Why can protein denaturation also be tested with biuret reagent?

A biuret reaction is one with two or more peptide bonds.

The compound reacts with Cu2+ under alkaline conditions to form a reddish-purple complex.

Because the protein molecule contains many peptide bonds similar to the structure of biuret, the biuret reaction can also occur, therefore, the structure of diurea (H2NOC-NH-Conh2) in the protein reacts with Cu2+ in copper sulfate solution in alkaline solution (NaOH) to form a purple complex. So biuret reagent.

Proteins can be identified because there are many peptide bonds in the protein that are structurally similar to biuret.

Where a molecule contains two or more amide bonds.

peptide bonds) compounds such as polypeptides, proteins, etc., can react purplely with biurea. This is because the peptide bonds of proteins and peptides are structurally similar to those of biurea, and can also form purplish-red complexes with Cu2+. Amino acid.

There are no peptide bonds in the molecule, and there is only one peptide bond in the dipeptide molecule, so biuret reagents can be used to detect proteins and peptides, but not to detect dipeptides and amino acids.

High temperature does not destroy peptide bonds, denaturation refers to the loss of function caused by changes in the higher order structure of proteins, that is, conformation, and this process does not necessarily involve changes in primary results, so the double shrinkage reaction to detect peptide bonds is still applicable.

Because the alkali in this reagent can denature the protein, the denatured protein can still be tested in this way.

Diuret is made up of two moleculesUreaThe condensed compound heats the urea to 180 degrees, then the two molecules of urea are condensed into one molecule of biurea, and one molecule of ammonia is released.

Diurea bicarib can be used with copper sulfate in alkaline solution.

The reaction produces a reddish-purple complex.

This reaction is called the biuret reaction.

Protein molecules contain many peptide bonds that are structurally similar to biuret.

Therefore, it can also cause a biuret reaction to form a reddish-purple complex.

This principle is not required to be mastered in high school, and it is enough to know the reaction phenomenon.

Biuret reagent.

It is an analytical chemical reagent used to identify proteins. It is an alkaline copper-containing test solution that is blue in color and consists of g ml sodium hydroxide.

or potassium hydroxide, g ml copper sulfate and potassium sodium tartrate.

The biuret reagent is originally used to detect biuret, because the protein molecule contains many peptide bonds that are structurally similar to biuret, so it can also be compared with copper ions.

The biuret reaction occurs in an alkaline solution. When the substrate contains peptide bonds, the copper in the solution is coordinated with the polypeptide, and the complex is purple. Concentrations can be analyzed colorimetrically, with a wavelength of 540 nm in the UV-Vis spectrum.

The sensitivity of the identification reaction is 5-160 mg ml.

The copper sulfate that really works in the biuret reagent is potassium hydroxide only to provide an alkaline environment, so it can be replaced by other bases such as sodium hydroxide. Add potassium iodide to the reagent.

will prolong the life of the reagent. The function of potassium sodium tartrate is to protect the complex ions generated by the reaction from being precipitated into precipitation, so that the reagent becomes ineffective.

The biuret reagent is originally used to detect bicicolimb silver urea, because the protein molecule contains many structures similar to biuretPeptide bonds, so it can also react with copper ions in an alkaline solution.

In the alkaline solution, biuret combines with copper ions to form a complex dust banquet purple luster complex. The peptide bonds of proteins and peptides are similar to those of biurea, and can also form purple-red complexes with Cu2+.

Its maximum light absorption is at 540 nm. The shade of color is proportional to the protein concentration, and to the molecular weight and amino acids of the protein.

The concentration range of the protein determined by this method is suitable for 1 10 mg ml. The biuret method is commonly used for rapid determination of proteins.

Precautions for the detection of biuret reagent

When using the biuret reagent, it is important to note that g ml of sodium hydroxide must be added first.

solution, plus g ml of copper sulfate.

Hunger solution.

If copper sulfate [CuSO4] solution is added first, and then sodium hydroxide [NaOH] solution is added, the alkaline environment cannot be fully created, and CuSO4 will metabolize with NaOH at this time.

Blue copper hydroxide [Cu(OH)2] precipitation was generated, which led to unclear phenomena and could not achieve the experimental purpose.

The above content refers to Encyclopedia-Biscarylurea Reagent.

Since the protein molecule contains many structures similar to biuretPeptide bonds, in an alkaline solution,Biuret reagent. It can react with proteins to form a purple colorComplexesTherefore, the experimental principle of the detection effect of the protein is that the biuret reagent reacts with the protein in purple.

It is used to detect biuret, because the protein molecule contains many peptide bonds similar to the structure of biuret, so it can also be compared with copper ions.

The biuret reaction occurs in an alkaline solution. When the substrate contains peptide bonds, the copper in the test solution is coordinated with the polypeptide, and the complex is purple. Concentrations can be analyzed colorimetrically, in the UV-Vis spectrum.

The wavelength in is 540nm. The sensitivity of the identification reaction is 5-160 mg ml.

Protein evaluation of biuret reagent detection:

Advantages: The determination range of protein by biuret method is 1 10mg protein, which is simple and fast. It is suitable for both manual operation and automated analysis, and repeatability.

Good linear relationship, diuret reagent can be stored for a long time (if there is a black sinking chain burning lake in the storage bottle, it needs to be reconstituted).

Disadvantages: Poor sensitivity, narrow measurement range, large sample requirements, and similar shades of color produced by different proteins, so it is often used for protein assays that require fast, but do not require accurate ten-point execution. Substances that interfere with the assay include amino acids that are natured.

or peptide buffers.

As in TRIS buffers, because they produce a positive color reaction, copper ions are also easily reduced, sometimes with red precipitates.

The above content reference: shed code encyclopedia - biuret reagent.