Coupling infrared multiphoton dissociation spectroscopy, mass-spectrometry and ion mobility spectrometry for the determination of structures of angiotensin II cations

Gas-phase structures of mass-selected singly- and doubly charged angiotensin ions have been determined by means of infrared multiple photon dissociation (IRMPD) spectroscopy and ion mobility spectrometry. Simulation of IRMPD spectra at the DFT level provides the location of the proton on the Arg side-chain in the case of the singly charged species. Interpretation of the ion mobility data suggests that the structures of singly- and doubly charged species are rather similar except for an internal proton transfer.