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Physical Chemistry Chemical Physics 14 (2012) 8000-8004
Decomposition of methionine by low energy electrons
J. Kopyra, I. Szamrej, H. Abdoul-Carime1, B. Farizon1, M. Farizon1

In this work, we present the results from low energy (<12 eV) electron impact on isolated methionine, Met. We show that dissociative electron attachment is the operative mechanism for the sulfur content amino-acid fragmentation. The two most dominant fragments are attributed to the (Met-H)− and (C4NOH5)− ions that are formed at energy below 2 eV. The formation of the latter anion is accompanied by the loss of neutral counterparts, which are most likely a water molecule and highly toxic methanethiol, CH3SH. Further fragments are associated with the damage at the sulfur end of the amino acid, producing the methyl sulfide anion CH3S− or sulfur containing neutrals. In the context of radiation induced damage to biological material at the nano-scale level, the present interest of methionine arises from the implication of the molecule in biological processes (e.g., S-adenosyl methionine for the stimulation of DNA methyltransferase reactions or protein synthesis).
1 :  IPNL - Institut de Physique Nucléaire de Lyon