Berlin 2018 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 29: Statistical Physics of Biological Systems I (joint session BP/DY)

BP 29.2: Vortrag

Donnerstag, 15. März 2018, 09:45–10:00, H 2013

A reaction center driven by entropy — •Franz-Josef Schmitt, Zuleyha Yenice Campbell, Mai Vi Bui, and Thomas Friedrich — Technische Universität Berlin, Sekr. PC 14, Straße des 17. Juni 135, 10623 Berlin

The phototrophic cyanobacterium Halomicronema hongdechloris contains chlorophyll a and f in photosystem II. The ratio of Chl f to Chl a is reversibly changed from 1:8 under illumination with far red light (720-730 nm) to a very low level of Chl f under white-light culture conditions. Phycobiliproteins exhibit highly efficient excitation energy transfer (EET) to Chl a and from there to Chl f within 200 ps apparent transfer time if H. hongdechloris grown under far red light is illuminated with 630 nm laser radiation which is absorbed by phycobilisomes. However excitation energy localized on Chl f shows long lifetime of more than 1 ns. Questions arise about composition of the reaction center and possible primary charge separation driven by Chl f. Our Simulations and thermodynamic considerations suggest that the time- and wavelength-resolved ps fluorescence data can be explained assuming light-induced far red-shifted traps of excitation energy localized on Chl f in the light harvesting antenna while the large majority of Chl a is strongly coupled to these Chl f traps driving the uphill EET from Chl f to Chl a by entropic force.