Lyophilized

A lyophilized product has been freeze-dried: the peptide solution is frozen and the water is then drawn off by sublimation under vacuum, without heat, leaving a dry cake or powder behind in the vial. Nearly all research peptides in injectable-style vials are supplied like this, because peptide bonds hydrolyse and side chains oxidise much more quickly in solution than in the dry solid.

Reading the cake

The look of the cake is informative. A solid, even, white cake occupying the expected volume indicates that freeze-drying stayed below the collapse temperature. A shrunken, glassy or seemingly melted puck points to collapse — typically due to a shelf that was too warm or a vacuum failure — and a lot delivered in that state should be checked against its certificate of analysis. A little loose powder, or a cake that has moved during transport, is purely cosmetic and quite normal.

The reference state for storage

Freeze-dried material is the baseline for storage and handling. Sealed dry vials cope with long periods in the fridge or freezer and with brief spells at ambient temperature during shipping; after reconstitution, degradation proceeds much faster. Bulking agents like mannitol are sometimes added as excipients to create a visible cake when peptide mass is low, which explains why a 2 mg vial may appear fuller than you expect.

Related terms

reconstitution · stability · cold chain. Read what lyophilization is and how to store peptides, or browse lyophilized peptide vials.