How should a retatrutide reference record define sequence, lipidation, and molecular form?

Answer first

A retatrutide record should identify the 39-residue backbone and each structural modification before an expected mass is assigned. The reviewed public records distinguish a sodium-salt compound entry from the active molecular entity and locate the C20 fatty-diacid side chain at Lys17, so the form and mass basis must travel with every result.

Reviewed Chemical LedgerRetatrutide

Molecular form representedRetatrutide sodium-salt record represented by PubChem CID 171934787

Molecular formula: C221H342N46O68
Average molecular weight: 4731 g/mol average molecular weight
Exact mass: 4730.4784689 Da

Reviewed peptide designation39-residue retatrutide backbone with non-coded residues, Lys17 C20-diacid lipidation, and C-terminal amide

Sequence representationIncludes stated terminal and modification notation

Y-Aib-QGTFTSDYSI-alpha-MeLeu-LDK-K17[gamma-Glu-AEEA-C20 diacid]-AQ-Aib-AFIEYLLEGGPSSGAPPPS-NH2

Structural notes

Aib at positions 2 and 20 of the 39-residue backbone record
Alpha-methyl-leucine at position 13
C20 fatty diacid side chain linked at Lys17
C-terminal serinamide

Salt or counter-ion scopeSodium-salt database record; project-specific sodium stoichiometry must be documented separately

Known Aliases / Code Names:RetatrutideLY3437943LY-3437943

Field-level sources

PubChem CID 171934787: Retatrutide (sodium salt)

National Library of Medicine / PubChem · accessed 2026-08-03

Supports: name, molecularForm, formula, weight, exactMass, saltForm

FDA GSRS Retatrutide sodium record

FDA / NCATS Global Substance Registration System · accessed 2026-08-03

Supports: sequence, peptideDesignation, modifications, aliases

Where this framework helps

Building an expected-mass record for an engineered peptide
Comparing identity evidence when salt or counter-ion wording differs
Planning sequence mapping around non-coded residues and a lipidated lysine

Limits to keep visible

The sodium-salt record is not a substitute for lot-specific counter-ion measurement.
A backbone sequence alone does not encode the side-chain structure or terminal chemistry.
This dossier does not discuss clinical use, outcomes, administration, or purchasing.

Name the exact molecular form

Record whether a calculation refers to the active entity, a sodium-salt representation, or another material form. Formula, expected average mass, exact mass, and counter-ion accounting must use the same basis.

Keep backbone and modifications in one identity map

The GSRS record provides a 39-residue backbone and modification detail, while structural literature identifies lipidation at Lys17. Sequence evidence should therefore cover the backbone and explicitly address Aib, alpha-methyl-leucine, the linker, the C20 diacid, and the terminal amide.

Assign methods to unresolved questions

Intact mass can test agreement with the selected molecular form. Peptide mapping or fragment evidence is needed when the research question requires modification-site or sequence localization, and composition testing is separate from either conclusion.

Primary and official sources

References used for this page

FDA GSRS validated Retatrutide sodium substance recordFDA / NCATS Global Substance Registration System
Structural insights into triple agonism manifested by retatrutideCell Discovery / PubMed

Visible FAQ

Questions research teams ask

Why is a plain one-letter sequence incomplete for retatrutide?

It omits the non-coded residues, Lys17 side chain, linker, fatty diacid, and terminal amide. Those features change both identity and expected mass.

Can the sodium-salt title be applied to every retatrutide sample?

No. It identifies the reviewed database record. A project sample needs its own declared form and composition evidence before that label is used.

Which result can localize the Lys17 modification?

A whole-molecule mass match does not automatically localize the side chain. Localization requires an appropriate mapping or fragment workflow with interpretable coverage around the modified residue.