RCaMP1f is a genetically encoded fluorescent Ca[2+] indicator. It is a fusion protein composed of an RSET-nickel affinity tag (which lacks 2 His residues), the M13 peptide, a circularly permuted red fluorescent protein and calmodulin. The circularly permuted fluorescent protein is based on mRuby; the circular permutation site is between residues 158 and 159. A number of amino acid substitutions have been introduced relative to the 'RCaMP-AI' parent variant: L59A, E60I, G109A, A112Y, A270V, T364I, D372Y, R384G, I424S (note that the numbering does not take into account the deletion of 2 His residues in the RSET tag relative to 'RCaMP-AI') (FBrf0221174). For detailed kinetic and spectral properties and a comparison of RCaMP1f with other red fluorescent Ca[2+] indicators, see FBrf0221174.