If you have been reading about reverse-phase HPLC 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 2026-03-06. 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. 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.
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.
| 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 |
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.
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.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
Oskar Stross, Austrian Consul General Mervyn Whitfield, Political Branch, Public Security, Alexandria, 1917 General Sir Reginald Wingate, 1915 Judge Youssef Zulficar Pasha (Grand Cordon) Oswald Longstaff Prowde, English civil engineer Lt Colonel William John Ainsworth, CBE DSO Durham Light Infantry (3rd Class 1919),
== Bronchodilators == Arformoterol Bitolterol Epinephrine Fenoterol Formoterol Ipratropium Isoetharine Isoproterenol Levalbuterol Metaproterenol Pirbuterol Procaterol Racepinephrine (racemic epinephrine) Salbutamol Salmeterol Terbutaline Tiotropium
== Nomenclature == Alternative names provided by the EC include 3CLpro, 3C-like protease, coronavirus 3C-like protease, Mpro, SARS 3C-like protease, SARS coronavirus 3CL protease, SARS coronavirus main peptidase, SARS coronavirus main protease, SARS-CoV 3CLpro enzyme, SARS-CoV main protease, SARS-CoV Mpro and severe acute respiratory syndrome coronavirus main protease.
No one shall be held in slavery or servitude; slavery and the slave trade shall be prohibited in all their forms. In 2014, for the first time in history, major leaders of many religions, Buddhist, Hindu, Christian, Jewish, and Muslim met to sign a shared commitment against modern-day slavery; the declaration they signed calls for the elimination of slavery and human trafficking by 2020. The signatories were: Pope Francis, Mātā Amṛtānandamayī, Bhikkhuni Thich Nu Chân Không (representing Zen Master Thích Nhất Hạnh), Datuk K Sri Dhammaratana, Chief High Priest of Malaysia, Rabbi Abraham Skorka, Rabbi David Rosen, Abbas Abdalla Abbas Soliman, Undersecretary of State of Al Azhar Alsharif (representing Mohamed Ahmed El-Tayeb, Grand Imam of Al-Azhar), Grand Ayatollah Mohammad Taqi al-Modarresi, Sheikh Naziyah Razzaq Jaafar, Special advisor of Grand Ayatollah (representing Grand Ayatollah Sheikh Basheer Hussain al Najafi), Sheikh Omar Abboud, Justin Welby, Archbishop of Canterbury, and Metropolitan Emmanuel of France (representing Ecumenical Patriarch Bartholomew.) Groups such as the American Anti-Slavery Group, Anti-Slavery International, Free the Slaves, the Anti-Slavery Society, and the Norwegian Anti-Slavery Society continue to campaign to eliminate slavery. UNESCO has been working to break the silence surrounding the memory of slavery since 1994, through The Slave Route Project.
Sources: en.wikipedia.org
===== The maxillary division innervation ===== Maxillary nerve – conveys sensation to the upper jaw and the face. Infraorbital nerve – conveys sensation to the area from below the eye socket to the external nares (nostrils). Zygomatic nerve – through the zygomatic bone and the zygomatic arch, conveys sensation to the cheekbone areas. Superior posterior dental nerve – sensation in the teeth and the gums. Superior anterior dental nerve – mediates the sneeze reflex. Sphenopalatine nerve – divides into the lateral branch and the septal branch, and conveys sensation from the rear and the central regions of the nasal cavity.
In 1985, the chain struggled in Singapore, losing its relevance to newer, larger chains and its dominance in the fried chicken area to KFC. The chain was about to amp up its operations in the Asian region, with a possible launch in Hong Kong as well as three new restaurants in Thailand. On April 21, 1985, its first restaurant opened in Indonesia, in the Melawai area of South Jakarta, its capital. Currently, Indonesia is the chain's largest international market, which as of February 2023 claimed 243 restaurants in 30 cities. A restaurant in Ximending, Taiwan opened on February 22, 1986. Its two units in Kuwait were closed in 1988 owing to security concerns. It was in Kuwait, during a US-Malaysia trip, that Kevin Bazner was held hostage in August 1990 when the plane he was on board was set for refueling; he was released in December. Negotiations were held with Sonic Drive-In for a potential buying of the chain, but the plans fell in October 1986 due to a decline in franchises. Expansion plans were formulated in August 1987 with the opening of twenty new restaurants in a one-year period. On March 6, 1988, the first conventional A&W outlet opened in the Philippines at Fiesta Carnival in Cubao, followed by a second at Gift Gate Center on November 26. The second restaurant's reputation was damaged by a fire of unknown origin that broke out in May 1990. Nonetheless, the chain expanded with new outlets and products by the end of 1990. The Philippine chain was the first A&W to introduce chicken nuggets, a product that even the American operations wanted from there.
== Supercritical fluid methods == Supercritical fluid precipitation techniques produce micronized particles by inducing supersaturation in a supercritical-fluid solution, leading to controlled precipitation of individual particles. The three most widely applied variants are the RESS process (Rapid Expansion of Supercritical Solutions), the SAS method (Supercritical Anti-Solvent) and the PGSS method (Particles from Gas Saturated Solutions), each described in the subsections below. Supercritical carbon dioxide (scCO2) is the most commonly used medium because it is chemically inert, has easily accessible critical-point parameters, and can be used to obtain either crystalline or amorphous micronized forms. Particle size and morphology are controlled both by macroscopic parameters such as nozzle geometry and flow rate, and by molecular-level effects of pressure, temperature, solute concentration and antisolvent-to-solvent ratio. These conditions influence nucleation kinetics and can drive polymorphic or amorphous transformations during particle formation. Compared to mechanical comminution, supercritical-fluid methods generally yield narrower particle-size distributions and more consistent particle morphology, and the relatively mild operating pressures and temperatures permit processing of thermolabile compounds. The use of CO2 as solvent also avoids the flammable and toxic organic solvents required by some conventional precipitation methods.
==== 2020 ==== Scientists report, using public biological data on 1.75 m people with known lifespans overall, to have identified 10 genomic loci which appear to intrinsically influence healthspan, lifespan, and longevity – of which half have not been reported previously at genome-wide significance and most being associated with cardiovascular disease – as well as haem metabolism as a promising candidate for further research within the field. Scientists report that after mice exercise their livers secrete the protein GPLD1, which is also elevated in elderly humans who exercise regularly, that this is associated with improved cognitive function in aged mice and that increasing the amount of GPLD1 produced by the mouse liver in old mice could yield many benefits of regular exercise for their brains – such as increased BDNF-levels, neurogenesis, and improved cognitive functioning in tests. Scientists report that yeast cells of the same genetic material and within the same environment age in two distinct ways, describe a biomolecular mechanism that can determine which process dominates during aging and genetically engineer a novel aging route with substantially extended lifespan. Reprogramming progress Scientists show that expression of nuclear reprogramming factors can lead to rapid and broad amelioration of cellular aging. A study shows that reprogramming induced with the OSK-genes can restore youthful epigenetic patterns as well as revert age-related vision loss.
GC Vitamin D binding protein, also referred to as Vitamin D binding protein (DBP), is a protein that is encoded by the GC gene in Homo sapiens (modern humans). DBP is genetically the oldest member of the albuminoid family and appeared early in the evolution of vertebrates.
Sources: en.wikipedia.org
Zverev maintained his top 5 ranking throughout the year. However, he still did not deliver any high-calibre results at the major tournaments. He was upset at the Australian Open by reigning Next Gen Finals champion and No. 59 Chung Hyeon in five sets in the third round. Zverev stated that issues at majors were "definitely not physical" when asked if his problems were physical or mental, and also attribute this lack of success to the extra pressure he was putting on himself at these events. Zverev did not reach his first final of the year until early April at the Miami Masters. Despite taking the first set of the final, he finished runner-up to American John Isner, who had never previously won a Masters title. Zverev continued his Masters success into the clay-court season, reaching the semifinals at the Monte Carlo Masters, winning his third career Masters title at the Madrid Open, and making the final at the Rome Masters. In Madrid, he defeated Dominic Thiem in the final to become the only active player outside of the Big Four to have won three Masters titles. He came close to winning back-to-back Masters events, going up a break in the third set against Nadal at the Italian Open. However, Nadal was able to recover and win the final five games of the match after a rain delay. Zverev had also defended his title at the Bavarian International Tennis Championships in his only other French Open tune-up to help build up a 13 match win streak that lasted until the Italian Open final.
Until January 1918, the Free Cossacks of Ukraine were subordinate to the Ukrainian General Secretariat of Internal Affairs. With the beginning of the Ukrainian-Soviet War, their units were incorporated into the regular army. However, after a number of battles against the Bolsheviks, Free Cossacks were disarmed in compliance with orders of the German command, whose troops had occupied Ukraine in March–April 1918 after the Treaty of Brest-Litovsk. On 29 April 1918 Pavlo Skoropadskyi, the earlier leader of Free Cossacks, was proclaimed Hetman of Ukraine at a congress of the conservative All-Ukrainian Union of Landowners. This coup was backed by generals of German and Austrian armies which were occupying Ukraine at that time. The previously democratic Ukrainian People's Republic was replaced with the Hetmanate, the Central Rada and the Council of Ministers of the Ukrainian People's Republic were abolished, with all their powers, as well as command over the military, being transferred to Skoropadskyi, and private land ownership was reinstated. Local administration was entrusted to commissioners personally appointed by the hetman. To achieve legitimacy among the Ukrainian population, the Skoropadskyi styled his regime as a continuation of Ukrainian Cossack traditions of the 17-18th centuries. The hetman's government included representatives of old Cossack nobility (starshyna), most prominently Fedir Lyzohub (head of the Conucil of Ministers) and Dmytro Doroshenko (Minister of Foreign Affairs).
Selenium is a chemical element; it has symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust. Selenium (from σελήνη 'moon') was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot. Although trace amounts of selenium are necessary for cellular function in many animals, including humans, both elemental selenium and (especially) selenium salts are toxic in even small doses, causing selenosis. Symptoms include (in decreasing order of frequency): diarrhea, fatigue, hair loss, joint pain, nail brittleness or discoloration, nausea, headache, tingling, vomiting, and fever.
International Proteolysis Society Protease cut sites graphical interface Merops - the peptidase database Archived 2006-11-14 at the Wayback Machine The Proteolysis Map TopFIND protease database covering cut sites, substrates and protein termini List of proteases and their specificities (see also [1] Archived 2011-04-30 at the Wayback Machine) Proteases at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
=== Cystic fibrosis === Cystic fibrosis affects pancreatic ducts as well as many other secretory epithelia. Cystic fibrosis transmembrane conductance regulator (CFTR) is the mutated gene and is essential to chloride and bicarbonate secretion. The abnormal amount of anion secretion causes a reduced amount of ductal water flow. Because of this, the duct's protein concentration increases and causes the duct lumina to get plugged. The onset of cystic fibrosis affects the pancreas more than any other organ (even before birth).
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.
Purity is usually reported as an HPLC area percentage, most often measured at 214 nm. Identity is confirmed separately by mass spectrometry. A certificate of analysis should state both the method and the observed value.