1. The Clinical Endocrinology Branch and Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 50 South Drive, Bethesda, Maryland 20892, NIH Chemical Genomics Center, National Human Genome Research Institute, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland 20850, and Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, D.C. 20375