The short version of heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-07. Anything still debated is marked as such rather than presented as settled.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
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.
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.
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.
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.
Various labs jointly conducted thousands of repetitive chromatographic experiments between 1988 and 1993. All group 5 elements and protactinium were extracted from concentrated hydrochloric acid; after mixing with lower concentrations of hydrogen chloride, small amounts of hydrogen fluoride were added to start selective re-extraction. Dubnium showed behavior different from that of tantalum but similar to that of niobium and its pseudohomolog protactinium at concentrations of hydrogen chloride below 12 moles per liter. This similarity to the two elements suggested that the formed complex was either DbOX−4 or [Db(OH)2X4]−. After extraction experiments of dubnium from hydrogen bromide into diisobutyl carbinol (2,6-dimethylheptan-4-ol), a specific extractant for protactinium, with subsequent elutions with the hydrogen chloride/hydrogen fluoride mix as well as hydrogen chloride, dubnium was found to be less prone to extraction than either protactinium or niobium. This was explained as an increasing tendency to form non‐extractable complexes of multiple negative charges. Further experiments in 1992 confirmed the stability of the +5 state: Db(V) was shown to be extractable from cation‐exchange columns with α‐hydroxyisobutyrate, like the group 5 elements and protactinium; Db(III) and Db(IV) were not. In 1998 and 1999, new predictions suggested that dubnium would extract nearly as well as niobium and better than tantalum from halide solutions, which was later confirmed. The first isothermal gas chromatography experiments were performed in 1992 with 262Db (half-life 35 seconds).
As part of a comprehensive modernization of German radiation protection law, which is largely based on Directive 2013/59/Euratom, the provisions of the X-Ray Ordinance have been incorporated into the revised Radiation Protection Ordinance. Among many other measures, contaminated food was withdrawn from the market on a large scale. Parents were strongly advised not to let their children play in sandboxes. Some of the contaminated sand was replaced. In 1989, the Federal Office for Radiation Protection was incorporated into the Ministry of the Environment. On April 30, 2003, a new precautionary radiation protection law was promulgated to implement two EU directives on the health protection of persons against the dangers of ionizing radiation during medical exposure. The protection of workers from optical radiation (infrared radiation (IR), visible light (VIS) and ultraviolet radiation (UV)), which falls under the category of non-ionizing radiation, is regulated by the Ordinance on the Protection of Workers from Artificial Optical Radiation of 19 July 2010. It is based on the EU Directive 2006/25/EC of April 27, 2006. On March 1, 2010, the "Act on the Protection of Humans from Non-Ionizing Radiation" (NiSG), BGBl. I p. 2433, came into force, according to which the use of sunbeds by minors has been prohibited since August 4, 2009, in accordance with § 4 NiSG [Network and Information Systems Security Ordinance – NIS Ordinance] (in German) A new Radiation Protection Act came into force in Germany on October 1, 2017.
=== Aneuploidy === Sex chromosomes Analysis of maternal serum cffDNA by high-throughput sequencing can detect common fetal sex chromosome aneuploidies such as Turner's syndrome, Klinefelter's syndrome and triple X syndrome but the procedure's positive predictive value is low.
==== Brazil ==== Working on public policies, Brazil hosts, for example, Instituto Liberdade, a University-based Center at Tecnopuc inside the Pontifícia Universidade Católica do Rio Grande do Sul, located in the South Region of the country, in the city of Porto Alegre. Instituto Liberdade is among the Top 40 think tanks in Latin America and the Caribbean, according to the 2009 Global Go To Think Tanks Index a report from the University of Pennsylvania's Think Tanks and Civil Societies Program (TTCSP). Fundação Getulio Vargas (Getulio Vargas Foundation (FGV)) is a Brazilian higher education institution. Its original goal was to train people for the country's public- and private-sector management. Today it hosts faculties (Law, Business, Economics, Social Sciences and Mathematics), libraries, and also research centers in Rio, São Paulo and Brasilia. It is considered by Foreign Policy magazine to be a top-five "policymaker think tank" worldwide. The Igarapé Institute is a Brazilian think tank focusing on public, climate, and digital security.
According to a study by Colombia's National Centre for Historical Memory, 220,000 people have died in the conflict between 1958 and 2013, most of them civilians (177,307 civilians, 40,787 fighters) and more than five million civilians were forced from their homes between 1985 and 2012, generating the world's second largest population of internally displaced persons (IDPs). The report shows that the humanitarian crisis in Colombia is extremely serious in terms of both lethal and nonlethal violence: it examines the widespread use of sexual violence against women and girls as a weapon of war, as well as the invisibility of this phenomenon. 16.9% of the population in Colombia has been a direct victim of the war. 2.3 million children have been displaced from their homes, and 45,000 children have been killed, according to national figures cited by Unicef. In total, one in three of the 7.6 million registered victims of the conflict are children, and since 1985, 8,000 minors have disappeared. As of 2016, some 1,000 children have been forcibly recruited by some of the myriad armed groups in the country, 75 have been killed, and 65 schools have been damaged by fighting since peace talks with FARC began. According to the report "Basta ya", written in 2013 by Colombia's National Centre for Historical Memory, 80% of victims affected by conflict-related violence and landmines were civilians. The report documents 1,982 massacres between 1980 and 2012. The Government also began a process of assistance, attention, and comprehensive reparation for victims of conflict.
Sources: en.wikipedia.org
== Structure == Lipoprotein(a) [Lp(a)] consists of an LDL-like particle and the specific apolipoprotein(a), which is bound covalently to the apoB contained in the outer shell of the particle. Lp(a) plasma concentrations are highly heritable and mainly controlled by the LPA gene located on chromosome 6q25.3–q26. Apo(a) proteins vary in size due to a size polymorphism [KIV-2 VNTR], which is caused by a variable number of kringle IV repeats in the LPA gene. This size variation at the gene level is expressed on the protein level as well, resulting in apo(a) proteins with 10 to more than 50 kringle IV repeats (each of the variable kringle IV consists of 114 amino acids). These variable apo(a) sizes are known as "apo(a) isoforms". There is a general inverse correlation between the size of the apo(a) isoform and the Lp(a) plasma concentration. One theory explaining this correlation involves different rates of protein synthesis. Specifically, the larger the isoform, the more apo(a) precursor protein accumulates intracellularly in the endoplasmic reticulum. Lp(a) is not fully synthesised until the precursor protein is released from the cell, so the slower production rate for the larger isoforms limits the plasma concentration.
The properties of phalloidin make it a useful tool for investigating the distribution of F-actin in cells by labeling phalloidin with fluorescent analogs and using them to stain actin filaments for light microscopy. Fluorescent derivatives of phalloidin have turned out to be enormously useful in localizing actin filaments in living or fixed cells as well as for visualizing individual actin filaments in vitro. A high-resolution technique was developed to detect F-actin at the light and electron microscopic levels by using phalloidin conjugated to the fluorophore eosin which acts as the fluorescent tag. In this method known as fluorescence photo-oxidation, fluorescent molecules can be utilized to drive the oxidation of diaminobenzidine (DAB) to create a reaction product that can be rendered electron dense and detectable by electron microscopy. The amount of fluorescence visualized can be used as a quantitative measure of the amount of filamentous actin there is in cells if saturating quantities of fluorescent phalloidin are used. Consequently, immunofluorescence microscopy along with microinjection of phalloidin can be used to evaluate the direct and indirect functions of cytoplasmic actin in its different stages of polymer formation. Therefore, fluorescent phalloidin can be used as an important tool in the study of actin networks at high resolution.
dodecapeptide located in the C-terminal of the fibrinogen γ chain (the most important) RGD sequence of the α chain → the Arginine-Glycine-Aspartate amino acid sequence This complex also binds vWF, fibronectin and vitronectin. In the resting state the contact between the two protein subunits (necessary for the complex activation) is prevented by aggregin, which disables their contact necessary for the complex activation. The complex can be activated by ADP. When bound to ADP, conformational changes occur within the aggregin molecule and consequently, it dissociates from the two subunits. Furthermore, the complex can be activated by thrombin. Thrombin binding to its receptor activates protein kinase C and increases the level of inositol triphosphate. Consequently, there is a release of calcium ions that activate calpain. Calpain cleaves aggregin, and thus allows for joining of the two subunits. Deficiency in the IIb / IIIa complex is described as Glanzmann's thrombasthenia. Patients completely lack the ability to aggregate platelets.
Minimal change disease is characterised as a cause of nephrotic syndrome without visible changes in the glomerulus on microscopy. Minimal change disease typically presents with edema, an increase in proteins passed from urine and decrease in blood protein levels, and an increase in circulating lipids (i.e., nephrotic syndrome) and is the most common cause of the nephrotic syndrome in children. Although no changes may be visible by light microscopy, changes on electron microscopy within the glomeruli may show a fusion of the foot processes of the podocytes lining the basement membrane of the capillaries of glomerulus. It is typically managed with corticosteroids and does not progress to chronic kidney disease.
Sources: en.wikipedia.org
=== Epithelialization === The formation of granulation tissue into an open wound allows the reepithelialization phase to take place, as epithelial cells migrate across the new tissue to form a barrier between the wound and the environment. Basal keratinocytes from the wound edges and dermal appendages such as hair follicles, sweat glands and sebaceous (oil) glands are the main cells responsible for the epithelialization phase of wound healing. They advance in a sheet across the wound site and proliferate at its edges, ceasing movement when they meet in the middle. In healing that results in a scar, sweat glands, hair follicles and nerves do not form. With the lack of hair follicles, nerves and sweat glands, the wound, and the resulting healing scar, provide a challenge to the body with regards to temperature control. Keratinocytes migrate without first proliferating. Migration can begin as early as a few hours after wounding. However, epithelial cells require viable tissue to migrate across, so if the wound is deep it must first be filled with granulation tissue. Thus the time of onset of migration is variable and may occur about one day after wounding. Cells on the wound margins proliferate on the second and third day post-wounding in order to provide more cells for migration. If the basement membrane is not breached, epithelial cells are replaced within three days by division and upward migration of cells in the stratum basale in the same fashion that occurs in uninjured skin.
Berzelius made some initial characterisations of the new metal and its chemical compounds: he correctly determined that the thorium–oxygen mass ratio of thorium oxide was 7.5 (its actual value is close to that, ~7.3), but he assumed the new element was divalent rather than tetravalent, and so calculated that the atomic mass was 7.5 times that of oxygen (120 Da); it is actually 15 times as large. He determined that thorium was a very electropositive metal, ahead of cerium and behind zirconium in electropositivity. Metallic thorium was isolated for the first time in 1914 by Dutch entrepreneurs Dirk Lely Jr. and Lodewijk Hamburger.
== History == The drug appeared briefly on the black market in the early 1980s, prior to the enactment of the Federal Analog Act, which sought to regulate entire classes of substances based on structural similarity rather than scheduling each one individually as it emerged. Fentanyl analogs have been responsible for hundreds of fatalities across Europe and the former Soviet republics since their re-emergence in Estonia in the early 2000s, and new derivatives continue to appear. In 2013, the Drug Enforcement Administration (DEA) established an aggregate production quota of 2 grams (0.071 oz) for acetyl-alpha-methylfentanyl.
=== Crown Dependencies === The Guernsey Football Association, Jersey Football Association, and the Isle of Man Football Association have no international recognition; they have county status within the English Football Association.
The list of minerals required for plants is similar to that for animals. Both use very similar enzymes, although differences exist. For example, legumes host molybdenum-containing nitrogenase, but animals do not. Many animals rely on hemoglobin (Fe) for oxygen transport, but plants do not. Fertilizers are often tailored to address mineral deficiencies in particular soils. Examples include molybdenum deficiency, manganese deficiency, zinc deficiency, and so on.
Sources: en.wikipedia.org
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
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.