1 Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138 USA.
2 Department of Biochemistry and Molecular Biology, Department of Chemistry, University of Chicago, Gordon Center for Integrative Science, 929 E 57th St, Chicago, IL 60637.
3 Cardiovascular Research Institute, Departments of Biochemistry and Biophysics, and Cellular and Molecular Pharmacology, California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA 93858-2330 USA; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA. Electronic address: [email protected].