If you have been reading about blood-brain barrier and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-06-21. Numbers and descriptions here follow the published literature rather than marketing material.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Modeled on tuftsin |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues |
| Approximate molecular mass | Around 750 Da | Depends on counter-ion and hydration |
| Common forms | Lyophilized powder | Also described as aqueous solution |
| Primary origin of research | Russian laboratories | Mid-1990s onward |
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.
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.
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.
=== Food safety === Water activity is used in many cases as a critical control point for Hazard Analysis and Critical Control Points (HACCP) programs. Samples of the food product are periodically taken from the production area and tested to ensure water activity values are within a specified range for food quality and safety. Measurements can be made in as little as five minutes, and are made regularly in most major food production facilities. For many years, researchers tried to equate bacterial growth potential with water content. They found that the values were not universal, but specific to each food product. W. J. Scott first established that bacterial growth correlated with water activity, not water content, in 1953. It is firmly established that growth of bacteria is inhibited at specific water activity values. U.S. Food and Drug Administration (FDA) regulations for intermediate moisture foods are based on these values. Lowering the water activity of a food product should not be seen as a kill step. Studies in powdered milk show that viable cells can exist at much lower water activity values, but that they never grow. Over time, bacterial levels decline.
Norris's mother defended her son's trips around Europe, saying he was "trying to live his life the best he could while under the pressure of a police investigation". When police questioned Norris about the fact that the vials of insulin, the murder weapon in Hall's case, had gone missing from the fridge that morning when Hall was killed, he responded by saying: "obviously if someone was to kill someone, they wouldn't leave their signature would they? To say that they were there." He denied ever injecting Hall with insulin. The police were dismissive of Norris's claim that an intruder must have come in during the night shift through the fire escape while nurses were having a cigarette before injecting Hall. Norris said this despite revealing he had never once seen an intruder on the ward. Detectives believed this suggestion that an intruder had sneaked onto a bay at night to inject a patient before sneaking away without anybody realising (since no other staff member could have been responsible) was highly implausible. Norris behaved bizarrely in the interviews he had with the police. Throughout the interviews he acted notably aggressively and arrogantly, challenging detectives, and became physically angry at times to the point where he had to be restrained. Investigators stated that Norris did not seem to be explicitly denying the murders, but insisting that they could not be proved, demanding officers told him how he did it and saying that he didn't think their facts were "good enough" to prove he had killed them.
The most important of these nuclei is the locus coeruleus, located in the pons. Outside the brain, norepinephrine is used as a neurotransmitter by sympathetic ganglia located near the spinal cord or in the abdomen, as well as Merkel cells located in the skin. It is also released directly into the bloodstream by the adrenal glands. Regardless of how and where it is released, norepinephrine acts on target cells by binding to and activating adrenergic receptors located on the cell surface. A variety of medically important drugs work by altering the actions of noradrenaline systems. Noradrenaline itself is widely used as an injectable drug for the treatment of critically low blood pressure. Stimulants often increase, enhance, or otherwise act as agonists of norepinephrine. Drugs such as cocaine and methylphenidate act as reuptake inhibitors of norepinephrine, as do some antidepressants, such as those in the SNRI class. One of the more notable drugs in the stimulant class is amphetamine, which acts as a dopamine and norepinephrine analog, reuptake inhibitor, as well as an agent that increases the amount of global catecholamine signaling throughout the nervous system by reversing transporters in the synapses. Beta blockers, which counter some of the effects of noradrenaline by blocking beta-adrenergic receptors, are sometimes used to treat glaucoma, migraines and a range of cardiovascular diseases.
Sources: en.wikipedia.org
== Threats == Predation on egg cases is thought to be a major source of mortality for developing oviparous sharks, skates and chimaeras. In general, predation is the leading cause of mortality for marine fish eggs, due to their abundance and high nutritional value. Parental care ends when the egg case is released from the body, so the embryo relies on its tough, leathery exterior as its only source of protection. Some gastropods are known to feed on egg cases by boring into the exterior. Sharks are also common predators of egg cases.
== Function == This gene encodes one of the two alpha chains of type XI collagen, a minor fibrillar collagen. It is located on chromosome 6 very close to but separate from the gene for retinoid X receptor beta. Type XI collagen is a heterotrimer but the third alpha chain is a post-translationally modified alpha 1 type II chain. Proteolytic processing of this type XI chain produces PARP, a proline/arginine-rich protein that is an amino terminal domain. Mutations in this gene are associated with type III Stickler syndrome, otospondylomegaepiphyseal dysplasia (OSMED syndrome), Weissenbacher-Zweymuller syndrome, and autosomal dominant nonsyndromic sensorineural 13 deafness. Three transcript variants encoding different isoforms have been identified for this gene.
The stroma of the cornea (or substantia propria) is a fibrous, tough, unyielding, perfectly transparent and the thickest layer of the cornea of the eye. It is between Bowman's layer anteriorly, and Descemet's membrane posteriorly. At its centre, a human corneal stroma is composed of about 200 flattened lamellae (layers of collagen fibrils), superimposed one on another. They are each about 1.5-2.5 μm in thickness. The anterior lamellae interweave more than posterior lamellae. The fibrils of each lamella are parallel with one another, but at different angles to those of adjacent lamellae. The lamellae are produced by keratocytes (corneal connective tissue cells), which occupy about 10% of the substantia propria. Apart from the cells, the major non-aqueous constituents of the stroma are collagen fibrils and proteoglycans. The collagen fibrils are made of a mixture of type I and type V collagens. These molecules are tilted by about 15 degrees to the fibril axis, and because of this, the axial periodicity of the fibrils is reduced to 65 nm (in tendons, the periodicity is 67 nm). The diameter of the fibrils is remarkably uniform and varies from species to species. In humans, it is about 31 nm. Proteoglycans are made of a small protein core to which one or more glycosaminoglycan (GAG) chains are attached. The GAG chains are negatively charged. In corneas we can find two different types of proteoglycans: Chondroitin sulphate/dermatan sulphate (CD/DS) and keratan sulphate (KS).
Sources: en.wikipedia.org
3-Methylfentanyl (3-MF, mefentanyl) is an opioid analgesic that is an analog of fentanyl. 3-Methylfentanyl is one of the most potent opioids, estimated to be between 400 and 6000 times stronger than morphine, depending on which isomer is used (with the cis isomers being the more potent ones).
=== Cuban Communist Party and government === Initially, First Secretary of the Cuban Communist Party Miguel Díaz-Canel condemned "U.S. imperialism", and called on people to prepare for a "war of the entire nation", while organizing state-sponsored demonstrations against the American oil blockade. On 6 February, he declared that "Cuba is ready for a talk with Washington on every topic without prerequisites", while rejecting negotiations on cases that he viewed as "internal Cuban affairs".
Petroleum in some form has been used since ancient times. More than 4,300 years ago, bitumen was mentioned when the Sumerians used it to make boats. A tablet of the legend of the birth of Sargon of Akkad mentions a basket which was closed by straw and bitumen. More than 4,000 years ago, according to Herodotus and Diodorus Siculus, asphalt (bitumen) was used in the construction of the walls and towers of Babylon; there were oil pits near Ardericca and Babylon and a pitch spring on Zakynthos. In Babylon, petroleum was used for road construction, ship caulking, and medicine. The use of petroleum in ancient China dates back more than 2,000 years. The I Ching, one of the earliest Chinese writings, cites that oil in its raw state, without refining, was first discovered, extracted, and used in China in the 1st century BCE. In addition, the Chinese were the first to record the use of petroleum as fuel as early as the 4th century BCE. By 347 CE, oil was produced from bamboo-drilled wells in China. In the 7th century, petroleum was among the essential ingredients for Greek fire, an incendiary projectile weapon that was used by Byzantine Greeks against Arab ships attacking Constantinople. Crude oil was distilled by Persian chemists, with clear descriptions given in Arabic handbooks such as those of Abu Bakr al-Razi. In the 9th century, oil fields were exploited in the area around modern Baku, Azerbaijan. These fields were described by Abu Bakr al-Razi in the 10th century and by Marco Polo in the 13th century, who describes the output of those wells as hundreds of shiploads.
=== Nano and biological materials === FTIR is also used to investigate various nanomaterials and proteins in hydrophobic membrane environments. Studies show the ability of FTIR to directly determine the polarity at a given site along the backbone of a transmembrane protein. The bond features involved with various organic and inorganic nanomaterials and their quantitative analysis can be done with the help of FTIR.
Sources: en.wikipedia.org
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.
It originates from research in Russia, associated with the Institute of Molecular Genetics of the Russian Academy of Sciences. The first descriptions date to the mid-1990s. Most published studies come from Russian laboratories.
No, Selank itself does not occur naturally. Its backbone is based on tuftsin, which is produced in the body, but the seven-residue version is a synthetic construct. It is supplied as a manufactured peptide.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.