1. Department of Biology, Center for Biotechnology and Interdisciplinary Studies, Room 2137, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 6180, Chemistry Department, Gorlaus Laboratories, Leiden University, Leiden, The Netherlands, and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801