If you have been reading about Selank 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.
Last reviewed on 2026-06-30. 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.
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.
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.
| 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 |
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
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.
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Ion yield is typically estimated to range from 10−4 to 10−7, with some experiments hinting to even lower yields of 10−9. The issue of low ion yields had been addressed, already shortly after introduction of MALDI by various attempts, including post-ionization utilizing a second laser. Most of these attempts showed only limited success, with low signal increases. This might be attributed to the fact that axial time-of-flight instruments were used, which operate at pressures in the source region of 10−5 to 10−6, which results in rapid plume expansion with particle velocities of up to 1000 m/s. In 2015, successful laser post-ionization was reported, using a modified MALDI source operated at an elevated pressure of ~3 mbar coupled to an orthogonal time-of-flight mass analyzer, and employing a wavelength-tunable post-ionization laser, operated at wavelength from 260 nm to 280 nm, below the two-photon ionization threshold of the matrices used, which elevated ion yields of several lipids and small molecules by up to three orders of magnitude. This approach, called MALDI-2, due to the second laser, and the second MALDI-like ionization process, was afterwards adopted for other mass spectrometers, all equipped with sources operating in the low mbar range.
Lenway, Stefanie Ann (1988). "Between war and Commerce: economic sanctions as a tool of statecraft". International Organization. 42 (2). Cambridge University Press: 397–426. doi:10.1017/S0020818300032860. S2CID 154337246. Ong, Andrew (2023). Stalemate: Autonomy and Insurgency on the China-Myanmar Border. Cornell University Press. ISBN 978-1-5017-7071-5. JSTOR 10.7591/j.ctv2t8b78b. Zhang, Chuchu (2025). China's Changing Role in the Middle East: Filling a Power Vacuum?. Changing Dynamics in Asia-Middle East Relations series. Abingdon, Oxon; New York, NY: Routledge. ISBN 978-1-032-76275-3.
== Funding == In the United Kingdom the GP contract leaves the cost of point-of-care testing, which may be substantial, with the individual GP practice, which the cost of medication is met by the clinical commissioning group, which, as the House of Commons Health and Social Care Committee noted in October 2018, creates perverse incentives.
Sources: en.wikipedia.org
CEEs are hydrolyzed in the intestines during first-pass metabolism upon oral administration. Following their absorption, they are resulfated mainly in the liver also during the first pass. Following this, they serve as a circulating reservoir and are slowly rehydrolyzed into their unconjugated active forms. Oral CEEs, at a daily dosage of 0.625 mg, achieve estrone and estradiol levels of 150 pg/mL and 30–50 pg/mL, respectively, while a daily oral dosage of 1.25 mg achieves levels of 120–200 pg/mL and 40–60 pg/mL of estrone and estradiol, respectively. The oral ingestion of 10 mg CEEs, which contains about 4.5 mg sodium estrone sulfate and 2.5 mg sodium equilin sulfate, produces maximal plasma concentrations of estrone and equilin of 1,400 pg/mL and 560 pg/mL within three and five hours, respectively. By 24 hours post-dose of 10 mg, the levels of estrone and equilin fall to 280 pg/mL and 125 pg/mL, respectively. Oral CEEs 1.25 mg/daily and oral micronized estradiol 1 mg/daily result in similar plasma concentrations of estrone and estradiol (150–300 pg/mL and 30–50 pg/mL for micronized estradiol, respectively) (oral estradiol is extensively metabolized into estrone during hepatic first-pass metabolism), although this does not account for equilin and other equine estrogens involved in the effects of CEEs, which may be significantly more potent in comparison to estrone. The pharmacokinetics of vaginal CEEs and of intravenous CEEs have been studied as well.
== Plunge freezing == The method involves ultra-rapid cooling of small tissue or cell samples to the temperature of liquid nitrogen (−196 °C) or below, stopping all motion and metabolic activity and preserving the internal structure by freezing all fluid phases solid. Typically, a sample is plunged into liquid nitrogen or into liquid ethane or liquid propane in a container cooled by liquid nitrogen. The ultimate objective is to freeze the specimen so rapidly (at 104 to 106 K per second) that ice crystals are unable to form, or are prevented from growing big enough to cause damage to the specimen's ultrastructure. The formation of samples containing specimens in amorphous ice is the "holy grail" of biological cryomicroscopy. In practice, it is very difficult to achieve high enough cooling rates to produce amorphous ice in specimens more than a few micrometres in thickness. For this purpose, plunging a specimen into liquid nitrogen at its boiling point (−196 °C) does not always freeze the specimen fast enough, for several reasons. First, the liquid nitrogen boils rapidly around the specimen forming a film of insulating N2 gas that slows heat transfer to the cryogenic liquid, known as the Leidenfrost effect. Cooling rates can be improved by pumping the liquid nitrogen with a rotary vane vacuum pump for a few tens of seconds before plunging the specimen into it.
=== Medieval period === In the Golden age of the Islamic Caliphate (medieval time in Europe), a form of passport was the bara'a, a receipt for taxes paid. Border controls were in place to ensure that only people who paid their zakah (for Muslims) or jizya (for dhimmis) taxes could travel freely between different regions of the Caliphate; thus, the bara'a receipt was a "basic passport". In medieval Europe, passports were issued as early as the reign of Henry V of England to help his subjects prove who they were in foreign lands. The earliest reference to these documents is found in an act of Parliament, the Safe Conducts Act 1414 (2 Hen. 5. Stat. 1. c. 6). In 1540, granting travel documents in England became a role of the Privy Council of England, and it was around this time that the term "passport" was used. In 1794, issuing British passports became the job of the Office of the Secretary of State. The 1548 Imperial Diet of Augsburg required the public to hold imperial documents for travel, at the risk of permanent exile. During World War I, European governments introduced border passport requirements for security reasons, and to control the emigration of people with useful skills. These controls remained in place after the war, becoming a standard, though controversial, procedure. British tourists of the 1920s complained, especially about attached photographs and physical descriptions, which they considered led to a "nasty dehumanization". Beginning in the mid-19th century, the Ottoman Empire established quarantine stations on many of its borders to control disease.
opsonin Any substance, especially certain blood-serum proteins such as immunoglobulins, that in binding to the surface of foreign cells or particulate matter increases the susceptibility of the foreign material to phagocytosis by phagocytes. Opsonins work by linking foreign particles to specific receptors on the surface of phagocytic cells in a process known as opsonization.
=== Cancer and diabetes === It has been reported that people with LS in Ecuador are resistant to cancer and diabetes and are somewhat protected against aging. This is consistent with findings in mice with a defective growth hormone receptor gene. Among the approximately 100 individuals in this population, there were no reported cases of diabetes and one case of cancer. A 2019 study of individuals with isolated growth hormone deficiency (IGHD type 1B) in Itabaianinha County, Brazil, demonstrated a phenotype consistent with Laron syndrome. Researchers found that these humans had similarly extended healthspan, with resistance to cancer and attenuated effects of aging, but neither patients with LS nor IGHD experienced an increase in their overall lifespan. Recent studies indicate that individuals with Laron syndrome exhibit significantly lower rates of cancer and enhanced metabolic health, likely as a result of reduced insulin-like growth factor 1 (IGF-1) activity, which decreases cell proliferation and activation of cancer-related pathways.
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 seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.