kp calculator
Calculate Isoelectric Point (pI)
Use single letter codes (A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y, V)
About Isoelectric Point
The isoelectric point (pI) is the pH at which a molecule carries no net electrical charge. For amino acids and proteins, it's calculated as the average of the two pKa values that bracket the neutral charge state.
pI = (pKa₁ + pKa₂) / 2
For amino acids with ionizable side chains:
pI = (pKa₁ + pKa₂ + pKa₃) / 3
The pI is important in protein purification, electrophoresis, and understanding protein behavior in different pH environments.