Compound reference
Research peptide molecular weight and CAS number reference table
Published 2026-10-29 · updated 2026-10-29 · vendor-authored explanatory note
Short answer
This table lists PubChem's computed molecular formula and average molecular weight, the CAS registry number, and the PubChem compound ID (CID) for 24 compounds. A compound appears only when the CAS number PubChem holds matches the catalog CAS number, so two independent sources agree. Values describe the reference compound; the identity, purity, and quantity of a specific lot come only from that lot's certificate of analysis.
| Compound | Molecular formula | MW (g/mol) | CAS | PubChem | Catalog |
|---|---|---|---|---|---|
| Acetyl octapeptide-3 | C41H70N16O16S | 1075.2 | 868844-74-0 | CID 76283482 | Lot documentation |
| Afamelanotide (Melanotan-1) | C78H111N21O19 | 1646.8 | 75921-69-6 | CID 16197727 | Lot documentation |
| AOD-9604 | C78H123N23O23S2 | 1815.1 | 221231-10-3 | CID 71300630 | Lot documentation |
| BPC-157 | C62H98N16O22 | 1419.5 | 137525-51-0 | CID 9941957 | Lot documentation |
| Bremelanotide | C50H68N14O10 | 1025.2 | 189691-06-3 | CID 9941379 | Lot documentation |
| Cibinetide (ARA-290) | C51H84N16O21 | 1257.3 | 1208243-50-8 | CID 91810664 | Lot documentation |
| Delta sleep-inducing peptide | C35H48N10O15 | 848.8 | 62568-57-4 | CID 68816 | Lot documentation |
| Elamipretide (SS-31) | C32H49N9O5 | 639.8 | 736992-21-5 | CID 11764719 | Lot documentation |
| Epitalon | C14H22N4O9 | 390.35 | 307297-39-8 | CID 219042 | Lot documentation |
| Examorelin (hexarelin) | C47H58N12O6 | 887.0 | 140703-51-1 | CID 6918297 | Lot documentation |
| Glutathione | C10H17N3O6S | 307.33 | 70-18-8 | CID 124886 | Lot documentation |
| Ipamorelin | C38H49N9O5 | 711.9 | 170851-70-4 | CID 9831659 | Lot documentation |
| LL-37 | C205H340N60O53 | 4493 | 154947-66-7 | CID 16198951 | Lot documentation |
| Melanotan II | C50H69N15O9 | 1024.2 | 121062-08-6 | CID 92432 | Lot documentation |
| Nadide (NAD+) | C21H27N7O14P2 | 663.4 | 53-84-9 | CID 5892 | Lot documentation |
| Oxytocin | C43H66N12O12S2 | 1007.2 | 50-56-6 | CID 439302 | Lot documentation |
| Pralmorelin (GHRP-2) | C45H55N9O6 | 818.0 | 158861-67-7 | CID 6918245 | Lot documentation |
| Prezatide copper (GHK-Cu) | C14H23CuN6O4+ | 402.92 | 89030-95-5 | CID 71587328 | Lot documentation |
| Semaglutide | C187H291N45O59 | 4114 | 910463-68-2 | CID 56843331 | Lot documentation |
| Semax (ACTH 4-7 Pro-Gly-Pro) | C37H51N9O10S | 813.9 | 80714-61-0 | CID 9811102 | Lot documentation |
| Sermorelin | C149H246N44O42S | 3357.9 | 86168-78-7 | CID 16132413 | Lot documentation |
| Tesamorelin | C221H366N72O67S | 5136 | 218949-48-5 | CID 16137828 | Lot documentation |
| Thymalfasin (thymosin alpha-1) | C129H215N33O55 | 3108.3 | 62304-98-7 | CID 16130571 | Lot documentation |
| Tirzepatide | C225H348N48O68 | 4813 | 2023788-19-2 | CID 166567236 | Lot documentation |
How to use this table
Molecular weight is needed to convert a mass into an amount of substance (moles), for example when preparing a stock solution of known molarity for an in-vitro assay, or when predicting the m/z values an LC-MS identity check should show.
PubChem's molecular weight is the average (isotope-weighted) mass computed from the molecular formula. High-resolution mass spectrometry compares against the monoisotopic mass instead, which PubChem lists separately on each compound page.
Why a CAS match matters
Peptide trade names are often reused for different sequences, salt forms, or modifications. A CAS number pins down one registered substance. When a supplier's CAS number, the name, and the PubChem record all agree, a reader can be more confident that the documentation refers to the compound they expect.
Compounds whose catalog CAS number does not match PubChem, or that PubChem does not list by name, are left out of this table rather than guessed.
Salt forms and net peptide content
Lyophilized peptides are usually supplied as salts (for example acetate or trifluoroacetate) and contain residual water, so the weighed powder is not 100% peptide. A certificate that reports net peptide content lets a laboratory correct the weighed mass before calculating concentration.
Related on Vitality Chems
- Stock solution and molarity calculator — uses these molecular weights.
- Expected LC-MS m/z calculator — charge-state values from the same data.
- Peptide COA checklist — what a lot certificate must show.
- Verify a lot — look up a published lot report by lot number.
Frequently asked
Where do these molecular weights come from?
From PubChem (National Library of Medicine), retrieved on 2026-10-29 through the PUG REST API. They are PubChem's computed average molecular weights in g/mol.
Is the molecular weight on a COA the same as PubChem's?
It should agree with the reference value for the free compound. Small differences can come from rounding or from reporting a salt form; a large difference is worth asking the supplier about.
Why is a compound I expected missing?
It is listed only when PubChem's CAS number matches the catalog CAS number. Compounds without a matching PubChem record are omitted rather than estimated.
Can I cite this table?
Yes. Cite PubChem for the values (each row links to its CID) and this page for the compiled cross-check.
References
- PubChem (National Library of Medicine)Source of molecular formula, molecular weight, CAS and CID.
- PubChem PUG REST documentationProgrammatic access used to retrieve the values.
