Metallation kinetics of a free base porphyrin in surface-enhanced resonance Raman scattering active Ag colloid system as a probe of porphyrin-nucleic acids 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) polynucleotides have been studied by using surface-enhanced resonance Raman scattering spectroscopy (SERRS). SERRS spectra of these complexes have been recorded during time-scale varying from minutes to days, and the differences in the course of the porphyrin metallation, indicating different accessibility of the metal surface for the porphyrin con in the case of particular complexes, have been monitored. The results obtained for the three studied systems are in very good agreement with the expected dominant types of the porphyrin interaction with the nucleic acids, i.e., intercalation in the case of poly(dG-dC) and external binding in the case of poly(dA-dT), (C) 1999 Elsevier Science B.V. All rights reserved.