Protein isoelectric point calculator

Isoelectric point, the pH at which a particular molecule carries no net electrical charge, is an critical parameter for many analytical biochemistry and proteomics techniques, especially for 2D gel electrophoresis (2D-PAGE), capillary isoelectric focusing (cIEF), X-ray crystallography and liquid chromatography–mass spectrometry (LC-MS)

Below is the text area where you can paste amino acid sequence of analyzed protein (peptide) or multiple sequences in fasta format

  • Input should be ONE sequence in plain text or MULTIPLE sequences in FASTA format (limit is set to 50,000 chars)
  • Input should be in one letter amino acid code, input can be upper or lower case.
  • All non-amino acid characters will be removed from the sequence.
  • For big datasets use standalone version or split your input into 50k chunks.
Input example: for Ala-Pro-Lys-His-Ala-Tyr peptide, please enter APKHAY
Standalone version of the program
IPC in Python
(command line, any OS)

Available also as PyPi package (pip install isoelectric)

Reference: Kozlowski LP (2016) IPC - Isoelectric Point Calculator. Biology Direct 11:55.

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License: IPC is public domain, for details see license
IPC website mirrors: Mirror 1 Mirror 2

If you are interested in high-throughput analysis of isoelectric points for whole organisms you might want to check this database:
Proteome-pI - Proteome Isoelectric Point Database - predicted isoelectric point for ~21 million proteins across 5,029 organisms

Contact: Lukasz P. Kozlowski