Solubility FAQ¶
1. What solvents are recommended for peptide reconstitution?¶
| Solvent | Best For | Notes |
|---|---|---|
| Sterile Water for Injection (WFI) | Most hydrophilic peptides | pH ~5–7, first choice for most peptides |
| PBS (pH 7.4) | Cell-based assays | Buffered, physiological pH |
| 0.9% Saline | General research use | Isotonic |
| 0.1% Acetic Acid | Hydrophobic/basic peptides | Improves solubility for basic peptides |
| DMSO (≤0.1% final) | Highly hydrophobic peptides | Avoid >0.1% in cell assays |
2. What is the typical solubility of research peptides?¶
Solubility is highly sequence-dependent. Most peptides dissolve at 1–10 mg/mL in WFI or PBS. Hydrophobic peptides or those with high β-sheet propensity may require acidic conditions or co-solvents.
3. How do I calculate the final concentration?¶
Concentration (mg/mL) = Mass of peptide (mg) / Volume of solvent (mL)
For molar concentration: Molarity (M) = Concentration (mg/mL) / Molecular Weight (g/mol)
Example: 5 mg peptide with MW 1500 g/mol dissolved in 2.5 mL of WFI: - Concentration = 5 / 2.5 = 2 mg/mL - Molarity = 2 / 1500 = 0.00133 M = 1.33 mM
4. What if the peptide doesn't dissolve?¶
Try these steps in order: 1. Allow more time (15–30 min with gentle swirling) 2. Warm to 25°C (do not exceed 37°C) 3. Sonicate in a water bath (30 seconds, avoid foaming) 4. Add a small volume of 0.1% acetic acid or DMSO 5. Adjust pH (use 0.1 M HCl or NaOH in small increments)
5. Can I use DMSO as the primary solvent?¶
DMSO is effective for hydrophobic peptides but should be used with caution. Final DMSO concentration in cell-based assays should not exceed 0.1%. For stock solutions in DMSO, prepare at 1000× the final assay concentration.
6. How does pH affect solubility?¶
Peptides are most soluble at a pH away from their isoelectric point (pI). For basic peptides (pI > 7), slightly acidic conditions improve solubility. For acidic peptides (pI < 7), slightly basic conditions are preferred.
For solubility inquiries: [email protected]