Nucleic Acids Research
The resonance Raman spectra of water-soluble porphyrins, M(TMpy-P4) (M = Cu(II), Ni(II) and Co(III)) and their mixtures with poly(dG-dC)2, poly(dA-dT)2 and calf thymus and salmon DNAs were measured using a divided rotating cell to determine the magnitudes of frequency shift and intensity variation resulting from M(TMpy-P4)-nucleic acid interactions. Bands II(Cβ-H bending, ˜ 1100 cm-1) and VIII(Cβ-Cβ stretch, ˜ 1570 cm-1) show a large and small upward shift, respectively, when Cu(TMpy-P4) and Ni(TMpy-P4) are intercalated at the G-C sites. In contrast, these bands show a small upward and downward shift, respectively, when Co(TMpy-P4) is groove-bound at the A-T sites of nucleic acids. Both Bands V (˜ 1260 cm-1) and IX (˜ 1646 cm-1) which originate in the N-methylpyridyl group always show small downward shifts due to coulombic interaction between the N-CH3+ group of TMpy-P4 and the PO2 group of the nucleic acid.