Counterion-controlled spectral tuning of the protonated Schiff-base retinal

Yoni Toker, Jeppe Langeland, Elisabeth Gruber, Christina Kjær, Steen Brøndsted Nielsen, Lars H. Andersen, Veniamin A. Borin, and Igor Schapiro
Phys. Rev. A 98, 043428 – Published 23 October 2018

Abstract

Color vision is based on the ability of different opsin proteins to tune the absorption band of their chromophore, the retinal protonated Schiff base (RPSB). Two main mechanisms proposed for this tunability are geometric and electrostatic. Here we probe the latter effect experimentally and by a quantum chemical calculation of the absorption by an isolated complex containing the retinal chromophore and molecules with a strong dipole moment. Betaine complexation causes an anomalously large blue shift. The shift provides direct evidence that the strong charge-transfer character of the electronic transition is the cause of the opsin shift, and shows that the electric field of the counterion is responsible for the color tuning, which allows absorption of light in the blue region of the visible spectrum by opsin proteins.

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  • Received 17 June 2018

DOI:https://doi.org/10.1103/PhysRevA.98.043428

©2018 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalPhysics of Living Systems

Authors & Affiliations

Yoni Toker

  • Department of Physics and Institute for Nanotechnology and Advanced Materials, Bar Ilan University, Ramat Gan 529002, Israel

Jeppe Langeland, Elisabeth Gruber, Christina Kjær, Steen Brøndsted Nielsen, and Lars H. Andersen

  • Department of Physics and Astronomy, Aarhus University, Aarhus 8000, Denmark

Veniamin A. Borin and Igor Schapiro

  • Fritz Haber Center for Molecular Dynamics Research, Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem 9190401, Israel

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Issue

Vol. 98, Iss. 4 — October 2018

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