1. Duke Comprehensive Cancer Center and Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, Department of Chemistry, Korea Advanced Institute of Science and Technology, Taejeon 305-701, Korea, Department of Food and Nutrition, Hanyang University, Seoul 133-791, Korea, Schools of Natural Science and Engineering, University of California, Merced, California 95344, and Department of Medicine, University of Chicago, Chicago, Illinois, 60637