Protein Isoelectric Point
How to calculate the isoelectric point of a protein
- Paste one or more protein sequences, as plain text or FASTA.
- The isoelectric point appears for each sequence.
- Change the pH to see the net charge of the protein at that pH.
Frequently asked questions
How is the pI calculated?
The charge of the ends and of each D, E, C, Y, H, K and R is added up from its pKa, and the pH where the total is zero is found by bisection. The pKa values are those used by EMBOSS.
Why is it different from other calculators?
Each calculator uses its own set of pKa values, so results often differ by a few tenths of a pH unit. None of them accounts for folding or modifications.
Is my sequence uploaded?
No. Everything runs in your browser, so your sequences never leave your device.
More DNA and protein sequence tools
Reverse ComplementDNA to RNACombine FASTA SequencesSplit FASTA SequenceGenBank to FASTAEMBL to FASTAGenBank Feature ExtractorEMBL Feature ExtractorGenBank Translation ExtractorEMBL Translation ExtractorSplit CodonsRange Extractor DNARange Extractor ProteinWindow Extractor DNAWindow Extractor ProteinFilter DNAFilter ProteinGroup DNAGroup ProteinOne-Letter to Three-Letter Amino AcidsThree-Letter to One-Letter Amino AcidsDNA StatisticsProtein StatisticsCodon UsageCpG Island FinderDNA Molecular WeightProtein Molecular WeightProtein GRAVYDNA Pattern FindProtein Pattern FindFuzzy Search DNAFuzzy Search ProteinIdentity and SimilarityORF FinderTranslate DNA to ProteinReverse TranslateReverse Translate a Protein AlignmentPCR Primer StatsPCR ProductsRestriction SummaryMutate for DigestPairwise Align DNAPairwise Align ProteinPairwise Align CodonsRestriction MapTranslation MapPrimer MapColor Alignment by ConservationColor Alignment by PropertiesCodon PlotRandom DNA SequenceRandom Protein SequenceRandom Coding DNARandom DNA RegionsRandom Protein RegionsSample DNASample ProteinShuffle DNAShuffle ProteinMutate DNAMutate ProteinGenetic CodesIUPAC Codes