The role of the solvent on proton localization and zwitterion formation in amino acids and small peptides: influence on structure and dynamics

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The subject of the collaboration is the understanding of proton or hydrogen transfer reactions in neutral and ionized amino acids and small peptides in the gas phase. These processes are controlled by intramolecular properties but are equally influenced or even catalyzed by the solvent. The methodological approach is the use of spectroscopic structural data for the in-depth interpretation of dynamical studies on fast (ns) and an ultra-fast (fs) time-scale. From a fundamental point of view, the aim is to follow the evolution of the properties of molecular systems as a function of the number of solvent molecules which surround them. The four groups have a long-standing experience of such studies with elementary model systems and propose to extend them to protein components. The different aspects of proton transfer: proton localization, zwitterion formation, charge migration and fragmentation, will be investigated by means of complementary approaches. A single experiment cannot alone provide a full answer to the studied problems. For example, neutral and charged amino acids or peptides cannot be handled with the same experimental techniques. Some experimental approaches have already been developed by the participating teams and will be transferred from one group to another (e.g. IR depletion). Some others have up to now never been used and they will require the full cooperation of the different teams (e.g. time-resolved fragmentation of peptides with simultaneous detection of ionic and neutral products). The cooperation program will investigate the feasibility of a long-standing goal of advanced mass-spectrometry: the introduction of laser-controlled selective dissociation of protein fragments to provide structural information on fragments and non-covalent complexes through IR spectroscopy, down to the single ion detection level, for protein-sequencing in Proteomics.