Why peptides are supplied as a lyophilised powder, how the cake structure protects the sequence, and what a collapsed or discoloured cake can indicate.
Why peptides are supplied dry
Peptides in solution degrade. Hydrolysis, oxidation, deamidation and aggregation all proceed faster in water, and microbial growth becomes possible. Removing the water arrests almost all of it, which is why every vial ships as a lyophilised solid rather than a ready-made solution.
How lyophilisation works
- Freezing — the solution is frozen solid, locking the peptide in an ice matrix.
- Primary drying — pressure is reduced and ice sublimes directly to vapour, leaving a porous cake.
- Secondary drying — gentle warming removes residual bound water to a low percentage.
- Stoppering — the vial is sealed, often under vacuum or inert gas, before it leaves the chamber.
Reading the cake
- A white, intact, evenly distributed cake is the expected appearance.
- A thin film or scattered powder is normal for small quantities in large vials and is not a defect.
- A collapsed, shrunken or glassy cake can indicate the product warmed above its collapse temperature in transit.
- Yellow or brown discolouration, or visible moisture, warrants contacting the supplier before use.
Handling implications at the bench
Lyophilised peptide is hygroscopic. Allow a refrigerated vial to reach room temperature before opening, or condensation will form on the cold powder and begin the degradation you were avoiding. Reseal promptly, keep desiccant in the storage container, and add diluent slowly down the vial wall rather than directly onto the cake.
References
Supplied for laboratory research use only. Not for human or veterinary use.