Visible-Light Sensitized Isomerization in the Lipid Bilayer Enables Activation of a Transmembrane Transporter

Currently, there is major interest in embedding light-responsive (supra)molecular systems in phospholipid bilayer membranes, for example, to control transmembrane transport processes. Most of these systems are operated by harmful UV-light. Although in solution phase the isomerization of photoswitchable systems has been achieved using visible-light-absorbing photosensitizers, no cases are known yet of sensitized isomerization in a lipid bilayer environment. Herein, we show that the active isomer of a stiff-stilbene based chloride transporter can be generated in situ by irradiation and energy transfer from a ruthenium tris(bipyridyl) complex. In the bilayer, this process is more efficient than in solution, as a benefit of the higher effective concentration of sensitizer and transporter upon confinement. Our work offers an approach to induce isomerization of membrane-embedded systems by visible light, without the need of synthetic modification and loss of function or activity.