1. Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, United States
2. Molecular Histopathology Laboratory, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, United States
3. Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, United States
4. Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, United States