Safety in the Lab: Handling and Storage Fundamentals

Why peptides degrade

Peptides are held together by bonds that water, heat and enzymes can break. In the dry, lyophilised state they are relatively robust. Exposed to moisture, warmth or light they begin to change. Several processes are at work.

• Hydrolysis. Water slowly cleaves peptide bonds. Warmth accelerates it.
• Oxidation. Certain amino acids (methionine, cysteine, tryptophan) react with oxygen and light.
• Aggregation. Some sequences clump together over time, which changes their behaviour in an assay.
• Adsorption. Peptides stick to plastic and glass surfaces, so a fraction of a sample can end up on the container rather than in it.
• Microbial growth. Any moisture that reaches an unpreserved sample invites contamination.

Lyophilised material

Freeze-dried peptide arrives as a powder or a thin cake at the bottom of a sealed vial. In this state the main enemies are moisture and heat. Standard laboratory practice is to store sealed vials cold, protected from light, and to let a vial reach room temperature before opening so condensation does not form on the cold powder. Manufacturers publish stability data for their own products and that data should take precedence over any general rule.

Storage conditions

Stability is mostly a matter of environment. Laboratories protect material with a few consistent habits.

• Store sealed vials in a dedicated, temperature-controlled unit that is not used for food or anything else.
• Keep material in the dark. Amber containers or an opaque box inside the storage unit both work.
• Minimise temperature swings. Every time a sample warms and cools it loses a little integrity.
• Label every container with compound, lot number, receipt date and storage location.
• Discard material on the schedule the manufacturer's stability data supports rather than guessing.

Personal and lab safety

Bioactive compounds deserve the same respect as any other laboratory reagent. Standard measures include gloves and eye protection, working in a clean and dedicated space, keeping materials away from food or drink, and disposing of waste through the proper channels. Material safety information from the supplier should be on file and read before handling.

Record keeping

A stability problem that is not written down is a stability problem that will be repeated. Good labs log lot numbers, receipt dates, storage locations and every time a sample leaves controlled storage. When a result looks strange the log is often where the explanation lives. It is also the backbone of any claim that an experiment was done properly.