Question

What other class of molecule besides salts are commonly used for fractional precipitation of proteins

Answer 1

Following molecules can also be used to precipitate proteins in addition to salts :

1. Miscible solvents, like Ethanol and Methanol : They replace water layer from the protein and cause aggregation of proteins.

2. Polymers, for example Dextran and Polyethylene Glycol : These polymers also attract water molecules away from proteins and cause it to precipitate.

3. Alginate, tannic acid etc can also be used.

4. Metal ions can also be used , for example : Ca²⁺, Mg²⁺ etc.