Surface-enhanced resonance Raman spectra of adriamycin, 11-deoxycarminomycin, their model chromophores, and their complexes with DNA

The surface-enhanced resonance Raman spectra on Ag sols of adriamycin, 11-deoxycarminomycin, their model chromophores 1,4- and 1,8-dihydroxyanthraquinones, and their complexes with DNA were measured. The well-detailed spectra allowed us to obtain, by the combined analysis in terms of symmetry and pseudosymmetry, a nearly complete vibrational assignment of the resonance Raman active modes. The spectral perturbations induced by the adsorption of the compounds onto the Ag particles, by comparison with their resonance Raman spectra in solution, were explained in terms of interaction between one C=O⋯H-O group of the chromophore and the silver surface. The intensity reduction of some bands associated with the HOCCC=O groups observed in the drug/DNA complexes was interpreted in terms of changes between the ground and the excited states of the normal coordinates and/or their equilibrium positions. The inferred structures of the complexes were found to be consistent with intercalation between daunorubicin and the DNA fragment d(CpGpTpApCpG) already obtained from X-ray measurements.