Peptide solubility calculator
Paste a sequence to see its charge class at pH 7, how hydrophobic it is, which solvents to try in what order, and which residues need extra care in solution.
Load a known peptide
| Peptide | Sequence | Modifications | Charge, pH 7 | Class | Load preset |
|---|---|---|---|---|---|
| BPC-157 | GEPPPGKPADDAGLV | — | -2.02 | Acidic | |
| GHK (GHK-Cu without copper) | GHK | — | +1.22 | Short | |
| Epitalon | AEDG | — | -2.02 | Short | |
| KPV | KPV | — | +0.98 | Short | |
| Selank | TKPRPGP | — | +1.98 | Basic | |
| Semax | MEHFPGP | — | -0.78 | Acidic | |
| DSIP | WAGGDASGE | — | -2.02 | Acidic | |
| Cartalax | AED | — | -2.02 | Short | |
| Thymosin Alpha-1 | SDAAVDTSSEITTKDLKEKKEVVEEAEN | N-acetyl | -5.99 | Acidic | |
| Oxytocin | CYIQNCPLG | C-amide, 1 disulfide | +0.97 | Basic | |
| Kisspeptin-10 | YNWNSFGLRF | C-amide | +1.97 | Basic | |
| Sermorelin | YADAIFTNSYRKVLGQLSARKLLQDIMSR | C-amide | +3.98 | Basic | |
| AOD-9604 | YLRIVQCRSVEGSCGF | 1 disulfide | +0.98 | Basic | |
| MOTS-c | MRWQEMGYIFYPRKLR | — | +2.98 | Basic | |
| VIP | HSDAVFTDNYTRLRKQMAVKKYLNSILN | C-amide | +4.22 | Basic | |
| LL-37 | LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES | — | +5.98 | Basic | |
| TB-500 fragment (Ac-LKKTETQ) | LKKTETQ | N-acetyl | 0.00 | Neutral |
How the advice is chosen
Solubility follows charge and hydrophobicity. The calculator finds the net charge at pH 7 (EMBOSS pKa values) and the share of hydrophobic residues (Ala, Phe, Ile, Leu, Met, Val, Trp, Tyr), then sorts the sequence into one of five classes. Each class has a first solvent to try and a next step if that fails. It is a starting order for a small test portion, not a prediction for a specific lot.
| Class | First step |
|---|---|
| Short peptide (5 residues or fewer) | Try sterile water first. Peptides this short usually dissolve readily. |
| Basic: net positive at pH 7 | Try sterile water first. |
| Acidic: net negative at pH 7 | Try sterile water or a neutral buffer such as PBS first. |
| Neutral at pH 7 | Water alone often fails. Dissolve in a minimal volume of organic solvent first: DMSO, or DMF or acetonitrile if the sequence has Met or a free Cys. |
| Hydrophobic: more than half hydrophobic residues | Dissolve in a minimal volume of organic solvent first: DMSO, or DMF or acetonitrile if the sequence has Met or a free Cys. |
Good practice for any peptide
- Test a small portion of the lot first; step to the next solvent only if needed.
- Let the vial reach room temperature before opening so moisture does not condense on the powder.
- Brief sonication helps; centrifuge before use to pellet anything undissolved.
- Store solutions as single-use aliquots, frozen, and avoid repeated freeze-thaw cycles.
See lyophilized peptide storage for handling the dry powder, and the isoelectric point calculator for the full charge curve.
Questions
How do you predict whether a peptide will dissolve in water?
Start with its net charge at neutral pH and its share of hydrophobic residues. Charged peptides usually dissolve in water or dilute acid or base; neutral or highly hydrophobic ones usually need a small volume of organic solvent first. Peptides of five residues or fewer usually dissolve in water.
Why is a peptide least soluble near its isoelectric point?
At the pI the molecules carry no net charge, so they repel each other least and aggregate most. Moving the pH a unit or two away from the pI usually helps.
Which peptides need care with DMSO?
DMSO can oxidize methionine and free cysteine. For sequences that contain them, DMF or acetonitrile are the usual alternatives.
What is GRAVY?
The grand average of hydropathy: the mean Kyte–Doolittle score across the sequence. Positive values mean hydrophobic, negative values hydrophilic. It is a rough guide; charge at the working pH usually matters more for short peptides.
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Reference tools for laboratory research. Not for human or animal use.