title: Effect of quantum tunneling on single strand breaks in a modeled gas phase cytidine nucleotide induced by low energy electron: a theoretical approach.
abstract: Effect of quantum mechanical tunneling on single strand breaks induced by low energy electron (LEE) has been investigated in a modeled gas phase system, 2'-deoxycytidine-3'-monophosphate (3'-dCMPH). The potential energy curves for the sugar-phosphate C-O (3' C-O) bond cleavage have been generated using second order Møller-Plesset perturbation theory at the 6-31+G(d) accuracy level. Results from the electronic structure theory calculations in conjunction with our time dependent calculations for the 3' C-O bond rupture in 3'-dCMPH using local complex potential based time dependent wave packet approach show significant quantum tunneling of the 3' C-O bond from the bound vibrational states above 1 eV of the anionic potential energy curve. A comparison of the fragmentation profile with that of our earlier gas phase investigations based on Hartree-Fock and density functional theory--Becke, 3-parameter, Lee-Yang-Parr methods with 6-31+G(d) basis set is also provided. Further, inspection of the singly occupied molecular orbitals generated at different 3' C-O bond lengths clearly indicates the electron transfer from the low lying base-π(∗) shape resonance state to the phosphate P = O π(∗) orbital of the DNA backbone during the strand breaks. The decisive step during LEE induced strand breaks follows via "charge induced dissociation" (CID) for the metastable anion formed below 1 eV, whereas quantum mechanical tunnel-ing is out-weighted the CID mechanism for the LEE above 1 eV.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781 039, India.
authors.forename: Renjith
authors.initials: R
authors.lastname: Bhaskaran
authors.forename: Manabendra
authors.initials: M
authors.lastname: Sarma
mesh_terms: D053904:DNA Breaks, Single-Stranded / Q000528:radiation effects*; D003843:Deoxycytidine Monophosphate / Q000737:chemistry*; D004583:Electrons; D005740:Gases; D008958:Models, Molecular; D008962:Models, Theoretical; D044367:Phase Transition
chemical_list: D005740:Gases; D003843:Deoxycytidine Monophosphate