Isoelectric p H
Definition:
Isoelectric pH (pI) is the pH at which an amino acid or protein carries no net electrical charge - the positive and negative charges are equal.
Key point:
At pI, the molecule does not migrate in an electric field.
Examples (real data):
Glycine → pI = 6.0
Albumin → pI ≈ 4.7
Hemoglobin → pI ≈ 6.8
Formula (for simple amino acids):
Short Answer:
It is the pH at which an amino acid or protein has no net charge and does not move in an electric field.
Example: Glycine has pI ≈ 6.0.