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MO: Fachverband Molekülphysik

MO 18: Biomolecules and Electron Transfer

MO 18.2: Talk

Friday, March 10, 2017, 11:15–11:30, N 25

Characterization of Charge Separated States in (6-4)-Photolyase - Mechanistic Implications — •Mara Oßwald and Benjamin Fingerhut — Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Str. 2A, D-12498 Berlin

The UV irradiation of DNA causes the formation of cyclobutane pyrimidine dimers and of the (6-4)-photoproduct. The latter can be reverted by the enzyme (6-4)-photolyase. Triggered by light induced electron transfer, (6-4)-photolyase catalyzes the transfer of a hydroxyl group in addition to covalent bond cleavage. We present results on the effect of enzyme-electrostatics on the energetics of charge separated states in the (6-4)-photoproduct repair complex. Excited state calculations in gas phase and with enzyme were conducted using a QM/MM framework and TDDFT methods with modern long-range-corrected functionals as well as local coupled cluster linear response as ab-initio benchmark. By including all relevant molecules in the QM-region (ISO, ADE, (6-4)-lesion, His365, His369), the calculations account for the, up to date, largest QM-region regarding the (6-4)-repair complex. The results show that the electrostatics of the enzyme substantially affect the charge transfer (CT) states of the system. Most notably, the CT states from the isoalloxazine ring to the (6-4)-lesion are destabilized and become inaccessible. While the (6-4)-photoproduct acts as electron acceptor in gas phase, a radical cationic state, arising from the reverted electron transfer direction, is favored once the enzyme is taken into account.