Does removal of hydrogen change the electron energy-loss spectra of DNA bases?

Quantum-chemical calculations using the CNDO/2 method are applied to radicals produced by cleaving hydrogen from the DNA bases adenine, guanine, cytosine, and thymine. The resulting sequences of occupied molecular orbitals show that the loss of hydrogen atom in most cases leads to the loss of one phi electron. Consequently the phi electron part of the energy-loss spectra will change considerably. In view of this, it is possible that the change of the electron energy-loss spectra due to irradiation, as observed by Isaacson et al., might be caused by the loss of hydrogen atoms. Such damage does not influence the electron-microscopical image appreciably, as long as no deleterious secondary processes are initiated.