1. Radioimmune and Inorganic Chemistry Section, Radiation Oncology Branch, Center for Cancer Research, Department of Diagnostic Radiology, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, Wyatt Technology Corporation, 30 South La Patera Lane, B-7, Santa Barbara, California 93117, and Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717