Isoelectric Point Calculator

Calculate the theoretical isoelectric point (pI) of protein sequences.

What is Isoelectric Point?

The isoelectric point (pI) is the pH at which a protein carries no net electrical charge. At this pH, the protein is least soluble and will not migrate in an electric field.

How It Works

The pI is calculated using the Henderson-Hasselbalch equation, considering the pKa values of ionizable amino acid side chains (Asp, Glu, His, Cys, Tyr, Lys, Arg) and the N- and C-termini.

Input

• Protein sequences: Enter one or more protein sequences in FASTA format
• Supports batch processing of multiple sequences

Output

• Protein ID: Identifier from FASTA header
• Number of Amino Acids: Sequence length
• Isoelectric Point: Theoretical pI value

Use Cases

• Design protein purification strategies
• Predict protein behavior in electrophoresis
• Buffer selection for protein handling
• Isoelectric focusing experiments