What does lyophilised mean for a research peptide?
Freeze-drying explained: why peptides are supplied this way, what else is in the vial besides peptide, and how to handle a lyophilised cake.
Every peptide in the Alphex catalogue is supplied "lyophilised". The word appears on the label, the specification table and the COA, and it explains a great deal about how the vial should be handled: why it is under vacuum, why the contents look like a small white cake or a film rather than a powder you could pour, why the mass on the label is not net peptide, and why the compound is stable in the vial but not in solution. This note explains what lyophilisation is and what it means for the researcher. All Alphex products are for laboratory and in-vitro research only.
Lyophilisation in one paragraph
Lyophilisation, or freeze-drying, removes water from a frozen solution by sublimation: the peptide solution is frozen solid, a vacuum is applied, and ice passes directly to vapour without melting. Because the water leaves as vapour from a solid, the peptide is never exposed to liquid water at a temperature where it would degrade, and it is left behind as a porous, low-density solid that occupies roughly the volume the frozen solution did. That is why a 5 mg vial can look almost empty, or contain a thin film, or a fragile cake, depending on the fill volume used before drying.
Why peptides are supplied this way
- Stability. Hydrolysis needs water. A lyophilised peptide with residual moisture of a few percent has almost none available, so bond cleavage, deamidation and most oxidation are dramatically slowed. This is what allows storage for months to years at -20 C.
- Accurate dispensing. The manufacturer fills a known volume of solution of known concentration into each vial before drying, which is how a nominal 5 mg or 10 mg is achieved without weighing hygroscopic powder.
- Fast reconstitution. The porous cake has an enormous surface area, which is why most short peptides dissolve within a minute or two of adding diluent, without agitation.
- Shipping. A dry peptide tolerates days at ambient temperature in transit; a solution would not. See do peptides need to be shipped cold.
What the vial contains besides peptide
Lyophilised peptide is not 100% peptide by mass. The solid retains:
- Counter-ions from purification, most often acetate or trifluoroacetate (TFA), bound to the basic residues. See acetate versus TFA salt.
- Residual water, typically a few percent by mass.
- Sometimes bulking agents such as mannitol, added to give a robust cake for very low-mass fills. Alphex does not add bulking agents; what is in the vial is peptide, counter-ion and residual moisture.
The practical consequence is that the label mass is gross content. Net peptide content is usually 70-90% of gross depending on the sequence and salt form. For concentration-critical assays this matters; see net peptide content versus gross vial weight.
Handling a lyophilised vial
- The vacuum. Vials are sealed under partial vacuum. When you insert a needle, air is drawn in; if you have already drawn diluent into the syringe, it may be pulled in faster than you intend. Add slowly. A vial that has lost vacuum (the stopper is not domed inward, or no air rushes in on puncture) may have been compromised in transit; contact us before using it.
- The cake. It can look like a film, a shard, or loose flakes; all are normal. Some cakes shift or break up in transit, which does not affect the peptide.
- Condensation. Let the vial reach room temperature before opening. Cold cake plus warm humid air equals water on the peptide.
- Reconstitution. Diluent down the wall, no shaking; the full method is in how to reconstitute research peptides.
Frequently asked questions
Why does my 10 mg vial look empty?
Because 10 mg of freeze-dried peptide is a very small amount of a very low-density solid, and it may be a transparent film on the glass rather than a visible cake. Check the label and batch number, then reconstitute as normal.
Is lyophilised the same as spray-dried or air-dried?
No. Spray-drying and air-drying expose the peptide to heat and to liquid water during drying and are not used for research peptides of this kind.
Can I weigh out part of a vial?
Not accurately. The cake is hygroscopic and low-mass; reconstitute the whole vial and dispense by volume instead.
Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.
Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.
Published 12 May 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.