Photoinduced crosslinking of double-helical DNA by psoralen covalently linked to a triple helix-forming oligonucleotide under near-physiological conditions.

Stable triplexes have been generated under near-physiological conditions by the introduction of the C and T base analogues 3-methyl-2-aminopyridine-2'-deoxyriboside and 5-(3-aminoprop-2-ynyl)-'-deoxyuridine into psoralen-conjugated triplex-forming oligonucleotides. After irradiation with UV light at 365 nm, photo-induced cross-linking of the TFO to double-helical DNA was observed by UV-melting analysis and fluorescence measurements.