Psoralen C2 at the 5’-terminus of an oligonucleotide serves effectively as a cross-linking reagent in double-stranded oligonucleotides. The 6 atom spacer arm of Psoralen C6 allows cross-linking with a triplex oligonucleotide strand. Click Chemistry with psoralen azide and one of our many nucleosidic and non-nucleosidic alkyne derivatives has the potential to generate a variety of practical cross-linkers. The well known reversible cross-linking behavior of psoralen with an adjacent thymidine residue could be very useful.
