Photoreaction channels of the guanine–cytosine base pair explored by long-range corrected TDDFT calculations

Abstract

Electronic supplementary information (ESI) available: vertical excitation energies calculated with basis sets of double-zeta plus polarization quality, and additional figures of potential energy profiles. 2 AbstractPhotoinduced processes in the Watson-Crick guanine-cytosine base pair are comprehensively studied by means of long-range corrected (LC) TDDFT calculations of potential energy profiles using the LC-BLYP and CAM-B3LYP functionals. The ab initio CC2 method and the conventional TDDFT method with the B3LYP functional are also employed to assess the reliability of the LC-TDDFT method. The present approach allows us to compare the potential energy profiles at the same computational level for excited-state reactions of the base pair, including single and double proton transfer between the bases and nonradiative decay via ring puckering in each base. In particular, long-range correction to the TDDFT method is critical for a qualitatively correct description of the proton transfer reactions. The calculated energy profiles exhibit low barriers for out-of-plane deformation of the guanine moiety in the locally-excited state, which is expected to lead to a conical intersection with the ground state, as well as for single proton transfer from guanine to cytosine with the well-known electron-driven proton transfer mechanism. Thus the present results suggest that both processes can compete in hydrogen-bonded base pairs and play a significant role in the mechanism of photostability.3

Proton/Hydrogen Transfer Mechanisms in the Guanine–Cytosine Base Pair: Photostability and Tautomerism

“…74,80,81,82,83 At first, the proton (H 1 ) in the central hydrogen-bond network migrates from G to C (see Figure 1). Next, it returns to the purine (G) moiety, which supports the stepwise pathway.…”

Hydrogen-bond-directed-linking solving transparence-efficiency tradeoff in nonlinear optical molecule

“…The transition properties of (N C C C H) n , including the transition energy E and oscillator strength f 0 , were calculated by the time-dependent density-functional theory (TDDFT) approach using the LC-BLYP [49,50] functionals, which perform well for charge transfer excitations. Besides, the results of TDDFT are compared with those of the configuration interaction singles (CIS) method.…”

Computational Modeling of Photoexcitation in DNA Single and Double Strands

“…The conformation of the Watson-Crick base pair was found to be the key to the photostability of Gua·Cyt [311], which may even involve double proton transfer in the gas phase [312]. There are also experiments supporting a proton-transfer mechanism in alternating G/C double strands [e.g., (dGdC) n ·(dCdG) n ], which, however, strongly depends on the base sequence [313].…”