The history and basic principles of electrophoresis-Electrophoretic Materials

In 1809, Russian physicist Tsar ейсе first discovered the phenomenon of electrophoresis. He inserted positive and negative electrodes with glass tubes into wet clay, and after applying voltage, found that the original water layer in the positive glass tube became turbid, that is, negatively charged clay particles moved towards the positive electrode, which is the phenomenon of electrophoresis.

In 1909, Michaelis first referred to the movement of colloidal ions in an electric field as electrophoresis. He measured the electrophoretic mobility and isoelectric points of invertase and catalase using solutions of different pH values in a U-shaped tube.

In 1937, Tiselius from Uppsala University in Sweden improved the electrophoresis instrument, created the Tiselius electrophoresis apparatus, established a mobile interface electrophoresis method for studying proteins, and for the first time proved that serum is composed of albumin and alpha, beta, and gamma globulin. Due to Tiselius' pioneering contributions in electrophoresis technology, he was awarded the Nobel Prize in Chemistry in 1948.

In 1948, Wieland and Fischer redeveloped the electrophoresis method using filter paper as a support medium and studied the separation of amino acids. Since the 1950s, especially after Durrum used paper electrophoresis to separate various proteins in 1950, it has pioneered a zone electrophoresis method using various solid substances (such as various filter papers, cellulose acetate films, agar gel, starch gel, etc.) as support media.

In 1959, Raymond and Weintraub created polyacrylamide gel electrophoresis using synthetic gel as the support medium, which greatly improved the resolution of electrophoresis technology and ushered in a new era of modern electrophoresis. 

For more than 30 years, polyacrylamide gel electrophoresis is still the most widely used and highest resolution analysis and identification technology for biological macromolecules such as protein, polypeptide, nucleic acid, etc. in biochemistry and molecular biology. It is the standard analysis and identification method for testing the highest purity of biochemical substances, namely, "electrophoresis purity" (one band of one-dimensional electrophoresis or one point of two-dimensional electrophoresis). It is still known as the last analysis and identification of biological macromolecules

The most accurate method is' Last Check '.

The new capillary electrophoresis technology developed in the 1980s is an important new development in chemical and biochemical analysis and identification techniques, and has received full attention from people.

Electrophoresis refers to the process of charged particles migrating under the action of an electric field. Many important biomolecules, such as amino acids, peptides, proteins, nucleotides, nucleic acids, etc., have ionizable groups that can carry positive or negative charges at a specific pH value. Under the action of an electric field, these charged molecules will move towards the electrode direction opposite to the polarity of their charge. Electrophoretic technology is a technique that utilizes the charged properties of various molecules in the sample to be separated, as well as the intrinsic properties of the molecules, under the action of an electric field

The difference in body size, shape, and other properties causes charged molecules to have different migration speeds, thereby enabling the separation, identification, or purification of samples.

The electrophoresis process must be carried out in a supporting medium. The free interface electrophoresis conducted by Tiselius et al. in 1937 did not have a fixed supporting medium, so diffusion and convection were relatively strong, affecting the separation efficiency. Thus, electrophoresis with a fixed support medium emerged, where the sample undergoes electrophoresis in a fixed medium, reducing interference such as diffusion and convection. The initial supporting media were filter paper and cellulose acetate membrane, which are currently less commonly used in laboratories.

 For a long time, small molecule substances such as amino acids, peptides, sugars, etc. were usually separated and analyzed by electrophoresis using filter paper or cellulose or silica gel thin layer plates as media. However, currently, more sensitive techniques such as HPLC are generally used for analysis. These media are suitable for separating small molecule substances and are easy and convenient to operate. But for complex biomolecules, the separation effect is poor. The introduction of gel as a support medium has greatly promoted the development of electrophoresis technology, making it one of the important means to analyze biological macromolecules such as proteins and nucleic acids. The original gel was starch gel, but at present, agarose gel and polyacrylamide gel are the most widely used. Polyacrylamide gel is mainly used for protein electrophoresis.

The electrophoresis device mainly consists of two parts: power supply and electrophoresis tank. The power supply provides direct current, generating an electric field in the electrophoresis tank to drive the migration of charged molecules. Electrophoresis tanks can be divided into two types: horizontal and vertical. Vertical plate electrophoresis is a common method for protein separation in polyacrylamide gel electrophoresis. In the middle of the electrophoresis tank are two glass plates sandwiched together. The two sides of the glass plates are separated by plastic strips. Electrophoretic gel is prepared in the middle of the glass plate. The size of the gel is usually 12cm ′ 14cm and the thickness is 1mm~2mm. 

The newly developed electrophoresis tank in recent years has a smaller and thinner gel surface to save reagents and shorten the electrophoresis time. A plastic comb is placed in the gel solution during glue making, and removed after glue polymerization to form a groove on the sample. Horizontal electrophoresis: gel is laid on horizontal glass or plastic plate, and a thin layer of wet filter paper is used to connect gel and electrophoresis buffer, or gel is directly immersed in buffer. Due to the change in pH value causing a change in the charge of charged molecules, which in turn affects their electrophoretic migration speed, the electrophoresis process should be carried out in an appropriate buffer solution, which can maintain the stability of the charged properties of the separated substance.