The short version of proteolysis fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
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.
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 limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
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.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
Finally, an extra ligand can associate to the palladium to form an 18-electron trigonal bipyramidal structure, with R1 and R2 cis to each other in equatorial positions. The geometry of this intermediate makes it similar to the Y-shaped above.
Individual transmembrane adenylyl cyclase isoforms have been linked to numerous physiological functions. Soluble adenylyl cyclase (sAC, AC10) has a critical role in sperm motility. Adenylyl cyclase has been implicated in memory formation, functioning as a coincidence detector. AC-IV was first reported in the bacterium Aeromonas hydrophila, and the structure of the AC-IV from Yersinia pestis has been reported. These are the smallest of the AC enzyme classes; the AC-IV (CyaB) from Yersinia is a dimer of 19 kDa subunits with no known regulatory components (PDB: 2FJT). AC-IV forms a superfamily with mammalian thiamine-triphosphatase called CYTH (CyaB, thiamine triphosphatase). These forms of AC have been reported in specific bacteria (Prevotella ruminicola O68902 and Rhizobium etli Q8KY20, respectively) and have not been extensively characterized. There are a few extra members (~400 in Pfam) known to be in class VI. Class VI enzymes possess a catalytic core similar to the one in Class III.
began the production/isolation of 99Mo in its reactor, and became the single U.S. producer of 99Mo during the 1980s. However, in 1989, Cintichem detected an underground leak of radioactive products that led to the reactor shutdown and decommissioning, putting an end to the commercial production of 99Mo in the USA. The production of 99Mo started in Canada in the early 1970s and was shifted to the NRU reactor in the mid-1970s. By 1978 the reactor provided technetium-99m in large enough quantities that were processed by AECL's radiochemical division, which was privatized in 1988 as Nordion, now MDS Nordion. In the 1990s a substitution for the aging NRU reactor for production of radioisotopes was planned. The Multipurpose Applied Physics Lattice Experiment (MAPLE) was designed as a dedicated isotope-production facility. Initially, two identical MAPLE reactors were to be built at Chalk River Laboratories, each capable of supplying 100% of the world's medical isotope demand. However, problems with the MAPLE 1 reactor, most notably a positive power co-efficient of reactivity, led to the cancellation of the project in 2008. The first commercial 99mTc generators were produced in Argentina in 1967, with 99Mo produced in the CNEA's RA-1 Enrico Fermi reactor. Besides its domestic market CNEA supplies 99Mo to some South American countries.
Sources: en.wikipedia.org
== Regulatory status == PRP is not regulated by the FDA because, like certain other human tissue and blood products, it is exempted from the traditional regulatory pathways; any use of PRP in a clinical setting is therefore considered "off label". The medical devices used to prepare PRP, however, are subject to FDA clearance.
France's "February Revolution" of 1848, was the first of the Revolutions of 1848. The events of the revolution led to the end of the 1830–1848 Orleans Monarchy and led to the creation of the Second Republic. The Revolution of 1830, part of a wave of similar regime changes across Europe, had put an end to the monarchy of the Bourbon Restoration and installed a more liberal constitutional monarchy under the Orleans dynasty governed predominantly by Guizot's conservative-liberal center-right and Thiers' progressive-liberal center-left. But to the left of the dynastic parties, the monarchy was criticized by Republicans (a mixture of Radicals and socialists) for being insufficiently democratic: its electoral system was based on a narrow, privileged electorate of property owners and therefore excluded workers. During the 1840s several petitions requesting electoral reform (universal manhood suffrage) had been issued by the National Guard but had been rejected by both of the main dynastic parties. Political meetings dedicated to this issue were banned by the government, and electoral reformers therefore bypassed the ban by holding a series of 'banquets' (1847–1848), events where the political debate was disguised as dinner speeches. This movement began overseen by Odilon Barrot's moderate center-left liberal critics of Guizot's conservative government but took on a life of its own after 1846 when the economic crisis encouraged ordinary workers to demand a say over the government.
=== June === 1 June House prices in the UK are reported to have fallen by 3.4% in the year to May, the biggest decline since July 2009. The average property price is now estimated at £260,736. A ban on e-scooters carried on Southeastern, Southern, Thameslink and Gatwick Express trains comes into force, due to concerns over fire risk. 2 June – A visibly emotional Phillip Schofield gives an interview with the BBC's Amol Rajan, in which he apologises and says his "career is over" following the affair with a young male colleague. 3 June Train strikes staged by the ASLEF union cause disruption to the 2023 FA Cup final and a Beyoncé Knowles concert. In the FA Cup Final, the first in the 152-year history of the competition to feature a Manchester derby, Manchester City defeat rivals Manchester United 2–1 to win their seventh FA Cup trophy. A man is arrested at the FA Cup final after being pictured wearing a Manchester United shirt with the number 97 and the slogan "not enough", believed to be a reference to the Hillsborough disaster. The 33-year-old male is subsequently charged with displaying threatening or abusive writing likely to cause harassment, alarm or distress. A protestor is detained by police after attempting to disrupt the 2023 Epsom Derby by trespassing on the track. 6 June Record high numbers of gonorrhoea and syphilis infections are reported, following a dip during previous years.
== Methods of studying proteins == In proteomics, there are multiple methods to study proteins. Generally, proteins may be detected by using either antibodies (immunoassays), electrophoretic separation or mass spectrometry. If a complex biological sample is analyzed, either a very specific antibody needs to be used in quantitative dot blot analysis (QDB), or biochemical separation then needs to be used before the detection step, as there are too many analytes in the sample to perform accurate detection and quantification.
Sources: en.wikipedia.org
=== Receptors === Innate immune system senses intact peptidoglycan and peptidoglycan fragments using numerous PRRs (pattern recognition receptors) that are secreted, expressed intracellularly or expressed on the cell surface.
==== Serotonergic pathway regulation ==== KOR activation suppresses serotonergic signaling through multiple mechanisms, including regulation of the serotonin transporter (SERT) via intracellular kinase cascades. Dynorphin, released from local GABAergic neurons within reward-related regions, can bind to KORs expressed on serotonergic terminals projecting from the DRN to regions such as NAcc, prefrontal cortex, and other limbic structures associated with mood regulation. Agonist-induced binding to these receptors triggers rapid, concentration-dependent upregulation of SERT function through CaMKII and Akt. This increased trafficking of SERT to the plasma membrane, enhances serotonin reuptake via p38 MAPK-mediated recruitment, coupled with increased phosphorylation of the transporter protein, reducing serotonin's functional availability to the postsynaptic 5‑HT1A and other 5‑HT receptor subtypes. Beyond depleting serotonin levels, KOR agonism directly interferes with the signaling efficacy of 5-HT1A receptor G-protein through competition as both receptors are coupled to Gi/0. The presence of KOR agonists depletes the available pool of the heterotrimeric G-proteins and the receptor's mutant variant I135L which has a high basal activity inhibits signaling mediated by the 5-HT1A. In the NAcc, stress-dependent upregulation of postsynaptic 5-HT1B receptors co-expressed on direct pathway neurons expressing prodynorphin is an additional downstream mechanism.
=== Non-antibacterial use === It is well established that tigecycline works as an effective antibiotic; however, it may have other properties that are not yet fully understood. Minocycline has been shown to have anti-inflammatory and anti-apoptotic activities, inhibition of proteolysis and suppression of angiogenesis and tumor metastasis. This is a feature not unique to minocycline, with many tetracyclines exhibiting non-antibiotic clinical benefits. Tigecycline has shown in vitro and in vivo activity against acute myeloid leukemia. The antileukemic activity of tigecycline can be attributed to the inhibition of mitochondrial protein translation in eukaryotic cells. Leukemic cells have an increased dependence on mitochondrial function, causing a heightened sensitivity to tigecycline. Tigecycline has also shown anti-cancer properties against several other kinds of tumors, including non-small cell lung cancer, gastric cancer, hepatocellular carcinoma, and glioblastoma. It also shows good activity against the causative agent of pythiosis.
2 FeCl3 + 2 H2O + SO2 → 2 FeCl2 + H2SO4 + 2 HCl 2 CuCl2 + 2 H2O + SO2 → 2 CuCl + H2SO4 + 2 HCl Two less well-known laboratory methods of producing sulfuric acid, albeit in dilute form and requiring some extra effort in purification, rely on electrolysis. A solution of copper(II) sulfate can be electrolyzed with a copper cathode and platinum/graphite anode to give spongy copper at cathode and oxygen gas at the anode. The solution of dilute sulfuric acid indicates completion of the reaction when it turns from blue to clear (production of hydrogen at cathode is another sign):
Its adherence to the concept of an exclusive one-party state alienated it from the FNLA and UNITA, which began portraying themselves as anti-communist and pro-Western in orientation. South Africa believed that if the MPLA succeeded in seizing power, it would support the PLAN militarily and lead to an unprecedented escalation of the fighting in South West Africa. While the collapse of the Portuguese colonial state was inevitable, Pretoria hoped to install a moderate anti-communist government in its place, which in turn would continue cooperating with the SADF and work to deny PLAN bases on Angolan soil. This led Prime Minister Vorster and South African intelligence chief Hendrik van den Bergh to embark on a major covert action programme in Angola, Operation Savannah. Arms and money were secretly funnelled to the FNLA and UNITA, in exchange for their promised support against PLAN. Jonas Savimbi, UNITA's president, claimed he knew where PLAN's camps in southern Angola were located and was prepared to "attack, detain, or expel" PLAN fighters. FNLA President Holden Roberto made similar assurances and promised that he would grant the SADF freedom of movement in Angola to pursue PLAN.
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.
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.