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BP: Fachverband Biologische Physik

BP 17: Posters: Protein structure and dynamics

BP 17.20: Poster

Montag, 16. März 2015, 17:30–19:30, Poster A

Time-resolved single-frequency IR absorption spectroscopy on photosystem II for investigation of electron-coupled proton transfer — •Philipp Simon, Petko Chernev, and Holger Dau — Freie Universität Berlin, Fachbereich Physik

Photosystem II is a light activated and transmembrane protein performing photosynthetic water oxidation. During the accumulation of four oxidizing equivalents needed for O-O bond formation at the reaction center, a Mn₄Ca-oxo cluster, protons are released and transported over large distances of up to 30 Å(Klaus et al. 2012, PNAS 109, 16035-16040).

Understanding of the process at an atomic level does not only answer fundamental questions of protein functions but can also provide hints on the development of catalysts for artificial photosynthesis, a clean way of producing storable energy.

To analyse the dynamics of these processes a new infra-red absorption experiment is being designed. Its central part is a cw quantum-cascade laser tunable from 1300 to 1650 cm⁻¹ and thus covering the amide I and II regions, the COO⁻ stretching region as well as bands of the quinones or the redox active tyrosine denoted as Y_Z. The time resolution is in the microsecond range, which enables us to observe structural changes and proton transfer dynamics. Here the setup and first measurements on the dynamics of selected vibrational bands, specifically the band assignable to Q_A, will be presented.