Chemistry

Isoelectric Point Calculator

Find the pI from two pKa values.

Calculated Output

Isoelectric point (pI) 6.015

Formula: pI = (pKa₁ + pKa₂) ÷ 2

Step-by-Step Breakdown

1. Values used:

2. pKa (carboxyl/acidic) = 2.34

3. pKa (amino/basic) = 9.69

5. Isoelectric point (pI) = 6.015

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The math behind it

For a simple amino acid, pI = average of the two relevant pKa values.

Glycine: (2.34 + 9.69) ÷ 2 → 6.02.

Side chains?

Acidic/basic side chains add a third pKa; average the two flanking the neutral form.