If you have been reading about actin binding and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
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.
| 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 |
Laboratory work on thymosin beta-4 describes binding to monomeric actin and effects on cell migration, angiogenesis, and inflammatory signaling in cultured cells. Animal models have examined skin, corneal, and cardiac repair after injury, with outcomes reported mainly in preclinical literature. Most of that evidence concerns the parent protein rather than preparations labelled TB-500, so extrapolation from animal findings to a specific commercial product remains uncertain. Whether the two behave identically in living systems has not been established in controlled human studies.
No major regulatory agency has approved TB-500 for therapeutic use, and it holds no pharmacopoeial monograph. The name appears on the World Anti-Doping Agency prohibited list within the class covering peptide hormones, growth factors, and related substances. Detection in doping control relies on mass spectrometric methods applied to urine, often after preparation steps that concentrate the analyte. Discussion of TB-500 therefore clusters in biochemistry, sports medicine, and anti-doping literature rather than in registered clinical trials.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
Detection in biological matrices generally relies on liquid chromatography coupled with tandem mass spectrometry, because the peptide lacks a convenient ultraviolet chromophore beyond the amide backbone. Immunoassays have been described, but antibodies raised against the fragment can cross-react with the full-length protein or with unrelated peptides, so findings usually require confirmation by a second technique. Sample preparation typically involves protein precipitation followed by solid-phase extraction. Reported detection windows depend on dose, route, matrix, and instrument sensitivity.
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 compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
==== France ==== In May 2025, Dunkin' established its first location in France, in the 2nd arrondissement of Paris. As of now, there are five Dunkin' locations in France, all of them in Île-de-France, and the chain continues to expand.
Human rights in the Soviet Union were severely limited. The Soviet Union was a totalitarian state from 1927 until 1953 and a one-party state until 1990. Freedom of speech was suppressed and dissent was punished. Independent political activities were not tolerated, whether these involved participation in free labour unions, private corporations, independent churches or opposition political parties. The freedom of movement within and especially outside the country was limited. The state restricted rights of citizens to private property.
Fundamentals of Oncology (1997; co‑editors: Miklós Kásler, István Ember, László Kopper, László Thurzó) Dictionary of Epidemiology (2003; co‑editor: Piroska V. Hajdú) The Health Status of the Hungarian Population at the Turn of the Millennium (2003) Preventive Medicine and Public Health (2006, 2012; first and second editions) Public Health Genomics (2013; co‑editors: Judit Sándor, Angela Brand) Public Health in Budapest (2014; co‑editor: Tamás Szentes) Health Diplomacy (2014; co‑editors: Mihály Kökény, Ilona Kickbusch) Public Health Medicine (2015; co‑editors: István Kárpáti, György Paragh) Preventive Services in Primary Care (2017; co‑editor: Magor Papp) Preventive Medicine and Public Health (third edition, 2023; co‑editors: István Kiss, Edit Paulik, János Sándor, Zoltán Ungvári)
Sources: en.wikipedia.org
Though eligible to join the EU's Economic and Monetary Union (EMU), Danish voters in a referendum in 2000 rejected exchanging the krone for the euro. Whereas Denmark's neighbours like Norway, Sweden, Poland and the United Kingdom generally follow inflation targeting in their monetary policy, the priority of Denmark's central bank is to maintain exchange rate stability. Consequently, the central bank has no role in a domestic stabilization policy. In an international context, a relatively large proportion of the population is part of the labour force, in particular because the female participation rate is very high. 78.8% of all 15-to-64-year-olds were active in the labour market in 2017, the sixth-highest number among all OECD countries. With a 4.8% unemployment rate, unemployment is relatively low in comparison to other European countries, where the average unemployment rate is 6.7%. The labour market is traditionally characterized by a high degree of union membership rates and collective agreement coverage. Denmark invests heavily in active labor market policies and the concept of flexicurity has been important historically.
== Applications == HILIC can be applied in many fields including proteomics, metabolomics, medical studies, and agricultural/ food studies, among others. It can be used to separate proteins and peptides, nucleosides, amino acids, sacharides, carbohydrates, and other small, polar, ionizable compounds. HILIC is especially common in metabolomic studies, both for targeted and untargeted approaches, given its ability to retain polar analytes that are poorly suited for traditional reverse-phased columns. This separation technique is also particularly suitable for glycosylation analysis and quality assurance of glycoproteins and glycoforms in biologic medical products. For the detection of polar compounds with the use of electrospray-ionization mass spectrometry as a chromatographic detector, HILIC can offer a ten fold increase in sensitivity over reversed-phase chromatography because the organic solvent is much more volatile. HILIC is considered orthogonal reverse phase chromatography, and these two are increasingly being combined in studies for more comprehensive coverage.
However, the situation might be more complex, since modern computational studies have established that traditional examples of proximity effects cannot be related directly to enzyme entropic effects. Also, the original entropic proposal has been found to largely overestimate the contribution of orientation entropy to catalysis.
=== Purge and trap GC–MS === For the analysis of volatile compounds, a purge and trap (P&T) concentrator system may be used to introduce samples. The target analytes are extracted by mixing the sample with water and purge with inert gas (e.g. Nitrogen gas) into an airtight chamber, this is known as purging or sparging. The volatile compounds move into the headspace above the water and are drawn along a pressure gradient (caused by the introduction of the purge gas) out of the chamber. The volatile compounds are drawn along a heated line onto a 'trap'. The trap is a column of adsorbent material at ambient temperature that holds the compounds by returning them to the liquid phase. The trap is then heated and the sample compounds are introduced to the GC–MS column via a volatiles interface, which is a split inlet system. P&T GC–MS is particularly suited to volatile organic compounds (VOCs) and BTEX compounds (aromatic compounds associated with petroleum). A faster alternative is the "purge-closed loop" system. In this system the inert gas is bubbled through the water until the concentrations of organic compounds in the vapor phase are at equilibrium with concentrations in the aqueous phase. The gas phase is then analysed directly.
Sources: en.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.
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.