[1] Johns Hopkins Med Inst, Div Cardiol, Dept Med, Baltimore, MD 21287 USA
[2] Univ Calif Los Angeles, Sch Publ Hlth, Interdepartmental Program Mol Toxicol, Los Angeles, CA 90095 USA
[3] Univ Calif Los Angeles, Sch Med, Dept Pharmacol, Hlth Sci Ctr, Los Angeles, CA 90095 USA
[4] Univ Arizona, Dept Chem, Tucson, AZ 85721 USA
[5] NCI, Radiat Biol Branch, Bethesda, MD 20892 USA
[6] UCL, Wolfson Inst Biomed Res, London WC1E 6AE, England