The conformation (structure) of the peptide chain is ordered and unique for each protein. Under special conditions, a large number of bonds break, which stabilized the spatial structure of the compound molecule. As a result of the rupture, the entire molecule (or a significant part of it) takes the form of a disordered ball. This process is called "denaturation." This change can be triggered by heating from sixty to eighty degrees. Thus, each molecule resulting from a break can differ in conformation from the others.
Protein denaturation also occurs under the influence of any agents capable of breaking non-covalent bonds. This process can happen in alkaline or acidic conditions, on the surface of the phase separation, under the influence of some organic compounds (phenols, alcohols, and others). Protein denaturation can also occur under the influence of guanidine chloride or urea. These agents form weak bonds (hydrophobic, ionic, hydrogen) with the carbonyl or amino groups of the peptide backbone and with a number of groups of amino acid radicals, replacing the intrinsic hydrogen bonds present in the protein inside the molecules. As a result, a change occurs in the secondary and tertiary structure.
Resistance to denaturing agents depends mainly on the presence of disulfide bonds in the protein compound. The trypsin inhibitor has three S - S bonds. Provided that they are restored, protein denaturation occurs without other effects. If, subsequently, the compound is placed under conditions where the oxidation of SH-groups of cysteine and the formation of disulfide bonds are carried out, the initial conformation will be restored. Moreover, the presence of even one disulfide bond significantly increases the stability in the spatial structure.
Protein denaturation is usually accompanied by a decrease in its solubility. Along with this, a precipitate is often formed. It arises in the form of "curled protein." With a high concentration of compounds in the solution, “coagulation” undergoes the entire solution, as, for example, this happens when cooking chicken eggs. When denatured, the protein loses its biological activity. The use of carbolic acid (aqueous phenolic solution) as an antiseptic substance is based on this principle.
The instability of the spatial structure, the high probability of destruction under the influence of various agents significantly complicate the isolation and study of protein. Certain problems are also created when using compounds in industry and medicine.
If protein denaturation was carried out by exposure to high temperatures, then with slow cooling under certain conditions, the process of renovation takes place - restoration of the native (initial) conformation. This fact proves that the folding of the peptide chain occurs in accordance with the primary structure.
The formation of the native conformation (initial location) is a spontaneous process. In other words, this arrangement corresponds to the minimum amount of free energy contained in the molecule. As a result, we can conclude 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 that are similar in the alternation of amino acids (for example, 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.