If you have been reading about heptapeptide 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 2026-07-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| 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 |
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
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.
== Example == While performing a biceps curl, the person lifting the weight would start with a 25 pound dumbbell and do as many repetitions as possible without significantly compromising form. Then a 20-pound weight would be used until exhaustion is reached. One could continue to "drop" down as many times as they wish, but usually the weight is not dropped to below fifty percent of their one rep maximum.
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==== Cancer immunotherapy ==== In 1995, Robert Conry demonstrated that intramuscular injection of naked RNA encoding carcinoembryonic antigen elicited antigen-specific antibody responses. Then, it was elaborated by demonstrating that dendritic cells(DCs) exposed to mRNA coding for specific antigens or to total mRNA extracted from tumor cells and injected into tumor-bearing mice induced T cell immune responses and inhibited the growth of tumors. Then, researchers started to approach mRNA transfected DCs using vaccines based on ex vivo IVT mRNA-transfected DCs. Meanwhile, Argos Therapeutics had initiated a Phase III clinical trial using DCs with advanced renal cell carcinoma in 2015 (NCT01582672) but it was terminated due to the lack of efficacy. For further application, IVT mRNA was optimized for in situ transfections of DCs in vivo. It improved the translation efficiency and stability of IVT mRNA and enhanced the presentation of the mRNA-encoded antigen on MHC class I and II molecules. Then, they found out that the direct injection of naked IVT mRNA into lymph nodes was the most effective way to induce T cell responses. Based on this discovery, first-in-human testing of the injection of naked IVT mRNA encoding cancer antigens by BioNTech has started with patients with melanoma (NCT01684241). Recently, the new cancer immunotherapy, the combining of self-delivering RNA(sd-rxRNA) and adoptive cell transfer(ACT) therapy, was invented by RXi Pharmaceuticals and the Karolinska Institute.
Large portions of the book involve detailed discussions of mathematics, physics, and philosophy. Most of these discussions use fictional Arbran terminology, but treat ideas from actual science and philosophy. Stephenson acknowledges the work of author Julian Barbour as the source for much of this material. A major theme of the novel is the many-worlds interpretation of quantum mechanics based on a directed acyclic graph, which accounts for the various "worldtracks" and "narratives" explored by Fraa Orolo and manipulated by Fraa Jad. Another major theme is the recurring philosophical debate between characters espousing mathematical Platonic realism (called "Halikaarnians" in the novel and associated with Incanters) and characters espousing nominalism (called "Procians" in the novel and who are the Rhetors). Stephenson cites the work of Roger Penrose as a major influence on the novel. Specific ideas from Penrose's work include: the idea that the human mind operates in certain fundamental ways as a quantum computer, espoused in Penrose's The Emperor's New Mind; Platonic realism as a philosophical basis for works of fiction, as in stories from Penrose's The Road to Reality; and the theory of aperiodic tilings, which appear in the Teglon puzzle in the novel. Stephenson also cites as an influence the works of Kurt Gödel and Edmund Husserl, both of whom the character Durand mentions by name in the novel. Much of the Geometers' technology seen in the novel reflects existing scientific concepts. The alien ship moves by means of nuclear pulse propulsion.
Sources: en.wikipedia.org
The couple are still involved in their grown children's lives, but their "empty nest" grows crowded when Darlene, now a single mother, moves back home with her two children after losing her publishing job in Chicago, creating new conflicts and stresses. In The Conners, Dan is now a widower, Roseanne having died from an accidental overdose of pain pills. He deeply mourns her death, but after two years begins dating Louise, a former high-school classmate. Dan also becomes a grandfather a fourth time after Becky gives birth to a daughter. Though Dan was the father of four in Roseanne, youngest son Jerry has been retconned out of existence, and there are only three Conner children. In Season 3, Dan realizes he is too old to continue working as a contractor and retires. He begins working at the hardware store owned by Darlene's boyfriend, Ben. In an article about television dads, The Post and Courier editor Mindy Spar discussed how '90s TV dads became goofier than dads from earlier decades, calling Dan more like one of the children than the father. IGN editor Edgar Arce called Dan Conner a prototypical everyman. An article in the Sarasota Herald-Tribune praised Dan and Roseanne's relationship, calling it realistic and commenting that while they mock each other, viewers can feel their love while they deal with the kinds of problems real families face. Daily News editor David Bianculli stated that while they were the most entertaining and realistic couple on television, they were one of the least during their separation.
== In popular culture == In Jules Verne's 1870 novel, 20,000 Leagues Under The Sea, the story is written in the form of narration from journal entries by Professor Pierre Aronnax, a naturalist from the Paris Museum of Natural History (the name of the museum at the time). The Gallery of Palaeontology and Comparative Anatomy and other parts of Jardin des Plantes was a source of inspiration for French graphic novelist Jacques Tardi. The gallery appears on the first page and several subsequent pages of Adèle et la bête (Adèle and the Beast; 1976), the first album in the series of Les Aventures extraordinaires d'Adèle Blanc-Sec. The story opens with a 136-million-year-old pterodactyl egg hatching, and a live pterodactyl escaping through the gallery glass roof, wreaking havoc and killing people in Paris. The Gallery of Palaeontology and Comparative Anatomy returned the favour by placing a life size cardboard cutout of Adèle and the hatching pterodactyl in a glass cabinet outside the main entrance on the top floor balcony. The Pulitzer Prize–winning novel All the Light We Cannot See, by Anthony Doerr, partially takes place at the MNHN; the father of the protagonist Marie-Laure works as the chief locksmith of the museum. The story also makes many references to Jules Verne's novel 20,000 Leagues Under the Seas, and the fictional naturalist and narrator Professor Pierre Aronnax. Marie-Laure was gifted braille books of the novel by her father.
Alkyllithiums and aryllithiums may also react with N,N-disubstituted amides to give aldehydes and ketones, and symmetrical ketones by reacting with carbon monoxide. They thermally decompose to eliminate a β-hydrogen, producing alkenes and lithium hydride: another route is the reaction of ethers with alkyl- and aryllithiums that act as strong bases. In non-polar solvents, aryllithiums react as the carbanions they effectively are, turning carbon dioxide to aromatic carboxylic acids (ArCO2H) and aryl ketones to tertiary carbinols (Ar'2C(Ar)OH). Finally, they may be used to synthesise other organometallic compounds through metal-halogen exchange.
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.
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.