Lyophilization (Freeze-Drying)
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What is Lyophilization?
Lyophilization, commonly known as freeze-drying, is a dehydration process used to preserve peptides and other biological materials by removing water from a frozen sample through sublimation (the direct transition from solid ice to water vapor without passing through the liquid phase). The result is a stable, dry powder that retains the chemical integrity and biological activity of the original peptide. Virtually all research peptides are supplied in lyophilized form because this state offers superior long-term stability compared to liquid solutions.
The Lyophilization Process
The freeze-drying process occurs in three main stages. First, during the freezing stage, the peptide solution is cooled to a temperature well below its freezing point, forming ice crystals. Second, during primary drying (sublimation), the pressure is reduced and gentle heat is applied, causing the ice to sublimate directly into vapor, which is then collected by a condenser. Third, during secondary drying (desorption), residual bound water molecules are removed by raising the temperature further under vacuum. The result is a dry cake or powder with a moisture content typically below 1-3%.
Benefits for Peptide Stability
Lyophilization is the preferred preservation method for peptides because it dramatically extends shelf life by eliminating the water that would otherwise promote hydrolysis, oxidation, and microbial growth. Lyophilized peptides can remain stable for years when stored properly at low temperatures (-20C or below), whereas peptides in solution may degrade within days or weeks. The process also facilitates accurate weighing, shipping at ambient temperature for short durations, and straightforward reconstitution when the researcher is ready to begin their experiments.
Reconstituting Lyophilized Peptides
Before use in research, lyophilized peptides must be reconstituted by dissolving the powder in an appropriate solvent. The choice of solvent depends on the peptide's charge and hydrophobicity. Sterile water or bacteriostatic water is suitable for most hydrophilic peptides, while hydrophobic peptides may require a small amount of DMSO or dilute acetic acid. It is always advisable to dissolve a small test quantity first, and to consult the supplier's solubility recommendations provided with each product.