ComparisonSeptember 10, 2026 · 1 min read

Semax vs Selank: Two Russian Heptapeptides, Two Research Lanes

Research compounds for laboratory use only · not medical advice

ACTH-fragment lineage versus tuftsin lineage — how Semax and Selank differ in sequence origin, signaling focus (BDNF vs cytokine/GABA), and where each is used as a CNS reference peptide.

Sold as a pair since the 2010s, studied as siblings since the 1980s — Semax and Selank come out of the same Russian peptide-stabilization program but answer to different parent molecules.

Side by side

	Semax	Selank
Sequence	Met-Glu-His-Phe-Pro-Gly-Pro	Thr-Lys-Pro-Arg-Pro-Gly-Pro
Parent fragment	ACTH 4-10 (hormone fragment)	Tuftsin (immune tetrapeptide) + extension
Approx. MW	≈ 814 g/mol	≈ 752 g/mol
Primary research lane	BDNF signaling, cognitive-plasticity models	Anxiolytic modulation, cytokine balance
Vial form (our catalog)	1 mg / 5 mg lyophilized	1 mg / 5 mg lyophilized

The full mechanics of each are in their guides: Semax and Selank.

Both natural fragments — an ACTH piece and an immune tetrapeptide — were enzymatically short-lived. The program’s move was surgical: keep the pharmacophore, edit the edges, re-test stability. That’s why both read as “heptapeptide + something”: Semax extends the 4-10 core; Selank appends Pro-Gly-Pro onto tuftsin. For vial math they behave like any lyophilized peptide — reconstitution calculator, molar conversions in the MW calculator.

Choosing between them in a panel

Cognitive-endpoint batteries reach for Semax; anxiety/stress-axis and immunomodulation batteries reach for Selank; panels that assay both lanes run both — they are not interchangeable, and the reason is written into their sequences. If the question is sleep-axis rather than either of these, the third Russian favorite in that slot is DSIP.

References: Kopylova L.A. et al., “Synthetic Peptide Analog of ACTH4-10 and Semax… (Review).” Russian Journal of Bioorganic Chemistry, 2019 · Site profiles: Semax guide, Selank guide.

For laboratory research use only. Not medical advice.

FAQ

Frequently asked questions

What is the core difference between Semax and Selank?

Origin and signaling lane. Semax is an ACTH 4-10 fragment analog studied mainly in BDNF/cognitive-plasticity models; Selank embeds the immune tetrapeptide tuftsin and is studied in anxiety-modulation and cytokine-balance models. Both are synthetic heptapeptides from the same Russian program.

Same dose, same results?

No — published research protocols treat them as separate instruments; the weight ranges overlap, the endpoints do not. Cognitive panels sometimes run both, which is why vendors sell them as a pair.

Which one is 'the nootropic'?

Semax — its literature consistently centers on learning/memory task models and BDNF-dependent plasticity. Selank's center of gravity is anxiolytic and immunomodulatory endpoints.

Are they the same family as ACTH or tuftsin?

Each is a stabilized analog of a different endogenous peptide: Semax of ACTH(4-10), Selank of tuftsin with a C-terminal extension. The stabilizing edits are what turned two short-lived natural fragments into research compounds with workable profiles.

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