Electrophoresis is an analytic procedure for separating molecules both by size and electrical charge. It is regularly applied in medical diagnostics and other biological fields to determine the constituent molecules within biological samples. Its uses include the differentiation of proteins within a sample and in DNA analysis.
Basic electrophoresis involves placing a sample in an electrical field and allowing molecules to migrate towards the electrical poles based on their charges - the most highly charged move furthest. Additionally, and perhaps most importantly with respect to biological analysis, when the samples are placed within a matrix gel then the smaller molecules will move further than the larger ones. Various forms of this separation through a matrix are known as capillary electrophoresis, gel electrophoresis and capillary gel electrophoresis.
Inside the electrical field matrix, molecules that are all of the same size and charge will all move the same distance whereas other molecules of different sizes will move a different distance. This produces characteristic bands or stripes and each band will represent a specific molecule. The bands are often stained using chemical dyes to make them easier to analyse.
90% of people with multiple sclerosis have been found to have elevated amounts of an antibody protein called immunoglobin-G (IgG) in their cerebrospinal fluid (CSF) to a greater degree than is present in their blood serum. Capillary electrophoresis will show these increased levels as IgG oligoclonal bands. By applying a simple formula to the capillary electrophoresis results of both fluids, it is possible to determine the CSF IgG index, the CSF IgG synthesis rate and CSF IgG/Albumin ratio. A sample is considered positive for CSF oligoclonal bands if there are two or more bands in the CSF immunoglobulin region that are not present in the serum.
During MS relapses, elevated levels of myelin basic protein (MBP) are often detectable through electrophoresis as are other proteins.
None of the protein bands are definitive for MS and up to 10% of CSF samples from people with clinically definite MS can yield negative electrophoresis results.
Diseases such as sub-acute sclerosing panencephalitis, herpes simplex encephalitis, meningeal carcinomatosis, meningoencephalitis, neurosyphilis, Guillain-Barré Syndrome among others cannot be definitively differentiated from multiple sclerosis through electrophoresis.
CSF sample collection is done via a spinal tap.
Capillary electrophoresis has become a very important tool in the diagnosis and profiling of many diseases because it can separate a wide range of biological molecules such as inorganic ions, organic acids, amino acids, peptides, drugs, vitamins, steroids, hormones, carbohydrates, proteins and nucleic acids. It is also used for early detection of disease states such as cystic fibrosis, for DNA finger-printing and the detection of banned drugs in athletes.
What is Electrophoresis ?
Application of Capillary Electrophoresis in Clinical Diagnosis
Kitchen Electrophoresis - Background Information
The Electrophoresis Society