Metallation kinetics of a free base porphyrin in surface-enhanced resonance Raman scattering active Ag colloid system as a probe of porphyrin-nucleicacids interaction

Complexes of the cationic free base 5,10,15,20-tetrakis (1-methyl-4-pyridyl ) porphyrin with DNA, double-stranded poly(dA-dT) and poly(dG-dC) polynucle otides have been studied by using surface-enhanced resonance Raman scatteri ng spectroscopy (SERRS). SERRS spectra of these complexes have been recorde d during time-scale varying from minutes to days, and the differences in th e course of the porphyrin metallation, indicating different accessibility o f the metal surface for the porphyrin con in the case of particular complex es, have been monitored. The results obtained for the three studied systems are in very good agreement with the expected dominant types of the porphyr in interaction with the nucleic acids, i.e., intercalation in the case of p oly(dG-dC) and external binding in the case of poly(dA-dT), (C) 1999 Elsevi er Science B.V. All rights reserved.