nounIntermediate
Definition
The specific pH at which a peptide or amino acid carries zero net electrical charge, meaning the total positive charges from protonated amino groups and basic side chains exactly equal the total negative charges from deprotonated carboxyl groups and acidic side chains.
Detailed Explanation
The specific pH at which a peptide or amino acid carries zero net electrical charge, meaning the total positive charges from protonated amino groups and basic side chains exactly equal the total negative charges from deprotonated carboxyl groups and acidic side chains. At its pI, a peptide has minimum solubility and does not migrate in an electric field (electrophoresis). pI can be calculated from the pKa values of all ionizable groups and is useful for predicting peptide behavior during chromatographic purification.
Key Facts
- The specific pH at which a peptide or amino acid carries zero net electrical charge, meaning the total positive charges from protonated amino groups and basic side chains exactly equal the total negative charges from deprotonated carboxyl groups and acidic side chains.
- At its pI, a peptide has minimum solubility and does not migrate in an electric field (electrophoresis).
- pI can be calculated from the pKa values of all ionizable groups and is useful for predicting peptide behavior during chromatographic purification.
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