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Peptide Storage & Handling Guidelines

Storage

Peptides will arrive as a lyophilized form. Lyophilized peptides generally have very good stability and the short-term temperature change during shipping should not affect the product quality and efficacy. However, we recommend storing the lyophilized peptides at –20 � C upon arrival and at this temperature, most lyophilizates can be stable for years without significant degradation.

Peptides are often hydroscopic. The absorption of moisture may decrease the stability and reduce the overall product quality. To avoid this, the vial should be always tightly sealed and when preparing for use, peptides should be allowed to warm to room temperature before opening the vial. We recommend that you only dissolve the needed amount into a buffer. The remainder of the stock should be stored dry at –20 � C. The majority of peptides, both acidic and basic peptides, are most stable in acidic condition. Aliquots of remaining peptide solution can be stored frozen for a short term, however, for maximal stability, we recommend re-lyophilizing the solution and re-constituting the compounds.

Solubilization

Peptide solubilization often presents a problem for the researchers. We recommend first attempting to determine the solubility by dissolving an aliquot into the buffer of choices by vortexing and sonication if necessary.

If solubility still remains a problem, following our guideline and determine the net charge of the compound may be of help. The charge of each residue of K, R, H, free N-terminal and any additional -NH₂ is set at +1; each of D, E and free C-terminal is set at   -1. For basic peptides (net charge >= 1), try to add a drop or more of glacial acetic acid (can be up to 20-30% in volume for problematic sequences) to facilitate the dissolution. For acidic peptides (net charge <= -1), 5% ammonia may be helpful for the solubilization.

For difficult hydrophobic peptide (containing high portion of A, V, M, I, Q where the net charge may or may not be 0), try to first dissolve it in an organic solvent such as DMSO and ethanol, etc. or an organic/aqueous co-solvent, then dilute the stock to the concentration and media of choices.

Note: The use of base and DMSO may promote problem for peptides containing cysteine residue with free thiol group.