Peptide Solubility Guidelines
How to dissolve your peptide
Proper peptide solubilization is one of the most important factors in a successful peptide assay. Improper peptide solubilization results in inaccurate peptide concentration calculations, which can introduce experimental error into data or result in experimental failure. However, finding the ideal solvent in which to dissolve your peptide is often a challenge. The steps outlined below guide you through the process for determining the best solvent for maximum solubility of your custom peptide. It is best to test your peptide's solubility by first using a minute amount of peptide. Distilled, sterile water should be tried as a solvent first, especially when the peptide has less than five residues. For other peptides, optimum conditions for peptide solubility are based on the peptide sequence.
- Calculate the length of the peptide. Generally, for those less than 6 amino acids, peptide can dissolve in pure water. For those more than 6 amino acids, the dissolve principle is according to its overall charge of the peptide and the degree of hydrophobic.
- Assign a value of -1 to acidic residues which include Asp (D), Glu (E), and the C-terminal -COOH. Assign a value of +1 to basic residues which include Arg (R), Lys (K), His (H), and the N-terminal -NH2. Calculate the overall charge of the entire peptide.
- (Option 1-1) If the overall charge of the peptide is negative, try to dissolve the peptide in water first. (Option 1-2)If water fails, add NH4OH (< 50 μl) and then dilute the peptide solution to the desired concentration. If the peptide contains Cys, do not use NH4OH to dissolve it. Try the alternative method listed below. (Option 1-3) If the peptide still does not dissolve, add DMSO (50-100μl) to solubilize the peptide and then dilute the peptide solution to the desired concentration.
- (Option 2-1)If the overall charge of the peptide is positive, try dissolving the peptide in water first. (Option 2-2)If water fails, try dissolving the peptide in a 10%-30% acetic acid solution. (Option 2-3) If the peptide still does not dissolve, try dissolving the peptide in a small amount of DMSO, and then dilute the peptide solution to the desired concentration.
- Peptides having an overall charge of zero usually dissolve best in an organic solvent. First, try adding acetonitrile, methanol, etc. For very hydrophobic peptides, try dissolving the peptide in a small amount of DMSO, and then dilute the solution with water to the desired concentration. Peptides containing Cysteine (C), Methionine (M) or Tryptophan (W) are sensitive to oxidation by DMSO. We advise that peptides dissolved in DMSO be used immediately or stored at -20°C (or preferably −80°C) prior to use.
The above recommendations are schematically represented below:
Click on the bubbles that correspond to the overall charge of your peptide for guidance on how to dissolve your peptide. or Request a solubility test when you request a quote for your custom peptide (by typing 'solubility test' in the comments box) and let us make peptide solubilization easy for you.
Flowchart for Dissolving Peptides:
- a. Cys-containing peptides
- b. Very hydrophobic peptides
- c. Tend-to-aggregate peptides
- It is recommended that the concentration of the stock solution be around 1-2 mg of peptide per mL of solution. This is dilute enough so that relatively small volumes (< 100 μL ) of peptide can be used in an assay, minimizing the effect of the solvents initially used for solubilization.
- The stability of each peptide depends on its sequence information. We suggest storing lyophilized peptides at -20 °C. Once in solution we recommend that you aliquot your peptide into tubes and store at -20 °C(or preferably −80°C). It is recommended that peptides containing methionine, cysteine, or tryptophan residues be stored in an oxygen-free atmosphere to avoid oxidation.
Quotations and Ordering
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