Semax & Selank: Nootropic Peptides for Cognitive Research | PeptidesDirect
Complete guide to Semax and Selank nootropic peptides. Compare mechanisms, research applications, and find research-grade quality with EU shipping.
Semax and Selank: What Researchers Should Know
Semax and Selank come up together so often in cognitive neuroscience that you'd be forgiven for thinking they're interchangeable. They're not. Both were developed at the Institute of Molecular Genetics in Moscow, both are synthetic heptapeptides stabilized with a Pro-Gly-Pro extension, and both show nootropic properties in research models. But they derive from entirely different parent molecules and work through separate mechanisms. Understanding those differences matters when designing experiments.
Semax: Built from ACTH
Semax is based on the ACTH(4-7) fragment of adrenocorticotropic hormone. The original research goal in the 1980s was straightforward: keep the neurotropic effects of ACTH, strip out the hormonal activity. The resulting sequence -- Met-Glu-His-Phe-Pro-Gly-Pro -- achieved exactly that. The C-terminal Pro-Gly-Pro extension gives it far better stability and a longer biological half-life than the native ACTH fragment.
How Semax Works
BDNF Upregulation — The Core Mechanism
The most consistently documented effect of Semax is upregulation of Brain-Derived Neurotrophic Factor (BDNF). This is significant because BDNF drives neuronal survival, synaptic plasticity, long-term memory consolidation, and hippocampal neurogenesis. Semax also influences Nerve Growth Factor (NGF) expression and modulates dopamine and serotonin metabolism in the brain.
Transcriptomic studies have added another layer of complexity. Semax affects expression of hundreds of genes tied to immune response, vascular function, and neuronal signaling. This breadth of action makes it interesting but also makes it harder to pin down a single "primary" mechanism.
In research models, Semax has shown neuroprotective effects in stroke and ischemia paradigms, improved memory and learning in behavioral assays, anti-inflammatory activity in neural tissue, and enhanced attention in animal behavioral tests.
ACTH(4-7)-derived heptapeptide. Primary mechanism: BDNF and NGF upregulation for neuroprotection and plasticity.
Selank: Built from Tuftsin
Selank takes a different parent molecule entirely. It's an analog of tuftsin (Thr-Lys-Pro-Arg), an endogenous immunomodulatory peptide. The full sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, again stabilized with that same Gly-Pro extension. Tuftsin is primarily an immunostimulant, but Selank was developed to exploit its anxiolytic and nootropic properties.
How Selank Works
GABAergic Modulation Without Sedation
Where Semax acts mainly through neurotrophic pathways, Selank targets the GABAergic system -- the brain's primary inhibitory machinery. This is the same system benzodiazepines act on, but Selank appears to modulate GABA without producing sedation or dependence in research models. That distinction alone makes it attractive for anxiety research.
Selank also inhibits enzymes that degrade enkephalins, the endogenous opioid peptides involved in mood regulation. By prolonging enkephalin activity, Selank promotes calming effects without the risks of exogenous opioids. Add to that its effects on serotonin, dopamine, and norepinephrine balance, and you get a peptide with broad mood-stabilizing potential.
Because of its tuftsin heritage, Selank retains genuine immunomodulatory properties. It influences cytokine production and immune cell function, which makes it relevant to neuroimmune research as well.
The main research applications include anxiety and stress-response models, cytokine regulation and immune function studies, cognitive performance under stress, and transcriptomic analysis of inflammatory and neurotransmitter gene networks.
Tuftsin-derived anxiolytic peptide. GABAergic modulation and enkephalin stabilization without sedation.
Comparing the Two
The differences become clearer when you look at them side by side.
Parent molecule. Semax derives from ACTH(4-7). Selank derives from tuftsin. These are fundamentally different starting points.
Primary research focus. Semax is the stronger candidate for cognitive enhancement and neuroprotection work. Selank is more suited to anxiolytic and mood stabilization research.
Key pathways. Semax acts through BDNF and NGF upregulation, driving neurotrophic signaling. Selank works through GABAergic modulation and enkephalin metabolism.
Neurotransmitter effects. Semax increases dopamine and serotonin activity. Selank enhances GABA signaling and rebalances monoamines.
Immune involvement. Semax affects immune-related gene expression indirectly. Selank has direct immunomodulatory effects inherited from tuftsin.
Sedation. Neither peptide produces sedation in research models.
Choosing Between Them
Using Both Together
Their mechanisms are genuinely complementary. Semax brings the activating, neurotrophic component -- BDNF upregulation, dopaminergic enhancement. Selank provides the calming side -- GABAergic modulation, enkephalin stabilization. Combined, they model a balanced nootropic intervention: enhanced cognition without increased anxiety. Many research groups study them in parallel for exactly this reason.
Combined nootropic stack pairing BDNF-driven plasticity with GABAergic anxiolysis for balanced cognitive research.
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Handling and Storage
Reconstitution and Storage Protocol
Both Semax and Selank ship as lyophilized powder. Reconstitute with bacteriostatic water by adding it slowly along the vial wall, then swirl gently until dissolved. Do not shake.
Store unreconstituted peptide at -20 degrees C, protected from light and moisture. Once reconstituted, keep at 2-8 degrees C and use within four weeks. Avoid repeated freeze-thaw cycles. For more detail, see our Peptide Storage Guide.
Quality Testing
Every cognitive peptide from PeptidesDirect ships with a Janoshik Certificate of Analysis confirming purity at 98% or above, verified by independent mass spectrometry for molecular identity and HPLC for quantitative purity. EU shipping runs 2-3 business days.
Where the Field Is Heading
Nootropic peptide research is moving in several directions at once. Combination studies pairing Semax and Selank with other neuropeptides are becoming more common. Nasal delivery formulations are being refined to improve CNS access. Structural analogs like Adamax continue to expand the toolkit. And transcriptomic approaches are finally giving researchers a genome-wide view of what these peptides actually do at the molecular level, which will be essential for any eventual translational work.
Wrapping Up
Semax and Selank are not the same peptide with different names. Semax is the neurotrophic, neuroprotective tool. Selank is the anxiolytic, immunomodulatory one. Knowing which mechanism matters for your research question is the whole point of understanding both.