Raman spectroscopy of an O2–Co(II)bleomycin–calf thymus DNA adduct: alternate polymer conformations Original Research Article

Bleomycin (Blm) is an antitumor agent which binds to specific sequences of DNA and as HO2–Fe(III)Blm causes single and double strand cleavage. In the present investigation, binding of O2–Co(II)Blm to a native DNA polymer, calf thymus DNA, was examined using conventional Raman spectroscopy. O2–Co(II)Blm is a model for O2–Fe(II)Blm, the direct precursor of HO2–Fe(III)Blm. Although the DNA polymer retained a predominant B-form structure, Raman spectral evidence was obtained for localized structural changes to A, C and Z-DNA forms. The presence of these alternate DNA forms within B-DNA implied the presence of B/A, B/C and B/Z junctions. The observed changes in DNA secondary structure were attributed to perturbation of structural water resulting from binding of O2–Co(II)Blm within the minor groove.