Lyophilization
Definition
Freeze-drying: the solution is frozen and the water removed by sublimation under vacuum, leaving a dry cake whose chemistry is far more stable than the solution it came from. Properly stored lyophilised peptide keeps for years at -20C.
In more detail
Lyophilisation removes water from a frozen solution under vacuum, taking the ice directly to vapour without passing through a liquid stage. Avoiding that stage is the point: it is the liquid state in which hydrolysis, aggregation and most other degradation routes proceed.
What is left is a porous cake rather than a dense solid, which is why a lyophilised peptide takes solvent back up readily. The appearance of that cake is itself information, and a collapsed or shrunken one indicates the cycle did not run as intended.
Excipients are often present for structural reasons rather than chemical ones. Mannitol is a common bulking agent, giving a cake its form where a milligram of peptide alone would leave almost nothing visible in the vial.
What this means for research sourcing
Getting this right matters when preparing lyophilized research peptides for in vitro work. Volta ships compounds as lyophilized powder for reconstitution.
Related Terms in Preparation
Lyophilized
Freeze-dried. Research peptides ship in this form because a dry powder survives transport and storage that a solution does not, and it has to be reconstituted before any work can be done with it.
Aseptic Technique
The handling practices that keep a preparation from being contaminated: disinfecting a stopper before it is pierced, using a fresh needle, and not touching the parts of the equipment that meet the solution. It governs contamination, not sterility, which a container either had or did not.
Vial
The sealed glass or plastic container a peptide is supplied in, closed with an elastomeric stopper under an aluminium crimp. A single-entry vial carries no preservative and is intended to be entered once; a multiple-entry vial carries one so it can be entered repeatedly.
Aliquot
A measured portion divided out of a larger volume. Splitting a reconstituted solution into single-use aliquots is how repeated freeze-thaw of the whole stock is avoided, and it is the standard answer to a material that degrades on repeated freeze-thaw.
Working Stock
A diluted solution prepared from a concentrated one for day-to-day use, so the concentrated stock is disturbed as rarely as possible. The dilution factor and the date belong on the label, because a working stock is the thing most likely to be misidentified later.
Excipient
Anything in a formulation other than the active substance: bulking agents, buffers, preservatives, stabilisers. Excipients decide how a cake looks and how well it redissolves, and they appear on an approved label alongside the active.
Mannitol
A sugar alcohol used as a bulking agent and cryoprotectant in freeze-dried formulations. It gives the cake its visible structure and shields the peptide during drying, so a vial that looks empty often simply has no mannitol in it.
Peptide Blend
One vial holding two or more compounds pre-mixed at a fixed ratio by the supplier, as against a set of single-compound vials, where each compound has its own vial. A blend's certificate reports each component separately and states no single purity for the vial.
