From color-tuning to optogenetics: relationship between red-light absorption and fluorescence intensity in an archaerhodopsin model.

From color-tuning to optogenetics: relationship between red-light absorption and fluorescence intensity in an archaerhodopsin model.

From color-tuning to optogenetics: relationship between red-light absorption and fluorescence intensity in an archaerhodopsin model. (#47)

Massimo Olivucci ¹

University of Siena and Bowling Green State University, Siena, ITALY, Italy

Recent computational studies have revealed the critical impact of the electronic structure of the excited state species generated during the light-induced double bond isomerization of the chromophore of rhodopsin pigments. While a charge transfer structure dominates the function of visual rhodopsins (1), a diradical structure appears to control the fluorescence emission in NeoRhodopsin (3,4) and in a set of archaearhodopsin optogenetic reporters (2). By using a novel and unconventional type of quantum chemical modeling, we show that the stability of such a diradical must be inversely proportional to the absorption wavelength and that, most importantly, both properties can be regulated by the position and “delocalization” of the counter-ion of the protonated retinal chromophore.

(1) X. Yang et al., Nat. Chem. 2022, 14, 441-449.
(2) L. Barneschi et al., Nat. Comm. 2022, 13, 6432.
(3) R. Palombo et al., Nat. Comm. 2022, 13, 6652.
(4) Broser, M. et al. J. Phys. Chem. Lett. 2023, 14, 9291.

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Authors contributing to this presentation.

Olivucci, M

Massimo Olivucci is professor of Organic Chemistry at the University of Siena, Italy and Research Professor of Computational Chemistry at the Centre for Photochemical Sciences, Bowling Green State University, USA. Massimo took his PhD at the Università di Bologna (Italy) with Fernando Bernardi and carried out Postdoctoral research work at King’s College London (UK) with Michael A. Robb before accepting his first academic position in Bologna in 1991. He has authored over 290 research papers focusing on the investigation of organic and bio-organic reactivity using theoretical and computational methods. The most recent results are related to the investigation of light energy conversion in biological photoreceptors and the design of light-driven biomimetic molecular switches and motors. The programming and implementation of automated computational methods are also part of his work. Massimo Olivucci has contributed to establish the expanding fields of computational photochemistry and photobiology. Early results helped to establish that the “transition states” driving photochemical reactions are structures called “conical intersections”. This discovery created a new branch of theoretical photochemistry and changed the way in which these processes can be understood and designed. It also contributed to rationalize the observations made in the field of transient spectroscopy that many photochemical reactions occur on ultrafast timescale. In the first decade of 2000, his research group shifted to photobiology and applied the new ideas of theoretical photochemistry to biomolecules. The central role played by conical intersections in determining the function of different biological chromophores and of the corresponding photoreceptors was demonstrated. These results included the description of the sub-picosecond photoisomerization of the mammal visual pigment rhodopsin at the nuclear and electronic levels. Main honors: 2010 Gold Medal "Angelo Mangini" from the Italian Chemical Society, 2015 fellow of the Institute for Advanced Studies of the Université de Strasbourg, France, 2021 Doctoris Honoris Causa by the Université Aix-Marseille, France.

From color-tuning to optogenetics: relationship between red-light absorption and fluorescence intensity in an archaerhodopsin model. (#47)

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