Why do proteins denature? What changes occur after protein denaturation

What is protein denaturation?

Protein denaturation is a familiar example: the composition of egg whites is mainly protein. When cooked, the egg whites become egg whites.

That's when the protein is denatured. After denaturation, the spatial structure of the protein changes, and the function changes. For example, the chemical nature of salivary amylase is protein, which can catalyze the hydrolysis of starch, but if salivary amylase is denatured, salivary amylase loses its role in catalyzing starch hydrolysis.

The spatial structure of the protein is destroyed under the action of some physical and chemical factors, but it does not involve the change of the primary structure, resulting in the loss of its biological activity, the increase of viscosity, the decrease of diffusion coefficient, the decrease of solubility, the decrease of sedimentation coefficient, and the phenomenon of being easily hydrolyzed by protease.

Protein denaturation is divided into reversible and irreversible denaturation. It can use simple physical methods such as dialysis and osmosis to make protein refolding reversible; Physical methods such as dialysis cannot be used to refold proteins, which is called irreversible denaturation.

1. Eggs, meat, etc. are denatured after heating, and are easier to digest after cooking.

2. Bacteria and viruses are heated, acid plates are added, and metal weights (mercury) are inactivated (sterilized and sterilized) due to protein denaturation.

3. Fixed preservation and embalming of animal and insect specimens.

4. Many toxins are proteins, which are fixed with formaldehyde, and the toxic base groups are attenuated and sealed as toxoid antigens to make antitoxins.

5. It is used for the precipitation of impurities in protein purification.

There are times in our lives when protein denaturation occurs, so what is the cause of protein denaturation?

Under the action of heat, acid, alkali, heavy metal salts, ultraviolet rays, etc., the protein will change its properties and condense. This coagulation is irreversible and can no longer be brought back to their original proteins. This change in the protein is called denaturation, and after the protein is denatured, the ultraviolet absorption, chemical activity, and viscosity will increase, and it will become easy to hydrolyze, but the solubility will decrease.

Protein denaturation has many practical applications, such as ethanol disinfection and sterilization, boiling, clinical ultraviolet irradiation, clinical laboratory heating coagulation reaction to detect urine protein, cooking and eating protein digestion in daily life, etc., but on the other hand, egg protein denaturation in the preparation and preservation of protein preparations (such as enzymes, vaccines, immune serum, etc.) to prevent inactivation.