yellow fluorescent protein tag venus fluorescent protein tag PSI-MI Introduction of a point mutation into Aequorea-derived YFP, the substitution of leucine for phenylalanine at position 46 (F46L), produced Venus. This mutation dramatically accelerates oxidation of the chromophore, the rate-limiting step in fluorescent protein maturation. Additional mutations were also introduced in order to increase the tolerance of Venus to acidic environments and to reduce the sensitivity to chloride. The absorption and emission spectral peaks are 515 and 528 nanometers, respectively. orchard venus 2012-01-03T03:05:01Z MI:1135