1. Departments of Chemistry and Physics, University of Rochester, Rochester, New York 14627, Center for Pediatric Biomedical Research and Departments of Pediatrics and Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, and Institute of Bioorganic Chemistry, Polish Academy of Sciences, 60-714 Poznan, Noskowskiego 12/14, Poland