PARTICIPATION OF THE NUCLEOBASES IN THE REGIOSELECTIVE BACKBONE FRAGMENTATION OF NUCLEIC-ACIDS - A MOLECULAR-DYNAMICS AND TANDEM MASS-SPECTROMETRIC INVESTIGATION ON A MODEL DINUCLEOSIDE PHOSPHOTRIESTER

The anions (I-III) obtained from O-methyl 5'-O-(5'-deoxythymidine) 3'- O-(2',3'-dideoxyuridine) phosphate by the competitive removal of the 3 -N-H protons of the nucleobases and of the methyl group from the phosp hotriester bond, assume in the gas phase stable conformations as a fun ction of their charge site. The mass-analyzed ion kinetic energy (MIKE ) spectra of I and III show that the regioselective backbone cleavage of the internucleotidic linkage is controlled by the 2'-H proton trans fer to the nucleobase within the 5'-end nucleoside. Similar pathways a re taken by species II when the nucleobase is eliminated as neutral fr om the 5'-end nucleoside. (C) 1997 American Society for Mass Spectrome try.