A practical reference on thymosin beta-4: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-02-17. Anything still debated is marked as such rather than presented as settled.
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.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Supplied as a lyophilised cake in sealed vials |
| Solubility class | Freely soluble in water | Polar and charged side chains dominate the sequence |
| Typical storage temperature | -20 °C or below | Dry and dark; a desiccant is often recommended |
| Identity confirmation | Mass spectrometry | Observed mass compared with the theoretical value |
| Common synonyms | Thymosin beta-4 fragment | Also written as T beta 4 fragment 17-23 |
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.
Lyophilised material is stable for extended periods when kept dry and cold, and suppliers typically recommend storage well below freezing. Once dissolved, the peptide is handled at refrigeration temperatures and used within a short period, because peptide bonds and the acetylated terminus can be affected by repeated freeze-thaw cycles, proteases, or extreme pH. Bacteriostatic water and saline are both described as solvents, although preservatives can interfere with some analytical workflows. Reconstituted solutions are inspected for particulates before use.
Sports authorities classify the peptide as a prohibited substance, and it appears on the World Anti-Doping Agency list under peptide hormones, growth factors, and related substances. Racing jurisdictions for horses and dogs have issued separate restrictions, and several national bodies treat it as a controlled or prescription-only item. As a research chemical it is sold without a therapeutic indication, and labels usually state that the product is not for human or veterinary use. Regulatory treatment therefore varies by country.
The CUX1 gene Alternatively Spliced Product was first reported in 1997. The CUX1 gene has up to 33 exons. CASP mRNA includes exons 1 through 14 and 25 through 33. The human CASP protein is predicted to contain 678 amino acids, of which 400 are shared with CUTL1. CASP protein is approximately 80 kD. It lacks the DNA binding region of CUTL1, but instead contains a trans-membrane domain that allows it to insert into lipid bilayers. It has been localized to the Golgi apparatus. CASP has been reported to be part of a complex with Golgin 84 that tethers COPI vesicles and is important for retrograde transport in the Golgi and between the Golgi and endoplasmic reticulum. The targeting of vesicles involves tethers and SNAREs.
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=== Microchimerism === Microchimerism of fetal cells (offspring lymphoid cells in maternal circulation) may generate autoimmunity in women who have previously been pregnant. Generation of an autoimmune potential via microchimerism may lead to a switch from a silent form of autoimmunity with age-dependent decrease in self-tolerance.
Sources: en.wikipedia.org
The Celtic Boii settled there and the region was first mentioned on the map of Ptolemaios in the 2nd century AD. The Germanic tribe of the Marcomanni dominated the entire core of the region in later centuries. Those tribes already built cities like Brno, but moved west during the Migration Period. In the 7th century AD Slavic people moved in and were united under Samo's realm. Later in the High Middle Ages Germans settled into the less populated border region.
== Committees of the People's Assembly == Within the People's Assembly, there are several committees responsible for discussing and approving legislation proposed by the People's Assembly regarding a specific field related to these committees. These committees were formed by a 17-member special committee formed by People's Assembly speaker Abdul Hamid al-Awak, and is responsible with drafting laws regarding the internal regulations of the People's Assembly, such as the formation and election of committees, and holding sessions of the People's Assembly. In total, there are currently 26 committees of the People's Assembly; these committees were formed on 30 July 2026, after the second session of the 22nd People's Assembly.
==== OXA-48-like carbapenemases ==== The spread of OXA-48 carbapenem resistance involves both the expansion of successful bacterial clones and the movement of blaOXA-48 between bacteria on mobile genetic elements. The gene is commonly associated with Tn1999-family transposons carried on highly conjugative IncL plasmids, although OXA-48-like genes also occur in other plasmid types and chromosomal contexts. A community outbreak in New Zealand during 2018–2022 involved 25 patients with OXA-48-producing Escherichia coli sequence type 131. Eighteen patients had visited the same community food premises, where four food handlers were also found to be colonized, and whole-genome sequencing demonstrated genomic links between patient and food-handler isolates. Subsequent long-read genomic analysis found that the outbreak lineage had acquired blaOXA-48 on a 7,872-base-pair Col156 plasmid and identified a single IS1-mediated transposition of the resistance gene into the Col156 plasmid backbone. Analysis of global genomic data showed that blaOXA-48 occurs in diverse plasmid and insertion-sequence contexts among Enterobacterales.
Sources: en.wikipedia.org
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StoreDot is a developer of lithium-ion (Li-ion) batteries for electric vehicles founded in 2012 by Doron Myersdorf, Simon Litsyn, and Gil Rosenman. It is based in Herzliya, Israel. The company was founded around developing peptide-based mobile phone displays and data storage. The company reported it was ready to commercially release these products: peptide-based displays by 2016; peptide-based batteries for mobile phones that fully charge in 30 seconds by 2016; germanium-based mobile phone batteries by 2019; electric car and aerial drone batteries that fully charge in five minutes by 2020; scooter batteries that fully charge in under five minutes by 2021; and silicon-graphite-electrode batteries in 2025. None of the aforementioned products have been commercially released as of February 2026. Financial journalists estimated in February 2026 that StoreDot has funding for a few more months of operations. StoreDot stated in 2026 it needs two more years of development in order to commercialize its product.
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Sources: en.wikipedia.org
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.
It corresponds to the actin-binding region of thymosin beta-4. Commercial synthesis reproduces that seven-residue stretch, usually with an acetyl group on the N-terminus.
It is not authorised as a medicine in the United States or the European Union and is distributed as a research chemical. Labels consequently carry research-use-only statements rather than clinical indications.
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.