The short version of heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Also in aqueous buffers |
| Typical purity (HPLC) | 95 percent or higher | Lot-dependent |
| Dry powder storage | Minus 20 degrees Celsius | Sealed, dry, protected from light |
| Solution storage | 2 to 8 degrees Celsius | Short-term use |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF |
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
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.
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.
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.
Homopolymers of amino acids (such as polylysine) can adopt α-helical structure at low temperature that is "melted out" at high temperatures. This helix–coil transition was once thought to be analogous to protein denaturation. The statistical mechanics of this transition can be modeled using an elegant transfer matrix method, characterized by two parameters: the propensity to initiate a helix and the propensity to extend a helix.
Counter-Strike: Source retains its team-based objective-oriented first-person shooter style gameplay. The aim of playing a map is to accomplish a map's objective: defusing the bomb, rescuing all hostages, or killing the entire opposing team. The ultimate goal of the game is to win more rounds than the opposing team. Once players are killed, they do not respawn until the next round, though this depends on which server people play on. This gameplay feature distinguishes Counter-Strike from other first-person shooter games, where players respawn instantly or after a short delay. Shooting while moving dramatically decreases accuracy, and holding the trigger down to continuously shoot produces severe recoil. The severity of damage induced by weaponry is dependent upon the specific locations of hits, with hits to the head being most lethal and shots which make contact elsewhere causing lesser loss of health. Damage is also affected by the distance, and if the target wears protection.
Unlike many medicines, insulin cannot be taken orally at the present time. Like nearly all other proteins introduced into the gastrointestinal tract, it is reduced to fragments (single amino acid components), whereupon all activity is lost. There has been some research into ways to protect insulin from the digestive tract, so that it can be administered in a pill. So far this is entirely experimental.
Sources: en.wikipedia.org
In 2016, a set of 355 genes likely present in the LUCA was identified. A total of 6.1 million prokaryotic genes from Bacteria and Archaea were sequenced, identifying 355 protein clusters from among 286,514 protein clusters that were probably common to the LUCA. The results suggest that the LUCA was anaerobic with a Wood–Ljungdahl (reductive Acetyl-CoA) pathway, nitrogen- and carbon-fixing, thermophilic. Its cofactors suggest dependence upon an environment rich in hydrogen, carbon dioxide, iron, and transition metals. Its genetic material was probably DNA, requiring the 4-nucleotide genetic code, messenger RNA, transfer RNA, and ribosomes to translate the code into proteins such as enzymes. LUCA likely inhabited an anaerobic hydrothermal vent setting in a geochemically active environment. It was evidently already a complex organism, and must have had precursors; it was not the first living thing. The physiology of LUCA has been in dispute. Previous research identified 60 proteins common to all life. Metabolic reactions inferred in LUCA are the incomplete reverse Krebs cycle, gluconeogenesis, the pentose phosphate pathway, glycolysis, reductive amination, and transamination.
=== Aggregation === Tropoelastin aggregates at physiological temperature due to interactions between hydrophobic domains in a process called coacervation. This process is reversible and thermodynamically controlled and does not require protein cleavage. The coacervate is made insoluble by irreversible crosslinking.
Californiconus J. K. Tucker & Tenorio, 2009 Conasprella Thiele, 1929 † Conilithes Swainson, 1840 † Contraconus Olsson & Harbison, 1953 Conus Linnaeus, 1758 † Eoconus J. K. Tucker & Tenorio, 2009 † Hemiconus Cossmann, 1889 † Herndliconus Petuch & Drolshagen, 2015 Kenyonia Brazier, 1896 Lilliconus G. Raybaudi Massilia, 1994 Malagasyconus Monnier & Tenorio, 2015 † Papilliconus Tracey & Craig, 2017 Profundiconus Kuroda, 1956 Pseudolilliconus J. K. Tucker & Tenorio, 2009 Pygmaeconus Puillandre & Tenorio, 2017 † Tequestaconus Petuch & Drolshagen, 2015 † The authors grouped 85% of all known cone snail species under Conus. They recognized 57 subgenera within Conus, and 11 subgenera within the genus Conasprella.
As of June 2021, Sputnik V is under rolling review process by EMA, but the marketing authorisation application was not submitted yet. Emergency use has also been authorized in Algeria, Bolivia, Serbia, the Palestinian territories, and Mexico. On 25 January 2021, Iran approved the vaccine, with Foreign Minister Mohammad Javad Zarif saying the country hopes to begin purchases and start joint production of the shot "in the near future", after Supreme Leader Ayatollah Ali Khamenei banned the government from importing vaccines from the United States and United Kingdom. The Czech Republic was also considering buying Sputnik V, and Prime Minister Andrej Babis dismissed the Minister of Health, Jan Blatný, who was a loud opponent to the use of Sputnik V. On 4 March 2021, EMA's human medicines committee (CHMP) has started a rolling review of Sputnik V (Gam-COVID-Vac), a COVID-19 vaccine developed by Russia's Gamaleya National Centre of Epidemiology and Microbiology. When asked about the prospect of Austria giving Sputnik V the approval (as some other European countries chose to do), EMA management board chair Christa Wirthumer-Hoche pointed to the fact there was not yet sufficient safety data about those who had already been given the vaccine. "We could have Sputnik V on the market in future, when we've examined the necessary data," she said, adding that the vaccine needed to match up to European criteria on quality control and efficacy.
Sources: en.wikipedia.org
Flubber, also commonly known as slime, is a non-Newtonian fluid, easily made from polyvinyl acetate–based glues (such as white "school" glue) and borax. It flows under low stresses but breaks under higher stresses and pressures. This combination of fluid-like and solid-like properties makes it a Maxwell fluid. Its behaviour can also be described as being viscoplastic or gelatinous.
== External links == Data related to Reptilia at Wikispecies Reptilia at Wikibooks "Reptiles" . Encyclopædia Britannica (11th ed.). 1911. "Reptile phylogeny". whozoo.org. Herpetology. Reptile images. 1833. {{cite book}}: |website= ignored (help) "Sri Lanka wildlife information database". wildreach.com. Archived from the original on December 27, 2010. "Biology of the reptilia". carlgans.org. — an online full text copy of a 22 volume 13,000 page summary of the state of reptile research.
=== Laboratory synthesis === Formaldehyde was discovered in 1859 by the Russian chemist Aleksandr Butlerov (1828–1886) when he tried to synthesize methanediol ("methylene glycol") from iodomethane and silver oxalate. In his paper, Butlerov called formaldehyde "dioxymethylen" (methylene dioxide) because his empirical formula for it was incorrect, as atomic weights were not precisely determined until the Karlsruhe Congress. August Wilhelm von Hofmann first identified the compound as an aldehyde. He announced its production by passing methanol vapor in air over hot platinum wire. With modifications, Hofmann's method remains the basis of the modern industrial route. Solution routes to formaldehyde also entail oxidation of methanol or iodomethane.
== External links == GeneReviews/NCBI/NIH/UW entry on Chondrodysplasia Punctata 2, X-Linked, Conradi-Hünermann Syndrome, Happle Syndrome EBP+protein,+human at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
In 1933 Hodgkin was awarded a research fellowship by Somerville College, and in 1934, she moved back to Oxford. She started teaching chemistry with her own lab equipment. The college appointed her its first fellow and tutor in chemistry in 1936, a post which she held until 1977. In the 1940s, one of her students was Margaret Roberts (later Margaret Thatcher) who, while Prime Minister, hung a portrait of Hodgkin in her office at Downing Street out of respect for her former teacher. Hodgkin was, however a life-long Labour Party supporter. In April 1953, together with Sydney Brenner, Jack Dunitz, Leslie Orgel, and Beryl M. Oughton, Hodgkin was one of the first people to travel from Oxford to Cambridge to see the model of the double helix structure of DNA, constructed by Francis Crick and James Watson, which was based on data and technique acquired by Maurice Wilkins and Rosalind Franklin. According to the late Dr Beryl Oughton (married name, Rimmer), they drove to Cambridge in two cars after Hodgkin announced that they were off to see the model of the structure of DNA. Hodgkin became a reader at Oxford in 1955 and she was given a fully modern laboratory the following year. In 1960, Hodgkin was appointed the Royal Society's Wolfson Research Professor, a position she held until 1970. This provided her salary, research expenses and research assistance to continue her work at the University of Oxford. She was a fellow of Wolfson College, Oxford, from 1977 to 1983.
Sources: en.wikipedia.org
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.
Freeze-dried material is kept frozen, often at minus 20 degrees Celsius, and protected from light and moisture. Dissolved peptide is refrigerated for short-term use. Repeated freeze-thaw cycles are avoided.
A certificate of analysis typically lists purity by HPLC, the confirmed mass, appearance, and sometimes water or counter-ion content. It documents results for a specific batch. Details vary by supplier.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.