Selank vs Semax: Siblings, Not Twins

Both molecules end in Pro-Gly-Pro. That tripeptide tail is not incidental biology; it was added deliberately, because short peptides are cleaved quickly by aminopeptidases and the PGP terminus slows that down. It is the reason both compounds exist as usable research materials rather than as sequences that disappear on contact with plasma. It is also the reason the two look superficially related when they are not.

Selank is built on tuftsin, a four-residue fragment (Thr-Lys-Pro-Arg) of the heavy chain of immunoglobulin G. Its origin is therefore immunological, and a good part of the literature on it reports immune-marker and cytokine effects alongside the behavioural work.[2]

Semax is built on ACTH(4-7), a fragment of adrenocorticotropic hormone stripped of the hormone's endocrine activity. Its origin is neuroendocrine, and the published work on it centres on cognition and neuroprotection, including regulation of BDNF and its receptor in the rat hippocampus.[4]

One is an immune fragment stabilised for the brain; the other is a hormone fragment stabilised for the brain. That difference in ancestry is what shows up in what each literature measures.

Amino Acid Sequence

Amino Acid Sequence

• ·Selank. Anxiolytic models, with published work reporting effects on GABAergic and serotonergic measures[3] and on cytokine expression,[2] plus a small clinical literature in Russian anxiety settings.[1]
• ·Semax. Cognitive and neuroprotective models, with the mechanistic centre of gravity on BDNF and trkB expression in the hippocampus.[4] The neuroprotective work in stroke models is the part most often cited.
• ·Both are registered as pharmaceutical nasal preparations in Russia and nowhere else, which is a real distinction from most of this catalogue but not an approval that carries into Canada.
• ·Neither has an approval in Canada, and neither is supplied here for any use other than laboratory research.

Both literatures are genuine, decades deep, and heavily concentrated in a single national research tradition. Independent replication outside those institutions is thin, and a large share of the primary work is published in journals with limited reach in the English-language literature.

That is not an accusation, and it is not a reason to dismiss the compounds. It is a reason to hold the outcome claims at the standard the evidence supports: interesting, internally consistent, and not independently confirmed at the scale a Western regulatory dossier would require. A methods section that says so is stronger than one that quietly treats the Russian clinical literature as equivalent to a phase 3 programme.

Both compounds are also sold in N-acetylated form, and those are not grades or formulations of the parent. Acetylation of the N-terminus is a covalent modification that changes stability, changes kinetics, and changes molecular weight.

The practical consequence is that a supplier must state which one is in the vial and the certificate must confirm it, because the mass difference is exactly what mass-spectrometric identity is for. A listing that treats "semax" and "N-acetyl semax" as interchangeable is describing two different compounds with one word. The notation is explained in understanding peptide sequences.

Short sequences are cheap to substitute, which makes identity testing the load-bearing check for this pair rather than a formality. The standard is the usual three: mass-spectrometric identity against the theoretical mass, HPLC purity, and measured content against the labelled amount, published per lot before sale and verifiable on the testing laboratory's own database.

Published Certificate

Batch

SLNK-CA-26F-10

Purity (HPLC)

99.161%

Measured content

10.55 mglabelled 10 mg

Laboratory

Janoshik

Verify on the lab’s own databaseAll published certificates

Published Certificate

Batch

SMAX-CA-26G-10

Purity (HPLC)

99.0.53%

Measured content

10.69 mglabelled 10 mg

Laboratory

Janoshik

Verify on the lab’s own databaseAll published certificates

The honest selection rule is short. Selank for anxiolytic-model questions and for anything where the immune-marker side of the literature is relevant. Semax for cognitive and neurotrophic questions. Both when a panel spans the two domains, which is common, since the two compounds are studied together often enough that the pairing has its own small literature.

All four molecules, both parents and both N-acetyl variants, are listed separately with their own lot certificates.

Available at Eppix Labs

Buy Selank Canada | Anxiolytic Peptide 10mg

10mg

Every batch tested by an independent laboratory, with the certificate published before sale.

From $35.00 CADIn stock

Available at Eppix Labs

Buy Semax Canada | Nootropic Peptide 10mg

10mg

Every batch tested by an independent laboratory, with the certificate published before sale.

From $40.00 CADIn stock