Psoralen-DNA photoreaction: controlled production of mono- and diadducts with nanosecond ultraviolet laser pulses.

Samples of DNA which contain adducts of a new psoralen derivative, but no cross-links, have been prepared by irradiating mixtures of DNA and the derivative with single, 15-nanosecond pulses of laser light. Succeeding pulses introduce cross-links. The ability to rapidly and selectively create monoadducts and corss-links may allow the use of psoralens as probes of dynamic processes in living cells.