PHOTOADDITION OF RUTHENIUM(II)-TRIS-1,4,5,8-TETRAAZAPHENANTHRENE TO DNA AND MONONUCLEOTIDES

Formation of adducts between Ru(TAP)(3)(2+) (TAP = 1,4,5,8-tetraazaphe nanthrene) and DNA has been monitored by gel electrophoresis, UV-vis s pectroscopy and dialysis methods. Adduct formation is found for both s ingle- and double-stranded nucleic acids. The reaction with double-str anded DNA is found to be insensitive to solution pH or aeration. Spect roscopic changes similar to those for DNA are found with GMP in oxygen -free pH 5 solution. However, different reactions occur with GMP at hi gher pH or when the solution contains oxygen. Comparative experiments with double-stranded polyd(G-C) or polyd(A-T) indicate that the ad duct with DNA involves binding to the guanosine moiety. It is proposed that the product is formed by the reaction of the reduced ruthenium c omplex and oxidised guanine species produced by photo-induced electron transfer.