A sealed vial of lyophilised peptide is one of the more stable forms a biomolecule can take. Water, the medium in which most degradation reactions run, has been removed, and the powder sits under a stopper and crimp cap. What shortens the usable life of a vial is almost always something that happens after the seal is broken. This guide walks through the four main factors.
1. Water
Once a peptide is in solution, hydrolysis, deamidation and oxidation proceed at rates that depend on temperature, pH and the sequence. Asparagine and glutamine residues deamidate, methionine and cysteine oxidise, and aspartate bonds can cleave. The same peptide that keeps for years as powder may show measurable change within weeks in solution at room temperature. The practical consequence: reconstitute only what a protocol needs within a short period, and keep the rest as powder.
2. Temperature
Every 10 °C roughly doubles the rate of most degradation reactions. Sealed powder is best stored at -20 °C for long-term storage, with 2 to 8 °C acceptable for weeks. Reconstituted solution belongs in the refrigerator at 2 to 8 °C. Freezing a solution is possible but introduces the next factor.
3. Freeze-thaw cycles
When a solution freezes, ice forms first and the remaining liquid becomes more and more concentrated in peptide and salts. Local pH shifts and the formation of ice crystals put mechanical and chemical stress on the molecule, and some peptides aggregate on thawing. A single freeze-thaw cycle is usually tolerable; repeated cycles are not. If a reconstituted vial must be frozen, split it into single-use aliquots first so that each portion is thawed only once.
4. Light and oxygen
Tryptophan, tyrosine and methionine are light-sensitive and oxidation-prone. Amber vials or a box in the refrigerator solve the light problem. Oxygen enters each time a needle passes the stopper, which is one reason to minimise the number of draws from a vial and to use bacteriostatic water, whose preservative keeps a multi-draw vial from becoming a culture medium.
A simple storage protocol
Sealed vials: -20 °C, dark, dry. Let the vial reach room temperature before opening so that no condensation forms on the cold powder.
Reconstituted: 2 to 8 °C, dark, dated label, used within the period your protocol defines.
If freezing a solution is unavoidable: aliquot first, freeze once, thaw once.
Record lot number, reconstitution date and solvent volume for every vial.
Our FAQ summarises the storage conditions for every product in the range. The temperatures above apply to all peptides we supply.
For laboratory research use only. Not dosing or medical advice.