iAChSnFR is a genetically encoded fluorescent sensor designed for in vivo detection of acetylcholine. It is a fusion protein composed of an N-terminal IgG kappa secretion tag, the choline-binding protein encoded by the Thermoanaerobacter sp. X513 opuBC gene, with a circularly permuted form of sfGFP inserted after residue 106, a Tag:MYC tag and a C-terminal transmembrane domain from PDGFR. iAChSnFR also contains a number of amino acid substitutions that result in increased specificity and affinity for acetylcholine (https://www.biorxiv.org/content/10.1101/2020.02.07.939504v1).