FIGURE 4.

Molecular structures of selected small molecule-based Zn²⁺ indicators and schematic representations of selected GEZIs. Many small molecule-based Zn²⁺ indicators are structurally similar to small molecule-based Ca²⁺ indicators. (A) FuraZin, (B) IndoZin, and (C) FluoZin-3 have fluorophore moieties that are identical to those of fura-2 and indo-1, and fluo-4, respectively, (Gee et al., 2002). (D) ZP1 is composed of a di-2-picolylamine (DPA) Zn²⁺ chelator and a green-fluorescent fluorescein moiety (Walkup et al., 2000). (E) RhodZin-3 is a rhodamine-based red fluorescent Zn²⁺ indicator (Gee et al., 2002). (F) CALWY (Vinkenborg et al., 2009) is a FRET-based GEZI with the Zn²⁺ binding moiety of ATOX1/WD4. (G) ZIBG1 (Chen et al., 2019) is based on the Zn²⁺ binding ZAP1 protein and ncpEGFP. (H) ZIBG2 (Chen et al., 2019) is based on Zinc hook and cpEGFP.