Gas-phase hydrogen/deuterium exchange of adenine nucleotides

Gas-phase hydrogen/deuterium exchange reactions of (de)protonated (sodiated) adenosine-5'-mono-, di- and triphosphate ions with CD(3)OD, CD(3)CO(2)D and ND(3) were achieved using a combination of electrospray ionization and Fourier transform ion cyclotron resonance mass spectrometry. The reaction kinetics are dependent on factors such as the charge state, the phosphate chain length, the properties of the exchange reactants and the sodium content. The results indicate that the overall H/D exchange may involve specific sites even if endowed with high energetic barriers. The enhanced reactivity exhibited by adenosine polyphosphate ions compared with adenosine-5'-monophosphate suggests a critical role of the polyphosphate chain in rendering conformationally accessible remote H-donor sites. Low-energy collision-induced dissociation of (sodiated) adenine nucleotides anions supports the aptitude of the (poly)phosphate chain in probing distant sites via the intermediacy of a cyclic structure.