The same molecule routinely appears under a code number, a chemical description, an international non-proprietary name and two or three informal abbreviations. None of them is wrong, and they are not synonyms in the way they look — each comes from a different naming system with different rules about what counts as the same substance. When two names sit close together but not identically, the difference is usually real.
Where the names come from
| Name type | Assigned by | What it pins down | Example shape |
|---|---|---|---|
| Development code | The originating laboratory | A project, not always one molecule | CJC-1295, BPC-157 |
| Sequence description | Convention | Residues and modifications | Modified GRF (1–29) |
| INN / generic | WHO | One substance, with a class suffix | Tesamorelin, semaglutide |
| Informal abbreviation | Usage | Whatever the community means by it | GHRP-6, TB-500 |
The suffixes on generic names are not decorative. -tide marks a peptide; -relin a releasing-hormone analogue; -glutide a GLP-1 analogue. A name ending in -glutide is telling you its class before you look anything up, which is more than a development code does.
Why does one molecule need four names?
Because the naming systems answer different questions and were never reconciled. A development code identifies a programme inside a company, and programmes can cover more than one molecule. A sequence description identifies a structure and changes if the structure changes. An INN identifies a regulated substance and is granted once. An informal abbreviation records what people actually say. The four coexist because none of them was designed to replace the others, and the collisions between them are where the confusion lives.
What is the difference between CJC-1295 with and without DAC?
They are different molecules, and this is the clearest case of one code covering two substances. Both are based on a modified GRF(1–29) sequence. The version with DAC — Drug Affinity Complex — carries a reactive linker that binds covalently to serum albumin, which extends its half-life dramatically. The version without it is the modified sequence alone, with a half-life of minutes to hours rather than days.
Because both are called CJC-1295, a citation using the bare code is ambiguous and the ambiguity is consequential: the two differ in duration by orders of magnitude. The no-DAC form is also widely sold as "Modified GRF (1–29)" or "CJC-1295 DAC-free" — three labels for one molecule. It is the form carried here, in co-formulated products rather than on its own. Where a paper says only CJC-1295, the first job is establishing which one it studied.
The traps worth knowing
A code can cover a family. As above. A development programme may produce several analogues that all carry the project number in informal use.
A fragment inherits the parent's name. TB-500 is routinely called thymosin β4, and it is a seven-residue piece of a 43-residue protein. The same applies to Semax, which is built from an ACTH fragment and does not behave like ACTH. Findings about a parent protein do not transfer to a fragment without an argument.
Salt form is often left off. "Acetate" and "trifluoroacetate" describe the same peptide with a different counter-ion, and dropping the suffix hides a difference in how much of the vial is peptide.
Blends get portmanteau names. A co-formulated product may be named for its components in a way that says nothing about the ratio, which is a property of the product rather than of the name.
How can I be sure two names refer to the same molecule?
By checking the sequence and the modifications, not the name. A one-letter or three-letter sequence, plus any modifications — acylation, amidation at the C-terminus, acetylation at the N-terminus, substituted residues — identifies a molecule unambiguously in a way no name does. Where a sequence is not available, the CAS registry number is the next best identifier, because it is assigned per substance rather than per programme. Two products with the same CAS number are the same substance; two with the same trade name may not be.
Does an amidated C-terminus count as a different peptide?
Yes. Replacing the terminal carboxyl with an amide removes a negative charge and changes the mass by one unit, and for many sequences it substantially changes stability against exopeptidases. It is a genuinely different molecule that is often described with the same name plus a small suffix, or with no suffix at all. A mass on a certificate that sits one dalton off the value you calculated is usually this rather than an error — and the identity panel is where that gets settled.
Why do blends have names that do not list their contents?
Because they are product names rather than chemical ones. A blend name is a label for a particular combination at a particular ratio, and neither the components nor the proportion is recoverable from it. The ratio is the property that matters and is fixed at manufacture, so the only reliable source is the certificate, which should report each component independently — a combined figure answers nothing. A name is a convenience for ordering, not a specification.
Which name should a methods section use?
Enough of them to remove ambiguity, which usually means more than one. The generic or INN name where one exists, the sequence with its modifications, the salt form, and the supplier with the lot number. That combination lets a reader identify exactly what was used and, if the supplier publishes certificates by lot, check its characterisation independently. A methods section naming only a development code has described a programme rather than a molecule, and has made its own result harder to reproduce than it needed to be.
All products referenced here are supplied for laboratory and research use only. They are not drugs, foods, supplements or cosmetics, and are not for human or veterinary use.
