Fig. 2. Basic principle of geNOps.

The geNOps are chimeric constructs, which consist of FP variants, e.g. GFP, directly fused with a highly selective non-heme iron(II) NO binding domain. When using the probes in cells, an iron(II)-loading procedure is required (upper panel) to receive full NO responsiveness of the probes. NO binds in a reversible manner to geNOps, thereby inducing a loss of fluorescence intensity, which is fully recovered in the absence of the radical (lower panel).