Trimethylsilyl derivatization of nucleic acid anions in the gas phase

Abstract

Ion-molecule reactions between nucleic acid anions, [M-nH]n-, formed via electrospray ionization, and trimethylsilylchloride have been investigated in an ion trap mass spectrometer at a helium bath gas pressure of 1 mtorr. Three types of reactions are observed: (i) SN2(Si) when n > 1; (ii) adduct formation when n = 1; and (iii) addition followed by elimination of HCl when n = 1 and where an acidic phosphate proton is present (e.g., 5′-pdA). The kinetics of these reactions have been studied for various anions derived from the following deoxyadenosine species: 5′-pdA; 5′-pppdA, 5′-d(AA)-3′; 5′-d(AAA)-3′ and 5′-d(AAAA)-3′. The following reactivity order is observed: [M-2H]2- of 5′-pppdA > [M-2H..