If you have been reading about GABA-A receptor 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 2026-04-21. Numbers and descriptions here follow the published literature rather than marketing material.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
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.
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.
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.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
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.
Other analgesics work peripherally (i.e., not on the brain or spinal cord). Research is starting to show that morphine and related drugs may indeed have peripheral effects as well, such as morphine gel working on burns. Recent investigations discovered opioid receptors on peripheral sensory neurons. A significant fraction (up to 60%) of opioid analgesia can be mediated by such peripheral opioid receptors, particularly in inflammatory conditions such as arthritis, traumatic or surgical pain. Inflammatory pain is also blunted by endogenous opioid peptides activating peripheral opioid receptors. It was discovered in 1953, that humans and some animals naturally produce minute amounts of morphine, codeine, and possibly some of their simpler derivatives like heroin and dihydromorphine, in addition to endogenous opioid peptides. Some bacteria are capable of producing some semi-synthetic opioids such as hydromorphone and hydrocodone when living in a solution containing morphine or codeine respectively. Many of the alkaloids and other derivatives of the opium poppy are not opioids or narcotics; the best example is the smooth-muscle relaxant papaverine. Noscapine is a marginal case as it does have CNS effects but not necessarily similar to morphine, and it is probably in a category all its own.
Premarin, the major brand of CEEs in use, is manufactured by Pfizer and was first marketed in 1941 in Canada and in 1942 in the United States. It is the most commonly used form of estrogen in menopausal hormone therapy in the United States. However, it has begun to fall out of favor relative to bioidentical estradiol, which is the most widely used form of estrogen in Europe for menopausal hormone therapy. CEEs are available widely throughout the world. An estrogen preparation very similar to CEEs but differing in source and composition is esterified estrogens. In 2020, it was the 283rd most commonly prescribed medication in the United States, with more than 1 million prescriptions.
== Phase diagram == As the substance in a liquid body crosses the boundary from liquid to gas (see green arrow in phase diagram), the liquid changes into gas at a finite rate, while the amount of liquid decreases. When this happens within a heterogeneous environment, surface tension in the liquid body pulls against any solid structures the liquid might be in contact with. Delicate structures such as cell walls, the dendrites in silica gel, and the tiny machinery of microelectromechanical devices, tend to be broken apart by this surface tension as the liquid–gas–solid junction moves by. To avoid this, the sample can be brought via two possible alternate paths from the liquid phase to the gas phase without crossing the liquid–gas boundary on the phase diagram. In freeze-drying, this means going around to the left (low temperature, low pressure; blue arrow). However, some structures are disrupted even by the solid–gas boundary. Supercritical drying, on the other hand, goes around the line to the right, on the high-temperature, high-pressure side (red arrow). This route from liquid to gas does not cross any phase boundary, instead passing through the supercritical region, where the distinction between gas and liquid ceases to apply. Densities of the liquid phase and vapor phase become equal at critical point of drying.
This will typically be 22 kilometres (14 miles) wide, but could be more (if a state has chosen to claim a territorial sea of less than 22 kilometres), or less, if it would otherwise overlap another state's contiguous zone. However, unlike the territorial sea, there is no standard rule for resolving such conflicts, and the states in question must negotiate their own compromise. America invoked a contiguous zone out to 44 kilometres from the baseline on 29 September 1999. Exclusive economic zone: An exclusive economic zone extends from the baseline to a maximum of 370 kilometres (230 miles). A coastal nation has control of all economic resources within its exclusive economic zone, including fishing, mining, oil exploration, and any pollution of those resources. However, it cannot prohibit passage or loitering above, on, or under the surface of the sea that complies with the laws and regulations adopted by the coastal State in accordance with the provisions of the UN Convention, within that portion of its exclusive economic zone beyond its territorial sea. The only authority a state has over its EEZ is, therefore, its ability to regulate the extraction or spoliation of resources contained therein, and border-control measures implemented to this effect focus on the suppression of unauthorised commercial activity. Vessels not complying with a state's maritime policies may be subject to ship arrest and enforcement action by the state's authorities.
Sources: en.wikipedia.org
These people would often travel in large, organised groups from supermarket to supermarket, clearing the shelves of baby formula, then make substantial profits by sending the formula to China to be sold at a significant markup.
== Personal life == Helton came up as a major fan of Chicago Cubs' first baseman Mark Grace, himself a left-handed first baseman who was both a highly successful hitter and also excelled with the glove. Grace was nearing retirment as a player when Helton reached the major leagues. Helton took jersey number 17 as a tribute to Grace, and wore that uniform number for the rest of his career. Helton, his wife, and their two daughters reside in Knoxville, Tennessee. They previously lived in Brighton, Colorado, but sold their house in 2018. Helton and his family are good friends with Helton's former Tennessee Volunteers football teammate, Hall of Fame quarterback Peyton Manning. In 2013, Helton was arrested in Colorado for driving under the influence (DUI) of alcohol. He was fined $400, received a year of probation, and was ordered to perform 24 hours of community service. In 2019, Helton was cited for another DUI after crashing his car in Tennessee. He subsequently entered a treatment program. He was sentenced to two days in jail in 2020 after pleading guilty to the DUI.
This stirred up a wave of protest among the Catholic population, and bishops, Catholic organisations and the Centre Party itself united to combat the "red danger". This conflict bridged internal tensions within the party and secured its continual existence despite the turmoil of the revolution. The party however was weakened by its Bavarian wing splitting off and forming the Bavarian People's Party (BVP), which emphasised autonomy of the states and also took a more conservative course. In the 1919 elections for the Weimar National Assembly, the Centre Party gained 91 representatives, being the second largest party after the Social Democratic Party (SPD). The Centre's Constantin Fehrenbach was elected president of the National Assembly. The party actively cooperated with Social Democrats and left-liberal German Democratic Party (DDP) in drawing up the Weimar Constitution, which guaranteed what the Centre had been fighting for since its founding: equality for Catholics and autonomy for Catholic Church throughout Germany. The party was less successful in the school question. Although religious education remained an ordinary subject in most schools, the comprehensive, inter-denominational schools became default.
Sources: en.wikipedia.org
The oral sugar test also requires giving the horse only a single flake of hay at 10pm the night before the test. The following morning, karo corn syrup is given orally, and glucose and insulin levels are measured at 60 and 90 minutes after administration. Normal or excessively high insulin levels are diagnostic. However, equivocal test results require retesting at a later date, or performing a different test. A similar test is available outside the US, in areas where corn-syrup products are less readily available, where horses are given a morning meal of chaff with dextrose powder, and blood insulin levels are measured 2 hours later. Dynamic testing for insulin has higher sensitivity test than fasting insulin concentration, because insulin resistance may only become evident when challenged by hyperglycemia. There are various tests available for measuring changes in insulin concentration. They usually require a similar fasting protocol as the fasting insulin test.
=== Suicide === Fluoroquinolones can increase the risk of psychiatric symptoms, including depression and psychotic reactions. These may potentially lead to thoughts of suicide or suicide attempts. Recent reports from coroners on two suicides show the risks of fluoroquinolones in everyday life. Neither victim had a history of depression or mental health problems. However, both men had been prescribed ciprofloxacin shortly before they killed themselves. In a "Report to Prevent Future Deaths", mandated by UK law, one of the coroners noted that there is no compelling reason why patients should expect to risk becoming suicidal from an antibiotic unless this fact and potential symptoms were brought to their attention by the prescriber. A 2024 review from the UK's Medicines & Healthcare Products Regulatory Agency examined the effectiveness of current measures to reduce these identified risks of fluoroquinolones. It concluded, "Systemic fluoroquinolones must now only be prescribed when other commonly recommended antibiotics are inappropriate."
The α-globin chains are encoded by two closely linked genes HBA1 and HBA2 on chromosome 16; in a person with two copies on each chromosome, a total of four loci encode the α chain. Two alleles are maternal and two alleles are paternal in origin. Alpha-thalassemias result in decreased alpha-globin production, resulting in an excess of β chains in adults and excess γ chains in fetus and newborns.
=== Kinetic exclusion assay === Kinetic exclusion assay (KinExA) measures free (unbound) ligand or free receptor present in a mixture of ligand, receptor, and ligand-receptor complex. The measurements allow quantitation of the active ligand concentration and the binding constants (equilibrium, on and off rates) of the interaction.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.