How to store research peptides

Store lyophilized (freeze-dried) peptides in the freezer, store reconstituted peptides in the fridge, and use a vial within a few weeks of mixing it. That's the whole rule. Everything below is the why, because most ruined vials come from getting one of those three wrong.

Lyophilized powder: the freezer is for the long haul

A sealed vial of dry peptide is surprisingly tough. With no water present, there's almost nothing for the molecule to react with.

• Long-term (months to a year+): freezer, around -20°C.
• Short-term (a few weeks): a regular fridge is fine.
• In transit or on the bench briefly: room temperature won't hurt it.

Keep it dry and keep it dark. Light and moisture are the enemies, not a few degrees of warmth. Every vial in our catalog is lyophilized for exactly this reason — it travels across Canada without a cold pack and arrives chemically intact.

After you reconstitute, the clock starts

The moment water goes in, the peptide becomes far more fragile. Now it can degrade, and bacteria have something to grow in.

• Keep the reconstituted vial in the fridge (2–8°C), never the door shelf where the temperature swings.
• Using bacteriostatic water (which contains a small amount of preservative) gives you a longer usable window than plain sterile water — see how to reconstitute a lyophilized peptide for the mixing step.
• Treat it as a "use it" item, not a "store it" item. A few weeks cold is a reasonable expectation; indefinite storage is not.

Freeze-thaw is what actually kills peptides

People obsess over temperature and ignore the real damage: cycling. Freezing and thawing the same solution over and over physically stresses the molecule and drops your effective purity each round.

If you need to keep a reconstituted solution longer, split it into small single-use aliquots before freezing. Then you only ever thaw the portion you need, and the rest stays untouched.

"It arrived warm" is not a problem

This is the most common worry we hear, and it's a non-issue. Lyophilized peptides are freeze-dried specifically so they don't need refrigerated shipping. A parcel that sat in a warm truck is completely normal.

What you should check on arrival isn't the temperature — it's the paperwork. Scan the QR code on the vial. Every pepuro vial resolves to its own report at pepuro.com/v/<uuid>, so you can confirm the exact vial you're holding was tested, rather than trusting a generic batch PDF.

The one-line version

• Dry powder → freezer for the long term, fridge is fine short term.
• Mixed → fridge, use within weeks.
• Never freeze-thaw repeatedly — aliquot instead.
• A warm delivery means nothing; a missing test report means everything.

For research use only. Not for human or animal consumption.