Figure 3

Properties of the cell populations stably transfected by p1.2-based plasmids under various drug selection stringencies. DG44: untransfected CHO DG44 cells; p1.1: cells stably transfected by the p1.1eGFP plasmid and selected in the presence of 200 nM MTX; p1.1(EBVTR-): transfection by the p1.1(EBVTR-)eGFP plasmid using the same conditions. A. Level of intracellular eGFP in cell populations. Error bars indicate the standard deviation, n = 2. B. Proportion of eGFP-negative cell populations measured by FACS. C. Number of copies of genome-integrated plasmids measured by Q-PCR. Amplicons are located inside the eGFP ORF and one representative value experiment from three independent measurements is shown. Error bars represents standard deviations, n = 3-4. The apparent level of the eGFP ORF DNA for the untransfected CHO DG44 cells is below 0.1 copies per one haploid genome. D. Codes for the different cell populations and the concentrations of antibiotics employed.