A new twist in the photophysics of the GFP chromophore: A volume-conserving molecular torsion couple

Conyard, Jamie, Heisler, Ismael A., Chan, Yohan, Bulman Page, Philip, Meech, Stephen R. ORCID: https://orcid.org/0000-0001-5561-2782 and Blancafort, Lluis (2018) A new twist in the photophysics of the GFP chromophore: A volume-conserving molecular torsion couple. Chemical Science, 9 (7). pp. 1803-1812. ISSN 2041-6520

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The simple structure of the chromophore of the green fluorescent protein (GFP), a phenol and an imidazolone ring linked by a methyne bridge, supports an exceptionally diverse range of excited state phenomena. Here we describe experimentally and theoretically the photochemistry of a novel sterically crowded nonplanar derivative of the GFP chromophore. It undergoes an excited state isomerization reaction accompanied by an exceptionally fast (sub 100 fs) excited state decay. The decay dynamics are essentially independent of solvent polarity and viscosity. Excited state structural dynamics are probed by high level quantum chemical calculations revealing that the fast decay is due to a conical intersection characterized by a twist of the rings and pyramidalization of the methyne bridge carbon. The intersection can be accessed without a barrier from the pre-twisted Franck-Condon structure, and the lack of viscosity dependence is due to the fact that the rings twist in the same direction, giving rise to a volume-conserving decay coordinate. Moreover, the rotation of the phenyl, methyl and imidazolone groups are coupled in the sterically crowded structure, with the methyl group translating the rotation of one ring to the next. As a consequence, the excited state dynamics can be viewed as a torsional couple, where the absorbed photon energy leads to conversion of the out-of-plane orientation from one ring to the other in a volume conserving fashion. A similar modification of the range of methyne dyes may provide a new family of devices for molecular machines, specifically torsional couples.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Materials and Catalysis
Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
Depositing User: Pure Connector
Date Deposited: 03 Jan 2018 07:33
Last Modified: 25 Aug 2023 00:11
URI: https://ueaeprints.uea.ac.uk/id/eprint/65832
DOI: 10.1039/C7SC04091A

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