Definition

A furocoumarin that intercalates with DNA, inhibiting DNA synthesis and cell division. Psoralen is used in Photochemotherapy with high-intensity long-wavelength UVA irradiation. Psoralens are tricyclic furocumarins and have a strong tendency to intercalate with DNA base pairs. Irradiation of nucleic acids in the presence of psoralen with long wave UV (~360 nm) results in the 2+2 cyclo- addition of either of its two photoreactive sites with 5,6-carbon bonds of pyrimidines resulting in crosslinking double-stranded nucleic acids.