Gas-phase hydration of Mg2+ complexes with deprotonated uracil, thymine, uridine, and thymidine

The gas-phase hydration of Mg2+ complexes with deprotonated uracil (U), thymine (T), uridine (U-r, uracil riboside), and thymidine (T-dr, thymine deoxyriboside) was studied. The aim of the work was to analyze the hydration of product ions (eg, [2U-H+Mg](+)) formed as a result of the collision induced dissociation of the respective parent ion (eg, [3U(r)-H+Mg](+)). The efficiency of gas-phase hydration of the ions [2U-H+Mg](+) and [2T-H+Mg](+) was similar. However, the efficiency of gas-phase hydration of the ion [U+U-r-H+Mg](+) was much higher than that of gas-phase hydration of the ion [T+T-dr-H+Mg](+). On the basis of the mass spectra obtained and the performed molecular modelling, it was concluded that in the ion [T+T-dr-H+Mg](+), we deal with a steric hindrance due to the presence of a sugar moiety, which affects water attachment. In the ion [U+U-r-H+Mg](+), the position of the sugar moiety does not affect water attachment.