If you have been reading about freeze-thaw 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.
Last reviewed on 2026-06-07. Where a claim depends on a specific study, the study is described rather than over-claimed.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
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.
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.
The measles vaccine is equally effective for preventing measles in all formulations, but side effects vary for different combinations. The World Health Organization (WHO) recommends measles vaccine be given at nine months of age in areas of the world where the disease is common, or at twelve months where the disease is not common. Measles vaccine is based on a live but weakened strain of measles. It comes as a dried powder that is mixed with a specific liquid before being injected either just under the skin or into a muscle. Verification that the vaccine was effective can be determined by blood tests. The measles vaccine was first introduced in 1963. In that year, the Edmonston-B strain of measles virus was turned into a vaccine by John Enders and colleagues and licensed in the United States. In 1968, an improved and even weaker measles vaccine was developed by Maurice Hilleman and colleagues, and began to be distributed, becoming the only measles vaccine used in the United States since 1968. About 86% of children globally had received at least one dose of the vaccine as of 2018. In 2021, at least 183 countries provided two doses in their routine immunization schedule. It is on the World Health Organization's List of Essential Medicines. As outbreaks easily occur in under-vaccinated populations, non-prevalence of disease is seen as a test of sufficient vaccination within a population.
These fears of subversive Peruvians were also fueled by the widely publicized kidnapping, together with the collection of a ransom of 1,000,000 dollars, of the Bolivian businessman and politician Samuel Doria Medina; a fact that was carried out by Peruvians (also classified as subversives) members of the Tupac Amaru Revolutionary Movement (MRTA). All of which were events that generated a very bad reputation for Peruvians among Bolivian society, being incited by said prejudices and stereotypes by the morbidity of the press. Despite everything, Bolivian institutions report that, in the prison population of in that country, it is not a reality that the number of Peruvian prisoners is proportionally greater than the Bolivian citizens sentenced to prison. The Commission for Human Rights and Pacification of the Congress of the Republic of Peru has come to examine multiple cases of aggressions and mistreatment in Bolivia, against Peruvian citizens, including Congresswoman Susana Díaz, after a trip to Bolivia, verified the excesses committed against Peruvian groups, coming to denounce that there is an "anti-Peruvian phobia", especially in the Desaguadero.
=== Mechanical debridement === When removal of tissue is necessary for the treatment of wounds, hydrotherapy which performs selective mechanical debridement can be used. Examples of this include directed wound irrigation and therapeutic irrigation with suction. Baths with whirlpool water flow should not be used to manage wounds because a whirlpool will not selectively target the tissue to be removed and can damage all tissue. Whirlpools also create an unwanted risk of bacterial infection, can damage fragile body tissue, and in the case of treating arms and legs, bring risk of complications from edema. Hydrosurgery uses a high‐pressure, water‐based jet system to remove burnt skin. This should leave behind the unburned, healthy skin. A 2019 Cochrane systematic review aimed to find out if burns treated with hydrosurgery heal more quickly and with fewer infections than burns treated with a knife. The review authors only found one randomised controlled trial (RCT) with very low certainty evidence that investigated this. Based on this trial, they concluded that it is uncertain whether or not hydrosurgery is better than conventional surgery for early treatment of mid‐depth burns. More RCTs are needed to fully answer this question. Allowing a dressing to proceed from moist to dry, then manually removing the dressing causes a form of non-selective debridement. This method works best on wounds with moderate amounts of necrotic debris (e.g. "dead tissue").
==== Silver ion tablets ==== An alternative to iodine-based preparations in some usage scenarios are silver ion/chlorine dioxide-based tablets or droplets. These solutions may disinfect water more effectively than iodine-based techniques while leaving hardly any noticeable taste in the water in some usage scenarios. Silver ion/chlorine dioxide-based disinfecting agents will kill Cryptosporidium and Giardia, if utilized correctly. The primary disadvantage of silver ion/chlorine dioxide-based techniques is the long purification times (generally 30 minutes to 4 hours, depending on the formulation used). Another concern is the possible deposition and accumulation of silver compounds in various body tissues leading to a rare condition called argyria that results in a permanent, disfiguring, bluish-gray pigmentation of the skin, eyes, and mucous membranes.
Sources: en.wikipedia.org
She donated the entirety of the prize money towards the creation of scholarships to assist women, underrepresented minorities and refugees who are pursuing the study of physics. 2018: Canadian physicist Donna Strickland received the Nobel Prize in Physics "for groundbreaking inventions in the field of laser physics"; she shared it with Arthur Ashkin and Gérard Mourou. 2018: New Zealand chemist Juliet Gerrard was appointed as the Prime Minister's Chief Science Advisor in the administration of Jacinda Ardern, the first time a woman was appointed to the role. 2018: American chemist Frances Arnold received the Nobel Prize in Chemistry "for the directed evolution of enzymes"; she shared it with George Smith and Gregory Winter, who received it "for the phage display of peptides and antibodies". This made Frances the first American woman to receive the Nobel Prize in Chemistry. 2018: For the first time in history, women received the Nobel Prize in Chemistry and the Nobel Prize in Physics in the same year. 2019: NASA astronauts Christina Koch and Jessica Meir complete the first ever all-female spacewalk outside the International Space Station (ISS) replacing a failed power control unit. 2019: American Mathematician Karen Uhlenbeck became the first woman to win the Abel Prize for "her pioneering achievements in geometric partial differential equations, gauge theory, and integrable systems, and for the fundamental impact of her work on analysis, geometry and mathematical physics".
(1914–2006), American physicist and chemist who won the 2002 Nobel Prize in Physics for detecting neutrinos emitted from the Sun Humphry Davy (1778–1829), British chemist, discovered several alkaline earth metals Serena DeBeer (born 1973), American chemist known for developing X-ray based spectroscopic probes of electronic structure Peter Debye (1884–1966), Dutch chemist who improved the theory of electrical conductivity in electrolyte solutions, winner of the 1936 Nobel Prize in Chemistry Johann Deisenhofer (born 1943), German biochemist who determined the three-dimensional structure of a protein complex found in photosynthetic bacteria, 1988 Nobel Prize in Chemistry Margarita del Val (born 1959), Spanish chemist, immunologist, and virologist, coordinator of the Salud Global ("Global Health") platform Nathalie Demassieux (1884–1961), French mineral chemist and academic who worked on the complex halogenated salts of lead Gautam Radhakrishna Desiraju (born 1952), Indian chemist known for work on crystal engineering and weak hydrogen bonds James Dewar (1842–1923), British chemist and physicist known for his invention of the vacuum flask and its usefor studying the liquefaction of gases François Diederich (1952–2020), Luxembourg chemist known for molecular recognition studies with biological receptors Otto Diels (1876–1954), German chemist, winner of the 1950 Nobel Prize in Chemistry for the Diels–Alder reaction, a method for cyclohexene synthesis Robert Dirks (1978–2015), American computational chemist known for work on DNA nanotechnology
The epithelium is the innermost layer. It is where most digestive, absorptive and secretory processes occur. The lamina propria, the underlying layer of loose connective tissue within the mucosa. The muscularis mucosae, a thin layer of smooth muscle. The epithelium, the most exposed part of the mucosa, is a glandular epithelium with many goblet cells. Goblet cells secrete mucus, which lubricates the passage of food along and protects the intestinal wall from digestive enzymes. In the small intestine, villi are folds of the mucosa that increase the surface area of the intestine. The villi contain a lacteal, a vessel connected to the lymph system that aids in the removal of lipids and tissue fluids. Microvilli are present on the epithelium of a villus and further increase the surface area over which absorption can take place. Numerous intestinal glands as pocket-like invaginations are present in the underlying tissue. In the large intestines, villi are absent and a flat surface with thousands of glands is observed. Underlying the epithelium is the lamina propria, which contains myofibroblasts, blood vessels, nerves, and several different immune cells, and the muscularis mucosa which is a layer of smooth muscle that aids in the action of continued peristalsis and catastalsis along the gut.
=== As a feed additive === Guanidinoacetic acid is a nutritional feed additive approved by the European Commission for chickens for fattening, weaned piglets and pigs for fattening. It is supposed to lead with a "vegetarian diet" (meaning without feeding of animal protein) to higher feed conversion, higher weight gain and improved muscle increase already at a low dosage (600 g/to feed). Possible benefits of glycocyamine supplementation can not yet be conclusively assessed, neither in other breeding, fattening and domestic animals nor for high-performance athletes, analogous to the glycocyamine metabolite creatine. The simultaneous intake of methyl providing substances such as betaine appears advisable because of the risk of homocysteine formation with glycocyamine alone.
Shikimate Dehydrogenase catalyzes the reversible NADPH-dependent reaction of 3-dehydroshikimate to shikimate. The enzyme reduces the carbon-oxygen double bond of a carbonyl functional group to a hydroxyl (OH) group, producing the shikimate anion. The reaction is NADPH dependent with NADPH being oxidised to NADP+.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.