Enkephalinase is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-05-28. Numbers and descriptions here follow the published literature rather than marketing material.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Calculated for the free peptide |
| Molecular weight | About 751.9 g/mol | Derived from the sequence |
| Appearance | White to off-white powder | Typical lyophilised form |
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
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.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
=== Other methods === Of academic interest, palladium acetate, iodine, and oxygen can be used to couple cyclohexyl amine and cyclohexyl isocyanide. Yields of up to 67% have been achieved using this route:
=== Abuse and special populations === Benzodiazepine abuse and misuse are guarded against when prescribed to those with alcohol or other drug dependencies or who have psychiatric disorders. Pediatric patients For those less than 18 years of age, this treatment is usually not indicated, except for treatment of epilepsy, and pre-or postoperative treatment. The smallest possible effective dose is typically used for this group of patients. Under 6 months of age, safety and effectiveness have not been established; diazepam is not given to those in this age group. Elderly and seriously ill patients can experience apnea or cardiac arrest. Concomitant use of other central nervous system depressants increases this risk. The smallest possible effective dose is generally used for this group of people. The elderly metabolize benzodiazepines much more slowly than younger adults, and are also more sensitive to the effects of benzodiazepines, even at similar blood plasma levels. Doses of diazepam are recommended to be about half of those given to younger people, and treatment is limited to a maximum of two weeks. Long-acting benzodiazepines such as diazepam are not recommended for the elderly. Diazepam can also be dangerous in geriatric patients owing to a significantly increased risk of falls. Intravenous or intramuscular injections in hypotensive people or those in shock are administered carefully, and vital signs are closely monitored.
The San Francisco 49ers defeated the Cincinnati Bengals 26 to 21, to win Super Bowl XVI at the Pontiac Silverdome in Pontiac, Michigan. The telecast of the game continues to hold the record for highest television ratings for a Super Bowl broadcast, with a 49.1 rating and a 73 share of the audience, with almost three out of four households with television watching the game. U.S. astronomer Edward L. G. Bowell discovered three asteroids in the same day, designating the 9 miles (14 km) minor planet as 3131 Mason-Dixon. The name honored English astronomers and surveyors Charles Mason and Jeremiah Dixon for whom the "Mason–Dixon line" boundary between U.S. states was named. On the same day, Bowell discovered 3749 Balam, which has two minor-planet moons revolving around it, and 2905 Plaskett. Born: Jamie "Killer" Lyon, Australian professional rugby league centre, selected as the National Rugby League's Dally M Medal winner for centre of the year in 2010, 2011, 2013 and 2014, and Centre of the Year by the Rugby League International Federation in 2011 and 2013; in Narrabri, New South Wales Died: Alfredo Ovando Candia, 65, President of Bolivia from 1969 to 1970 Karol Borsuk, 76, Polish mathematician and topologist known for the theories of absolute retracts (ARs) and absolute neighborhood retracts (ANRs), as well as the Borsuk-Spanier cohomotopy groups, Borsuk's conjecture, the Borsuk–Ulam theorem and the Bing–Borsuk conjecture. Fernando Sánchez Polack, 61, Spanish film actor with appearances in 110 films, primarily Westerns, from 1959 to 1992, died from a cardiac arrest.
Sources: en.wikipedia.org
== Function == Many oligopeptides with an N-Formylmethionine N-terminal residue—such as the prototypical tripeptide N-Formylmethionine-leucyl-phenylalanine (FMLP)—are products of bacterial protein synthesis. These formylated peptides stimulate granulocytes to migrate directionally (see chemotaxis), and to engage in phagocytosis and bacterial killing, thereby contributing to host defense by directing the innate immune response during acute inflammation. Early studies indicated that these peptides act through a receptor-mediated mechanism. To investigate this, researchers used the human leukocyte cell line HL-60, which consists of promyelocytes that do not respond to FMLP. Upon differentiation into granulocytes, which do respond, the cells were used to partially purify and clone a gene. When this gene was transfected into FMLP-unresponsive cells, it conferred responsiveness to FMLP and other N-formyl oligopeptides. This receptor was initially named the formyl peptide receptor (FPR). Subsequently, two additional genes were cloned, encoding receptor-like proteins with high sequence similarity to FPR. These three receptors were initially named inconsistently but are now designated formyl peptide receptor 1 (FPR1), formyl peptide receptor 2 (FPR2; this gene), and formyl peptide receptor 3 (FPR3). FPR2 and FPR3 are grouped with FPR1 based on sequence homology, not ligand specificity. Indeed, FPR2 exhibits markedly different ligand preferences and biological functions compared to FPR1, while FPR3 does not bind FMLP or most other N-formyl peptides that activate FPR1 or FPR2.
will lead to a dimension-different PseAA composition. Using Eq.6 is just one of the many modes for deriving the correlation factors in PseAAC or its components. The others, such as the physicochemical distance mode and amphiphilic pattern mode, can also be used to derive different types of PseAAC, as summarized in a 2009 review article. In 2011, the formulation of PseAAC (Eq.3) was extended to a form of the general PseAAC as given by:
== Further Information == ASTM E1588-10e1, Standard Guide for GSR analysis by Scanning Electron Microscopy/Energy Dispersive X-ray Spectrometry, American Society for Testing and Materials, West Conshohocken, PA, 2010. E. Boehm, Application of the SEM in forensic medicine, Scanning Electron Microscopy (1971) 553–560. M Christopher, J Warmenhoven, FS Romolo, M Donghi, R Webb, C Jeynes, NI Ward, A New Quantitative Method for Gunshot Residue Analysis by Ion Beam Analysis. Analyst, 2013, 138, 4649. O. Dalby, D. Butler, J.W. Birkett, Analysis of Gunshot Residue and Associated Materials—A Review, J. Forens. Sci. 55 (2010) 924–943. M. Grima, M. Butler, R. Hanson, A. Mohameden, Firework displays as sources of particles similar to gunshot residue, Science and Justice 52 (1) (2012) 49–57. H.H. Meng, B. Caddy, Gunshot residue analysis - review, J. Forens. Sci. 42 (1997) 553–570. P.V. Mosher, M.J. McVicar, E.D. Randall, E.H. Sild, Gunshot residue-similar particles produced by fireworks, Journal of the Canadian Society of Forens. Sci. 31 (3)(1998) 157–168. F.S. Romolo, M.E. Christopher, M. Donghi, L. Ripani, C. Jeynes, R.P. Webb, N.I. Ward, Integrated Ion Beam Analysis (IBA) in Gunshot Residue (GSR) characterisation. Forensic Sci. Int. 231 (2013), 219–228. F.S. Romolo. Advances in Analysis of Gunshot Residue. In Emerging Technologies for the analysis of forensic traces, Edited by Simona Francese, Springer Publishing Company, pagine 183–202, ISBN 978-3-030-20541-6. A.J. Schwoeble, D.L. Exline, Current Methods in Forensic Gunshot Residue Analysis, (2000) CRC Press LLC. J.S. Wallace, J.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.
Selank is a synthetic analogue built on the tuftsin tetrapeptide Thr-Lys-Pro-Arg. Extra proline residues were added to the C-terminus during design work. That modification is intended to make the peptide less vulnerable to rapid enzymatic degradation.
Transliteration from Russian produces variant spellings such as Selanc. Many suppliers avoid the trade-style name entirely and list the peptide sequence. Comparing sequences rather than names is the reliable way to confirm two entries describe the same molecule.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.