ChrimsonR is a light-gated cation channel that can be used as an optogenetic tool to activate neurons; it is optimally excited by light of approximately 590nm wavelength. It is an artificial channelrhodopsin derived by introducing the K176R mutation into Chrimson; this results in faster off-kinetics without altering the action spectrum. The formation of a functional channel requires the presence of a covalently linked all-trans-retinal chromophore which can be provided exogenously if necessary via the culture medium or diet (this cofactor is present endogenously in some intact vertebrate systems). For detailed kinetic and spectral properties, see FBrf0224260.