Semax and Selank: The Russian Research Peptides

Semax and Selank come from the same Russian research tradition and are built on the same structural trick, but they are not variations of one compound. Semax comes from a stress hormone. Selank comes from an antibody fragment. They ended up in the same category because of how they were designed, not because of where they started.

The shared design trick

Both are heptapeptides, seven amino acids, and both end in the same three residues: proline, glycine, proline.

That tail is deliberate. Peptidases in blood and tissue chew peptides from the ends inward, and proline is awkward for many of them to cut past. Adding Pro-Gly-Pro caps the molecule against rapid degradation.

So both compounds have the same construction: a short biologically active fragment at the front, a protective tail at the back. Different fragment, same tail.

Semax

The active fragment in Semax is ACTH(4-7), a four residue piece of adrenocorticotropic hormone.

ACTH is the pituitary hormone that tells the adrenal glands to produce cortisol. That is its endocrine job. But ACTH also has effects in the brain on attention, learning and memory, and those effects were traced to a different region of the molecule than the one driving cortisol release.

Semax takes the fragment carrying the neural activity and leaves out the part that stimulates the adrenals. The result is a compound with the central effects and without the corticotropic ones. Cutting a hormone down to isolate one of its jobs is the same strategy behind AOD-9604, which does it with growth hormone.

What the research reports

• BDNF and NGF. The most cited finding is increased expression of brain derived neurotrophic factor and nerve growth factor in the hippocampus. These are the proteins that support neuron survival, growth and the formation of new connections.
• Neurotransmitter systems. Effects have been reported on dopaminergic and serotonergic signaling.
• Clinical use in Russia. Semax has been used there in stroke care and in cognitive and attention related conditions, and much of the literature reflects that setting.
• Route. It is commonly given intranasally, which takes advantage of the nasal route into the central nervous system.

Stocked in 5 mg and 10 mg vials.

Selank

Selank is built on tuftsin, a four amino acid sequence with the code TKPR.

Tuftsin is not a brain molecule at all in origin. It is cut out of the heavy chain of immunoglobulin G, the main class of antibody, and its known role is immune: it stimulates macrophages and other immune cells. Selank is tuftsin with the same Pro-Gly-Pro tail attached.

What makes it interesting is that a fragment from an antibody turned out to have activity in the central nervous system, and the research on Selank is dominated by anxiety rather than immunity.

What the research reports

• GABA system. Studies describe effects on GABAergic signaling, the main inhibitory system in the brain and the one benzodiazepines act on. Selank has been examined as an anxiolytic acting through this system without the sedation and dependence associated with that drug class.
• Enkephalins. Selank has been reported to inhibit the enzymes that break down enkephalins, the body’s own opioid peptides. Slowing their breakdown raises how long they persist.
• BDNF. As with Semax, changes in BDNF expression have been reported.
• Immune activity. Given its tuftsin origin, immunomodulatory effects appear in the literature too.

Available in 5 mg and 10 mg, and in a combined vial with Semax.

Why they get paired

The combination exists because the two are usually described as pulling in different directions along the same axis. Semax is associated with activation, attention and drive. Selank is associated with reducing anxiety. Neither duplicates the other, and the pairing is the reason a combined vial is offered.

Dihexa, a different approach

Also in this category is Dihexa, which works on another mechanism entirely. It is derived from angiotensin IV and acts on the hepatocyte growth factor and c-Met pathway, which is involved in forming new synaptic connections. Its research focus is synaptogenesis rather than neurotransmitter signaling.

Common questions

Does Semax raise cortisol?

The fragment it is built from, ACTH(4-7), does not carry the corticotropic activity of the full hormone. Separating the neural effects from the adrenal ones was the reason for using that fragment.

What is BDNF?

Brain derived neurotrophic factor, a protein that supports the survival and growth of neurons and the formation of new connections between them. It is one of the standard markers in this area of research.

Why does Selank come from an antibody?

Its parent sequence, tuftsin, is cut from the heavy chain of immunoglobulin G and has an immune role. The central nervous system activity was found separately, and it is what most of the Selank research follows.

Why the Pro-Gly-Pro tail?

Proline is difficult for many peptidases to cut past, so the tail protects the molecule from being broken down from the end. It is a stability feature, not an active part.

TL;DR

Both are seven amino acid peptides ending in a protective Pro-Gly-Pro tail. Semax is built on ACTH(4-7), the part of the stress hormone carrying neural activity but not the adrenal signal, and the research centers on BDNF and NGF in the hippocampus. Selank is built on tuftsin, a fragment of an antibody heavy chain, and its research centers on the GABA system and enkephalin breakdown.

Everything we supply is lab tested for purity and identity, and sold as research grade material for laboratory and research use. See the cognitive and nootropic range, or read about DSIP and sleep.