Technology may enable the development of tests for mad cow diseaseTechnology may enable the development of tests for mad cow disease
March 1, 2003
Originally Published MPMN March 2003
Technology may enable the development of tests for mad cow disease
Separation by charge and size of specific molecules from a complex mixture can be achieved with the Gradiflow process.
A new technology can concentrate and remove infectious and noninfectious prion proteins from human biological samples in laboratory studies, according to Gradipore (Frenchs Forest, New South Wales, Australia). This process, called Gradiflow, could be used to develop a diagnostic test for a transmissible spongiform encephalopathy (TSE) disease such as new variant Creutzfeldt-Jakob (nvCJD), the human form of mad cow disease. It could also be useful for helping in the detection of other TSEs including scrapie and bovine spongiform encephalopathy (known as mad cow disease).
"Gradiflow is an enabling technology and not a diagnostic tool; i.e., it allows other diagnostic tools to be more sensitive and usable because our technology purifies and concentrates prions," says Hari Nair, the company's chief operating officer in the United States and general manager of its commercial separations division. Prions are thought to be the cause of TSEs.
"Prions exist in very low concentrations in the body, and the cross reaction with other proteins makes the identification of these prions difficult. Also, because our technology uses an electrical field, the structure and function of the target prion is not disturbed," Nair explains.
The Gradiflow-based electrophoresis instrument has two circulating streams that are divided by a separation membrane and confined by restriction membranes. Since in an electric field a molecule will move toward the electrode of opposing charge, the electrodes are positioned so that Stream 1 contains molecules with a positive charge and Stream 2 molecules that are negatively charged. Charged molecules can be moved between the streams when a current is applied. This allows the separation by charge and size of specific molecules from a complex mixture.
Molecules such as proteins have different charges depending on the acidity of the solution. If the acidity level is close to the isoelectric point (pI) of a protein that substance will have little charge under an electric field. Two molecules with different pIs may be separated by performing the Gradiflow process at a pH level between the two pI values. This causes one molecule to have a net positive charge and the other molecule a net negative charge. For example, positively charged molecules are attracted toward the negative electrode and remain in Stream 1. The negatively charged molecules migrate toward the positive electrode through the separation membrane and into Stream 2.
Size separations are performed by using separation membranes with different pore sizes. For example, when a high pH buffer is used, it imparts a net negative charge on all of the molecules. The larger negatively charged molecules are unable to migrate through the separation membrane due to size constraint and are maintained in Stream 1. The small negatively charged molecules are able to migrate through the separation membrane toward the positive electrode and are contained in Stream 2.
Nair says Gradipore is currently talking to a number of diagnostic companies that are interested in this technology.
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