Radical cations of DNA bases: some insights on structure and fragmentation patterns by density functional methods

In this work the DNA bases and their radical cations are investigated by an hybrid Hartree-Fock/density functional model. The calculated geometries and ionization energies are in good agreement with the available experimental data, confirming the reliability of this approach for the study of open shell systems. A critical comparison between the electronic and geometric structures of the radical cations and those of the neutral DNA bases, together with an analysis based on the natural bond orbital theory, offer some insights on the fragmentation patterns recorded in the experimental mass spectra as well as a tentative explanation of the different behavior of thymine and cytosine. (C) 2000 Elsevier Science B.V.