roGFP2 is a reduction-oxidation-sensitive fluorescent protein, showing rapid and reversible changes in fluorescence in response to changes in redox potential. The protein has two excitation peaks (at approximately 400nm and 490nm), with the relative amplitude of the peaks depending on the solution oxidation potential: oxidation increases the 400nm excitation peak, while decreasing the 490nm peak. The fluorescence emission of roGFP2 is also affected by pH. roGFP2 is an artificial derivative of the naturally occurring fluorescent protein encoded by the Aequorea victoria GFP gene (UniProtKB:P42212) and contains the mutations S147C, Q204C and S65T, plus the phenotypically neutral mutations C48S and Q80R (PMID:14722062).