This presentation encompasses the quantitative dissociation of protonated methionine, H+Met, which is examined in detail through computational study. Experimental mass spectrometry results suggest that primary dissociation pathways of H+Met following collision with neutral Xe are deamidation (NH3), CO+H2O loss, and CH3SH loss, which are then followed by three subsequent dissociations. However, it is not possible to determine the mechanism by which fragmentation occurs experimentally. This computational study utilizes potential energy, transition state, and single point energy calculations to investigate the mechanism and associated energetics of these dissociation channels. The computational results for the elementary steps for the primary and secondary losses from H+Met are in good agreement with the experimentally obtained dissociation energies.

Mechanism of decomposition of protonated methionine: A computational study

2019 Spring National Meeting

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