Variability of protein co-expression ratios at the single cell level for identical co-transfection conditions.

<p>(<i>A</i>) Wide-field images of cells co-transfected with a mixture of <i>pH2B-mPlum/Gag</i> and <i>pGag-mEos2</i> at an equimolar ratio show high variability in H2B-mPlum expression. (<i>B</i>) Measured Gag/Gag-mEos2 co-expression ratios as a function of the co-transfection ratio of plasmids. Each symbol corresponds to the co-expression ratio measured in a single cell. The black circles show the mean values. The linear fit of the mean co-expression level is plotted as a dashed line. The expression levels were extracted from the extrapolated FCS calibration curves shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115095#pone-0115095-g003" target="_blank">Fig. 3</a>. Scale bars correspond to 5 µm.