Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, Maryland, United States of America, Department of Bioinformatics, Boston University, Boston, Massachusetts, United States of America.|Applied and Computational Mathematics Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States of America.|Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, Maryland, United States of America.|Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, Maryland, United States of America.