252Cf-plasma desorption mass spectrometry of covalently bound nucleic acid adducts: Psoralen-nucleosides photoadducts

Psoralen-nucleosides photocycloadducts have been studied by ²⁵²Cf-Plasma Desorption Mass Spectrometry. The present study involves isolation, high performance liquid chromatography purification and mass spectrometry analysis of the two major monoaddition products formed in the photoreaction of the naturally occurring 8-methoxypsoralen with thymidine. Structural informations have also been obtained concerning photocycloadducts of a new linear psoralen derivative 3-carbethoxypsoralen with thymidine and cytidine. A photobinding of 3-carbethoxypsoralen with adenosine has also been studied. The mass spectra of the adducts have been obtained directly without any derivatization. In all cases they showed molecular and quasimolecular ions in the positive and/or negative mode. It is concluded that ²⁵²Cf-PDMS is a powerful and easy technique for studying xenobiotic-modified nucleic acids.