Pro-Gly-Pro is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2025-12-11. 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.
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 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.
| 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 |
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.
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.
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 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.
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.
=== Blood Loss === In response to significant blood loss, either acute (e.g., trauma or surgery) or chronic (e.g., gastrointestinal bleeding), the bone marrow increases production to replace lost red blood cells. This results in an increased reticulocyte count, as new immature cells are released and make up a larger proportion of the blood volume.
== Further reading == "Imaging Trace Metals in Biological Systems" pp 81–134 in "Metals, Microbes and Minerals: The Biogeochemical Side of Life" (2021) pp xiv + 341. Authors Yu, Jyao; Harankhedkar, Shefali; Nabatilan, Arielle; Fahrni, Christopher; Walter de Gruyter, Berlin. Editors Kroneck, Peter M.H. and Sosa Torres, Martha. DOI 10.1515/9783110589771-004
== External links == Images of fruit development from flowers at bioimages.Vanderbilt.edu (archived 18 February 2007) Fruit and seed dispersal images at bioimages.Vanderbilt.edu (archived 25 April 2017) Fruit Facts (Archived 2020-07-12 at the Wayback Machine from California Rare Fruit Growers, Inc.) Photo ID of Fruits (Archived 2021-01-09 at the Wayback Machine by Capt. Pawanexh Kohli) "Fruit" . Encyclopædia Britannica (11th ed.). 1911.
Sources: en.wikipedia.org
== Pharmacology == The drug is a selective KOR antagonist and shows approximately 10- to 20-fold higher affinity for the KOR (Ki = 1–3 nM) over the μ-opioid receptor (MOR) (Ki = 10–64 nM) and has negligible affinity for the δ-opioid receptor (DOR) (Ki > 4,000 nM). It is a "short-acting" or non-inactivating antagonist of the KOR (as opposed to irreversible antagonists like JDTic). Although originally characterized as a KOR neutral antagonist however, subsequent research revealed in 2020 that PF-04455242 is actually only a moderately efficacious partial antagonist of the KOR (Imax ≈ 50%). In any case, the drug reversed the analgesic and prolactin-elevating effects of the KOR agonist spiradoline in animals, showed efficacy in animal models predictive of antidepressant activity, and reversed stress-induced reinstatement of cocaine-seeking behavior. However, PF-04455242 also showed a variety of other weak off-target activities.
== Pharmacology == The pharmacodynamic profile of deudimethyltryptamine, including its interactions with serotonin receptors and its effects in animals, is similar to that of DMT. As with DMT, deudimethyltryptamine is a potent agonist of the serotonin 5-HT2A receptor and produces psychedelic-like effects in animals. However, deudimethyltryptamine, due to its deuteration, is more resistant to metabolism than DMT and shows a longer elimination half-life (by 2.5- to 2.9-fold) and slower clearance (by 38 to 55%) in animals. The brain to plasma ratio of deudimethyltryptamine was also increased (by 30%) relative to DMT, indicating slightly greater central permeability as well. The pharmacokinetics and effects of deudimethyltryptamine in humans have been studied and compared with those of DMT. Its elimination half-life was 37 to 40 minutes and its duration was approximately 40 minutes. For comparison, the half-life of DMT in humans has been reported to be 9 to 12 minutes (range 5–19 minutes). Deudimethyltryptamine produced more robust psychedelic effects than DMT at lower concentrations. Additional details on the pharmacokinetics of deudimethyltryptamine in humans have also been reported.
==== TAS1R1 + TAS1R3 ==== The TAS1R1 + TAS1R3 receptor is a G-protein-coupled receptor, much like the sweet and bitter receptors. It uses the same downstream signaling molecules, including G proteins beta-gamma, PLCB2 and IP3, to ultimately cause a release of calcium (Ca2+) from intracellular stores. Calcium activates a so-called transient-receptor-potential cation channel TRPM5 that leads to membrane depolarization and the consequent release of ATP across a channel of CALHM1 and CALHM3. The ATP released by the "Type II" cell is detected by P2X receptors on nearby afferent gustatory nerve fibers and P2Y receptors on adjacent taste cells. P2X appears to be indispensable for the transduction of umami, so this is probably the main route for umami signals. "Type III" cells, which directly connect to the nerve synapses, also respond to the released ATP by releasing neurotransmitters. One of these neurotransmitters, serotonin, regulates the release of ATP by the type II cells.
KFC Corporation, trading as Kentucky Fried Chicken (KFC), is an American multinational fast food restaurant chain specializing in Southern fried chicken and chicken sandwiches. Headquartered in Plano, Texas, it is the world's second-largest restaurant chain (as measured by sales) after McDonald's, with over 31,980 locations globally in 150 countries, as of September 2025. The chain is a subsidiary of Yum! Brands, a restaurant company that also owns the Taco Bell chain. KFC was founded by Colonel Harland Sanders (1890–1980), an entrepreneur who began selling fried chicken from his roadside restaurant in Corbin, Kentucky, during the Great Depression. Sanders identified the potential of the restaurant-franchising concept, and the first "Kentucky Fried Chicken" franchise opened in South Salt Lake, Utah, in 1952. KFC popularized chicken in the fast-food industry, diversifying the market by challenging the established dominance of the hamburger. By branding himself as "Colonel Sanders", Harland became a prominent figure of American cultural history, and his image remains widely used in KFC advertising to this day. However, the company's rapid expansion overwhelmed the aging Sanders, and he sold it to a group of investors led by John Y. Brown Jr. and Jack C. Massey in 1964.
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.
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.