01 /Why storage matters
Peptides are more sensitive to temperature, moisture, oxygen, and light than most small molecule reagents. Poor storage is the most common reason research peptide stability falls short of the manufacturer's stated shelf life. The good news: storage is the variable researchers control most directly, so getting it right is the highest leverage stability move available.
Stability failures show up as loss of activity in assay, formation of soluble or insoluble degradation products, color change, or in extreme cases visible precipitation in solution. Most failures are invisible until the experiment runs.
02 /Lyophilized (powder) storage
Apothify ships lyophilized peptides. Lyophilized means freeze dried under vacuum into a fluffy white cake or powder. In this form, peptides are at their most stable because there is essentially no water available to drive hydrolysis reactions.
The standard storage recommendation is sealed, in original packaging, with desiccant, at minus 20 Celsius, protected from light. Stored this way, lyophilized peptides are generally stable for the timeframes on the COA, typically 24 months or longer.
If your freezer cannot hold minus 20, a household freezer at minus 10 to minus 15 is acceptable for short term storage (under 6 months). Refrigeration at 4 Celsius is acceptable for very short term storage (under 4 weeks). Room temperature storage is acceptable only for the duration of shipping (under 5 business days).
03 /Avoid freeze thaw cycles
Every freeze thaw cycle slightly degrades the peptide. Three or four cycles are typically fine. Twenty are not. The mechanism is mechanical (ice crystal formation) plus chemical (concentrated salt and pH effects during freezing).
To avoid cycles, aliquot the lyophilized peptide on first opening if you anticipate intermittent use. Or reconstitute the full vial once and aliquot the solution into single use volumes before any are frozen.
04 /Reconstitution: choice of solvent
The standard reconstitution solvent for research peptides is bacteriostatic water (sterile water with 0.9 percent benzyl alcohol as a bacteriostat). For peptides with low aqueous solubility, options include sterile saline, acetic acid solution (5 to 10 millimolar), or dimethyl sulfoxide (DMSO) followed by dilution into aqueous buffer.
Match the solvent to the peptide. A general rule: hydrophilic peptides (rich in charged residues like lysine, arginine, glutamate, aspartate) dissolve easily in water. Hydrophobic peptides (rich in tryptophan, phenylalanine, valine, leucine) may need acid or DMSO. The peptide supplier should provide a solubility note; if not, start with water and try acid as a second option.
05 /Reconstituted (solution) storage
Once reconstituted, peptides are much less stable. Most are stored at 4 Celsius and used within a short window per the laboratory's own validation. A typical conservative window is one to two weeks at 4 Celsius. Some peptides tolerate four weeks; others degrade noticeably in seven days.
Freezing a reconstituted peptide at minus 20 Celsius slows degradation substantially. Freezing at minus 80 Celsius slows it further. If you need a peptide solution for a study spanning more than two weeks, prepare in advance, aliquot into single use volumes, and freeze. Thaw one aliquot at a time and never refreeze.
Glass vials are slightly better than plastic for long term storage. Some peptides adsorb to plastic walls (especially polypropylene), which both depletes the solution concentration and complicates analytical work.
06 /Light, oxygen, and pH
Peptides with tryptophan, tyrosine, or methionine residues are sensitive to oxidation. Store them away from light and minimize air exposure during pipetting (use the smallest available vial, do not leave the cap off, do not vortex in open headspace).
Cysteine containing peptides form disulfide bonds with each other in solution. For monomer stability, reconstitute under nitrogen if possible and use within hours rather than days.
pH matters. Most peptides are most stable around pH 4 to 6 (slightly acidic). Strongly alkaline solutions (above pH 8) accelerate degradation, especially for peptides with asparagine or glutamine residues that can deamidate.
07 /Shipping and receipt
Apothify ships USPS Priority Mail by default. UPS 2 Day Air and UPS Next Day Air are available at checkout. Shipping at ambient temperature is acceptable for lyophilized peptides over 1 to 5 business days. Cold pack shipping is available on request and recommended for orders shipping in summer to addresses where high heat exposure during transit is likely.
On receipt, inspect the package immediately. Vials should be intact, the lyophilized cake should look white and fluffy (not melted or wet), and the desiccant if present should be dry. Transfer to your laboratory freezer as soon as possible. Apothify is not responsible for stability changes caused by post delivery storage. The window for damage and incorrect item claims is 72 hours from delivery scan, per the refund policy.
08 /Common stability failure modes
Discoloration. A lyophilized peptide that turns yellow has typically oxidized. Discard.
Soluble aggregates. A reconstituted peptide that looks cloudy at low concentration but clear at high concentration has formed soluble aggregates and is unlikely to be useful.
Insoluble precipitate. White flakes or particles in solution mean precipitation. May be recoverable by warming briefly to 37 Celsius and gentle inversion (not shaking). If precipitate persists, discard.
Loss of activity without visible change. The most common and the hardest to catch. The only protection is a fresh aliquot baseline at the start of each new experimental block.
09 /When in doubt, reorder
Research peptides are cheap compared to a failed experiment. If you have any doubt about the stability of a vial that has been in your freezer for over a year, order a fresh batch. The cost is a few dozen dollars; the cost of a failed paper is months.
