peptide purity 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 2026-05-24 and is reviewed periodically as new material appears.
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.
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.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
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.
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.
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.
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.
== Expression/Production systems == Different organisms may be used to express a gene's target protein, and the expression vector used will therefore have elements specific for use in the particular organism. The most commonly used organism for protein production is the bacterium Escherichia coli. However, not all proteins can be successfully expressed in E. coli, or be expressed with the correct form of post-translational modifications such as glycosylations, and other systems may therefore be used.
Restricting population size is a proposed solution to malnutrition. Thomas Malthus argues that population growth can be controlled by natural disasters and by voluntary limits through "moral restraint." Robert Chapman suggests that government policies are a necessary ingredient for curtailing global population growth. The United Nations recognizes that poverty and malnutrition (as well as the environment) are interdependent and complementary with population growth. According to the World Health Organization, "Family planning is key to slowing unsustainable population growth and the resulting negative impacts on the economy, environment, and national and regional development efforts". However, more than 200 million women worldwide lack adequate access to family planning services. There are different theories about what causes famine. Some theorists, like the Indian economist Amartya Sen, believe that the world has more than enough resources to sustain its population. In this view, malnutrition is caused by unequal distribution of resources and under- or unused arable land. For example, Sen argues that "no matter how a famine is caused, methods of breaking it call for a large supply of food in the Public Distribution System. This applies not only to organizing rationing and control, but also to undertaking work programmes and other methods of increasing purchasing power for those hit by shifts in exchange entitlements in a general inflationary situation."
One of the first Norman mercenaries to serve as a Byzantine general was Hervé in the 1050s. By then, however, there were already Norman mercenaries serving as far away as Trebizond and Georgia. They were based at Malatya and Edessa, under the Byzantine duke of Antioch, Isaac Komnenos. In the 1060s, Robert Crispin led the Normans of Edessa against the Turks. Roussel de Bailleul even tried to carve out an independent state in Asia Minor with support from the local population in 1073, but he was stopped in 1075 by the Byzantine general and future emperor Alexius Komnenos. Some Normans joined Turkish forces to aid in the destruction of the Armenian vassal-states of Sassoun and Taron in far eastern Anatolia. Later, many took up service with the Armenian state further south in Cilicia and the Taurus Mountains. A Norman named Oursel led a force of "Franks" into the upper Euphrates valley in northern Syria. From 1073 to 1074, 8,000 of the 20,000 troops of the Armenian general Philaretus Brachamius were Normans—formerly of Oursel—led by Raimbaud. They even lent their ethnicity to the name of their castle: Afranji, meaning "Franks". The known trade between Amalfi and Antioch and between Bari and Tarsus may be related to the presence of Italo-Normans in those cities while Amalfi and Bari were under Norman rule in Italy. Several families of Byzantine Greece were of Norman mercenary origin during the period of the Comnenian Restoration, when Byzantine emperors were seeking out western European warriors.
=== Origin of selenoproteins === From about three billion years ago, prokaryotes evolved selenoprotein families centering around the selenocysteine machinery. Several selenoprotein families are known in bacteria, archaea, and eukaryotes, invariably owing to the presence of selenocysteine. They protect their host cells from oxidative damage. Selenium enzymes are involved in utilization of the small reducing molecules glutathione and thioredoxin, common intracellular antioxidants and redox partners. Selenoprotein families of GSH-Px and the deiodinases of eukaryotic cells seem to have a bacterial phylogenetic origin. The selenocysteine-containing form occurs in species as diverse as green algae, diatoms, sea urchins, fish, and chickens.
Sources: en.wikipedia.org
== External links == What's in an Oil Drop? An Introduction to Fourier Transform Ion Cyclotron Resonance (FT-ICR) for Non-scientists National High Magnetic Field Laboratory Scottish Instrumentation Resource Centre for Advanced Mass Spectrometry Fourier-transform Ion Cyclotron Resonance (FT-ICR) FT-ICR Introduction University of Bristol
Myristicin poisoning can be detected by testing levels of myristicin in the blood. There are no known antidotes for myristicin poisoning, and treatment focuses on symptom management and potential sedation in cases of extreme delirium or aggravation.
=== Sex === Over 70 million adults in U.S. are obese (35 million men and 35 million women). 99 million are overweight (45 million women and 54 million men). NHANES 2016 statistics showed that about 39.6% of American adults were obese. Men had an age-adjusted rate of 37.9% and Women had an age-adjusted rate of 41.1%. The CDC provided a data update in May 2017 stating that for adults 20 years and older, the crude obesity rate was 39.8% and the age adjusted rate was measured to be 39.7%. Including the obese, 71.6% of all American adults age 20 and above were overweight.
Sources: en.wikipedia.org
The ammonium ion (NH+4) has very similar properties to the heavier alkali metals, acting as an alkali metal intermediate between potassium and rubidium, and is often considered a close relative. For example, most alkali metal salts are soluble in water, a property which ammonium salts share. Ammonium is expected to behave stably as a metal (NH+4 ions in a sea of delocalised electrons) at very high pressures (though less than the typical pressure where transitions from insulating to metallic behaviour occur around, 100 GPa), and could possibly occur inside the ice giants Uranus and Neptune, which may have significant impacts on their interior magnetic fields. It has been estimated that the transition from a mixture of ammonia and dihydrogen molecules to metallic ammonium may occur at pressures just below 25 GPa. Under standard conditions, ammonium can form a metallic amalgam with mercury. Other "pseudo-alkali metals" include the alkylammonium cations, in which some of the hydrogen atoms in the ammonium cation are replaced by alkyl or aryl groups. In particular, the quaternary ammonium cations (NR+4) are very useful since they are permanently charged, and they are often used as an alternative to the expensive Cs+ to stabilise very large and very easily polarisable anions such as HI−2. Tetraalkylammonium hydroxides, like alkali metal hydroxides, are very strong bases that react with atmospheric carbon dioxide to form carbonates.
=== On bone formation === Due to myostatin's ability to inhibit muscle growth, it can indirectly inhibit bone formation by decreasing the load on the bone. It has a direct signalling effect on bone formation as well as degradation. Knockdown of myostatin has been shown to reduce formation of osteoclasts (multinucleated cells responsible for the breakdown of bone tissue) in mice modeling rheumatoid arthritis. Rheumatoid arthritis is an autoimmune disorder that, among other effects, leads to the degradation of the bone tissue in affected joints. Myostatin has not, however, been shown to be solely sufficient for the formation of mature osteoclasts from macrophages, only an enhancer. Myostatin expression is increased around the site of a fracture. Suppression of myostatin at the fracture site leads to increased callus and overall bone size, further supporting the inhibitory effect of myostatin on bone formation. One study by Berno Dankbar et al., 2015 found that myostatin deficiency leads to a notable reduction in inflammation around a fracture site. Myostatin affects osteoclastogenesis by binding to receptors on osteoclastic macrophages and causing a signalling cascade. The downstream signalling cascade enhances the expression of RANKL-dependent integrin αvβ3, DC-STAMP, calcitonin receptors, and NFATc1 (which is part of the initial intracellular complex that starts the signaling cascade, along with R-Smad2 and ALK4 or ALK5).
== Structure == Stromal connective tissues are found in the stroma; this tissue belongs to the group connective tissue proper. The function of connective tissue proper is to secure the parenchymal tissue, including blood vessels and nerves of the stroma, and to construct organs and spread mechanical tension to reduce localised stress. Stromal tissue is primarily made of extracellular matrix containing connective tissue cells. Extracellular matrix is primarily composed of ground substance - a porous, hydrated gel, made mainly from proteoglycan aggregates - and connective tissue fibers. There are three types of fibers commonly found within the stroma: collagen type I, elastic, and reticular (collagen type III) fibres.
Sources: en.wikipedia.org
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.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
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.