Manabendra Sarma
Indian Institute of Technology Guwahati, India
Title: Low energy electrons induced damage to selected DNA fragments
Biography
Biography: Manabendra Sarma
Abstract
We have theoretically and computationally investigated the mechanism of low energy electron (LEE) induced DNA damages such as single strand breaks (SSBs) and glycosidic bond cleavage in some selected DNA fragments (Fig. 1) viz., 2¢-deoxycytidine-3¢-monophosphate (3¢-dCMPH) [Fig. 1(a)], 2¢-deoxycytidine-5¢-monophosphate (5¢-dCMPH) [Fig. 1(b)] and sugar-phosphate-sugar (SPS) [Fig. 1(c)]. In this regard, we have used electronic structure theory and our newly implemented local complex potential based time dependent wave packet (LCP-TDWP) approach. Results from our calculations show that in 3¢-dCMPH and 5¢-dCMPH DNA fragments SSB predicted near 1 eV whereas in SPS moiety it appears around 0.6 eV. Further, in case of SPS moiety there are two dissociation channels namely 3¢ C-O and 5¢ C-O bond lesions. Our calculations show that the activation energy barrier for 5¢ C-O bond dissociation is less than of 3¢ C-O bond dissociation pathway. It has also been found that the metastable anion formed after electron attachment to SPS moiety is more long lived (~40-55 fs) than that to 3¢-dCMPH and 5¢-dCMPH fragments (~18-20 fs). On the other hand, the glycosidic bond cleavage in 3¢-dCMPH moiety [Fig. 1(d)] requires higher activation energy than of the SSB in the same fragment and thus least preferred channel compared to SSB.
(a) (b) (c) (d)
Figure 1: Some of the selected DNA fragments. For each fragment bond susceptible for cleavage is marked with an arrow.