Key takeaways
- Store sealed lyophilised vials at -20°C, or -80°C for sensitive sequences and longer holds, in the dark with desiccant and away from frost-free defrost cycles.
- Let a cold vial reach room temperature in a desiccator before opening, so condensation does not form on the hygroscopic cake.
- Reconstitute only what you need with a suitable sterile diluent, adding it down the vial wall and swirling rather than shaking.
- Keep solutions at 2 to 8°C short term, freeze single-use aliquots in low-binding tubes, and label every vial with lot, diluent and date opened. The COA for your lot governs.
A lyophilised peptide is about as stable as a peptide gets. That stability holds only while the cake stays dry, cold, dark and sealed. Most of the degradation seen in research labs traces back to handling rather than to the material itself: a vial opened straight from the freezer, a stock solution thawed ten times, a box parked in a frost-free freezer that warms up every night.
This guide covers storage from the moment a shipment arrives to the point a solution is used up. Treat the timeframes as general guidance: stability is sequence-specific, and the supplier’s specification or certificate of analysis for your lot takes precedence over anything written here.
What lyophilisation does, and why the dry cake lasts
Lyophilisation (freeze-drying) removes water from a frozen peptide solution without passing through a liquid phase. It runs in three stages. The solution is frozen, then held under vacuum so the ice sublimes directly to vapour (primary drying), and finally warmed gently to drive off water still bound to the solid (secondary drying).
Water is the medium for most of the chemistry that damages peptides. Hydrolysis of the backbone, deamidation of asparagine and glutamine, and many oxidation pathways all proceed far more slowly when there is little water and little molecular mobility. Put water back, even as a thin film of condensation, and they resume. For more on the chemistry, see our article on peptide stability factors in laboratory settings.
Receiving a shipment
Dry peptides generally tolerate a few days at ambient temperature in transit, but unpack promptly and get sealed vials into cold storage the same day. Our shipping page explains how orders are packed and dispatched.
Receiving-and-opening checklist
- Check the outer packaging for crushing, water damage or signs the parcel sat somewhere hot.
- Inspect each vial seal. The cap and crimp should be intact, with no cracks in the glass.
- Look at the cake. A white to off-white cake or powder is normal. It may have shrunk from the wall or broken up in transit, which is cosmetic. A glassy, sticky, collapsed or visibly wet appearance suggests moisture exposure and is worth querying before use.
- Match labels to paperwork. Confirm product name, lot number and fill against the packing slip and the certificate of analysis.
- Log receipt with date, lot and storage location, then move sealed vials to the freezer.
- Warm before opening. Take the vial from the freezer and let it reach room temperature inside a desiccator before breaking the seal. A cold vial opened in room air draws in humid air, and condensation forms on the cake. A small vial usually needs 20 to 30 minutes; a full box takes longer.
- Work quickly and reseal. If unused powder goes back into the freezer, flush the vial with dry nitrogen or argon if available and store it with desiccant.
Long-term storage of sealed vials
Temperature
For most lyophilised peptides, -20°C is the standard for long-term storage of sealed vials. Where a sequence is known to be sensitive, or material needs to be held for an extended period, -80°C gives extra margin. Avoid door racks, where temperature swings are largest.
Frost-free freezers
Frost-free (auto-defrost) freezers stay clear of ice by periodically warming the evaporator coils to melt accumulated frost. Each cycle briefly raises the compartment temperature, which is a poor fit for peptides and a worse one for frozen solutions. A manual-defrost laboratory freezer with a temperature log or alarm is the better choice.
Light
Tryptophan, tyrosine, cysteine and methionine residues are susceptible to photo-oxidation, and some modified peptides carry light-sensitive labels or fluorophores. Store vials in their outer box or an opaque container, use amber vials or foil when material sits on the bench for long periods, and keep vials away from lamps and windows.
Moisture
Many lyophilised peptides are hygroscopic, particularly those supplied as acetate or trifluoroacetate salts and those rich in charged residues. They take up water from the air readily. Keep seals intact, store vials in a sealed secondary container with desiccant, and replace or regenerate the desiccant when its indicator changes colour.
Reconstitution for laboratory work
Reconstitute only what the experiment needs. Before starting, check the certificate of analysis for net peptide content and any solubility notes; our guide to interpreting a peptide certificate of analysis explains each field.
Choosing a diluent
- Sterile water is the simplest starting point for peptides with good aqueous solubility.
- Bacteriostatic water contains 0.9% benzyl alcohol, which limits microbial growth in a vial that is accessed more than once. Benzyl alcohol can interfere with some cell-based and biochemical assays, so confirm compatibility first.
- Dilute acetic acid helps dissolve basic peptides and some sequences that aggregate in water. Prepare the stock in the acid, then dilute into your working buffer.
- Hydrophobic sequences may need a small volume of organic solvent before aqueous dilution. Bear in mind that DMSO can oxidise cysteine and methionine residues.
Technique
Work in a clean area, ideally a biosafety cabinet or laminar flow hood, with sterile consumables and alcohol-wiped septa. Add the diluent slowly down the inside wall of the vial rather than directly onto the cake. Swirl or roll gently until dissolved. Do not shake or vortex hard, because foaming and air-liquid interfaces promote aggregation. The result should be clear; persistent cloudiness or particles point to incomplete dissolution or aggregation. More detail is in our notes on laboratory handling best practices for peptides.
Storing peptide solutions
Once dissolved, a peptide is far more vulnerable. For short-term use, keep solutions at 2 to 8°C and protected from light. How long they stay usable depends on sequence, pH, diluent and concentration, and can range from days to a few weeks. If a solution is needed beyond that, freeze it.
Aliquot before you freeze
Each freeze-thaw cycle stresses a peptide. As water turns to ice, solutes and peptide are concentrated in the remaining liquid, and some buffers shift pH sharply on freezing, sodium phosphate being the classic example. Divide the stock into single-use aliquots straight after reconstitution, freeze them at -20°C or -80°C, and thaw each one once. Discard what is left rather than refreezing it.
Use low-binding polypropylene tubes. Peptides adsorb to ordinary plastic and glass surfaces, and at low concentrations that loss can be a meaningful share of the material.
Oxygen-sensitive sequences
Peptides containing cysteine, methionine or tryptophan are prone to oxidation, and free cysteine thiols can form disulfide bonds, a reaction that speeds up at neutral to basic pH. Keep headspace small by matching tube size to aliquot volume, use degassed diluents, and overlay with nitrogen or argon before capping where the sequence warrants it.
Labelling and logging
A good log separates a genuine stability problem from a handling error. Every vial and aliquot should carry, at minimum:
- Peptide name and lot number
- Date received and date opened or reconstituted
- Diluent used and nominal stock concentration
- Storage temperature and location
- Initials of the person who prepared it
Use freezer-rated labels or cryo markers, since standard ink smears after a few rounds of condensation. Record freeze-thaw events and any excursion, such as a freezer alarm or power interruption, against the lots affected.
Storage checklist at a glance
The windows below are typical practical ranges, not guarantees. Stability depends on the sequence, salt form and handling, and the supplier’s specification or certificate of analysis for the lot governs.
| Form | Temperature | Light | Typical practical window | Notes |
|---|---|---|---|---|
| Sealed lyophilised vial | -20°C | Dark, in outer box | Typically months to years | Store with desiccant; warm to room temperature in a desiccator before opening |
| Sealed vial, sensitive sequence or extended hold | -80°C | Dark | Longer than at -20°C for many sequences | Manual-defrost freezer; keep door openings to a minimum |
| Opened, resealed powder | -20°C | Dark | Shorter than sealed; use promptly | Flush with inert gas if available; seal in a container with desiccant |
| Reconstituted working solution | 2 to 8°C | Dark | Days to a few weeks | Sterile technique; check diluent compatibility with the assay |
| Frozen solution aliquots | -20°C or -80°C | Dark | Weeks to months | Single-use aliquots in low-binding tubes; thaw once, do not refreeze |
| Solutions of Cys, Met or Trp-containing sequences | 2 to 8°C short term; -80°C frozen | Dark | Often shorter than for other sequences | Degassed diluent, minimal headspace, inert gas overlay |
Store dry, cold, dark and sealed. Warm before opening, aliquot after dissolving, and write everything down.
At Aussie Peptide Co we hold lyophilised stock at -20°C in Melbourne. You can browse the research peptide range for current lots. All products are supplied for in-vitro laboratory research use only.
References & further reading
- New Trends in Freeze-Drying of Pharmaceutical Products Pharmaceutics (2023), PubMed Central
- Effectiveness of Lyoprotectants in Protein Stabilization During Lyophilization Pharmaceutics (2024), PubMed Central
- Strategies for Improving Peptide Stability and Delivery Pharmaceuticals (Basel) (2022), PubMed Central
- Prudent Practices in the Laboratory: Handling and Management of Chemical Hazards National Research Council, NCBI Bookshelf
- ICH Q1A (R2) Stability testing of new drug substances and drug products - Scientific guideline European Medicines Agency
Frequently asked questions
For short periods, usually yes. Dry peptides generally tolerate a few days at ambient temperature in transit, but that is not a storage plan. Move sealed vials to -20°C on arrival, or -80°C for sensitive sequences and longer holds, and keep them dark with desiccant. Stability is sequence-specific, so the supplier's specification or certificate of analysis for your lot takes precedence.
A vial taken straight from the freezer is colder than the room air around it. Open it cold and humid air rushes in, and moisture condenses on the cake. Many lyophilised peptides are hygroscopic, and that water restarts hydrolysis and other degradation. Let the sealed vial reach room temperature inside a desiccator first. A small vial usually needs 20 to 30 minutes.
Sterile water is the simplest choice for peptides that dissolve well in water. Bacteriostatic water contains 0.9% benzyl alcohol, which limits microbial growth in a vial accessed more than once, but the benzyl alcohol can interfere with some cell-based and biochemical assays. Check compatibility with your method first. Basic or aggregation-prone sequences may dissolve better in dilute acetic acid.
Ideally once. Each freeze-thaw cycle concentrates solutes in the unfrozen liquid, can shift the pH of some buffers, and encourages aggregation. Divide the stock into single-use aliquots in low-binding tubes straight after reconstitution, freeze them at -20°C or -80°C, and thaw each aliquot only when needed. Discard any leftover solution rather than refreezing it, and log each thaw against the lot.
Our in-house team writes laboratory-focused guides on peptide documentation, testing, storage and handling. Content is reviewed against published analytical practice and is provided strictly for research use.
