CAS Number
A unique numerical identifier assigned by the Chemical Abstracts Service to every chemical substance, providing an unambiguous way to identify compounds across languages and naming systems.
CAS numbers are the gold standard for chemical identification — a compound may have dozens of common names, brand names, or abbreviations, but its CAS number is invariant. When verifying the identity of a research peptide, cross-referencing the CAS number on a certificate of analysis (COA) against a trusted chemical database confirms you have the correct compound.
In peptide research, CAS numbers are particularly useful for distinguishing between closely related analogs. For example, different acetylated or amidated forms of the same peptide sequence will have different CAS numbers, reflecting their distinct chemical structures despite similar names.