1. Department of Chemistry University of Michigan 930 N. University Ave. Ann Arbor MI 48109-1055 USA
2. Institut für Physik-NMR Halle/Saale Germany
3. Macromolecular Science and Engineering University of Michigan 2300 Hayward Avenue Ann Arbor MI 48109-1055 USA
4. Biophysics Program University of Michigan 930 N. University Ave. Ann Arbor MI 48109-1055 USA