Hydrogen/deuterium exchange of nucleoside analogs in a quadrupole ion trap mass spectrometer

Hydrogen/deuterium (HID) exchange reactions of protonated nucleoside analogs, including several antibiotics, are reported. Protonated nucleoside analogs contain a wide variety of labile hydrogens and undergo a different number of exchanges when reacted with the reagents ND3 and CH3OD. All of the protonated nucleoside analogs, except for tubercidin and cytidine, exchanged all of their labile hydrogens plus the protonating hydrogen when reacted with ND3. The protonated analogs underwent a more selective exchange with CH3OD, and only zidovudine exchanged all of its labile hydrogens plus the protonating hydrogen. The results indicate that HID exchange involves both rings of the nucleoside analogs despite fairly large differences in basicities of specific sites in the two rings, suggesting that the protonating hydrogen can remain mobile or that hydrogen-bond formation between the deuterated reagent and the analyte may occur across the two rings. (Int J Mass Spectrom 190/191 (1999) 161-170) (C) 1999 Elsevier Science B.V.