Almost every research peptide on Peptide Shop ships as a lyophilised (freeze-dried) cake in a sealed glass vial. This article explains why, what changes the moment the vial is reconstituted, and the narrow set of cases where a liquid formulation is preferable.
What lyophilisation does
Lyophilisation (freeze-drying) removes water from the formulation under vacuum at low temperature. The end product is a porous solid cake of peptide plus a small amount of buffering or bulking agent (often acetate, mannitol, or trehalose). With water removed:
- Hydrolysis of labile peptide bonds is dramatically slowed.
- Aggregation kinetics drop by orders of magnitude.
- Microbial growth is suppressed (water activity below 0.6 prevents most growth).
- Shipping at ambient temperature becomes feasible for the short transit window.
A correctly lyophilised research peptide stored at −20 °C is typically stable for 24 months from manufacture.
What changes on reconstitution
The moment diluent enters the vial, every degradation pathway re-activates:
| Pathway | Lyophilised | Reconstituted |
|---|---|---|
| Backbone hydrolysis | negligible | seconds–weeks, pH-dependent |
| Met oxidation | very slow | hours–days in air |
| Cys disulfide scrambling | very slow | minutes–hours at neutral pH |
| Asn deamidation | slow | days–weeks |
| Trp photo-oxidation | requires light | requires light |
| Aggregation | very slow | minutes–weeks, sequence-dependent |
Reconstituted shelf life therefore drops from years to days–weeks. Storage protocols change accordingly (see storage & handling).
Why we ship lyophilised
- Stability in transit. A 48-hour international shipment at ambient temperature is non-trivial for a liquid formulation; the lyophilised cake survives easily.
- Concentration flexibility. A single 5 mg vial can be reconstituted to anywhere from 0.5 mg/mL to 10 mg/mL depending on the assay.
- Diluent flexibility. The user picks the diluent appropriate to the assay (water, BAC water, PBS, DMSO).
- Shelf-life economics. A 24-month shelf life on a lyophilised lot supports lab planning; a 5-day liquid formulation does not.
When liquid makes sense
A pre-reconstituted, liquid research peptide can be appropriate when:
- The assay is run at a fixed concentration in a defined diluent and runs daily over a short window.
- The peptide is stable in solution for months (some short, hydrophilic, non-Met/Cys/Trp sequences).
- The end-user does not have a
−20 °Cfreezer near the bench.
If you have a project with a recurring concentration requirement and want a liquid format, contact the technical team. Custom liquid formulations are case-by-case.
Practical implications
- Treat every newly reconstituted vial as having a fresh shelf-life clock that starts at first diluent contact.
- Aliquot immediately rather than re-opening a stock vial repeatedly.
- Record the reconstitution date and diluent on every aliquot label.