17-13 (CRX2027177; CRA030525)
A total of 3 ug DNA from each sample was mixed with cesium chloride (CsCl) solution to reach an initial buoyant density of 1.725 g mL-1 in gradient buffer (pH 8.0; 100 mM Tris-HCl, 100 mM KCl, 1.0 mM EDTA). The mixture was transferred to 5.1 mL ultracentrifuge tubes and centrifuged in a vertical rotor at 45000 rpm (190000 x g) for 44 h at 20 C. Following centrifugation, the tubes were removed vertically and fractionated into fifteen 340 uL DNA density fractions by displacing the gradient medium with sterile water using a programmable syringe pump.