Simulations of the fragmentation of the [V-H]− anions as formed upon DEA to L-valine

Abstract

The dissociation of proteins due to radiation and charged particles is an important process which is not well understood. Measurements of the fragmentation of such large molecules using mass spectrometers can be difficult to describe and understand since for many of the masses observed there are more than one possible combination of atoms. We have simulated the metastable decay of the anions formed by dissociative electron attachment (DEA) to L-Valine to show that it is possible to recognize some of the observed mass to charge ratios by their further fragmentation. By using computer simulations of the classical dynamics of the ions and finding minimum energy paths for intermolecular atom transfer and reorganization, we have identified molecular combinations that can be assigned to the measured m/Z ratios. The atomic forces in these calculations are obtained from density functional theory using a gradient dependent functional.