THE ISOLATION AND CHARACTERIZATION OF PYRIMIDINE-PSORALEN PHOTOADDUCTS FROM DNA

Abstract

We have examined the photoadducts of 4'-hydroxymethyl- 4,5',8-trirnethylpsoralen (HMT) and native DNA. Five DNA-HMT monoaddition products have been isolated and characterized, corresponding to three deoxythymidine-HMT and two deoxyuridine (derived from deoxycytidine) -HMT adducts. Structural assignments are based on high resolution mass spectrometry and {sup 1}H NMR studies, including homonuclear spin decoupling and nuclear Overhauser effect (NOE) experiments. The results of this study indicate that (1) a limited number of nucleoside-psoralen adducts are formed with native, double-stranded DNA, and (2) the stereochemistry of the adducts is apparently determined by the geomertry of the non-covalent intercalative complex formed by HMT and DNA prior to irradiation