Peptide tools
Peptide calculator.
Paste a sequence to get its mass, formula and isoelectric point, and see how hard it is likely to be to make by solid-phase synthesis.
Monoisotopic massDa
Average massg/mol
Formula
Lengthresidues
Isoelectric point (pI)
Net charge at pH 7
GRAVYKyte–Doolittle
Extinction coefficient
Synthesis complexity
–/ 100
Enter a sequence
The score combines length, hydrophobicity, aggregation, beta-sheet propensity and known sequence liabilities.
Sequence map
Highlighted: aggregation-prone liability
Net charge vs pH
Dashed line marks pH 7. The curve crosses zero at the pI.
Watch-outs and suggestions
Expected ions for LC-MS
Monoisotopic m/z for protonated ions.
How it works
Methods and limits.
These are screening estimates for linear peptides of the 20 standard amino acids. Real behaviour also depends on resin, protecting groups and conditions, so our chemists review every sequence before quoting.
- Mass and formula from elemental compositions, including termini and disulfides (−2 H each).
- pI and charge from the Henderson–Hasselbalch equation with the EMBOSS pKa set. Bridged cysteines are not counted.
- Hydrophobicity as GRAVY (Kyte–Doolittle) and the share of A, V, I, L, M, F and W.
- Aggregation-prone regions are 5-residue windows, with no Pro, that are both hydrophobic (mean hydropathy ≥ 1.2) and beta-prone (mean Chou–Fasman Pβ ≥ 1.1).
- Liabilities include aspartimide motifs, Cys, Met and Trp oxidation, pyroglutamate, diketopiperazine, repeats and beta-branched runs.
- Extinction coefficient at 280 nm from Trp (5,500), Tyr (1,490) and cystine (125).
Difficult sequence?
Send it to our chemists for a free synthesis assessment and route recommendation.