GABA-A receptor raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-08-20. Anything still debated is marked as such rather than presented as settled.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
| Property | Value | Notes |
|---|---|---|
| Typical purity report | 95% or higher by HPLC | Area percentage at 214 nm |
| Identity confirmation | Mass spectrometry | Electrospray or MALDI |
| Powder storage | -20 C, desiccated | Protect from light |
| Solution storage | 2-8 C short term | Freeze aliquots for longer |
| Quality document | Certificate of analysis | States method and value |
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
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.
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.
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.
=== Notable alumni === Keith Barry, performing artist Fiona Everard, national champion runner Ethna Gaffney, first female professor at the Royal College of Surgeons in Ireland Michael D. Higgins, 9th President of Ireland Catherine Connolly, 10th President of Ireland Enda Kenny, former Taoiseach Aifric Keogh and Fiona Murtagh Olympic bronze medalists Tokyo 2020 Mark Heslin, judge of the High Court Máire Whelan, former Attorney General and current judge of the Court of Appeal Breandán Ó hEithir, writer and author Pat McGrath, news correspondent Wilfrid Napier O.F.M., Cardinal, Archbishop of Durban Conor Pope, journalist Gráinne Seoige, former news anchor and television presenter Martin Sheen, actor Nicola Coughlan, actor Rónán Mullen, Irish senator representing National University of Ireland (constituency) Enya (honorary doctorate) Heather Humphreys, Fine Gael politician Donogh O'Malley, Fianna Fáil politician Bobby Molloy, Fianna Fáil politician Frank Fahey (politician) Pat Rabbitte, former Irish Labour Party leader Séamus Brennan, former Irish government minister Alfred Keogh, former Director-General of the British Army Medical Services during the First World War. Brian McManus, host of the YouTube channel Real Engineering
SCl2 + Cl2 → SCl4 It melts with simultaneous decomposition above −20 °C. Its solid structure is uncertain. It is probably the salt SCl3+Cl−, since related salts are known with noncoordinating anions. In contrast to this tetrachloride, SF4 is a neutral molecule.
==== Earth sciences ==== In Earth sciences, particularly in geomorphology, in situ refers to natural materials or processes occurring at their point of origin without being transported. An example is weathering, in which rocks undergo physical or chemical disintegration in place, in contrast to erosion, which involves the removal and relocation of materials by agents such as wind, water, or ice. Soil formed from the weathering of underlying bedrock is an example of an in situ formation. In situ measurements, such as those of soil moisture, rock stress, groundwater trends, or radiation levels, are conducted on-site to provide direct data. These measurements are often essential for validating remote sensing data, such as satellite imagery, which is widely used for large-scale environmental monitoring but may require in situ confirmation to ensure accuracy.
Sources: en.wikipedia.org
The Australian National University Act received royal assent on 1 August 1946. The act created the Australian National University (ANU), and gave the medical research institute the name "John Curtin School of Medical Research". H. C. "Nugget" Coombs, an economist and head of the Department of Post-War Reconstruction, accompanied the Prime Minister, Ben Chifley, on an official visit to the UK as his principal advisor. Coombs met with Florey in Oxford in May 1946. They agreed that the success of the new university would depend on the quality of faculty they could attract, and he wanted four eminent scholars to lead the four research schools: Florey for medicine, Mark Oliphant for physics, Keith Hancock for history, and Raymond William Firth for Pacific studies. Each received an official invitation in April 1947, and they were invited to come to Canberra for consultation in December 1947 and January 1948. They would constitute an academic advisory committee, for which they would be paid £250 (equivalent to A$20,242 in 2022) plus £200 (equivalent to A$16,193 in 2022) expenses per annum. Since they were all located in the UK, a London office of the university was opened to provide liaison. Florey never moved to Canberra, but he did accept the position of acting director of the John Curtin School of Medical Research for a five-year term commencing in May 1948 in order to establish it. Brian Lewis had been appointed university architect, but Florey hired Stephen Welsh, the professor of architecture at Sheffield University.
== Protactinium-233 == Protactinium-233 is also part of the thorium fuel cycle. It is an intermediate beta decay product between thorium-233 (produced from natural thorium-232 by neutron capture) and uranium-233 (the fissile fuel of the thorium cycle). Some thorium-cycle reactor designs try to protect 233Pa from further neutron capture producing 234Pa and 234U, which are not useful as fuel.
Azeliragon vTv Therapeutics (formerly TransTech Pharma) sponsored a Phase 3 clinical trial of their RAGE inhibitor Azeliragon (TTP488) for mild Alzheimer's disease. These trials were halted in 2018. RAP (Receptor Antagonist Peptide) RAP is a peptide-based inhibitor that functions by directly competing with RAGE ligands for binding, thereby inhibiting RAGE-mediated signaling. It has shown potential in reducing vascular inflammation and preventing atherosclerosis in experimental models. RAP's ability to block the RAGE-ligand interaction has made it a candidate for cardiovascular disease therapies, particularly those involving chronic inflammation. FPS-ZM1 FPS-ZM1 is a well-known small molecule inhibitor of RAGE, designed to cross the blood-brain barrier and effectively block RAGE signaling in the central nervous system. Studies have demonstrated that FPS-ZM1 significantly reduces neuroinflammation and β-amyloid accumulation in mouse models of Alzheimer's disease. By inhibiting RAGE, FPS-ZM1 aims to reduce oxidative stress and inflammation associated with neurodegenerative processes, showing promise in preclinical studies for treating Alzheimer's disease and other neuroinflammatory conditions.
Sources: en.wikipedia.org
Purity is usually reported as an HPLC area percentage, most often measured at 214 nm. Identity is confirmed separately by mass spectrometry. A certificate of analysis should state both the method and the observed value.
Dry powder is kept frozen, desiccated, and shielded from light. Dissolved material is aliquoted and frozen to limit freeze-thaw cycles. Short-term refrigerated storage is common for working solutions.
Russia registers it as a prescription nasal product. Most other markets classify it as a research chemical with no approved medical use. Oversight of purity and labeling is consequently minimal in those markets.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.