Peptide Dissolution and Storage
  • Peptide Dissolution

    The appropriate dissolution method for peptide is an significant factor for the success of biochemical experiment. Improper dissolution will cause the loss of peptide and the failure of experiment.Before peptide dissolution, it is recommended that you test the optimal dissolution method with a small amount of peptide. Only when the peptide is completely dissolved can you add water or buffer to dilute it to the final concentration.

     

    Calculate the charge number of the whole peptide chain.Each acidic amino acid is defined as - 1,include Asp,Glu,and -COOH from C-terminal ;Each alkaline amino acid is defined as + 1, including Arg, Lys, His and -NH2 from N-terminal.The result is alkaline peptide if total score is positive,acidic peptide for negative.Neutral peptide for zero total.


    Alkaline peptide      1.Distilled water

                                   2.10% - 25% acetic acid                     

                                   3.TFA(10-50μL) or 50% acetic acid            

                       

    Acidic peptide         1.Distilled water                           Dilute to the required

                                   2.PBS (PH7.4)                               concentration

                                   3.NH4HCO/NH4OH    

                          

    Neutral peptide       1.Acetonitrile/methanol/isopropanol            

                                   2.DMSO (Hydrophobic peptide)       

     

    Considerations

     

    1.Firstly dissolve the peptide into a higher concentration with sterile water or acetic acid (0.1%) as the storage solution rather than directly diluting it to the detection concentration.Then buffer this storage solution to the required concentration when you need test .

     

    2.Peptides with less than 5 amino acids are generally soluble in aqueous solution, except for highly hydrophobic amino acids.  

     

    3.Hydrophobic peptide:Peptides with hydrophobic amino acid content > 50% are generally insoluble in aqueous solution.It is better to dissolve the peptide in a small amount of strong organic solvents such as DMF, ACN, isopropanol, ethanol, acetic acid, 6M guanidine•HCl, 8M urea, or DMSO ,Then the organic solvent which dissolves the peptide is slowly added into the aqueous solution .

     

    4.Ultrasound: ultrasound can only accelerate the dissolution of peptide, can not improve the solubility of them.

     

    Properties of amino acids
    AlkalineArg,His,Lys
    AcidicAsp,Glu
    HydrophobicTry,Phe,Val,Leu,Ile,Ala,Met


    Peptide Preservation

     

    1. Peptides in the form of lyophilized powder provided by aurora can be stably transported under normal temperature through sealed packaging.Peptides requiring long-term preservation shall be stored in a sealed container containing desiccant in the form of lyophilized powder and stored at a temperature below - 20 centigrade, which can avoid peptide degradation, bacterial degradation and oxidation, and the formation of secondary structure of peptide.

     

    2. The peptide has hygroscopicity. Before opening the package or weighing, please balance the peptide in the desiccator to room temperature to avoid the water absorption.Then can unfold the vial to weigh the peptide.

     

    3. The dissolved peptide is much more unstable than the lyophilized form.The peptide in the form of solution should be dissolved in the sterile water of pH 5-7(or filter with 0.2 μ m membrane) and stored at - 20 centigrade.Stored in small amount respectively to avoid repeated freezing and dissolve of them.

     

    4. Peptides containing Cys, Met or Trp are easy to oxidize. Before peptide sealing, we will add nitrogen or argon to reduce its effection of oxidation. Therefore, deoxidizing buffer is essential for dissolution.