reverse-phase HPLC raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
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.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
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.
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.
In 1953, changes in political leadership on both sides shifted the dynamic of the Cold War. Dwight D. Eisenhower was inaugurated president that January. During the last 18 months of the Truman administration, the American defense budget had quadrupled, and Eisenhower moved to reduce military spending by a third while continuing to fight the Cold War effectively. Joseph Stalin died in 1953. Nikita Khrushchev eventually won the ensuing power struggle by the mid-1950s. In 1956, he denounced Joseph Stalin and proceeded to ease controls over the party and society (de-Stalinization).
==== July 2021 settlement ==== Four major drug manufacturers and distributors, J&J, McKesson, Cardinal Health, and AmerisourceBergen, have agreed to a settlement announced by a group of state attorneys general in July 2021. The settlement, $26 billion (US), will be used on the prevention of opioid addiction and treatment programs. J&J will pay $5 billion (US) over the next five years; the remaining $21 billion (US) will be paid by the other firms. The settlement, when approved by a "significant" group of states and local governments, will settle more than 4,000 individual legal actions. All four of the manufacturing firms disputed all allegations in the lawsuits.
== Cause == Mutations in the UGT1A1 gene lead to Gilbert syndrome. The gene provides instructions for making the bilirubin uridine diphosphate glucuronosyltransferase (bilirubin-UGT) enzyme, which can be found in the liver cells and is responsible for preparing bilirubin for removal from the body. The bilirubin-UGT enzyme performs a chemical reaction called glucuronidation. Glucuronic acid is transferred to unconjugated bilirubin, which is a yellowish pigment made when your body breaks down old red blood cells, and then being converted to conjugated bilirubin during the reaction. Conjugated bilirubin passes from the liver into the intestines with bile. It's then excreted in stool. People with Gilbert syndrome have approximately 30% of normal bilirubin-UGT enzyme function, which contributes to a lower rate of glucuronidation of unconjugated bilirubin. This substance then accumulates in the body, causing mild hyperbilirubinemia.
Macromolecules cannot be directly processed by cells. Macromolecules must be broken into smaller units before they can be used in cell metabolism. Different classes of enzymes are used to digest these polymers. These digestive enzymes include proteases that digest proteins into amino acids, as well as glycoside hydrolases that digest polysaccharides into simple sugars known as monosaccharides. Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their guts, including the stomach, pancreas, and salivary glands. The amino acids or sugars released by these extracellular enzymes are then pumped into cells by active transport proteins.
Pearly penile papules are also termed papillae coronae glandis and hirsutoid papillomas. The condition of having such papules or papillae is called hirsuties papillaris coronae glandis or papillomatosis coronae glandis or papillomatosis coronae penis. These lesions develop in up to 30% of males during their puberty or, less commonly, early adulthood. They typically occur as numerous white-colored to skin-colored papules located circumferentially around the corona of the penis or, less commonly, the ventromedial aspect of the corona near the penis's frenulum. (Vestibular papillomatosis, also named hirsutoid vulvar papillomas, vulvar squamous papillomatosis, micropapillomatosis labialis, and squamous vestibular micropapilloma, is the female equivalent of pearly penile papules in men. It has not been formally termed an angiofibroma.)
Sources: en.wikipedia.org
The first body fossils of animals appear in the Ediacaran, represented by forms such as Charnia and Spriggina. It had long been doubted whether these fossils truly represented animals, but the discovery of the animal lipid cholesterol in fossils of Dickinsonia suggests that they are. Animals are thought to have originated under low-oxygen conditions, suggesting that they were capable of living entirely by anaerobic respiration, but as they became specialised for aerobic metabolism they became fully dependent on oxygen in their environments. Many animal phyla first appear in the fossil record during the Cambrian explosion, starting about 539 million years ago, in beds such as the Burgess Shale. Extant phyla in these rocks include molluscs, brachiopods, onychophorans, tardigrades, arthropods, echinoderms and hemichordates, along with numerous now-extinct forms such as the predatory Anomalocaris. The apparent suddenness of the event may however be an artefact of the fossil record, rather than showing that all these animals appeared simultaneously. That view is supported by the discovery of Auroralumina attenboroughii, the earliest known Ediacaran crown-group cnidarian (557–562 mya, some 20 million years before the Cambrian explosion) from Charnwood Forest, England. It is thought to be one of the earliest predators, catching small prey with its nematocysts as modern cnidarians do. Some palaeontologists have suggested that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago.
=== Legal controversy === The film was the subject of a copyright infringement lawsuit filed by White Wolf, Inc. and Nancy A. Collins, claiming the setting was too similar to the Vampire: The Masquerade and Werewolf: The Apocalypse games, both set in the World of Darkness setting, and to the Sonja Blue vampire novels. White Wolf filed 17 counts of copyright infringement, and claimed over 80 points of unique similarity between White Wolf's gaming systems and the film. These included some general plot points like vampires having superhuman speed or being able to disappear, and more specific similarities like a vampire/werewolf hybrid being referred to as an “Abomination”. White Wolf, Inc. also said the script was very similar to a story entitled The Love of Monsters (1994), which they published, written by Nancy A. Collins. In September 2003, a judge granted White Wolf an expedited hearing. The lawsuit ended in a confidential settlement.
The goal of the program was to boost the proficiency of Georgia's security forces in areas including border security, anti-terrorism, disaster response. Responsibility for training Georgian forces was eventually handed off to the U.S. Marine Corps in conjunction with the British Army. British and American teams worked as part of a joint effort to train each of the four infantry battalion staffs and their organic rifle companies. This training began with the individual soldier and continued through fire team, squad, platoon, company, and battalion level tactics as well as staff planning and organization. Upon completing training, each of the new Georgian infantry battalions began preparing for deployment rotations in support of the Global War on Terrorism. As part of the program Georgian troops were issued new uniforms, boots, weapons, and other articles of equipment. Although GTEP formally ended in April 2004, US military assistance to Georgia continued through the Georgia Sustainment and Stability Operations Program. Part of this program involved preparing Georgian units for operations in US-led Multinational Force Iraq. That program ended in September 2007.
== The economic crisis in Germany == Hitler's interest in Czechoslovakia was largely economic. Germany had the second-largest economy in the world, but German agriculture was not capable of feeding the population, and there was also a lack of many raw materials, which had to be imported. The Four-Year Plan that Hitler had launched in September 1936 to have the German economy ready for a "total war" by 1940 had seriously strained the German economy by 1937 as German government was forced to use up its foreign exchange reserves both to feed its own people and to import various raw materials to achieve the ambitious armament goals of the Four Year Plan. Though the Four Year Plan aimed at autarky, there were certain raw materials such as high-grade iron, oil, chrome, nickel, tungsten, and bauxite that Germany did not have and had to be imported. The need to import food and raw materials made Germany into Europe's second largest importer, being exceeded only by Great Britain. Moreover, hundreds of millions of Reichsmarks were spent on immense armament works such as the Reichswerke steel complex, an expensive program to develop synthetic fuel, as well as various costly chemical and metallurgical programs, all of which strained the German economy. The Great Depression was an era beset by trade wars and protectionism, which put further straining on the German export market and ability to generate foreign exchange. Moreover, the Four Year Plan with its aim of autarky led to Germany increasing its tariffs, which led other nations to do likewise in retaliation.
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.
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.