1. Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
2. Northeastern Collaborative Access Team and Department of Chemistry and Chemical Biology, Cornell University, Building 436E, Argonne National Laboratory, Argonne, Illinois 60439, United States
3. Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland 21702, United States
4. Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States