Lyophilised Peptides, Reconstitution & −20 °C Storage: A Practical Guide to the Corex Vitality™ Learning Hub

For in-vitro laboratory research use only. Not for human or veterinary use.

Reconstituting and storing a lyophilised peptide correctly is one of the simplest ways to protect the quality of your in-vitro work. This guide explains what happens at each stage in plain English, and shows how to use the new interactive tools in the Corex Vitality™ Learning Hub to check your numbers before you pick up a pipette.

1. How to use the Corex Vitality™ Interactive Learning Hub

Our Learning Hub now opens with three interactive tools, all in one panel near the top of the page.

• Interactive Knowledge & Compound Explorer. Type a peptide name, CAS number or topic into the search bar, or tap a pathway pill such as “Storage & Reconstitution”. Compound cards show the CAS number, molecular weight, sequence or formula and storage temperature, with one-tap links to the product page and the certificate of analysis. New guides, including this one, appear automatically.
• In-Vitro Laboratory Reconstitution & Dilution Calculator. Pick the vial mass, diluent volume and target aliquot, or type your own values. The calculator shows the stock concentration in mg/mL (and µg/mL), the micropipette volume per aliquot in mL and µL, and how many aliquots one vial gives. A vial diagram fills as you change the volume.
• 4-Step Lab Protocol & COA Walkthrough. Four clickable steps cover receiving and storage, reconstitution, reading an HPLC and mass spectrometry certificate, and aliquoting. Each step ends with a short self-check question and a link to verify your batch.

2. Why research peptides arrive as a freeze-dried “puck”

Lyophilisation, or freeze-drying, removes water from a frozen peptide solution by sublimation: under a deep vacuum at low temperature, ice turns straight into vapour without melting. What is left is a dry, porous solid.

This matters because water drives most of the ways a peptide breaks down. In solution, peptide bonds can be slowly cut by hydrolysis, and residues such as methionine and cysteine can oxidise. At room temperature that can become measurable within days or weeks. As a dry solid, the same molecule is far more stable.

The result is usually a small white cake, sometimes called a puck, or a loose powder at the bottom of the vial. A 2 mg or 5 mg vial can look almost empty, and the cake may crack or shrink in transit. None of this affects the contents: the quantity in the vial is measured on the certificate of analysis.

3. Choosing the right laboratory solvent

There is no single solvent that suits every peptide. The best starting point depends on the sequence, so work it out before you open the vial and always test a small portion first, keeping the rest dry.

Step 1: estimate the overall charge

Count the basic groups (lysine K, arginine R, histidine H and a free N-terminus) and the acidic groups (aspartic acid D, glutamic acid E and a free C-terminus). An acetylated N-terminus or an amidated C-terminus does not count. This is only an approximate guide, and lipidated peptides often behave differently.

• More basic groups (basic peptide): try water first. If it is slow, add a small amount of dilute acetic acid, then dilute to volume.
• More acidic groups (acidic peptide): try water or a neutral buffer first. If it is slow, add a small amount of dilute (about 0.1%) aqueous ammonia, then dilute to volume.
• Around neutral pH: phosphate-buffered saline (PBS) at pH 7.0–7.4 often works for concentrations up to about 1 mg/mL.
• Very hydrophobic or neutral sequences: dissolve in a small volume of an organic solvent such as DMSO, DMF or acetonitrile, then add the aqueous buffer slowly while mixing. Check that the organic solvent is compatible with your assay.

Step 2: check for sensitive residues

Sequences containing cysteine, methionine or tryptophan oxidise easily, so use freshly degassed, oxygen-free solvent and keep air exposure to a minimum. Do not add reducing agents such as DTT to peptides that rely on a disulfide bridge. Asparagine and glutamine shorten shelf life in solution, so prepare these fresh and aliquot promptly. Each Corex Vitality™ product page has a Storage & Handling box with a compound-specific note.

Step 3: water, sterile water or bacteriostatic water

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol. The benzyl alcohol slows bacterial growth but does not sterilise, it is not suitable for every peptide, and it can interfere with cell-based assays. Our BAC Water for laboratory reconstitution is one option. Sterile water or a sterile buffer without preservative is the better choice for a single session or for assays where benzyl alcohol could interfere.

Swirl gently, and if needed use brief sonication in a water bath. Do not heat the solution. The solubility approach above is paraphrased in our own words from Bachem’s peptide solubility guidelines.

4. Step-by-step reconstitution and concentration maths

1. Let the vial reach room temperature. Opening a cold vial draws moisture from the air onto the dry powder as condensation. Leave it sealed, ideally in a desiccator, until it reaches room temperature. Then weigh out or reconstitute quickly and reseal tightly. Peptide powders absorb moisture, and absorbed water lowers the real peptide content of what you weigh.
2. Add solvent down the glass wall. Aim the stream at the inside wall of the vial, never directly onto the cake, and add it slowly.
3. Swirl gently. Roll or swirl the vial until the solution is clear. Do not shake or vortex: vigorous mixing creates air–liquid surfaces where peptides can unfold and clump together.
4. Label it with the compound, concentration, date and batch number.

Concentration is one division:

Concentration (mg/mL) = Lyophilised vial mass (mg) ÷ Diluent volume (mL)

Worked example: a 10 mg vial with 2 mL of solvent gives 10 ÷ 2 = 5.00 mg/mL, which is 5,000 µg/mL. A 500 µg laboratory aliquot is therefore 500 ÷ 5,000 = 0.10 mL, or 100 µL, and the vial holds 20 aliquots of that size. You can check any combination with the live calculator on the Learning Hub.

If your certificate reports net peptide content as well as purity, our guide to HPLC purity vs net peptide content explains how that affects the true amount of peptide in solution. The calculator uses the label mass; a rough net amount is label mass × HPLC purity × net peptide content.

5. Preventing freeze–thaw damage and storing at −20 °C or colder

For longer storage, unopened lyophilised vials are best kept tightly closed at −20 °C or colder, away from light and moisture. A laboratory fridge (2–8 °C) is fine short-term for vials you plan to open soon, and room-temperature transit is normal for dry peptides. Peptide pens are different, because they hold a solution that is filled fresh to order: keep them at 2–8 °C and do not freeze them. Once reconstituted, a peptide is at its most fragile, and peptides do not keep long in solution.

Each time a solution freezes, ice crystals form and grow. They concentrate the peptide and any salts into small pockets, create new ice–liquid surfaces and put physical stress on the chains, which can lead to unfolding, clumping and breakdown. Every extra freeze–thaw cycle adds to that damage.

The fix is simple: divide fresh stock into single-use micro-aliquots using a calibrated micropipette, label each tube, and freeze them at −20 °C (or −80 °C for longer-term work). Thaw only the aliquot you need, and do not refreeze it. For background on peptide structure, see What Are Peptides?

Check your batch

Every Corex Vitality™ vial carries a report number. Match it to its certificate on our verification page before you start.

Sources

• Bachem. Handling and Storage Guidelines for Peptides and Peptide Solubility Guidelines. Bachem Knowledge Center (accessed October 2026; paraphrased).
• Carpenter JF, Pikal MJ, Chang BS, Randolph TW. Rational design of stable lyophilized protein formulations: some practical advice. Pharmaceutical Research 14, 969–975 (1997).
• Wang W. Lyophilization and development of solid protein pharmaceuticals. International Journal of Pharmaceutics 203, 1–60 (2000).
• Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharmaceutical Research 27, 544–575 (2010).
• United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding – Sterile Preparations.
• European Pharmacopoeia. Monograph 0169, Water for injections, and 5.1.3, Efficacy of antimicrobial preservation. EDQM, Council of Europe.

All Corex Vitality™ products are supplied strictly for in-vitro laboratory research use only and are not for human or veterinary use. Nothing in this article is medical advice, and no information here describes use in humans or animals.