Electrophoresis refers to the movement of dispersed charged particles under the influence of an applied uniform electric field. The electrophoresis of positively charged particles is called cataphoresis, while the electrophoresis of negatively charged particles is called anaphoresis.
A specific type of electrophoresis called ‘gel electrophoresis’ is used very frequently in chemistry. It uses the varying rates of movements of different charged macromolecules (e.g. proteins) to separate them by either charge or size.
The basic process of separating by size involves using SDS to linearize proteins, by breaking any native intra-molecular bonds, and impart a uniform negative charge to these proteins. Then in a polyacrylamide gel (PAGE), a uniform electric field is applied. The larger the charged macromolecules the slower it will move through the gel and vice versa.
On the other hand, isoelectric focusing (IEF) separates proteins based on charge. This is done by creating an ion gradient in the gel, so the sample proteins will migrate towards their respective isoelectric point, which is the pH at which the surface carries no net electrical charge.
Exploiting the differences in charge or size is useful, but exploiting both at the same time is even more effective at separating and identifying different macromolecules within a sample. This feat can be achieved through a process known as 2D-Gel Electrophoresis, which separates by size in the x-axis, and by charge in the y-axis. The result is a two-dimensional migration of the macromolecules.
Thus, understanding the underlying concepts behind electrophoresis is important for knowing how to exploit macromolecules based on size and charge.
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