The Stability of Anionic States of Thymine-Glycine Dimers with Excess Electron

Abstract

It has been demonstrated that low energy electrons (LEEs) can induce serious DNA damages including bases loss and even single and double strand breaks. Experiments also showed that LEE induced DNA damages will be reduced with the presence of amino acids. For understanding of the protection of amino acids to DNA, the stability of 6 kinds of thymine and glycine (T-g) dimers with planar configurations with an excess electron were studied with density functional theory (DFT) method. The results show that, when the excess electron is vertically attached, all the dimers become more active with higher energy. After re-optimization, 4 kinds (66.7%) of T-g dimers become more stable than their neutral states. For the most stable anionic dimer noted as [34-A]-, the excess electron is localized on the thymine, while one proton transfers from the glycine to the thymine. The proton transformation depresses the activities and prevents further reactions of the excess electron. For other three dimers, there is no chemical topology change founded. The glycine attract the excess electron with hydrogen-bonding to the thymine.