Why Lyophilisation?
Most Stackpure peptide vials contain lyophilised (freeze-dried) powder rather than pre-dissolved solution. Lyophilisation removes water under vacuum while the sample is frozen, preserving peptide integrity and extending shelf life to up to 24 months at −20 °C. Lyophilised peptides are also more resistant to oxidation and microbial contamination than dissolved preparations. The trade-off is that researchers must reconstitute the powder prior to use, which requires attention to solvent selection, concentration calculation, and reconstitution technique to avoid aggregation, degradation, or inaccurate concentration.
Solvent Selection
The appropriate reconstitution solvent depends on the peptide's physicochemical properties. For most research peptides in this catalog, bacteriostatic water (sterile water with 0.9% benzyl alcohol as a preservative) is the standard choice: it is compatible with most peptides, provides microbial inhibition to extend reconstituted stability, and is suitable for cell culture use at appropriate dilutions. Acidic peptides (containing multiple Asp or Glu residues) may require a small amount of dilute acetic acid (0.1% glacial acetic acid in water) to aid solubility before diluting to working concentration in PBS or culture medium. Basic peptides (Lys, Arg-rich) may dissolve more readily in sterile PBS. If a peptide forms a turbid solution, do not centrifuge, instead add solvent dropwise with gentle swirling until clear.
Concentration Calculation
To prepare a stock solution of known concentration: (1) Note the mass of peptide in the vial (e.g., 5 mg). (2) Determine the required concentration (e.g., 1 mg/mL). (3) Add volume of solvent = mass ÷ concentration (e.g., 5 mL for 1 mg/mL). (4) Confirm molecular weight from the COA to calculate molar concentration if needed (e.g., 1 mg/mL ÷ 1419.5 g/mol × 1000 = ~0.70 mM for BPC-157). Always use a calibrated micropipette and volumetrically verified glassware. Mass stated on the vial is nominal, actual fill weight may vary by ±5%. Account for this in concentration-sensitive experiments by weighing the vial before and after adding solvent.
Reconstitution Technique
Reconstitution should be performed under sterile conditions using a laminar flow hood when possible. (1) Allow the vial to equilibrate to room temperature before opening to prevent condensation. (2) Wipe the septum with 70% isopropanol. (3) Draw the calculated volume of solvent into a sterile syringe with a fresh needle. (4) Inject the solvent slowly against the vial wall, do not inject directly onto the lyophilised cake under pressure, as this can cause aggregation. (5) Swirl gently, do not vortex. (6) If the peptide does not dissolve within 5 minutes, apply gentle warming (palm of hand or 37 °C water bath for 30 seconds) and continue swirling. Do not apply heat exceeding 40 °C.
Aliquoting and Storage
Reconstituted peptide should be aliquoted into single-use volumes to minimise freeze-thaw cycles. Use sterile LoBind polypropylene microcentrifuge tubes (1.5 mL) and fill to 90% capacity to allow for expansion during freezing. Label with peptide name, concentration, preparation date, and solvent. Store at 4 °C if using within 30 days; at −80 °C for longer-term storage (up to 6 months for most peptides in bacteriostatic water; some degrade faster, check stability data if available). Never refreeze a thawed aliquot. For peptides containing disulfide bonds or methionine residues, use nitrogen-purged vials to minimise oxidation.