Solubility
Solubility is often one of the major challenges for researchers who work with peptides. Each amino acid exhibits its own physical characteristics. Such amino acids as leucine, isoleucine, and valine are very hydrophobic. Other amino acids such as lysine, histidine, and arginine are hydrophilic. Thus, different peptides will have different solubilities, based on the content of the peptide. As a general rule, peptides should first be dissolved in distilled, preferably sterile water. If solubility still remains a problem, try the following steps:
Sonication is helpful to dissolve the peptide.
Small amounts of dilute (10%) aqueous acetic acid (for basic peptides) or aqueous ammonia (for acidic peptides) may help dissolution of these peptides.
It is also recommended that the peptide be dissolved to the highest possible concentration, and then diluted with water or buffer to the working concentration. (Note: The buffer should be added only after the peptide is completely in solution form, because salts may cause aggregation and create further solubility problems.)
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Peptide Storage
Peptides are delivered in lyophilized form and often hydroscopic. Absorption of water will decrease stability of the peptide and may reduce overall peptide content. For best results, please note:
Maintain a dry environment and use a desiccator.
Upon arrival, always store lyophilized peptide in a freezer at -20?C for maximum stability.
Avoid using a frost-free freezer, because changes in moisture and temperature may affect peptide stability.
Short-term temperature changes that occur during shipping should not affect product life or efficacy.
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Preparation for Use
When preparing the peptide for use, please observe the following steps to maintain peptide quality:
Warm the peptide to room temperature, prior to opening and weighing out portions of the peptide.
Weigh out desired quantity of peptide quickly.
Reseal vial tightly.
Store the remaining peptide in freezer, preferably below -20?C and under dry conditions.
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Storage of Peptides 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, asparginine, glutamine, and N-terminal glutamic acid. In general, aliquot the necessary amounts of peptide for the day and relyophilize remaining portions. 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.
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Need vialing?
American Peptide Company offers our customers a vialing service to prepack the desired aliquots of your peptide. Please call customer service at 800-926-8272 for more information.
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Handle with care
The chemical, physical, and toxicological properties of research chemicals and peptides have not been fully investigated. Chemicals and peptides should be handled only by or under the direct supervision of a "technically qualified individual."
