Peptides arrive lyophilized — a dry, fluffy powder — because that is the most stable form for shipping and long-term storage. How you reconstitute and store them after they arrive has a direct effect on how long they remain usable. The principles below apply to most research peptides.
Before you open the vial
Let the sealed vial reach room temperature before opening. Lyophilized peptide is hygroscopic; opening a cold vial in humid air invites condensation, and water is the enemy of long-term stability. A few minutes on the bench prevents this.
Choosing a reconstitution solvent
Bacteriostatic water (sterile water with 0.9% benzyl alcohol) is the common choice for research reconstitution because the preservative slows microbial growth. Some hydrophobic peptides need a small amount of acetic acid or another co-solvent to fully dissolve. Add solvent slowly down the side of the vial — never blast it directly onto the powder — and let the peptide dissolve on its own. Gentle swirling is fine; vigorous shaking can shear and denature longer sequences.
Working out the concentration
Use the net peptide content from the COA, not the gross label weight, for accurate concentration math. For example, if a vial reports 10 mg gross at 80% net content, you have 8 mg of actual peptide. Adding 2 mL of solvent gives 4 mg/mL.
Storage timelines
- Lyophilized, unopened: stable for extended periods at -20°C and protected from light. For long horizons, -80°C is better still.
- Reconstituted, short term: refrigerated at 2–8°C, most peptides remain usable for a number of weeks, though this varies by sequence.
- Reconstituted, long term: aliquot and freeze. The single most damaging thing you can do is repeatedly freeze and thaw the same vial.
Why aliquoting matters
Each freeze-thaw cycle physically stresses the peptide and concentrates it as ice forms. Dividing your reconstituted stock into single-use aliquots means you thaw only what you need, leaving the rest untouched. This one habit does more for stability than almost anything else.
Signs of degradation
Cloudiness, visible particulates, or an unexpected color change in a previously clear solution suggest degradation or contamination. When in doubt, discard and reconstitute a fresh aliquot — the cost of a compromised experiment far exceeds the cost of a vial.
For research use only. Not for human or veterinary use.