1. Leukaemia Research Fund Laboratory and Department of Chemistry, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, U.K., CRC Drug-DNA Interactions Research Group, Department of Oncology, University College London Medical School, London W1P 8BT, U.K., and Department of Molecular Carcinogenesis, Institute of Cancer Research, Sutton, Surrey SM2 5NG, U.K.