AcGFP1 is a monomeric green fluorescent protein with an excitation peak of 475nm and an emission peak of 505nm in vitro. It is an artificial derivative of the Aequorea coerulescens acGFPL gene (GenBank:AY151052), a non-fluorescent GFP homolog. AcGFP1 contains the mutations V11I, F64L, K101E, T206A and E222G relative to the wild-type acGFPL gene (the latter mutation being the key mutation that creates the fluorescent form) and the open-reading frame has been optimized for mammalian codon usage (PMID:12693991).