Impact of the Electron Attachment to the Alanyl Glycine and Glycyl Alanine Conformers

The low-energy electrons (LEEs) attachment to biological molecules can result in irreversible damage. The attachment of LEEs to DNA, amino acids, peptides, and proteins has a significant impact due to their diverse biological applications. This study focuses on the effect of the electron attachment to the conformers of Alanyl Glycine and Glycyl Alanine dipeptide molecules. The study used a quantum mechanical (QM) approach to extract the low-lying conformers of the dipeptide molecules and performed atom-centered density matrix propagation (ADMP) simulation to assess the impact of the electron attachment at 2.0 eV. We observed a dipole-bound state to a π* valence-bound state transition based on the singly occupied molecular orbitals (SOMOs) analysis. It was observed that different conformers have distinct impacts on electron attachment to the system, and strong intramolecular H-bonds give extra stability to the system toward the dissociative electron attachment (DEA). The latter part of the work focuses on identifying two low-lying π* resonance states, as the DEA process involves a π* to σ* transition, which was studied using the complex absorbing potential (CAP) approach. Our results align reasonably well with experimental observations for the Alanyl Glycine and Glycyl Alanine molecules in the gas phase.