Pro-Gly-Pro comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-07-30. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
| 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 |
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
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.
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.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
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.
== Treatment == The only curative treatment is complete surgical excision of the tumor, which can be performed even in the case of invasion into large blood vessels, such as the renal vein or inferior vena cava. The 5-year survival rate after successful surgery is 50–60%, but unfortunately, many patients are not surgical candidates. A 2018 systematic review suggests that laparoscopic retroperotenial adrenalectomy appears to reduce late morbidity, time to oral fluid or food intake and time to ambulation when compared to laparoscopic transperitoneal adrenalectomy, however there is uncertainty about these effects due to very low-quality evidence. For outcomes such as all-cause mortality, early morbidity, socioeconomic effects, and operative and postoperative parameter, the evidence is uncertain about the effects of either interventions over the other. Radiation therapy and radiofrequency ablation may be used for palliation in patients who are not surgical candidates. Minimally invasive surgical techniques remain controversial due to the absence of long-term data, with a particular concern for rates of recurrence and peritoneal carcinomatosis. Chemotherapy regimens typically include the drug mitotane, an inhibitor of steroid synthesis, which is toxic to cells of the adrenal cortex, as well as standard cytotoxic drugs. A retrospective analysis showed a survival benefit for mitotane in addition to surgery when compared to surgery alone. The two most common regimens are cisplatin, doxorubicin, etoposide (EDP) + mitotane, and streptozotocin + mitotane.
Eannatum (Sumerian: 𒂍𒀭𒈾𒁺 É.AN.NA-tum2; fl. c. 2450 BC) was a Sumerian Ensi (ruler or king) of Lagash. He established one of the first verifiable empires in history, subduing Elam and destroying the city of Susa, and extending his domain over the rest of Sumer and Akkad. One inscription found on a boulder states that Eannatum was his Sumerian name, while his "Tidnu" (Amorite) name was Lumma.
== Chemistry == Selenocysteine is the Se-analogue of cysteine. It is rarely encountered outside of living tissue (nor is it available commercially) because of its high susceptiblility to air-oxidation. More common is the oxidized derivative selenocystine, which has an Se-Se bond. Both selenocysteine and selenocystine are white solids. The Se-H group is more acidic (pKa = 5.43) than the thiol group; thus, it is deprotonated at physiological pH.
Sources: en.wikipedia.org
== History == In the 1950s, major breakthroughs in psychopharmacology occurred around the world. Then throughout the 1960s and 1970s major advances were made in synthesizing and identifying psychoactive drugs which were useful in the treatment of various mental disorders. Here, scientists had realised that these drugs interact with receptors located on neurons that led to changes in neural functioning. The connection was made shortly after the discovery of catecholamines having effects on emotion, relating to depression, and was of wide interest. Discovery was made on the decreased levels of certain neurotransmitters, catecholamines such as norepinephrine, dopamine and serotonin, and their role in the pathogenesis of depression. These past discoveries in psychopharmacology led to the development of antidepressants and a range of drugs with different functions on those neurotransmitters. But a new generation of antidepressants were resulted from the discovery of selective serotonin reuptake inhibitors (SSRIs) (e.g., fluoxetine). Although SSRIs are a group of effective antidepressant drugs with considerably few severe side effects, they are not universally effective and can also have a few unpleasant side effects, such as weight gain, sleep disturbances and anxiety. Pharmacologically and chemically unrelated to SSRIs, the past four decades, norepinephrine has been asserted to play an important, possibly primary, role in the treatment of mental disorders.
Studies show that Safe Routes to School programs are effective at increasing rates of bicycling and walking to school and decreasing injuries (Safe Routes Partnership). According to authors from the state of childhood obesity, their focus was on a few programs and policies regarding children. The Child and Adult Food Care Program (CACFP) provides federal funding to many states to reimburse providers for the cost of providing healthy meals to children and adults in their care. Around 4.3 million children and 130,000 adults partake in this program each year. Providers are required to meet the minimum nutrition standards to receive reimbursement. Some of their nutrition requirements are more whole grains, a wider variety of fruits and vegetables, free added sugars, and less saturated fat. The goal is to increase children's intake of these healthy foods, reduce their consumption of grain-based desserts, and improve their overall health. Research has been done on this program and it has been found that participation in CACFP moderately increases the consumption of milk and vegetables among children, and it helps regulate their weight. Another early childhood education program that helps prepare children for school by providing education, health, and social services is Head Start. This program reaches over one million children who have family economic trouble each year. Early Head Start serves children aged three and under and pregnant women. Head Start and Early Head Start programs participate in either CATFP or the federal school meals programs.
=== Moving-belt interface === The moving-belt interface (MBI) was developed by McFadden et al. in 1977 and commercialized by Finnigan. This interface consisted of an endless moving belt onto which the LC column effluent was deposited in a band. On the belt, the solvent was evaporated by gently heating and efficiently exhausting the solvent vapours under reduced pressure in two vacuum chambers. After the liquid phase was removed, the belt passed over a heater which flash desorbed the analytes into the MS ion source. One of the significant advantages of the MBI was its compatibility with a wide range of chromatographic conditions. MBI was successfully used for LC–MS applications between 1978 and 1990 because it allowed coupling of LC to MS devices using EI, CI, and fast-atom bombardment (FAB) ion sources. The most common MS systems connected by MBI interfaces to LC columns were magnetic sector and quadrupole instruments. MBI interfaces for LC–MS allowed MS to be widely applied in the analysis of drugs, pesticides, steroids, alkaloids, and polycyclic aromatic hydrocarbons. This interface is no longer used because of its mechanical complexity and the difficulties associated with belt renewal (or cleaning) as well as its inability to handle very labile biomolecules.
=== The Banana gang === In 2015, the Belgian authorities dismantled the Belgian-Moroccan Banana gang (Dutch: De Bananenbende), which was led by Karim A., Nabil A. and Khalid O.H., after a seizure that contained 3.4 tonnes of cocaine in Antwerp. The drugs were hidden in two containers of bananas from Colombia that had passed through Ecuador. The drugs were estimated of being worth near €100 million. The investigators admitted that the clan had been importing shipments of this type for many years and that they had important links with several Moroccan clans in the Netherlands. Fourteen people were arrested, including the manager of a hookah bar in Antwerp, and the owner of a car dealership. The Belgian intelligence services estimated that this clan generated around €300 million a year, with importing no more than 10 tonnes of cocaine from South America.
Sources: en.wikipedia.org
=== Pharmacokinetics === The conversion of codeine to morphine occurs in the liver and is catalyzed by the cytochrome P450 enzyme CYP2D6. CYP3A4 produces norcodeine, and UGT2B7 conjugates codeine, norcodeine, and morphine to the corresponding 3- and 6-glucuronides. Srinivasan, Wielbo, and Tebbett speculate that codeine-6-glucuronide is responsible for a large percentage of the analgesia of codeine, and thus these patients should experience some analgesia. CYP2D6 converts codeine into morphine, which then undergoes glucuronidation. Life-threatening intoxication, including respiratory depression requiring intubation, can develop over a matter of days in patients who have multiple functional alleles of CYP2D6, resulting in ultrarapid metabolism of opioids such as codeine into morphine. Studies on codeine's analgesic effect are consistent with the idea that metabolism by CYP2D6 to morphine is important, but some studies show no major differences between those who are poor metabolizers and extensive metabolizers. Evidence supporting the hypothesis that ultrarapid metabolizers may get greater analgesia from codeine due to increased morphine formation is limited to case reports. Due to the increased metabolism of codeine to morphine, ultrarapid metabolizers (those possessing more than two functional copies of the CYP2D6 allele) are at increased risk of adverse drug effects related to morphine toxicity.
== Research == In addition to major depressive disorder, aticaprant was under development for the treatment of alcoholism, cocaine use disorder, and smoking withdrawal. However, development for these indications was discontinued.
Improving metabolism (improving insulin sensitivity, inhibiting de novo lipogenesis, or increasing fatty acid oxidation). Metabolic modulators tested in MASH include glucagon-like peptide-1 receptor agonists (GLP-1 agonists), GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) or glucagon co-agonists and thyromimetics. Some of these drugs may treat MASFLD by significantly reducing body weight. Reducing inflammation, for example reducing oxidative stress and hepatocyte death. These drugs, such as chemokine antagonists, anti-apoptotics, vascular adhesion protein-1 inhibitors, and c-Jun N-terminal kinase inhibitors, have not shown benefit. "Gut-liver axis targets" that either change a person's microbiome, or act on bile acids Anti-fibrotic drugs, such as fibroblast growth factor analogues, which have largely not met their endpoints Other treatments such as farnesoid X receptor (FXR) agonists, peroxisome proliferator-activated receptor (PPAR) agonists, and ASK1 (apoptosis signal-regulating kinase 1) inhibitors may improve MASFLD by multiple mechanisms simultaneously.
Metal toxicity or metal poisoning is toxicity affecting plants, animals, or humans due to excessive concentration of metals. At low concentrations, metals such as copper, iron, manganese, and zinc are essential nutrients obtained through the diet supporting health, but have toxicity at high exposure concentrations. Other metals having no biological roles in animals, but with potential for toxicity include arsenic, cadmium, lead, mercury, and thallium. Exposure to metals, primarily due to occupational exposure or environmental pollution, can increase metal concentration into hazardous range. Some metals are toxic when they form poisonous soluble compounds which interfere with enzyme systems, such as superoxide dismutase, catalase, or glutathione peroxidase. Only soluble metal-containing compounds are toxic by forming coordination complexes, which consist of a metal ion surrounded by ligands. Ligands can range from water in metal aquo complexes to alkyl groups, as in tetraethyl lead. Toxic metal complexes can be detoxified by conversion to insoluble derivatives or by binding them in rigid molecular environments using chelating agents. An option for treatment of metal poisoning may be chelation therapy, which involves the administration of chelation agents to remove metals from the body.
=== GABAA receptor modulation === Some AAS, such as testosterone, DHT, stanozolol, and methyltestosterone, have been found to modulate the GABAA receptor similarly to endogenous neurosteroids like allopregnanolone, 3α-androstanediol, dehydroepiandrosterone sulfate, and pregnenolone sulfate. It has been suggested that this may contribute as an alternative or additional mechanism to the neurological and behavioral effects of AAS.
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.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.