This is a working overview of heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-02-16 and is reviewed periodically as new material appears.
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.
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.
| 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 |
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.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
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Activation energies consistent with proline isomerization, which typically has an activation of about 20 kcal/mol. Two-state folding kinetics indicative of both fast-folding and slow-folding populations in the unfolded or denatured state. "Double-jump" assays in which proline-containing proteins are unfolded and refolded, and the population of non-native proline conformations are studied as a function of the extent of folding. Acceleration of the in vitro folding rate by the addition of a prolyl isomerase. Acceleration of the in vitro folding rate in mutant protein variants with one or more proline residues replaced by another amino acid. Not every proline peptide bond is critical to the structure or function of a protein, and not every such bond has a significant influence on folding kinetics, especially trans bonds. Furthermore, some prolyl isomerases have a degree of sequence specificity and therefore may not catalyze the isomerization of prolines in certain sequence contexts.
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=== Nanoparticles === A novel application for gel electrophoresis is the separation or characterization of metal or metal oxide nanoparticles (e.g. Au, Ag, ZnO, SiO2) regarding the size, shape, or surface chemistry of the nanoparticles. The scope is to obtain a more homogeneous sample (e.g. narrower particle size distribution), which then can be used in further products/processes (e.g. self-assembly processes). For the separation of nanoparticles within a gel, the key parameter is the ratio of the particle size to the mesh size, whereby two migration mechanisms were identified: the unrestricted mechanism, where the particle size << mesh size, and the restricted mechanism, where particle size is similar to mesh size.
Sources: en.wikipedia.org
== Polymerization == Polypropylene glycol is produced by ring-opening polymerization of propylene oxide. The initiator is an alcohol and the catalyst a base, usually potassium hydroxide. When the initiator is ethylene glycol or water the polymer is linear. With a multifunctional initiator like glycerine, pentaerythritol or sorbitol the polymer branches out.
=== Protein === This 1686-amino acid protein belongs to the ADAMTS family and is one of 19 members known in humans. It is a large, multi-domain enzyme that undergoes extensive post-translational modifications, including N- and O-linked glycosylation, chondroitin sulfate attachment, and potential C-mannosylation and O-fucosylation of the thrombospondin (TSP) type 1 domains. The domain structure from the N-terminus to the C-terminus consists of:
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Sources: en.wikipedia.org
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== Further reading == Press Conference by professor Samuel S. Epstein M.D. 1999-05-31 World Trade Organization (2000). Dispute Settlement Reports 1998. Cambridge University Press. p. 79. ISBN 0-521-78895-1. Galbraith, H. (December 2002). "Hormones in international meat production: biological, sociological and consumer issues". Nutrition Research Reviews. 15 (2). CABI Publishing: 293–314. doi:10.1079/NRR200246. PMID 19087409. M. Ellin Doyle. "Human Safety of Hormone Implants Used to Promote Growth in Cattle". National Cattlemen's Foundation. Archived from the original (Microsoft Word) on 7 May 2006. J. J. Kastner & R. K. Pawsey (29 November 2001). "Harmonising sanitary measures and resolving trade disputes through the WTO–SPS framework. Part I: a case study of the US–EU hormone-treated beef dispute" (PDF). Food Control. 13. Elsevier Science Ltd.: 49–55. doi:10.1016/S0956-7135(01)00023-8. Archived from the original (PDF) on 21 May 2004. Tim Josling; Donna Roberts & Ayesha Hassan (12 April 2000). "The Beef-Hormone Dispute and its Implications for Trade Policy" (PDF). Stanford University. Archived from the original (PDF) on 11 June 2007. Grace Skogstad (September 2001). "The WTO and Food Safety Regulatory Policy Innovation in the European Union". Journal of Common Market Studies. 39 (3): 485–505. doi:10.1111/1468-5965.00300. Christina L. Davis (2003). "Battles over Beef: The Beef Hormone Dispute". Food Fights Over Free Trade: How International Institutions Promote Agricultural Trade Liberalization. Princeton University Press. pp. 321–337. ISBN 0-691-11505-2.
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=== Other interventions === A 2024 review found that fecal microbiota transplantation may reduce pain intensity and improve fatigue and quality of life in patients with fibromyalgia, but evidence was insufficient at that stage to support use. Research on gut microbiome links with FM continues. Hyperbaric oxygen therapy (HBOT) has shown beneficial effects in treating chronic pain by reducing inflammation and oxidative stress. However, treating fibromyalgia with hyperbaric oxygen therapy is still controversial, in light of the scarcity of large-scale clinical trials. In addition, hyperbaric oxygen therapy raises safety concerns due to the oxidative damage that may follow it. An evaluation of nine trials with 288 patients in total found that HBOT was more effective at relieving fibromyalgia patients' pain than the control intervention. In most of the trials, HBOT improved sleep disturbance, multidimensional function, patient satisfaction, and tender spots. Negative outcomes (predominantly mild barotrauma (air pressure effect on ear or lung) that could be resolved spontaneously) were experienced by 24% of the patients, but they were not prevented from completing the treatment regimen, and no serious side effects, complications, or deaths were reported.
=== Order of magnitude estimates === The following table illustrates the range of viscosity values observed in common substances. Unless otherwise noted, a temperature of 25 °C and a pressure of 1 atmosphere are assumed. The values listed are representative estimates only, as they do not account for measurement uncertainties, variability in material definitions, or non-Newtonian behavior.
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.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.