AnHPLC analysis showed that clarified lysates obtained from GALG20cells had the highest percentage of pDNA (41% vs 31% and 26%for MG1655endArecA and DH5, respectively).
The distribu-tion of plasmid topoisomers and the presence of impurities likeRNA, gDNA, and residual proteins in the final pDNA were alsoinvestigated (Table 2 and Fig. 3). An agarose gel electrophoresisanalysis with ethidium bromide staining showed that RNA impu-rities were absent and that supercoiled isoforms predominate inthe three pDNA preparations (Fig. 3). The levels of protein con-tamination were residual and independent of the starting cells.Although low amounts of gDNA were detected in samples iso-lated from GALG20 and MG1655endArecA cells, gDNA contentin pDNA preparations derived from DH5 was higher than the rec-ommended value (