Everything below concerns heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-11-20. Numbers and descriptions here follow the published literature rather than marketing material.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
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.
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 |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Analog of the tetrapeptide tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Reported consistently across pharmacopoeial descriptions |
| Appearance | White to off-white lyophilized powder | Typical form of research-grade material |
| Solubility | Freely soluble in water | Aqueous buffers; poor in nonpolar solvents |
| Typical storage temperature | -20 degrees Celsius | Lyophilized powder; protect from moisture |
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.
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.
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.
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.
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.
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.
Reflecting his left-wing views, Peukert praised "our red grandfathers" who chose to oppose National Socialism, despite their downtrodden status, arguing that their willingness to take action when so many were passive or supportive of National Socialism, made them heroes. Peukert's PhD thesis, published in 1980, was Die KPD im Widerstand Verfolgung und Untergrundarbeit am Rhein und Ruhr, 1933–1945 (The KPD in the Resistance Persecution and Underground work in the Rhine and the Ruhr 1933–1945). Peukert's work went beyond what the title of his PhD dissertation would suggest, as he examined the ideological motivation, organizational structure of the underground Communist Party, and the motivation and social background of a single individual Communist in the Ruhr and Rhineland convicted by German courts of belonging to the KPD. Peukert's work on the Communist resistance led him to engage in many bitter, polemical disputes with his former associates in the Communist Party who did not like his conclusions. From the right, criticism of Die KPD im Widerstand Verfolgung und Untergrundarbeit am Rhein und Ruhr, 1933-1945 came from the American historian Albert Lindemann who complained that Peukert's focus on Communist resistance in the Rhineland and Ruhr regions did not merit a 460-page long book, though Lindemann wrote that wrote the book was not "an exercise in hagiography" and praised Peukert for his "critical remarks" about East German historiography.
Often described as a de facto one-party state because of its uncommon longevity for a nominal liberal democracy, some activists and opposition politicians view the PAP government's tight regulation of political and media activities, along with its stringent laws, as an infringement on political rights. In response, the PAP introduced several significant political changes, including the creation of the Non-constituency Members of Parliament (NCMPs) scheme from the 1984 election, which allowed a limited number of the best performing losing opposition candidates to be appointed as MPs. Group representation constituencies (GRCs) were subsequently introduced in the 1988 election as multi-member electoral divisions intended to guarantee minority representation in parliament, although the opposition has accused the scheme of enabling gerrymandering. In addition, Nominated Members of Parliament (NMPs) were introduced in 1990 to allow non-elected and non-partisan representatives from diverse professional fields to serve in parliament. The constitution was amended in 1991 to provide for an elected president with veto powers over the use of past reserves and key public service appointments. The first such election was held in 1993. In 1990, Goh Chok Tong succeeded Lee and became Singapore's second prime minister, leading the PAP into the 1991 election. During Goh's tenure, the country went through the 1997 Asian financial crisis and the 2002–2004 SARS outbreak. In 2004, Lee Hsien Loong, the eldest son of Lee Kuan Yew, became the country's third prime minister.
===== Immune barrier ===== The surface area of the digestive tract is estimated to be about 32 square meters, or about half a badminton court. With such a large exposure (more than fifteen times larger than the exposed surface of the skin), critical immune components function to prevent pathogens from entering the blood and lymph circulatory systems. Fundamental components of this protection are provided by the intestinal mucosal barrier, which is composed of physical, biochemical, and immune elements elaborated by the intestinal mucosa. Microorganisms also are kept at bay by an extensive immune system comprising the gut-associated lymphoid tissue (GALT). There are additional factors contributing to protection from pathogen invasion. For example, low pH (ranging from 1 to 4) of the stomach is fatal for many microorganisms that enter it. Similarly, mucus (containing IgA antibodies) neutralizes many pathogenic microorganisms. Other factors in the GI tract contributing to immune function include enzymes secreted in the saliva and bile.
The median lethal dose (LD50) of a venom is the dose required to kill half the members of a tested population after a specified test duration. A lower LD50 number indicates increased toxicity. There are four methods for administering the LD50 test: Subcutaneous: Venom is injected into the fatty layer beneath the skin. Intravenous: Venom is injected directly into a vein. Intramuscular: Venom is injected into a muscle. Intraperitoneal: Venom is injected into the abdominal cavity. The most commonly tested methods are subcutaneous and intravenous injections, using mice. Subcutaneous is the most applicable to actual bites: Only large Bitis or extremely large Bothrops or Crotalus specimens are able to deliver a bite that is truly intramuscular, and intravenous injections are extremely rare in actual bites. Mixing dry venom with 0.1% bovine serum albumin in saline gives more consistent test results than mixing with saline alone. Wayne C Hodgson et al. stated in 2002: "Historically, the lethality of snake venoms has been based on murine LD50 studies. Due to ethical reasons, these studies are being superseded by in vitro studies. Instead, the time taken to produce 90% inhibition of nerve-mediated twitches (i.e. t90) in skeletal muscle preparations can be determined".
Sources: en.wikipedia.org
=== Sulfonating agent === Sulfur trioxide is a potent sulfonating agent, i.e. it adds SO3 groups to substrates. Often the substrates are organic, as in aromatic sulfonation. For activated substrates, Lewis base adducts of sulfur trioxide are effective sulfonating agents.
=== Legal status === In December 2016, a new drug application was filed with the US Food and Drug Administration (FDA), and in October 2017, an FDA advisory committee approved it unanimously. In December 2017, the injectable version with the brand name Ozempic was approved in the US for use by people with diabetes, and, in January 2018, in Canada. In February 2018, authorization was granted in the European Union, in March 2018 in Japan, and in August 2019 in Australia. A version of semaglutide to treat diabetes that can be taken orally (Rybelsus) was approved for medical use in the US in September 2019, and in the European Union in April 2020. In January 2023, the US FDA prescription label for Rybelsus was updated to reflect that it can be used as a first-line treatment for adults with type 2 diabetes. In June 2021, a higher-dose version for injectable use, sold under the brand name Wegovy, was approved by the FDA as an anti-obesity medication for long-term weight management in adults. In January 2022, Wegovy was approved for medical use in the European Union. In December 2025, an oral version of semaglutide, sold under the brand name Wegovy, was approved in the US for weight management. In March 2026, the CHMP recommended granting a conditional marketing authorization for Kayshild (semaglutide), a GLP-1 receptor agonist for the treatment of non-cirrhotic metabolic dysfunction-associated steatohepatitis (MASH) with liver fibrosis, a serious disease where fat deposits accumulate in the liver causing inflammation.
The predicted half-lives for these nuclides often greatly exceed the estimated age of the universe, and in fact, there are also 31 known radionuclides (see primordial nuclide) with half-lives longer than the age of the universe. The total of all known nuclides, of which most have been created only artificially, is several thousand, of which 987 are stable or have a half-life longer than one hour; see List of nuclides.
Sources: en.wikipedia.org
== Cause == The cause of lipedema is still unknown. There are various hypotheses about its pathophysiology, including altered adipogenesis, microangiopathy, and damage to the lymphatic system disturbing its microcirculation. Lipedema has been described in familial clusters, suggesting a genetic component. It often appears around times of hormonal change such as puberty, pregnancy, and menopause, suggesting a potential hormonal component. Having obesity does not cause lipedema, but more than half of people with the condition have a BMI higher than 35.
There is broad scientific consensus that the acids DHA and EPA (both of which are highly prevalent in seafood) are beneficial to neurodevelopment and cognition, especially at young ages. The United Nations' Food and Agriculture Organization has described fish as "nature's superfood". Seafood consumption is associated with improved neurodevelopment during pregnancy and early childhood. Fish consumption is associated with a decreased risk of dementia, lung cancer, and stroke, as well as a more tenuous link to reduced mortality from coronary heart disease. A 2020 umbrella review concluded that fish consumption reduces all-cause mortality, cancer, cardiovascular disease, stroke, and other outcomes, while suggesting that two to four servings per week is generally safe. However, two other umbrella reviews found no statistically significant association between fish consumption and cancer risks, and have cautioned researchers when it comes to interpreting this reported association as the quality of evidence is low. The parts of fish containing essential fats and micronutrients, often cited as the primary health benefits of eating seafood, are frequently discarded in the developed world. Micronutrients including calcium, iodine, potassium, selenium, and zinc are found in their highest concentrations in the head, intestines, bones, and scales of fish. Government recommendations promote moderate consumption of fish.
=== Historical background === Cryobiology history can be traced back to antiquity. As early as in 2500 BC, low temperatures were used in Egypt in medicine. The use of cold was recommended by Hippocrates to stop bleeding and swelling. With the emergence of modern science, Robert Boyle studied the effects of low temperatures on animals. In 1949, bull semen was cryopreserved for the first time by a team of scientists led by Christopher Polge. This led to a much wider use of cryopreservation today, with many organs, tissues and cells routinely stored at low temperatures. Large organs such as hearts are usually stored and transported, for short times only, at cool but not freezing temperatures for transplantation. Cell suspensions (like blood and semen) and thin tissue sections can sometimes be stored almost indefinitely in liquid nitrogen temperature (cryopreservation). Human sperm, eggs, and embryos are routinely stored in fertility research and treatments. Controlled-rate and slow freezing are well established techniques pioneered in the early 1970s which enabled the first human embryo frozen birth (Zoe Leyland) in 1984. Since then, machines that freeze biological samples using programmable steps, or controlled rates, have been used all over the world for human, animal, and cell biology – 'freezing down' a sample to better preserve it for eventual thawing, before it is deep frozen, or cryopreserved, in liquid nitrogen.
The first instance of a pathogenic NAA20 variant were two siblings with a Met54Val missense mutation and three siblings with a homozygous missense variant Ala80Val, and the second instance was about two siblings with a Gln34Ter/Leu4Pro biallelic mutation. The common effect of these mutations is that there is weaker binding of NAA20 to NAA25, thereby reducing the capacity of the NatB complex to add an acetyl group to a target protein. There are some slight differences in the clinical symptoms in the seven patients, the main one is that the patients with either Met54Val or Ala80Val mutation had decreased head circumference, a condition known as microcephaly. The common symptoms in all seven patients are various forms of developmental delay in form of speech impairment, walking disabilities and changes in facial features. Which proteins are affected and could cause the pathogenic symptoms is to date not known and must be further studied, since the effect of NAA20 loss of function is quite impactful to the patients' health and quality of life.
Sources: en.wikipedia.org
Selank is a synthetic seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.
The first four residues of Selank reproduce the tuftsin sequence Thr-Lys-Pro-Arg. A Pro-Gly-Pro extension at the C-terminus was added to slow enzymatic breakdown and extend residence time.
It holds marketing authorization in Russia, where nasal drop formulations are sold. No equivalent approval exists in the European Union, the United States, or most other countries.
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.