Peptide Storage

Start from the lyophilised powder

Freeze-dried peptide is supplied as a stable powder, and it stays that way as long as it is kept dry, dark, and cool. Store tightly sealed to limit moisture uptake, and protect from light. Standard laboratory practice for lyophilised peptides is frozen storage — commonly around -20 °C for shorter-term keeping and -80 °C for longer-term archival. Because individual sequences differ in stability, follow any lot-specific guidance where given.

The most common avoidable error

Opening a vial taken straight from the freezer. Cold surfaces condense atmospheric water, and that moisture enters the powder, accelerating degradation and making subsequent weighing inaccurate. Always let the sealed vial equilibrate to room temperature before opening it.

Aliquot rather than reuse one vial

Repeated freeze-thaw cycles are a practical source of loss. Where a batch will be used across multiple experiments, divide it into single-use aliquots shortly after receipt — either as weighed powder portions or as aliquots of reconstituted solution frozen immediately. Then each experiment draws a fresh aliquot and the rest remain undisturbed.

Reconstituted solution

Peptide in solution is considerably less stable than peptide as powder. General practice is to prepare solution close to the time of use, aliquot it, freeze the aliquots, and thaw only what is needed for one session. Repeatedly warming and refreezing the same tube is what tends to cause trouble.

Sequences needing additional care

Cysteine-containing peptides can form disulfide bonds on standing in solution, particularly at non-acidic pH. Methionine and tryptophan are oxidation-sensitive; limiting exposure to air and light helps, and for particularly sensitive work an inert atmosphere is sometimes used. These are handling considerations rather than defects, and they explain why two otherwise similar peptides may age differently.

Containers and surfaces

Use clean, low-binding tubes for dilute solutions, since peptide can adsorb to vessel walls and to some filter membranes — a loss that becomes proportionally larger as concentration falls. When filtering dilute solutions, consider whether recovery should be verified.

Keep a simple record

Note the lot number, the date received, the date reconstituted, the solvent used, and how aliquots were stored. This takes moments at the time and becomes valuable when reconciling results across experiments or reordering material months later.