Sensitized photomodification of DNA by binary systems of oligonucleotide conjugates. III. Two-photon sensitization

Site-specific modification of single-stranded DNA by oligonucleotide deriva tives of p-azido-O-(4-aminobutyl)tetrafluorobenzaldoxime sensitized by an o ligonucleotide derivative of pyrenylethylamine was studied. Upon irradiatio n with the long-wave UV light (365-390 nm) of a DNA target-oligonucleotide reagent complementary complex, a considerable increase in the rate of sensi tized photomodification at the G11 residue of the target relative to the di rect photomodification was observed owing to the singlet-singlet energy tra nsfer from the sensitizer onto the photoreagent. Upon simultaneous irradiat ion of the complex with UV and visible light in the region of the triplet-t riplet absorption of pyrene (360-580 nm), an additional increase in the mod ification rate and a change in its site-direction (from the G11 to T13 resi due) occured through the two-photon triplet-triplet sensitization. The tota l extent of the structure photomodification amounted to 80%.