Storing research peptides without ruining them

Most peptide loss in a research setting is not caused by shipping or by the supplier. It happens quietly, in a freezer, over weeks, because lyophilised and reconstituted material were treated the same way.

Lyophilised powder

In its freeze-dried state a peptide is remarkably stable. The enemies are moisture and repeated temperature swings, not time.

• Keep vials sealed and dry. Let a vial reach room temperature before opening it — opening a cold vial pulls humid air onto cold glass and condenses water directly onto the powder.
• −20 °C is appropriate for long-term storage of most sequences; −80 °C extends it further.
• Protect from light. Tryptophan, tyrosine, methionine and cysteine residues are the ones that notice.

After reconstitution

In solution the clock starts. Hydrolysis, oxidation and adsorption to the container all begin immediately.

• Store at 2–8 °C for short-term work, and plan in days rather than months.
• Aliquot before freezing. Every freeze–thaw cycle costs material. One vial thawed twenty times is twenty insults to the same peptide; twenty aliquots thawed once each is one.
• Use bacteriostatic water where the protocol calls for repeated withdrawals, and sterile water where it does not.
• Glass or low-binding polypropylene. Standard plastic adsorbs peptide out of dilute solutions, which shows up as a potency problem that is really a surface problem.

Sequences that need extra care

Peptides containing cysteine can form disulfide bridges in solution. Methionine oxidises. Asparagine and glutamine deamidate, and the rate depends on pH. If a sequence contains these residues, shorter solution storage and a buffered diluent matter more than the freezer temperature does.

A practical routine

1. Log the batch number and the date the vial arrived.
2. Warm to room temperature before the first opening.
3. Reconstitute, mix gently — do not shake, which shears and foams.
4. Aliquot into single-use volumes.
5. Label every aliquot with compound, concentration, diluent and date.

The labelling step is the one people skip and the one that invalidates the most work.

Research use only. Not for human or veterinary use.