seattle, WA 98195-1800, USA
4. Center for Computational Biology, Montana State University, Bozeman, MT 59717-3148, USA