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 2026-03-14 and is reviewed periodically as new material appears.
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.
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.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
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.
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.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
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.
The French censor cut some violent scenes and made the director change the end of his movie which was seen as "too pessimistic". Léo Joannon's film Fort du Fou (Fort of the Mad) /Outpost in Indochina was released in 1963. Another film was The 317th Platoon (La 317ème Section) was released in 1964, it was directed by Indochina War (and siege of Dien Bien Phu) veteran Pierre Schoendoerffer. Schoendoerffer has since become a media specialist about the Indochina War and has focused his production on realistic war movies. He was cameraman for the army ("Cinematographic Service of the Armies", SCA) during his duty time; moreover, as he had covered the Vietnam War he released The Anderson Platoon, which won the Academy Award for Documentary Feature. Graham Greene's novel The Quiet American takes place during this war. In 2011, Vietnamese software developer Emobi Games released a first-person-shooter called 7554. Named after the date 07-05-54 (7 May 1954) which marks the end of the decisive Battle of Dien Bien Phu, it commemorates the First Indochina War from the Vietnamese point of view. The 2017 film by Olivier Lorelle, Ciel Rouge, starring Cyril Descours and Audrey Giacomini, is set during the early part of the First Indochina War.
The two substrates of this enzyme are ethyl (S)-3-hydroxyhexanoate and oxidised nicotinamide adenine dinucleotide phosphate (NADP+). Its products are ethyl 3-oxohexanoate, reduced NADPH, and a proton. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is ethyl-(S)-3-hydroxyhexanoate:NADP+ 3-oxidoreductase. This enzyme is also called 3-oxo ester (S)-reductase.
== Discontinuous assays == Discontinuous assays are when samples are taken from an enzyme reaction at intervals and the amount of product production or substrate consumption is measured in these samples.
== Symptoms and signs == For reasons that are not understood, many people with defective variants of the AMPD genes are asymptomatic, while others have symptoms including exercise intolerance, and/or muscle pain and cramping.
Looking Glass (or Operation Looking Glass) is the historic code name for an airborne command and control center operated by the United States. Since 2016 it has been referred to as the ABNCP (Airborne National Command Post). It provides command and control of U.S. nuclear forces in the event that ground-based command centers have been destroyed or otherwise rendered inoperable. In such an event, the general officer aboard the Looking Glass serves as the Airborne Emergency Action Officer (AEAO), and by law assumes the authority of the National Command Authority and could command execution of nuclear attacks. The AEAO is supported by a battle staff of approximately 20 people, with another dozen responsible for the operation of the aircraft systems. The name Looking Glass, which is another name for a mirror, was chosen for the Airborne Command Post because the mission operates in parallel with the underground command post at Offutt Air Force Base.
Sources: en.wikipedia.org
Some quantum dots are small regions of one material buried in another with a larger band gap. These can be so-called core–shell structures, for example, with CdSe in the core and ZnS in the shell, or from special forms of silica called ormosil. Sub-monolayer shells can also be effective ways of passivating the quantum dots, such as PbS cores with sub-monolayer CdS shells. Quantum dots sometimes occur spontaneously in quantum well structures due to monolayer fluctuations in the well's thickness.
The normal function of Aβ is not yet known. Though some animal studies have shown that the absence of Aβ does not lead to any obvious loss of physiological function, several potential activities have been discovered for Aβ, including activation of kinase enzymes, protection against oxidative stress, regulation of cholesterol transport, functioning as a transcription factor, and anti-microbial activity (potentially associated with Aβ's pro-inflammatory activity). The glymphatic system clears metabolic waste from the mammalian brain, and in particular amyloid beta. A number of proteases have been implicated by both genetic and biochemical studies as being responsible for the recognition and degradation of amyloid beta; these include insulin degrading enzyme and presequence protease. The rate of removal is significantly increased during sleep. However, the significance of the glymphatic system in Aβ clearance in Alzheimer's disease is unknown.
The perineal body is a pyramidal structure of muscle and connective tissue and part of it is located between the anus and vagina. It is a tendon that is formed at the point where the bulbospongiosus muscle, superficial transverse perineal muscle, and external anal sphincter muscle converge to form this major supportive structure of the pelvis and vagina. Below this, muscles and their fascia converge and become part of the perineal body. The lower vagina is attached to the perineal body by attachments from the pubococcygeus, perineal muscles, and the anal sphincter. The perineal body is made up of smooth muscle, elastic connective tissue fibers, and nerve endings. Above the perineal body are the vagina and the uterus. Damage and resulting weakness of the perineal body changes the length of the vagina and predisposes it to rectocele and enterocele.
MDMA, also known as 3,4-methylenedioxy-N-methylamphetamine or as 1-(1,3-benzodioxol-5-yl)-N-methylpropan-2-amine, is a chemical compound of the phenethylamine, amphetamine, and methylenedioxyphenethylamine (MDxx) families. It is a derivative of various related compounds including phenethylamine, amphetamine, methamphetamine, homopiperonylamine (MDPEA), and 3,4-methylenedioxyamphetamine (MDA). MDMA is a racemic mixture of two enantiomers, (R)-MDMA and (S)-MDMA.
Sources: en.wikipedia.org
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.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.