THERMOSPRAY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC MASS-SPECTRAL ANALYSES OF THE PHOTOPRODUCTS OF DTPDT AND DTPDU

The photoproducts of the dinucleoside monophosphates dTpdT and dTpdU have been examined by thermospray high-performance liquid chromatography/mass spectrometry in the positive and negative ion modes. The photoproducts included the cis-syn and trans-syn cyclobutane dimers, the 6-4 and Dewar 6-4 pyrimidine-pyrimidinone photoadducts and the uracil photohydrates of dTpdU. Molecular ions and several fragment ions are observed in all cases. It is shown that the cyclobutane dimers, 6-4 photoadducts and Dewar 6-4 photoadducts can be easily distinguished from each other and from the parent dinucleoside monophosphates by fragmentation pattern differences. Using single-ion monitoring these photoproducts could be detected st the low-picomole level.