Why is protein most likely to precipitate at its isoelectric point? Draw pictures to support your...

Why is protein most likely to precipitate at its isoelectric point? Draw pictures to support your explanation.

Expert Solution

Ans. On a pH other than isoelectric pH (pI), the protein bears some net negative or net positive charge. Presence of charge on protein makes is better solvated in a solution (like, cations and anions are better solvated in water than the elemental state of the atom).

At isoelectric point (= isoelectric pH), the net charge on protein is zero, i.e. no atom or group in the protein is in ionized state. Nullifying the net charge on protein reduces its solubility in aqueous solution because lesser is the net charge (irrespective of positive or negative charge) on protein, lesser is the interaction among residues on protein and the water molecules in aqueous solution. Therefore, isoelectric point is most likely to precipitate the protein due to reduced solubility.

# Shown here a pentapeptide whose net charge is nullified when transferred to a solution with pH = pI of protein.

queen_honey_blossom answered 2 years ago

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