Electrofocusing, or isoelectric focusing, is a technique for separating different molecules by their electric charge differences (if they have any charge). It is most commonly used on proteins.
It is a type of zone electrophoresis that takes advantage of the fact that a molecule's charge changes as the pH of its surroundings changes.
Molecules are distributed over a medium that has a pH gradient (usually created by aliphatic ampholytes). An electric current is passed through the medium, creating a "positive" and "negative" end. Negatively charged particles migrate through the pH gradient toward the "positive" end while positively charged particles move toward the "negative" end. As a particle moves into a pH that neutralizes its charge, it will stop following the current. Particles of the same initial charge will deposit (or focus) around the same place on the pH gradient.
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