1. Departments of Chemistry, Biochemistry and Molecular and Cell Biology, Neurobiology and Physiology, and Radiology, Northwestern University, Evanston, Illinois 60208-3113
2. Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208-3100
3. Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611