A practical reference on blood-brain barrier: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-09-26 and is reviewed periodically as new material appears.
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.
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.
| 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 |
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
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.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
== History == The earliest description of a lectin is believed to have been given by Peter Hermann Stillmark in his doctoral thesis presented in 1888 to the Imperial University of Dorpat. Stillmark isolated ricin, an extremely toxic hemagglutinin, from seeds of the castor plant (Ricinus communis). Although lectins were first discovered in plants, they are now known to be present throughout nature. The first lectin to be purified on a large scale and available on a commercial basis was concanavalin A, which is now the most-used lectin for characterization and purification of sugar-containing molecules and cellular structures. The legume lectins are probably the most well-studied lectins. Long before a deeper understanding of their numerous biological functions was developed, the plant lectins, also known as phytohemagglutinins, were noted for their particularly high specificity for foreign glycoconjugates (e.g., those of fungi and animals) and used in biomedicine for blood cell testing and in biochemistry for fractionation.
Undernutrition can occur either due to protein-energy wasting or as a result of micronutrient deficiencies. It adversely affects physical and mental functioning, and causes changes in body composition and body cell mass. Undernutrition is a major health problem, causing the highest mortality rate in children, particularly in those under 5 years, and is responsible for long-lasting physiologic effects. It is a barrier to the complete physical and mental development of children. Undernutrition can manifest as stunting, wasting, and being underweight. If undernutrition occurs during pregnancy, or before two years of age, it may result in permanent problems with physical and mental development. Extreme undernutrition can cause starvation, chronic hunger, Severe Acute Malnutrition (SAM), or Moderate Acute Malnutrition (MAM). The signs and symptoms of micronutrient deficiencies depend on which micronutrient is lacking. However, undernourished people are often thin and short, with very poor energy levels; and swelling in the legs and abdomen is also common. People who are undernourished often get infections and frequently feel cold.
== Etymology == The English name "Normans" comes from the French words Normans/Normanz, plural of Normant, modern French normand, which is itself borrowed from Old Low Franconian Nortmann "Northman" or directly from Old Norse Norðmaðr, Latinized variously as Nortmannus, Normannus, or Nordmannus (recorded in Medieval Latin, 9th century) to mean "Norseman, Viking". The 11th century Benedictine monk and historian, Goffredo Malaterra, characterised the Normans thus:
Such corals require sunlight and grow in clear, shallow water, typically at depths less than 60 metres (200 feet; 33 fathoms), but corals in the genus Leptoseris have been found as deep as 172 metres (564 feet; 94 fathoms). Corals are major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the Great Barrier Reef off the coast of Australia. These corals are increasingly at risk of bleaching events where polyps expel the zooxanthellae in response to stress such as high water temperature or toxins. Other corals do not rely on zooxanthellae and can live globally in much deeper water, such as the cold-water genus Lophelia which can survive as deep as 3,300 metres (10,800 feet; 1,800 fathoms). Some have been found as far north as the Darwin Mounds, northwest of Cape Wrath, Scotland, and others off the coast of Washington state and the Aleutian Islands.
Sources: en.wikipedia.org
== Thermal conductivity == The thermal conductivity is a measure of the capacity of a material to conduct heat. In a nanofluid this conductivity is influenced by the nanoparticles suspended in the solution. A simple model only considered the thermal conductivity of the liquid and the suspended solids. This is called the Maxwell–Garnett model (1891) and is defined as:
Abbreviations: TSNA, tobacco specific nitrosoamines; LC-MS, liquid chromatography-mass spectrometry; MAO-A and B, monoamineoxidase A and B; PAH, polycyclic aromatic hydrocarbons; GS-MS, gas chromatography – mass spectrometry; ICP-MS, inductively coupled plasma – mass spectrometry; CO, carbon monoxide, VOC, volatile organic compounds; UPLC-MS, ultra-performance liquid chromatography-mass spectrometry; HPLC-DAD-MMI-MS, high performance liquid chromatography-diode array detector-multi-mode ionization-mass spectrometry.
double-strand break (DSB) The loss of continuity of the phosphate-sugar backbone in both strands of a double-stranded DNA molecule, in particular when the two breaks occur at sites that are directly across from or very close to each other on the complementary strands. Contrast single-strand break.
== Structures == Both classes of aminoacyl-tRNA synthetases are multidomain proteins. In a typical scenario, an aaRS consists of a catalytic domain (where both the above reactions take place) and an anticodon binding domain (which interacts mostly with the anticodon region of the tRNA). Transfer-RNAs for different amino acids differ not only in their anticodon but also at other points, giving them slightly different overall configurations. The aminoacyl-tRNA synthetases recognize the correct tRNAs primarily through their overall configuration, not just through their anticodon. In addition, some aaRSs have additional RNA binding domains and editing domains that cleave incorrectly paired aminoacyl-tRNA molecules. The catalytic domains of all the aaRSs of a given class are found to be homologous to one another, whereas class I and class II aaRSs are unrelated to one another. The class I aaRSs feature a cytidylyltransferase-like Rossmann fold seen in proteins like glycerol-3-phosphate cytidylyltransferase, nicotinamide nucleotide adenylyltransferase and archaeal FAD synthase, whereas the class II aaRSs have a unique fold related to biotin and lipoate ligases. The alpha helical anticodon binding domain of arginyl-, glycyl- and cysteinyl-tRNA synthetases is known as the DALR domain after characteristic conserved amino acids. Aminoacyl-tRNA synthetases have been kinetically studied, showing that Mg2+ ions play an active catalytic role and therefore aaRs have a degree of magnesium dependence.
South Africa The model remained in production in South Africa, as an entry-level model until 2003. It was also sold there as the "Midge", the "Sting", and as the "Ford Tonic". A locally designed pickup based on the Familia front end, called the Rustler was also produced, and sold as the "Ford Bantam". From 1991 to 1994 Samcor also produced and sold the 323 with the 2.0 L 16-valve DOHC FE engine from the Mazda 626 and badged it "200i". Along with the 2.0 L 16-valve DOHC engine there were upgrades to the suspension and braking system. Still, the 1.6-litre GT-Ae homologation car was more powerful. This South African built model was also sold in Australia between 1989 and 1991 with minor changes, the most noticeable one being the front indicators having a clear color rather than the normal amber. These models were labeled BF as opposed to the next generation's BG.
Sources: en.wikipedia.org
== Protein properties == There are two keyhole limpet hemocyanin genes, termed KLH1 and KLH2 which share around 60% identity at the protein level. Both encode large glycosylated proteins consisting of around 3400 amino acids and a molecular weight of around 390,000 daltons, excluding the glycosylation. The protein oligomerises to form a barrel shaped didecameric complex which is composed of 20 monomers. Each domain of a KLH subunit contains two copper atoms that together bind a single oxygen molecule (O2). When oxygen is bound to hemocyanin, the molecule takes on a distinctive transparent, opalescent blue color, due to the Cu2+ state of the copper. In the absence of oxygen, the bound copper is found as Cu1+ and hemocyanin is colorless. The KLH protein is potently immunogenic, but does not cause an adverse immune response in humans. It is therefore highly prized as a vaccine carrier protein. Because of its size and glycosylation, KLH protein cannot be reproduced synthetically; it is available only as a purified biological product from the keyhole limpet Megathura crenulata.
=== Integration of Biocon Biologics === On 6 December 2025, Biocon announced that it would fully integrate its biosimilars subsidiary Biocon Biologics Limited (BBL) as a wholly owned subsidiary, in a corporate action that valued BBL at US$5.5 billion and marked a pivot away from a previously planned initial public offering (IPO) of the biosimilars business. The company said the integration would simplify the group's corporate structure, remove the holding-company discount that had weighed on its valuation, and combine its generics and biosimilars operations into a single listed entity focused on diabetes, oncology and immunology. Under the plan, Biocon acquired the minority stakes held by Serum Institute Life Sciences, Tata Capital Growth Fund II and Activ Pine LLP through a share swap of 70.28 Biocon shares for every 100 BBL shares, priced at ₹405.78 per Biocon share. It also bought out the residual stake held by Mylan Inc. (Viatris) for US$815 million, comprising US$400 million in cash and US$415 million via a share swap, with the swap ratios based on independent valuations by EY. To fund the cash component payable to Viatris, Biocon raised approximately ₹4,150 crore (about US$460 million) through a qualified institutional placement (QIP) completed on 14 January 2026. The integration was completed by 31 March 2026, making Biocon Biologics a wholly owned subsidiary of Biocon Limited and creating a unified entity spanning biosimilars, insulins, generics and peptides. The leadership transition that followed is described under Corporate governance.
The yearly Ministerial Council Meeting, with the Ministers of Economy of all member countries and the candidates for enhanced engagement among the countries. The annual OECD Forum, which brings together leaders from business, government, labour, civil society and international organisations. Held every year since June 2000, the OECD Forum takes the form of conferences and discussions, is open to public participation and is held in conjunction with the MCM. Thematic Ministerial Meetings, held among ministers of a given domain (i.e., all Ministers of Labour, all Ministers of Environment, etc.). The bi-annual World Forum on Statistics, Knowledge and Policies, which does not usually take place in the OECD. This series of meetings has the ambition to measure and foster progress in societies. The Forum for Harmful Tax Practices OECD Eurasia Week, which includes several high-level policy dialogue discussions to share best practices and experiences in addressing common development and economic challenges in Eurasia.
== Epidemiology == Biliary atresia seems to affect females slightly more often than males, and Asians and African Americans more often than Caucasians. It is common for only one child in a pair of twins or within the same family to have the condition. There seems to be no link to medications or immunizations given immediately before or during pregnancy. Diabetes during pregnancy particularly during the first trimester seems to predispose to a number of distinct congenital abnormalities in the infant such as sacral agenesis, transposition of the great vessels and the syndromic form of biliary atresia.
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.
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.