The larger the protein the more slowly it will move through the matrix of the polyacrylamide. Following electrophoresis the migration distance of unknown proteins relative to known standard proteins is assessed by various staining or radiographic detection techniques. This technique is termed isoelectric focusing . Isoelectric focusing utilizes a thin tube of polyacrylamide made in the presence of a mixture of small positively and negatively charged molecules termed ampholytes. The ampholytes have a range of pIs that establish a pH gradient along the gel when current is applied.
Analytical centrifugation measure the rate that proteins sediment.
Michael W. KING, Ph.