Heptapeptide 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.
Updated 2026-03-02. 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.
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.
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.
| 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 |
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.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
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.
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.
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.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
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.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
Responsibility for educational supervision in Germany is primarily organised within the individual states. Optional kindergarten education is provided for all children between three and six years old, after which school attendance is compulsory for at least nine years depending on the state. Primary education usually lasts for four to six years. Secondary schooling is divided into tracks based on whether students pursue academic or vocational education. A system of apprenticeship called Duale Ausbildung leads to a skilled qualification which is almost comparable to an academic degree. It allows students in vocational training to learn in a company as well as in a state-run trade school. This model is well regarded and reproduced all around the world. Most of the German universities are public institutions, and students traditionally study without fee payment. The general requirement for attending university is the Abitur. According to an OECD report from 2014, Germany is the world's third leading destination for international study. The established universities in Germany include some of the oldest in the world, with Heidelberg University (established in 1386), Leipzig University (established in 1409) and the University of Rostock (established in 1419) being the oldest in the country. The Humboldt University of Berlin, founded in 1810 by the liberal educational reformer Wilhelm von Humboldt, became the academic model for many Western universities.
== Etymology and historical development == The term internal medicine in English has its etymology in the 19th-century German term Innere Medizin. Originally, internal medicine focused on determining the underlying "internal" or pathological causes of symptoms and syndromes through a combination of medical tests and bedside clinical examination of patients. It emphasized treatment of the diseases affecting the internal organs of the body. This approach differed from earlier generations of physicians, such as the 17th-century English physician Thomas Sydenham, known as the father of English medicine or "the English Hippocrates." Sydenham developed the field of nosology (the study of diseases) through a clinical approach that involved diagnosing and managing diseases based on careful bedside observation of the natural history of disease and their treatment. Sydenham emphasized understanding the internal mechanisms and causes of symptoms rather than dissecting cadavers and scrutinizing the internal workings of the body. In the 17th century, there was a shift towards anatomical pathology and laboratory studies, and Giovanni Battista Morgagni, an Italian anatomist of the 18th century, is considered the father of anatomical pathology. Laboratory investigations gained increasing significance, with contributions from physicians like German physician and bacteriologist Robert Koch in the 19th century. During this time, internal medicine emerged as a field that integrated the clinical approach with the use of investigations.
Ulrich Hersel; Claudia Dahmen; Horst Kessler (2003). "RGD modified polymers: biomaterials for stimulated cell adhesion and beyond". Biomaterials. 24 (24): 4385–4415. doi:10.1016/s0142-9612(03)00343-0. PMID 12922151. Wikidata Q34223126. Marco Arnold; Elisabetta A Cavalcanti-Adam; Roman Glass; Jacques Blümmel; Wolfgang Eck; Martin Kantlehner; Horst Kessler; Joachim P Spatz (2004). "Activation of integrin function by nanopatterned adhesive interfaces". ChemPhysChem. 5 (3): 383–388. doi:10.1002/cphc.200301014. PMID 15067875. Wikidata Q44832858. Kessler, Horst (July 1982). "Conformation and Biological Activity of Cyclic Peptides". Angewandte Chemie International Edition in English. 21 (7): 512–523. doi:10.1002/anie.198205121. ISSN 0570-0833. Dechantsreiter MA; Planker E; Mathä B; Lohof E; Hölzemann G; Jonczyk A; Goodman SL; Kessler H (1999). "N-Methylated cyclic RGD peptides as highly active and selective alpha(V)beta(3) integrin antagonists". Journal of Medicinal Chemistry. 42 (16): 3033–3040. doi:10.1021/jm970832g. PMID 10447947. Wikidata Q30580638. Elisabetta A Cavalcanti-Adam; Tova Volberg; Alexandre Micoulet; Horst Kessler; Benjamin Geiger; Joachim Pius Spatz (2007). "Cell spreading and focal adhesion dynamics are regulated by spacing of integrin ligands". Biophysical Journal. 92 (8): 2964–2974. doi:10.1529/biophysj.106.089730. PMC 1831685. PMID 17277192. Wikidata Q30479140. Kessler, Horst (2023). NMR: Mein Kompass in der Organischen und Medizinischen Chemie [NMR: my compass in organic and medicinal chemistry]. Berlin: GNT Publishing GmbH. ISBN 978-3-86225-132-2.
== Administration == Citalopram is typically taken in one dose, either in the morning or evening. It can be taken with or without food. Its absorption does not increase when taken with food, but doing so can help prevent nausea. Nausea is often caused when the 5-HT3 receptors actively absorb free serotonin, as this receptor is present within the digestive tract.
Sources: en.wikipedia.org
The wide occurrence of glycolysis in other species indicates that it is an ancient metabolic pathway. Indeed, the reactions that make up glycolysis and its parallel pathway, the pentose phosphate pathway, can occur in the oxygen-free conditions of the Archean oceans, also in the absence of enzymes, catalyzed by metal ions, meaning this is a plausible prebiotic pathway for abiogenesis. The most common type of glycolysis is the Embden–Meyerhof–Parnas (EMP) pathway, which was discovered by Gustav Embden, Otto Meyerhof, and Jakub Karol Parnas. Glycolysis also refers to other pathways, such as the Entner–Doudoroff pathway and various heterofermentative and homofermentative pathways. However, the discussion here will be limited to the Embden–Meyerhof–Parnas pathway. The glycolysis pathway can be separated into two phases:
Although the Vaal uprising is credited with having emboldened black civil society to carry out the final phase of opposition to apartheid, it also marked the beginning of an unprecedented upswing in political violence in South Africa, much of which set black groups against each other.
Additionally, increasing levels of OGT for O-GlcNAcylation may have therapeutic effects for Alzheimer's disease patients. Brain glucose metabolism is impaired in Alzheimer's disease, and a study suggests that this leads to hyperphosphorylation of tau and degerenation of tau O-GlcNCAcylation. Replenishing tau O-GlcNacylation in the brain along with protein phosphatase could deter this process and improve brain glucose metabolism.
Polyphenols are natural products with "several hydroxyl groups on aromatic rings", including four principal classes: phenolic acids, flavonoids, stilbenes, and lignans. Flavonoids can be grouped as flavones, flavonols, flavanols, flavanones, isoflavones, proanthocyanidins, and anthocyanins. Particularly abundant flavanoids in foods are catechin (tea, fruits), hesperetin (citrus fruits), cyanidin (red fruits and berries), daidzein (soybean), proanthocyanidins (apple, grape, cocoa), and quercetin (onion, tea, apples). Polyphenols also include phenolic acids, such as caffeic acid, and lignans, which are derived from phenylalanine present in flax seed and other cereals.
=== 1 June === Ukrenergo said Russia launched a barrage of missiles and drones targeting energy facilities in Donetsk, Zaporizhzhia, Dnipropetrovsk, Kirovohrad and Ivano-Frankivsk Oblasts. The private energy company DTEK reported that two thermal power plants were "seriously damaged". The governor of Zaporizhzhia Oblast said that the Dnieper Hydroelectric Station was in a "critical state" following the attacks. Russian officials claimed that over 10 HIMARS rockets were destroyed by air defence in Belgorod Oblast. Fragments of the rockets were recovered and photographed.
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.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.