1. A.B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments
of Biochemistry, §Chemistry, and #Pharmacology, ‡Mass Spectrometry Research Center, ⊥Vanderbilt Institute of Chemical Biology,
Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States