Lab tools

Peptide identity index

The peptide identity index tells you whether two names used for research peptides refer to the same molecule. Look up a catalog name, a CAS number, or an alias. Compare a second name when a vial, a paper, or a COA uses a different label.

Mass values computed from sequence are for checking an HPLC-MS report. This page does not calculate reconstitution volumes or human doses. Pair it with a lot-linked Certificate of Analysis and the 12-point COA audit.

Compound A

Melanotan 1

75921-69-6

Compound B

Melanotan 2

121062-08-6

Observed mass from a COA

Not the same molecule

Linear tridecapeptide versus a shorter cyclic analog.

Peptide

Melanotan 1

View specs

CAS: 75921-69-6
Formula: C78H111N21O19
Catalog mass: 1,646.85 Da
Sequence avg: 1,646.87 Da
Monoisotopic: 1,645.8365 Da
Sequence: Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2

Expected ions

[M+H]+

1,646.8438

[M+2H]2+

823.9255

[M+3H]3+

549.6194

COA documents PubChem CAS search

Often confused with

Melanotan 2

Peptide

Melanotan 2

View specs

CAS: 121062-08-6
Formula: C50H69N15O9
Catalog mass: 1,024.18 Da
Sequence avg: Not computed
Monoisotopic: Not computed
Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2

Sequence notation is too modified to compute ions here. Use the catalog mass and the COA report together.

COA documents PubChem CAS search

Often confused with

Melanotan 1

How the index decides

Catalog CAS, formula, and sequence come from Tetrava lot identity tables. Monoisotopic mass and expected ions are calculated only when the sequence parses as standard residues plus common caps (acetyl, amide, Aib, Nle, pGlu). Heavily modified GLP-1 analogs stay as catalog text.

TB-500 is the main trap. Supplier tables often reuse the CAS and 4,963 Da mass of full-length thymosin beta-4 on a vial whose sequence is Ac-LKKTETQ. This index splits those identities on purpose.

Research use only. Not for human or veterinary consumption.