Frankfurt 2006 – wissenschaftliches Programm
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Q: Quantenoptik und Photonik
Q 60: Laserspektroskopie I
Q 60.7: Vortrag
Donnerstag, 16. März 2006, 12:40–12:55, HII
Photodynamics of the small BLUF protein BlrB from Rhodobacter sphaeroides — •Peyman Zirak1, Alfons Penzkofer1, Tina Schiereis2, Peter Hegemann2, Astrid Jung3, and Ilme Schlichting3 — 1Institut II * Experimentelle und Angewandte Physik, Universität Regensburg, Universitätstrasse 31, D-93053 Regensburg, Germany — 2Institut für Biologie, Experimentelle Biophysik, Humboldt-Universität zu Berlin, Invalidenstr.42, D-10115 Berlin, Germany — 3Max-Planck-Institut für medizinische Forschung, Abteilung Biomolekulare Mechanismen, Jahnstrasse 29, D-69120 Heidelberg, Germany
The BLUF protein BlrB from the non-sulphur anoxyphototrophic purple bacterium Rhodobacter sphaeroides is characterized by absorption and emission spectroscopy. The dark-adapted protein exists in two different receptor conformations with different sub-nanosecond fluorescence lifetimes. Some of the flavin-cofactor (ca. 8 %) is unbound in thermodynamic equilibrium with the bound cofactor. The two receptor conformations are transformed to putative signalling states of decreased fluorescence efficiency and shortened fluorescence lifetime by blue-light excitation. In the dark both signalling states recover back to the initial receptor states with a time constant of about 2 s. A quantum yield of signalling state formation of about 90 % was determined by intensity dependent transmission measurements. Extended blue-light excitation causes unbound flavin degradation and bound cofactor conversion to the semiquinone form. The flavin-semiquinone further reduces and the reduced flavin re-oxidizes back in the dark.