Research Peptide Glossary

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Aliquot: A measured portion divided out from a larger volume, usually so the stock is thawed only once. · Lab Practice
Amino Acid: The building blocks of peptides; each unit in an assembled chain is called a residue. · Fundamentals

Bacteriostatic Water: Sterile water containing 0.9% benzyl alcohol, which inhibits bacterial growth and so allows a vial to be entered more than once. · Lab Practice

CAS Number: A unique registry identifier assigned to a chemical substance by the Chemical Abstracts Service. · Fundamentals
Certificate of Analysis: The per-batch document reporting what a compound was tested for, by which method, and what the results were. · Lab Practice

Freeze–Thaw Cycle: One round of freezing and thawing a solution; repeated cycles are a common cause of degradation. · Lab Practice

HPLC: High-performance liquid chromatography — the separation technique behind the purity percentage on a certificate of analysis. · Lab Practice

In Vitro: Latin for “in glass” — work performed outside a living organism, such as in cell culture or a cell-free assay. · Fundamentals

Lyophilization: Freeze-drying: water is removed from a frozen solution under vacuum so the remaining solid can be stored dry and reconstituted later. · Lab Practice

Mass Spectrometry: Measures mass-to-charge ratio to confirm a compound's molecular weight — the usual evidence for identity rather than purity. · Lab Practice
Molarity: Amount of substance per unit volume, in moles per litre — the concentration unit that is comparable between compounds. · Lab Practice
Molecular Weight: The mass of one mole of a compound, in grams per mole — what converts a mass concentration into a molar one. · Fundamentals

Peptide: A chain of amino acids joined by peptide bonds — shorter than a protein, with no sharp boundary between the two. · Fundamentals
Peptide Content: The fraction of a lyophilized solid's mass that is actually peptide, the rest being counter-ions and bound water. · Lab Practice
PubChem: The NIH's public chemical database; a PubChem CID identifies one specific compound record. · Fundamentals
Purity: The proportion of a sample that is the intended compound, as measured by a stated analytical method. · Lab Practice

Reconstitution: Dissolving a lyophilized solid back into liquid by adding a measured volume of diluent. · Lab Practice
Research Use Only: A designation restricting a material to laboratory and in-vitro research — not for human or veterinary use, diagnosis or treatment. · Fundamentals

Sequence: The order of amino acid residues in a peptide, conventionally written from the N-terminus to the C-terminus. · Fundamentals

Third-Party Testing: Analysis performed by a laboratory independent of the seller and the manufacturer. · Lab Practice