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., Nielsen, Steen Brøndsted and Bull, James N. (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
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Depositing User: LivePure Connector
Date Deposited: 27 Jan 2022 11:30
Last Modified: 09 Jun 2022 14:43
DOI: 10.1021/acs.jpca.1c10628

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