Enkephalinase comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-03-31. Where a claim depends on a specific study, the study is described rather than over-claimed.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
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.
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.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
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.
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.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
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.
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Anti-obesity medication or weight loss medications are pharmacological agents that reduce excess body fat and cause weight loss. These medications alter one of the fundamental processes of weight regulation, by: reducing appetite and consequently energy intake, increasing energy expenditure, redirecting nutrients from adipose to lean tissue, or interfering with the absorption of calories. Weight loss drugs have been developed since the early twentieth century, and many have been banned or withdrawn from the market due to adverse effects, including deaths; other drugs proved ineffective. Although many earlier drugs were stimulants such as amphetamines, in the early 2020s, GLP-1 receptor agonists became popular for weight loss. As of 2023, the medications liraglutide, naltrexone/bupropion, orlistat, semaglutide, tirzepatide and phentermine/topiramate are approved by the US Food and Drug Administration (FDA) for weight management in combination with reduced-calorie diet and increased physical activity. Medications to treat obesity may be considered in those with a body mass index above 30, or above 27 with obesity related complications (such as hypertension, hyperlipidemia, cardiovascular disease, or obstructive sleep apnea). As of 2022, no medication has been shown to be as effective at long-term weight reduction as bariatric surgery.
=== On multi drug resistant cancer cells === Poloxamers have been shown to preferentially target cancer cells, due to differences in the membrane of these cells when compared to noncancer cells. Poloxamers have also been shown to inhibit MDR proteins and other drug efflux transporters on the surface of cancer cells; the MDR proteins are responsible for the efflux of drugs from the cells and hence increase the susceptibility of cancer cells to chemotherapeutic agents such as doxorubicin. Another effect of the polymers upon cancer cells is the inhibition of the production of ATP in multi-drug resistant (MDR) cancer cells. The polymers seem to inhibit respiratory proteins I and IV, and the effect on respiration seems to be selective for MDR cancer cells, which may be explained by the difference in fuel sources between MDR and sensitive cells (fatty acids and glucose respectively). The poloxamers have also been shown to enhance proto-apoptotic signaling, decrease anti-apoptoic defense in MDR cells, inhibit the glutathione/glutathione S-transferase detoxification system, induce the release of cytochrome C, increase reactive oxygen species in the cytoplasm, and abolish drug sequestering within cytoplasmic vesicles.
== Adverse effects == The most widely reported side effect of glycyrrhizin use via consumption of black liquorice is reduction of blood potassium levels, which can affect body fluid balance and function of nerves. Chronic consumption of black licorice, even in moderate amounts, is associated with an increase in blood pressure, may cause irregular heart rhythm, and may have adverse interactions with prescription drugs. In extreme cases, death can occur as a result of excess consumption.
Denmark's long-term economic development has largely followed the same pattern as other Northwestern European countries. In most of recorded history Denmark has been an agricultural country with most of the population living on a subsistence level. Since the 19th century, Denmark has gone through an intense technological and institutional development. The material standard of living has experienced formerly unknown rates of growth, and the country has been industrialized and later turned into a modern market-economy society. Almost all of the land area of Denmark is arable. Unlike most of its neighbours, Denmark has not had extractable deposits of minerals or fossil fuels, except for the deposits of oil and natural gas in the North Sea, which started playing an economic role only during the 1980s. On the other hand, Denmark has had a logistic advantage through its long coastal line and the fact that no point on Danish land is more than 50 kilometers from the sea – an important fact for the whole period before the industrial revolution when sea transport was cheaper than land transport. Consequently, foreign trade has always been very important for the economic development of Denmark.
Sources: en.wikipedia.org
==== Biographies ==== Collins, Jon. Rush: Chemistry: The Definitive Biography. Helter Skelter Publishing, 2006. ISBN 1-900924-85-4 (hardcover). Gett, Steve. Rush: Success Under Pressure. Cherry Lane Books, 1984. ISBN 0-89524-230-3. Harrigan, Brian. Rush. Omnibus Press, 1982. ISBN 0-86001-934-9. Popoff, Martin. Rush: The Illustrated History. Voyageur Press, 2013. ISBN 978-0760349953. Popoff, Martin. Anthem: Rush in the '70s. ECW Press, 2020. ISBN 9781770415201. Popoff, Martin. Limelight: Rush in the '80s. ECW Press, 2020. ISBN 9781770415362. Popoff, Martin. Driven: Rush in the '90s and "In the End". ECW Press, 2021. ISBN 9781770415379.
== Discovery and general principles == FFF was devised and first published by J. Calvin Giddings in 1966 and in 1976. Giddings had published many articles on flow-FFF which is the most important FFF technique today. Giddings, credited for the invention of FFF, was professor of chemistry and specialist of chromatography and separation techniques at the University of Utah.
=== DNA repair === RECQL4 has a crucial role in DNA end resection that is the initial step required for homologous recombination (HR)-dependent double-strand break repair. When RECQL4 is depleted, HR-mediated repair and 5' end resection are severely reduced in vivo. RECQL4 also appears to be necessary for other forms of DNA repair including non-homologous end joining, nucleotide excision repair and base excision repair. The association of deficient RECQL4-mediated DNA repair with accelerated aging is consistent with the DNA damage theory of aging.
=== Breast cancer === Docetaxel and paclitaxel have comparable efficacy metastatic breast cancer but paclitaxel has less severe side effects. Additionally, it has been noted that docetaxel is prone to cellular drug resistance via a variety of different mechanisms.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.