1. Department of Physics and Institute of Molecular Biophysics and School of Computational Science, Florida State University, Tallahassee, Florida 32306;
2. Departmento de Ciencia de Proteinas, Centro de Investigaciones Biológicas, CSIC, Madrid 28040, Spain;
3. Section on Physical Biochemistry, Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland 20892;