What the label has to carry
Product name and, ideally, the sequence. Net mass in milligrams. Lot or batch number, which is what ties the vial to a certificate. Storage conditions. An expiry or retest date. A research use only statement where applicable.
The one field people overlook is the lot number, and it is the one that makes every other document about that vial usable. A vial with no lot number cannot be matched to a certificate at all.
The abbreviations worth knowing
Salt form abbreviations tell you how much of the weight is peptide. TFA is trifluoroacetate, AcOH or Ac indicates an acetate salt, HCl a hydrochloride. Their absence usually means TFA by default, since that is what reverse-phase purification produces.
Purity is normally given as a percentage with a method, HPLC being the usual one. Net peptide content, where present, may appear as NPC or peptide content. Lyophilised, often abbreviated to lyoph, means freeze-dried.
- •TFA: trifluoroacetate salt, the heaviest common counterion
- •AcOH or acetate: acetate salt, lighter and preferred for cell work
- •RUO: research use only
- •Lyoph: lyophilised, that is freeze-dried
- •MW: molecular weight, usually the free base
- •Lot or Batch: the identifier that matches the certificate
Mass on a label is not peptide in the vial
The milligram figure is the fill weight, which includes counterions, residual water and any impurities. A 10 mg vial does not hold 10 mg of peptide, and how far short it falls depends on the salt form and the purity.
Where a label states net peptide content as well as gross weight, the net figure is the one to use. Where it does not, the purity and net peptide content calculators estimate it from the certificate values.
Expiry, retest and storage
An expiry date is a statement that the material meets specification until that date under the stated storage conditions. A retest date is weaker: it says the material should be re-analysed by then rather than that it becomes unusable.
Both are conditional on the storage conditions printed alongside them. A vial stored warm has not had the shelf life its label describes, regardless of what the date says.
How the label decoder reads a label
Field by field, translating abbreviations and flagging what a given field does and does not establish.
- Identify the product and its sequence. The name alone is ambiguous for many research peptides, which trade under several names. A sequence or a molecular weight disambiguates it.
- Read the mass and check what it refers to. Gross fill weight or net peptide, and whether a salt form is stated. Without a salt form, the difference between the two is unknown.
- Locate the lot number. The field that ties the vial to a certificate. Everything documentary about the vial depends on it.
- Read the storage conditions and date together. An expiry date is conditional on the storage it names. The two fields are one statement, not two.
- Note the regulatory statement. Research use only means the material is not qualified for any other purpose, and it is a statement about qualification rather than a formality.
What this method cannot tell you
- •It reads what the label says. It cannot verify that the vial's contents match it.
- •Abbreviations are not standardised across suppliers, so an unfamiliar one may not decode.
- •A label is a summary. The certificate carries the analytical detail, and the two should be read together.
- •It cannot detect relabelling, which is the failure mode no document check catches.
Peptide label decoder: frequently asked questions
At minimum:
- •Product name, and ideally the sequence
- •Net or gross mass in milligrams
- •Lot or batch number
- •Storage conditions
- •Expiry or retest date
- •A research use only statement where applicable
Trifluoroacetate salt. It is the counterion left over from reverse-phase purification and the heaviest of the common ones, at 114 daltons per site.
It reduces peptide content relative to acetate and is cytotoxic in cell culture above roughly 0.1 percent.
Research use only. The material has not been qualified for any other purpose, which is a statement about what testing has been done rather than a legal formality.
Usually not. It is normally the gross fill weight, which includes counterions, residual water and impurities.
Where a label distinguishes net peptide content from gross weight, the net figure is the one to use for any calculation.
Because it is the link between the vial and its certificate. Without it, no analytical document can be tied to the material in your hand.
Freeze-dried: frozen and then dried under vacuum so the water sublimes directly from ice to vapour without a liquid phase.
It produces a porous cake that redissolves readily and is far more stable than a solution.
An expiry date says the material meets specification until then. A retest date says it should be re-analysed by then, without asserting that it has failed.
Retest dates are common for research chemicals, where a formal stability programme has not been run.
A temperature and usually a light and moisture instruction. Most lyophilised peptides specify minus 20 degrees Celsius, protected from light and moisture.
The expiry date is conditional on those conditions being met.
Assume TFA, since that is the default output of reverse-phase purification, and ask the supplier to confirm.
Assuming acetate when the material is TFA overstates peptide content by ten percentage points or more.
Ideally yes, though space often prevents it on small vials. Many research peptides trade under several names, and the sequence is what removes the ambiguity.
Where the label cannot carry it, the certificate should.
Molecular weight, normally of the free base rather than the salt. It is the figure to use in a molarity calculation, together with a mass corrected for salt content.
For a vial you labelled yourself with a recorded concentration and date, yes. For a supplied product, a handwritten label suggests a repackaging step with no traceability.
It gives you something to check against. Most lyophilised peptides are white to off-white powders or cakes.
A vial whose contents do not match the description is a reason to query, not to proceed.
Because they answer different questions. Gross is what was filled; net peptide is what is usable.
A label carrying both is unusually informative, and the net figure is the one to carry into calculations.
Yes. It carries the lot number, and once the vial is reconstituted the lot number is the only remaining link to the certificate.
The storage label generator prints a supplementary label with the reconstitution details, which is a complement to the original rather than a replacement.
Query it before using the material. The two documents describe the same batch and should agree on mass, purity and lot number.
A disagreement means at least one of them is wrong about the vial in front of you.
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