Monthly Archives: January 2012

A systematic comparison of microbial opsins

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.

Tools compared:

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.

Experimental conditions:

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).

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