Unimolecular reactivity upon collision of uracil-Ca2+ complexes in the gas phase: Comparison with uracil-M+ (MÂ =Â H, alkali metals) and uracil-M2+ (MÂ =Â Cu, Pb) systems

► Interaction of Ca2+ ions with uracil studied by MS/MS and DFT calculations. ► Use of labeled uracils for more detailed information. ► Potential energy surfaces of the various fragmentations explored. ► Comparison with the reactivity induced by other monocations or dications.