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 phosphotriester bond, assume in the gas phase stable conformations as a function 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 transfer to the nucleobase within the 5'-end nucleoside. Similar pathways are taken by species II when the nucleobase is eliminated as neutral from the 5'-end nucleoside. (C) 1997 American Society for Mass Spectrometry. OI sindona, giovanni/0000-0002-5623-5795; Liguori, Angelo/0000-0003-4483-2506

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 phosphotriester bond, assume in the gas phase stable conformations as a function 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 transfer to the nucleobase within the 5'-end nucleoside. Similar pathways are taken by species II when the nucleobase is eliminated as neutral from the 5'-end nucleoside