Sonics VC750 (Serial No. "Y through "AB")" - Manual (Page 28)

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Before each application, place the tip in 100% ethanol and energize the power supply
for a few seconds to remove any residual substances. If still concerned about
contamination from previous use, clean the probe with a disinfectant such as 20%
Virkon solution and rinse with distilled water. Probes are autoclavable.
To inhibit sample loss in test tube due to sticking, siliconize the test tube as follows:
Wash and dry the test tube thoroughly, coat with silicone, then air dry. “Sigmacote”
manufactured by Sigma Chemical Co., 3050 Spruce Street, St. Louis, Missouri 63103,
USA, phone (314) 771-5765, is ideally suited for that purpose.
High viscosity and concentration are problematic. 2,000 cps and 15% concentration
by weight are maximum limits. Ultrasonic processing propagates sound waves
through the sample. If the sample is so dense that it will not pour or circulate easily it
will absorb the sound waves, and be too thick for ultrasonic processing.
Use the Cup Horn for processing pathogenic, radioactive, and biohazardous materials
in complete isolation without probe intrusion. Because plastic tubes have a tendency
to absorb vibrations, it is preferable to contain the sample in a stainless steel tubes or
glass tubes when working with a cup horn. To expedite processing, add glass beads
to the sample. If desired, crushed ice can also be added to the water inside the cup
horn, in order to optimize cooling. Processing samples in a Cup Horn will usually take
4 times longer than processing with direct probe intrusion.
Various methods can be implemented to measure the efficiency of ultrasonic
disruption. Typically, counting the cells using a microscope is a satisfactory method.
However, for greater accuracy, a protein assay should be used. This procedure is
widely recognized as a good method for measuring cell disruption by taking into
account the amount of protein released after disruption. The disrupted cells are then
tested and checked against this number for percentage breakage.
There are several types of protein assays. The most common is the Folin Reaction
(Lowry Assay) method, as it is comparatively simple and provides consistent results.
This colorimetric method has a sensitivity to protein of around 8 µg / mL in the assay
solution.
The assay turns blue in the presence of proteins due to the reaction of copper ions in
the alkaline solution with protein and the reduction of phosphomolybdate-
phosphotungstic acid in the Folin reagent by aromatic amino acids in the treated
protein.