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The structure modifications during protein denaturation

2019-01-11 来源:亚科官网

Protein denaturation can be seen everywhere in our daily lives. For example, a raw egg will become cooked after being boiled. This is the best performance of protein denaturation. As early as the 1920s, Wu Xian proposed the concept of protein denaturation firstly. He pointed out that protein denaturation is not changes caused by its chemical structure but in spatial structure. And the theory has been widely accepted by the international biochemistry community.

What is protein denaturation?

Protein denaturation refers to the electrons outside the acyloxy atom in a protein molecule affected by protons and moves toward protons, and the electrons in the adjacent carbon nuclei move toward oxygen, the nucleus is relatively nucleated. The molecules are made larger and the fluidity is deteriorated. To put it another way, protein denaturation is not caused by changes of its chemical structure but in its spatial structure.

Factors affecting protein denaturation

In general, the factors that can affect protein denaturation are mainly classified into physical factors and chemical factors. Physical factors mainly include heating, pressurization, stirring, shaking, drying, ultraviolet irradiation, ultrasonic action, etc.; chemical factors mainly include heavy metal salts, strong acids, strong alkalis, trichloroacetic acid, ethanol, acetone, formaldehyde, urea, etc.

When the protein is denatured by heating, shaking, ultraviolet irradiation, etc., various secondary bonds such as hydrogen bonds in the protein molecule are destroyed (for example, heating is a thermal motion to break a hydrogen bond), and the spatial structure is destroyed and changed. This leads to changes in its physical and chemical properties and loss of biological activity, but there is no breakage and formation of covalent bonds during the change, and the chemical composition of the protein does not change (no other substances are produced), so the change in protein is mainly physical changes, that is, protein denaturation caused primarily by physical changes. When ethanol, acetone, etc. are mixed with proteins, since these organic substances have strong hydrophilic ability, they can both disappear the hydrated film on the surface of the protein colloid, make it agglomerate and precipitate, and enter the voids of the polypeptide chain to break hydrogen bond and other secondary bonds, thereby denatures the protein. Therefore, there is no breakage and formation of covalent bonds during the change, and protein denaturation is mainly caused by physical changes.

The heavy metal salt denatures the protein because the heavy metal cation can form insoluble salt with the free carboxyl group in the protein, and the chemical bond is broken and formed during the change. Strong acid and strong base denature the protein because they can both break the hydrogen bond and react with the free amino or carboxyl group in the protein to form a salt, that is, the chemical bond breaks and generates during the change. Therefore, in the process of denaturation of proteins by heavy metal salts, strong acids, strong bases, etc., chemical changes occur, and the denaturation of proteins is mainly caused by chemical changes.

Proteins may be denatured by any combination of one or more of the above factors. Since the conformation of proteins in denaturation varies widely, small conformational changes cannot be detected by current experimental means, while general physicochemical methods can be used to measure larger conformational changes.

Edited by Suzhou Yacoo Science Co., Ltd.