C-geNOp a cyan fluorescent probe for single cell NO• measurements
C-geNOp is a cyan fluorescent genetically encoded sensor capable for specific detection of intracellular nitric oxide (NO•) dynamics. It has been developed on the basis of cyan fluorescent protein (CFP) that is conjugated with a NO•-binding domain of the Escherichia coli protein NorR. Upon NO• binding to C-geNOp the cyan fluorescence intensity is immediately quenched. The NO•-dependent quenching effect correlates with the cellular NO• concentration. Fluorescence of C-geNOp rapidly and fully recovers in the absence of NO•. Hence, C-geNOp provides a highly specific real-time read-out of cytosolic NO• dynamics. The excitation and emission maxima of C-geNOp are at 430 nm and 480 nm, respectively. Standard optical filters optimized for imaging of CFP should be used.