The short version of thymosin beta-4 fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-09-21 and is reviewed periodically as new material appears.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
Lyophilised peptide powders are hygroscopic, and the fragment absorbs atmospheric moisture when a vial is opened at room temperature. Weighing and aliquoting are normally done quickly in a dry environment, and stock solutions are divided into single-use portions before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and can shift the measured content of a vial. These practices are general to synthetic peptides rather than unique to this sequence, but they matter more for short chains kept for long periods.
The seven-residue chain carries several polar and charged side chains, so it dissolves readily in water and in aqueous buffers near neutral pH. No cysteine is present, so disulphide formation is not a concern and reducing agents are unnecessary. Dilute ammonium hydroxide or acetonitrile-water mixtures are sometimes used for stock solutions when initial dissolution is slow. Strongly alkaline conditions and prolonged contact with oxidising agents are avoided because they can modify lysine-containing stretches, and haze in solution usually signals incomplete dissolution or aggregated material.
Identity and purity are checked with reversed-phase high-performance liquid chromatography, which separates the target sequence from truncated or deletion analogues, and with mass spectrometry, which confirms the expected molecular mass. Amino acid analysis and peptide mapping give orthogonal confirmation but are used less often outside specialist laboratories. Counter-ion content varies: material purified on trifluoroacetic acid gradients retains trifluoroacetate, and ion exchange can convert the salt form. Residual water and solvent are measured by Karl Fischer titration or thermogravimetric analysis, and any purity figure should be read together with the method used to obtain it.
| Property | Value | Notes |
|---|---|---|
| Physical form | Lyophilised powder | Sealed vial; reconstituted before laboratory use |
| Appearance | White to off-white solid | Visual descriptor used on certificates of analysis |
| Solubility class | Water-soluble | Dissolves in water and aqueous buffers |
| Reported mass, fragment | Near 889 Da | Value depends on the stated sequence |
| Reported mass, parent protein | Near 4963 Da | 43-residue thymosin beta-4 |
Purity and identity are separate measurements and are often confused. Reverse-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, reports the share of total peak area belonging to the target compound. Mass spectrometry by electrospray or matrix-assisted laser desorption then checks whether the observed mass matches the expected sequence. Neither measurement alone shows that a vial holds the intended peptide. Peptide content, meaning the fraction of vial mass that is genuine peptide rather than counter-ion, water or residual acid, is reported separately and is frequently lower than the stated purity figure.
The regulatory position is broadly consistent across major jurisdictions: no thymosin beta-4 fragment is an approved medicine, and laboratory material is commonly labelled as not intended for human consumption. Anti-doping rules in sport list thymosin beta-4 and its fragments among prohibited peptide hormones. Because these products travel through research-chemical channels rather than pharmaceutical supply chains, quality varies considerably between vendors. Independent testing of identity, purity and sterility is the only dependable check, and a certificate of analysis describes one batch rather than a supplier's whole catalogue.
Lyophilized peptide powder is normally held desiccated at −20 °C, with −80 °C used for longer storage periods. Allowing a sealed vial to reach room temperature before opening is standard practice, because condensation forming on cold powder introduces moisture. Once dissolved, solutions are typically kept cold and shielded from light. Repeated freeze-thaw cycles are avoided because they encourage aggregation and gradual loss of material. These conventions are general to synthetic peptides rather than unique to any one sequence.
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.
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.
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.
Narrated by actress Miranda Richardson 27 November Dismantling the Bomb, Pantex in Texas; START II in January 1993; Ted Taylor (physicist); eighteen scientists from the UK worked on the Manhattan Project; the plutonium fissile material, which was half the world's supply, for the July Trinity (nuclear test) was carried on the back seat of a car, to be assembled; the bomb was hoisted on 14 July 1945; a warning flare was fired, then the electrical circuits were connected at 5.29am on 16 July 1945; the bomb was dropped twenty one days later, exploding at 1,900 feet; the Russians developed the bomb through the work of Igor Kurchatov and Yulii Khariton; much American nuclear weapon research also took place at Livermore, California; the first British nuclear test, on 3 October 1952, was set up by two people on HMS Plym; many US weapon cores had been made at the Rocky Flats Plant in Colorado; Viktor Mikhailov (politician), Russian minister of nuclear power; the Nuclear Control Institute. Narrated by Scottish actor Tom Cotcher, produced by Chris Haws, directed by Richard Melman, made by InCA Productions 4 December Electric Skies, about lightning at the Langmuir Laboratory for Atmospheric Research; electrical engineer Martin A.
"Attogram sensing of trinitrotoluene with a self-assembled molecular gelator". Journal of the American Chemical Society. 134 (10): 4834–4841. doi:10.1021/ja210728c. PMID 22352376. SS Babu, VK Praveen, Ajayaghosh, Ayyappanpillai (2014). “Functional π-gelators and their applications”. Chem. Rev. 2014, 114, 4, 1973-2129. https://doi.org/10.1021/cr400195e R, D, Mukhopadhyay.; and Ajayaghosh, Ayyappanpillai (2015). “Living supramolecular polymerization”. Science 2015, 349, 241.doi:10.1126/science.aac7422 S, Prasanthkumar.; S, Ghosh.; V, C, Nair.; A, Saeki.; S, Seki.; and Ajayaghosh Ayyappanpillai (2015). “Organic Donor-Acceptor Assemblies to Coaxial p-n Heterojunctions with High Photoconductivity”. Angew. Chem., Int. Ed. 2015, 54, 946-950. https://doi.org/10.1002/anie.201408831. B, Vedhanarayanan.; V, S, Nair.; V, C, Nair.; and Ajayaghosh, Ayyappanpillai (2016). “Formation of Coaxial Nanocables with Amplified Supramolecular Chirality through an Interaction between Carbon Nanotubes and a Chiral p-Gelator”. Angew. Chem., Int. Ed. 2016, 55, 10345-10349. https://doi.org/10.1002/anie.201605354. V, S, Nair.; R, D, Mukhopadhyay.; A, Saeki.; S, Seki.; and Ajayaghosh, Ayyappanpillai (2016). “A p-Gel Scaffold for Assembling Fullerene to Photoconducting Supramolecular Rods: Non-Equilibrium Self-Assembly of C60 in a p-Gel”. Science Advances 2016, 2, e1600142. doi:10.1126/sciadv.1600142 R, D, Mukhopadhyay.; B, Vedhanarayanan.; and Ajayaghosh, Ayyappanpillai (2017). “Creation of 'Rose Petal' and 'Lotus Leaf' Effects on Alumina by Surface Functionalization and Metal Ion Coordination”. Angew.
In the case of the simians, the loss of the ability to make vitamin C may have occurred much farther back in evolutionary history than the emergence of humans or even apes, since it evidently occurred soon after the appearance of the first primates, yet sometime after the split of early primates into the two major suborders Haplorrhini (which cannot make vitamin C) and its sister suborder of non-tarsier prosimians, the Strepsirrhini ("wet-nosed" primates), which retained the ability to make vitamin C. According to molecular clock dating, these two suborder primate branches parted ways about 63 to 60 million years ago. Approximately three to five million years later (58 million years ago), only a short time afterward from an evolutionary perspective, the infraorder Tarsiiformes, whose only remaining family is that of the tarsier (Tarsiidae), branched off from the other haplorrhines. Since tarsiers also cannot make vitamin C, this implies the mutation had already occurred, placing it between these two marker points (63 to 58 million years ago). It has also been noted that the loss of the ability to synthesize ascorbate strikingly parallels the inability to break down uric acid, also a characteristic of primates. Uric acid and ascorbate are both strong reducing agents. This has led to the suggestion that, in higher primates, uric acid has taken over some of the functions of ascorbate.
Sources: en.wikipedia.org
After 137Cs and 90Sr have decayed to low levels, the bulk of radioactivity from spent fuel come not from fission products but actinides, notably plutonium-239 (half-life 24 ka), plutonium-240 (6.56 ka), americium-241 (432 years), americium-243 (7.37 ka), curium-245 (8.50 ka), and curium-246 (4.73 ka). These can be recovered by nuclear reprocessing (either before or after most 137Cs and 90Sr decay) and fissioned, offering the possibility of greatly reducing waste radioactivity in the time scale of about 103 to 105 years. 239Pu is usable as fuel in existing thermal reactors, but some minor actinides like 241Am, as well as the non-fissile and less-fertile isotope plutonium-242, are better destroyed in fast reactors, accelerator-driven subcritical reactors, or fusion reactors. Americium-241 has some industrial applications and is used in smoke detectors and is thus often separated from waste as it fetches a price that makes such separation economic.
Israel is widely believed to possess nuclear weapons, with an estimated stockpile of between 90 and 400 nuclear warheads. Israel is the only nuclear-armed country that does not officially acknowledge its nuclear weapons capability. Some scholars have argued that Israel's nuclear weapons have incentivized Iran to develop its own nuclear program, seen as maintaining a balance of nuclear deterrence, or causing a regional nuclear arms race. Citing security threats, Israel rejects international calls to accede to the Treaty on the Non-Proliferation of Nuclear Weapons or to participate in negotiations of a Middle East nuclear weapon free zone. This has frustrated both US and UK diplomatic efforts towards such a zone. Scholars also suggest US tacit acceptance of the Israeli nuclear weapons capability is seen as a double standard that undermines its diplomatic credibility in Middle East nonproliferation negotiations.
===== Restoration of diplomatic relations ===== On 15 November 2023, Santiago Peña restored diplomatic relations with Venezuela, after the break that occurred in 2019 under the government of Mario Abdo Benítez. Peña recognized Nicolás Maduro as president, stating that Paraguay would reopen its embassy in Caracas and that Venezuela would do the same in Asunción. Peña defended the gradual resumption of relations with Venezuela, but expressed concern over the disqualification of opposition figure María Corina Machado. He justified the rapprochement as part of a regional strategy after speaking with leaders such as Lula da Silva and Gabriel Boric, assuring that Paraguay remains committed to democracy and human rights. Although he ruled out that the decision was linked to Petropar's debt to PDVSA, he acknowledged the possibility of increasing trade with Venezuela if there were guarantees of payment.
The first commercial oil well in Canada became operational in 1858 at Oil Springs, Ontario. Businessman James Miller Williams dug several wells between 1855 and 1858 before discovering a rich reserve of oil four metres below ground. Williams extracted 1.5 million litres of crude oil by 1860, refining much of it into kerosene lamp oil. Williams's well became commercially viable a year before Drake's Pennsylvania operation and could be argued to be the first commercial oil well in North America. The discovery at Oil Springs touched off an oil boom which brought hundreds of speculators and workers to the area. Advances in drilling continued into 1862 when local driller Shaw reached a depth of 62 metres using the spring-pole drilling method. On January 16, 1862, after an explosion of natural gas, Canada's first oil gusher came into production, shooting into the air at a recorded rate of 480 cubic metres (3,000 bbl) per day. By the end of the 19th century the Russian Empire, particularly the Branobel company in Azerbaijan, had taken the lead in production.
Sources: en.wikipedia.org
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.
Naming for research peptides is not standardised, and suppliers sometimes apply the same label to different chain lengths. Certificates of analysis and mass data are the practical way to determine what a given lot contains.
The fragment commonly cited under this label is reported near 889 Da, and the parent protein near 4963 Da. Reported values shift with the exact sequence and with residual counter-ions or water in the sample.
Divide it into single-use aliquots and hold them frozen at -20 °C or below, protected from light. Repeated thawing of one container is the main avoidable source of variability.