A practical reference on research chemical: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-03-31 and is reviewed periodically as new material appears.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Literature and online discussion often conflate TB-500 with full-length thymosin beta-4, even though the two differ in size and are not interchangeable in analytical terms. The fragment is produced by solid-phase peptide synthesis, and the product is a defined seven-residue chain rather than a biological extract. Because the term is a trade-style label, two vendors may supply materials of the same nominal sequence but different counter-ion content, purity, or water content. Comparisons across studies are therefore difficult unless the exact sequence and purity are reported.
TB-500 is a research peptide whose sequence matches residues 17 to 23 of thymosin beta-4, a 43-residue protein present in most mammalian cells. The chain is seven amino acids long, written as LKKTETQ, and is normally supplied with an acetyl group on the N-terminus. Suppliers list it as a lyophilised powder under the code name TB-500, and the same sequence appears elsewhere in catalogues as the thymosin beta-4 actin-binding fragment. The label is commercial rather than systematic, so no single authority fixes exactly what TB-500 denotes.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
| Property | Value | Notes |
|---|---|---|
| Name type | Commercial trade name | Not a systematic chemical identifier |
| Parent peptide | Thymosin beta-4 | 43-residue natural peptide |
| Common fragment sequence | LKKTETQ | Maps to part of the actin-binding region |
| Molecular size class | Roughly 0.8-1.0 kDa | Depends on exact fragment and terminal modification |
| Regulatory status | Prohibited in sport | Grouped with peptide hormones in many frameworks |
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
Regulatory status differs by country, but TB-500 is not an approved pharmaceutical in major jurisdictions. It is commonly sold as a research chemical for laboratory use, which places responsibility for identity and purity on the supplier and the laboratory. Published human data are limited, and most reports involve preclinical models or cell culture. Questions about whether the fragment mimics all actions of thymosin beta-4, and under which conditions, remain open. Independent verification of any material is therefore a practical requirement in research settings.
TB-500 is a synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Discussion of the compound frequently appears alongside other short peptides described as fragments of larger proteins. That grouping is convenient but can be misleading, because fragment length, charge, and modification state determine how a peptide behaves in solution and in any experimental system. A seven-residue acetylated peptide and a full-length protein differ in mass by roughly an order of magnitude, and they cannot be assumed to share distribution or binding properties. Precision about which molecule is under discussion is the single most useful step when reading such material.
TB-500 is a shorthand label used in supplier catalogs and online discussion for a short synthetic peptide described as a fragment of thymosin beta-4. Most product listings present it as the N-terminally acetylated heptapeptide Ac-LKKTETQ, a sequence corresponding to the actin-binding region of the parent protein. The name is not a formal chemical designation and does not appear in standard nomenclature systems. Because labeling practices vary between vendors, two products sold under the same name may not contain the same molecule, and the stated sequence should be treated as a claim rather than a fixed definition.
== Analytik == Die spezifische Drehung beträgt [α]D +17,3°, wenn es in Chloroform gelöst wurde. Der Nachweis erfolgt über Dragendorff-Reagenz, bei der eine Farbreaktion nach Orange zu beobachten ist. Die zuverlässige qualitative und quantitative Bestimmung von Aconitin gelingt nach adäquater Probenvorbereitung durch Einsatz der Kopplung der HPLC mit der Massenspektrometrie.
== Wirkung == Aconitin gilt als eines der stärksten Pflanzengifte überhaupt, es ist wirksamer als Strychnin. Aconitin und verwandte Alkaloide werden sehr schnell intestinal, aber auch über intakte Haut und Schleimhäute resorbiert. Aconitin verlangsamt die Inaktivierung des spannungsabhängigen Natriumkanals und verlängert dadurch den Einstrom von Natriumionen während des Aktionspotenzials. Es wirkt peripher wie zentral auf motorische wie sensible Nerven zunächst erregend, gefolgt von einer Lähmung. Kardiale Auswirkungen sind vor allem Arrhythmien sowie eine Bradykardie, die bei letaler Dosis zum diastolischen Herzstillstand führt. Die tödliche Dosis Aconitin liegt für einen Erwachsenen bei circa 2 Milligramm. Deshalb wurde es – gewonnen aus dem Blauen Eisenhut – früher als Pfeil-, Köder- und Mordgift verwendet. Aconitin ist verschreibungspflichtig. Es sind homöopathische Präparate auf dem Markt. Erst ab Potenz D4 (was einer Verdünnung von 1:10.000 entspricht) ist Aconitin rezeptfrei erhältlich.
Sir Joseph John Thomson OM (häufig auch J. J. Thomson; * 18. Dezember 1856 in Cheetham Hill bei Manchester; † 30. August 1940 in Cambridge) war ein britischer Physiker und Nobelpreisträger für Physik. Er entdeckte 1897 – etwa zeitgleich mit dem deutschen Physiker Emil Wiechert – das Elektron.
== Leben == Joseph John Thomson wurde am 18. Dezember 1856 als Sohn schottischer Eltern in Cheetham Hill, nahe Manchester, geboren. Sein Vater hatte ein Antiquariat. Er besuchte ab 1870 das Owens College in Manchester, das ihm eine gute naturwissenschaftliche Ausbildung verschaffte. Nach dem Willen der Eltern sollte er Ingenieur werden und in einer Lokomotivfabrik lernen. Nach dem Tod des Vaters 1873 wurde Thomson Halbwaise und diese Pläne zerschlugen sich, da die finanziellen Mittel dazu fehlten. Ab 1876 studierte er am Trinity College der University of Cambridge Mathematik und Physik mit dem Abschluss als Second Wrangler in den Tripos-Prüfungen in Mathematik 1880 (entsprechend dem Bachelor-Abschluss). Auch beim Wettbewerb um den Smith Prize, den er 1880 erhielt, schnitt er als Zweiter ab. 1883 folgte der Master-Abschluss, gleichzeitig gewann er 1882 den Adams Prize. 1884 wurde er Nachfolger von John William Strutt als Cavendish Professor of Physics in Cambridge. Am 22. Januar 1890 heiratete er Rose Elizabeth Paget (1860–1951), die Tochter des Medizinprofessors George Edward Paget und eine der ersten Forscherinnen am Cavendish-Laboratorium. Sie hatten zwei Kinder, Joan Paget Thomson und George Paget Thomson, ein weiterer Nobelpreisträger. Thomson selbst wurde als tollpatschig beschrieben. Er überwachte die Experimente und gab Anweisungen. Seine Assistenten und Schüler versuchten jedoch, ihn von der Durchführung der Experimente fernzuhalten. Einer seiner Schüler war Ernest Rutherford, der später einen Nobelpreis für Chemie erhalten sollte.
Sources: de.wikipedia.org
No. Thymosin beta-4 is a 43-residue natural peptide, while TB-500 is a commercial label applied to a short synthetic fragment of it. The two differ in length, sequence coverage and how they are handled in the laboratory.
Published work usually examines actin binding, cell migration and tissue repair endpoints in cell and animal models. Findings are generally described as preliminary, and controlled human data remain limited.
Because TB-500 is a trade name rather than a chemical identifier, different vendors and papers may attach it to different fragment lengths. Checking the stated sequence is the practical way to resolve the ambiguity.
No. Thymosin beta-4 is a 43-residue protein, while TB-500 matches only residues 17 to 23 of that chain. The two are related but differ in size, and a method that identifies one does not automatically identify the other.