Comparison of fluorescence spectra of cells expressing the FL-IFN-γR2/EBFP and FL-IFN-γR2/GFP chains in the presence and absence of the IFN-γR1 chain and in the presence and absence of ligand. Comparison of fluorescence spectra of cells expressing the FL-IFN-γR2/EBFP and FL-IFN-γR2/GFP chains in the presence and absence of the IFN-γR1 chain and in the presence and absence of ligand. COS-1 cells were transfected with FL-IFN-γR2/EBFP and FL-IFN-γR2/GFP without transfection with IFN-γR1 (left panels). COS-1 cells were also transfected with IFN-γR2/EBFP and IFN-γR2/GFP together with the IFN-γR1 chain (right panels). The spectra of the COS-1 cells transfected with the FL-IFN-γR2/EBFP and FL-IFN-γR2/GFP in the presence and absence of IFN-γ and in the presence and absence of the IFN-γR1 chain are shown in the panels. In all experiments with FRET, measurements were taken at 15 min after addition of IFN-γ when noted. All laser excitation experiments were performed with single cells, although multiple cells were sampled and provided similar results. The fluorescence emission spectra in response to two-photon excitation at 760 nm are shown. Christopher D. Krause et al. Mol Cell Proteomics 2002;1:805-815 © 2002 The American Society for Biochemistry and Molecular Biology