The effect on DNA conformation upon binding of the bis-intercalator, N,N'-diacridinyl spermidine is studied by uranyl mediated DNA photocleavage and gel retardation. It is shown that a characteristic A-tract correlated 10 base pair modulation of the uranyl photocleavage of bent (kinetoplast) DNA is suppressed upon binding of the diacridine. Likewise, the anomalous slow gel electrophoretic migration of bent-DNA is abolished by diacridine binding. At higher diacridine/DNA ratios a DNA conformation in which G-residues become hypersensitive to uranyl photocleavage is induced.