Antigenicity of poly(dA-dT) . poly(dA-dT) photocrosslinked with 8-methoxypsoralen.

We report the formation of photocrosslink (diad-duct) between duplex poly(dA-dT) and 8-methoxypsoralen inferred on the basis of UV and fluorescence characteristics, Tm, nuclease S1 digestibility, and hydroxyapatite column chromatography. The photocrosslink was highly immunogenic inducing high titer antibodies in goat. The affinity constant of antigen-antibody interaction quantitated by precipitin titration was found to be 2.71 x 10(9) M-1, calculated by Langmuir isotherm plot. These antibodies were highly specific showing recognition of almost exclusively of nucleic acid-furocoumarin photoadducts and could be used as a probe to detect and quantitate DNA modified with furocoumarins in health and disease. Antibodies against poly(dA-dT)-furocoumarin photocrosslink might be a better probe because of repeated A-T sequences on the immunogen.