If you have been reading about heptapeptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-11-15. Where a claim depends on a specific study, the study is described rather than over-claimed.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
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.
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.
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.
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.
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.
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.
=== Detector === A Faraday cup measures the ion current hitting a metal cup, and is sometimes used for high-current secondary-ion signals. With an electron multiplier, an impact of a single ion starts off an electron cascade, resulting in a pulse of 108 electrons, which is recorded directly. A microchannel plate detector is similar to an electron multiplier, with lower amplification factor but with the advantage of laterally-resolved detection. Usually it is combined with a fluorescent screen, and signals are recorded either with a CCD-camera or with a fluorescence detector.
=== Mechanism of action === Elbasvir targets the NS5A protein, which effectively prevents the transcription of the HCV RNA and also prevents virion assembly. "Median EC50 values range from 0.2 to 3600 pmol/L, based on genotype." Grazoprevir is an protease inhibitor targeting HCV NS3/4A serine protease. Effectively grazoprevir prevents cleavage of the necessary polyproteins for replication.
== Notes == An α indicates the medicine is on the complementary list for which specialized diagnostic or monitoring or training is needed. An item may also be listed as complementary on the basis of higher costs or a less attractive cost-benefit ratio.
Chemical energy (or "chemical fuels") was an attractive option at the beginning, given the broad array of reversible chemical reactions (heavily based on acid-base chemistry) to switch molecules between different states. However, this comes with the issue of practically regulating the delivery of the chemical fuel and the removal of waste generated to maintain the efficiency of the machine as in biological systems. Though some AMMs have found ways to circumvent this, more recently waste-free reactions such based on electron transfers or isomerization have gained attention (such as redox-responsive viologens). Eventually, several different forms of energy (electric, magnetic, optical and so on) have become the primary energy sources used to power AMMs, even producing autonomous systems such as light-driven motors.
Sources: en.wikipedia.org
The subcutaneous tissue (also hypodermis) is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (the subcutaneous tissue contains 50% of body fat). Fat serves as padding and insulation for the body. Microorganisms like Staphylococcus epidermidis colonize the skin surface. The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings.
Early civilizations, such as the Egyptians, Babylonians, and Indians, amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but did not develop a systematic theory. A basic chemical hypothesis first emerged in Classical Greece with the theory of four elements as propounded definitively by Aristotle stating that fire, air, earth and water were the fundamental elements from which everything is formed as a combination. Greek atomism dates back to 440 BC, arising in works by philosophers such as Democritus and Epicurus. In 50 BCE, the Roman philosopher Lucretius expanded upon the theory in his poem De rerum natura (On The Nature of Things). Unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments. An early form of the idea of conservation of mass is the notion that "Nothing comes from nothing" in Ancient Greek philosophy, which can be found in Empedocles (approx. 4th century BC): "For it is impossible for anything to come to be from what is not, and it cannot be brought about or heard of that what is should be utterly destroyed." and Epicurus (3rd century BC), who, describing the nature of the Universe, wrote that "the totality of things was always such as it is now, and always will be".
In September 2013, the Supreme People's Court authorized a three-year prison term for bloggers who shared more than 500 times any content considered "defamatory". In 2014, the Chinese government launched the Cleaning the Web campaign, aiming to crack down on pornographic, vulgar, and politically questionable content. It also launched Operation Qinglang campaigns since 2016 to "clean up" the Chinese internet. China under Xi has taken a strong stand to control internet usage inside China, including Google, Facebook and Wikipedia, advocating Internet censorship under the concept of internet sovereignty. Likewise, the situation for users of Weibo has been described as a change from fearing one's account would be deleted, to fear of arrest. The Provisions on the Governance of the Online Information Content Ecosystem, which came into effect in 2020, defined the scope of legal expression for service platforms and content creators. Under Xi's administration, China started enforcing an Internet real-name system for online platforms, requiring them to collect users' real names, ID numbers, and other information when providing services.
Sources: en.wikipedia.org
DiCaprio's second role in 2010 was in Christopher Nolan's critically acclaimed ensemble science-fiction film Inception. Inspired by the experience of lucid dreaming and dream incubation, the film features Dom Cobb (DiCaprio), an "extractor" who enters the dreams of others to obtain information that is otherwise inaccessible. Cobb is promised a chance to regain his old life in exchange for planting an idea in a corporate target's mind. DiCaprio was fascinated with the idea of a "dream-heist" and the potential for his character to manipulate his dreamworld and impact his real life. Made on a budget of $160 million, the film grossed $836 million worldwide to become DiCaprio's second highest-grossing film. To star in this film, DiCaprio agreed to a pay cut from his $20 million fee and opted for a share in first-dollar gross points, which entitled him to a percentage of the cinema ticket sales. The risk proved fruitful, as DiCaprio earned $50 million from the film, becoming his highest payday yet. DiCaprio starred as J. Edgar Hoover in Clint Eastwood's J. Edgar (2011). A biopic about Hoover, the film focuses on his career as an FBI director, including an examination of his private life as an alleged closeted homosexual. Critics felt that the film lacked coherence overall but commended DiCaprio's performance. Roger Ebert praised DiCaprio's ability to bring depth and nuance to the character, suggesting that his performance conveyed aspects of Hoover's personality that were possibly even unknown to the man himself.
The eating habits of Komodo dragons follow a hierarchy, with the larger animals generally eating before the smaller ones. The largest male typically asserts his dominance and the smaller males show their submission by use of body language and rumbling hisses. Dragons of equal size may resort to "wrestling". Losers usually retreat, though they have been known to be killed and eaten by victors. The Komodo dragon's diet varies depending on stage of growth. Young Komodo dragons will eat insects, birds and bird's eggs and small reptiles, while larger Komodo dragons (typically over 20 kg (44 lb)) prefer large ungulate prey, such as Javan rusa deer, wild pigs and water buffalo. Occasionally, they attack and bite humans. Sometimes they consume human corpses, digging up bodies from shallow graves. This habit of raiding graves caused the villagers of Komodo to move their graves from sandy to clay ground, and pile rocks on top of them, to deter the lizards. Dwarf species of Stegodon (a proboscidean related to living elephants) are suggested to have been a primary prey item of the Komodo dragon during the Pleistocene, prior to the introduction of their modern ungulate prey, which were only introduced to the islands in the Holocene, around 10-7,000 years ago. The Komodo dragon drinks by sucking water into its mouth via buccal pumping (a process also used for respiration), lifting its head, and letting the water run down its throat.
The "d-" in the name d-ribose refers to the stereochemistry of the chiral carbon atom farthest away from the aldehyde group (C4'). In d-ribose, as in all d-sugars, this carbon atom has the same configuration as in d-glyceraldehyde.Relative abundance of forms of ribose in solution: β-d-ribopyranose (59%), α-d-ribopyranose (20%), β-d-ribofuranose (13%), α-d-ribofuranose (7%) and open chain (0.1%). For ribose residues in nucleosides and nucleotides, the torsion angles for the rotation encompassing the bonds influence the configuration of the respective nucleoside and nucleotide. The secondary structure of a nucleic acid is determined by the rotation of its 7 torsion angles. Having a large amount of torsion angles allows for greater flexibility. In closed ring riboses, the observed flexibility mentioned above is not observed because the ring cycle imposes a limit on the number of torsion angles possible in the structure. Conformers of closed form riboses differ in regards to how the lone oxygen in the molecule is positioned respective to the nitrogenous base (also known as a nucleobase or just a base) attached to the ribose. If a carbon is facing towards the base, then the ribose is labeled as endo. If a carbon is facing away from the base, then the ribose is labeled as exo. If there is an oxygen molecule attached to the 2' carbon of a closed cycle ribose, then the exo confirmation is more stable because it decreases the interactions of the oxygen with the base.
Encouraged by women in the community, it is primarily intended to protect chastity, deter promiscuity, and offer protection from assault. By 2013, UNICEF in conjunction with the Somali authorities reported that the prevalence rate among 1- to 14-year-old girls in the autonomous northern Puntland and Somaliland regions had dropped to 25% following a social and religious awareness campaign. About 93% of Somalia's male population is also reportedly circumcised. Somalia has one of the lowest HIV infection rates on the continent. This is attributed to the Muslim nature of Somali society and adherence of Somalis to Islamic morals. While the estimated HIV prevalence rate in Somalia in 1987 (the first case report year) was 1% of adults, a 2012 report from UNAIDS says that since 2004, estimates from 0.7% to 1.0% have been assumed. Although healthcare is now largely concentrated in the private sector, the country's public healthcare system is in the process of being rebuilt, and is overseen by the Ministry of Health. The Minister of Health is Qamar Adan Ali. The autonomous Puntland region maintains its own Ministry of Health, as does the Somaliland region in northwestern Somalia.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
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.