G-geNOps are green fluorescent probe for single cell NO• measurements
G-geNOps are a class of green fluorescent genetically encoded sensor capable for specific detection of intracellular nitric oxide (NO•) dynamics either within the cytosol (G-geNOp) or mitochondria (mtG-geNOp). These constructs have been developed on the basis of green fluorescent protein (GFP) that is conjugated with a NO•-binding domain of the Escherichia coli protein NorR. Upon NO• binding to functional G-geNOps the green fluorescence intensity is immediately quenched. The NO•-dependent quenching effect correlates with the cellular NO• concentration. Fluorescence of G-geNOps rapidly and fully recovers in the absence of NO•. Hence, G-geNOps provide a highly specific real-time read-out of local NO• dynamics on the level of individual cells or organelles (mitochondria). The excitation and emission maxima of G-geNOps are at 480 nm and 535 nm, respectively. Standard optical filters optimized for imaging of GFP should be used. ΔG-geNOps are NO insensitive constructs that should be used as respective controls.