Why lyophilised powder is stable
The chemical reactions that break a peptide down (hydrolysis of the backbone, deamidation of asparagine and glutamine, oxidation of methionine, cysteine and tryptophan) all need water, and most of them run faster with heat and light. A lyophilised vial contains very little free water, so at −20°C in the dark these reactions are slowed to the point where the powder is stable for years. The same vial in solution at room temperature on a bench may lose measurable purity in days to weeks, depending on the sequence.
Storage by form
| Form | Temperature | Light | Typical horizon |
|---|---|---|---|
| Lyophilised, sealed | −20°C | Dark | Years |
| Lyophilised, sealed | 2–8°C | Dark | Months |
| Lyophilised, in transit | Ambient, days | Boxed | No meaningful loss |
| Reconstituted in bacteriostatic water | 2–8°C | Dark | Up to 28 days by convention; sequence-dependent |
| Reconstituted in sterile water | 2–8°C | Dark | Days; use promptly |
| Reconstituted, aliquoted and frozen | −20°C | Dark | Weeks to months; one thaw only |
| Bacteriostatic water, unopened | Room temperature | Boxed | Printed expiry |
| Bacteriostatic water, opened | Room temperature | Boxed | 28 days after first puncture |
The 28-day figures come from the multi-dose vial convention in pharmacy practice (USP General Chapter 797 assigns a 28-day beyond-use date to an opened multi-dose container unless the manufacturer states otherwise). They are a limit on the preservative, not a guarantee about any particular peptide's chemistry, which is why the peptide row says "sequence-dependent".
Which peptides degrade first
- Methionine, cysteine, tryptophan oxidise, and the reaction is driven by light and dissolved oxygen. Semax contains a methionine at its N-terminus and is the clearest example in our catalog; keep it dark.
- Asparagine and glutamine deamidate in solution, faster at neutral-to-alkaline pH. Most solutions in plain water sit near neutral.
- Aspartate–proline bonds cleave under acidic conditions.
- Long, hydrophobic sequences such as the acylated GLP-1 family compounds can aggregate when repeatedly warmed and cooled, which shows up as cloudiness or particulates rather than as a chemistry change.
- GHK-Cu is a copper complex. Its blue colour is the complex itself; a solution that loses colour has lost the copper coordination, so keep it away from chelating buffers and reducing agents.
Freeze–thaw
Every freeze–thaw cycle concentrates solutes at the ice front and stresses the peptide. One cycle is usually harmless; ten are not. If a solution has to be kept longer than a refrigerator allows, split it into single-use aliquots before freezing so that each is thawed exactly once.
Light
Ultraviolet and blue light photo-oxidise tryptophan and tyrosine and accelerate methionine oxidation. Amber vials, a closed box, or simply the inside of a refrigerator all solve this. Do not leave clear vials on a bench under lab lighting.
What "stable in transit" means
Lyophilised powder does not need refrigeration to travel. A few days at ambient temperature in a parcel has no measurable effect on a sealed lyophilised vial; that is the whole reason the material is freeze-dried before shipping. Our orders leave Nashville at room temperature without ice packs, and vials should go into a −20°C freezer on arrival. Details are on the shipping page.
How we store stock
Lyophilised stock is held at −20°C, protected from light, in the sealed lot-numbered vials it arrived in. Nothing is repackaged or re-lotted. The full handling policy is on the quality and handling page.