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

Selank

129954-34-3

Compound B

Semax

80714-61-0

Observed mass from a COA

Not the same molecule

Both are heptapeptides with a PGP tail. Different N-terminal sequences.

Peptide

Selank

View specs

CAS: 129954-34-3
Formula: C33H57N11O9
Catalog mass: 751.89 Da
Sequence avg: 751.88 Da
Monoisotopic: 751.4341 Da
Sequence: Thr-Lys-Pro-Arg-Pro-Gly-Pro

Expected ions

[M+H]+

752.4414

[M+2H]2+

376.7243

[M+3H]3+

251.4853

Presentations

Nasal spray

COA documents PubChem CID 11765600

Often confused with

Semax

Peptide

Semax

View specs

CAS: 80714-61-0
Formula: C35H52N12O9
Catalog mass: 813.93 Da
Sequence avg: 813.93 Da
Monoisotopic: 813.3480 Da
Sequence: Met-Glu-His-Phe-Pro-Gly-Pro

Expected ions

[M+H]+

814.3553

[M+2H]2+

407.6813

[M+3H]3+

272.1233

Presentations

Nasal spray

COA documents PubChem CID 9811102

Often confused with

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.