Question

What other class of molecule, besides salts, is commonly used for fractional precipitation of proteins that preserves them in their folded state?

Answer 1

Some other classes used for fractional precipitation of proteins that preserves them in their folded state are:

1.Miscible solvents :- Addition of miscible solvents such as ethanol or methanol to a solution may cause proteins in the solution to precipitate. The solvation layer around the protein will decrease as the organic solvent progressively displaces water from the protein surface and binds it in hydration layers around the organic solvent molecules. With smaller hydration layers, the proteins can aggregate by attractive electrostatic and dipole forces. Important parameters to consider are temperature, which should be less than 0 °C to avoid denaturation, pH and protein concentration in solution. Miscible organic solvents decrease the dielectric constant of water, which in effect allows two proteins to come close together.

2.Non-ionic hydrophilic Polymers:- Polymers, such as dextrans and polyethylene glycols, are frequently used to precipitate proteins because they have low flammability and are less likely to denature biomaterials than isoelectric precipitation. These polymers in solution attract water molecules away from the solvation layer around the protein. This increases the protein–protein interactions and enhances precipitation.