Dissociative Electron Attachment to Amides

A comprehensive picture of the quantum phenomena of electron scattering is essential for the characterization and control of molecular systems driven by low-energy impacts that are elementary and important processes not only in radiation-induced chemical reactions but also in other areas, such as the processing of materials, energy flow in molecular systems, and biochemical transformations. At low energy of electrons, dissociative electron attachment (DEA) is a key process involved in the physical and chemical modifications of any target affected by electron interactions. My group conducted a series of experimental studies of gas-phase DEA measurements of compounds with the peptide bond linkage to model proteins, and we considered several reaction channels responsible for damage to these compounds [1]. We focused on gas-phase amides with increasing complexity, ranging from the simplest amide, formamide, to more complex species such as N-ethylformamide and N-ethylacetamide [2,3], to reveal the nature of amide bond cleavage through the DEA process. The location of different resonant states and their corresponding dissociation channels were identified, and with the assistance of quantum chemistry calculations, threshold energies for each dissociation channel were obtained for all studied compounds. Moreover, our results indicated that in all these molecules, the dissociation of the amide bond results in a double resonant structure with peaks at approximately 5 and 9 eV. Interestingly, such resonant structures for corresponding fragments were also observed in gas-phase peptides. This common finding implies the fundamental characteristic for breakage of the amide bond and is particularly important to formulating a general mechanism for molecular dissociation.