Center for Theoretical Biological Physics (CTBP) and Department of Physics, University of California at San Diego (UCSD), La Jolla, California, United States of America, Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America.|Laboratory of Theory of Biopolymers, University of Warsaw, Warsaw, Poland.|Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America.|Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America.|Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America.|Departments of Chemistry and Biochemistry, University of California at San Diego (UCSD), La Jolla, California, United States of America.