909 AMINOSStability of Lyophilized Peptides: What Degrades a Sealed Vial
Lyophilization removes most of the water from a peptide and often slows degradation, but it doesn't stop it. How stable a given material is can only be established by stability testing of that material.
- A lyophilized peptide is often more stable than the same peptide in solution, but that is a general tendency, not a rule.
- Moisture, temperature, oxygen and light are the main factors that affect a lyophilized material.
- Methionine, cysteine, tryptophan, asparagine, glutamine and aspartic acid are the residues most prone to degradation reactions.
- A certificate of analysis describes the sample on its analysis date; it doesn't predict how the material will change afterward.
1What lyophilization does
Lyophilization (freeze-drying) removes most of the water from a peptide. Because many degradation reactions need water, a lyophilized peptide is often more stable than the same peptide in solution.
The actual stability of a given material depends on its sequence, its formulation, its residual moisture and how it is stored, and it can only be established by stability testing of that material. Lyophilized material also still changes over time.
2What affects a lyophilized peptide
Lyophilized peptides are often hygroscopic: they absorb water from the air. Absorbed water lets degradation reactions proceed faster.
Chemical reactions generally run faster when warmer. Temperature changes can also contribute to moisture exposure, for example through condensation when a cold container is opened in warmer air; how much depends on handling and on whether the container stays sealed.
Some amino acids oxidize on contact with air.
Some amino acids absorb light and can degrade under prolonged exposure.
3Which amino acids are most sensitive
You can check a sequence for these residues (see Peptide Identifiers):
| Residue | Main concern |
|---|---|
| Methionine (M), Cysteine (C), Tryptophan (W) | Oxidation |
| Asparagine (N), Glutamine (Q) | Deamidation |
| Aspartic acid (D), especially next to G or P | Chain cleavage or rearrangement |
| Tryptophan (W), Tyrosine (Y) | Light sensitivity |
Having these residues doesn't mean a material is unstable. It means these are the reactions to look for.
4How degradation would show up in testing
Degradation products are usually peptide-related impurities: oxidized, deamidated or cleaved forms of the target. On an HPLC chromatogram they appear as additional peaks and lower the main peak's share of the area. See Impurity Peaks on an HPLC Chromatogram.
A certificate of analysis describes the sample on the date it was analyzed. It doesn't predict how the material will change afterward.
5Reading stability information
- Is a storage condition stated for this specific product? A general statement ("store cold") isn't the same as a condition verified for that product.
- Is there a retest or expiry date, and is it based on stability data?
- When was the lot analyzed? Every 909 certificate shows its analysis date.
909 Aminos does not publish handling or storage conditions for a product unless that information has been verified for it, and does not publish preparation instructions of any kind. Laboratories should handle and store materials using the controls appropriate to their own procedures.
?Frequently asked questions
Is a lyophilized peptide stable indefinitely?
No. Lyophilization often slows degradation, but it doesn't stop it, and how much it helps varies by material. Moisture, temperature, oxygen and light all play a part.
Does a certificate of analysis tell me how long a material stays within specification?
No. It reports the sample on its analysis date. Shelf life needs stability testing over time.
Why doesn't 909 publish storage temperatures for each product?
Because a stated condition should be verified for that product. Until it is, 909 doesn't state one.
For laboratory research use only. Not for human or veterinary use. Not FDA approved.