Alkylated green fluorescent protein chromophores: Dynamics in the gas phase and in aqueous solution

Ashworth, Eleanor K., Kao, Min-Hsien, Anstöter, Cate Sara, Riesco-llach, Gerard, Blancafort, Lluís, Solntsev, Kyril M., Meech, Stephen R. ORCID:, Verlet, Jan R. R. and Bull, James N. ORCID: (2023) Alkylated green fluorescent protein chromophores: Dynamics in the gas phase and in aqueous solution. Physical Chemistry Chemical Physics, 25 (35). pp. 23626-23636. ISSN 1463-9076

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Fluorescent labelling of macromolecular samples, including using the green fluorescent protein (GFP), has revolutionised the field of bioimaging. The ongoing development of fluorescent proteins require a detailed understanding of the photophysics of the biochromophore, and how chemical derivatisation influences the excited state dynamics. Here, we investigate the photophysical properties associated with the S1 state of three alkylated derivatives of the chromophore in GFP, in the gas phase using time-resolved photoelectron imaging, and in water using femtosecond fluorescence upconversion. The gas-phase lifetimes (1.6–10 ps), which are associated with the intrinsic (environment independent) dynamics, are substantially longer than the lifetimes in water (0.06–3 ps), attributed to stabilisation of both twisted intermediate structures and conical intersection seams in the condensed phase. In the gas phase, alkylation on the 3 and 5 positions of the phenyl ring slows the dynamics due to inertial effects, while a 'pre-twist' of the methine bridge through alkylation on the 2 and 6 positions significantly shortens the excited state lifetimes. Formation of a minor, long-lived (>>40 ps) excited state population in the gas phase is attributed to intersystem crossing to a triplet state, accessed because of a T1/S1 degeneracy in the so-called P-trap potential energy minimum associated with torsion of the single-bond in the bridging unit connecting to the phenoxide ring. A small amount of intersystem crossing is supported through TD-DFT molecular dynamics trajectories and MS-CASPT2 calculations. No such intersystem crossing occurs in water at T = 300 K or in ethanol at T ≈ 77 K, due to a significantly altered potential energy surface and P-trap geometry.

Item Type: Article
Additional Information: Acknowledgements: Funding was provided by a start-up grant at University of East Anglia and an EPSRC New Investigator Award (EP/W018691) to JNB. LB and GRL thank the Ministerio de Ciencia, Innovación y Universidades (Spain) for project PID-2019-104654GB-I00 and the Red Española de Supercomputación for computational time (project QSB-2018-1-0040). EKA acknowledges a University of East Anglia Doctoral Studentship. Electronic structure calculations were carried out on the High Performance Computing Cluster supported by the Research and Specialist Computing Support service at the University of East Anglia.
Uncontrolled Keywords: physics and astronomy(all),physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/3100
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
Faculty of Science > Research Groups > Chemistry of Light and Energy
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Depositing User: LivePure Connector
Date Deposited: 22 Aug 2023 08:30
Last Modified: 24 Oct 2023 01:40
DOI: 10.1039/D3CP03250G


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