Table of Contents
Structural Origins and Sequences
Semax is a heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It is a synthetic analogue of the ACTH(4-7) fragment — a portion of adrenocorticotropic hormone — with a C-terminal Pro-Gly-Pro extension added to improve stability and modify pharmacological activity relative to the parent fragment. The molecular weight of Semax is approximately 887.0 Da.
Selank is a heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It is derived from a modified form of the endogenous neuropeptide tuftsin (Thr-Lys-Pro-Arg), with the same C-terminal Pro-Gly-Pro extension used in Semax. Despite sharing this extension and the same residue count, the core sequences are entirely different — Semax derives from ACTH and Selank derives from tuftsin.
Both peptides were developed at the Institute of Molecular Genetics (now part of the Russian Academy of Sciences) and have been subjects of Russian government-sponsored research since the 1990s. Understanding the distinct peptide sequences is important for researchers — these are not structural variants of the same compound but genuinely different molecules with different primary pharmacological targets.
Semax: Research Profile
Semax's pharmacological profile in published research is anchored to its origin as an ACTH analogue. Documented research areas include its interactions with melanocortin receptors (particularly MC4R), its effects on BDNF (brain-derived neurotrophic factor) expression in preclinical neural tissue models, and its influence on the serotonergic and dopaminergic systems in rodent preparations.
Published studies have documented Semax's effects in models of cognitive function, neuroprotection, and neuroplasticity. The compound has also been investigated in models examining retinal tissue and optic nerve preparations. The Russian literature on Semax is particularly extensive, with translation of key studies available in international databases.
Semax is notable for its BDNF-upregulating effects observed in published in vivo and in vitro studies. Researchers studying neurotrophin signalling pathways may find Semax a relevant tool for modulating BDNF expression in controlled neural tissue preparations, in line with published methodology.
Selank: Research Profile
Selank's pharmacological profile centers on its tuftsin-derived origin. Tuftsin itself is an endogenous tetrapeptide produced through cleavage of IgG, with documented immunomodulatory effects. Selank was designed to extend tuftsin's pharmacological activity profile, and the added Pro-Gly-Pro sequence contributes to its metabolic stability relative to the parent compound.
Published research on Selank has investigated its interactions with the GABAergic system, specifically its effects on GABA-A receptor subunit expression and on benzodiazepine receptor sites in rodent models. This interaction profile distinguishes Selank from Semax at the receptor level and gives the two compounds different research applications when studying inhibitory neurotransmission versus neurotrophic factor signalling.
Additional documented research areas for Selank include its immunomodulatory effects in murine models, its interaction with enkephalin-degrading enzyme systems, and anxiety-related behavioural endpoints in preclinical research. The compound has been investigated both as a standalone research tool and in comparison studies alongside other anxiolytic-profile compounds.
Key Pharmacological Differences
For researchers evaluating which compound to select for a specific study design, the following distinctions are the most practically relevant:
- Primary receptor targets: Semax engages melanocortin receptor pathways (ACTH-derived). Selank engages GABAergic and tuftsin receptor pathways. These are distinct systems — compound selection should follow the pathway under investigation.
- Neurotrophic vs. anxiolytic profile: The published literature positions Semax more strongly in neurotrophic factor (particularly BDNF) research, while Selank is more strongly represented in GABAergic and anxiety-related research paradigms. Neither description is absolute, but it reflects the general distribution of published work.
- Immunomodulatory literature: Selank's tuftsin origin gives it a more prominent immunomodulatory literature base than Semax, relevant to researchers working at the neuroimmune interface.
- Stability: Both compounds share the C-terminal Pro-Gly-Pro extension, which contributes to resistance against enzymatic degradation by prolyl endopeptidase. Stability profiles in solution are broadly comparable, though researchers should confirm handling conditions with reference to published methodology.
Selecting Between Them for Study Design
Compound selection between Semax and Selank should be driven by the specific molecular pathway or receptor system under investigation. A research protocol examining BDNF modulation in neural tissue preparations has better literature support for Semax. A protocol examining GABAergic system modulation or benzodiazepine receptor interactions has stronger published precedent for Selank.
Comparative study designs using both compounds simultaneously are represented in the published literature and can be valid research approaches when the study question explicitly involves comparison of the two compounds' effects on a shared downstream readout. Researchers conducting comparative studies should carefully control for vehicle effects and use appropriate concentration ranges informed by published methodology for each compound independently.
Both Semax and Selank are available in the nootropics research category. View Semax 10mg and Selank 10mg for current specifications and pricing.
Sourcing Both Compounds in Canada
Peptides Canada supplies both Semax 10mg and Selank 10mg for research use, with HPLC-verified purity and third-party documentation. Both ship from within Canada. For researchers sourcing both compounds for a comparative study design, the contact page is available for combined order enquiries and documentation requests.
The FAQ addresses common questions about storage, reconstitution, and order logistics. For a broader overview of supplier evaluation criteria applicable to both compounds, the guide to sourcing peptides in Canada covers the key evaluation dimensions in detail.