Hi,
Is it efficient to use pI precipitation for peptides (actually small proteins; e.g3-4 kDa)? Could you provide references or share your personal experiences?... Although it is a versatile approach for protein isolation, can it also be applicable for peptides, and what are the pros & cons?
Thanks in advance...Emir
I worked with proteins and modulated their isoelectric points (PMID: 29192764).
Proteins may have their lowest solubility at their pI, but this does not mean that they have zero or close-to-zero solubility. They can still remain soluble while having a net zero charge. For ex, tetra- or penta-glycine should have zero charge but still have enough solubility at pH7.
Unlike crystallization, isoelectric precipitation is a very crude and rapid process where proteins form aggregates. During this process, it is possible that other proteins with similar structures (or those which interact with the precipitating protein) can co-precipitate. I have performed repeated precipitation-dissolution cycles with insulin variants (~6000 Da) hoping to purify them from native insulin, but they always contained significant amount of native insulin impurity.
Pros: Cheap, quick
Cons: Not all proteins/peptides crash out of solution, does not yield pure proteins
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