Alkali protein solubility changes

Derived Proteins.—A few primary protein derivatives have been mentioned in connection with the substances described above. Paracasein and fibrin are formed as the result of the action of certain enzymes on casein and fibrinogen, respectively. The metaproteins are obtained by treating proteins with dilute acids or alkalies. Acids form acid-proteins, which are soluble in acids and insoluble in alkalies. The latter form soluble alkali-proteins, which are precipitated by acids. Many soluble proteins are changed into insoluble substances (coagulated) when heated. The derived proteins resemble closely the substances from which they are formed except in solubility. The nature of the change is not understood. It is possible that the conversion of a protein into a primary derivative may be associated with a change in the colloidal condition of the molecule. 

To change the molecular structure of globular proteins by bringing a protein solution to its boiling point and exposing it to acids or alkalies or various detergents. The process reduces the solubility of proteins and prevents crystallization. 

The e-elimination reaction could also be used to change the solubility properties of a protein. For example, alkali treatment in the presence of sodium sulfite leads to incorporation of sulfonate groups into the protein (44,53) which would increase its water solubility and probably change its functional properties. 

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