1. Division of Therapeutic Proteins, Center for Drug Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, Lancaster Laboratories, 2425 New Holland Pike, Lancaster, Pennsylvania 17605-2425, and Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, The National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892