Storage and handling of lyophilised peptides

Every Dohrna peptide is supplied as a lyophilised (freeze-dried) solid in a sealed glass vial. In that state a synthetic peptide is a stable material, and keeping it that way is mostly a matter of temperature, moisture and light. This page sets out the conditions under which the sealed vial should be kept, and the handling steps that keep it in the condition the certificate describes. It concerns the material as supplied; what a laboratory does with it after the seal is broken is governed by that laboratory's own procedures.

As supplied

The vial contains a dry powder — usually white to off-white — sealed under a crimped cap with a rubber septum. The mass on the label is the nominal fill. Lyophilised peptides are hygroscopic: they take up water from the air, which is why the seal matters and why the vial should stay closed until the material is needed.

The storage line on each product page states the supplier's condition for that line, where the supplier's specification has been published. Where it is stated, it governs; where it is still shown as outstanding, the general practice below applies, and the specification is added as the supplier issues it.

Temperature

For the sealed vial, colder is better and stable is better than cold.

• Long-term: −20 °C is the usual condition for a lyophilised peptide, and most lines are stable for years at that temperature in the sealed vial. Some are specified for −80 °C; the product page says so where that applies.
• Short-term: 2–8 °C (an ordinary laboratory refrigerator) is acceptable for weeks. It is appropriate for a vial that will be opened soon, and it is the condition the material is likely to have travelled in.
• Room temperature: tolerable for the days of transit, and for the short time a vial spends on a bench. Not a storage condition.

Repeated warming and cooling is worse than either temperature alone. A vial that is taken from the freezer, allowed to warm, and returned, several times over, accumulates condensation with each round. Where a line will be used in several portions over a long period, the usual practice is to divide the material once, into portions that are each opened once.

Moisture

Moisture is the main thing that degrades a lyophilised peptide in storage. Two habits deal with most of it:

• Let a cold vial reach room temperature before opening it. A vial opened straight from the freezer draws condensation onto the powder as warm laboratory air meets cold glass. Fifteen to thirty minutes on the bench, seal intact, avoids this.
• Keep the vial in a container with desiccant where the storage environment is humid or the vial will be opened more than once.

A vial whose powder has become sticky, clumped or visibly wet has taken up water. The material may still be identifiable, but the mass on the label no longer describes the dry peptide.

Light

Peptides containing tryptophan, tyrosine, methionine or cysteine are the ones most affected by light and by oxidation. A vial kept in its box, or in an opaque container, is protected. A vial left on a lit bench for an extended period is not.

In transit

Dohrna ships lyophilised material at ambient temperature, which is standard practice for peptides in this form: the days of transit are within the range the material tolerates. Where a line requires cold-chain carriage, the product page says so and the consignment is carried accordingly — the delivery policy states the shipping condition.

On receipt, the vial should go into its storage condition without delay. The label and the certificate should be kept together; the lot number on the label is what ties the vial to its certificate.

What the expiry date means

The expiry date on the label is the end of the period for which the laboratory's data support the certificate's figures, under the stated storage condition. It applies to the sealed vial. A vial that has been opened, or stored outside its condition, may not reach it; a vial stored correctly may still be identifiable after it. After the expiry date the certificate no longer describes the contents and the material should be re-analysed before it is relied on.

Handling summary

The Safety Data Sheet for each line, available from the documentation centre, states the hazard classification and the handling precautions that apply to the material itself; this page is about keeping the material in specification, not about protecting the person handling it, and the Safety Data Sheet governs on the latter.