PE-22-28 (8mg) · Research brief

PE-22-28 vs Selank and Dihexa: Peptide Comparison

Real Peptides Research TeamEditorial

Updated September 22, 20269 min read

56 WORDS

Short answer

Put PE-22-28, Selank, and Dihexa on the same bench and the striking thing is how little they share. One blocks a potassium channel. One works upstream of GABAergic tone and endogenous enkephalins. One potentiates a growth factor receptor with no relationship to either. Filing all three under the label 'nootropic peptides' hides more than it explains.

Key takeaways

PE-22-28 antagonises the TREK-1 potassium channel, Selank acts through GABAergic and enkephalin pathways, and Dihexa potentiates HGF signalling at the c-Met receptor, making them three unrelated pharmacological classes.
The pe-22-28 vs selank decision is settled by behavioural model, not potency: one has an antidepressant-like literature, the other an anxiolytic-like one.
Spadin's plasma stability is reported in minutes, which is precisely why PE-22-28 was engineered as a shorter, more degradation-resistant analog.
Selank is registered as a medicine in Russia but holds no FDA approval, and none of these compounds are approved drugs for human or veterinary use.
Cross-study potency comparisons are invalid because published rodent work used different routes: intraperitoneal and intranasal for spadin analogs, intranasal for Selank, oral for Dihexa.
Batch-level RP-HPLC purity and mass spectrometry identity data on a certificate of analysis matter more to reproducibility than any brand claim.

We supply research-grade compounds to labs running behavioural and neurochemical assays, and pe-22-28 vs selank is one of the most frequent sourcing questions we field. The researchers asking it already know their endpoint. What they want is the molecule the published literature actually supports for that endpoint.

PE-22-28 vs Selank: what actually separates them?

PE-22-28 is a shortened spadin analog that antagonises the TREK-1 potassium channel, a target linked in rodent work to rapid antidepressant-like behavioural change. Selank is a tuftsin-derived heptapeptide studied mainly for anxiolytic-like activity through GABAergic and enkephalin-related pathways. Different protein family, different behavioural models, different stability in solution. Choose by endpoint, not by category label.

The oversimplification worth killing early: these are not three grades of the same thing. No dose ladder connects them, and a result obtained with one predicts very little about the others, because they act on unrelated protein families. This comparison covers the molecular target behind each compound, what the animal literature does and does not report, and how the three differ in laboratory handling, stability, and documentation.

Three compounds, three unrelated molecular targets

PE-22-28 is a short analog of spadin, a peptide derived from the propeptide of sortilin (also called neurotensin receptor-3). Spadin was characterised by Mazella and colleagues in PLoS Biology in 2010 as a blocker of TREK-1 (gene KCNK2, channel K2P2.1), a two-pore-domain potassium channel. TREK-1 knockout mice show a depression-resistant phenotype in standard rodent screens, which is what put the channel on the map. Spadin's plasma stability is poor, reported in minutes, so PE-22-28 was designed as a shorter fragment retaining TREK-1 antagonism with better resistance to degradation.

Selank is the heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro: the immunopeptide tuftsin with a Pro-Gly-Pro tail added to slow enzymatic breakdown. It was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. Published work reports altered GABA-A receptor subunit expression, inhibition of enkephalin-degrading enzymes (which extends the life of endogenous enkephalins), changes in hippocampal BDNF expression, and cytokine effects inherited from its tuftsin origin.

Dihexa (N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide, also labelled PNB-0408) came out of angiotensin IV research at Washington State University. Literature describes it as a hepatocyte growth factor mimetic or potentiator acting through the c-Met receptor, with synaptogenesis as the reported downstream readout. Structurally it is a small peptidomimetic rather than a conventional peptide. Labs that pick the target first and the compound second consistently get cleaner data.

What the animal literature reports, and where it stops

Every citable behavioural result for these three compounds comes from rodents, and that single fact should frame the whole comparison. For PE-22-28, the interest is onset speed: TREK-1 blockade produced antidepressant-like changes in rodent screens within a few days in published work, against the several weeks generally needed for SSRIs such as fluoxetine, alongside reported increases in hippocampal neurogenesis markers. Selank has the longest applied history of the three. It is registered as a medicine in Russia and has been studied in anxiety-related and cognitive paradigms, though it carries no FDA approval. Dihexa research centres on spatial learning recovery in scopolamine-impaired and lesioned rodents, with the original Washington State University reports describing oral activity and blood-brain-barrier penetration.

Here is the detail most side-by-side write-ups skip. Route and vehicle differ across these literatures. Much of the spadin and PE-22-28 rodent data uses intraperitoneal or intranasal delivery, Selank studies frequently use intranasal administration, and Dihexa was profiled orally in rodents. Comparing potency figures across those papers is not really a comparison of pharmacology, it is a comparison of pharmacokinetics. That is why the pe-22-28 vs selank question can only be settled by choosing a behavioural model first. The pe-22-28 vs dihexa question collapses even faster, since one is measured on mood-related behaviour and the other on learning and dendritic spine density.

One caution the literature discusses openly: c-Met signalling is implicated in tumour proliferation, so potentiating that pathway carries a theoretical oncogenic concern relevant to study design.

Handling, stability, and what to verify before ordering

Lyophilised peptides are typically stored at -20°C, protected from light, and kept dry until reconstitution; once in solution, refrigeration at 2-8°C and a short working window are standard laboratory practice. Repeated freeze-thaw cycling degrades peptide integrity faster than most researchers expect, and at low working concentrations both Selank and PE-22-28 can adsorb onto glass and plastic surfaces, quietly reducing effective concentration before anything reaches an assay. None of that is visible in the vial. It only shows up as noise in your data.

Format matters too. Selank is supplied both as a liquid preparation and as a lyophilised amidate, and the amidated variant differs at the C-terminus, which affects enzymatic stability. Dihexa is handled as a powder with different solubility behaviour from either peptide. For anyone weighing pe-22-28 vs selank purely on quality grounds, the deciding document is the batch certificate: RP-HPLC purity, mass spectrometry identity confirmation, and a lot number that matches the vial in your hand.

That is why our Selank Liquid Spray, Selank Amidate, and Dihexa listings each sit alongside the wider Selank research overview, published certificates of analysis, and the full research catalog. Everything described here is supplied for laboratory research use only, is not approved for human or veterinary use, and any question about a person's or an animal's health belongs with a licensed physician or veterinarian, not a peptide supplier.

PE-22-28 vs Selank and Dihexa: Head-to-Head Comparison

Researchers type this as pe 22 28 vs selank, as pe 22 28 peptide vs selank, and as pe-22-28 vs dihexa, but the underlying question is always the same: which target does my endpoint actually require? The table below maps target, structure, and research focus so the choice is made on mechanism rather than marketing.

Compound	Molecular target	Structure and class	Dominant research focus	Handling and stability notes	Bottom line for researchers
PE-22-28	TREK-1 potassium channel (KCNK2 / K2P2.1), blocked via the sortilin-derived spadin mechanism	Short spadin fragment analog, a true peptide sequence	Rodent antidepressant-like screens with rapid onset and reported hippocampal neurogenesis markers	Lyophilised storage at -20°C; parent spadin has very short plasma stability, which is the reason the analog exists	The narrowest and most novel target of the three; relevant only if the study question is TREK-1 channel modulation
Selank	GABA-A receptor subunit expression and enkephalin-degrading enzyme inhibition, with cytokine effects from its tuftsin parent	Heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro, tuftsin plus a stabilising Pro-Gly-Pro tail	Anxiolytic-like and cognitive rodent paradigms; longest applied research history of the three	Available as liquid preparation and as lyophilised amidate; the amidated form differs at the C-terminus and resists degradation differently	The best-documented option for anxiety-related endpoints, with the deepest published body of work behind it
Dihexa	c-Met receptor, via potentiation of hepatocyte growth factor signalling	N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide peptidomimetic, not a conventional peptide	Spatial learning recovery in impaired rodents and synaptogenesis or spine density readouts	Powder with solubility behaviour unlike either peptide; c-Met involvement in tumour biology is a documented design consideration	The right tool only for synaptic and learning endpoints, and the one demanding the most careful safety framing

What If: Research Design Scenarios

What if the endpoint is anxiety-like behaviour rather than depression-like behaviour?

Selank is the compound with the deeper literature base for that endpoint. Its published mechanism, involving GABA-A receptor subunit expression and inhibition of enkephalin-degrading enzymes, maps directly onto anxiety-related paradigms, while PE-22-28 work has clustered around antidepressant-like screens tied to TREK-1 blockade. Picking the wrong compound for the wrong model produces a null result that tells you nothing about either molecule.

Dihexa is the compound studied against spinogenesis and spatial learning endpoints. Neither Selank nor PE-22-28 has a comparable synaptogenesis literature, which is the honest answer to pe-22-28 vs dihexa: they are not competitors, they answer different questions. Factor in the c-Met and tumour biology consideration at the protocol design stage rather than after data collection.

What if a new vial looks different from the previous batch?

Stop and check the certificate of analysis for that lot number before reconstituting anything. Lyophilised peptide cake appearance varies with fill volume, lyophilisation cycle, and residual moisture, so visual difference alone is not evidence of a problem, but it is a legitimate trigger for documentation review. Purity and identity data belong to a specific batch, never to a product name in general.

What if a reconstituted vial was left at room temperature overnight?

Log the excursion and treat that vial as unsuitable for quantitative work. Peptides in solution degrade faster outside 2-8°C, and there is no home or bench test that reliably confirms retained potency after a temperature excursion. Running the assay anyway means any anomalous result is uninterpretable, because you cannot separate compound effect from degradation.

The Uncomfortable Truth About Ranking These Three

Here is the honest answer: there is no winner in pe-22-28 vs selank, and anyone ranking them on a single scale is selling something. They hit different protein families, were validated in different behavioural models, and were delivered by different routes in the studies people cite. Most published data on all three is preclinical and rodent-based. The rigorous version of the pe-22-28 vs selank comparison is not which is stronger, it is which target your hypothesis names. Everything else is a category error dressed up as a recommendation.

The pe-22-28 vs selank question keeps resurfacing because both compounds arrived with genuinely interesting mechanisms and almost no translational data to argue over, which leaves comparison charts to fill the gap. TREK-1 antagonism is a real and unusual target. Tuftsin-derived GABAergic modulation is a real and unusual target. They are simply not the same target, and no amount of side-by-side formatting will make them one. The researchers who get value from these molecules treat them as three separate tools with three separate literatures, and they read the batch certificate before they read the comparison table.

References

Peer-reviewed sources on Selank indexed in PubMed, listed for research context. Real Peptides supplies Selank for laboratory research use only.

Selank, a Peptide Analog of Tuftsin, Attenuates Aversive Signs of Morphine Withdrawal in Rats. Bulletin of experimental biology and medicine, 2022. PMID 36322304. doi:10.1007/s10517-022-05624-x
The Influence of Selank on the Level of Cytokines Under the Conditions of "Social" Stress. Current reviews in clinical and experimental pharmacology, 2021. PMID 32621722. doi:10.2174/1574884715666200704152810
Functional Connectomic Approach to Studying Selank and Semax Effects. Doklady biological sciences : proceedings of the Academy of Sciences of the USSR, Biological sciences sections, 2020. PMID 32342318. doi:10.1134/S001249662001007X
Morphological Changes in the Large Intestine of Rats Subjected to Chronic Restraint Stress and Treated with Selank. Bulletin of experimental biology and medicine, 2020. PMID 32651826. doi:10.1007/s10517-020-04868-9
Selank, Peptide Analogue of Tuftsin, Protects Against Ethanol-Induced Memory Impairment by Regulating of BDNF Content in the Hippocampus and Prefrontal Cortex in Rats. Bulletin of experimental biology and medicine, 2019. PMID 31625062. doi:10.1007/s10517-019-04588-9
Effect of Selank on Morphological Parameters of Rat Liver in Chronic Foot-Shock Stress. Bulletin of experimental biology and medicine, 2019. PMID 31243679. doi:10.1007/s10517-019-04512-1
Peptide-based Anxiolytics: The Molecular Aspects of Heptapeptide Selank Biological Activity. Protein and peptide letters, 2018. PMID 30255741. doi:10.2174/0929866525666180925144642
Effect of Selank on Functional State of Rat Hepatocytes under Conditions of Restraint Stress. Bulletin of experimental biology and medicine, 2017. PMID 28853100. doi:10.1007/s10517-017-3817-8

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Questions

PE-22-28 is a spadin-derived analog that blocks the TREK-1 two-pore-domain potassium channel (KCNK2), a target identified through sortilin propeptide research. Selank is a tuftsin-derived heptapeptide whose published mechanism involves GABA-A receptor subunit expression, inhibition of enkephalin-degrading enzymes, and changes in hippocampal BDNF expression. They act on entirely different protein families, so results with one do not predict results with the other.

PE-22-28 is a shortened analog of spadin, the peptide released from the propeptide of sortilin (neurotensin receptor-3). Spadin was described as a TREK-1 blocker in PLoS Biology in 2010, but its plasma stability is poor, reported in minutes. PE-22-28 was developed to retain TREK-1 antagonism in a shorter sequence with improved resistance to enzymatic degradation.

Selank has the deeper and longer research record. It was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, is registered as a medicine in Russia, and has appeared in anxiety-related and cognitive rodent paradigms for decades. PE-22-28 and its parent spadin represent a newer line of TREK-1 research with a much smaller published literature.

They are not comparable tools. PE-22-28 blocks the TREK-1 potassium channel and appears in mood-related rodent behavioural screens. Dihexa is an angiotensin IV derived peptidomimetic that potentiates hepatocyte growth factor signalling through the c-Met receptor, and its literature focuses on synaptogenesis and spatial learning recovery in impaired rodents. Different target, different endpoint, different assay design.

No. None of these compounds is an FDA-approved drug, and none is approved for human or veterinary use. Selank holds regulatory registration as a medicine in Russia but not in the United States. All three are supplied strictly as research chemicals for laboratory investigation, and health questions should go to a licensed physician or veterinarian.

Standard laboratory practice is storing lyophilised peptide at -20°C, protected from light and moisture, until reconstitution. Once in solution, refrigeration at 2-8°C with a short working window is typical, and repeated freeze-thaw cycling should be avoided because it accelerates degradation. At low working concentrations, peptides can also adsorb onto glass and plastic, which quietly lowers effective concentration.

A useful certificate of analysis lists the specific lot number, RP-HPLC purity percentage, and mass spectrometry confirmation that the measured molecular weight matches the intended sequence. Purity data belongs to a batch, not to a product name, so the lot on the certificate should match the lot printed on the vial. Real Peptides publishes batch certificates for catalog compounds.

Because the published studies used different delivery routes and vehicles. Spadin and PE-22-28 rodent work commonly used intraperitoneal or intranasal delivery, Selank research frequently used intranasal administration, and Dihexa was profiled with oral dosing in rodents. Comparing numbers across those papers compares pharmacokinetics as much as pharmacology, which makes any resulting ranking meaningless.

Selank amidate carries an amidated C-terminus rather than a free carboxyl terminus. That modification changes how readily terminal exopeptidases degrade the molecule, which affects stability in solution and in biological matrices. The core Thr-Lys-Pro-Arg-Pro-Gly-Pro sequence is the same, so the practical difference researchers report is handling and degradation behaviour rather than a different target.

Yes, and the literature discusses it openly. Dihexa acts by potentiating hepatocyte growth factor signalling at the c-Met receptor, and c-Met activity is implicated in tumour proliferation, which creates a theoretical oncogenic concern relevant to preclinical study design. Neither PE-22-28 nor Selank engages that pathway, so this consideration is specific to Dihexa protocols.

Selank has the most directly relevant published record for anxiety-related paradigms, based on its reported effects on GABA-A receptor subunit expression and endogenous enkephalin availability. PE-22-28 research has clustered around antidepressant-like screens tied to TREK-1 blockade instead. Matching compound to behavioural model before the study begins prevents null results that reflect design error rather than compound activity.

RESEARCH USE ONLY · NOT EVALUATED BY THE FDA