1. Department
of Radiology and Biomedical Imaging, University of California, San Francisco, California 94158, United States
2. Department
of Radiology and Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, United States
3. Departments
of Chemistry and Molecular and Cell Biology and the Howard Hughes
Medical Institute, University of California, Berkeley, California 94720, United States