Fig 1. Schematic representation of the composition of the original libraries and suggested stages of the FGCaMP calcium indicator function.

(A) The designed original libraries for calcium indicators consisted of M13-like peptide or calcineurin from A. fumigatus or K. pastoris and CaM from A. niger or K. pastoris as a sensory part and cpEGFP as a fluorescent part, with randomized linkers located between sensory and fluorescent components. (B) Schematic representation of the FGCaMP indicator function. The cpEGFP component is shown as blue and cyan cylinders according to the excitation wavelengths; CaM and M13-like peptide are shown in light gray and speckled gray, respectively; Ca²⁺ ions are shown as red dots.