1. Departments of Biomedical Engineering, Material Science and Engineering, Dermatology and Medicine, State University of New York at Stony Brook, Stony Brook, New York 11794-8165, Department of Medicinal Chemistry, The University of Utah, 419 Wakara Way, Suite 205, Salt Lake City, Utah 84108-1257, and Physical Chemistry Laboratory, Estee Lauder Research, Melville, New York 11747