Agarose gel electrophoresis for DNA detectionExperimental principle agarose gel electrophoresis is a typical method for the isolation, purification and identification of DNA fragments, which is characterized by simplicity and rapidity.

The principle of agarose gel electrophoresis of DNA fragments is basically the same as that of protein electrophoresis, the DNA molecule carries a negative charge in the pH solution higher than its isoelectric point, and moves toward the positive pole in the electric field.DNA molecules swim through the medium in the electric field, and in addition to the charge effect, the gel medium also has a molecular sieve effect, which is related to the molecule size and conformation.

For linear DNA molecules, their mobility in the electric field is inversely proportional to the logarithmic value of their molecular weight. Nucleic acid molecules are amphoteric dissociation molecules, pH 3.5 is the amino group on the base dissociation, and only one of the three phosphate groups phosphate dissociation, so the molecule is positively charged, in the electric field to the negative pole swimming; and pH 8.0-8.3, the base is almost not dissociated, and the phosphate group dissociation, so the nucleic acid molecules are negatively charged, in the electric field to the positive pole swimming.

Introduction to agarose and electrophoresis:

Agarose is a linear polymorph with the basic structure of a long chain of alternating 1,3-linked β-D-galactose and 1,4-linked 3,6-endoether-L-galactose. Agar pectin is a heterogeneous mixture of many smaller molecules.

Agarose generally dissolves in water when heated above 90°C and forms a good semi-solid gel when the temperature drops to 35-40°C. This is the main feature and basis for its many uses. Agarose gel properties are usually expressed in terms of gel strength. The higher the strength, the better the gel properties. Electrophoresis is the phenomenon in which charged particles move toward an electrode opposite to their electrical properties under the action of an electric field. The technique that utilizes the different speeds at which charged particles move in an electric field to achieve separation is called electrophoresis.