Selank and Semax: Russian-developed neuropeptides in BDNF and GABA research

Two neuropeptides from the same research family

Selank and Semax are synthetic neuropeptides developed in Russia. Both are short analogues of natural protein fragments and are built from seven amino acid residues. That small size makes them straightforward to synthesise, analyse and check for purity batch by batch. Despite their similar dimensions, they differ in starting point, sequence and in the biological systems most often described in the literature. This guide sets those differences out clearly for researchers planning work with these reagents.

Selank: a tuftsin analogue

Selank has the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. The first four residues match tuftsin, a natural tetrapeptide (Thr-Lys-Pro-Arg) released from a fragment of the immunoglobulin G heavy chain. Tuftsin is described in the literature as a factor linked to phagocytic activity. Selank adds a Pro-Gly-Pro tail to this sequence. According to published descriptions, that extension lengthens the molecule and improves its resistance to enzymatic breakdown. The molecular weight is roughly 750 Da.

Semax: an ACTH(4-10) analogue

Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It starts from the ACTH(4-10) fragment, residues 4 to 10 of corticotropin. In Semax, the final Arg-Trp-Gly residues are replaced by Pro-Gly-Pro. The modification is described as a way to keep the neuroregulatory activity of the fragment while reducing its hormonal effects. The molecular weight is roughly 810 Da.

Side-by-side comparison

Feature	Selank	Semax
Sequence	Thr-Lys-Pro-Arg-Pro-Gly-Pro	Met-Glu-His-Phe-Pro-Gly-Pro
Starting point	tuftsin (Thr-Lys-Pro-Arg)	ACTH(4-10), a corticotropin fragment
Length	7 amino acid residues	7 amino acid residues
Molecular weight	roughly 750 Da	roughly 810 Da
Contains sulphur	no	yes (methionine residue)
Main research themes	GABA system, immune modulation, cognitive models in rodents	BDNF, NGF, learning models in rodents

GABA and immune signalling

GABA is the main inhibitory neurotransmitter in the central nervous system, and the interactions of Selank with this system are among the most discussed themes in its literature. In in vitro work and animal models, Selank has also been described as affecting enkephalins, the body’s own opioid-like peptides, and the enzymes that break them down. Because the peptide derives from tuftsin, it is also discussed in the context of immune modulation.

BDNF and NGF in model systems

BDNF, brain-derived neurotrophic factor, is a protein widely described as a key regulator of neuron survival and differentiation. NGF, nerve growth factor, plays a related role. In animal studies, Semax has been reported to influence BDNF and NGF expression in selected brain regions. Work linking Selank to BDNF is less extensive and calls for careful interpretation. Most of the data comes from rodent experiments and in vitro studies, rather than from large clinical programmes.

Lab practice: stability and handling

Short peptides are sensitive to moisture, light and repeated temperature swings. For reliable lab work, keep these points in mind:

• store lyophilised material cold, in a sealed container, as the product sheet specifies,
• reconstitute only when needed and maintain aseptic technique,
• check HPLC purity and MS mass confirmation for each batch,
• plan working solutions with our concentration calculator before you start.

Every batch at MOLEVIA is at least 99% pure by HPLC, with mass confirmed by MS. You can find more about how we check material on our quality page.

Selank or Semax? Matching the peptide to the question

The right choice depends on the question your team is asking. If the study concerns the GABA system, interactions with enkephalins or immune responses, Selank is the natural starting point. If you are interested in trophic factor expression, such as BDNF and NGF, Semax is the better place to begin. Both peptides can also sit inside one project as two separate comparison arms, which lets you assess the differences between them without attributing results the literature does not support.

Order with same-day dispatch

Selank and Semax are available in our shop: Selank and Semax. Orders placed by 14:00 on a working day ship the same day. In Poland, parcels go to an InPost Parcel Locker with next working day delivery. Across Europe, a DPD courier delivers in 2-4 working days. Shipping is free on orders from 75 EUR, 65 GBP, 80 USD. Pay online by card, Apple Pay, Google Pay or BLIK (PLN only). We settle in PLN, EUR, GBP and USD. Full details are on our shipping page.

Why the two are studied together

Selank and Semax are often discussed side by side because they come from the same research tradition and share a similar length. For a team working on neuroplasticity, that means two molecules with different starting points that can be compared under the same experimental conditions. The differences in sequence are small and easy to map in structural analysis, which makes it simpler to link an observation to a specific part of the molecule. Every project should still have its own control groups and clearly defined endpoints, because structural analogy alone does not settle outcomes.

Key points

• Selank is a tuftsin analogue with the sequence TKPR and a Pro-Gly-Pro tail, about 750 Da.
• Semax is an ACTH(4-10) analogue in which Arg-Trp-Gly is replaced by Pro-Gly-Pro, about 810 Da.
• In research, Selank is linked mainly to the GABA system and immune signalling, while Semax is linked to BDNF and NGF.
• Both are short peptides, so storage and handling determine how well they hold up.
• Every batch comes with HPLC purity of at least 99% and MS mass confirmation.
• Both products are research reagents for laboratory use.