Small-scale purification of bacteriophage λ DNA by an airfuge centrifugation step in cesium chloride gradients

A rapid and efficient procedure for purifying bacteriophage λ DNA is described. This small-scale purification involves isolation of bacteriophage particles on cesium chloride gradients. Using an Airfuge ultracentrifuge, the centrifugation step can be readily achieved in 90 minutes. The method allows a 1-day purification of up to 12 independent λ DNA (20–40 μg each). The recovered DNA, essentially devoid of RNA and DNA contaminants, is efficiently cut by restriction endonucleases and can serve as starting material for the ligation of DNA fragments in other cloning vehicles.