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 2026-02-19. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Primary route studied | Intranasal | Also examined parenterally in animal work |
| Reported plasma half-life | Minutes to tens of minutes | Values vary widely between reports |
| Main model systems | Rodent behavioural and cell assays | Human trials are few and small |
| Principal proposed targets | GABA-A receptor, GABA transaminase | Monoamine and neurotrophic pathways also reported |
| Evidence grade | Preliminary | Limited independent replication |
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
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.
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.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
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.
(ASAXAA/ ASAp)(Ttc) where ASAp refers to the area of the entire fused protein that is available to the solvent that is being used, ASAXAA refers to the area of the guest residue on the ELP that is available to the solvent, and Ttc is the transition temperature that is unique to the amino acid. Summing up the contribution of each potential guest residue (XAA) will yield an SI index that is directly proportional to ΔTt,fusion. It was found that the amino acids that are charged under a physiological pH of 7.4 have the greatest impact on the overall SI of a fused protein. This is due to the fact that they are more accessible to water-containing solvents, thereby increasing the ASAXAA and also have high Ttc values. Hence, knowledge of the transition temperature of a fused protein is highly dependent on the presence of these charged residues.
The microscopic structure of liquids is complex and historically has been the subject of intense research and debate. Liquids consist of a dense, disordered packing of molecules. This contrasts with the other two common phases of matter, gases and solids. Although gases are disordered, the molecules are well-separated in space and interact primarily through molecule-molecule collisions. Conversely, although the molecules in solids are densely packed, they usually fall into a regular structure, such as a crystalline lattice (glasses are a notable exception).
Venezuela holds the world's largest proven oil reserves, estimated at 17% of the global total, or 300 billion barrels. In December 2025, the US began a maritime blockade of sanctioned oil or shadow fleet tankers. The 2025–2026 operations are seen by the Trump administration as serving the triple goals of crippling Maduro, disrupting drug trade routes, and getting access to Venezuelan oil; Trump stated that revenue generated would go to the Venezuelan people, US oil companies, and "to the United States of America in the form of reimbursement for the damages caused us by that country". Following the raid, Trump's press conference made clear that oil was a motivation for action in Venezuela. Citing the restructuring of Venezuela's oil industry in 1976 and 2007, Trump, Stephen Miller, and others claimed that Venezuela had stolen oil from US companies. Trump suggested on 5 January that seized oil could be treated as a US asset, asserting the willingness to sell it or add it to the US Strategic Petroleum Reserve. On 9 January, after other sanctioned vessels were seized, and a tanker was returned to Venezuela as part of a joint operation between interim authorities in Venezuela and the US, Trump said: "This tanker is now on its way back to Venezuela, and the oil will be sold through the GREAT Energy Deal, which we have created for such sales." The Trump administration also expressed interest in Venezuela's large deposits of gold and rare earth minerals.
Sources: en.wikipedia.org
Growing from a taproot like a carrot, dill grows up to 0.5–1.5 metres (1+1⁄2–5 feet) tall. Its stems are slender and hollow with finely divided, softly delicate leaves; the leaves are alternately arranged, 10–20 centimetres (4–8 inches) long with ultimate leaf divisions measuring 1–2 millimetres (1⁄32–3⁄32 in) broad, slightly wider than the similar leaves of fennel, which are less than 1 mm (1⁄16 in) across but harder in texture. In hot or dry weather, small white to yellow scented flowers form in small umbels 2.5–9 cm (1–3+1⁄2 in) in diameter from one long stalk. The seeds come from dried up fruit 4–5 mm (3⁄16–3⁄16 in) long and 1 mm (1⁄16 in) thick, and straight to slightly curved with a longitudinally ridged surface.
== History and background == GFS was designed by Michael C. Giddings (University of North Carolina, Chapel Hill) et al., and released in 2003. Giddings expanded the algorithms for GFS from earlier ideas. Two papers were published in 1993 explaining the techniques used to identify proteins in sequence databases. These methods determined the mass of peptides using mass spectrometry, and then used the mass to search protein databases to identify the proteins In 1999 a more complex program was released called Mascot that integrated three types of protein/database searches: peptide molecular weights, tandem mass spectrometry from one or more peptide, and combination mass data with amino acid sequence. The fallback with this widely used program is that it is unable to detect alternative splice sites that are not currently annotated, and it not usually able to find proteins that have not been annotated. Giddings built upon these sources to create GFS which would compare peptide mass data to entire genomes to identify the proteins. Giddings system is able to find new annotations of genes that have not been found, such as undocumented genes and undocumented alternative splice sites.
Also in the 4th century BCE, Herophilos and Erasistratus produced more accurate anatomical descriptions based on vivisection of criminals in Alexandria during the Ptolemaic period. In the 2nd century, Galen of Pergamum, an anatomist, clinician, writer, and philosopher, wrote the final and highly influential anatomy treatise of ancient times. He compiled existing knowledge and studied anatomy through the dissection of animals. He was one of the first experimental physiologists through his vivisection experiments on animals. Galen's drawings, based mostly on dog anatomy, became effectively the only anatomical textbook for the next thousand years. His work was known to Renaissance doctors only through Islamic Golden Age medicine until it was translated from Greek sometime in the 15th century.
Sources: en.wikipedia.org
on the toxicity findings of publicly-funded academics, whose methods are very heterogeneous, but who test, and often find, toxicity at much lower doses that industry's TG studies); or, a nation may interpret the accepted study's results according to its own criteria. According to OECD Council Decision C(97)186/Final, chemical testing data generated in any OECD member country following OECD Test Guidelines and GLP principles is recognized by other OECD member countries, such as Australia, Canada, Korea, and the USA. This recognition also extends to some non-OECD countries that fully adhere to the mutual acceptance of data (MAD) under OECD Council Decision C(97)114/Final, including Brazil, India, Malaysia, Singapore, and South Africa, as well as Argentina for industrial chemicals, pesticides, and biocides only. In June 2004, the US FDA published a comparison chart of FDA and EPA Good Laboratory Practice (GLP) regulations alongside OECD Principles for GLP, aiding in understanding the key differences and similarities in GLP standards across these regulatory bodies. Note, unlike many countries, the US EPA names its mandated use of the OECD TG, ‘the EPA Test Methods’.
== Degradation == Once secreted, GLP-1 is extremely susceptible to the catalytic activity of the proteolytic enzyme dipeptidyl peptidase-4 (DPP-4). Specifically, DPP-4 cleaves the peptide bond between Ala8-Glu9 resulting in the abundant GLP-1 (9–36) amide constituting 60–80% of total GLP-1 in circulation. DPP-4 is widely expressed in multiple tissues and cell types and exists in both a membrane-anchored and soluble circulating form. Notably, DPP-4 is expressed on the surface of endothelial cells, including those located directly adjacent to GLP-1 secretion sites. Consequently, less than 25% of secreted GLP-1 is estimated to leave the gut intact. Additionally, presumably due to the high concentration of DPP-4 found on hepatocytes, 40–50% of the remaining active GLP-1 is degraded across the liver. Thus, due to the activity of DPP-4 only 10–15% of secreted GLP-1 reaches circulation intact. Neutral endopeptidase 24.11 (NEP 24.11) is a membrane-bound zinc metallopeptidase widely expressed in several tissues, but found in particularly high concentrations in the kidneys, which is also identified accountable for the rapid degradation of GLP-1. It primarily cleaves peptides at the N-terminal side of aromatic or hydrophobic amino acids and is estimated to contribute by up to 50% to GLP-1 degradation. However, the activity only becomes apparent once the degradation of DPP-4 has been prevented, as the majority of GLP-1 reaching the kidneys has already been processed by DPP-4. Similarly, renal clearance appears more significant for the elimination of already inactivated GLP-1.
There is at least one and possibly two fossil specimens of the hadrosaur Edmontosaurus annectens with healed caudal injuries caused by Tyrannosaurus bites made while the herbivore was alive. One pair of Edmontosaurus caudal (tail) vertebrae has the tip of an adult Tyrannosaurus tooth embedded in the bone, with evidence of new bone growth that wrapped around the tooth, showing that this individual had also survived a Tyrannosaurus attack. Another specimen of Edmontosaurus (in some newspapers it was misidentified as Hadrosaurus) from Montana showed healed supposed tyrannosaur-inflicted damage on its tail vertebrae where some of its caudal neural spines was mutilated; however, in this case the damage is ambiguous and not directly attributable to Tyrannosaurus. There is also evidence for an aggressive interaction between a Triceratops and a Tyrannosaurus in the form of partially healed tyrannosaur tooth marks on a Triceratops brow horn and squamosal (a bone of the neck frill); the bitten horn is also broken, with new bone growth after the break. It is not known what the exact nature of the interaction was, though: either animal could have been the aggressor. Since the Triceratops wounds healed, it is most likely that the Triceratops survived the encounter and managed to overcome the Tyrannosaurus. In a battle against a bull Triceratops, the Triceratops would likely defend itself by inflicting fatal wounds to the Tyrannosaurus using its sharp horns.
Sources: en.wikipedia.org
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.
The peptide enters plasma rapidly and is broken down by ordinary proteases into amino acids and shorter fragments. Reported half-lives are short. Whether meaningful amounts of the intact molecule reach the brain is an open question.
Most clinical reports are small, published in Russian and not independently replicated. English-language reviews highlight the absence of large randomised trials. Conclusions about efficacy should be treated as provisional.
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.