As the protein travels through this pH gradient, its various ionizable groups either pick up or lose protons. Eventually, it will find a pH where its charge is zero and it will get stuck at that point.
DNA Agarose Gels: A simple way of separating large fragments of DNA from one another by size is to use an agarose gel. Agarose is another type of matrix used for many purposes (such as the support for the growth of bacteria on plates). DNA does not need a detergent, since it is already has a large under of negative phosphate groups evenly spaced. Thus, as with SDS-PAGE, the charge to mass ratio is constant. In addition, like SDS-PAGE the separation results from the matrix itself. The range of size sensitivity can be varied by changing the density of agarose.
DNA Denaturing Polyacrylamide Gels: To look at smaller DNA molecules with much higher resolution, people generally denature the DNA via heat and run it through a thin polyacrylamide gel that is also kept near the denaturing temperature. These gels usually contain additional denaturing compounds such as Urea. Two pieces of DNA that differ in size by 1base can be distinguished from each other this way.
Capillary Electrophoresis: This is an automated analytical technique that separates species by applying voltage across buffer filled capillaries. It is generally used for separating ions, which move at different speeds when the voltage is applied depending on their size and charge. The solutes are seen as peaks as they pass through the detector and the area of each peak is proportional to their concentration, which allows quantitative determinations. Analysis includes purity determination, assays, and trace level determinations. Analysis times are in the region of 1-30 minutes depending on the complexity of the separation.
Immunoelectrophoresis: There are two major types of electrophoresis: protein electrophoresis and immunoelectrophoresis.