1. Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106-9510, United States
2. Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
3. Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
4. Max-Planck-Institut Für Biophysikalische Chemie, Karl Friedrich-Bonhoeffer-Institut, Am Fassberg 11, 37077 Göttingen, Germany