GABA-A receptor raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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 |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
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.
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.
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.
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.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
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.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Chemical synthesis of proteins is a valuable tool in chemical biology as it allows for the introduction of non-natural amino acids as well as residue-specific incorporation of "posttranslational modifications" such as phosphorylation, glycosylation, acetylation, and even ubiquitination. These properties are valuable for chemical biologists as non-natural amino acids can be used to probe and alter the functionality of proteins, while post-translational modifications are widely known to regulate the structure and activity of proteins. Although strictly biological techniques have been developed to achieve these ends, the chemical synthesis of peptides often has a lower technical and practical barrier to obtaining small amounts of the desired protein. To make protein-sized polypeptide chains with the small peptide fragments made by synthesis, chemical biologists can use the process of native chemical ligation. Native chemical ligation involves the coupling of a C-terminal thioester and an N-terminal cysteine residue, ultimately resulting in formation of a "native" amide bond. Other strategies that have been used for the ligation of peptide fragments using the acyl transfer chemistry first introduced with native chemical ligation include expressed protein ligation, sulfurization/desulfurization techniques, and use of removable thiol auxiliaries.
A 2017 study estimated the top running speed of Tyrannosaurus as 17 mph (27 km/h), speculating that Tyrannosaurus exhausted its energy reserves long before reaching top speed, resulting in a parabola-like relationship between size and speed. Another 2017 study hypothesized that an adult Tyrannosaurus was incapable of running due to high skeletal loads. Using a calculated weight estimate of 7 tons, the model showed that speeds above 11 mph (18 km/h) would have probably shattered the leg bones of Tyrannosaurus. The finding may mean that running was also not possible for other giant theropod dinosaurs like Giganotosaurus, Mapusaurus and Acrocanthosaurus. However, studies by Eric Snively and colleagues, published in 2019 indicate that Tyrannosaurus and other tyrannosaurids were more maneuverable than allosauroids and other theropods of comparable size due to low rotational inertia compared to their body mass combined with large leg muscles. As a result, it is hypothesized that Tyrannosaurus was capable of making relatively quick turns and could likely pivot its body more quickly when close to its prey, or that while turning, the theropod could "pirouette" on a single planted foot while the alternating leg was held out in a suspended swing during a pursuit. The results of this study potentially could shed light on how agility could have contributed to the success of tyrannosaurid evolution. In 2026, Boeye and colleagues analyzed the foot biomechanics of T. rex and determined that its foot likely functioned similarly to modern birds.
Despite the trial data failing to show improvements in bone density on QCT scans, its primary goal, there were improvements on DXA scans. In a September 2020 press release, Mereo said it was seeking to do a phase III trial in 2021, and had received a Rare Pediatric Disease (RPD) designation from the US Food and Drug Administration (FDA). Romosozumab, which is also a monoclonal antibody targeting sclerostin, is an approved drug in the US and EU for the treatment of osteoporosis. The pharmaceutical industry analyst Evercore has remarked that "it could wipe out setrusumab's economics", as romosozumab is priced more cheaply than a drug for a rare disease would be, claiming that it will be "vital" to Ultragenyx's profit margins to prove its setrusumab is more efficacious than romosozumab for OI. A clinical trial evaluating romosozumab's efficacy in OI began in September 2020 and as of September 2021 is ongoing. Ultragenyx predicts that its phase 2/3 trials for setrusumab will be completed in 2026.
Stirring of a given sample of amylose is said to form fibrillar crystals which are said to precipitate out of the mother liquor. These long fibrils can be imaged using electron microscopy revealing transverse striations resembling a shish-kebab. Amylose fibrils are categorized with having one of two morphologies: ones with small rodlike fibrils and others with lath-shaped crystals.
Sources: en.wikipedia.org
=== Chemistry === Like the other noble gases, krypton is chemically highly unreactive. The rather restricted chemistry of krypton in the +2 oxidation state parallels that of the neighboring element bromine in the +1 oxidation state; due to the scandide contraction it is difficult to oxidize the 4p elements to their group oxidation states. Until the 1960s no noble gas compounds had been synthesized. Following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride (KrF2) was reported in 1963. In the same year, KrF4 was reported by Grosse, et al., but was subsequently shown to be a mistaken identification. Under extreme conditions, krypton reacts with fluorine to form KrF2 according to the following equation:
Like most other antipsychotics, ziprasidone is sedating due primarily to serotonin and dopamine blockade. It has also been identified as a potent vesicular monoamine transporter 2 (VMAT2) inhibitor (IC50Tooltip half-maximal inhibitory concentration = 15 nM).
In October 1928, Chiang Kai-shek appointed Liu Wenhui as Chairman of the Sichuan Provincial Government. Liu's inauguration occurred on 12 March 1929. He declared that he would focus on relieving the people's suffering and advancing their welfare.
Sources: en.wikipedia.org
== Use in organic synthesis == Without the propionyl group on the oxygen, the non-esterified alcohol precursor of propoxyphene (both enantiomers, known as darvon alcohol and novrad alcohol) have been employed as stoichiometric chiral reagents for asymmetric carbonyl reduction reactions involving aluminium hydride reagents.
=== Alcohol dependence === Nalmefene is used in the European Union to reduce alcohol dependence and NICE recommends the use of nalmefene to reduce alcohol consumption in combination with psychological support for people who drink heavily. Based on a meta analysis, the usefulness of nalmefene for alcohol dependence is unclear. Nalmefene, in combination with psychosocial management, may decrease the amount of alcohol drunk by people who are alcohol dependent. The medication may also be taken "as needed", when a person feels the urge to consume alcohol.
An anorectic is a drug that reduces appetite, resulting in lower food consumption, leading to weight loss. These substances work by affecting the central nervous system or certain neurotransmitters to create a feeling of fullness or reduce the desire to eat. The understanding of anorexiant effects is crucial in the development of interventions for weight management, eating disorders, and related health concerns. The anorexiant effect can be induced through diverse mechanisms, ranging from hormonal regulation to neural signaling. Ghrelin, leptin, and peptide YY are among the hormones involved in appetite control. Additionally, neurotransmitters such as serotonin and dopamine in the central nervous system contribute significantly to the regulation of food intake. By contrast, an appetite stimulant is referred to as orexigenic. The term is (from the Greek ἀν- an- 'without' and ὄρεξις órexis 'appetite'), and such drugs are also known as anorexigenic, anorexiant, or appetite suppressant.
In 1956, a factory in the city released methylmercury in the industrial wastewater resulting in thousands of deaths and many other health problems. This incident alerted the world to the phenomenon of bioaccumulation. While all mercury compounds are toxic, organomercury compounds are especially dangerous because they are readily absorbed from the skin and can cross the blood–brain barrier to cause irreversible brain damage. Methylmercury and related compounds are thought to bind to the sulfur of cysteinyl residues in proteins. Nickel causes a contact dermatitis in up to 20% of people as result of prolonged contact with coins or jewelry. Industrial processing with highly toxic nickel carbonyl can cause acute poisoning; inhalation of nickel and nickel compounds in these settings can cause respiratory tract cancer. Chromium, arsenic, cadmium, mercury, and lead have a strong affinity for sulfur; in the human body they usually bind, via thiol groups (–SH), to enzymes responsible for controlling the speed of metabolic reactions. The resulting sulfur-metal bonds inhibit the proper functioning of the enzymes involved; human health deteriorates, sometimes fatally.
Sources: en.wikipedia.org
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
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.