A practical reference on GABA-A receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-12-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
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.
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.
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.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
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.
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.
=== Interactions === Human herpesvirus 6 lives primarily on humans and, while variants of the virus can cause mild to fatal illnesses, can live commensally on its host. It has been demonstrated that HHV-6 fosters the progression of HIV-1 upon coinfection in T cells. HHV-6 upregulates the expression of the primary HIV receptor CD4, thus expanding the range of HIV susceptible cells. Several studies also have shown that HHV-6 infection increases production of inflammatory cytokines that enhance in vitro expression of HIV-1, such as TNF-alpha, IL-1 beta, and IL-8. A more recent in vivo study shows HHV-6A coinfection to dramatically accelerate the progression from HIV to AIDS in pigtailed macaques. HHV-6 has also been demonstrated to transactivate Epstein–Barr virus.
cytidine (C, Cyd) One of the four standard nucleosides used in RNA molecules, consisting of a cytosine base with its N9 nitrogen bonded to the C1 carbon of a ribose sugar. Cytosine bonded to deoxyribose is known as deoxycytidine, which is the version used in DNA.
== External links == Daintith, John (18 August 2008). Biographical Encyclopedia of Scientists (Third ed.). CRC Press. ISBN 978-1-4200-7272-3 – via Google Books. "Sidney W. Fox; Analyzed First Moon Rocks". 18 August 1998 – via LA Times. Fox, Sidney W.; Harada, Kaoru (1958). "Thermal Copolymerization of Amino Acids to a Product Resembling Protein". Science. 128 (3333): 1214. Bibcode:1958Sci...128.1214F. doi:10.1126/science.128.3333.1214. JSTOR 1756313. PMID 13592311. Fox, Sidney W. (1957). "The chemical problem of spontaneous generation". Journal of Chemical Education. 34 (10): 472. Bibcode:1957JChEd..34..472F. doi:10.1021/ed034p472.
=== Economic disruption === In 2017, the WannaCry and Petya (NotPetya) cyber attacks, masquerading as ransomware, caused large-scale disruptions in Ukraine as well as to the U.K.'s National Health Service, pharmaceutical giant Merck, Maersk shipping company and other organizations around the world. These attacks are also categorized as cybercrimes, specifically financial crime because they negatively affect a company or group.
=== Kh-Kn === Har Gobind Khorana (1922–2011). Indian-American biochemist at the University of Wisconsin, who participated in elucidating the genetic code. Nobel Prize for Physiology or Medicine (1968). Member Natl. Acad. Sci. USA. Ann Kimble-Hill (21st century). American biochemist studying structure-function relationships of membrane proteins and lipids Charles Glen King (1896–1988). American biochemist at the University of Pittsburgh. He isolated vitamin C, and was a pioneer in the field of nutrition research. Judith Klinman (b. 1941). American chemist, biochemist, and molecular biologist at UC Berkeley, known for her work on enzyme catalysis. Member Natl. Acad. Sci. USA. Aaron Klug FRS (President) (1926–2018). Lithuanian/South African/British structural biologist at Cambridge University. Nobel Prize in Chemistry (1982). Foreign associate Natl. Acad. Sci. USA. Franz Knoop (1875–1946). German biochemist at the University of Tübingen known for the discovery of β-oxidation. Jeremy Randall Knowles FRS (1935–2008). British and American biochemist at Oxford and Harvard, known for research on enzyme mechanisms. Foreign Associate Natl. Acad. Sci. USA.
Sources: en.wikipedia.org
American Association of Physical Anthropologists Biological Anthropology Section of the American Anthropological Association British Association of Biological Anthropologists and Osteoarchaeologists Canadian Association for Physical Anthropology Journals
=== Pacific islands === During an El Niño event, New Zealand tends to experience stronger or more frequent westerly winds during their summer, which leads to an elevated risk of drier than normal conditions along the east coast. There is more rain than usual though on New Zealand's West Coast, because of the barrier effect of the North Island mountain ranges and the Southern Alps. Fiji generally experiences drier than normal conditions during an El Niño, which can lead to drought becoming established over the Islands. However, the main impacts on the island nation is felt about a year after the event becomes established. Within the Samoan Islands, below average rainfall and higher than normal temperatures are recorded during El Niño events, which can lead to droughts and forest fires on the islands. Other impacts include a decrease in the sea level, possibility of coral bleaching in the marine environment and an increased risk of a tropical cyclone affecting Samoa. In the late winter and spring during El Niño events, drier than average conditions can be expected in Hawaii. On Guam during El Niño years, dry season precipitation averages below normal, but the probability of a tropical cyclone is more than triple what is normal, so extreme short duration rainfall events are possible. On American Samoa during El Niño events, precipitation averages about 10 percent above normal, while La Niña events are associated with precipitation averaging about 10 percent below normal.
This technology entails the joining of DNA from different species and the subsequent insertion of the hybrid DNA into a host cell. One of the first individuals to develop recombinant DNA technology was a biochemist at Stanford by the name of Paul Berg. In his experimental design in 1974, he cleaved (cut into fragments) the monkey virus SV40. He then cleaved the double helix of another virus, an antibacterial agent known as bacteriophage lambda. In the third step, he fastened DNA from the SV40 to DNA from the bacteriophage lambda. The final step involved placing the mutant genetic material into a laboratory strain of the E. coli bacterium. This last step, however, was not completed in the original experiment.
In addition, if a piece of wood is used for multiple purposes, there may be a significant delay between the felling of the tree and the final use in the context in which it is found. This is often referred to as the "old wood" problem. One example is the Bronze Age trackway at Withy Bed Copse, in England; the trackway was built from wood that had clearly been worked for other purposes before being re-used in the trackway. Another example is driftwood, which may be used as construction material. It is not always possible to recognize re-use. Other materials can present the same problem: for example, bitumen is known to have been used by some Neolithic communities to waterproof baskets; the bitumen's radiocarbon age will be greater than is measurable by the laboratory, regardless of the actual age of the context, so testing the basket material will give a misleading age if care is not taken. A separate issue, related to re-use, is that of lengthy use, or delayed deposition. For example, a wooden object that remains in use for a lengthy period will have an apparent age greater than the actual age of the context in which it is deposited.
Nonetheless, some genes may have helped modern East Asians adapt to the environment; the putatively Neanderthal Val92Met variant of the MC1R gene, which may be weakly associated with red hair and UV radiation sensitivity, is primarily found in East Asian, rather than European, individuals. Some genes related to the immune system appear to have been affected by introgression, which may have aided migration, such as OAS1, STAT2, TLR6, TLR1, TLR10, and several related to immune response. In addition, Neanderthal genes have also been implicated in the structure and function of the brain, keratin filaments, sugar metabolism, muscle contraction, body fat distribution, enamel thickness and oocyte meiosis. Nonetheless, a large portion of surviving introgression appears to be non-coding ("junk") DNA with few biological functions. A 2016 study indicated that human-Neanderthal gene variance may be involved in autism, with chromosome 16 section 16p11.2 deletions playing a large role. A 2017 study reported finding that the more Neanderthal DNA a person has in their genome, the more closely the brain of the individual would resemble that of a Neanderthal. The study also found that parts of the Neanderthal brain related to tool use and visual discrimination may have also experienced evolutionary or adaptational "trade-offs" with the "social brain", as also found in scientific studies on autism.
Sources: en.wikipedia.org
=== The Copa América final (1975) === The renamed and decentralised 1975 Copa América produced Colombia's first deep run in a continental tournament. Coached by Efraín Sánchez, the goalkeeper of the 1962 squad, Colombia won all four group matches against Paraguay and Ecuador, scoring seven and conceding one. In the semi-final they overwhelmed the defending champions Uruguay 3–0 at the Estadio El Campín through Edgar Angulo, Ortiz and Ernesto Díaz; the return at the Estadio Centenario finished 1–0 to Uruguay, whose Fernando Morena converted an early penalty before being sent off and whose team missed two further spot-kicks. With the sides level on points, Colombia advanced on goal difference. The final against Peru was the first in the competition's history to be decided over multiple legs. Ponciano Castro settled the opening match in Bogotá on 16 October with a long-range strike; Peru answered a week later at the Estadio Nacional in Lima, Juan Carlos Oblitas and Oswaldo Ramírez scoring inside the first half for a 2–0 win that levelled the tie on points and forced a decider on neutral ground. At the Estadio Olímpico in Caracas on 28 October, Hugo Sotil — flown in from Barcelona — scored the only goal before 30,000 spectators, and Peru claimed a second continental title. Ernesto Díaz finished as the tournament's joint leading scorer with four goals, a total that still ranks among the highest by a Colombian at the Copa América.
Benzene at The Periodic Table of Videos (University of Nottingham) International Chemical Safety Card 0015 USEPA Summary of Benzene Toxicity NIOSH Pocket Guide to Chemical Hazards Benzene from PubChem Dept. of Health and Human Services: TR-289: Toxicology and Carcinogenesis Studies of Benzene Video Recording of Sir John Cadogan giving a lecture on Benzene at the Royal Institution, 22 September 1991 Substance profile NLM Hazardous Substances Databank – Benzene
==== Natural resources ==== Initially, some mining executives feared that Castillo may nationalize mining, as he alluded during his electoral campaign. However, as of late, the Castillo Administration has toned down its rhetoric and showed greater willingness to work with private companies. Castillo has pledged to raise taxes on mining companies, and to make sure that projects are "socially profitable" for local mining communities. Prime Minister Guido Bellido has stated that he welcomes investment, as long as it means the development of the population. Later, the then prime minister stated that the energy sector should be under government control, while using the Camisea Gas Project as an example. In response, Economic Minister Pedro Francke ruled out expropriating the Camisea gas field. Francke also claimed that Bellido's call for government control of the energy sector was actually referring to state participation in the construction of a proposed natural gas pipeline, the Gran Gasoducto del Sur. However, PM Bellido later urged for the contract with the Camisea gas field to be renegotiated, threatening to nationalize the gas field if higher taxes aren't paid. The Prime Minister has also stated that strategic resources cannot remain in private hands. The Minister of Justice, Aníbal Torres, has stated that he's in favor of renegotiating the contract with Camisea, "like almost all the other ministers." However, Torres rejected the possibility of unilateral nationalization, and said that there were no talks about nationalization within the cabinet.
== Labeling of cells == How the labeling of RNA molecules is achieved depends on the model organism. For E.coli (bacteria) the minimum medium M9 can be used and supplemented with the stable isotope labeled variants of the needed salts. This enables labeling with 13C-carbon, 15N-nitrogen, 34S-sulfur and 2H-hydrogen. In S.cerevisiae (yeast) there are currently two possibilities: First, the use of commercially available complete growth medium, which enables labeling with 13C-carbon and/or 15N-nitrogen and second the use of minimal YNB medium which has to be supplemented with several amino acids and glucose which can be added as stable isotope labeled variants in order to achieve 13C-carbon, 15N-nitrogen and 2H-hydrogen labeling of RNA. While labeling in model organisms like E.coli and S.cerevisiae is fairly simple, stable isotope labeling in cell culture is much more challenging as the composition of the growth media is much more complex. Neither the supplementation of stable isotope labeled glucose nor the supplementation of stable isotope labeled variants of simple precursors of nucleoside biosynthesis such as glutamine and/or aspartate is sufficient for a defined mass increase higher than 2 Da. Instead, most cells kept in cell culture can be fed with stable isotope labeled methionine for labeling of methyl groups and with stable isotope labeled variants of adenin and uridine for labeling of the nucleoside's base body.
Sources: en.wikipedia.org
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
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.