H-atom loss and migration in hydrogen-rich peptide cation radicals: The role of chemical environment

- The quantum description of the ECD/ETD mechanism could be influenced by the chosen DFT functional.
- M06-2X is an adequate choice if it provides the correct ground state, otherwise LC-BLYP should be chosen.
- The stronger the total H-bond interactions with an ammonium, the smaller its electron affinity.
- Ammonium group without any free N-H is not as able as backbone peptide to capture an electron.
- H loss is slightly favored for ammonium groups which are not highly intramolecularly “solvated”.