Guide
Why peptides ship freeze-dried
Research peptides arrive as a white cake or powder in a sealed vial rather than as a liquid, and they arrive in an ordinary parcel rather than on ice. Both of those are deliberate, and both follow from the same piece of chemistry: what makes peptides fragile is water.
What lyophilisation is
Freeze-drying, or lyophilisation, removes water from a frozen solution without ever letting it melt. The material is frozen, the pressure is dropped, and the ice sublimes - passing straight from solid to vapour. A secondary drying stage then pulls off water still bound to the molecules.
What remains is a porous solid holding the shape of the frozen liquid, which is why it appears as a cake rather than a dense pellet. That structure matters: it has a large surface area and redissolves readily.
Why water is the problem
Peptides degrade by routes that mostly require water, or require the molecular mobility that water provides.
Hydrolysis cleaves the peptide bond, and it needs water as a reactant. Deamidation converts asparagine and glutamine side chains to acidic residues through a cyclic intermediate, and proceeds readily in solution. Oxidation affects methionine, cysteine and tryptophan. Aggregation requires molecules to move and meet.
Remove the water and most of these slow dramatically. Not because the chemistry becomes impossible, but because reactants cannot move and, in the case of hydrolysis, because the reactant itself is gone.
What 'stable in transit without a cold chain' means
A cold chain exists to keep something cold from origin to destination without interruption. It is expensive, it fails silently, and for a lyophilised peptide it is generally unnecessary.
A dry peptide in a sealed vial tolerates ambient temperatures for the days a parcel spends moving. That is the claim, and it is a narrow one. It does not mean the material is indestructible, that heat is irrelevant, or that a vial left in a hot car indefinitely is fine. It means a few days at ordinary shipping temperatures is not the thing that will degrade it.
It also means an unrefrigerated delivery is not evidence of a careless supplier. For lyophilised material it is the normal and correct way to ship.
Sealed under vacuum or inert gas
Vials are typically stoppered at the end of the drying cycle, before pressure returns to normal, so the vial closes under reduced pressure or under an inert gas such as nitrogen or argon.
This keeps out two things: oxygen, which drives oxidative degradation of susceptible residues, and atmospheric moisture, which would undo the drying. It is also why a properly sealed vial often shows a slight inward pull on the stopper.
A vial that has lost its seal has lost that protection, whatever the certificate says. Physical inspection is worth doing.
What the cake looks like, and what it doesn't tell you
Lyophilised cakes vary in appearance. A firm white cake filling the base of the vial is typical. Cakes can also shrink away from the glass, collapse into a denser layer, or appear as loose powder where the fill was small.
Appearance is weak evidence about quality. A collapsed cake usually reflects the drying cycle - freezing rate, shelf temperature, fill depth - rather than the identity or purity of what is in it. Very small fills, a few milligrams in a large vial, can look like almost nothing at all and be entirely correct.
What appearance can tell you: obvious discolouration, visible foreign matter, or moisture inside a vial that should be dry are all worth querying.
After water goes back in
Every stability advantage described above belongs to the dry state. Adding solvent reverses it: the degradation routes that were suppressed become available again, and the clock starts.
That is why lyophilised material is the form that ships and the form that stores, and why reconstituted material is treated as a much shorter-lived preparation. The specifics of handling reconstituted material in a laboratory are a protocol question and depend entirely on the work being done - this page is about why the powder arrives dry, not about what to do with it afterwards.
Common questions
Why are research peptides shipped as a powder instead of a liquid?
Because the main degradation routes for peptides - hydrolysis, deamidation, aggregation - need water or the molecular mobility water provides. Removing the water by freeze-drying suppresses them, which is what makes a peptide stable enough to ship and store without refrigeration.
Do peptides need to be shipped cold?
Lyophilised peptides generally do not. A dry peptide in a sealed vial tolerates ambient temperature for the few days a parcel is in transit, which is why a cold chain is not normally used. This applies to the dry powder, not to material that has already been reconstituted.
My vial looks half empty or the cake has collapsed. Is something wrong?
Usually not. Cake appearance reflects the freeze-drying cycle and the fill volume, and small fills in a standard vial can look like very little material. Discolouration, visible foreign matter, or moisture in a vial that should be dry are worth querying; a shrunken or powdery cake on its own generally is not.
Why is the vial sealed under vacuum?
Vials are typically stoppered before pressure returns at the end of drying, so the vial closes under reduced pressure or inert gas. That excludes oxygen, which drives oxidation of susceptible residues, and atmospheric moisture, which would reverse the drying.
How long does lyophilised peptide last?
It depends on the peptide, the storage temperature and the integrity of the seal, and a certificate does not answer it - a certificate reports what was measured on a date, not a shelf life. Store sealed vials as described on the label.
Check the evidence for a Causa lot
Our lot pages publish the available results for assayed batches. Request the original laboratory Certificate of Analysis using the lot number, and compare it with the material you are considering. Materials without a qualifying result are marked assay pending. A summary is not a substitute for the original laboratory report.
Related research documentation guides
Research use only. Not for human or veterinary use. This guide explains how to read an analytical document. It is not medical advice and not guidance on use.