Interactions of water-soluble metalloporphyrins with nucleic acids studied by resonance Raman spectroscopy

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Abstract
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)-nuleic acid interactions. Bands II(Cβ-H bending, ˜1100 cm−1 ) and VIII (Cβ-Cβ stretch, ˜1570 cm 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-ound at the A-T sies of nucleic acids. Both Bands V (˜1260 cm) and IX(˜l646 cm ) 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 P02 group of the nucleic acid.