Figure 2: Effects of a low frequency (30W; 3W/cm2 from 36mm transducer) ultrasound treatment on plasmid DNA tertiary structures. Lane 1: control plasmid DNA, Lane 2-3: plasmid DNA was treated with the ultrasound treatment for 90 sec, and 30 min, Lane 4: plasmid DNA was treated with KpnI restriction enzyme.