Freeze-dried peptide is remarkably stable. The moment water goes in, the clock starts and it runs faster than most people assume.
why it arrives as powder
Lyophilisation removes water by freezing the material and pulling it off under vacuum. Water is what enables most of the reactions that degrade a peptide, so removing it buys enormous stability — a properly lyophilised, sealed, refrigerated peptide can hold for a long time. That stability is a property of the dry state and it does not survive reconstitution.
how peptides actually fall apart
Three main routes. Oxidation, which hits methionine, cysteine and tryptophan residues especially. Deamidation, where asparagine and glutamine residues convert and change the molecule. And aggregation, where peptide chains clump into species that are no longer the compound you started with. Which route dominates depends on the specific sequence, which is why blanket shelf-life claims across a whole product range are not meaningful.
Freeze-dried peptide is remarkably stable.
water, and which kind
Bacteriostatic water contains roughly 0.9% benzyl alcohol as a preservative, which is what permits repeated withdrawals from the same vial over time. Sterile water has no preservative and is single-use in practice. The distinction matters because the failure mode is bacterial growth in a multi-use vial, and that failure is invisible.
the gap nobody mentions
Most research peptides ship without any cold chain — ambient parcels, several days in transit, potentially a hot van and a hotter porch. The COA describes material as it was at synthesis, not as it arrived. That gap between the tested sample and the vial on your counter is unmeasured, unmanaged, and almost never discussed on the product page.