This is a working overview of proteolysis, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-26. 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.
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.
| 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 |
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.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
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.
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.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
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.
=== In industry === Acids are fundamental reagents in treating almost all processes in modern industry. Sulfuric acid, a diprotic acid, is the most widely used acid in industry, and is also the most-produced industrial chemical in the world. It is mainly used in producing fertilizer, detergent, batteries and dyes, as well as used in processing many products such like removing impurities. According to the statistics data in 2011, the annual production of sulfuric acid was around 200 million tonnes in the world. For example, phosphate minerals react with sulfuric acid to produce phosphoric acid for the production of phosphate fertilizers, and zinc is produced by dissolving zinc oxide into sulfuric acid, purifying the solution and electrowinning. In the chemical industry, acids react in neutralization reactions to produce salts. For example, nitric acid reacts with ammonia to produce ammonium nitrate, a fertilizer. Additionally, carboxylic acids can be esterified with alcohols, to produce esters. Acids are often used to remove rust and other corrosion from metals in a process known as pickling. They may be used as an electrolyte in a wet cell battery, such as sulfuric acid in a car battery.
== History == In 1958, James (Jim) Logan Waters founded Waters Associates in an office in the basement of a police station in Framingham, Massachusetts. Early products included a boiler feedwater flame photometer, a balloon hydrometer, a nerve gas detector, a lab refractometer and process control refractometers. Having asked Waters to design a refractometer in 1961, Dow Chemical had designed a method of analyzing polymers using gel columns. Waters negotiated an exclusive license to the patent, paying $10,000 plus a 10% royalty. In 1962, Hardie Sheppard provided the company with $150,000, its first external financing raise. In 1963, Waters’ produced its first five gel permeation chromatography instruments, selling three to Dow Chemical, one to BFGoodrich, and one to Esso. Dow Chemical then invested $400,000 in Waters. In 1965, interest surged after Waters sponsored a symposium where scientists presented the results of using Waters equipment. In 1966, Dow converted its royalty receivable into equity in Waters. In 1967, the company introduced the ALC 100, the first Waters LC system. It was a benchtop system equipped with a Milton Roy pump, syringe injection, and two detectors: a Waters differential refractometer and a UV detector from Laboratory Data Control. In 1969, Dimitri D’Arbeloff, then president of Millipore Corporation, joined the board of directors; Millipore's venture capital subsidiary made a $600,000 equity investment in Waters and provided the company with marketing expertise. By 1972, Dow Chemical had invested $700,000 in the company and owned a 20% stake.
Canada is divided into 15 terrestrial and five marine ecozones. These ecozones encompass over 80,000 classified species of Canadian wildlife, with an equal number yet to be formally recognized or discovered. Although Canada has a low percentage of endemic species compared to other countries, due to human activities, invasive species, and environmental issues in the country, there are currently more than 800 species at risk of being lost. About 65 percent of Canada's resident species are considered "Secure". Over half of Canada's landscape is intact and relatively free of human development. The boreal forest of Canada is considered to be the largest intact forest on Earth, with approximately 3,000,000 square kilometres (1,200,000 sq mi) undisturbed by roads, cities or industry. Since the end of the last glacial period, Canada has consisted of eight distinct forest regions. Approximately 12.1 percent of the nation's landmass and freshwater are conservation areas, including 11.4 percent designated as protected areas. Approximately 13.8 percent of its territorial waters are conserved, including 8.9 percent designated as protected areas. Canada's first National Park, Banff National Park was established in 1885. Canada's oldest provincial park, Algonquin Provincial Park was established in 1893. Established in 2015, Lake Superior National Marine Conservation Area is the world's largest freshwater protected area. Canada's largest national wildlife region, established in 2018, is the Scott Islands Marine National Wildlife Area.
Common recreational drugs include caffeine, commonly found in coffee, tea, soft drinks, and chocolate; alcohol, commonly found in beer, wine, cocktails, and distilled spirits; nicotine, commonly found in tobacco, tobacco-based products, and electronic cigarettes; cannabis and hashish (with legality of possession varying inter/intra-nationally); and the controlled substances listed as controlled drugs in the Single Convention on Narcotic Drugs (1961) and the Convention on Psychotropic Substances (1971) of the United Nations (UN). Since the early 2000s, the European Union (EU) has developed several comprehensive and multidisciplinary strategies as part of its drug policy in order to prevent the diffusion of recreational drug use and abuse among the European population and raise public awareness on the adverse effects of drugs among all member states of the European Union, as well as conjoined efforts with European law enforcement agencies, such as Europol and EMCDDA, in order to counter organized crime and illegal drug trade in Europe.
=== Heterogeneous catalysis === Operando spectroscopy is widely applicable to heterogeneous catalysis, which is largely used in industrial chemistry. An example of operando methodology to monitor heterogeneous catalysis is the dehydrogenation of propane with molybdenum catalysts commonly used in industrial petroleum. Mo/SiO2 and Mo/Al2O2 were studied with an operando setup involving EPR/UV-Vis, NMR/UV-Vis, and Raman. The study examined the solid molybdenum catalyst in real time. It was determined that the molybdenum catalyst exhibited propane dehydrogenation activity, but deactivated over time. The spectroscopic data showed that the most likely catalytic active state was Mo4+ in the production of propene. The deactivation of the catalyst was determined to be the result of coke formation and the irreversible formation of MoO3 crystals, which were difficult to reduce back to Mo4+. The dehydrogenation of propane can also be achieved with chromium catalysts, through the reduction of Cr6+ to Cr3+. Propylene is one of the most important organic starting materials is used globally, particularly in the synthesis of various plastics. Therefore, the development of effective catalysts to produce propylene is of great interest. Operando spectroscopy is of great value to the further research and development of such catalysts.
Sources: en.wikipedia.org
=== Other small molecule VEGFR inhibitors === Conjugated 3-(indolyl)- and 3-(azaindolyl)-4-arylmaleimide compounds can induce apoptosis in cancer cells and therefore may have use in cancer therapy, including colorectal and gastric adenocarcinoma. Oxetane 3,3-dicarboxamide compounds are possible inhibitors of tumor angiogenesis and metastasis, and may also be effective against viral infections. A 1,6-naphyridine-4-ketone fused heterocyclic derivative inhibits various kinases and the activity of tumor cells. The antifungal drug itraconazole may be and inhibitor for VEGFR-2 and could be used in treatments that VEGFR-2 plays a role. 3-phenyl-5-ureidoisothiazole-4-carboximide and 3-amino-5-phenylisothiazole derivatives inhibit, modulate and regulate tyrosine kinase signal and can be used for treatment of disorders that are caused by unregulated tyrosine kinase signal transduction, including cell growth, metabolic and blood vessel proliferative disorders. Thioether derivatives can be used to treat all forms of cancer and target multi target protein kinase inhibitors.
== Bound-state β− decay == A very small minority of free neutron decays (about four per million) are "two-body decays": the proton, electron and antineutrino are produced, but the electron fails to gain the 13.6 eV energy necessary to escape the proton, and therefore simply remains bound to it, as a neutral hydrogen atom. In this type of beta decay, in essence all of the neutron decay energy is carried off by the antineutrino. For fully ionized atoms (bare nuclei), it is possible in likewise manner for electrons to fail to escape the atom, and to be emitted from the nucleus into low-lying atomic bound states (orbitals). This can in theory occur for neutral atoms, as a new bound state is always opened by the decay, but rarely is appreciable. Bound-state β− decays were predicted by Daudel, Jean, and Lecoin in 1947, and the phenomenon in fully ionized atoms was first observed for 163Dy66+ in 1992 by Jung et al. of the Darmstadt Heavy-Ion Research Center. Though neutral 163Dy is stable, fully ionized 163Dy66+ undergoes β− decay into the K and L shells with a half-life of 47 days. The resulting nucleus – 163Ho66+ – is stable only in this almost fully ionized state and will decay via electron capture back into 163Dy in the neutral state. Likewise, while being stable in the neutral state, the fully ionized 205Tl81+ undergoes bound-state β− decay to 205Pb81+ with a half-life of 291+33−27 days. The half-lives of neutral 163Ho and 205Pb are respectively 4570 years and 1.70×107 years. The Q-value of bound-state beta decay of a highly-ionized atom,
The brand became a well-established franchise in the Philippines, where it began in 1975 under the ownership of the country's largest food conglomerate, San Miguel Corporation, primarily promoting their San Miguel draft beer. Beginning with a restaurant located on Makati Avenue in Makati, the restaurant expanded rapidly in Metro Manila, with most of its outlets offering live music. San Miguel had difficulty maintaining the consistency of the branches, and ultimately sold the franchise in 1987 to International Family Food Services, Inc. (IFFSI), a group led by the family of sports executive Leo Prieto. In 1997, it had evolved into mostly a fast-food franchise. The brand was reengineered as a family-oriented casual dining brand in 2003. In 2004, Shakey's partnered with Sports Vision for the launch of the Shakey's V-League, one of the pioneering volleyball leagues in the country. The Shakey's Super League was formally launched on August 16, 2022, at the Shakey's Pizza Aseana City outlet in Parañaque. This marks the return of Shakey's Pizza in Philippine volleyball since they served as the title sponsor for the Shakey's V-League (now Premier Volleyball League) from 2004 to 2017. As of early 2015, there were 153 Shakey's outlets in the Philippines, more than double the number remaining in the United States. In March 2016, the Century Pacific Group and the Singapore-based GIC Private Limited acquired the majority shares of IFFSI from the Prieto family, which will retain a minority interest in the company.
The siege of Coimbra in 1064 or the definitive conquest of Coimbra by Christian forces took place in 1064, from January to July; it ended on 9 July 1064, a Friday, when the king, Ferdinand I of Leon, captured the city from the Muslims. The city of Coimbra had previously been taken from the Christians by Almanzor (or al-Manṣūr) in 987. When the Fitna of al-Andalus broke out and the Umayyad Caliphate of Cordova fragmented into numerous taifa states, Dom Sesnando Davides, lord of Tentúgal proposed the conquest of the city to Ferdinand of Leon. Ferdinand thus began preparations for the campaign in December 1063, after receiving the remains of Saint Isidore of Seville in León. Before he moved against Coimbra however, he made a pilgrimage to Santiago de Compostela. Having prayed there before the tomb of the apostle, St. James of Compostela, for three days and made several donations to the church there, he departed accompanied by his wife Dona Sancha, his sons, the Bishop Crescónio of Santiago, Bishop Vistruário of Lugo, Bishop Suário of Mondonhedo, Bishop Sesnando of Portugal, the abbot Ariano of Cela Nova, abbot Pedro of Guimarães, and a large number of nobles. They advanced through a coastal road that linked Santiago de Compostela to Iria Flavia to Braga, Porto and Coimbra. They arrived before the walls of the city on 20 January 1064. The Muslim garrison fiercely resisted the Christian attacks. The supply situation of the Christians was not favourable and Ferdinand even pondered lifting the siege.
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.
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.