The problem freeze-drying solves
A peptide in water is a peptide being slowly taken apart. Water is a reactant in hydrolysis of the backbone and in the deamidation of asparagine and glutamine, and it is the medium in which oxidation, aggregation and microbial growth happen. Remove the water and those reactions have nothing to run in. That is the entire logic of lyophilisation: a peptide that would lose measurable purity in weeks as a solution is stable for years as a dry solid.
What lyophilisation is
The process has three stages, and each leaves a trace you can see in the vial.
- Freezing. The purified peptide solution is dispensed into vials and frozen, typically well below −40°C, so the water becomes ice crystals with the peptide and any salts held in the solid between them.
- Primary drying. Under vacuum, with gentle heat, the ice sublimes directly from solid to vapour without melting. This removes the bulk of the water and leaves a porous solid with the shape of the original frozen volume: the cake.
- Secondary drying. Temperature is raised slightly to drive off water that is bound to the peptide rather than frozen as ice. Residual moisture after this step is typically a few percent or less.
The vial is then stoppered under vacuum or dry nitrogen and crimped. That is why a fresh vial often "pulls" when the stopper is pierced, and why diluent added through a needle is drawn in.
What a good cake looks like
- A uniform white or off-white solid filling part of the vial, sometimes a thin disc, sometimes a plug, depending on the fill volume.
- Loose powder or a broken cake is normal. Cakes crack and shift in transit. A cake that has broken into pieces has not changed chemically.
- A shrunken, glassy or sticky mass is not normal. That is collapse or melt-back, which happens when the product warmed during drying, and it usually reconstitutes poorly. It is a manufacturing defect, not a storage one.
- Colour depends on the compound. GHK-Cu is blue because of the copper complex; NAD+ is white to slightly yellow; almost everything else is white.
What the powder contains
Lyophilised peptide is not pure peptide by mass. The solid also contains the counter-ion left over from purification, most often trifluoroacetate (TFA) from the HPLC mobile phase, sometimes acetate if the manufacturer has exchanged it, plus a small amount of bound water. For a peptide with several basic residues the counter-ion alone can be a meaningful fraction of the gross weight. This is why a certificate can report 99% HPLC purity and a net peptide content well below 100% at the same time: the two numbers measure different things. Our guide to reading a certificate of analysis covers both.
Why it ships at room temperature
With the water gone, a few days at ambient temperature in a parcel has no measurable effect on a sealed vial. Manufacturers ship lyophilised peptides worldwide this way and so do we. Cold matters for long-term storage, where months at room temperature would add up, so vials go into a −20°C freezer on arrival. The storage guide gives horizons by form.
Reconstituting a cake
A porous cake dissolves quickly because the diluent has a large surface to reach. Let the vial come to room temperature first, so no condensation forms on the cold solid, then run the diluent down the inside wall rather than onto the cake, and swirl rather than shake. The concentration calculator covers the arithmetic. Once in solution the clock that freeze-drying stopped is running again, which is the reason the storage guide gives days to weeks for solutions and years for powder.
In our catalog
Every compound in the catalog is supplied as lyophilised powder except bacteriostatic water, which is the diluent.