lyophilised powder raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-03-09. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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 |
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.
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.
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.
Policies outlined include banning non-compete clauses, curbing the ability of manufacturers to restrict the right to repair certain products, granting the Federal Trade Commission the ability to set guidelines on data collection, banning unfair competition practices in online marketplaces, and ordering the Food and Drug Administration to work with states and Native American tribes on procuring cheaper medicines from Canada. Illinois becomes the first state to teach history about Asian Americans in public schools. July 11–13 – The 2021 Major League Baseball First-Year Player Draft was held in Denver. Henry Davis was selected first overall by the Pittsburgh Pirates. July 12 Actor Drake Bell is sentenced to two years of probation for child endangerment. Ghislaine Maxwell, the long-time friend and partner of Jeffrey Epstein, appears in court in relation to allegations of sex trafficking. July 13 – The American League defeat the National League (5–2) in the 2021 MLB All-Star Game. July 16 – Michael Gargiulo (a.k.a. the Hollywood Ripper) is sentenced to death for two murders. July 17 – A shooting occurs outside of Nationals Park during a game between the San Diego Padres and the Washington Nationals during the sixth inning, causing the game to get postponed until Sunday. July 19 – Fox News host Sean Hannity urges viewers to take the threat of COVID-19 seriously, as well as urging viewers to receive the COVID-19 vaccine.
== Function == The protein encoded by this gene is an insulin like hormone produced mainly in gonadal tissues in males and females. Studies of the mouse counterpart suggest that this gene may be involved in the development of urogenital tract and female fertility. INSL-3 initiates meiotic progression in follicle-enclosed oocytes by mediating a reduction in intra-oocyte cAMP concentration by activating leucine-rich repeat-containing G protein-coupled receptor 8 (LGR8). It may also act as a hormone to regulate growth and differentiation of gubernaculum, and thus mediating intra-abdominal testicular descent. The mutations in this gene may lead to, but not a frequent cause of, cryptorchidism.
Curd is obtained by coagulating milk in a sequential process called curdling. It can be a final dairy product or the first stage in cheesemaking. The coagulation can be caused by adding rennet, a culture, or any edible acidic substance such as lemon juice or vinegar, and then allowing it to coagulate. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria) will also automatically produce curds, and sour milk cheeses are produced this way. Producing cheese curds is one of the first steps in cheesemaking; the curds are pressed and drained to varying amounts for different styles of cheese and different secondary agents (molds for blue cheeses, etc.) are introduced before the desired aging finishes the cheese. The remaining liquid, which contains only whey proteins, is the whey. In cow's milk, 90 percent of the proteins are caseins. Curds can be used in baking or may be consumed as a snack.
Sources: en.wikipedia.org
Ions with the same electron configuration decrease in size as their atomic number rises, due to increased attraction from the more positively charged nucleus: thus for example ionic radii decrease in the series Se2−, Br−, Rb+, Sr2+, Y3+, Zr4+, Nb5+, Mo6+, Tc7+. Ions of the same element get smaller as more electrons are removed, because the attraction from the nucleus begins to outweigh the repulsion between electrons that causes electron clouds to expand: thus for example ionic radii decrease in the series V2+, V3+, V4+, V5+.
In an exothermic reaction, the temperature in the sample cell increases upon addition of ligand. This causes the feedback power to the sample cell to be decreased (remember: a reference power is applied to the reference cell) in order to maintain an equal temperature between the two cells. In an endothermic reaction, the opposite occurs; the feedback circuit increases the power in order to maintain a constant temperature (isothermal operation). Observations are plotted as the power needed to maintain the reference and the sample cell at an identical temperature against time. As a result, the experimental raw data consists of a series of spikes of heat flow (power), with every spike corresponding to one ligand injection. These heat flow spikes/pulses are integrated with respect to time, giving the total heat exchanged per injection. By integrating each peak from the baseline, the total heat associated with each injection is obtained, including both reaction-specific and non-reaction-related contributions. The pattern of these heat effects as a function of the molar ratio [ligand]/[macromolecule] can then be analyzed to give the thermodynamic parameters of the interaction under study.
=== Archaea === Archaea have a single type of RNAP, responsible for the synthesis of all RNA. Archaeal RNAP is structurally and mechanistically similar to bacterial RNAP and eukaryotic nuclear RNAP I-V, and is especially closely structurally and mechanistically related to eukaryotic nuclear RNAP II. The history of the discovery of the archaeal RNA polymerase is quite recent. The first analysis of the RNAP of an archaeon was performed in 1971, when the RNAP from the extreme halophile Halobacterium cutirubrum was isolated and purified. Crystal structures of RNAPs from Sulfolobus solfataricus and Sulfolobus shibatae set the total number of identified archaeal subunits at thirteen. Archaea has the subunit corresponding to Eukaryotic Rpb1 split into two. There is no homolog to eukaryotic Rpb9 (POLR2I) in the S. shibatae complex, although TFS (TFIIS homolog) has been proposed as one based on similarity. There is an additional subunit dubbed Rpo13; together with Rpo5 it occupies a space filled by an insertion found in bacterial β′ subunits (1,377–1,420 in Taq). An earlier, lower-resolution study on S. solfataricus structure did not find Rpo13 and only assigned the space to Rpo5/Rpb5. Rpo3 is notable in that it's an iron–sulfur protein. RNAP I/III subunit AC40 found in some eukaryotes share similar sequences, but does not bind iron. This domain, in either case, serves a structural function. Archaeal RNAP subunit previously used an "RpoX" nomenclature where each subunit is assigned a letter in a way unrelated to any other systems.
== Management == Secondary Raynaud's is managed primarily by treating the underlying cause, and as with primary Raynaud's, by avoiding triggers, such as cold, emotional and environmental stress, vibrations, and repetitive motions, and avoiding smoking (including passive smoking) and sympathomimetic drugs.
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.