Everything below concerns actin binding. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-09-13. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
| 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 |
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.
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.
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.
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.
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.
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.
=== 20 January === At least 11 people were killed by RSF shelling on the Abu Shouk IDP camp in El Fasher. A coalition of SAF and allied forces claimed to have repelled two RSF incursions from Libya in North Darfur near the tri-border area with Chad and Libya, killing a total of over 950 fighters, destroying 61 vehicles, and capturing 78 others that were equipped with advanced weaponry.
== Gene expression == During hair growth, as follicle bulb cells swiftly transform into cortical or cuticle hair keratinocytes, approximately 50-100 keratin genes become activated at the transcriptional level. However, this intricate process can be simplified into a few highly preserved gene families. In cortical keratinocytes, distinct patterns of keratin gene expression are evident, indicating the presence of different hierarchical transcription processes among various cell types. Examination of keratin gene promoter regions reveals conserved sequence motifs that might govern these cell-specific traits. Moreover, through the isolation of related sheep and human cuticle keratin genes, conserved DNA motifs and expression patterns during cuticle cell differentiation have been discovered. Further, the expression of sheep wool follicle IF and high-sulfur keratin genes in transgenic mice suggests that the regulatory DNA elements and proteins associated with hair keratin genes maintain functional conservation across mammalian species.
=== Phylloxera === There have been several theories proposed for why the phylloxera was ignored as the possible cause of the disease that resulted in the failure of so many vineyards, most of which involve the feeding behaviour of the insect, and the way it attacks the roots. The proboscis of the grape phylloxera has both a venom canal from which it injects its deadly venom and a feeding tube through which it takes in vine sap and nutrients. As the toxin from the venom corrodes the root structure of a vine, the sap pressure falls and, as a result, the Phylloxera quickly withdraws its feeding tube and searches for another source of food. Thus, anyone digging up a diseased and dying vine will not find Phylloxera clinging to the roots of the plant.
Further action is planned for Saturday, the day of the FA Cup Final, and on Friday by members of RMT. A huge wildfire covering 30 mi2 (78 km2), possibly the largest ever seen in the UK, is brought under control by the Scottish Fire and Rescue Service at Cannich in the Highlands.
). Another factor that impacts total CPU time needed by a simulation is the size of the integration timestep. This is the time length between evaluations of the potential. The timestep must be chosen small enough to avoid discretization errors (i.e., smaller than the period related to fastest vibrational frequency in the system). Typical timesteps for classical MD are on the order of 1 femtosecond (10−15 s). This value may be extended by using algorithms such as the SHAKE constraint algorithm, which fix the vibrations of the fastest atoms (e.g., hydrogens) into place. Multiple time scale methods have also been developed, which allow extended times between updates of slower long-range forces. For simulating molecules in a solvent, a choice should be made between an explicit and implicit solvent. Explicit solvent particles (such as the TIP3P, SPC/E and SPC-f water models) must be calculated expensively by the force field, while implicit solvents use a mean-field approach. Using an explicit solvent is computationally expensive, requiring inclusion of roughly ten times more particles in the simulation. But the granularity and viscosity of explicit solvent is essential to reproduce certain properties of the solute molecules. This is especially important to reproduce chemical kinetics. In all kinds of molecular dynamics simulations, the simulation box size must be large enough to avoid boundary condition artifacts.
Sources: en.wikipedia.org
With this support and the 1897 reorganization upon moving into its new home, the Library of Congress began to grow and develop more rapidly. Librarian Spofford's successor John Russell Young overhauled the library's bureaucracy, used his connections as a former diplomat to acquire more materials from around the world, and established the library's first assistance programs for the blind and physically disabled, with the establishment of the National Library Service for the Blind and Print Disabled. Librarian Young's successor Herbert Putnam held the office for forty years of the 20th century from 1899 to 1939. Two years after he took office, the library became the first in the United States to hold one million volumes. Putnam focused his efforts to make the library more accessible and useful for the public and for other libraries. He instituted the interlibrary loan service, transforming the Library of Congress into what he referred to as a "library of last resort". Putnam also expanded library access to "scientific investigators and duly qualified individuals", and began publishing primary sources for the benefit of scholars. During Putnam's tenure, the library broadened the diversity of its acquisitions. In 1903, Putnam persuaded President Theodore Roosevelt to use an executive order to transfer the papers of the Founding Fathers from the State Department to the Library of Congress. Putnam also expanded foreign acquisitions, including the 1904 purchase of a 4,000-volume library of Indica, the 1906 purchase of G. V.
Ádám István Mechler is a materials scientist and academic most known for his research on intermolecular interactions in physical chemistry, as well as on molecular machines, hierarchical metamaterials, and self-assembling systems inspired by biology. He is a professor of Chemistry at La Trobe University, Australia, where he leads the Bioinspired self-assembling nanostructures research group. He is also the Academic Program Director of the IIT Kanpur - La Trobe University Research Academy and the BITS Pilani - La Trobe University joint PhD program.
== Structural studies == As of late 2007, 34 structures have been solved for this class of enzymes, with PDB accession codes PDB: 1IX1, PDB: 1LM4, PDB: 1LM6, PDB: 1LME, PDB: 1LQW, PDB: 1LQY, PDB: 1LRU, PDB: 1LRY, PDB: 1N5N, PDB: 1Q1Y, PDB: 1S17, PDB: 1SV2, PDB: 1SZZ, PDB: 1V3Y, PDB: 1VEV, PDB: 1VEY, PDB: 1VEZ, PDB: 1WS0, PDB: 1WS1, PDB: 1XEM, PDB: 1XEN, PDB: 1XEO, PDB: 1Y6H, PDB: 1ZXZ, PDB: 1ZY0, PDB: 1ZY1, PDB: 2AI7, PDB: 2AI8, PDB: 2AI9, PDB: 2AIA, PDB: 2AIE, PDB: 2EW5, PDB: 2EW6, and PDB: 2EW7.
Monocyte- and macrophage-related cutaneous conditions are characterized histologically by infiltration of the skin by monocyte or macrophage cells, often divided into several categories, including granulomatous disease, histiocytoses, and sarcoidosis.
Sources: en.wikipedia.org
Conversely if the temperature falls the controller acts to close the TCV which reduces the heat transfer increasing the temperature of the first fluid. In the case of heating medium with the falling temperature of the first fluid the controller would act to open the TCV to increase the flow of heating medium thereby raising the temperature of the first fluid. The controller (TIC) may also generate high (TAH) and low temperature (TAL) alarms to warn operating personnel of a potential problem. Fin fan coolers use air to cool gases and liquids. The temperature of fluid is controlled (TIC) by opening or closing dampers on the cooler or adjusting the speed of the fan or the pitch angle of the fan blades thereby increasing or decreasing the flow of air. Temperature monitoring and control instrumentation is used in fired heaters and furnaces to adjust the fuel flow valve (FCV) to maintain a desired thermal output. Waste heat recovery units (WHRU) are used to extract heat from the flow of hot exhaust gases from a gas turbine to heat a fluid (heating medium). Instrumentation includes controllers to maintain a desired temperature of the heating medium by closing or opening dampers in the exhaust gas flow. Low temperature alarms (TSL) are used where cold fluids could be routed to pipework which is not suitable for cold service. Instrumentation may include an initial alarm (TAL) and then a shutdown action (TSLL) to close a shutdown valve (XV).
=== Enlargement === Tarlov cysts are known to have the tendency to enlarge over time. The prominent theory that explains this phenomenon reasons the enlargement of the cysts is due to the cerebrospinal fluid being pushed into the cyst during systole pulsation, but unable to get out during the diastole phase, resulting in enlargement observed in clinical settings over time. Increased ICP from trauma or other injury, childbirth, and overexertion are thought to trigger enlargement along with inflammation and hemorrhagic infiltration. With the cysts often containing a valve like mechanism fluid becomes trapped, and the meningeal sac or nerve sheath grows in size. Some patients have been diagnosed for up to 20 years with little change in size, and those with small stable cysts may avoid much progression of symptoms. Those with generally larger sacral cysts pressed along the sacrum cause the sacrum to become eroded and thin.
Integrin inside-out signaling in leukocytes and platelets correlates with large increases in actin polymerization and cellular shape changes upon activation. Most recently, ligand binding to integrins was shown to induce full conformational change within milliseconds, and to be the first step in integrin inside-out signaling.
== Sources == Isotope masses from: National Nuclear Data Center. "NuDat 3.0 database". Brookhaven National Laboratory. Half-life, spin, and isomer data selected from the following sources. National Nuclear Data Center. "NuDat 3.0 database". Brookhaven National Laboratory. IAEA - Nuclear Data Section. Live Chart of Nuclides. Vienna International Centre. Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.
=== History === Commercial production of ethylene oxide dates back to 1914 when BASF built the first factory which used the chlorohydrin process (reaction of ethylene chlorohydrin with calcium hydroxide). The chlorohydrin process was unattractive for several reasons, including low efficiency and loss of valuable chlorine into calcium chloride. More efficient direct oxidation of ethylene by air was invented by Lefort in 1931 and in 1937 Union Carbide opened the first plant using this process. It was further improved in 1958 by Shell Oil Co. by replacing air with oxygen and using elevated temperature of 200–300 °C (390–570 °F) and pressure (1–3 MPa (150–440 psi)). This more efficient route accounted for about half of ethylene oxide production in the 1950s in the US, and after 1975 it completely replaced the previous methods. The production of ethylene oxide accounts for approximately 11% of worldwide ethylene demand.
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.
No. Thymosin beta-4 is a 43-residue protein, while TB-500 refers to a seven-residue fragment corresponding to its N-terminal region. The two names are often used loosely in commercial and community writing, which obscures the difference in size, sequence, and likely behavior.