Resonance Raman spectra and transform analysis of anthracyclines and theircomplexes with DNA

The absorption, second-derivative and resonance Raman spectra of some anthr acyclines, namely idarubicin, epirubicin and 11-deoxycarminomycin in H2O an d D2O solutions, and their complexes with DNA in H2O solutions, were measur ed. Transform analysis that links resonance Raman band intensities to reson ant absorption was applied to idarubicin, epirubicin and their complexes wi th DNA to obtain the Franck-Condon factors. The results allowed us to provi de details on the nature of the resonance Raman active modes, the mechanism of their resonant enhancement and the chromophore-DNA interaction. In part icular, an interpretation involving excited-state charge transfer, associat ed in some cases with excited-state proton transfer, is proposed. This help s to rationalize the observed variations of the intensities of Raman-active modes of free anthracyclines in terms of variation of the transition momen t direction. The intercalation of the chromophore among the DNA base pairs induces, via excitonic interactions, a change in both the magnitude and the direction of the transition moment of the chromophore. Copyright (C) 2001 John Wiley & Sons, Ltd.