2. Peptides
  3. Peptide Solubility and Storage Guidelines

Peptide Solubility and Storage Guidelines

1.  The solubility of peptides depends on the sequence and modifications. It is recommended to take a small amount and perform solubility test before dissolving all peptides.

2.  Calculate the length of the peptide. Generally, for those less than 6 amino acids, peptide can dissolve in 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.

3.  Calculate the overall charge of the entire peptide according to the following table:

  Contents Assign value
Acidic amino acid Asp (D), Glu (E), and the C-terminal -COOH. -1
Basic amino acid Arg (R), Lys (K), His (H), and the N-terminal -NH2 +1
Neutral amino acid Gly (G), Ala (A), Leu (L), Ile (I), Val (V), Cys (C), Met (M), Thr (T), Ser (S), Phe (F), Tyr (Y), Trp (W), Pro (P), Asn (N), Gln (Q) 0

4.  Recommended solution.

Overall charge of peptide Details
Negative (<0) 1.  Try to dissolve the peptide in water first.
2.  If water fails, add NH4OH (<50 μL).
3.  If the peptide still does not dissolve, add DMSO (50-100 μL) to solubilize the peptide.
Positive (>0) 1.  Try to dissolve the peptide in water first.
2.  If water fails, try dissolving the peptide in a 10%-30% acetic acid solution.
3.  If the peptide still does not dissolve, try dissolving the peptide in a small amount of DMSO.
Zero (=0) 1.  Try to dissolve the peptide in organic solvent (acetonitrile, methanol, etc.) first.
2.  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.
Note:

1.  It is recommended that the concentration of the stock solution be around 1-2 mg/mL.

2.  Lyophilized peptides can be stored at -20°C. Solution of peptide should be divided into aliquots and stored at -20°C (or preferably -80°C). Keep away from bright light. Avoid repeated freeze-thaw cycles.

3.  Peptides that contain Met, Cys, or Trp residues should be stored in an oxygen-free atmosphere to avoid oxidation.

4.  Peptides containing Asp, Glu, Lys, Arg, or His are prone to moisture absorption from the air, called deliquescence. These peptides should be stored in a dessicator in a tightly capped vial.