Question

How to choose the buffer accprding to the ph of thr protein?

Answer 1

Indeed, when the pH buffer is equal to the pI (isoelectric point), the protein has no charge. Consequently, the protein is not able to bind to an ion exchange column (anion and cation). Adjusting the pH below or above the protein pI induces a positive charge when pH < pI and a negative charge when pH > pI (Fig.1).