Excitation-emission spectra for mutants with altered fluorescent color. In some cases spectra for the wild type proteins are shown for comparison. Within each pair of lines the emission spectrum is the one at longer wavelengths. (A) Spectra for amFP486 wild type (dotted lines) and its blue shifted mutant Y66W (solid lines). (B) Spectra for mutants amFP486-A167M (solid lines) and zFP506-M167A (gray thick lines). (C) Spectra for green mutant zFP538-K65M (solid lines) and zFP506 wild type (gray thick lines). (D) Spectra for dual-color mutant zFP538-D68N. (E) Spectra for yellow mutant zFP506-A63G/N65K/N68D (solid lines) and zFP538 wild type (gray thick lines). (F) Spectral characteristics of the dual-color mutant protein dsFP483-N68S/I112S. Dotted line - double-peak fluorescence (excitation at 280 nm). Solid line - red fluorescence (excitation at 540 nm). Dashed line - excitation spectrum for red emission (at 620 nm).