Collision-Induced Dissociation of Hydrated Adenosine Monophosphate Nucleotide Ions: Protection of the Ion in Water Nanoclusters

Fragmentation of singly charged anions of adenosine 5'-monophosphate (${\mathrm{AMP}}^{\ensuremath{-}}$) induced by collisions with neutral atoms (Ne, Na) has been studied at a collision energy of 50 keV. The experiments were performed with isolated ${\mathrm{AMP}}^{\ensuremath{-}}$ as well as with ${\mathrm{AMP}}^{\ensuremath{-}}$ anions nanosolvated in a cluster with a given number $m$ of water molecules. In the first case, the dominant fragmentation channels concern the loss of adenine, $\mathrm{PO}_{3}{}^{\ensuremath{-}}$ and ${\mathrm{H}}_{2}\mathrm{PO}_{4}{}^{\ensuremath{-}}$. In the latter, loss of water molecules becomes the dominating process, and the ${\mathrm{AMP}}^{\ensuremath{-}}$ ion is fully protected when $m$ is larger than $\ensuremath{\sim}13$. The observed fragment distributions are well described with the model of an evaporative ensemble.