1. Department of Pharmaceutical Sciences, College of Pharmacy, 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 2K6, and Department of Polymer Sciences, School of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow V-234, 119899 Russia