Düsseldorf 2007 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 26: Poster: Biomolecules

MO 26.4: Poster

Dienstag, 20. März 2007, 16:30–18:30, Poster A

Femtosecond transient absorption studies on the photolyase of Thermus thermophilus and their chromophores FMN and FAD — Annette Brunsen, •Tiago Buckup, Tobias Klar, Lars-Oliver Essen, and Marcus Motzkus — Physikalische Chemie, Philipps Universität Marburg, D-35032 Marburg, Germany

CPD-photolyases are enzymes which use blue light to repair UV-induced DNA damage. Flavins, like FAD and FMN, are the corresponding enzyme cofactors responsible for light absorption and the first step in the DNA repair reaction. In spite of the importance of photolyase in nature, very little is known about the ultrafast dynamics after the initial light absorption. In this work we investigate the mutant CPD-photolyase of Thermus thermophilus, which contains FAD only, with femtosecond transient absorption. The dynamics of the mutant photolyase is compared to the transient absorption signal of isolated FAD and FMN in different solvents. After excitation at 450 nm, ground-state bleach, excited-state absorption and stimulated emission could be measured between 450-900 nm. A fast solvent dependent time constant (2-10 ps) was observed and related to the closed form of FAD and dimerisation of FMN. Another long time constant is associated with the open and non-dimerised form. The transients of a mutated photolyase can be compared to those of FAD in water.