Ab Initio Calculations of DNA Nucleobases and Simulation of Electron Diffraction Patterns

SIDDIQUI, K.; CORTHEY, G.; HASEGAWA, T.; HAYES, S. A.; PICHUGIN, K.; SCIAINI, G.; MILLER, R. J. D.; WHITAKER, B.

Frauenchiemsee

Congreso; 16th European Symposium on Gas-Phase Electron Diffraction; 2013

Deoxyribonucleic acid (DNA) bases, i.e., adenine, thymine, cytosine and guanine are the building blocks of life. They exhibit interesting photophysics in the ultra-violet/visible range in that, after excitation, they are rapidly deactivated (t deactivation approx. 100 fs to 1 ps). This ultrafast deactivation is proposed to be the reason behind DNA´s remarkable photostability and evolution of life on Earth [1]. Ultrafast Electron Diffraction (UED) is a technique ideally suited to studying such processes with both atomic spatial and femtosecond time resolution [2]. We are interested in trying to identify key states of DNA bases that play a part in the deactivation and hence elucidate the mechanism of DNA photostability using a combination of Ab inito calculations at the complete active space self-consistent field (CASSCF) level and UED. In this poster, we present some results from Ab initio calculations done on adenine and thymine. The structures obtained from these calculations are used to simulate electron diffraction patterns as an experimental feasibility study. 1 Hernadez et al ,Chem. Rev. 2004, 104,1977?2019. 2 G.Sciani and R.J.D Miller, Rep. Prog. Phys. 2011, 74 , 96101.