A practical reference on Enkephalinase: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-06-22. Anything still debated is marked as such rather than presented as settled.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
| Property | Value | Notes |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
== Awards and honours == 2004 National Science Foundation CAREER Award 2010 American Chemical Society Horace S. Isbell Award 2017 Elected Edward, Frances, and Shirley B. Daniels Fellow at Harvard University 2017 International Fluorous Technology Award 2017 Silicon Valley Chemist Harry and Carol Mosher Award 2018 American Chemical Society Melville L. Wolfram Award 2019 Fulbright Program Scholar 2020 Elected a Fellow of the American Association for the Advancement of Science
=== Solid interfaces === Nano-particles can self-assemble on solid surfaces after external forces (like magnetic and electric) are applied. Templates made of microstructures, like carbon nanotubes or block polymers, can also be used to assist in self-assembly. They cause directed self-assembly (DSA), in which active sites are embedded to selectively induce nanoparticle deposition. Such templates are objects onto which different particles can be arranged into a structure with a morphology similar to that of the template. Carbon nanotubes (microstructures), single molecules, or block copolymers are common templates. Nanoparticles are often shown to self-assemble within distances of nanometers and micrometers, but block copolymer templates can be used to form well-defined self-assemblies over macroscopic distances. By incorporating active sites to the surfaces of nanotubes and polymers, the functionalization of these templates can be transformed to favor self-assembly of specified nanoparticles.
== Products and services == The major products of the company are Surfaxin (based on its capillary aerosol-generating technology) and Aerosurf. Surfaxin is a synthetic, peptide-containing (KL4) surfactant, similar to pulmonary surfactant, which is naturally in the lung for normal respiratory function. The drug is delivered by its capillary aerosol-generating technology to the lung. Aerosurf is a drug-device combination to prevent respiratory distress syndrome (RDS) in premature infants. In addition, the company also provides Afectair devices (disposable aerosol-conducting airway connectors).
intrinsically disordered protein (IDP) A protein (or a region or domain within a protein) that lacks any distinct, fixed three-dimensional structure or organization under physiological conditions, instead changing continuously and randomly between multiple transient conformational states rather than folding into any one stable conformation, especially in the absence of specific macromolecular interaction partners. The majority of eukaryotic proteins contain domains with intrinsic structure alongside unstructured domains. Peptide sequences lacking intrinsic order are generally characterized by high proportions of charged and hydrophilic amino acids and low proportions of hydrophobic amino acids, making them inherently flexible, accessible, and modifiable, which allows the same peptide sequence to have distinct functions across a wide variety of biochemical circumstances. They are frequently enriched in binding motifs and are common targets of post-translational modifications, giving them important roles in cell signaling pathways and as hubs in protein complexes.
Kissinger summoned Dobrynin to the White House to accuse the Soviet Union of responsibility for the Easter Offensive, saying the North Vietnamese were fighting with Soviet-made weapons, and asked the Soviets to pressure the North Vietnamese to end the offensive.
Sources: en.wikipedia.org
=== Canada === The following programs of study have currently been approved by the Denturist Association of Canada for the profession of denturism. On successful completion of the selected courses, individuals are then required to complete a Qualifying Examination administered by the College of Denturists, consisting of two components: a written examination and a structured clinical examination. Upon successful completion of the examination, individuals may then register with the College of Denturists of Ontario to practice legally as a denturist.
=== Controversies === In 2018 UA received funding from the Pioneer Fund, a non-profit institute which promotes scientific racism and eugenics. The funds were applied for by Aurelio Jose Figueredo, who directs the graduate program on human behavior and evolutionary psychology. Funds from the grant were used by Figueredo to attend the 2016 London Conference on Intelligence, where presentations on eugenics are given. Figueredo has also reviewed papers for Mankind Quarterly, a journal which has advocated for racial hierarchy. Figueredo has disavowed eugenics and racial inferiority.
=== Examples === Black-box (stimulus/response) loggers: A flight data recorder (FDR) is a piece of recording equipment used to collect specific aircraft performance data. The term may also be used, albeit less accurately, to describe the cockpit voice recorder (CVR), another type of data recording device found on board aircraft. An event data recorder (EDR) is a device installed by the manufacturer in some automobiles which collects and stores various data during the time-frame immediately before and after a crash. A voyage data recorder (VDR) is a data recording system designed to collect data from various sensors on board a ship. A train event recorder is a device that records data about the operation of train controls and performance in response to those controls and other train control systems. An accident data recorder (ADR) is a device for triggering accidents or incidents in most kind of land vehicles and recording the relevant data. In automobiles, all diagnostic trouble codes (DTCs) are logged in engine control units (ECUs) so that at the time of service of a vehicle, a service engineer will read all the DTCs using Tech-2 or similar tools connected to the on-board diagnostics port, and will come to know problems occurred in the vehicle. Sometimes a small OBD data logger is plugged into the same port to continuously record vehicle data. In embedded system and digital electronics design, specialized high-speed digital data logger help overcome the limitations of more traditional instruments such as the oscilloscope and the logic analyzer.
However, even these hydrocarbons became waterlogged and thick after two days of use. Gasoline does not absorb water from the atmosphere and is sometimes used if ethanol is not available. Ethanol is the most widely used coolant today, as American corn ethanol subsidies have made it less expensive than gasoline in many rural areas.
=== Diagnostic imaging === The insulinoma might be localized by noninvasive means, using ultrasound, CT scan, or MRI techniques. An indium-111 pentetreotide scan is more sensitive than ultrasound, CT, or MRI for detection of somatostatin receptor positive tumours, but not a good diagnostic tool for insulinomas. An endoscopic ultrasound has a sensitivity of 40-93% (depending on the location of the tumour) for detecting insulinomas. Sometimes, angiography with percutaneous transhepatic pancreatic vein catheterization to sample the blood for insulin levels is required. Calcium can be injected into selected arteries to stimulate insulin release from various parts of the pancreas, which can be measured by sampling blood from their respective veins. The use of calcium stimulation improves the specificity of this test.During surgery to remove an insulinoma, an intraoperative ultrasound can sometimes localize the tumour, which helps guide the surgeon in the operation and has a higher sensitivity than noninvasive imaging tests.
Sources: en.wikipedia.org
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.