What is the reason for the decrease in solubility after protein denaturation?

Proteins themselves have zwitterion ions such as -NH3+ and -COO-. Ionic bonds form between them, especially near the isoelectric point, when the ionic bonds are strong and proteins tend to form precipitates. After adding a small amount of salt, the added ions will interact with the ions of the protein itself, break the original ion bonds, and isolate the original groups to promote the dissolution of the protein.

From a thermodynamic point of view, increasing the ionic strength of the solution will reduce the activity coefficient of the ions, so that the concentration of ions will increase under the same activity conditions.

When a large amount of salt is added, the ion concentration in the solution is too large. Too many water molecules are attracted around the hydrated ions, resulting in not enough free water molecules to isolate the hydrophobic region within the protein. These regions bind to the precipitate due to hydrophobic interactions, resulting in a decrease in protein solubility.

1.Salting out reaction of proteins, saturated ammonium sulfate.

Generate a precipitate, let it stand, then pour out a small amount of turbid precipitate, add water, and dissolve the precipitate. Reason: Ammonium sulfate causes the protein to be salted out, which is a reversible precipitation and can be dissolved after adding water.

2.Heavy metal precipitation, add silver nitrate, generate precipitation, stand still, remove the supernatant, add water to the precipitation, and the precipitation is insoluble. Reason:

Heavy metal ions denature proteins and are irreversible precipitation, so they are dissolved without pins after adding water. 3.Add organic acid, add trichloroacetic acid, generate a precipitate, pour off the supernatant, add water to the precipitate, and the precipitate is insoluble.

Cause: Trichloroacetic acid is available as either hydroxyl or carbonyl.

The hydrogen or oxygen, the acid group combines with the positively charged protein to form an insoluble substance, which is irreversible precipitation. The precipitate does not dissolve after adding water. 4.Ninety-five percent ethanol is added to the protein.

Ethanol denatures proteins, producing precipitates.

1) Reversible precipitation: Under mild conditions, the protein is precipitated from the colloidal solution by changing the pH or salt concentration of the solution. During the precipitation process, the structure and properties of the protein do not change significantly, and under the right conditions, the protein can be re-dissolved to form a solution, so this precipitation is also called non-denaturing precipitation.

Reversible precipitation is the basic method of separating and purifying proteins, such as isoelectric point precipitation, saltingout, etc., using organic solvents such as ethanol or acetone at low temperatures.

Acting on proteins for a short period of time can also cause reversible precipitation of proteins.

Neutral salts (ammonium sulfate, sodium sulfate.

sodium chloride, etc.), the effect of protein precipitation and precipitation is called salting-out, and its principle is that a high concentration of salt can destroy the hydration layer and neutralize the charge, so that the protein aggregates. The salt concentration of different proteins is different, for example, globulin can be precipitated in semi-saturated ammonium sulfate solution, while albumin can be precipitated in saturated ammonium sulfate solution. The protein precipitate obtained by salting out can be redissolved in a low-salt solution, and the salting out of proteins called salting out is a reversible process.

2) Irreversible precipitation: Under strong precipitation conditions, the stability of the protein colloidal solution is destroyed, so that the protein precipitates out. Because this strong precipitation condition also destroys the structure of the protein, the resulting protein precipitate can no longer be re-dissolved in water, so it is also called denaturing precipitation.

For example, heating precipitation, heavy metal salt precipitation, organic acid precipitation and alkaloid precipitation are all indispensable: precipitation.

The denaturation of protein refers to the process and phenomenon that the protein is destroyed under the action of physics (high temperature, high pressure) and chemical chemistry (acid, alkali, denaturant), and its psychochemical properties and biological functions are changed at the same time. Denatured proteins tend to aggregate with each other to form sedimentation preservation, and in some cases, the proteins do not precipitate when the conditions that keep the solution stable (e.g., electric charge) still exist. Therefore, denatured proteins do not necessarily appear to precipitate, and precipitated proteins may not all be denatured.

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.

1. Protein denaturation in biochemistry refers to the phenomenon that proteins or nucleic acids are affected by certain physical and chemical factors, and their higher structure is destroyed and thus loses biological activity.

2. The denaturation process of proteins is of great significance in real life. The pre-slag plexus usually uses ethanol, heating, and ultraviolet light for disinfection and sterilization, which uses the principle of protein denaturation to make the pathogen lose its pathogenicity and reproduction ability. The same is true for taking a large amount of dairy products or egg whites during mercury poisoning, using the denaturing effect of heavy metal salts on the proteins in dairy products or egg whites, and the mercury is combined into insoluble substances and washed out by gastric lavage and other methods to avoid its absorption by the digestive tract.

3. Protein denaturation does not necessarily precipitate. It is only a change in the spatial structure, the basic first-level structure has not been destroyed, and it can be repented under certain conditions. It's just that the vast majority of conditions are quite harsh.

4. Protein precipitation is not necessarily denatured. Salting out is an example such as cherry blossoms. Although the hydration layer is removed, the peptide chain does not change to an elongated state, and the structure above the second order changes.

Answer]: C Analysis: Under the action of certain physical and chemical factors, the specific spatial conformation of the protein is destroyed, which leads to the change of the chemical properties and the loss of biological activity, which is called the denaturation of the protein (C).

Protein denaturation Wupei mainly undergoes the destruction of disulfide bonds and non-covalent bonds, no peptide bond breakage, and does not involve the change of amino acid sequence in the primary structure, so there is no subunit depolymerization and detachment of the cospittocarpan group.

Problem 1: After the egg is cooked, the protein is denatured and inactivated, which is due to the high temperature destroying the ( ) a peptide bond b peptide chain c spatial structure d amino group a, high temperature will not destroy the peptide bond, and the peptide bond breaking is inseparable from the osmotic effect of the enzyme, a is wrong; b. Temperature does not affect the structure of the peptide chain, and the hydrolysis of the peptide chain is inseparable from the action of enzymes. c. High temperature destroys the spatial structure of protein molecules, so that the protein is denatured, C is correct; d. Amino acids are the basic building blocks of protein, after the egg is cooked, the amino acids in the process of protein denaturation and inactivation are not destroyed, D is wrong, so choose: C

Problem 2: Protein denaturation is due to protein molecules Protein denaturation is due to the fact that proteins are affected by the conditions of high temperature, strong acid, and strong alkali, and the spatial structure is changed, which is an irreversible process.

Question 3: What happens if the peptide bond of a protein is broken? Protein denaturation and inactivation are due to the destruction of peptide bond structure, why is it a misaligned cluster? 50 points c Spatial structure.

A and B are actually about the same, to break the peptide bond to use peptidase, to break the phthalein chain in addition to the peptide bond, but also to break the disulfide bond between the phthalein chain; d is an obvious mistake to destroy amino acids to have acids or bases.

So choose c Question 4: Protein denaturation is mainly due to what bond is broken hydrogen bond, which is in the structure of the protein, biochemistry,