The Process

• First, prepare the cell sample in its appropriate buffer or media, and cool this sample in a beaker of ice (or ice water for faster cooling). Wash the nozzle of the sonication machine with water, and wipe dry with a Kimwipe.
  Switch the Sonication/Cell Disruptor machine on, and adjust the Output Power to an appropriate wattage, depending on cell type and experiment. Insert the nozzle of the sonicator into your cell sample tube and turn on the machine; allow sonication to occur for five to 30 seconds at a time. (Allowing sonication for longer than 30 seconds drastically heats up the sample and can often cause denaturation.) While sonicating, gently move the sample tube around the nozzle to allow the nozzle access to different areas of the volume. It is generally best not to allow the tip of the nozzle to reach near the surface of the volume, as this can cause bubbling/foaming of your sample.
  After the first sonication, mix your sample by inverting several times, then sonicate again for an equal amount of time, all the while keeping the sample on ice.
  
  

Optimization Is Important

• It is generally best to optimize your sonication protocol for each different cell line used, as one must find an ideal balance between enough cells sheared and minimal denaturation/damaging of the sample. This can be done by sonicating for various time lengths and Output Power settings, then checking the cells under a microscope for fractionation.
  For example, one can start by doing three five-second bursts at 50 percent power, then increasing time and power if only a small part of the cell population appears fractionated under the microscope.
  
  

Specific Example

• For example, E. Coli cells used for growth and purification of a surface-receptor-binding protein (C-terminal fragment of Clostridium perfringens enterotoxin, or "C-CPE") may be sonicated in a volume of 7 to 10mL for two 30-second bursts at maximum Output Power. The cell suspension buffer is 1x PBS with 0.2mg/mL lysozyme.
  The sonication device used for this is a Microson Ultrasonic Cell Disruptor.