Everything below concerns tuftsin. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Calculated for the free peptide |
| Molecular weight | About 751.9 g/mol | Derived from the sequence |
| Appearance | White to off-white powder | Typical lyophilised form |
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.
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.
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.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
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.
=== Ferromagnetic and ferroelectric effects === The small size of nanoparticles affects their magnetic and electric properties. The ferromagnetic materials in the micrometer range is a good example: widely used in magnetic recording media, for the stability of their magnetization state, those particles smaller than 10 nm are unstable and can change their state (flip) as the result of thermal energy at ordinary temperatures, thus making them unsuitable for that application.
However the secondary meaning of Basque gibel is "indolence". In biblical Hebrew, the word for liver, כבד (Kauved, stemmed KBD or KVD, similar to Arabic الكبد), also means heavy and is used to describe the rich ("heavy" with possessions) and honor (presumably for the same reason). In the Book of Lamentations (2:11) it is used to describe the physiological responses to sadness by "my liver spilled to earth" along with the flow of tears and the overturning in bitterness of the intestines. On several occasions in the book of Psalms (most notably 16:9), the word is used to describe happiness in the liver, along with the heart (which beats rapidly) and the flesh (which appears red under the skin). Further usage as the self (similar to "your honor") is widely available throughout the old testament, sometimes compared to the breathing soul (Genesis 49:6, Psalms 7:6, etc.). An honorable hat was also referred to with this word (Job 19:9, etc.) and under that definition appears many times along with פאר Pe'er - grandeur. These four meanings were used in preceding ancient Afro-Asiatic languages such as Akkadian and Ancient Egyptian preserved in classical Ethiopic Ge'ez language. Anatomical and medical terminology often use the prefix hepat- from ἡπατο-, from the Greek word for liver, such as hepatology, and hepatitis
melting point Also liquefaction point. The temperature at which a substance changes state from a solid to a liquid. It depends on pressure and is usually specified for a given substance under standard conditions. The melting point of a substance is identical to its freezing point.
== Hybrid models == From the beginning, the cyclol reaction was considered as a covalent analog of the hydrogen bond. Therefore, it was natural to consider hybrid models with both types of bonds. This was the subject of Wrinch's fourth paper on the cyclol model (1936), written together with Dorothy Jordan Lloyd, who first proposed that globular proteins are stabilized by hydrogen bonds. A follow-up paper was written in 1937 that referenced other researchers on hydrogen bonding in proteins, such as Maurice Loyal Huggins and Linus Pauling. Wrinch also wrote a paper with William Astbury, noting the possibility of a keto-enol isomerization of the >CαHα and an amide carbonyl group >C=O, producing a crosslink >Cα-C(OHα)< and again converting the oxygen to a hydroxyl group. Such reactions could yield five-membered rings, whereas the classic cyclol hypothesis produces six-membered rings. This keto-enol crosslink hypothesis was not developed much further.
Protons and neutrons are arranged in shells, just like electrons, and so a closed shell can significantly increase stability: the known superheavy nuclei exist because of such a shell closure, probably at around 114–126 protons and 184 neutrons. They are probably close to a predicted island of stability, where superheavy nuclides should be more long-lived than otherwise expected: predictions for the longest-lived nuclides on the island range from microseconds to millions of years. It should nonetheless be noted that these are essentially extrapolations into an unknown part of the chart of nuclides, and systematic model uncertainties need to be taken into account. As the closed shells are passed, the stabilizing effect should vanish. Thus, superheavy nuclides with more than 184 neutrons are expected to have much shorter lifetimes, spontaneously fissioning within 10−15 seconds. If this is so, then it would not make sense to consider them chemical elements: IUPAC/IUPAP theorizes and recommends an element to exist only if the nucleus lives longer than 10−14 seconds, the time needed for it to gather an electron cloud. Nonetheless, theoretical estimates of half-lives are very model-dependent, ranging over many orders of magnitude. The extreme repulsion between protons is predicted to result in exotic nuclear topologies, with bubbles, rings, and tori expected: this further complicates extrapolation. It is not clear if any further-out shell closures exist, due to an expected smearing out of distinct nuclear shells (as is already expected for the electron shells at oganesson).
Sources: en.wikipedia.org
=== Demographic === Gender, age, ethnicity, life expectancy, longevity, population density, and community diversity are all demographic characteristics that can increase the risk and severity of mental disorders.
A eukaryotic cell can be 2 to 100 times larger in diameter than a typical prokaryotic cell. Eukaryotes can be single-celled, as in diatoms (microscopic algae), or microfungi such as yeasts, or multicellular, as in animals, plants, most fungi, and seaweed (macroalgae). Multicellular organisms are made up of many different types of cell known overall as somatic cells. Eukaryotes are distinguished by the presence of a membrane-bound nucleus that gives the eukaryote its name, which means "true nut" or "true kernel", where "nut" means the nucleus. The nucleus is the largest membrane-bound organelle in the eukaryotic cell. Other organelles present in all eukaryotic cells are the endoplasmic reticulum, ribosomes, the Golgi apparatus, mitochondria, lysosomes, peroxisomes, endosomes, and vesicles. The contents of the cell are contained within a cell membrane, and together with all the membranes of the organelles (except the mitochondria) are known as the endomembrane system. All of these membranes are involved in the secretory and endocytic pathways, modifying, packaging, and transporting proteins and lipids to and from the trans Golgi network. In mammalian cells, endocytosis includes early, late, and recycling endosomes. Some eukaryotes cells including plant cells and fungi have a cell wall. Plastids including chloroplasts feature mainly in plant cells. Most cell types include vaults. There are many cell variations among the different eukaryote groups. Many cells project one or more cellular extensions.
Traditionally used packaging films like LDPE (low-density polyethylene), PVC (polyvinyl chloride), EVA (ethylene-vinyl acetate) and OPP (oriented polypropylene) are not permeable enough for highly respiring products like fresh-cut produce, mushrooms and broccoli. As fruits and vegetables are respiring products, there is a need to transmit gases through the film. Films designed with these properties are called permeable films. Other films, called barrier films, are designed to prevent the exchange of gases and are mainly used with non-respiring products like meat and fish. MAP films developed to control the humidity level as well as the gas composition in the sealed package are beneficial for the prolonged storage of fresh fruits, vegetables and herbs that are sensitive to moisture. These films are commonly referred to as modified atmosphere/modified humidity packaging (MA/MH) films.
== X == Xiuhpōhualli – A 365-day solar calendar used by the Aztecs and other pre-Columbian Nahua peoples in central Mexico. It consisted of eighteen 20-day periods plus a five-day period known as Nemontemi, considered to be unlucky. Used to track agricultural cycles and schedule religious festivals, it functioned alongside the 260-day Tonalpohualli ritual calendar; together these formed a 52-year calendar round.
== History == In the early 1960s, Dr. Arnold Kadish, a physician working at Loma Linda University, developed a closed-loop device for blood glucose control using a double-lumen autoanalyzer to measure blood glucose linked to an intravenous insulin infusion pump. Although it worked, the prototype was considered so bulky, worn as a backpack, and complicated, that it was never commercialized. In 1976, the first commercialized insulin pump was created and was named the Biostator. The pump was a 60 kg bedside device. It also had the capability of monitoring blood glucose levels, so this also doubles as the first continuous glucose monitor. Between 1978 and 1988, Robert Channon, working with Guy's Hospital and the Bristol Royal Infirmary, developed a series of miniature insulin infusion pumps. Today, insulin pumps are so small that they can fit in a pocket or a purse. In the late 1970s and early 1980s, Sandia National Laboratories and the University of New Mexico School of Medicine developed a remotely programmable implantable insulin infusion system that was tested in animals and implanted in human patients beginning in 1981. In 1984, an Infusaid implantable infusion device was used to treat a 22-year-old patient successfully. The insulin pump was first endorsed in the United Kingdom in 2003 by the National Institute for Health and Care Excellence (NICE).
Sources: en.wikipedia.org
==== Mammalian studies ==== Studies conducted in rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviors (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans with sexual arousal deficits such as hypoactive sexual desire disorder. Every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a novel female. The reflexive testosterone increases in male mice is related to the male's initial level of sexual arousal. In non-human primates, it may be that testosterone in puberty stimulates sexual arousal, which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females. Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its sexual motivation decreases, but there is no corresponding decrease in ability to engage in sexual activity (mounting, ejaculating, etc.). In accordance with sperm competition theory, testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats.
== History == Sildenafil (compound UK-92,480) was synthesized in 1989 by a group of pharmaceutical chemists led by Simon Campbell working at Pfizer's Sandwich, Kent, research facility in England. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a symptom of ischaemic heart disease). The first clinical trials were conducted in Morriston Hospital in Swansea. Phase I clinical trials under the direction of Ian Osterloh suggested the drug had little effect on angina, but it could induce marked penile erections. Pfizer therefore decided to market it for erectile dysfunction, rather than for angina; this decision became an often-cited example of drug repositioning. The drug was patented in 1996, approved for use in erectile dysfunction by the FDA on 27 March 1998, becoming the first oral treatment approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year. It soon became a great success: annual sales of Viagra peaked in 2008 at US$1.934 billion.
=== Hebrew === The longest Hebrew word is the 19-letter-long (including vowels) וכשלאנציקלופדיותינו (u'chshelentsiklopediotenu), which means "And when to our encyclopedias..." The Hebrew word אנציקלופדיה (encyclopedia) is of a European origin. The longest word in Hebrew that doesn't originate from another language is וכשלהתמרמרויותינו, (u'chshelehitmarmeruyotenu) which crudely means "And when, to our resentments/ grievances" The 11-letter-long (including vowels) וְהָאֲחַשְׁדַּרְפְּנִים (veha'aḥashdarpením) (Esther 9:3) is the longest word to appear in the Hebrew Bible. – Its meaning is "And the satraps". It also does not originate from Hebrew. Other very long Hebrew words include:
The Schleswig-Holstein War Between Denmark and the German States. Leonaur Limited. ISBN 978-1-78282-522-7. Schietzel, Kurt (2022). Unearthing Hedeby: An Archaeological Exploration of the Early Medieval Settlement of Hedeby : Documentation and Chronicle 1963-2013. Wachholtz. ISBN 978-3-529-01795-7. Bregnsbo, Michael; Jensen, Kurt Villads (2016). Schleswig Holstein: Contested Region(s) Through History. University Press of Southern Denmark. ISBN 978-87-7674-870-8. Svendsen, Nick (October 2012). Generals of the Danish Army in the First and Second Schleswig-Holstein Wars, 1848-50 And 1864: Rye, Du Plat, Schleppegrell. Helion, Limited. ISBN 978-1-908916-46-4. Svendsen, Nick (19 July 2010). The First Schleswig-Holstein War 1848-50. Helion and Company. ISBN 978-1-910294-19-2.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.
Selank is a synthetic analogue built on the tuftsin tetrapeptide Thr-Lys-Pro-Arg. Extra proline residues were added to the C-terminus during design work. That modification is intended to make the peptide less vulnerable to rapid enzymatic degradation.
Transliteration from Russian produces variant spellings such as Selanc. Many suppliers avoid the trade-style name entirely and list the peptide sequence. Comparing sequences rather than names is the reliable way to confirm two entries describe the same molecule.
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.