How should I store my peptide when it is in solution?
If storage of peptides in solution is absolutely unavoidable, use sterile buffers at pH 5-6 and store aliquots at -20°C to prolong the storage life of peptides in solution.
How long can I store my peptide when it is in solution?
It is not recommended to keep excess peptides in solution. The shelf life of peptides in solution is very limited, especially for sequences containing cysteine, methionine, tryptophan, asparagine, glutamine, and N-terminal glutamic acid. In general, aliquot the necessary amounts of peptide for a few days and relyophilize remaining portions for long term storage if necessary.
Are there any recommended procedures when I am about to start working on my peptide?
When preparing the peptide for use, please observe the following steps to maintain peptide quality:
Warm up the peptide to room temperature prior to opening and weighing out portion of the peptide. The recommended time for warm up is 1 hour. In a clean environment weigh out desired quantity of peptide quickly.
Store the remaining peptide in freezer, preferably below -20°C within an enclosed case with dessicants.
Reconstitution and Storage of Peptides
Peptides are usually supplied as a fluffy, freeze-dried material in serum vials. Store peptides in a freezer after they have been received. In order to reconstitute the peptide, distilled water or a buffer solution should be utilized. Some peptides have low solubility in water and must be dissolved in other solvents such as 10% acetic acid for a positively charged peptide or 10% ammonium bicarbonate solution for a negatively charged peptide. Other solvents that can be used for dissolving peptides are acetonitrile, DMSO, DMF, or isopropanol. Use the minimal amount of these non-aqueous solvents and add water or buffer to make up the desired volume. After peptides are reconstituted, they should be used as soon as possible to avoid degradation in solution. Unused peptide should be aliquoted into single-use portions, relyophilized if possible, and stored at -20°C. Repeated thawing and refreezing should be avoided.
Methods to Dissolve Peptides
The best way to dissolve a peptide is to use water. For peptides that are not soluble in water, use the following procedure:
For acidic peptides, use a small amount of base such as 10% ammonium bicarbonate to dissolve the peptide, dilute with water to the desired concentration. Do not use base for cysteine-containing peptides.
For basic peptides, use a small amount of 30% acetic acid, dilute with water to the desired concentration.
For a very hydrophobic peptide, try dissolving the peptide in a very small amount of DMSO, dilute with water to the desired concentration.
For peptides that tend to aggregate (usually peptides containing cysteines), add 6 M urea, 6 M urea with 20% acetic acid, or 6 M guanidine•HCl to the peptide, then proceed with the necessary dilutions.