Everything below concerns TKPRPGP. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-02-18. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
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.
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.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
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.
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.
This can be very labor-intensive, and usually limits the method to proteins smaller than 25 kDa. Because it takes minutes to hours to record a HSQC spectrum, amides that exchange quickly must be measured using other pulse sequences.
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==== K ==== Katsuobushi – the Japanese name for dried, fermented, and smoked skipjack tuna (Katsuwonus pelamis). Keumamah – traditional Acehnese dried fish. Kipper – a whole herring, a small, oily fish, that has been split in butterfly fashion from tail to head along the dorsal ridge, gutted, salted or pickled, and cold smoked over smouldering woodchips (typically oak). Kusaya – a salted-dried and fermented fish that is produced in the Izu Islands, Japan. Though the smell of kusaya is strong, its taste is quite mellow.
Similarly, maritime crossings across the Taiwan Strait require special permits from both the People's Republic of China and the Republic of China and are usually off-limits to foreign vessels. In India, foreign vessels engaging in the coasting trade require a licence that is generally only issued when no local vessel is available. Similarly, a foreign vessel may only be issued a licence to engage in cabotage in Brazil if there are no Brazilian flagged vessels available for the intended transport. As with maritime cabotage, most jurisdictions heavily restrict cabotage in passenger aviation, though rules regarding air cargo are typically more lax. Passenger cabotage is not usually granted under most open skies agreements. Air cabotage policies in the European Union are uniquely liberal insofar as carriers licensed by one member state are permitted to engage in cabotage in any EU member state, with few limitations. Chile has the most liberal air cabotage rules in the world, enacted in 1979, which allow foreign airlines to operate domestic flights, conditional upon reciprocal treatment for Chilean carriers in the foreign airline's country. Countries apply special provisions to the ability of foreign airlines to carry passengers between two domestic destinations through an offshore hub. Many countries implement air defence identification zones (ADIZs) requiring aircraft approaching within a specified distance of their airspace to contact or seek prior authorization from their military or transport authorities.
Sources: en.wikipedia.org
Polyphenols comprise up to 0.2–0.3% fresh weight for many fruits. Consuming common servings of wine, chocolate, legumes or tea may also contribute to about one gram of intake per day. According to a 2005 review on polyphenols:
Russian officials claimed that one person was killed in a Ukrainian drone strike in Belgorod Oblast. Canada imposed new sanctions on Russian individuals and entities for facilitating the illegal transfer of North Korean weapons, including ballistic missiles, for use in the invasion of Ukraine. The EU agreed to allow Ukraine to use the interest earned from seized Russian assets, totalling approximately 2.5 billion to 3 billion euros ($2.7 billion to $3.3 billion) annually, disbursed twice per year. Institutions will keep all interest earned between February 2022 and February 2024, possibly for reconstruction purposes, according to European Commission sources. More than 3,000 Ukrainian prisoners have applied to join the Ukrainian military.
Certified histocompatibility associate, certified histocompatibility technologist, certified histocompatibility specialist, and diplomate of the ABHI are titles granted by the American Board of Hisocompatibility and Immunogenetics after meeting education and experience requirements and passing the required examination; those individuals would hold the credentials CHA (ABHI), CHT (ABHI), CHS (AHBI), and D (ABHI) upon passing the corresponding examination. In the United States, medical laboratory scientists can be certified and employed in infection control. These professionals monitor and report infectious disease findings to help limit iatrogenic and nosocomial infections. They may also educate other healthcare workers about such problems and ways to minimize them. In the United Kingdom, the number of clinical scientists in a pathology discipline is typically greater, where less medically qualified pathologists train as consultants. Clinical biochemistry, clinical immunology and genomic medicine are specialities with an abundance of UK clinical scientists, and where the role is well established. Infection services in the UK are generally undertaken by medically qualified Microbiologists, who may have overall responsibility for laboratory services in addition to Infection Prevention and Control responsibilities, and may be required to contribute to ward rounds and patient clinics.
As described above, the use of N-terminal and side chain protecting groups is essential during peptide synthesis to avoid undesirable side reactions, such as self-coupling of the activated amino acid leading to (polymerization). This would compete with the intended peptide coupling reaction, resulting in low yield or even complete failure to synthesize the desired peptide. Two principle protecting group schemes are typically used in solid phase peptide synthesis: so-called Boc/benzyl and Fmoc/tert-butyl approaches. The Boc/Bzl strategy utilizes TFA-labile N-terminal Boc protection alongside side chain protection that is removed using anhydrous hydrogen fluoride during the final cleavage step (with simultaneous cleavage of the peptide from the solid support). Fmoc/tBu SPPS uses base-labile Fmoc N-terminal protection, with side chain protection and a resin linkage that are acid-labile (final acidic cleavage is carried out via TFA treatment). Both approaches, including the advantages and disadvantages of each, are outlined in more detail below.
The pelvis was a large structure. Its upper bone, the ilium, was both very long and high, providing an extensive attachment area for hindlimb muscles. The front pubic bone ended in an enormous pubic boot, longer than the entire shaft of the element. The rear ischium was slender and straight, pointing obliquely to behind and below. In contrast to the arms, the hindlimbs were among the longest in proportion to body size of any theropod. In the foot, the metatarsus was "arctometatarsalian", meaning that the part of the third metatarsal near the ankle was pinched. The third metatarsal was also exceptionally sinuous. Compensating for the immense bulk of the animal, many bones throughout the skeleton were hollowed, reducing its weight without significant loss of strength.
Sources: en.wikipedia.org
This reaction highlights a distinctive property of sulfur: its ability to catenate (bind to itself by formation of chains). Protonation of these polysulfide anions produces the polysulfanes, H2Sx where x = 2, 3, and 4. Ultimately, reduction of sulfur produces sulfide salts:
==== List of P-CABs in the markets (First year of approval for clinical use) ==== Revaprazan (2006) Vonoprazan (2014) Tegoprazan (2018) Fexuprazan (2021) Keverprazan (2023/China) Zastaprazan (2024/South Korea)
There is an obvious similarity between use of molecular or phenotypic data in the field of cladistics and analyses of morphological characters using a substitution model. However, there has been a vociferous debate in the systematics community regarding the question of whether or not cladistic analyses should be viewed as "model-free". The field of cladistics (defined in the strictest sense) favor the use of the maximum parsimony (MP) criterion for phylogenetic inference. Many cladists reject the position that maximum parsimony is based on a substitution model and (in many cases) they justify the use of parsimony using the philosophy of Karl Popper. However, the existence of "parsimony-equivalent" models (i.e., substitution models that yield the maximum parsimony tree when used for analyses) makes it possible to view parsimony as a substitution model. Even when maximum parsimony is used to construct a tree, substitution models can still play a role in checking the statistical validity of a tree. An example is Sun et al. (2018), where the majority-rule consensus of MP trees is annotated with Bayesian posterior probabilities under the Mk model.
On 21 July 1954, the Geneva Accords were signed. They established the terms of a ceasefire, the division of Vietnam at the 17th parallel north, the regrouping of Pathet Lao forces in two provinces of Laos, and the disarmament of the United Issarak Front (UIF) in Cambodia. France also undertook under these agreements to respect the independence of the three Indochinese states and to withdraw its troops at their request. Việt Minh troops had several months to evacuate Laos and Cambodia. A free election was to be held in Vietnam in 1956 under international supervision, with a view to reunification.
Transformation of a bacterial host with two different plasmids is required. One is designed to express a DNA-binding protein-of-interest as a fusion construct with a subunit of RNA polymerase (bait). The other plasmid contains a region of randomized sequence representing potential binding sites (prey) which, if bound to by the chimeric fusion product, drives expression of downstream reporter genes. This reporter region facilitates both positive and negative selection by HIS3 and URA3, respectively, which together allow for isolation of the prey containing the true DNA target sequence. HIS3 and URA3 encode proteins required for biosynthesis of histidine and uracil. Using a negative selectable marker is crucial for greatly reducing the incidence of false-positives. Self-activating prey, where the randomized region facilitate reporter expression in the absence of TF binding, are removed by transforming the reporter vector library into bacteria in the absence of bait and assaying for growth on plates containing 5-fluoro-orotic acid (5-FOA). The protein product of URA3 converts 5-FOA into a toxic compound, thereby allowing survival of only those colonies that contain reporter vectors which are not self-activating. Negative selection normally precedes positive selection so that a smaller, purified prey library can be subjected to the more rigorous positive selection process. Upon transformation of the purified prey library with the bait plasmid, positive selection is achieved by growing the host E.
Sources: en.wikipedia.org
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.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.