Complexation of green and red Kaede fluorescent protein chromophores by a zwitterion to probe electrostatic and induction field effects

Ashworth, Eleanor K., Stockett, Mark H., Kjaer, Christina, Bulman Page, Philip C., Meech, Stephen R. ORCID:, Nielsen, Steen Brøndsted and Bull, James N. ORCID: (2022) Complexation of green and red Kaede fluorescent protein chromophores by a zwitterion to probe electrostatic and induction field effects. The Journal of Physical Chemistry A, 126 (7). 1158–1167. ISSN 1089-5639

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The photophysics of green fluorescent protein (GFP) and red Kaede fluorescent protein (rKFP) are defined by the intrinsic properties of the light-absorbing chromophore and its interaction with the protein binding pocket. This work deploys photodissociation action spectroscopy to probe the absorption profiles for a series of synthetic GFP and rKFP chromophores as the bare anions and as complexes with the betaine zwitterion, which is assumed as a model for dipole microsolvation. Electronic structure calculations and energy decomposition analysis using Symmetry-Adapted Perturbation Theory are used to characterize gas-phase structures and complex cohesion forces. The calculations reveal a preponderance for coordination of betaine to the phenoxide deprotonation site predominantly through electrostatic forces. Calculations using the STEOM-DLPNO-CCSD method are able to reproduce absolute and relative vertical excitation energies for the bare anions and anion–betaine complexes. On the other hand, treatment of the betaine molecule with a point-charge model, in which the charges are computed from some common electron density population analysis schemes, show that just electrostatic and point-charge induction interactions are unable to account for the betaine-induced spectral shift. The present methodology could be applied to investigate cluster forces and optical properties in other gas-phase ion–zwitterion complexes.

Item Type: Article
Additional Information: Funding was provided by the Swedish Foundation for International Cooperation in Research and Higher Education (STINT, grant number PT2017-7328 to M.H.S. and J.N.B.), a start-up grant at University of East Anglia (to J.N.B.), the Olle Engkvist Foundation (Grant No. 200-575 to M.H.S.), the Swedish Research Council (2016-03675 to M.H.S.), the Independent Research Fund Denmark | Natural Sciences (9040-00041B to S.B.N.), and the NOVO Nordisk Foundation (NNF20OC0064958 to S.B.N.). S.R.M. and P.C.B.P. acknowledge funding from the EPSRC (EP/H025715/1). This work is supported by COST Action CA18212 – Molecular Dynamics in the GAS phase (MD-GAS). 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: physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/1600/1606
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
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Depositing User: LivePure Connector
Date Deposited: 27 Jan 2022 11:30
Last Modified: 09 Feb 2023 13:50
DOI: 10.1021/acs.jpca.1c10628


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