Gas‐phase hydration of Mg 2+ complexes with deprotonated uracil, thymine, uridine, and thymidine

The gas‐phase hydration of Mg 2+ 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, [2 U ‐H+Mg] + ) formed as a result of the collision induced dissociation of the respective parent ion (eg, [3 U r ‐H+Mg] + ). The efficiency of gas‐phase hydration of the ions [2 U ‐H+Mg] + and [2 T ‐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.