The gas-phase hydration of Mg2+ complexes with deprotonated uracil (U), thymine (T), uridine (Ur , uracil riboside), and thymidine (Tdr , 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, [3Ur -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+Ur -H+Mg]+ was much higher than that of gas-phase hydration of the ion [T+Tdr -H+Mg]+ . On the basis of the mass spectra obtained and the performed molecular modelling, it was concluded that in the ion [T+Tdr -H+Mg]+ , we deal with a steric hindrance due to the presence of a sugar moiety, which affects water attachment. In the ion [U+Ur -H+Mg]+ , the position of the sugar moiety does not affect water attachment.
Keywords: electrospray ionization; hydration; mass spectrometry; nucleosides; thymine; uracil.
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