This is a working overview of amino acid sequence, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-06-29. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
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.
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.
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.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
== Applications == The primary use of this element is in automobiles as a catalytic converter, changing harmful unburned hydrocarbons, carbon monoxide, and nitrogen oxide exhaust emissions into less noxious gases. Of 30,000 kg of rhodium consumed worldwide in 2012, 81% (24,300 kg) went into this application, and 8,060 kg was recovered from old converters. About 964 kg of rhodium was used in the glass industry, mostly for production of fiberglass and flat-panel glass, and 2,520 kg was used in the chemical industry. In 2008, net demand (with the recycling accounted for) of rhodium for automotive converters made up 84% of the world usage, with the number fluctuating around 80% in 2015−2021.
Primary polycythemias are myeloproliferative diseases affecting red blood cell precursors in the bone marrow. Polycythemia vera (PCV) (a.k.a. polycythemia rubra vera (PRV)) occurs when excess red blood cells are produced as a result of an abnormality of the bone marrow. Often, excess white blood cells and platelets are also produced. A hallmark of polycythemia vera is an elevated hematocrit, with Hct > 55% seen in 83% of cases. A somatic (non-hereditary) mutation (V617F) in the JAK2 gene, also present in other myeloproliferative disorders, is found in 95% of cases. Symptoms include headaches and vertigo, and signs on physical examination include an abnormally enlarged spleen and/or liver. Studies suggest that mean arterial pressure (MAP) only increases when hematocrit levels are 20% over baseline. When hematocrit levels are lower than that percentage, the MAP decreases in response, which may be due, in part, to the increase in viscosity and the decrease in plasma layer width. Furthermore, affected individuals may have other associated conditions alongside high blood pressure, including formation of blood clots. Transformation to acute leukemia is rare. Phlebotomy is the mainstay of treatment. Primary familial polycythemia, also known as primary familial and congenital polycythemia (PFCP), exists as a benign hereditary condition, in contrast with the myeloproliferative changes associated with acquired PCV. In many families, PFCP is due to an autosomal dominant mutation in the EPOR erythropoietin receptor gene.
=== Diet === Diet is the most essential factor to work on in people with anorexia nervosa, and must be tailored to each person's needs. Food variety is important when establishing meal plans as well as foods that are higher in energy density, especially in carbohydrates and dietary fat, which are easier for the undernourished body to break down. Evidence of a role for zinc supplementation during refeeding is unclear. Dieticians work with the medical team to add dietary supplements like iron, every other day, or calcium. Historically, practitioners have slowly increased calories at a measured pace from a starting point of around 1,200 kcal/day. However, as understanding of the process of weight restoration has improved, an approach that favors a higher starting point and a more rapid rate of increase has become increasingly common. In either approach, the end goal is typically in the range of 3,000 to 3,500 kcal/day.
John Barry Larson (born July 22, 1948) is an American politician and businessman who has been serving as the U.S. representative for Connecticut's 1st congressional district since 1999. The district is based in the state capital, Hartford. A member of the Democratic Party, Larson chaired the House Democratic Caucus during the 111th and 112th United States Congress. Larson was first elected to Congress in 1998, serving fourteen consecutive terms in the House. He attempted to seek a fifteenth term, but he was defeated in the 2026 Democratic primary by former Hartford mayor Luke Bronin.
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Addiction is a serious risk with heavy recreational amphetamine use, but is unlikely to occur from long-term medical use at therapeutic doses. Very high doses can result in psychosis, which rarely occurs at therapeutic doses even during long-term use. Recreational doses are generally much larger than prescribed therapeutic doses and carry a far greater risk of serious side effects. Amphetamine belongs to the phenethylamine class. It is also the parent compound of its own structural class, the substituted amphetamines, which includes prominent substances such as bupropion, cathinone, MDMA, and methamphetamine. As a member of the phenethylamine class, amphetamine is also chemically related to the naturally occurring trace amine neuromodulators, specifically phenethylamine and N-methylphenethylamine, both of which are produced within the human body. Phenethylamine is the parent compound of amphetamine, while N-methylphenethylamine is a positional isomer of amphetamine that differs only in the placement of the methyl group.
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.
== Related compounds == Numerous other compounds similar to levonantradol were also developed at the same time, including CP 42,096, CP 47,497, CP 55,940 and CP 55,244. The desacetyl derivative of levonantradol (DALN or CP 54,939) and its N-methyl derivative, as well as the tetracyclic analogue all have similar activity to levonantradol itself.
They show that levels of these so-called "forever chemicals" in rainwater are ubiquitously, and often greatly, above guideline safe levels worldwide. There are moves to restrict and replace their use.On 18 August, a simple method of breaking down these chemicals once they have been pulled out of contaminated water or soil is described. A preprint describes the donations-funded plans of The Galileo Project in detail: a systematic scientific research program searching for (signs of) extraterrestrial technological civilizations (ETCs) on and near Earth. 3 August – Scientists report an organ perfusion system that can restore, i.e. on the cellular level, multiple vital (pig) organs one hour after death (during which the body had warm ischaemia), after reporting a similar method/system for reviving (pig) brains hours after death in 2019. This could be used to preserve donor organs or for revival in medical emergencies. 4 August – Lab-made cartilage gel based on a synthetic hydrogel composite is found to have greater strength and wear resistance than natural cartilage, which could enable the durable resurfacing of damaged articulating joints. 8 August Researchers provide a dataset of standardized calculated detailed environmental impacts of >57,000 circulating food products, potentially e.g. informing consumers or policy. A study quantifies the large extent of climate change impacts on infectious diseases.
=== Music === C4 (American band), a neo-classical metal band set up by Michael Angelo Batio C4 (French band), French boyband C4 (mixtape), by American rapper Kendrick Lamar C4, scientific pitch notation for the note "Middle C" (261.626 Hz) C4 Records, a record label
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However, the situation might be more complex, since modern computational studies have established that traditional examples of proximity effects cannot be related directly to enzyme entropic effects. Also, the original entropic proposal has been found to largely overestimate the contribution of orientation entropy to catalysis.
==== Cold electron ionization ==== The "hard ionization" process of electron ionization can be softened by the cooling of the molecules before their ionization, resulting in mass spectra that are richer in information. In this method named cold electron ionization (cold-EI) the molecules exit the GC column, mixed with added helium make up gas and expand into vacuum through a specially designed supersonic nozzle, forming a supersonic molecular beam (SMB). Collisions with the make up gas at the expanding supersonic jet reduce the internal vibrational (and rotational) energy of the analyte molecules, hence reducing the degree of fragmentation caused by the electrons during the ionization process. Cold-EI mass spectra are characterized by an abundant molecular ion while the usual fragmentation pattern is retained, thus making cold-EI mass spectra compatible with library search identification techniques. The enhanced molecular ions increase the identification probabilities of both known and unknown compounds, amplify isomer mass spectral effects and enable the use of isotope abundance analysis for the elucidation of elemental formulas.
In addition to its possible use in the treatment of bacterial infections, penicillin is certainly useful to the bacteriologist for its power of inhibiting unwanted microbes in bacterial cultures so that penicillin-insensitive bacteria can readily be isolated. A notable instance of this is the very easy isolation of Pfeiffer's bacillus of influenza when penicillin is used ... It is suggested that it may be an efficient antiseptic for application to, or injection into, areas infected with penicillin-sensitive microbes. G. E. Breen, a fellow member of the Chelsea Arts Club, once asked Fleming if he thought it would ever be possible to make practical use of penicillin. Fleming gazed vacantly for a moment and then replied, "I don't know. It's too unstable. It will have to be purified, and I can't do that by myself." In 1941, the British Medical Journal reported that
== History == The concept of a hydrogen-like particle as a constituent of other atoms was developed over a long period. As early as 1815, William Prout used early values of atomic weight to devise what later researchers called Prout's hypothesis: all atoms are composed of integer combinations of hydrogen atoms (which he called "protyles"). When more accurate values of the atomic weights were measured, the integer relationship failed. Nevertheless the concept continued to intrigue scientists and would eventually emerge again a century later.
Sources: en.wikipedia.org
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
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.