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.
Updated 2026-06-23. Numbers and descriptions here follow the published literature rather than marketing material.
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 |
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.
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.
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.
=== Languages === The official language of Schleswig-Holstein is German. In addition, Low German, Danish and North Frisian are recognized minority languages. Historically, Low German (in Holstein and Southern Schleswig), Danish (in Schleswig), and North Frisian (in Western Schleswig) were widely spoken in Schleswig-Holstein. During the language change in the 19th century some Danish and North Frisian dialects in Southern Schleswig were replaced by Standard German. Low German is still used in many parts of the state. Missingsch, a Low German dialect with heavy High German (Standard German) influence, is commonly spoken informally throughout the state, while a mixed language Petuh (mixture of High German and Danish) is used in and around Flensburg. Danish is used by the Danish minority in Southern Schleswig, and North Frisian is spoken by the North Frisians of the North Sea Coast and the Northern Frisian Islands in Southern Schleswig. The North Frisian dialect called Heligolandic (Halunder) is spoken on the island of Heligoland. As is the case throughout Germany, High German, introduced in the 16th century, has come to steadily replace local dialects for official purposes, and is today the predominant language of media, law, and legislature. It is spoken by virtually all inhabitants in formal situations. Since the end of World War II and the widespread adoption of TV, radio, and other mass media, it has gradually come to supplant local dialects in urban areas as well.
Scott Boatwright, Chief Executive Officer and Board member Adam Rymer, Chief Financial Officer Curt Garner, President, Chief Strategy and Technology Officer Ilene Eskenazi, Chief Legal and Human Resources Officer Jason Kidd, Chief Operating Officer Laurie Schalow, Chief Corporate Affairs Officer Kerry Bridges, Chief Food Safety Officer
Births from January–October 2016 = 62,761 Births from January–October 2017 = 61,314 Deaths from January–October 2016 = 75,733 Deaths from January–October 2017 = 75,804 Natural growth from January–October 2016 = -12,972 Natural growth from January–October 2017 = -14,490
Ellen McLain (born 1952 or 1953) is an American voice actress. She is best known for providing the voice of GLaDOS, the primary antagonist of the Portal video game series, the Combine Overwatch AI in Half-Life 2, and the Administrator, the announcer in Team Fortress 2. Her voice roles also include the Jaeger A.I. in Pacific Rim and The Witch in Left 4 Dead 2.
Sources: en.wikipedia.org
=== PAM === One of the first amino acid substitution matrices, the PAM (Point Accepted Mutation) matrix was developed by Margaret Dayhoff in the 1970s. This matrix is calculated by observing the differences in closely related proteins. Because the use of very closely related homologs, the observed mutations are not expected to significantly change the common functions of the proteins. Thus the observed substitutions (by point mutations) are considered to be accepted by natural selection. One PAM unit is defined as 1% of the amino acid positions that have been changed. To create a PAM1 substitution matrix, a group of very closely related sequences with mutation frequencies corresponding to one PAM unit is chosen. Based on collected mutational data from this group of sequences, a substitution matrix can be derived. This PAM1 matrix estimates what rate of substitution would be expected if 1% of the amino acids had changed. The PAM1 matrix is used as the basis for calculating other matrices by assuming that repeated mutations would follow the same pattern as those in the PAM1 matrix, and multiple substitutions can occur at the same site. With this assumption, the PAM2 matrix can estimated by squaring the probabilities. Using this logic, Dayhoff derived matrices as high as PAM250. Usually the PAM 30 and the PAM70 are used.
== Signs and symptoms == Because of the enormous number of these diseases and the numerous systems negatively impacted, nearly every "presenting complaint" to a healthcare provider may have a congenital metabolic disease as a possible cause, especially in childhood and adolescence. The following are examples of potential manifestations affecting each of the major organ systems.
Structurally, relaxin is a heterodimer of two peptide chains of 24 and 29 amino acids linked by three disulfide bridges, and it appears related to insulin. Relaxin is produced from its prohormone, "prorelaxin", by post-translational proteolytic cleavage of its signal peptide and C domain peptide.
Next to occupy the Oval Office, Reagan protégé and former VP George H. W. Bush (1989–93) maintained the hard line drawn by his predecessor and former boss. In his first prime time address to the nation, Bush held up a plastic bag of crack "seized a few days ago in a park across the street from the White House" (it was later revealed that DEA agents had to lure the seller to Lafayette Park to make the requested arrest). The administration increased narcotics regulation in the first National Drug Control Strategy, issued by the Office of National Drug Control Policy (ONDCP) in 1989. The director of ONDCP became commonly known as the US drug czar. In the National Defense Authorization Act for 1990–91, Congress included Section 1208 – the 1208 Program, expanded into the 1033 Program in 1996 – authorizing the Department of Defense to transfer surplus military equipment that the DoD determined to be "suitable for use in counter-drug activities", to local law enforcement agencies. As president, Bill Clinton (1993–2001), seeking to reposition the Democratic Party as tough on crime, dramatically raised the stakes for drug felonies with his signing of the Violent Crime Control and Law Enforcement Act of 1994. The act introduced the federal "three-strikes" provision that mandated life imprisonment for violent offenders with two prior convictions for violent crimes or drugs, and provided billions of dollars in funding for states to expand their prison systems and increase law enforcement.
Targeted mass spectrometry is a mass spectrometry technique that uses multiple stages of tandem mass spectrometry (MSn with n=2 or 3) for ions of specific mass (m/z), at specific time. The values of the m/z and time are defined in an inclusion list which is derived from a previous analysis.
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.