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MO: Fachverband Molekülphysik
MO 15: MO Poster 3
MO 15.5: Poster
Mittwoch, 11. März 2020, 17:00–19:00, Empore Lichthof
pH-Dependence of Retinal Isomerization in Anabaena Sensory Rhodopsin — •Oskar Kefer1, Rei Abe-Yoshizumi2, Hideki Kandori2, and Tiago Buckup1 — 1Physikalisch-Chemisches Institut, Ruprecht-Karls Universitat Heidelberg, Germany — 2OptoBioTechnology Research Center, Nagoya Institute of Technology, Japan
Anabaena sensory rhodopsin (ASR) is an unique microbial retinal protein. In dark adaption the protein contains mostly AT- (all-trans,15-anti) retinal and in photo-equilibrium (light adaptation) a combination of 13C- (13-cis,15-syn) or AT-isomers are present. This enables the investigation of the ultrafast isomerization of these two isomeric chromophores in the same protein environment. pH-Titration experiments in acidic solution have shown two major pKa values (with 4.0 and 6.5) for protonation of residual amino acids, which are involved in the retinal to protein hydrogen-bonding network and influence the steady-state absorption. We use ultrafast transient absorption spectroscopy to investigate the photo-reaction of ASR until the formation of photoproduct "K" under dark and light adaptation. The investigated pH values are chosen to give insight into the effect of the protonation of these amino acids on the isomerization. Our findings indicate a (i) significant acceleration of initial dynamics for AT only for pH 3 and deceleration of "K"-Formation at more acidic solutions and (ii) a monotonic acceleration of the isomerization dynamics of 13C-isomer with increasing pH.