Solubility Tips

Reconstituting a Peptide

  • Bring frozen or refrigerated peptides to room temperature in a desiccated chamber to avoid water absorption.
  • Always begin by reconstituting a small amount of peptide before committing the entire lot.
  • Use sterile water or sterile filtration.  If there are any Methionine (M), Cysteine (C), or Tryptophan (W) residues, use oxygen free solvents to prevent oxidation. 
  • Avoid reconstituting a peptide in a buffer, such as PBS.  Salts hinder solubility.
  • Choose the appropriate solvent.  Begin reconstituting at a concentration higher than your desired final working concentration.


Amino Acid Characteristics

Recommended Solvent

Hydrophilic residues (KRHDEN)


Hydrophobic residues (AVLIMFW)

Low solubility in aqueous solvents; are soluble in organic solvents (DMF, DMSO, TFA, Acetonitrile)


  • A solubilized peptide is completely clear. No flecks or cloudiness should be present.
  • If a peptide with more hydrophilic residues is still not completely reconstituted:
    • Adjust the pH of the solution according to the overall charge of the peptide
      • Count the possible POSITIVE charges (K, R, H, and free N-terminus)
      • Count the possible NEGATIVE charges (D, E, and free C-terminus)
      • Determine which is greater.
        • If positive charges are greater, add dilute acid dropwise to proteinate residues and maximize charge.
        • If negative charges are greater, add dilute base dropwise to deproteinate and maximize charge.
        • try sonication, gentle heat or an organic solvent, such as DMSO, Acetonitrile or DMF.

If your peptide is still not completely reconstituted, lyophilize the peptide and begin again.

Please contact NEP Technical Service for assistance, should you have difficulty with these recommendations.


"I had been working with a different peptide company for custom peptides…but ran into a spate of problems – lost orders, huge delays, and bad technical help. So we switched to NEP. After that, everything has gone swimmingly. Pricing, honestly, is a bit more than I was paying before, but as with many other things in life, you get what you pay for!"
Kirk F. PhD