If you have been reading about pharmacokinetics 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.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
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.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Derived from the seven-residue sequence |
| Molecular weight | About 751.9 g/mol | Average mass; the monoisotopic value is slightly lower |
| Residue count | Seven amino acids | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent compound | Tuftsin (Thr-Lys-Pro-Arg) | Selank extends tuftsin at the C-terminus |
| Compound class | Synthetic short peptide | Studied in a research setting; not a licensed drug in most markets |
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.
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.
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.
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.
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.
Small-cell carcinoma of the lung usually presents in the central airways and infiltrates the submucosa leading to the narrowing of bronchial airways. Common symptoms include cough, dyspnea, weight loss, and debility. Over 70% of patients with small-cell carcinoma present with metastatic disease; common sites include the liver, adrenals, bone, and brain. Due to its high grade neuroendocrine nature, small-cell carcinomas can produce ectopic hormones, including adrenocorticotropic hormone (ACTH) and anti-diuretic hormone (ADH). Ectopic production of large amounts of ADH leads to syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH). Lambert–Eaton myasthenic syndrome is a well-known paraneoplastic condition linked to small-cell carcinoma. Approximately half of all individuals diagnosed with Lambert–Eaton myasthenic syndrome will eventually be found to have a small-cell carcinoma of the lung.
According to Bloomberg News, 2K Games was developing a remake of the original BioShock game but shelved the project in 2025. BioShock was remastered to support 1080p and higher framerates as part of the 2016 BioShock: The Collection release for Windows, PlayStation 4, and Xbox One systems. The remastering was performed by Blind Squirrel Games and published by 2K Games. A standalone version of BioShock Remastered was released for macOS by Feral Interactive on August 22, 2017. The standalone version of the remastered version of BioShock along with The Collection were released on May 29, 2020, on the Nintendo Switch.
The documented range of this species lies roughly south of a line from southeastern Nebraska through southern Iowa, Illinois, and Indiana to southwestern Ohio. In the southern states, it is native from central Texas to western Georgia and north to Kentucky. Despite rumors to the contrary, the brown recluse spider has not established itself in California or anywhere outside its native range. There are other species of the genus Loxosceles native to the southwestern part of the United States, including California, which may resemble the brown recluse, but interactions between humans and the recluse species in California and the region are rare because those species' native ranges lie outside of dense human populations. The number of "false positive" reports based on misidentifications is considerable; in a nationwide study where people submitted spiders that they thought were brown recluses, of 581 from California only one was a brown recluse—submitted by a family that moved from Missouri and brought it with them (compared to specimens submitted from Missouri, Kansas, and Oklahoma, where between 75% and 90% were recluses). From this study, the most common spider submitted from California as a brown recluse was in the genus Titiotus, whose bite is deemed harmless. A similar study documented that various arachnids were routinely misidentified by physicians, pest control operators, and other non-expert authorities, who told their patients or clients that the spider they had was a brown recluse when in fact it was not.
Sources: en.wikipedia.org
==== Natural biocontrol and elicitor ==== In agriculture, chitosan is typically used as a natural seed treatment and plant growth enhancer, and as an ecologically friendly biopesticide substance that boosts the innate ability of plants to defend themselves against fungal infections. Degraded molecules of chitin/chitosan exist in soil and water. Chitosan applications for plants and crops are regulated in the USA by the Environmental Protection Agency, and the USDA National Organic Program regulates its use on organic certified farms and crops. EPA-approved, biodegradable chitosan products are allowed for use outdoors and indoors on plants and crops grown commercially and by consumers. In the European Union and United Kingdom, chitosan is registered as a "basic substance" for use as a biological fungicide and bactericide on a wide range of crops. The natural biocontrol ability of chitosan should not be confused with the effects of fertilizers or pesticides upon plants or the environment. Chitosan active biopesticides represent a new tier of cost-effective biological control of crops for agriculture and horticulture. The biocontrol mode of action of chitosan elicits natural innate defense responses within plant to resist insects, pathogens, and soil-borne diseases when applied to foliage or the soil. Chitosan increases photosynthesis, promotes and enhances plant growth, stimulates nutrient uptake, increases germination and sprouting, and boosts plant vigor.
FAD, or flavin adenine dinucleotide, is a prosthetic group (a non-polypeptide unit bound to a protein that is required for function) that consists of an adenine nucleotide and a flavin mononucleotide. FAD is a unique electron acceptor. Its fully reduced form is FADH2 (known as the hydroquinone form), but FAD can also be partially oxidized as FADH by either reducing FAD or oxidizing FADH2. Dehydrogenases typically fully reduce FAD to FADH2. The production of FADH is rare. The double-bonded nitrogen atoms in FAD make it a good acceptor in taking two hydrogen atoms from a substrate. Because it takes two atoms rather than one, FAD is often involved when a double bond is formed in the newly oxidized substrate. FAD is unique because it is reduced by two electrons and two protons, as opposed to both NAD+ and NADP, which only take one proton.
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Sources: en.wikipedia.org
=== Human health === The effect of rBGH on human health is an ongoing debate, in part due to the lack of conclusive evidence. A few of the most debated issues include: Insulin-like growth factor 1 (IGF-1) is a hormone found in humans that is responsible for growth promotion, protein synthesis, and insulin actions over the lifecycle. The hormone has been shown to influence the growth of tumors in some studies and may be linked to the development of prostate, colorectal, breast, and other cancers. IGF-1 is also found in milk. Previous research has proposed an increase of IGF-1 in rBST-treated cows, but this claim is currently not substantiated. In addition, no current evidence shows that orally consumed IGF-1 is absorbed in humans and the dietary amount is negligible when compared to what the body produces on its own. "IGF-1 in milk is not denatured (inactivated) by pasteurization. The extent to which intact, active IGF-1 is absorbed through the human digestive tract remains uncertain." The American Cancer Society has reviewed the evidence concerning IGF-1 in milk from rBST-treated cows, and found that: "While there may be a link between IGF-1 blood levels and cancer, the exact nature of this link remains unclear. Some studies have shown that adults who drink milk have about 10% higher levels of IGF-1 in their blood than those who drink little or no milk. But this same finding has also been reported in people who drink soy milk.
In the early years of constitutional government, the strengths and weaknesses of the Meiji Constitution were revealed. A small clique of Satsuma and Chōshū elite continued to rule Japan, becoming institutionalized as an extra-constitutional body of genrō (elder statesmen). Collectively, the genrō made decisions reserved for the Emperor, and the genrō, not the Emperor, controlled the government politically. Throughout the period, however, political problems usually were solved through compromise, and political parties gradually increased their power over the government and held an ever-larger role in the political process as a result. Between 1891 and 1895, Ito served as Prime Minister with a cabinet composed mostly of genrō who wanted to establish a government party to control the House of Representatives. Although not fully realized, the trend toward party politics was well established.
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=== Factors affecting production === The effects of carbon, nitrogen sources, and amino acids on growth and tabtoxin production by pv. tabaci were examined by varying the components of a defined basal medium, which contained the following nutrients per liter: sucrose (10 g), KNO3 (5 g), MgSO4·7H2O (0.2 g), CaCl2·2H2O (0.11 g), FeSO4·7H2O (20 mg), NaH2PO4·2H2O (0.9 g) and H2PO4·3H2O (1 g). Both growth and quantity of tabtoxin synthesized were significantly affected by carbon source, nitrogen source, and amino acid supplements. Sorbitol, xylose, and sucrose proved to be the best carbon sources for tabtoxin production. Specific toxin production was very low using glucose as a single carbohydrate source, although bacterial growth was well supported by glucose. Amount and type of nitrogen sources (NH4Cl or KNO3) affected the growth of pv. tabaci and quantities of tabtoxin produced. Nitrate is the best of these two forms of nitrogen for production of tabtoxin. Some progress has been made on elucidating factors that regulate tabtoxin biosynthesis in P. syringae.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.
Tuftsin contains four residues, while selank carries an additional Pro-Gly-Pro segment at the carboxyl end. That extension is intended to reduce enzymatic cleavage. Comparative pharmacokinetic data in humans remain limited.
No single receptor target is widely accepted as the definitive mediator of the reported effects. Proposed contributors include GABAergic modulation, shifts in monoamine turnover, and altered neuropeptide degradation. The mechanism is treated in the literature as unresolved.
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.