An Optimized Glutamate Receptor Photoswitch with Sensitized Azobenzene Isomerization

A new azobenzene-based photoswitch, <b>2</b>, has been designed to enable optical control of ionotropic glutamate receptors in neurons via sensitized two-photon excitation with NIR light. In order to develop an efficient and versatile synthetic route for this molecule, a modular strategy is described which relies on the use of a new linear fully protected glutamate derivative stable in basic media. The resulting compound undergoes one-photon <i>trans</i>–<i>cis</i> photoisomerization via two different mechanisms: direct excitation of its azoaromatic unit and irradiation of the pyrene sensitizer, a well-known two-photon sensitive chromophore. Moreover, <b>2</b> presents large thermal stability of its <i>cis</i> isomer, in contrast to other two-photon responsive switches relying on the intrinsic nonlinear optical properties of push–pull substituted azobenzenes. As a result, the molecular system developed herein is a very promising candidate for evoking large photoinduced biological responses during the multiphoton operation of neuronal glutamate receptors with NIR light, which require accumulation of the protein-bound <i>cis</i> state of the switch upon repeated illumination

Two-Photon Neuronal and Astrocytic Stimulation with Azobenzene-Based Photoswitches

Synthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation have never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution