The short version of Heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Derived from the seven-residue sequence |
| Molecular weight | About 751.9 g/mol | Average mass; the monoisotopic value is slightly lower |
| Residue count | Seven amino acids | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent compound | Tuftsin (Thr-Lys-Pro-Arg) | Selank extends tuftsin at the C-terminus |
| Compound class | Synthetic short peptide | Studied in a research setting; not a licensed drug in most markets |
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.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
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.
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
== Early life and education == Freeman was born on June 1, 1937, in Memphis, Tennessee. He is the son of Mamie Edna (née Revere; 1912–2000), a teacher, and Morgan Porterfield Freeman (July 6, 1915 – April 27, 1961), a barber, who died of cirrhosis in 1961. He has three older siblings. Some of Morgan's great-great-grandparents were slaves who migrated from North Carolina to Mississippi. He later discovered that his white maternal great-great-grandfather had lived with and was buried beside Freeman's black great-great-grandmother in the segregated South, as the two could not legally marry at the time. A DNA test suggested that among all of his African ancestors, a little over one-quarter came from the area that stretches from present-day Senegal to Liberia and three-quarters came from the Congo-Angola region. As an infant, Freeman was sent to his paternal grandmother in Charleston, Mississippi. He moved frequently during his childhood, living in Greenwood, Mississippi, Gary, Indiana, and finally Chicago. He made his acting debut aged nine, playing the lead role in a school play. He then attended Broad Street High School, a building which serves today as Threadgill Elementary School in Greenwood. At the age of 12, he won a statewide drama competition, and while settling into school, discovered music and theater. When Freeman was 16 years old, he contracted pneumonia. Freeman graduated from high school in 1955, but turned down a partial drama scholarship from Jackson State University, opting instead to enlist in the United States Air Force.
=== Origins === Modern dentistry in Chengdu developed in the early 20th century through the work of Western medical missionaries. Ashley Woodward Lindsay, a graduate of the Royal College of Dental Surgeons of Ontario in Toronto, left Canada for Chengdu in 1907. With assistance from physician and missionary Omar L. Kilborn, Lindsay established a dental clinic on Sishengci Street. A history published through China's National Health Commission describes the clinic as marking the beginning of modern dentistry in Chengdu. Sichuan University dates the institutional history of the present hospital to the establishment of the Renji Dental Clinic in 1907. It records the expansion of the clinic into the Renji Dental Hospital in 1912. The hospital describes the 1912 institution as China's first specialized dental hospital. West China Union University, a missionary-founded university established in Chengdu in 1910, subsequently became the principal institutional base for Lindsay's dental work. In 1917, the university established its dental education program. The dental school at West China Union University was the earliest dental education institution in China. Several early faculty members were trained at the University of Toronto Faculty of Dentistry, which credits these dentists with helping introduce a university-based model of dental education to China and with contributing to the development of national dental-education standards. In the late 1920s the medical and dental programs of West China Union University were brought into a combined academic structure.
=== Microwave-induced plasma === Microwave induced plasma ion sources are capable of exciting electrodeless gas discharges to create ions for trace element mass spectrometry. A microwave plasma has high frequency electromagnetic radiation in the GHz range. It is capable of exciting electrodeless gas discharges. If applied in surface-wave-sustained mode, they are especially well suited to generate large-area plasmas of high plasma density. If they are both in surface-wave and resonator mode, they can exhibit a high degree of spatial localization. This allows to spatially separate the location of plasma generations from the location of surface processing. Such a separation (together with an appropriate gas-flow scheme) may help reduce the negative effect, that particles released from a processed substrate may have on the plasma chemistry of the gas phase.
Sources: en.wikipedia.org
The Jameson Raid (Afrikaans: Jameson-inval, lit. ''Jameson's Invasion'', 29 December 1895 – 2 January 1896) was a botched raid against the South African Republic (commonly known as the Transvaal) carried out by British colonial administrator Leander Starr Jameson, under the employment of Cecil Rhodes. It involved 500 British South Africa Company police and was launched from Rhodesia over the New Year weekend of 1895–96. Paul Kruger, for whom Rhodes had great personal hatred, was president of the South African Republic at the time. The raid was intended to trigger an uprising by the primarily British expatriate and settler workers (known as Uitlanders) in the Transvaal, but it failed. The workers were referred to as the Johannesburg Conspirators. They were expected to recruit an army and prepare for an insurrection; however, the raid was ineffective, and no uprising took place. The results included embarrassment of the British government; the replacement of Cecil Rhodes as prime minister of the Cape Colony; and the strengthening of Boer dominance of the Transvaal and its gold mines. Also, the withdrawal of so many fighting men left Rhodesia vulnerable, one factor that led just a couple of months later to the Second Matabele War. The raid was a contributory cause of the Second Boer War.
=== High-pressure reserve gas === An alternative to a low-pressure compressor for gas supply is high-pressure gas storage cylinders feeding through a pressure regulator which will be set to the required supply pressure for the depth and equipment in use. In practice HP storage may be used for either reserve gas supply or both main and reserve gas supplies to a gas panel. High-pressure bulk cylinders are quiet in operation and provide gas of known quality (if it has been tested). This allows the relatively simple and reliable use of nitrox mixtures in surface-supplied diving. Bulk cylinders are also quiet in operation compared to a low-pressure compressor, but have the obvious limitation of amount of gas available. The usual configurations for surface-supplied bulk gas storage are large single cylinders of around 50 litres water capacity, often referred to as "J"s or "bombs", "quads", which are a group (sometimes, but not necessarily four in number) of similar cylinders mounted on a frame and connected together to a common supply fitting, and "kellys" which are a group of "gas storage tubes" (long large volume seamless transportable gas storage pressure vessels, with water capacity between 150 litres (5.3 cu ft) and 3,000 litres (110 cu ft)) usually mounted in a container frame or trailer, and usually connected together to a manifold with a common connection fitting.
=== From specimen collection === Most causes of in vitro hemolysis are related to specimen collection. Difficult collections, unsecure line connections, contamination, and incorrect needle size, as well as improper tube mixing and incorrectly filled tubes are all frequent causes of hemolysis. In vitro hemolysis during specimen collection can cause inaccurate laboratory test results by contaminating the surrounding plasma with the contents of hemolyzed red blood cells. For example, the concentration of potassium inside red blood cells is much higher than in the plasma and so an elevated potassium level is usually found in biochemistry tests of hemolyzed blood. After the blood collection process, in vitro hemolysis can still occur in a sample due to external factors, such as prolonged storage, incorrect storage conditions and excessive physical forces by dropping or vigorously mixing the tube.
=== Society === Little is revealed of the Combine's activities outside of Earth, but dialogue in Half-Life 2 states that they control worlds of various dimensions inhabited by a range of species. The Combine occupation of Earth is shown to be a brutal totalitarian police state. In City 17, an Eastern European city, Civil Protection units routinely conduct searches of apartment blocks, interrogating human citizens, and engaging in wanton police brutality. The military Overwatch forces of the Combine attack human resistance bases in an effort to further solidify their authority in the urban centers. Human citizens are clad in blue uniforms, living in designated apartment blocks and move around to different cities or locales in passenger trains by the Combine's will. Vortigaunts, enemy alien creatures from Half-Life, have also been enslaved, and are observed in various professions such as janitors. According to Half-Life 2: Raising the Bar, the Combine are draining Earth's oceans and resources to be used on other Combine worlds. The heart of the Combine's command over Earth in Half-Life 2 is the Citadel, a large tower constructed by them which reaches both tens of thousands of feet (several or several tens of kilometres) into the sky and deep underground. Located within City 17, the Citadel serves as the Combine's headquarters on Earth, housing Combine Advisors and the office of Earth's administrator, Dr. Wallace Breen. Breen, a puppet ruler, is frequently seen on large screens around the city on which he spreads propaganda and makes announcements.
Sources: en.wikipedia.org
The important thing is not that scientists may disagree on where their responsibility to society lies, but that they are conscious that a responsibility exists, are vocal about it, and when they speak out they expect to affect policy. Otto Hahn, it would seem, was even more than just an example of this twentieth-century conceptual evolution; he was a leader in the process. He was one of the signatories of the agreement to convene a convention for drafting a world constitution. As a result, for the first time in human history, a World Constituent Assembly convened to draft and adopt a Constitution for the Federation of Earth.
==== Esterification ==== HA can be reacted with an epoxide such as glycidyl methacrylate and triethylamine in water to form these ester bonds. Alkyl halides, tosylates, and diazomethane can also be used to create ester bonds, but this reaction requires you to convert the native HA sodium salt to its TBA salt, which can be time consuming. These esterification reactions at the carboxyl group usually require a low pH. There are many different types of esterification reactions at both the carboxyl and hydroxyl groups.
Strength training, also known as weight training or resistance training, is exercise designed to improve physical strength. It may involve lifting weights, bodyweight exercises (such as push-ups, pull-ups, and squats), isometrics (holding a position under tension, such as planks), and plyometrics (explosive movements like jump squats and box jumps). Training works by progressively increasing the force output of the muscles and uses a variety of exercises and types of equipment. Strength training is primarily an anaerobic activity, although circuit training also is a form of aerobic exercise. Strength training can increase muscle, tendon, and ligament strength as well as bone density, metabolism, and the lactate threshold; improve joint and cardiac function; and reduce the risk of injury in athletes and the elderly. For many sports and physical activities, strength training is central or is used as part of their training regimen.
== Transplanted human organoids == Bio- and electrical engineers have shown that human cerebral organoids transplanted into mice functionally integrate with their visual cortex. Such models may raise similar ethical issues as organoid-based humanization of other animals.
Usually the largest workers in the colony develop into repletes; and, if repletes are removed from the colony, other workers become repletes, demonstrating the flexibility of this particular polymorphism. This polymorphism in morphology and behaviour of workers initially was thought to be determined by environmental factors such as nutrition and hormones that led to different developmental paths; however, genetic differences between worker castes have been noted in Acromyrmex sp. These polymorphisms are caused by relatively small genetic changes; differences in a single gene of Solenopsis invicta can decide whether the colony will have single or multiple queens. The Australian jack jumper ant (Myrmecia pilosula) has only a single pair of chromosomes (with the males having just one chromosome as they are haploid), the lowest number known for any animal, making it an interesting subject for studies in the genetics and developmental biology of social insects.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.
Tuftsin contains four residues, while selank carries an additional Pro-Gly-Pro segment at the carboxyl end. That extension is intended to reduce enzymatic cleavage. Comparative pharmacokinetic data in humans remain limited.
No single receptor target is widely accepted as the definitive mediator of the reported effects. Proposed contributors include GABAergic modulation, shifts in monoamine turnover, and altered neuropeptide degradation. The mechanism is treated in the literature as unresolved.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.