Patent ID: 7553658

Claim:
A method for the purification of plasmid DNA in an aqueous two-phase system, comprising: (a) providing a composition including a first polymer EO 50 PO 50 , a second polymer Dextran T 500 and, optionally, a salt; (b) contacting said composition with an aqueous solution comprising plasmid DNA and RNA to form a mixture which contains from about 4.5% (w/w) EO 50 PO 50 /4.5%(w/w) Dextran T 500, to about 2.5%(w/w)EO 50 PO 50 /9% (w/w) Dextran T 500; (c) providing a phase separation wherein plasmid DNA is partitioned to a top aqueous phase while RNA partitions predominantly to a lower phase, and subsequently isolating the top aqueous phase; (d) increasing the temperature of the isolated top aqueous phase to a temperature above the cloud point of the first polymer and below a temperature where plasmid DNA is degraded and subsequently isolating a top aqueous phase so formed; and, optionally, (e) performing a chromatography step to recover the plasmid DNA from the isolated top phase of step (d).