pharmacokinetics comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
| 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 |
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.
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.
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.
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.
Gel permeation chromatography is conducted almost exclusively in chromatography systems. The experimental design is not much different from other techniques of High Performance liquid chromatography. Samples are dissolved in an appropriate solvent, in the case of GPC these tend to be organic solvents and after filtering the solution it is injected onto a column. The separation of multi-component mixture takes place in the column. The constant supply of fresh eluent to the column is accomplished by the use of a pump. Since most analytes are not visible to the naked eye a detector is needed. Often multiple detectors are used to gain additional information about the polymer sample. The availability of a detector makes the fractionation convenient and accurate.
=== Solvent === Solvents are usually chosen based on the applications of the gel. They can be hydrophilic, lipophilic, or organic. Individual solvents can be used alone or as a mixture. Some examples of solvents include purified water, glycerin, glycols, alcohols, sucrose, toluene, and mineral oils.
Emus were used as a source of food by indigenous Australians and early European settlers. Emus are inquisitive birds and have been known to approach humans if they see unexpected movement of a limb or piece of clothing. In the wild, they may follow and observe people. Aboriginal Australians used a variety of techniques to catch the birds, including spearing them while they drank at waterholes, catching them in nets, and attracting them by imitating their calls or by arousing their curiosity with a ball of feathers and rags dangled from a tree. The pitchuri thornapple (Duboisia hopwoodii), or some similar poisonous plant, could be used to contaminate a waterhole, after which the disoriented emus were easy to catch. Another stratagem was for the hunter to use a skin as a disguise, and the birds could be lured into a camouflaged pit trap using rags or imitation calls. Aboriginal Australians only killed emus out of necessity, and frowned on anyone who hunted them for any other reason. Every part of the carcass had some use; the fat was harvested for its valuable, multiple-use oil, the bones were shaped into knives and tools, the feathers were used for body adornment and the tendons substituted for string. The early European settlers killed emus to provide food and used their fat for fuelling lamps. They also tried to prevent them from interfering with farming or invading settlements in search of water during drought. An extreme example of this was the Emu War in Western Australia in 1932.
Sources: en.wikipedia.org
== Education and career == Flegg received her PhD in Applied Mathematics from Queensland University of Technology in 2009. Her dissertation, "Mathematical Modelling of Chronic Wound Healing", was supervised by Dr. Sean McElwain. From 2010 to 2013, she was a researcher at the University of Oxford developing mathematical models for the spread of resistance to antimalarial drugs. From 2014 to early 2017, she was a mathematical lecturer in the School of Mathematical Sciences at Monash University. In May 2017, she joined the School of Mathematics and Statistics at the University of Melbourne as a senior lecturer in Applied Mathematics and was promoted to associate professor in 2020 and again to Professor in 2022. Flegg is an expert in the field of mathematical biology, with special focus in infectious disease epidemiology, wound healing and tumor growth. As of 2020, Flegg also serves as an editorial board member for PLOS Computational Biology, eLife and the Bulletin of Mathematical Biology.
=== Modifications in nature === Ribokinase catalyzes the conversion of d-ribose to d-ribose 5-phosphate. Once converted, d-ribose-5-phosphate is available for the manufacturing of the amino acids tryptophan and histidine, or for use in the pentose phosphate pathway. The absorption of d-ribose is 88–100% in the small intestines (up to 200 mg/kg·h). One important modification occurs at the C2' position of the ribose molecule. By adding an O-alkyl group, the nuclear resistance of the RNA is increased because of additional stabilizing forces. These forces are stabilizing because of the increase of intramolecular hydrogen bonding and an increase in the glycosidic bond stability. The resulting increase of resistance leads to increases in the half-life of siRNA and the potential therapeutic potential in cells and animals. The methylation of ribose at particular sites is correlated with a decrease in immune stimulation.
=== Europe === In Europe, the number of individuals affected by osteoarthritis has increased from 27.9 million in 1990 to 50.8 million in 2019. Hand osteoarthritis was the second most prevalent type, affecting an estimated 12.5 million people. In 2019, knee osteoarthritis was the 18th most common cause of years lived with disability (YLDs) in Europe, accounting for 1.28% of all YLDs. This has increased from 1.12% in 1990.
Sources: en.wikipedia.org
==== Inhalation and smoking ==== Results from epidemiological studies indicate that the risk of lung cancer increases with exposure to residential radon. One well known potential source of error in these studies is smoking, which is the main risk factor for lung cancer. In the US, cigarette smoking is estimated to cause 80% to 90% of all lung cancers. Radon, like other known or suspected external risk factors for lung cancer, is a threat for smokers and former smokers. According to the EPA, the risk of lung cancer for smokers is significantly higher when they are exposed to radon due to the synergistic effects of radon with smoking. For this population, about 62 people in a total of 1,000 will die of lung cancer, compared to 7 people in a total of 1,000 for people who have never smoked. A 2005 review article by Darby and colleagues analyzing 13 different case studies across Europe stated: "It is not appropriate to talk simply of a risk from radon in homes. The risk is from smoking, compounded by a synergistic effect of radon for smokers. Without smoking, the effect seems to be so small as to be insignificant." According to Darby, there is a difference in risk for the histological subtypes of lung cancer and radon exposure. Small-cell lung carcinoma, which has a high correlation with smoking, has a higher risk after radon exposure. For other histological subtypes, such as adenocarcinoma, the type that primarily affects non-smokers, the risk from radon appears to be lower.
== Medical uses == Stimulants are widely used throughout the world as prescription medicines as well as without a prescription (either legally or illicitly) as performance-enhancing or recreational drugs. Stimulants produce a noticeable crash or comedown at the end of their effects. In the US, the most frequently prescribed stimulants as of 2013 were lisdexamfetamine (Vyvanse), methylphenidate (Ritalin), and amphetamine (Adderall). It was estimated in 2015 that the percentage of the world population that had used cocaine during a year was 0.4%. For the category "amphetamines and prescription stimulants" (with "amphetamines" including amphetamine and methamphetamine) the value was 0.7%, and for MDMA 0.4%. Stimulants have been used in medicine for many conditions including obesity, sleep disorders, mood disorders, impulse-control disorders, asthma, nasal congestion and, in case of cocaine, as local anesthetics. Drugs used to treat obesity are called anorectics and generally include drugs that follow the general definition of a stimulant, but other drugs such as cannabinoid receptor antagonists also belong to this group. Eugeroics are used in management of sleep disorders characterized by excessive daytime sleepiness, such as narcolepsy, and include stimulants such as modafinil and pitolisant. Stimulants are used in impulse control disorders such as ADHD and off-label in mood disorders such as major depressive disorder to increase energy, focus, and elevate mood.
There are many mechanisms for the repair of damaged double stranded DNA. PARP1 may function as a synapsis factor in alternative non-homologous end joining. Additionally, it has been proposed that PARP1 is required to slow replication forks following DNA damage and promotes homologous recombination at replication forks that may be dysfunctional. It is possible that PARP1 and PARP3 work together in repair of double-stranded DNA and it has been shown that PARP3 is critical for double-stranded break resolution. There are two hypotheses by which PARP1 and PARP3 coincide. The first hypothesis states that the two (ADP-ribosyl)transferases serve to function for each other's inactivity. If PARP3 is lost, this results in single-strand breaks, and thus the recruitment of PARP1. A second hypothesis suggests that the two enzyme work together; PARP3 catalyzes mono(ADP-ribosyl)ation and short poly(ADP-ribosyl)ation and serves to activate PARP1. The PARPs have many protein targets at the site of DNA damage. KU protein and DNA-PKcs are both double-stranded break repair components with unknown sites of ADP-ribosylation. Histones are another protein target of the PARPs. All core histones and linker histone H1 are ADP-ribosylated following DNA damage. The function of these modifications is still unknown, but it has been proposed that ADP-ribosylation modulates higher-order chromatin structure in efforts to facilitate more accessible sites for repair factors to migrate to the DNA damage.
Up to 20% of people taking isoniazid experience peripheral neuropathy when taking daily doses of 6 mg/kg of body weight or higher. Gastrointestinal reactions include nausea and vomiting. Aplastic anemia, thrombocytopenia, and agranulocytosis due to lack of production of red blood cells, platelets, and white blood cells by the bone marrow respectively, can also occur. Hypersensitivity reactions are common and can present with a maculopapular rash and fever. Gynecomastia may also occur. Isoniazid inhibits pyridoxine phosphokinase, which is responsible for maintaining the active form of vitamin B6, pyridoxal 5′-phosphate (P5P). Isoniazid is also associated with increased excretion of pyridoxine. Altogether, this means that isoniazid can cause pyridoxine (vitamin B6) deficiency, leading to peripheral neuropathy and (rarely) sideroblastic anemia via insufficient P5P provided to δ-aminolevulinic acid synthase. It is recommended that isoniazid be taken with pyridoxine in persons at risk of peripheral neuropathy as well as those who have already developed peripheral neuropathy. Asymptomatic elevation of serum liver enzyme concentrations occurs in 10% to 20% of people taking INH, and liver enzyme concentrations usually return to normal even when treatment is continued. Isoniazid has a boxed warning for severe and sometimes fatal hepatitis, which is age-dependent at a rate of 0.3% in people 21 to 35 years old and over 2% in those over age 50. Symptoms suggestive of liver toxicity include nausea, vomiting, abdominal pain, dark urine, right upper quadrant pain, and loss of appetite.
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.
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.