Quantitation of plasmid DNA in aqueous two-phase systems by fluorescence analysis

The development of aqueous two-phase systems for plasmid purification from Escherichia coli cell lysates requires a reliable DNA quantitation method. Plasmid DNA was quantified by fluorescence using PicoGreen nucleic acid stain. Linearity was obtained up to 40 ng plasmid ml^sup -1^. Two polyethyleneglycol (PEG)/salt systems were studied, PEG 600/K^sub 2^HPO^sub 4^ and PEG 300/K^sub 2^HPO^sub 4^. The average plasmid recovery was 41% in the bottom phase of the first system and 35% in the top phase of the second system. This method has proved to be simple and reproducible.[PUBLICATION ABSTRACT]