Everything below concerns Reversed-phase HPLC. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-08-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
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.
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.
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.
== Structure and binding partners == Members of the CCN protein family, including CTGF, are structurally characterized by having four conserved, cysteine-rich domains. These domains are, from N- to C-termini, the insulin-like growth factor binding protein (IGFBP) domain, the von Willebrand type C repeats (vWC) domain, the thrombospondin type 1 repeat (TSR) domain, and a C-terminal domain (CT) with a cysteine knot motif. CTGF exerts its functions by binding to various cell surface receptors in a context-dependent manner, including integrin receptors, cell surface heparan sulfate proteoglycans (HSPGs), LRPs, and TrkA. In addition, CTGF also binds growth factors and extracellular matrix proteins. The N-terminal half of CTGF interacts with aggrecan, the TSR domain interacts with VEGF and, the CT domain interacts with members of the TGF-β superfamily, fibronectin, perlecan, fibulin-1, slit, and mucins.
Einsteinium halides are known for the oxidation states +2 and +3. The most stable state is +3 for all halides from fluoride to iodide. Einsteinium(III) fluoride (EsF3) can be precipitated from Es(III) chloride solutions upon reaction with fluoride ions. An alternative preparation procedure is to exposure Es(III) oxide to chlorine trifluoride (ClF3) or F2 gas at a pressure of 1–2 atmospheres and temperature 300–400°C. The EsF3 crystal structure is hexagonal, as in californium(III) fluoride (CfF3) where the Es3+ ions are 8-fold coordinated by fluorine ions in a bicapped trigonal prism arrangement. Es(III) chloride (EsCl3) can be prepared by annealing Es(III) oxide in the atmosphere of dry hydrogen chloride vapors at about 500°C for some 20 minutes. It crystallizes upon cooling at about 425°C into an orange solid with a hexagonal structure of UCl3 type, where einsteinium atoms are 9-fold coordinated by chlorine atoms in a tricapped trigonal prism geometry. Einsteinium(III) bromide (EsBr3) is a pale-yellow solid with a monoclinic structure of AlCl3 type, where the einsteinium atoms are octahedrally coordinated by bromine (coordination number 6). The divalent compounds of einsteinium are obtained by reducing the trivalent halides with hydrogen:
== Construction of the Cologne mosque (2007) == On June 4, 2007, Kermani published a report in the Süddeutsche Zeitung about a public hearing on the construction of a mosque in the district of Cologne-Ehrenfeld. In the report, Kermani expressed enthusiasm for the open atmosphere of discussion. Attesting that the citizens present embodied "democracy in its purest form", Kermani noted that there is a "broad, cosmopolitan middle" in Cologne whose members are far more tolerant than many intellectuals.
Cetacean species recorded as prey include small toothed whales like bottlenose dolphins, common dolphins, Indo-Pacific humpback dolphins, striped dolphins, Risso's dolphins, and harbor porpoises. Bite wounds from white sharks have also been documented on species as large as beaked whales. White sharks typically attack toothed whales from behind—beyond the prey's echolocation—and target the tail, underside, or dorsal area. There are two records of white sharks managing to kill small humpback whales which were weakened by net entanglement. One case involved two sharks employing strategic bites while in the other a single shark managed to drown its victim. White sharks are more likely to scavenge large whales than hunt them. When a carcass is available, multiple sharks will gorge themselves, ripping off chunks by shaking their heads side-to-side. They may spit out pieces, possibly judging them to be too low in energy, using their teeth to detect pressure and assess the fat content. The sharks do not appear to act aggressively towards each other, but accidental bites can occur. They eventually become lethargic from overconsumption; they can no longer lift their heads out of the water, nor can they get in a good bite as they bump into the dead whale. White sharks feed on numerous fish species, including other sharks. One 2023 study found that juvenile and subadult white sharks off the east coast of Australia fed primarily on ray-finned fishes, particularly flathead grey mullets, Japanese scads, and various species of porgies, mackerels, and tuna.
Sources: en.wikipedia.org
and associated with familial thrombophilia. In 1994, the relatively common genetic mutation that produces Factor VLeiden was noted (Bertina et al.). Two years later, Gla-domainless APC was imaged at a resolution of 2.8 Ångströms. Beginning with the PROWESS clinical trial of 2001, it was recognised that many of the symptoms of sepsis may be ameliorated by infusion of APC, and mortality rates of septic patients may be significantly decreased. Near the end of that year, Drotrecogin alfa (activated), a recombinant human activated protein C, became the first drug approved by the U.S. FDA for treating severe sepsis. In 2002, Science published an article that first showed protein C activates protease-activated receptor-1 (PAR-1) and this process accounts for the protein's modulation of the immune system.
=== Thermoresponsivity in organic solvents === Due to the low entropy of mixing, miscibility gaps are often observed for polymer solutions. Many polymers are known that show UCST or LCST behavior in organic solvents. Examples for organic polymer solutions with UCST are polystyrene in cyclohexane, polyethylene in diphenylether or polymethylmethacrylate in acetonitrile. An LCST is observed for, e.g., polypropylene in n-hexane, polystyrene in butylacetate or polymethylmethacrylate in 2-propanone.
When the analytical concentration of methylamine is twice that of ethylenediamine and the concentration of copper is the same in both reactions, the concentration [Cu(en)]2+ is much higher than the concentration [Cu(MeNH2)2]2+ because β11 ≫ β12. The difference between the two stability constants is mainly due to the difference in the standard entropy change, ΔS⊖. In the reaction with the chelating ligand there are two particles on the left and one on the right, whereas in equation with the monodentate ligand there are three particles on the left and one on the right. This means that less entropy of disorder is lost when the chelate complex is formed than when the complex with monodentate ligands is formed. This is one of the factors contributing to the entropy difference. Other factors include solvation changes and ring formation. Some experimental data to illustrate the effect are shown in the following table.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
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.