Isoelectric Information and Courses from MediaLab, Inc.

The heat and acetic acid test is another semiquantitative test used to confirm the presence of protein in urine. It is more sensitive than the SSA test because the pH of the sample is brought close to the isoelectric point of proteins. However, this test is sometimes considered too sensitive because it can detect trace amounts of protein which are considered normal. The heat and acetic acid test gives false positive results with inorganic iodides, benzoin, tolutamide, and proteoses, similar to the SSA test. Bence-Jones protein consists of dimers of either kappa or lambda light chains from immunoglobulins. This abnormal protein is most often associated with multiple myeloma, but can also be found in cases of lymphoma, macroglobulinemia, leukemia, and other malignancies (Balant and Fabre, 1978). Testing for Bence-Jones protein is not part of the routine urinalysis. However, if Bence-Jones protein is suspected, the heat precipitation test or immunoelectrophoresis can be performed on a urine specimen. The heat precipitation test is based on the protein’s unusual solubility properties. Bence-Jones protein precipitates at temperatures between 40ºC and 60ºC (56ºC optimum), but dissolves again at 100ºC. Upon cooling, the precipitate will reappear around 60ºC and will dissolve again below 40ºC

There are numerous applications of electrophoresis. Routine protein electrophoresis performed in clinical laboratories is the oldest method and therefore the most frequently used method. With the advent of molecular diagnostics, several other electrophoresis methods have become very important, highly automated, and have several important applications.Types of electrophoresis that will be discussed are Routine electrophoresis High resolution electrophoresis Polyacrylamide gel electrophoresis Capillary electrophoresis Isoelectric focusing Immunochemical electrophoresis Two-dimensional electrophoresis Pulsed field electrophoresis

Isoelectric focusing is a type of separation where the solutes migrate based upon a different principle. The separation takes place on a gel where a pH gradient has been created using ampholytes. Ampholytes are a mixtures of amphoteric polyaminocarboxylic acids. This mixture possesses a range of pIs, a high buffering capacity at each pH, and is used to create pH gradients.When ampholytes undergo electropohoresis, each individual ampholyte migrates to its own region, an area that matches its pI. After migration of ampholytes, the gel has stable pH zones of increasing pH or a pH gradient. The solutes in the specimen do not migrate to the electrode of opposite charge but to the zone or area that matches their pI. IEF is performed on a gel in a capillary tube, strip, or plate. Gels used are most commonly polyacrylamide gels but agarose and cellulose acetate can also be used.