The isoelectric point, pI, is defined as the pH of an aqueous solution of an amino acid at which the amino acids in the solution carry zero net charge. This will be explained further in the examples section. For amino acids having a charged or ionizable side chain, the pI value is calculated by taking a mean of the pKas’ of similarly ionizable groups. PKa2 –pKa of the amino group of the amino acidįor amino acids having a neutral side chain, the pI value is calculated by taking a mean of the pKa of the carboxylate and the pKa of the aminonium group. PKa1 – pKa of the carboxylate group of amino acid The isoelectric point formula for an amino acid having a neutral side chain will be as follows: The positively charged ammonium balances the negative charge of the carboxylate. The carboxyl group loses its hydrogen that is taken up by the amino group to form ammonium. At a neutral pH, an acid-base reaction occurs between the carboxyl group and the amino group of the amino acid. Amino acids interact intramolecularly to form zwitterions. At this pH, the aminoacids show minimum solubility. In an aqueous solution having a pH equal to the isoelectric point, most amino acids are present in the solution as zwitterions. The two opposite charges cancel out giving the zwitterion a net charge of zero. The zwitterion is the electrically neutral form of amino acid, that carries a negatively charged carboxylate group (CO2 –) and a positively charged amino group (NH3+ ). An aminoacid carrying no net charge is called a zwitterion. The isoelectric point is the pH of a solution at which an amino acid or peptide is neutral and carries zero net electric charge. This article will explain what is the isoelectric point, the formula used to calculate isoelectric point, and examples to demonstrate how the formula may be applied. For instance, in isoelectric focusing, a pH gradient is used to separate proteins based on their isoelectric points. The isoelectric point of proteins plays a significant role in the separation and purification methods used to isolate proteins from a solution. The pI value helps you determine the solubility of a molecule at a given pH. The isoelectric point is the pH at which the net electrical charge on a molecule is zero. An understanding of how to calculate isoelectric point is essential when you are working with proteins.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |