Professor John Simons of the University of Utah is supported by the Analytical and Surface Chemistry program to study the molecular mechanism for electron capture dissociation (ECD), a new ionization technique in the field of mass spectrometry. ECD is an important tool for determining primary sequences in peptides and proteins via mass spectrometry. While several mechanisms have been suggested, there is still much that is not understood about the ECD process. Dr. Simons is exploring a newly advanced mechanism for ECD using theoretical methods. Specically, it is thought that the positively charged sites on cations may stabilize their anti-bonding orbitals to the point that electron attachment becomes exothermic, resulting in the observed ionic fragmentation. He is also modeling another approach to ECD, which he calls electron transfer dissociation. In it, low binding energy anions give up their electrons to cations during collisions. A set of peptides with representative amino acids is being studied by unrestricted Hartree- Fock and second-order Moller-Plesset levels of theory in order to determine the electron energies required for cleavages relative to Coulombic stabilization. The resulting thermodynamic properties, energy barrier studies and electronic structure characterization will provide useful information about ECD, which could be potentially important in terms of mass spectrometry applications in proteomics.
Mass spectrometry is an approach that has revolutionized the study of the function and architecture of biological systems. ECD is one of the most promising current mass spectrometry technologies for rapid/flexible protein identification. This work is aimed at understanding how ECD works so that improved instrument performance will be possible.
