Anabaena Sensory Rhodopsin: Effect of point mutations on PSBR photo-isomerization speed Damianos Agathangelou 1 , Yoelvis Orozco-Gonzalez 1 , Marí del Carmen Marin Pérez 2 , Johanna Brazard 1 , Hideki Kandori 3 , Kwan-Hwang Jung 4 , Jérémie Léonard 1 , Nicolas Ferré 5 , Massimo Olivucci 2,6 , and S.Haacke 1,* 1 Université de Strasbourg - CNRS UMR 7504, Institut de Physique et Chimie des Matériaux de Strasbourg, Strasbourg 67034, France 2 Department of Biotechnology, Chemistry & Pharmacy, Università di Siena,2, I-53100 Siena, Italy 3 Department of Frontiers Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan 4 Department of Life Science and Institute of Biological Interfaces, Sogang University, South Korea 5 Aix-Marseille Université, CNRS, ICR, 13284 Marseille, France 6 Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States Abstract. We report new experimental results on the ultrafast photo- isomerization of ASR - PSBR where, unlike other retinal proteins, point mutations lead to a 2-fold increase of the photo-isomerization speed for the all-trans isomer. Prominent low-frequency vibrational coherences are reported for both the excited and photo-product ground states. 1 Introduction Anabaena sensory rhodopsin (ASR) is a microbial retinal protein for which the protonated Schiff base of retinal (PSBR) adopts two different conformations in the ground state, the all-trans,15-anti (AT) and 13-cis, 15-syn (13C). Related to the biological function of ASR being a light-intensity sensor, the isomer ratio depends upon illumination conditions (intensity and wavelength) reaching a photostationary, so- called light adapted (LA) state. Interestingly, upon incubation in the dark at room temperature, the AT population exceeds 97%, defining the so-called dark-adapted (DA) state. AT and 13C undergo two distinct photo-cycles interconverting on a millisecond time scale [1]. The interest of studying the primary steps of retinal proteins’ photo-cycle via femtosecond spectroscopy originates from a long-standing question, on how the protein environment tunes and optimizes the photoisomerization reaction speed and yield. In this context, ASR is a particularly suitable model system, since it allows to study the photoreaction of both conformers in the same protein environment at the same time. In particular, the excited state lifetime (ESL) is representative of the * Corresponding author : haacke@unistra.fr , E Web of Conferences https://doi.org/10.1051/e onf /201920 PJ pjc 9) 205 5 UP 2018 201 10004 ( 10004 © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).