Peptide nomenclature and CAS numbers

Why names multiply

Peptides pick up names for reasons rooted in how they're developed and sold, not because anyone's trying to obscure anything:

• Development codes are given by whoever first made or studied a compound, often before it has a settled generic name. CJC-1295 and PT-141 both started out as development codes.
• INNs (International Nonproprietary Names) are assigned later, to give a compound one standard generic name across languages and countries. A compound can carry both its original development code and its later INN at the same time.
• Descriptive short forms name a peptide by its amino acid sequence or a shared feature directly: KPV is simply the amino acids Lysine, Proline, and Valine; GHRP-2 places a compound in a numbered family sharing a similar structure.
• Market or vendor-specific nicknames, for blends especially (see the "Blends" group in the reference section), aren't standardized at all. The same nickname can mean different combinations from one seller to the next.

Why the CAS number is different

A CAS number is a unique number assigned to one specific chemical substance, permanently, by an organization called the Chemical Abstracts Service. Unlike a trade name, a development code, or a nickname, a CAS number is never reused and never changes, even if a compound is later renamed or rebranded. Two listings with the same CAS number describe the same substance, no matter what each one calls it. Two listings with different CAS numbers describe different substances, no matter how similar the names look.

Applying this when comparing listings

1. When comparing the same compound across sellers, check the CAS number on each listing or certificate, not just the product name.
2. Where a name is unclear on its own ("CJC-1295" without saying "no DAC" or "with DAC" is a common example), the CAS number settles which specific molecule is meant.
3. For a blend sold under a market nickname, the CAS number won't help, since a blend doesn't have one collectively. Compare the listed components and milligrams per vial instead.
4. For a coded compound, no CAS number or published structure exists at all, by design: identity there is established per lot on the certificate of analysis, not by a registry number. See each coded compound's reference entry for how that's handled.

Every single-compound entry in this reference section lists its CAS number alongside its amino acid sequence and formula for exactly this reason: it's the one identifier a name alone can't substitute for.