Isoelectric Point (pI)
Isoelectric Point (pI) — The pH at which a peptide carries no net electrical charge. At the pI, peptides have minimum solubility and are most susceptible to precipitation.
What Is the Isoelectric Point?
The isoelectric point (pI) is the pH at which a peptide carries no net electrical charge. At the pI, the positive charges from Arg, Lys, His, and the N-terminus exactly balance the negative charges from Asp, Glu, Cys, Tyr, and the C-terminus. At the pI, peptide solubility is at its minimum, and aggregation tendency is at its maximum.
Practical Applications
- Formulation: Buffer pH should be at least 2 units away from pI to maintain solubility and charge-based repulsion
- IEX: pI determines whether a peptide binds to cation (pH < pI) or anion (pH > pI) exchange columns
- Isoelectric focusing: Separates peptide charge variants for deamidation analysis
Frequently Asked Questions
What is Isoelectric Point (pI)?
The pH at which a peptide carries no net electrical charge. At the pI, peptides have minimum solubility and are most susceptible to precipitation.
Why is Isoelectric Point (pI) important in peptide research?
Isoelectric Point (pI) is a fundamental concept in chemistry as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.
Authority Sources
- Isoelectric Point (pI) on Wikipedia
- Search Isoelectric Point (pI) on PubChem (NIH)
- Research articles on ScienceDirect