Photoactivated excited states of DNA repair photolyase: Dynamical and semiempircal identification

Abstract

AbstractDNA damage caused by UV light radiation is often naturally repaired in a process initiated by excited state electron transfer from the photoactivated photolyase enzyme to the DNA cyclobutane pyrimidine dimer lesion. The active cofactor in the excited state electron transfer in the photolyase is the two‐electron fully reduced form of the flavin adenine dinucleotide (FADH−). To calculate electron tunneling matrix element and model the DNA binding with photolyase, the LUMO of the FADH− calculated using extended Huckel method was previously chosen from the SCF wavefunctions. Recently, the DNA–photolyase complex was crystallized in its bound form, in good agreement with our previous model in even minute details at the active site. Here we carry out molecular dynamics simulation of the entire complex using the new experimental structure of Anacystis nidulans and identify the low‐lying photoactivated states of the enzyme for the dynamical confirmations. Our results from ZINDO/S CIS calculations are compared with experimental UV spectra, and their implications for excited state electron transfer and energy transfer are discussed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007