1. Contribution from Physical Chemistry I−Biophysical Chemistry and Organic Chemistry, Department of Chemistry, University of Dortmund, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany, Departments of Chemical and Structural Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany, and Laboratory for Fluorescence Dynamics, University of Illinois, Urbana, Illinois 61801