Structure and collision-induced dissociation of the protonated cyclo His-Phe dipeptide: mechanistic studies and stereochemical effects

The role of stereochemical factors on the structure and fragmentation paths protonated cyclic dipeptide cyclo histidine–phenylalanine is studied under ion traps conditions by combining tandem mass spectrometry, laser spectroscopy, quantum chemical calculations dynamics simulations. Vibrational spectroscopy obtained Infrared Multiple Photon Dissociation (IRMPD) reveals a small difference between two diastereomers, c- $$\hbox {LLH}^{+}$$ {LDH}^{+}$$ , arising mainly from ancillary CH... $$\uppi $$ interactions. In contrast, there strong influence residues chirality collision-induced dissociation (CID) processes. Chemical simulations rationalize this effect evidence that proton mobility takes place, allowing isomerization to intermediate structures are different for resulting in barriers mobility. This related protonation imidazole ring. It contrasts with minute effects observed other dipeptides which borne an amide CO.