AzimiHashemi, N. et al. Nat. Commun. 5, 5810 (2014).

In Caenorhabditis elegans or Drosophila larvae, optogenetic manipulation with actuators such as channelrhodopsin 2 (ChR2) or ion pumps requires supplementing the animals' diet with the cofactor retinal. AzimiHashemi et al. took advantage of this requirement to supply synthetic retinal analogs that confer altered properties to optogenetic actuators. They tested eight different retinal analogs in C. elegans and observed a variety of effects on the actuators' action spectra as well as channel kinetics. For example, pairing ChR2 with dimethylamino-retinal (DMAR) results in slower channel kinetics and a broader action spectrum, making it possible to use light of longer-than-usual wavelength for optogenetic activation in C. elegans and Drosophila larvae. This makes the DMAR-ChR2 combination a more efficient optogenetic actuator in both model organisms than the retinal-ChR2 combination.