Isoelectric point of protein: When the protein solution is at pH, the protein has an equal tendency to dissociate into positive and negative ions, becoming zwitterionic ions with a net charge of zero. At this time, the pH of the solution is called the isoelectric point of the protein.

protein electrophoresis

protein chromatography

Factors that stabilize protein colloids

Dialysis and ultrafiltration

protein precipitation

protein denaturation Under the action of certain physical and chemical factors, the specific spatial conformation of proteins is destroyed, that is, the ordered spatial structure becomes a disordered spatial structure, resulting in changes in its physical and chemical properties and loss of biological activity.

It is generally believed that protein denaturation mainly occurs through the destruction of disulfide bonds and non-covalent bonds, and does not involve changes in the amino acid sequence in the primary structure.

Protein renaturation If the degree of protein denaturation is minor, the protein can still recover or partially recover its original conformation and function after removing the denaturing factors.

protein precipitation Under certain conditions, when the hydrophobic side chains of proteins are exposed, the peptide chains will tangle with each other and then aggregate, thus precipitating from the solution.

Protein coagulation The deformed floc of the protein can be turned into a relatively solid clot when heated, and this clot is not easily redissolvable in strong acids and alkalis.

Since protein molecules contain conjugated double bonds of tyrosine and tryptophan, they have a characteristic absorption peak at a wavelength of 280nm.

Ninhydrin reaction

biuret reaction