Targeted expression in HEK293 cells A: Schematic representation of the constructs used for targeting. CR is the signal peptide of calreticulin, KDEL is the ER retention motive. B: Fluorescence emission spectrum of dissociated HEK293 cells transfected for 2 days either with ER-Sapphire or ER-T-Sapphire. Excitation was at 399 nm. C: Individual 293 cell co-expressing ER-T-Sapphire and Yellow Cameleon 3ER. Excitation was either at 400 nm to specifically excite T-Sapphire or 488 to excite the YFP component of YC3ER. Note the identical fluorescence pattern. For comparison, T-Sapphire expressed in the cytosol fills the whole cell including the nucleus (bottom). The emission filter was 535/25. Scale bar 10 μM.