INSERM U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, 59045 Lille, France, Biospectroscopy and Physical Chemistry Unit, Department of Chemistry and Natural and Synthetic Drugs Research Center, University of Liege, Sart-Tilman, 4000 Liege, Belgium, and Department of Chemistry and Laboratory for Chemical and Biological Sciences, Georgia State University, Atlanta, Georgia 30303 (At 2005-01-15)