ChR2(C128T.H134R) is a light-gated cation channel that can be used as an optogenetic tool to activate neurons. It is an engineered derivative of ChR2, containing the C128T and H134R amino acid substitutions relative to ChR2 (FBrf0222569); C128T has been shown to extend the lifetime of the open state (PMID:19079251) and H134R has been shown to increase photocurrent size (PMID:16360690). 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 FBrf0222569.