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 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
| 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 |
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 developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
== Occurrence == The occurrence of unsaturated fats varies widely in nature. The saturated fatty acid components are almost exclusively stearic (C18) and palmitic acids (C16). Monounsaturated fats are almost exclusively oleic acid. Linolenic acid comprises most of the triunsaturated fatty acid component.
I mean, I'm happier than—I can't even express it!" A live performance of "Use This Gospel" with West and Sunday Service Choir came a few days later, ushering in a new era of Clipse live performances at music festivals and award shows. They appeared again on "Punch Bowl" by Nigo, from his album I Know Nigo! (2022). No Malice made a guest appearance (credited as Malice) on "I Pray for You" by Pusha T, from his fourth album, It's Almost Dry (2022). "Chains & Whips", the first song with Clipse as the primary artist since the reunion, was previewed on June 20, 2023. When asked about a potential new album in a live interview on November 16, 2023, Malice responded "Not at this time" with a smile. An upcoming album was confirmed in a story for magazine Greatest, published December 1, 2023.
== Production == As 225Ac does not occur in any appreciable quantities in nature, it must be synthesized in specialized nuclear reactors or accelerators. The majority of 225Ac results from the alpha decay of 229Th, but this supply is limited because the decay of 229Th (half-life 7920 years) is slow. It is also possible to breed 225Ac from radium-226 in the 226Ra(p,2n) reaction. This was first done in 2005, though the production and handling of 226Ra are difficult because of the respective cost of extraction and hazards of decay products such as radon-222. Alternatively, 225Ac can be produced in spallation reactions on a 232Th target irradiated with high-energy proton beams. Current techniques enable the production of millicurie quantities of 225Ac; however, it must then be separated from other reaction products. This is done by allowing some of the shorter-lived nuclides to decay; actinium isotopes are then chemically purified in hot cells and 225Ac is concentrated. Special care must be taken to avoid contamination with the longer-lived beta-emitting actinium-227. For decades, most 225Ac was produced in one facility—the Oak Ridge National Laboratory in Tennessee—further reducing this isotope's availability even with smaller contributions from other laboratories. Additional 225Ac is now produced from 232Th at Los Alamos National Laboratory and Brookhaven National Laboratory. The TRIUMF facility and Canadian Nuclear Laboratories have formed a strategic partnership around the commercial production of actinium-225.
Sources: en.wikipedia.org
However, the "absolute zero" on the Kelvin temperature scale was originally defined in terms of the second law of thermodynamics, which Thomson himself described in 1852. Thomson did not assume that this was equal to the "zero-volume point" of Charles's law, merely said that Charles's law provided the minimum temperature which could be attained. The two can be shown to be equivalent by Ludwig Boltzmann's statistical view of entropy (1870). However, Charles also stated:
== History == Thyroxine was first isolated in pure form in 1914 at the Mayo Clinic by Edward Calvin Kendall from extracts of hog thyroid glands. The hormone was synthesized in 1927 by British chemists Charles Robert Harington and George Barger.
It must be clear to anyone who has read any of my books that I have never been a Nazi sympathizer and I never have been anti-Semitic, and no amount of misquotation, mistranslation, or rearrangement of what I have written can alter the record of my true point of view. Nearly every one of these passages has been tampered with, either by malice or by ignorance. Furthermore, my friendly relations with a large group of Jewish colleagues and patients over a period of many years in itself disproves the charge of anti-Semitism. However, after the war Jung reportedly apologized to several of his Jewish colleagues, friends, and patients regarding his past statements about Jews.
The chromerids are a group of algae known from Australian corals which comprise some close photosynthetic relatives of the apicomplexans. The first member, Chromera velia, was discovered and first isolated in 2001. The discovery of Chromera velia with similar structure to the apicomplexans, provides an important link in the evolutionary history of the apicomplexans and dinophytes. Their plastids have four membranes, lack chlorophyll c and use the type II form of RuBisCO obtained from a horizontal transfer event.
Sources: en.wikipedia.org
=== Role in apoptosis === Cytochrome c was also discovered in 1996 by Xiaodong Wang to have an intermediate role in apoptosis, a controlled form of cell death used to kill cells in the process of development or in response to infection or DNA damage. Cytochrome c binds to cardiolipin in the inner mitochondrial membrane, thus anchoring its presence and keeping it from releasing out of the mitochondria and initiating apoptosis. While the initial attraction between cardiolipin and cytochrome c is electrostatic due to the extreme positive charge on cytochrome c, the final interaction is hydrophobic, where a hydrophobic tail from cardiolipin inserts itself into the hydrophobic portion of cytochrome c. During the early phase of apoptosis, mitochondrial ROS production is stimulated, and cardiolipin is oxidized by a peroxidase function of the cardiolipin–cytochrome c complex. The hemoprotein is then detached from the mitochondrial inner membrane and can be extruded into the soluble cytoplasm through pores in the outer membrane. The sustained elevation in calcium levels precedes cyt c release from the mitochondria. The release of small amounts of cyt c leads to an interaction with the IP3 receptor (IP3R) on the endoplasmic reticulum (ER), causing ER calcium release. The overall increase in calcium triggers a massive release of cyt c, which then acts in the positive feedback loop to maintain ER calcium release through the IP3Rs. This explains how the ER calcium release can reach cytotoxic levels. This release of cytochrome c in turn activates caspase 9, a cysteine protease.
Total population of the FR Yugoslavia – 10,019,657 Serbia (total): 9,396,411 Vojvodina: 2,116,725 Central Serbia: 5,479,686 Kosovo: 1,800,000 Montenegro: 623,246 Major cities (over 100,000 inhabitants) – 2002 data (2003 for Podgorica): Beograd (Belgrade): 1,280,639 (1,574,050 metro) Novi Sad: 215,600 (298,139 metro) Pristina: 200,000 (2002 estimate) Niš: 173,390 (234,863 metro) Kragujevac: 145,890 (175,182 metro) Podgorica: 139,500 (169,000 metro) Prizren: 121,000 (2002 estimate) Subotica: 99,471 (147,758 metro) More than half of Kosovo's pre-1999 Serb population (226,000), including 37,000 Romani, 15,000 Balkan Muslims (including Ashkali, Bosniaks, and Gorani), and 7,000 other non-Albanian civilians were expelled to central Serbia and Montenegro, following the Kosovo War. According to a 2004 estimate, the State Union had 10,825,900 inhabitants. According to a July 2006 estimate, the State Union had 10,832,545 inhabitants.
The identification of the heart as the seat of emotions in particular is due to the Roman physician Galen, who also located the seat of the passions in the liver, and the seat of reason in the brain. The heart also played a role in the Aztec system of belief. The most common form of human sacrifice practiced by the Aztecs was heart-extraction. The Aztec believed that the heart (tona) was both the seat of the individual and a fragment of the Sun's heat (istli). To this day, the Nahua consider the Sun to be a heart-soul (tona-tiuh): "round, hot, pulsating". In 2020, Indigenous elders including Unangan (Aleut) leader Illarion Merculieff and Hawaiian studies educator Sabra Kauka released a short film urging humanity to give the heart, rather than the intellect, a greater role in guiding action. In Catholicism, there has been a long tradition of veneration of the heart, stemming from worship of the wounds of Jesus Christ which gained prominence from the mid sixteenth century. This tradition influenced the development of the medieval Christian devotion to the Sacred Heart of Jesus and the parallel veneration of the Immaculate Heart of Mary, made popular by John Eudes.
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.
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.