ASPIRIN-DNA INTERACTION STUDIED BY FTIR AND LASER RAMAN DIFFERENCE SPECTROSCOPY

The interaction of calf-thymus DNA with aspirin is investigated in aqu eous solution at pH 7-6 with drug/DNA(phosphate) molar ratios of r = 1 /40, 1/20, 1/10, 1/5, 1/2, 1 and 2. Fourier transform infrared (FTIR) and laser Raman difference spectroscopy are used to determine drug bin ding sites, sequence preference and DNA secondary structure, as well a s the structural variations of aspirin-DNA complexes in aqueous soluti on, Spectroscopic evidence showed that at low aspirin concentration (r = 1/40), drug-DNA interaction is mainly through the backbone PO2 grou ps and the A-T base pairs, Such interaction largely perturbs the phosp hate vibration at 1222 cm(-1) and the A-T bands at 1663 and 1609 cm(-1 ) with no major helix destabilization. At higher drug concentration (r > 1/20), the participation of the G-C bases in drug-DNA complexation was evident by strong perturbations of the guanine and cytosine vibrat ions at 1717 and 1494 cm(-1), with a partial helix destabilization. A major alteration of the B-DNA structure towards A-DNA occurs on drug c omplexation, The aspirin interaction was through anion CO and COOCH3 d onor atoms with those of the backbone PO2 group and DNA bases donor si tes (directly or indirectly via H2O molecules).