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Radical-Triggered Reaction Mechanism of the Green-to-Red Photoconversion of EosFP

Fare, C; Yuan, L; Cordon-Preciado, V; Michels, JJ; Bearpark, MJ; Rich, P; van Thor, JJ; (2020) Radical-Triggered Reaction Mechanism of the Green-to-Red Photoconversion of EosFP. The Journal of Physical Chemistry B , 124 (36) pp. 7765-7778. 10.1021/acs.jpcb.0c04587. Green open access

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Abstract

Reaction intermediates in the green-to-red photoconversion of the photochromic fluorescent protein EosFP have been observed using high-intensity continuous blue illumination. An intermediate was identified through light-induced accumulation that continues to convert the green form in subsequent darkness, putatively containing a tyrosyl radical, albeit with anomalously shifted features in both the electronic and FTIR spectra. Lowering the pH to 5.5 significantly delays the decay of this tyrosyl intermediate, which is accompanied by Stark-shifted features in the electronic spectra of reactants and products. Vibrational mode assignments for the high-frequency and fingerprint FTIR spectral regions of the reaction intermediates support a proposed sequence of events where the newly formed C_{alfa}=C_{beta} ethylenic bond precedes modifications on the His-62 imidazole ring and confirms a C═O(NH_{2}) product group on Phe-61. We propose a reaction mechanism that involves tyrosyl generation via singlet excited-state-mediated oxidation which subsequently triggers the covalent reactions by oxidation of the green chromophore.

Type: Article
Title: Radical-Triggered Reaction Mechanism of the Green-to-Red Photoconversion of EosFP
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.jpcb.0c04587
Publisher version: https://doi.org/10.1021/acs.jpcb.0c04587
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.
Keywords: Reaction mechanisms, Absorption, Fourier transform infrared spectroscopy, Chromophores,Chemical reactions
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Structural and Molecular Biology
URI: https://discovery.ucl.ac.uk/id/eprint/10110768
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