Explained
What are peptides?
Built from index records dated 2026-10-09 Compiled by an automated pipeline, checked by The Peptide Observer editorial desk How this site works
A peptide is a short chain of amino acids, which is a description of chemical structure and nothing more: it says nothing about what a substance does, whether anyone has studied it in people, or whether it is a medicine.
That first sentence is a general description of the word itself, not a value read off any record. Everything below it is counted from the records this site holds.
What we actually know
Chemical structure is something that can be measured, and for most entries here it has been. The scale below plots every described entry whose molecular weight was read from a public chemistry record. Heavier means a longer chain, and that is all it means.
| Entry | Molecular weight |
|---|---|
| Noopept | 318.4 g/mol |
| KPV | 342.43 g/mol |
| Epitalon | 390.35 g/mol |
| LL-37 | 4,493 g/mol |
| Thymosin beta 4 | 4,963 g/mol |
| FOXO4-DRI | 5,358 g/mol |
Of the 27 entries this site describes, 24 are classified as a peptide and 3 are not. The exceptions are Capromorelin, IGF-1 DES and IGF-1 LR3, kept here because the same searches and the same research literature cover them.
The index also carries entries that are not peptides at all. They are kept because the same research literature and the same searches cover them, and each one says on its own page that it is not a peptide.
What is not known
- What a compound does cannot be read off its structure. Two entries here can sit almost on top of each other on that scale and have nothing else in common.
- For many entries this index holds no amino-acid sequence, because no sequence database was queried when the records were gathered. An empty sequence row means nobody looked it up here, not that the compound has no sequence.
- The word peptide is used loosely in product marketing, including for substances that are not peptides. This site records the classification it can support from a chemistry record and marks the rest.
How to read this
- Every value on this site arrives with the record it came from. Where no record was retrieved, the page prints the word Unknown instead of an estimate.
- An Unknown is a statement about this site's records. It is never a statement about the compound.
Read next
Where this comes from
Molecular weights and formulas on this page were read from PubChem compound records. Each entry's own page lists the record its value came from.