Reading time: ~2 min · Part of the free certification in peptide science
Most peptides come lyophilized (dehydrated by vacuum sublimation) because the dry solid state maximizes their stability. Lyophilization may include cryoprotective excipients (such as mannitol) that give body to the cake and protect the molecule during the process.
Choosing the diluent
Reconstituting means returning the lyophilizate to solution. Choosing the diluent is not trivial:
- Bacteriostatic water: sterile water with 0.9% benzyl alcohol, which inhibits microbial growth and allows multiple uses of the vial. It is the usual choice for multi-dose vials.
- Sterile water for injection: without preservative; suitable for immediate or single-dose use.
- Dilute acetic acid or other vehicles: some poorly soluble peptides at neutral pH require a slightly acidic vehicle to dissolve completely, given their dependence on pH and the isoelectric point (Module 1).
A peptide's solubility depends on its pI and its balance of residues. A peptide that tends to aggregate or precipitate near physiological pH may require a specific diluent. Checking that the solution is clear after reconstitution is the practical test of correct dissolution.
Catalogue compounds mentioned in this lesson
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