Excipient
Definition
Anything in a formulation other than the active substance: bulking agents, buffers, preservatives, stabilisers. Excipients decide how a cake looks and how well it redissolves, and they appear on an approved label alongside the active.
What this means for research sourcing
Getting this right matters when preparing lyophilized research peptides for in vitro work. Volta ships compounds as lyophilized powder for reconstitution.
Related Terms in Preparation
Mannitol
A sugar alcohol used as a bulking agent and cryoprotectant in freeze-dried formulations. It gives the cake its visible structure and shields the peptide during drying, so a vial that looks empty often simply has no mannitol in it.
Peptide Blend
One vial holding two or more compounds pre-mixed at a fixed ratio by the supplier, as against a set of single-compound vials, where each compound has its own vial. A blend's certificate reports each component separately and states no single purity for the vial.
Enteric Coating
A polymer film on a capsule or tablet that holds together in stomach acid and dissolves at the higher pH of the small intestine. Oral peptide formulations use it to get past gastric proteases, with limited success for anything but short sequences.
Cold Chain
The unbroken temperature-controlled path a material travels from manufacture to storage. Lyophilised peptide is typically held at -20C and solutions at 2 to 8C, and a break in the chain is not visible in the vial afterwards, which is why shipping records matter.
Sonication
Applying ultrasound to a liquid to speed dissolution or disperse aggregates. It appears in laboratory sample-preparation procedures, and prolonged or vigorous application can itself degrade a sensitive peptide.
Sterile Water
Water that has been sterilised and contains no preservative. Nothing in it inhibits growth once the container is opened, which is the single difference from a preserved solvent and the reason the two are not interchangeable.
Reconstitution
Returning a freeze-dried peptide to solution by adding a measured volume of solvent. The volume chosen is what sets the concentration, so one vial can yield many different concentrations and the arithmetic belongs with the record of the experiment.
Concentration
How much peptide sits in a unit of liquid, written as mg/mL or mcg/mL. It is a consequence of the vial contents and the solvent volume added, and nothing else, which is why it has to be recalculated whenever either changes.
