le  29 septembre 2022, à 11h

Michel SLIWA, LASIRE, Université de Lille

Lieu(x) :      Amphi Curie, Ecole Polytechnique

Contact :    Marten Vos
                    marten.vos at polytechnique.edu

The efficient use of light by living systems is a prerequisite for their existence. Among photo-active biological systems, photo-switchable proteins are key elements in different important biological functions for the vision, the protection or in the photosynthesis. They are also used in different applications such as opto-genetics and super-resolution bio-imaging. Their intrinsic properties of using in an efficient way the light is characterized by a photo-switching dynamics that takes place on several order time-scales, ranging from hundreds of femtoseconds to a few milliseconds. It involves several excited states and intermediates, and a complex interplay between the chomophore and 3D structural changes of the protein that guides efficiently the flow of energy to achieve reversibly the photo-modulation of different biological properties. However mechanistic details, in particular on the ultra-fast photochemical time scale, remain yet unclear. Another challenge in deducing the photo-switching mechanism is to create a uniform picture explaining both single pulse excitation experiments used in the study of ultrafast photo-dynamics, and continuous sun light irradiation experiments. I will report here on recent results on photo-switchable fluorescent proteins [1-3] and orange carotenoid protein [4-6], especially on how advanced time resolved techniques (time-resolved absorption spectroscopy and crystallography) and data analysis could reveal some crucial parameters in the photo-switching dynamics and rationally tailor the development of efficient new photo-active proteins for bio-imaging and optogenetics.

[1] L. M. Uriarte,* [...] M. Sliwa*, Structural Information about the trans -to- cis Isomerization Mechanism of the Photoswitchable Fluorescent Protein rsEGFP2 Revealed by Multiscale Infrared Transient Absorption, J. Phys. Chem. Lett., 2022, 13, 1194.
[2] J. Woodhouse, [...] M. Sliwa*, J.-P. Colletier, I. Schlichting* and M. Weik*, Photoswitching mechanism of a fluorescent protein revealed by time-resolved crystallography and transient absorption spectroscopy, Nat Commun, 2020, 11, 741.
[3] N. Coquelle, M. Sliwa, [...] J-P. Colletier,* I. Schlichting,*, M. Weik*, Chromophore twisting in the excited state of a photoswitchable fluorescent protein captured by time-resolved serial femtosecond crystallography, Nat. Chem., 2018, 10, 31.
[4] S. Niziński, […], G. Burdzinski* and M. Sliwa*, Is orange carotenoid protein photoactivation a single-photon process?, Biophys. Rep., 2022, 2, 100072.
[5] A. Wilson, [...] M. Sliwa*, D. Kirilovsky* and J.-P. Colletier*, Structure-function-dynamics relationships in the peculiar Planktothrix PCC7805 OCP1: impact of his-tagging and carotenoid type. Biochim Biophys Acta  Bioenerg 2022, 1863, 148584.
[6] S. Niziński, […], D. Kirilovsky*, G. Burdzinski* and M. Sliwa*, A unifying perspective of the ultrafast photo-dynamics of Orange Carotenoid Protein from Synechocystis : peril of high-power excitation, existence of different S* states and influence of tagging, JACS Au, 2022, 2, 1084.

A télécharger: Séminaire SLIWA