Peptide analyser
Mass, isoelectric point, extinction coefficient and composition from a sequence.
FASTA headers, whitespace, digits and lower case are all fine. Ambiguity codes are not — they have no single mass or pKa.
Match this one when you need to agree with ExPASy Compute pI/Mw, which most published pI values are quoted from.
The 280 nm coefficient counts disulfide bonds, not cysteines.
Length
Average mass
Isoelectric point
C409H619N105O108S2 · monoisotopic 8793.5614 · GRAVY -0.004 · aliphatic index 88.4
Net charge against pH
+0.358net charge
Absorbance at 280 nm
ε = 8480 M⁻¹cm⁻¹ · A(1 mg/mL, 1 cm) = 0.9637
Enter a reading
Composition · 20 of 20 present
- A Ala79.33%
- R Arg45.33%
- N Asn22.67%
- D Asp34%
- C Cys11.33%
- Q Gln34%
- E Glu68%
- G Gly22.67%
- H His34%
- I Ile22.67%
- L Leu810.7%
- K Lys68%
- M Met11.33%
- F Phe912%
- P Pro11.33%
- S Ser56.67%
- T Thr22.67%
- W Trp11.33%
- Y Tyr22.67%
- V Val79.33%
M = Σ residues + H₂O; ε₂₈₀ = 5500·nW + 1490·nY + 125·nSS; pI where Σq(pH) = 0- Extinction coefficient at 280 nm from sequence — Analytical Biochemistry, 1989
- Bjellqvist pKa set, as used by ExPASy Compute pI/Mw — Electrophoresis, 1993
- Hydropathy scale used for GRAVY — Journal of Molecular Biology, 1982
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Masses use IUPAC atomic weights and may differ from a supplier’s last digit. The extinction coefficient is for the denatured protein in water; a folded protein in buffer typically reads a few per cent lower.
About this tool
Compute molecular weight, monoisotopic mass, isoelectric point, net charge, the 280 nm extinction coefficient and amino acid composition for a protein or peptide. The pKa set and the cysteine state are yours to choose, because both change the answer.
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Science last reviewed .