Electrophoresis/ Cataphoresis: Definition, principle, and application

Electrophoresis, or cataphoresis, is the migration and separation of charged particles (ions) under the influence of an electric field. Ferdinand Frederic Reuss was the first person to detect electrophoresis in 1807. If the sol particles migrate toward the positive electrode, they carry a negative charge; on the other hand, if they migrate toward the negative electrode, they are positively charged. Thus, by noting the direction of movement of the sol particles, we can determine whether they carry a positive or negative charge.

Electrophoresis is a method of separating a mixture of organic compounds. The technique of electrophoresis is used in separating proteins (hemoglobin, serum proteins, lipoproteins isoenzymes) and nucleic acid. It is most useful in the diagnosis of hemoglobinopathies. Electrophoresis is hard to apply on a large scale and it, therefore, does not use preparatory.

Principle of Electrophoresis

Electrophoresis is the migration of charged particles in an electric field. Electrophoresis is performed in a U-shaped tube called Burton’s tube. This tube consists of two electrodes. To perform electrophoresis, a certain amount of sol is taken in the tube along with de-ionized water, and electricity is passed. If sol particles are positively charged, then sol levels rise toward the cathodic end, and if negatively charged, sol levels rise toward the anodic end. Thus, by observing the migration of sol particles, we can ascertain the charge present in the dispersed phase.

Electrophoresis of sol

The protein has both amnio as well as a carboxyl group that can potentially carry + or – charges depending on whether the pH of the medium is acidic or alkaline. At low pH, the negative charge is dominant and moves towards the positive pole (anode), and at high pH, the positive charge is dominant. Thus at particular pH, called the isoelectric point, two charges will be equal or the sol will be uncharged. Because of this, protein sol does not show the phenomenon of electrophoresis at the isoelectric point.

Gel electrophoresis

Gel electrophoresis is a laboratory technique for separating DNA, RNA, or protein mixtures based on molecular size. Gel electrophoresis is nearly the sole technology utilized to solve complex separation tasks in genomics and proteomics, where thousands of species must be separated. An electrical field pushes the molecules to be separated through a gel with microscopic holes in gel electrophoresis. The molecules move through the pores in the gel at a rate that is proportional to their length.

gel elctrophoresis
Gel electrophoresis

Electrophoresis allows you to differentiate between DNA fragments of various lengths. Since DNA is negatively charged, when an electric current is supplied to the gel, DNA migrates to the positively charged electrode. Because shorter strands of DNA move faster across the gel than longer strands, the fragments are arranged in order of size.

Application of Electrophoresis

  • Removal of smoke from chimney gases.
  • Since different sol particles migrate at different rates, so, electrophoresis is used for their separation.
  • electro-plating of rubber on the metal surface from latex(sol).
  • Painting of metal parts of cars from colloidal pigments.

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