Characterization of polyamine-induced aggregates of oligodeoxyribonucleotides by Raman spectroscopy

We have studied by Raman spectroscopy the interaction of a 15-mer double-stranded oligodeoxynucleotide with repetitive guanine-cytosine pairs and biogenic polyamines spermine, spermidine and putrescine. Room temperature Raman spectra of solutions containing 60 mM (phosphate) oligonucleotide and different polyamine concentrations, between 10 and 75 mM, were recorded at physiological pH and ionic conditions. The spectra showed a noticeable hypochromism for both base and phosphate bands, which have been related with the formation of highly ordered aggregated structures in solution. Aggregates would be stabilized by electrostatic attractions between oligonucleotide phosphate groups and polyamine amino protonated groups in addition to interactions with base residues. Evidences of a partial B --> Z transition have also obtained for spermine and spermidine but not for putrescine. (C) 2001 Elsevier Science B.V. All rights reserved.