Denaturation of the protein

The conformation (structure) of the peptide chain is ordered and unique for each protein. Under special conditions, a large number of bonds break, which stabilize the spatial structure of the molecule of the compound. As a result of the rupture, the whole molecule (or a significant part of it) takes the form of a disorderly coil. This process is called "denaturation." This change can be provoked by heating from sixty to eighty degrees. Thus, each molecule obtained as a result of the rupture may differ in conformation from the others.

Denaturation of proteins occurs under the influence of any agents capable of destroying non-covalent bonds. This process can occur in alkaline or acidic conditions, on the surface of phase separation, under the influence of certain organic compounds (phenols, alcohols and others). Denaturation of the protein can also occur under the influence of guanidine chloride or urea. These agents form weak bonds (hydrophobic, ionic, hydrogen) with the carbonyl or amine groups of the peptide backbone and with a number of groups of amino acid radicals, replacing the hydrogen bonds existing within the protein within the molecule. As a result, there is a change in the secondary and tertiary structure.

The resistance to the action of denaturing agents depends primarily on the presence of disulfide bonds in the molecule of the protein compound. The trypsin inhibitor has three S-S bonds. Under condition of their reduction, protein denaturation occurs without other influences. If, afterwards, the compound is placed in the conditions where the oxidation of SH-groups of cysteine occurs and the formation of disulfide bonds occurs, then the initial conformation will be restored. In this case, the presence of even one disulfide bond significantly increases stability in the spatial structure.

Denaturation of the protein, as a rule, is accompanied by a decrease in its solubility. At the same time, a precipitate is often formed. It appears in the form of a "curdled squirrel". When the concentration of compounds in the solution is high, "coagulation" undergoes the entire solution, as, for example, when cooking chicken eggs. When denatured, the protein loses its biological activity. This principle is based on the use of carbolic acid (an aqueous phenolic solution) as an antiseptic.

The instability of the spatial structure, the high probability of destruction under the influence of a variety of agents, make it very difficult to isolate and study the protein. Certain problems are also created when using compounds in industry and medicine.

If the denaturation of the protein was carried out by exposure to high temperatures, then under slow cooling, under certain conditions, a process of renativation takes place-the restoration of the native (initial) conformation. This fact proves that the laying of the peptide chain takes place in accordance with the primary structure.

Formation of the native conformation (initial location) is a spontaneous process. In other words, this arrangement corresponds to the minimum amount of free energy enclosed in the molecule. As a result, it can be concluded that the spatial structure of the compound is encoded in the amino acid sequence in the peptide chains. This, in turn, means that all polypeptides similar in amino acid sequence (eg, myoglobin peptide chains) will take an identical conformation.

Proteins can have significant differences in the primary structure, even if they are practically or absolutely identical in conformation.