This is a working overview of Reversed-phase HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-02-02 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
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.
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.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
=== Basement membrane zone === In the skin the basement membrane that separates, and connects the epidermis and the underlying dermis is part of a complex and specialized structure called the basement membrane zone (BMZ). The BMZ has four distinct layers – the basal cell layer, the lamina lucida, the lamina densa, and the sublaminal densa, and has many functions. Tiny microfilaments called tonofilaments cross the basal cell layer, and extend to the epidermal part of the hemidesmosome. Laminins and other adherence proteins are located in the lamina lucida. The lamina densa is mostly composed of a type IV collagen scaffold. Anchoring fibrils and microfilaments extend and blend with the elastic fibrillary system of the dermis. The components of the BMZ form a complex, functional network that extends from the basal epidermal keratinocytes and their hemidesmosomes, and include anchoring fibrils from the lamina densa, into the extracellular matrix (ECM) of the dermis. In the ECM the anchoring fibrils appear as cross-striated fibrous masses. There are also focal adhesion complexes on the outer cell membrane that bind the cytoskeleton to cell-matrix adhesions.
==== FDA assessment ==== In April 2019, the FDA issued a statement declaring that kratom was not approved for any medical use, was potentially unsafe in commercial products available in the United States, and remained on an import alert where imported supplies would be confiscated. On April 4, 2018, the FDA issued the first mandatory recall in its history over concerns of salmonella contamination of several kratom-containing products. Samples of the products, manufactured by Triangle Pharmanaturals, and marketed under the brand name 'Raw Form Organics', tested positive for contamination and the manufacturer did not comply with federal requests for voluntary recall. FDA Commissioner Gottlieb stated that the recall was "...based on the imminent health risk posed by the contamination of this product with salmonella" and not related to other regulatory concerns. Consumers were advised to immediately discard any such products to prevent serious health risks. In February 2018, the commissioner of the FDA, Scott Gottlieb, released a statement describing further opioid-like properties of kratom and stating that it should not be used for any medical treatment or recreational use. Also in 2018, the FDA supervised the voluntary destruction of kratom dietary supplements by a nationwide distributor in Missouri, and encouraged all companies involved in kratom commerce to remove their products from the market.
=== Parts and cleavages === Transcript variant 1 of PIDD1 mRNA in humans, produces a full-length PIDD1 protein consisting of 910 amino acids, with a molecular weight of about 100 kDa. This protein can be broken down into three parts: a 48 kDa N-terminal fragment called PIDD-N, and two C-terminal fragments, PIDD-C (51 kDa) and PIDD-CC (37 kDa). These cleavages occur at positions S446 and S588 through an autoproteolytic process that resembles proteins like inteins or nucleoporin Nup98 undergo self-cleavage. These proteins contain a conserved HSF tripeptide framework that enables a hydrophilic attack of the hydroxyl-group within the serine residue on the preceding peptide bond, converting it into an ester bond that is susceptible to cleavage by an additional nucleophile. The cleavage of full-length PIDD1 (FL-PIDD1) into PIDD-C or PIDD-CC seems to occur constitutively, meaning it happens regularly, which makes FL-PIDD1 levels remain low even when p53 is activated. However, the observation that PIDD-C accumulates before PIDD-CC in response to DNA damage supports the idea that PIDD-C is the primary form generated from FL-PIDD1.
== Museum exhibition == Deutsches Museum opened an exhibition on 3 November 1995 which featured Cremer's work in its branch in Bonn, explaining to the public how she built the first gas chromatograph with Fritz Prior in the 1940s.
=== Support team === Mission Director and Flight Director - Red Team: Christopher C. Kraft, Jr. Flight Director - Blue Team: John D. Hodge Flight Director - White Team: Eugene F. Kranz CAPCOMs: Gus Grissom, Roger B. Chaffee, and Eugene Cernan Worldwide support and recovery team: 10,249 U.S. Department of Defense personnel, 134 aircraft, and 26 ships.
Sources: en.wikipedia.org
== History == In 1921, Joslin reported the association of diabetes with hypertension and hyperuricaemia. In 1923, Kylin expanded on this triad. In 1947, Vague observed that upper-body obesity predisposed to diabetes, atherosclerosis, gout and calculi. The term metabolic syndrome began appearing in the late 1950s. In 1967, Avogaro, Crepaldi and coworkers described moderately obese people with diabetes, hypercholesterolemia, and marked hypertriglyceridemia that improved on hypocaloric, low-carbohydrate diets. In 1977, Hans Haller used the term for associations of obesity, diabetes mellitus, hyperlipoproteinemia, hyperuricemia, and hepatic steatosis. The same year, Singer used it for associations of obesity, gout, diabetes, and hypertension with hyperlipoproteinemia. In 1977–1978, Gerald B. Phillips proposed a "constellation of abnormalities" (glucose intolerance, hyperinsulinemia, hypercholesterolemia, hypertriglyceridemia, hypertension) and hypothesised sex hormones as a linking factor. The first comprehensive definition of the metabolic syndrome was given in 1981 by the German researchers Markolf Hanefeld and Wolfgang Leonhardt, Dresden, who defined it as a cluster of obesity, hyper- and dyslipoproteinemia, type 2 diabetes, gout, and hypertension, associated with an increased incidence of atherosclerotic vascular disease, fatty liver disease, and gallstones. In 1988, Gerald M. Reaven's Banting lecture proposed insulin resistance as the underlying factor and coined syndrome X.
In 1943, the Nobel committee received a single nomination for the Nobel Prize in Physiology or Medicine for Fleming and Florey from the British biochemist Rudolph Peters. The secretary of the Nobel committee, Göran Liljestrand, made an assessment of Fleming and Florey in the same year, but little was known about penicillin in Sweden at the time, and he concluded that more information was required. The following year, there was one nomination for Fleming alone and one for Fleming, Florey and Chain. Liljestrand and Nanna Svartz, the professor of medicine at the Karolinska Institute, considered their work, and while both judged Fleming and Florey equally worthy of a Nobel Prize, the Nobel committee was divided, and decided to award the prize that year instead to Joseph Erlanger and Herbert S. Gasser "for their discoveries relating to the highly differentiated functions of single nerve fibres". There were a large number of nominations for Florey and Fleming or both in 1945, and one for Chain, from Liljestrand, who nominated all three. Liljestrand noted that thirteen of the first sixteen nominations that came in mentioned Fleming, but only three mentioned him alone. This time evaluations were made by Liljestrand, Sven Hellerström and Anders Kristenson, who endorsed all three. There were rumours that the committee would award the prize to Fleming alone, or half to Fleming and one-quarter each to Florey and Chain. Fulton and Dale lobbied for the award to be given to Florey.
2800 Polar Way is a cold storage facility located in Richland, Washington, United States. It is both the largest refrigerated warehouse and the largest automated freezer on Earth. Holliday Fenoglio Fowler (HFF) financed the build-to-suit refrigerated warehouse for tenant Preferred Freezer Services. The project broke ground on May 12, 2014, and opened in late July 2015. In 2016, HHF sold the property to Lexington Realty Trust, an S&P 600 REIT company. In 2019, Lineage Logistics acquired Preferred Freezer, and continues to operate the facility.
The crystal structure of catechol oxidase purified from Ipomoea batatas has been resolved in its active form in both the oxidized Cu(II)-Cu(II) state and the reduced Cu(I)-Cu(I) state. It is a globular, single domain monomeric enzyme that is approximately 55 by 45 by 45 Å in size and ellipsoid in shape. A four α-helix bundle comprises the enzyme core, which girds the active site containing the dicopper center. The nitrogens on the imidazole side chains of His88, His109, and His118 coordinate with the first catalytic copper while the nitrogens on the imidazole side chains on His240, His244 and His274 coordinate with the second catalytic copper ion. In the oxidized Cu(II)-Cu(II) state, each copper ion possesses a four coordinate trigonal pyramidal geometry, with the three histidine residues and a bridging hydroxide molecule forming the four ligands on each copper ion. Comparing the reduced (Cu(I)-Cu(I)) state with the native (Cu(II)-Cu(II)) state of the enzyme, the key difference is the distance between the two copper centers. In the oxidized Cu(II)-Cu(II) state, the Cu-Cu distance is 3.3 Å while in the reduced Cu(I)-Cu(I) state, the distance increases to 4.4 Å. While the active site of both tyrosinase and catechol oxidase contain the di-copper center, variations in each enzyme’s respective structure result in differing activity. In catechol oxidase, a phenylalanine side-chain (Phe261) is above one of the copper centers and prevents the substrate from coordinating with both copper ions in the active site.
Sources: en.wikipedia.org
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.