The short version of freeze-thaw cycle fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Principal proposed target | GABA-A receptor complex | Hypothesis derived mainly from animal pharmacology |
| Common behavioral assay | Elevated plus maze | Rodent test for anxiety-like behavior |
| Reported molecular marker | Hippocampal BDNF expression | Measured by immunoassay or mRNA quantification |
| Typical dosing route | Intranasal | Chosen to reduce first-pass metabolism |
| Reported plasma half-life | Minutes | Based on limited peptide stability data |
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.
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.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
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.
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.
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.
Subsequently, those selecting the recipients have exercised wide latitude in determining what falls under the umbrella of Physiology or Medicine. The awarding of the prize in 1973 to Nikolaas Tinbergen, Konrad Lorenz, and Karl von Frisch for their observations of animal behavioural patterns could be considered a prize in the behavioural sciences rather than medicine or physiology. Tinbergen expressed surprise in his Nobel Prize acceptance speech at "the unconventional decision of the Nobel Foundation to award this year's prize 'for Physiology or Medicine' to three men who had until recently been regarded as 'mere animal watchers'".
Flyorov is also known for the discovery of spontaneous fission with Konstantin Petrzhak. IUPAC approved the name in May, 2012 and the naming ceremony for flerovium and livermorium was held on 24 October 2012 in Moscow. Other proposals included atlantisium (An, a reference via Atlantis to the island of stability), lazarevium (Lz, in honor of Yuri Lazarev), and oganessium (Og, in honor of Yuri Oganessian). In a 2015 interview with Oganessian, the host, in preparation to ask a question, said, "You said you had dreamed to name [an element] after your teacher Georgy Flyorov." Without letting the host finish, Oganessian repeatedly said, "I did."
=== Glucocorticoid activity === Progesterone is a partial agonist of the glucocorticoid receptor (GR). It has about 35% of the affinity of dexamethasone, a corticosteroid, for the human GR, and about 3 to 11% of the affinity of dexamethasone for the rat GR. However, progesterone appears to show weak or no glucocorticoid activity and no antiglucocorticoid activity in vitro and in animals. Nonetheless, progesterone has been found to upregulate the thrombin receptor in vascular smooth muscle cells in vitro, a glucocorticoid effect, and this could have clinical relevance in relation to risk of blood clots.
anorexia lethargy profuse watery to bloody diarrhea (bloody diarrhea is more common in dogs with parvovirus than cats) vomiting (most common in cats) Clinical laboratory findings include (but are not limited to):
Theraflu (made by Novartis) — previously contained pseudoephedrine, now contains phenylephrine Trima — contains 60 mg pseudoephedrine hydrochloride Tylol Hot (made by NOBEL İLAÇ SANAYİİ VE TİCARET A.Ş., Turkey) — a packet of 20 g contains 60 mg pseudoephedrine hydrochloride, 500 mg paracetamol and 4 mg chlorpheniramine maleate Unifed (made by United Pharmaceutical Manufacturer, Jordan) — contains pseudoephedrine hydrochloride (also triprolidine and guaifenesin). Zyrtec-D 12 Hour (made by McNeil Consumer Healthcare, a Kenvue company) — contains 120 mg pseudoephedrine hydrochloride (also 5 mg of cetirizine). Zephrex-D (made by Westport Pharmaceuticals) – a special meth-resistant form of pseudoephedrine that becomes gooey when heated.
Sources: en.wikipedia.org
He ran out of supplies shortly before a training camp in Australia and took Blackstone Labs DUST, a supplement which is mixed with water and is supposedly similar to C4. On August 26, 2019, NASCAR crew chief Matt Borland was indefinitely suspended under the sanctioning body's substance abuse policy after testing positive for DMAA. In a statement, Borland said that the positive test was most likely caused by a diet coffee he had felt comfortable drinking "after doing my due diligence." Team owner Bob Germain Jr. also said that he did not believe Borland “had reason to know that the coffee contained a banned substance. However, we also understand and respect NASCAR’s decisions to strictly uphold their policies for each and every owner, driver and crew member in the garage." The suspension was lifted on September 24 after completing NASCAR's mandatory "Road to Recovery Program".
=== Halides === Actinium trifluoride can be produced either in solution or in solid reaction. The former reaction is carried out at room temperature, by adding hydrofluoric acid to a solution containing actinium ions. In the latter method, actinium metal is treated with hydrogen fluoride vapors at 700 °C (1,292 °F) in an all-platinum setup. Treating actinium trifluoride with ammonium hydroxide at 900–1,000 °C (1,650–1,830 °F) yields oxyfluoride AcOF. Whereas lanthanum oxyfluoride can be easily obtained by burning lanthanum trifluoride in air at 800 °C (1,470 °F) for an hour, similar treatment of actinium trifluoride yields no AcOF and only results in melting of the initial product.
== A posteriori therapeutic drug monitoring == The concept of a posteriori TDM corresponds to the usual meaning of TDM in medical practice, which refers to the readjustment of the dosage of a given treatment in response to the measurement of an appropriate marker of drug exposure or effect. TDM encompasses all aspects of this feedback control, namely:
Centromere protein A, also known as CENPA, is a protein which in humans is encoded by the CENPA gene. CENPA is a histone H3 variant which is the critical factor determining the kinetochore position(s) on each chromosome in most eukaryotes including humans.
=== In waste disposal === In 2015, it was discovered that 100 mealworms can degrade polystyrene into usable organic matter at a rate of about 34–39 milligrams per day. No difference was found between mealworms fed only Styrofoam and the mealworms fed conventional foods, during the one-month duration of the experiment. Microorganisms inside the mealworm's gut are responsible for degrading the polystyrene, proven by reducing the property of degradation when mealworms were given gentamicin. Isolated colonies of the mealworm's gut microbes, however, have proven less efficient at degradation than the bacteria within the gut.
Sources: en.wikipedia.org
Intranasal administration predominates in both animal and human research because it avoids hepatic first-pass metabolism. Injectable and intraperitoneal routes appear in animal work mainly for comparison.
Behavioral endpoints include time spent in open arms of the elevated plus maze and avoidance latencies. Biochemical endpoints include BDNF concentration, cytokine levels, and monoamine metabolite ratios in brain tissue.
Most published studies are small, originate from a limited number of laboratories, and lack independent replication. Dose-response relationships, measured brain exposure, and long-term outcomes are not well characterized.
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.