Figure 1: Design and membrane localization of FRET-opsin sensor constructs in cultured neurons.
From: Imaging neural spiking in brain tissue using FRET-opsin protein voltage sensors
(a) Top, cartoon of the Mac-fluorescent protein fusion. Bottom, amino-acid sequences of the linker for the Mac-mOrange and Mac-mCitrine sensors. (b) Emission spectra of the donor mCitrine and mOrange fluorescent proteins and the absorption spectrum of MacQ, the FRET acceptor. (c) We expressed the enhanced Mac constructs as a protein fusion with mOrange2/mCitrine under the control of the Camk2a promoter and targeted the fusion protein to the cell membrane using the localization sequences TS and ER. (d) Fluorescence signals from neurons labelled with MacQ-mOrange2 and MacQ-mCitrine. The left images of each set are from the fluorescent protein’s colour channel; the right images are spatial maps of the fluorescence response to a voltage step depolarization of ~100 mV. Regions of fluorescence and voltage response are generally colocalized. Scale bar is 20 μm and applies to all four images.
