After centrifugation at 7500g for 5 min the aqueous phase was collected in a new tube and subsequently extracted with 500 ml of TriseHCl (pH 8.0) satured phenolechloroform (1:1) and two times with chloroform. Finally, the aqueous phase was precipitated with a 1:1/10 volume of 3 M Sodium Acetate (pH 5.2) and a 1:1 volume of 100% isopropanol for 2 min at room temperature.