SuperClomeleon is a fluorescent reporter of changes in intracellular chloride concentration. Cl[-] binding to SuperClomeleon results in a conformational change that can be detected as a change in the efficacy of fluorescence resonance energy transfer (FRET) between two fluorescent protein variants; the FRET donor is Cerulean with a S30R mutation, and the FRET acceptor is a derivative of YFP (which has a Cl[-] binding site adjacent to its chromophore). SuperClomeleon can be used to detect intracellular Cl[-] changes produced by exogenous GABA or inhibitory synaptic activity (PMID:24107961).