The team of Karl Deisseroth conducted a series of experiments under matched conditions in order to draw a systematic comparison of several microbial opsins. Experiments aimed at comparing action spectra, peak photocurrents, steady-state/peak ratios, time-to-peak, off kinetics, desensitization kinetics, kinetics of recovery from desensitization in darkness and 50% effective light power density. The report is published in an upcoming issue of Nature Methods.
- 11 ChR variants were tested: ChR2, ChR2(H134R), ChR2(E123A), ChR2(T159C), ChR2(E123T/T159C), ChR2(L132C), ChIEF, channelrhodopsin-fast receiver, channelrhodopsin-green receiver, C1V1(E162T) and C1V1(E122T/E162T).
- 4 ultrafast control tools were compared: ChR2(E123A), ChR2(E123A/H134R), ChR2(E123T) and ChR2(E123T/H134R).
- 7 light-driven pumps were compared: eNpHR3.0, Arch1.0, eArch3.0, ArchT1.0, eArchT3.0, Mac1.0 and eMac3.0.
- all opsin genes were packaged identically in a lentiviral backbone under the control of the mouse excitatory neuron–specific CaMKIIα promoter.
- all opsin coding sequences were fused in frame with the gene encoding enhanced YFP (eYFP).
- electrophysiological measurements were performed on transfected cultured hippocampal pyramidal neurons with matched light power densities across experiments (5 mW/mm2).