This is a working overview of Ac-SDKP, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-22. Anything still debated is marked as such rather than presented as settled.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
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.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Research interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
TB-500 is a catalogue name applied to a synthetic peptide related to thymosin beta-4, an actin-binding protein found in most mammalian cells. Suppliers do not use the label consistently: some describe it as the full 43-residue protein, others as a short fragment from the actin-binding region, and others as a related tetrapeptide. Because the name is commercial rather than chemical, two products sold under it may not contain the same molecule. This naming ambiguity is the first point to check in any description of the material.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
Raumfordernde zerebrale Strahlennekrosen lassen sich mit hochdosierten Corticosteroiden, wie beispielsweise Dexamethason, gut behandeln. Zugängliche und operable Radionekrosen können chirurgisch entfernt werden.
== Verlauf und Prognose == Unbehandelt entwickelt sich eine Strahlennekrose progredient und ist irreversibel. Im Fall einer Strahlennekrose im Gehirn kann das nekrotische Wachstum durch seinen Raumbedarf für den Patienten fatal werden. Bei jüngeren Patienten ist die Prognose schlechter als bei älteren.
== Weiterführende Literatur == P. G. Morris, P. H. Gutin u. a.: Seizures and radionecrosis from non-small-cell lung cancer presenting as increased fluorodeoxyglucose uptake on positron emission tomography. In: Journal of Clinical Oncology. Band 29, Nr. 12, April 2011, S. e324–e326, ISSN 1527-7755. doi:10.1200/JCO.2010.33.0837. PMID 21263097. E. Maranzano, F. Trippa, F. Loreti: Tumor relapse or radionecrosis after radiosurgery: single-photon emission computed tomography for differential diagnosis. In regard to Blonigen u. a. Irradiated volume as a predictor of brain radionecrosis after linear accelerator stereotactic radiosurgery. (Int J Radiat Oncol Biol Phys 2010;77:996-1001). In: International Journal of Radiation Oncology – Biology – Physics. Band 78, Nr. 4, November 2010, S. 1279, ISSN 1879-355X. doi:10.1016/j.ijrobp.2010.07.026. PMID 20970034. O. Belohlávek, G. Simonová u. a.: Brain metastases after stereotactic radiosurgery using the Leksell gamma knife: can FDG PET help to differentiate radionecrosis from tumour progression? In: European journal of nuclear medicine and molecular imaging. Band 30, Nr. 1, Januar 2003, S. 96–100, ISSN 1619-7070. doi:10.1007/s00259-002-1011-2. PMID 12483415. L. S. Chin, L. Ma, S. DiBiase: Radiation necrosis following gamma knife surgery: a case-controlled comparison of treatment parameters and long-term clinical follow up. In: Journal of Neurosurgery. Band 94, Nr. 6, Juni 2001, S. 899–904, ISSN 0022-3085. doi:10.3171/jns.2001.94.6.0899. PMID 11409517. S. T. Chao, J. H. Suh u.
a.: The sensitivity and specificity of FDG PET in distinguishing recurrent brain tumor from radionecrosis in patients treated with stereotactic radiosurgery. In: International Journal of Cancer. Band 96, Nr. 3, Juni 2001, S. 191–197, ISSN 0020-7136. PMID 11410888. T. Tashima, T. Morioka u. a.: Delayed cerebral radionecrosis with a high uptake of 11C-methionine on positron emission tomography and 201Tl-chloride on single-photon emission computed tomography. In: Neuroradiology. Band 40, Nr. 7, Juli 1998, S. 435–438, ISSN 0028-3940. PMID 9730342.
Sources: de.wikipedia.org
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.