Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 18: Biomolecules and Electron Transfer

MO 18.5: Talk

Friday, March 10, 2017, 12:00–12:15, N 25

Exploring Vibrational Dynamics of Anabaena Sensory Rhodopsin by Pump Impulsive Vibrational Spectroscopy — •Partha Pratim Roy¹, Yoshitaka Kato², Hideki Kandori², and Tiago Buckup¹ — ¹Physikalisch Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Germany — ²Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Japan

Anabaena Sensory Rhodopsin is a microbial retinal protein (MRP), which converts the photon energy to chemical energy by a cis-trans isomerization. Like other MRPs, it shows fast isomerization kinetics (<200fs) but surprisingly low quantum yield. Until now, it is not very clear which specific vibrational mode in excited potential energy surface (PES) drives such a fast isomerization kinetics. In this work, pump-impulsive vibrational spectroscopy with time resolution <20fs is utilized to capture the vibrational dynamics in ground and excited state and disentangle them. Excitation pulse (sub-13 fs), resonant with the ground-state absorption of the chromophore, is used for this experiment. The push and probe pulse (15 fs) were made resonant to absorption of K-product of the isomer. This study captures the vibrational signature in low frequency up to 2000 cm⁻¹. Strong ground state vibrational mode around 812, 1008 and 1539 cm⁻¹ was observed, which matches the spontaneous Raman spectrum of the molecule. Appearance of new vibrational modes around 900 and 1800 cm⁻¹ at certain push delay confirms their activity only in specific region of the excited state PES. This clearly shows the change of vibrational features from the FC-region to photoproduct region through the conical intersection.