Peptide storage & handling

Peptides degrade through a small number of well-characterized pathways: hydrolysis of peptide bonds, oxidation of methionine, cysteine, tryptophan, and tyrosine, deamidation of asparagine and glutamine, disulfide scrambling, and physical aggregation. Each pathway accelerates with heat, water activity, and oxygen exposure. Lyophilization removes most of the water and dramatically slows every pathway — which is why dry powder vials are shelf-stable for months to years while a reconstituted solution is good for days to weeks.

Practical consequence: keep peptides dry, cold, dark, and undisturbed until you actually need to use them. Once reconstituted, the clock starts.

• Long-term storage: −20 °C (standard lab freezer) protected from light. Most lyophilized research peptides are stable 24+ months under these conditions.
• Extended storage: −80 °C for multi-year archival, particularly for peptides with oxidation-prone residues (methionine, cysteine).
• Short-term (weeks): 2–8 °C refrigeration is acceptable if you'll reconstitute within a few weeks.
• Equilibrate before opening: let the sealed vial reach room temperature (10–15 minutes on the bench) before breaking the seal. Opening a cold vial pulls humid air onto cold glass and condenses water onto the powder.
• Keep the stopper sealed: never remove the rubber septum. Draw through it with a sterile needle.

The diluent you pick determines how long the reconstituted vial lasts and how many draws you can safely take from it.

BAC water is the default for any multi-draw research protocol. SWFI is appropriate when the entire vial will be used in a single session or when benzyl alcohol is incompatible with downstream assays.

1. Equilibrate both vials (peptide + diluent) to room temperature.
2. Wipe both septa with a fresh 70% isopropyl alcohol swab; let dry.
3. Draw the diluent into an insulin syringe (typically 1–3 mL, depending on target concentration — see dosage math).
4. Insert the needle into the peptide vial at an angle and aim the stream against the side wall, never directly onto the powder cake. A direct stream foams the peptide and shears chains.
5. Swirl gently for 30–60 seconds to dissolve. Do not shake or vortex.
6. Inspect: the solution should be clear and colorless. Cloudiness, color, or visible particulates means discard.
7. Label the vial with peptide name, concentration (mg/mL), diluent, and reconstitution date.

These ranges reflect commonly cited research-stability data; actual stability depends on concentration, diluent, lot, and storage discipline. When in doubt, use the shorter end of the range.

• Freeze–thaw cycles: each cycle causes ice-crystal damage and aggregation. If you must freeze a reconstituted solution, aliquot it into single-use volumes before freezing, so each aliquot thaws exactly once.
• Light: tyrosine and tryptophan absorb near-UV light and oxidize on prolonged exposure. Amber vials or a foil wrap are sufficient; total darkness isn't required.
• Heat excursions: peptides shipped on cold packs are designed to survive 48–72 hours above freezer temperature. Sustained exposure above 25 °C accelerates every degradation pathway.
• pH drift: bacteriostatic water is mildly acidic (pH ~5). For peptides that prefer neutral pH (e.g. some intranasal Selank/Semax preparations), buffered diluents extend stability.
• Adsorption: very dilute peptide solutions can lose mass to plastic syringe walls. Reconstitute at higher concentration and dilute at use, rather than storing a dilute working solution.

• Visible cloudiness, precipitate, or color change.
• Septum has been punctured more than ~10 times (the rubber starts to crumb into the solution).
• BAC reconstitution older than 30 days unless you have lot-specific stability data.
• Any vial left at room temperature for >12 hours.
• Any vial whose label or reconstitution date is missing or illegible.