If you have been reading about freeze-thaw cycle 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.
Updated 2026-02-23. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Also in aqueous buffers |
| Typical purity (HPLC) | 95 percent or higher | Lot-dependent |
| Dry powder storage | Minus 20 degrees Celsius | Sealed, dry, protected from light |
| Solution storage | 2 to 8 degrees Celsius | Short-term use |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF |
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.
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.
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.
== Molecular properties and chemical space of peptides == The chemical space of peptides is defined as a multidimensional landscape shaped by molecular descriptors or fingerprints. Within these frameworks, the distance between specific molecules serves as a proxy for chemical or functional similarity. This space can be mapped using primary amino acid sequences, three-dimensional structural data, or a combination of both. Key molecular properties used for mapping include molecular weight, lipophilicity (logP and logD), topological polar surface area (TPSA), and hydrogen-bond dynamics. Dimensionality-reduction techniques—such as Principal Component Analysis (PCA), t-SNE, and UMAP—are frequently employed alongside clustering algorithms to visualize peptide libraries and identify clusters with related biological activities. Peptides are distinguished from traditional small molecules by their unique combination of residue sequence, amide backbone flexibility, and susceptibility to chemical modifications, all of which dictate bioavailability and membrane permeability. Computational analysis is supported by notation systems like FASTA, HELM, and BILN for encoding both canonical and modified sequences. Modifications such as cyclization or the integration of non-natural amino acids significantly shift a peptide's position within the chemical space, altering its stability and target affinity. Consequently, chemical-space analysis is a vital tool for virtual screening and the discovery of shared bioactivity regions across different peptide families.
Barker countersued for slander, but Hallstrom prevailed, receiving a settlement in 2005. Though she was not required to sign a non-disclosure agreement, she limited her comments about Barker until after his death, fearing retribution from him. In October 2007, Deborah Curling, a CBS employee assigned to The Price Is Right, filed a lawsuit against CBS, Bob Barker, and The Price Is Right producers, claiming that she was forced to quit her job after testifying against Barker in a wrongful-termination lawsuit brought by a previous show producer. Curling claimed that she was demoted to an "intolerable work environment" backstage, which caused her to leave the job. Curling, who is black, also alleged that the show's producers, including Barker, created a hostile work environment in which black employees and contestants were discriminated against. A few months later, Barker was removed from the lawsuit, and in September 2009, the lawsuit was dismissed. Curling's attorney stated that he planned to appeal the dismissal of the lawsuit. In January 2012, the California Court of Appeals affirmed the dismissal.
=== Fats, minerals and proteins === Are produced when collagen proteins are manufactured. The main areas of application for Fat, Mineral and Protein Ingredients are human food, pet food and animal feed. The fats, for example, serve as energy sources. Proteins can improve the texture and hence the enjoyability and digestibility of foodstuffs and animal feed. Further applications are in technical areas and are used in the manufacture of bone china, construction molds, lubricants for machines and anti-rust agents.
The level was initially called "Traptown" or "phystown" in the game's files during an early E3 demo of Half-Life 2, referencing the numerous booby traps scattered through it. Datamined information by fans showed that an early build featured Combine forces in the level in addition to headcrabs and zombies, and the "mining town" aspect of Ravenholm was much more prominent, including allowing the player to control a large excavator. The original version of Ravenholm may have also been set chronologically before the player arrived at Black Mesa East and acquired the gravity gun. The weapon ultimately ended up defining the level, encouraging the player to kill zombies using saw blades and other tools as an alternative to using the player's weapons. Players who possessed shared knowledge of zombie-based fiction such as The Zombie Survival Guide could also instinctively guess that the objects able to be picked up by the gravity gun could be used in an offensive manner. Level designer Dario Casali stated that Ravenholm was conceived as a "sanctuary gone bad", where the player went expecting help from potential allies, but realized they had all turned into enemies. Casali further stated that the town was designed to both appear isolated to the point where it could have believably escaped Combine notice for a time while simultaneously match the game's other levels, describing this as a challenge.
Nuclear enrichment has been considered a component of Iranian national development plans since the Shah's regime, when the first nuclear program was developed. Iran retained its nuclear program after the 1979 revolution, and has long denied seeking nuclear weapons, saying its enrichment efforts were to generate nuclear power for civilian use. Despite Iran's compliance with the JCPOA, Trump withdrew the US from the deal in 2018, re-imposed sanctions, and adopted a "maximum pressure" strategy. The Biden administration kept most of these sanctions, further damaging Iran's economy. Trump continued the "maximum pressure" approach in his second term. In September 2025, the UN reimposed sanctions on Iran using the "snapback" mechanism, causing the currency to weaken, resulting in price increases for food supplies such as meat, rice, and other staples, freezing Iranian assets abroad, suspending arms transactions, and imposing penalties related to the country's ballistic-missile programme. Treasury Secretary Scott Bessent labeled the collapse of the Iranian currency in December 2025 as the strategy's "grand culmination". At his State of the Union Address in February 2026, Trump claimed Iran had restarted its nuclear program and was developing missiles capable of striking the US. Trump's claims contradicted his previous claims that Iran's nuclear program was "obliterated" and US intelligence reports that Iran did not pose any threat towards the US, and needed until 2035 to build such missiles to do so.
Sources: en.wikipedia.org
Drew went to New York City as the medical director of the United States' Blood for Britain project, a project to aid British soldiers and civilians by giving U.S. blood to the United Kingdom. It was here that Drew helped set the standard for other hospitals donating blood plasma to Britain by ensuring clean transfusions along with proper aseptic technique to ensure viable plasma dispersals were sent to Britain. Drew created a central location for the blood collection process where donors could go to give blood. He made sure all blood plasma was tested before it was shipped out. He ensured that only skilled personnel handled blood plasma to avoid the possibility of contamination. The Blood for Britain program operated successfully for five months, with total collections of almost 15,000 people donating blood, and with over 5,500 vials of blood plasma.
=== Circulation === The octopus has three hearts, one main two-chambered heart charged with sending oxygenated blood to the body and two smaller branchial hearts, one next to each set of gills. The circulatory circuit sends oxygenated blood from the gills to the atrium of the systemic heart, then to its ventricle which pumps this blood to the rest of the body. Deoxygenated blood from the body goes to the branchial hearts which pump the blood across the gills to oxygenate it, and then the blood flows back to the systemic atrium for the process to begin again. Three aortae leave the systemic heart, two minor ones (the abdominal aorta and the gonadal aorta) and one major one, the dorsal aorta which services most of the body. The octopus also has large blood sinuses around its gut and behind its eyes that function as reserves in times of physiologic stress. The octopus' heart rate does not change significantly with exercise, though temporary cardiac arrest of the systemic heart can be induced by oxygen debt, almost any sudden stimulus, or mantle pressure during jet propulsion. Its only compensation for exertion is through an increase in stroke volume of up to three times by the systemic heart, which means it suffers an oxygen debt with almost any rapid movement. The octopus is, however, able to control how much oxygen it pulls out of the water with each breath using receptors on its gills, allowing it to keep its oxygen uptake constant over a range of oxygen pressures in the surrounding water.
While the later Stalinist period was characterized by the restriction of creativity and architectural innovation, the earlier post-revolutionary years saw many radical buildings created in the city. Particularly notable were the constructivist architects associated with VKHUTEMAS (the Russian state's art and technical school), responsible for such landmarks as Lenin's Mausoleum. Another prominent architect was Vladimir Shukhov, famous for Shukhov Tower, one of many hyperboloid towers that he designed. This one was built between 1919 and 1922 as a transmission tower for a Russian broadcasting company. Shukhov left an enduring legacy in the constructivist architecture of early Soviet Russia. He designed shop galleries, notably the GUM department store on Red Square, which was bridged with innovative metal-and-glass vaults.
Acupuncture practitioners should know, and be prepared to be responsible for, any substantial harm from treatments. Some acupuncture proponents argue that the long history of acupuncture suggests it is safe. However, there is an increasing literature on adverse events (e.g. spinal-cord injury). Acupuncture seems to be safe in people getting anticoagulants, assuming needles are used at the correct location and depth, but studies are required to verify these findings.
TATP has been used in bomb and suicide attacks and in improvised explosive devices, including the London bombings on 7 July 2005, where four suicide bombers killed 52 people and injured more than 700. It was one of the explosives used by the "shoe bomber" Richard Reid in his 2001 failed shoe bomb attempt and was used by the suicide bombers in the November 2015 Paris attacks, 2016 Brussels bombings, Manchester Arena bombing, June 2017 Brussels attack, Parsons Green bombing, the Surabaya bombings, and the 2019 Sri Lanka Easter bombings. Hong Kong police claim to have found 2 kg (4.4 lb) of TATP among weapons and protest materials in July 2019, when mass protests were taking place against a proposed law allowing extradition to mainland China. TATP shockwave overpressure is 70% of that for TNT, and the positive phase impulse is 55% of the TNT equivalent. TATP at 0.4 g/cm3 has about one-third of the brisance of TNT at 1.2 g/cm3 as measured by the Hess test. TATP is attractive to terrorists because it is easily prepared from readily available retail ingredients like hair bleach and nail polish remover. It was also able to evade detection because it is one of the few high explosives which does not contain nitrogen, and could therefore pass undetected through standard explosive detection scanners, which were hitherto designed to detect nitrogenous explosives. By 2016, explosives detectors had been modified to be able to detect TATP, and new types were developed.
Sources: en.wikipedia.org
As such, the yeasts involved in what has been typically called top-cropping or top-fermenting ale may be both Saccharomyces cerevisiae and complex hybrids of Saccharomyces cerevisiae and Saccharomyces kudriavzevii. Three notable ales, Chimay, Orval and Westmalle, are fermented with these hybrid strains, which are identical to wine yeasts from Switzerland.
Dihydroxyphenylalanine ammonia-lyase was presumed to use 3,4-dihydroxy-L-phenylalanine (L-DOPA) to produce trans-caffeate and NH3. However, the EC number for this purported enzyme was deleted in 2007, as no evidence has emerged for its existence.
East Malaysia, on the island of Borneo, has a coastline of 2,607 km (1,620 mi). It is divided between coastal regions, hills and valleys, and a mountainous interior. The Crocker Range extends northwards from Sarawak, dividing the state of Sabah. It is the location of the 4,095 m (13,435 ft) high Mount Kinabalu, the tallest mountain in Malaysia. Mount Kinabalu is located in the Kinabalu National Park, which is protected as one of the four UNESCO World Heritage Sites in Malaysia. The highest mountain ranges form the border between Malaysia and Indonesia. Sarawak contains the Mulu Caves, the largest cave system in the world, in the Gunung Mulu National Park, another World Heritage Site. Also in Sarawak is the Rajang, the largest river in Malaysia. Around the two halves of Malaysia are numerous islands, the largest of which is Banggi. The local climate is equatorial and characterised by the annual southwest (April to October) and northeast (October to February) monsoons. The temperature is moderated by the presence of the surrounding oceans. Humidity is usually high, and the average annual rainfall is 250 cm (98 in). The climates of the Peninsula and the East differ, as the climate on the peninsula is directly affected by wind from the mainland, as opposed to the more maritime weather of the East. Local climates can be divided into three regions, highland, lowland, and coastal. Climate change will cause sea level rise and increased rainfall, increasing flood risks and leading to droughts.
If the amine nitrogen is instead fully substituted, then the next proton to leave is α to the double-bonded carbon, restoring conventional carbonyl polarity. As such, the amine nitrogen is a convenient location for a chiral auxiliary. This idea is the Enders SAMP/RAMP alkylation and its descendants. Hydrolysis, which would require another umpolung, is generally a difficult reaction for hydrazones. Nevertheless, alkyl hydrazones are 102- to 103-fold more susceptible to hydrolysis than analogous oximes. The reaction can be performed reliably with BiCl3 acid catalysis. Alternatively, acylation of the amine nitrogen, which reduces its basicity, makes hydrolysis possible with tosylic acid. Other reactions exploit hydrazones' similarity to the diazo and alkene functionalities. In the Shapiro reaction and descendants (hydrazone iodination and the Bamford–Stevens reaction), α elimination converts a sulfonamidrazone to the diazo, which then decomposes to vinyl compounds. In variants on the Lemieux–Johnson oxidation, strong oxidants peroxidize the imine nitrogen's double-bond to carbon, recovering the carbonyl and a nitrosamine. Some reductants cleave the nitrogen-nitrogen bond.
=== Ice test === Applying ice for 2–5 minutes to the muscles reportedly has a sensitivity and specificity of 76.9% and 98.3%, respectively, for the identification of MG. Acetylcholinesterase is thought to be inhibited at the lower temperature, which is the basis for this diagnostic test. This generally is performed on the eyelids when ptosis is present and is deemed positive if a ≥2-mm rise in the eyelid occurs after the ice is removed.
Sources: en.wikipedia.org
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.
Freeze-dried material is kept frozen, often at minus 20 degrees Celsius, and protected from light and moisture. Dissolved peptide is refrigerated for short-term use. Repeated freeze-thaw cycles are avoided.
A certificate of analysis typically lists purity by HPLC, the confirmed mass, appearance, and sometimes water or counter-ion content. It documents results for a specific batch. Details vary by supplier.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.