If you have been reading about reversed-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 2025-12-09. Numbers and descriptions here follow the published literature rather than marketing material.
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.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
| Property | Value | Notes |
|---|---|---|
| Typical purity report | 95% or higher by HPLC | Area percentage at 214 nm |
| Identity confirmation | Mass spectrometry | Electrospray or MALDI |
| Powder storage | -20 C, desiccated | Protect from light |
| Solution storage | 2-8 C short term | Freeze aliquots for longer |
| Quality document | Certificate of analysis | States method and value |
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.
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.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
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.
Symptoms of intoxication from overdose include drowsiness, insomnia, stupor, agitation, coma, transient confusion, increased anxiety, ataxia, convulsions, oliguria, anuria, tachycardia or bradycardia, arrhythmia, AV block, hypotension, shock, respiratory depression, and, rarely, cardiac arrest.
== January 31, 1982 (Sunday) == The documentary Let Poland be Poland was televised around the world and reportedly watched by 185,000,000 in 50 nations. Hosted by Charlton Heston in the U.S., the show included appearances by Paul McCartney, Orson Welles, Henry Fonda, Kirk Douglas, Max von Sydow, James A. Michener, Glenda Jackson, Madeleine Albright and the song "Ever Homeward", sung by Frank Sinatra. The show also featured recorded segments from world leaders, including U.S. President Ronald Reagan, UK Prime Minister Margaret Thatcher, German Chancellor Helmut Schmidt, Japanese premier Zenkō Suzuki, French President François Mitterrand, and prime ministers Pierre Trudeau (Canada), Arnaldo Forlani (Italy), Adolfo Suárez (Spain), Kåre Willoch (Norway), Bülend Ulusu (Turkey), Francisco Pinto Balsemão (Portugal), Wilfried Martens (Belgium), Pierre Werner (Luxembourg) and Gunnar Thoroddsen (Iceland). The Statute of Autonomy of the Principality of Asturias went into effect, recognizing the right of self-government of the Spanish region of 78 municipalities in areas formerly occupied by the medieval Kingdom of Asturias, including the capital, Oviedo. Spain's province of Santander was renamed Cantabria
==== Extraterritorial data access ==== The CLOUD Act allows United States authorities to request data from covered service providers, including some AI service providers, regardless of where the data is physically stored. Courts can require parent companies to provide data held by their subsidiaries, and such orders may be accompanied by nondisclosure requirements preventing the provider from notifying affected users. This framework has been described in legal commentary as creating legal tension with Article 48 of the General Data Protection Regulation (GDPR), which restricts the transfer of personal data in response to foreign court or administrative orders unless based on an international agreement. As a result, service providers operating in both jurisdictions may face competing legal obligations under U.S. and EU law.
== Epidemiology == Plantar fasciitis is the most common type of plantar fascia injury and is the most common reason for heel pain, responsible for 80% of cases. The condition tends to occur more often in women, military recruits, older athletes, dancers, the obese, and young male athletes. Plantar fasciitis is estimated to affect 1 in 10 people at some point during their lives, most commonly those 40-60 years old. In the United States alone, more than two million people receive treatment annually at a cost estimated to be $284 million.
Sources: en.wikipedia.org
== Industrial use == Butane-1,4-diol is used industrially as a solvent and in the manufacture of some types of plastics, elastic fibers and polyurethanes. In organic chemistry, 1,4-butanediol is used for the synthesis of γ-butyrolactone (GBL). In the presence of phosphoric acid and high temperature, it dehydrates to the important solvent tetrahydrofuran. At about 200 °C in the presence of soluble ruthenium catalysts, the diol undergoes dehydrogenation to form butyrolactone. It is used to synthesize 1,4-butanediol diglycidyl ether which is then used as a reactive diluent for epoxy resins. 1,4-Butanediol is used in the production of polybutylene terephthalate (PBT) plastic. World production of butane-1,4-diol was claimed to be about one million metric tons per year and market price is about US$2,000 (€1,600) per ton in 2005. In 2013, worldwide production was claimed to be billions of pounds (consistent with approximately one million metric tons). Almost half of it is dehydrated to tetrahydrofuran to make fibers such as Spandex. The largest producer is BASF.
CT imaging uses X-rays in conjunction with computing algorithms to image the body. In CT, an X-ray tube opposite an X-ray detector (or detectors) in a ring-shaped apparatus rotates around a patient, producing a computer-generated cross-sectional image (tomogram). CT is acquired in the axial plane, with coronal and sagittal images produced by computer reconstruction. Radiocontrast agents are often used with CT for enhanced delineation of anatomy. Although radiographs provide higher spatial resolution, CT can detect more subtle variations in attenuation of X-rays (higher contrast resolution). CT exposes the patient to significantly more ionizing radiation than a radiograph.
Siddhartha Roy (born 1 April 1954) is an Indian Chemical and Structural biologist, biophysicist, former director of the Indian Institute of Chemical Biology and the former director (officiating) of Bose Institute. Widely known for his studies on Gene Regulation, Peptidomimetics, bacteriophage lambda and protein synthesis, he is an elected fellow of the Indian Academy of Sciences and the Indian National Science Academy. In 1999, the Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, for his contributions to Biological sciences.
The market square also hosts the former washhouse and public baths of the neighbourhood, among the oldest examples of their kind in Turin (1905). One of the main thoroughfares crossing Borgo San Secondo is Via Sacchi, which serves as an ideal gate to the city centre: its Serlian arcades on the west side of the street (the east side is enclosed by Porta Nuova railway station service buildings) host some significant boutiques and hotels, such as the historic Pfatisch pastry shop and the Turin Palace Hotel (totally refurbished and reopened in 2015). South of Via Sacchi, Ospedale Mauriziano is one of the ancient and major hospitals of the city. Going further southwards, it is possible to appreciate an interesting residential cluster of old public housing gravitating around Via Arquata.
=== 5 January === Russian Orthodox Church Primate Patriarch Kirill called for a Christmas ceasefire so that people could attend Orthodox Christmas services on 6–7 January. Turkish President Recep Tayyip Erdogan also called for a "unilateral cease-fire"; afterwards, Putin]] ordered the Russian military to hold a 36-hour cease-fire for the Russian Orthodox Christmas. Ukraine rejected Russia's cease-fire proposal. The UK MoD said that fighting had "continued at a routine level into the Orthodox Christmas period." The first group of 24 prisoners recruited by PMC Wagner, fighting in Ukraine, have finished their six months contracts and have been released with full amnesty for their past crimes. In a joint statement President Biden and Chancellor Olaf Scholz announced that the German government had decided to provide Ukraine with a Patriot missile system and 40 Marder Infantry Fighting Vehicles, while the United States government would provide around 50 Bradley Fighting Vehicles.
Sources: en.wikipedia.org
== History and development == The first site was launched in 2001 by the American Association for Clinical Chemistry, the scientific society for clinical laboratory science. This led to a collaboration with professional societies in 17 other countries representing the laboratory medicine community. Each site is separately managed to allow both appropriate languages and information that matches local needs.
CPC Scientific Inc. is a contract research, development and manufacturing organization (CDMO) that specializes in the production of peptides and oligonucleotides. The company provides custom synthesis, process development, and manufacturing services for research, clinical, and commercial applications.
Symptoms of ethanol overdose may include nausea, vomiting, CNS depression, coma, acute respiratory failure, or death. Levels of even less than 0.1% can cause intoxication, with unconsciousness often occurring at 0.3–0.4%. Death from ethanol consumption is possible when blood alcohol levels reach 0.4%. A blood level of 0.5% or more is commonly fatal. The oral median lethal dose (LD50) of ethanol in rats is 5,628 mg/kg. Directly translated to human beings, this would mean that if a person who weighs 70 kg (150 lb) drank a 500 mL (17 US fl oz) glass of pure ethanol, they would have an estimated 50% risk of dying. The highest blood alcohol level ever recorded, in which the subject survived, is 1.41%.
6 January – The Prime Minister responds to X owner Elon Musk and others he accuses of "spreading lies and misinformation" over grooming gangs. Starmer tells reporters that these online debates have now "crossed a line", resulting in threats against MPs, including Safeguarding Minister Jess Phillips. MPs debate an online petition calling for a re-run of the 2024 general election in Westminster Hall, a secondary debating chamber. Treasury Minister Tulip Siddiq refers herself to the Independent Adviser on Ministers' Interests after controversy over her links to her aunt's political movement in Bangladesh. Justin Welby's tenure as Archbishop of Canterbury comes to an end following his resignation in November 2024. Archbishop of York Stephen Cottrell assumes temporary charge of the Church of England from the following day. 7 January – Minister Jess Phillips says Elon Musk is putting her in danger with misinformation about grooming gangs. 8 January – MPs vote 364–111 against a Conservative proposal to require the UK government to establish an inquiry into grooming gangs. The Liberal Democrats are ordered to pay £14,000 to Natalie Bird, a former parliamentary candidate who says she was driven out of the party and barred from standing as an MP over her gender-critical views. Sir Oliver Robbins is appointed Permanent Secretary to the Foreign Office, succeeding Sir Philip Barton. Patrick Harvie, the co-leader of the Scottish Greens, is to take time off from the Scottish Parliament because of a medical procedure.
=== Sleep apnea === Sleep apnea is a condition characterized by repeated interruptions in breathing during sleep, significantly affecting the flow of blood through the brain's blood vessels. These interruptions cause intermittent hypoxia, leading to vascular changes such as the constriction of cerebral blood vessels, thereby impacting overall brain blood flow. Sleep apnea can also result in reduced blood flow in the ciliary artery area, contributing to the development of NAION through various mechanisms. The results of a retrospective study investigating high altitude (7,000-9,000 feet) as a potential risk factor for NAION suggested that high-altitude-associated NAION might be linked to undiagnosed obstructive sleep apnea. The study concluded that NAION could occur under high-altitude conditions, often in younger individuals with obstructive sleep apnea and "disc-at-risk". Each apnea episode typically causes temporary increases in blood pressure and heart rate, leading to fluctuations that can result in irregular blood flow to the brain. This may cause long-term changes in the structure and function of cerebral blood vessels. The brain's mechanism for maintaining constant blood flow despite changes in systemic blood pressure, known as cerebral autoregulation, can be impaired by sleep apnea. This impairment results in periods of both reduced and excessive cerebral blood flow. Repeated airway obstruction during sleep leads to intermittent hypoxia, causing oxidative stress and damaging endothelial cells of blood vessels, including those supplying the optic nerve head.
Sources: en.wikipedia.org
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.
Dry powder is kept frozen, desiccated, and shielded from light. Dissolved material is aliquoted and frozen to limit freeze-thaw cycles. Short-term refrigerated storage is common for working solutions.
Russia registers it as a prescription nasal product. Most other markets classify it as a research chemical with no approved medical use. Oversight of purity and labeling is consequently minimal in those markets.
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.