Reconstitution

Reconstitution is the process of dissolving a lyophilised peptide back into solution at the lab bench, ready for use in an experiment. Done correctly, it preserves the peptide's purity, identity, and biological activity; done carelessly, it can introduce contamination, partial degradation, or inconsistent concentrations across replicate experiments. The choice of solvent depends on the peptide and the downstream application. Sterile water (USP grade) is the simplest choice for short-term reconstitution and gives a clean, unbuffered solution. Bacteriostatic water (containing 0.9% benzyl alcohol) inhibits microbial growth and is suitable for multi-use vials over 1-28 days at 2-8°C, depending on the peptide's intrinsic stability. Specific buffers - PBS at pH 7.4, acetate at pH 4-5, ammonium bicarbonate for downstream MS - are chosen when the peptide's pI, solubility, or experimental context requires it. Some hydrophobic peptides require an initial dissolution in a small volume of DMSO or acetic acid before dilution into the working buffer. The volume to add is calculated to give the desired final concentration: dividing the labelled mass on the vial by the volume yields the concentration. Most labs aliquot the reconstituted solution into single-use volumes immediately, store the aliquots at -20°C or -80°C, and thaw one aliquot per experiment to avoid freeze-thaw degradation of the bulk stock. Document the reconstitution conditions in the lab notebook: solvent, volume, date, expected concentration, and any visual observations (cloudiness, precipitate, color). This documentation is essential for reproducibility and is often requested by reviewers when reporting peptide-based research.