Center for Theoretical Biological Physics and Department of Physics, University of California at San Diego, La Jolla, California, USA. hermsen@ctbp.ucsd.edu|Center for Theoretical Biological Physics and Department of Physics, University of California at San Diego, La Jolla, California, USA. hermsen@ctbp.ucsd.edu|Center for Theoretical Biological Physics and Department of Physics, University of California at San Diego, La Jolla, California, USA. hermsen@ctbp.ucsd.edu