Protein property calculator: molecular weight, pI, GRAVY and more
Paste a protein sequence and Aaron's Archive calculates its molecular weight, isoelectric point (pI), GRAVY hydropathy, aromaticity, instability index, aliphatic index, extinction coefficient and charge at pH 7. It also draws the amino acid composition, a hydrophobicity profile, a charge-versus-pH curve and flags possible transmembrane helices and a signal peptide.
What you get
- Molecular weight, pI, GRAVY, aromaticity, instability index and aliphatic index
- Extinction coefficient (reduced, and with disulfide bonds) and net charge at pH 7
- Amino acid composition and a secondary-structure propensity estimate
- Hydrophobicity and charge profiles along the sequence, and charge versus pH
- Possible transmembrane helices and a signal peptide
How to use it
- Open the Single tab and paste a protein sequence.
- Leave the type on Auto or choose Protein.
- Press Run analysis and read the protein properties.
Worked example
Click KRAS protein in the examples, which loads this 40-residue sequence:
MTEYKLVVVGAGGVGKSALTIQLIQNHFVDEYDPTIEDSYThe tool reports a molecular weight of 4,401.9 Da, pI 4.29, GRAVY 0.022, aromaticity 10.0%, instability index 26.5, aliphatic index 99.75, net charge −4.41 at pH 7, and an extinction coefficient of 4,470 M⁻¹cm⁻¹.
Limits to know about
- Unknown residues such as X are skipped, and the result says what share of the sequence they make up.
- These are calculated from the sequence alone. They are estimates, not measurements.
Common questions
What does GRAVY mean?
The grand average of hydropathy: the mean hydropathy of the residues. Positive values lean hydrophobic and negative values lean hydrophilic. The protein properties guide covers each measure.
What is the isoelectric point?
The pH at which the protein carries no net charge. It helps when planning ion-exchange or electrophoresis.
What does an instability index above 40 mean?
It is a rule of thumb that the protein may be unstable in a test tube. It is a prediction from composition, not a measurement.
Are my sequences stored?
No. Sequences are processed in memory to produce your result and are not stored or logged. The privacy policy has the details, including what BLAST sends to NCBI and EMBL-EBI.