HEK 293 cells transfected with CFP-SR-A and YFP-GRP78 were imaged with CFP (CFP filter lane), YFP (YFP filter lane), and FRET (FRET filter lane) channel at room temperature (I,J,K). FRETC was calculated as described in Methods and represented as a pseudo-color image (pseudo-color lane) (l). Cells transfected with YFP-CFP fusion plasmid were used as positive controls (A,B,C,D). The YFP/CFP plasmids-transfected cells were negative controls (E,F,G,H). A.l.u.f.i., arbitrary linear units of fluorescence intensity. Bar, 10 μm.