Bacteriorhodopsin: Tunable Optical Nonlinear Magnetic Response

TL;DR

This paper demonstrates a strong, tunable magnetic optical nonlinear response in Bacteriorhodopsin under femtosecond pulse excitation, with potential applications in optogenetics and neural circuit mapping.

Contribution

It reveals a novel, tunable magnetic nonlinear optical response in Bacteriorhodopsin, linking photochemistry with magnetic properties for biomedical applications.

Findings

BR exhibits a strong, tunable magnetic nonlinear response.

The response is detectable via polarization mapping of second harmonic signals.

Potential for integration with optogenetics and functional imaging.

Abstract

We report on a strong and tunable magnetic optical nonlinear response of Bacteriorhodopsin (BR) under "off resonance" femtosecond (fs) pulse excitation, by detecting the polarization map of the noncollinear second harmonic signal of an oriented BR film, as a function of the input beam power. BR is a light-driven proton pump with a unique photochemistry initiated by the all trans retinal chromophore embedded in the protein. An elegant application of this photonic molecular machine has been recently found in the new area of optogenetics, where genetic expression of BR in brain cells conferred a light responsivity to the cells enabling thus specific stimulation of neurons. The observed strong tunable magnetic nonlinear response of BR might trigger promising applications in the emerging area of pairing optogenetics and functional magnetic resonance imaging susceptible to provide an unprecedented complete functional mapping of neural circuits.