Everything below concerns Pro-Gly-Pro. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-09-17. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 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.
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.
| 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 |
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.
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.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
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.
== Function == The collagens are a superfamily of proteins that play a role in maintaining the integrity of various tissues. Collagens are extracellular matrix proteins and have a triple-helical domain as their common structural element. Collagen VI is a major structural component of microfibrils. The basic structural unit of collagen VI is a heterotrimer of the alpha1(VI), alpha2(VI), and alpha3(VI) chains. The alpha2(VI) and alpha3(VI) chains are encoded by the COL6A2 and COL6A3 genes, respectively. The protein encoded by this gene is the alpha 1 subunit of type VI collagen (alpha1(VI) chain). Pathogenic variants in these genes are associated with collagen VI-related dystrophies, a spectrum of disorders that includes Bethlem muscular dystrophy, intermediate collagen VI-related dystrophy, and Ullrich congenital muscular dystrophy.
==== Role of Collagen VI in knee function ==== Studies have revealed that the mutation or deletion of genes encoding for collagen VI can result in numerous musculoskeletal disorders, e.g. hip osteoarthritis, tissue fibrosis, tissue ossification, and muscular dystrophies. The deletion of the COL6A1 gene in mice was used to determine the function of collagen VI in the bone and cartilage of knee joints. The absence of collagen VI impacted the structure and shape of the knee joint, but did not critically affect physicality of the cartilage.
Naturally occurring lutetium (71Lu) is composed of one stable isotope 175Lu (97.40% natural abundance) and one long-lived radioisotope, 176Lu with a half-life of 37 billion years (2.60% natural abundance). Forty synthetic radioisotopes have been added from 149Lu to 190Lu, with the most stable being 174Lu with a half-life of 3.31 years and 173Lu with a half-life of 1.37 years. All of the remaining radioactive isotopes have half-lives that are less than 9 days, and the majority of these have half-lives that are less than half an hour. Of the meta states known for this element, the most stable are 177m3Lu (t1/2 160.4 days) and 174mLu (t1/2 142 days). The primary decay mode before the most abundant stable isotope, 175Lu, is electron capture (with some alpha and positron emission), leading to ytterbium or less often thulium isotopes, and the primary mode after is beta emission giving hafnium isotopes. All isotopes of lutetium are either radioactive or, for the lone stable isotope 175Lu, observationally stable, meaning that it is predicted to be radioactive (to alpha decay) but no decay has been observed.
'Watch Men Fall') took place at Le Trianon in Paris on 25 September 2019 during the Major Arcana evening as part of the Red Bull Music Festival. Bus de Nuit, featuring two previously unreleased tracks and two remixes, was released in October.
Sources: en.wikipedia.org
The field of oxidative phosphorylation began with the report in 1906 by Arthur Harden of a vital role for phosphate in cellular fermentation, but initially only sugar phosphates were known to be involved. However, in the early 1940s, the link between the oxidation of sugars and the generation of ATP was firmly established by Herman Kalckar, confirming the central role of ATP in energy transfer that had been proposed by Fritz Albert Lipmann in 1941. Later, in 1949, Morris Friedkin and Albert L. Lehninger proved that the coenzyme NADH linked metabolic pathways such as the citric acid cycle and the synthesis of ATP. The term oxidative phosphorylation was coined by Volodymyr Belitser in 1939. For another twenty years, the mechanism by which ATP is generated remained mysterious, with scientists searching for an elusive "high-energy intermediate" that would link oxidation and phosphorylation reactions. This puzzle was solved by Peter D. Mitchell with the publication of the chemiosmotic theory in 1961. At first, this proposal was highly controversial, but it was slowly accepted and Mitchell was awarded a Nobel prize in 1978. Subsequent research concentrated on purifying and characterizing the enzymes involved, with major contributions being made by David E. Green on the complexes of the electron-transport chain, as well as Efraim Racker on the ATP synthase. A critical step towards solving the mechanism of the ATP synthase was provided by Paul D. Boyer, by his development in 1973 of the "binding change" mechanism, followed by his radical proposal of rotational catalysis in 1982.
Under the command of Bolívar and Sucre, the experienced veterans of the combined army, mainly Colombians, destroyed a royalist army under La Serna's command in the Battle of Ayacucho on 9 December 1824. La Serna's army was numerically superior but consisted of mostly new recruits. The only significant royalist area remaining on the continent was the highland country of Upper Peru. Following the Battle of Ayacucho, the royalist troops of Upper Peru under the command of Olañeta surrendered after he died in Tumusla on 2 April 1825. Bolívar tended to favor maintaining the unity of Upper Peru with Peru, but the Upper Peruvian leaders—many former royalists, like Casimiro Olañeta, nephew of General Olañeta—gathered in a congress under Sucre's auspices supported the country's independence. Bolívar left the decision to Sucre, who went along with the congress. Sucre proclaimed Upper Peru's independence in the city which now bears his name on 6 August, bringing the main wars of independence to an end. As it became clear that there was to be no reversal of Spanish American independence, several of the new states began to receive international recognition. Early, in 1822, the United States recognized Chile, the United Provinces of the Río de la Plata, Peru, Gran Colombia, and Mexico. Britain waited until 1825, after the Battle of Ayacucho, to recognize Mexico, Gran Colombia, and Río de la Plata. Both nations recognized more Spanish American states in the next few years.
== Selected articles == Ionescu‐Zanetti, C., Mechler, A., Carter, S. A., & Lal, R. (2004). Semiconductive polymer blends: Correlating structure with transport properties at the nanoscale. Advanced Materials, 16(5), 385–389. Thimm, J., Mechler, A., Lin, H., Rhee, S., & Lal, R. (2005). Calcium-dependent open/closed conformations and interfacial energy maps of reconstituted hemichannels. Journal of Biological Chemistry, 280(11), 10646–10654. Mechler, A., Praporski, S., Atmuri, K., Boland, M., Separovic, F., & Martin, L. L. (2007). Specific and selective peptide-membrane interactions revealed using quartz crystal microbalance. Biophysical Journal, 93(11), 3907–3916. Del Borgo, M. P., Mechler, A. I., Traore, D., Forsyth, C., Wilce, J. A., Wilce, M. C., ... & Perlmutter, P. (2013). Supramolecular self-assembly of N-acetyl-capped β-peptides leads to nano-to macroscale fiber formation. Angewandte Chemie International Edition, 52(32). Hasan, I. Y., & Mechler, A. (2017). Nanoviscosity measurements revealing domain formation in biomimetic membranes. Analytical chemistry, 89(3), 1855–1862. West, N. G., Bamford, S. E., Pigram, P. J., Pan, J., Qi, D. C., & Mechler, A. (2023). Controllable hierarchical self-assembly: systematic study forming metallosupramolecular frameworks on the basis of helical beta-oligoamides. Materials Horizons, 10(12), 5584–5596.
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.
Intranasal administration predominates in both animal and human research because it avoids hepatic first-pass metabolism. Injectable and intraperitoneal routes appear in animal work mainly for comparison.