Freeze-Thaw Cycle
Definition
A cycle of freezing and thawing a substance, which can damage peptide structure through ice crystal formation and aggregation. Multiple freeze-thaw cycles significantly degrade peptides; aliquoting prevents this.
Related Terms in Storage & Stability
Aggregation
The clumping together of peptide molecules, often caused by heat, agitation, or repeated freeze-thaw cycles. Aggregated peptides may lose potency and can trigger immune reactions if injected.
Deamidation
A common peptide degradation reaction where asparagine or glutamine residues lose an amide group. Accelerated by heat and alkaline pH. Detected on COAs as impurity peaks.
Oxidation
A degradation reaction where methionine, cysteine, or tryptophan residues in peptides react with oxygen. Exposure to light, air, or peroxides accelerates oxidation. Causes loss of potency.
Desiccant
A moisture-absorbing substance (typically silica gel) included in peptide packaging to prevent humidity-driven degradation during storage of lyophilized powders.
Beyond-Use Date (BUD)
The date after which a compounded preparation should not be used. Determined by the compounding pharmacy based on stability data. Differs from expiration date, which applies to manufactured drugs.