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 2026-03-30 and is reviewed periodically as new material appears.
Discussion of the compound frequently appears alongside other short peptides described as fragments of larger proteins. That grouping is convenient but can be misleading, because fragment length, charge, and modification state determine how a peptide behaves in solution and in any experimental system. A seven-residue acetylated peptide and a full-length protein differ in mass by roughly an order of magnitude, and they cannot be assumed to share distribution or binding properties. Precision about which molecule is under discussion is the single most useful step when reading such material.
TB-500 is a shorthand label used in supplier catalogs and online discussion for a short synthetic peptide described as a fragment of thymosin beta-4. Most product listings present it as the N-terminally acetylated heptapeptide Ac-LKKTETQ, a sequence corresponding to the actin-binding region of the parent protein. The name is not a formal chemical designation and does not appear in standard nomenclature systems. Because labeling practices vary between vendors, two products sold under the same name may not contain the same molecule, and the stated sequence should be treated as a claim rather than a fixed definition.
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.
| Property | Value | Notes |
|---|---|---|
| Reported sequence | Ac-LKKTETQ | Described in most listings as the actin-binding region of thymosin beta-4 |
| Reported molecular weight | Approximately 889 Da | Value shifts with the stated sequence; compare against the certificate of analysis |
| Parent protein length | 43 amino acids | Thymosin beta-4; the fragment covers only a small part of it |
| Common synonyms | TB4 fragment; thymosin beta-4 fragment | Trade-style names rather than formal nomenclature |
| Formal monographs | Not established | Labeling conventions differ by supplier and region |
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
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.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
Thymosin beta-4 itself is a small, widely expressed protein that sequesters monomeric actin and participates in cell migration, angiogenesis, and tissue repair. Researchers have examined the shortened fragment as a possible mimic of some of these activities, reasoning that the actin-binding motif lies within the first few residues. Binding to monomeric actin has been observed in cell-free systems. Whether the fragment reproduces the broader effects of the full protein in living tissue remains an open question, and findings from animal models are frequently cited without a clear bridge to human physiology.
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.
=== Medicine === Ether was once used in pharmaceutical formulations. A mixture of alcohol and ether, one part of diethyl ether and three parts of ethanol, was known as "spirit of ether", Hoffman's Anodyne or Hoffman's Drops. In the United States this concoction was removed from the Pharmacopeia at some point prior to June 1917, as a study published by William Procter, Jr. in the American Journal of Pharmacy as early as 1852 showed that there were differences in formulation to be found between commercial manufacturers, between international pharmacopoeia, and from Hoffman's original recipe. It was also used to treat hiccups through instillation into the nasal cavity.
The proton:neutron ratio is not the only factor affecting nuclear stability. It depends also on evenness or oddness of its atomic number Z, neutron number N and, consequently, of their sum, the mass number A. Oddness of both Z and N tends to lower the nuclear binding energy, making odd nuclei, generally, less stable. This remarkable difference of nuclear binding energy between neighbouring nuclei, especially of odd-A isobars, has important consequences: unstable isotopes with a nonoptimal number of neutrons or protons decay by beta decay (including positron emission), electron capture, or other less common decay modes such as spontaneous fission and cluster decay. Most stable nuclides are even-proton-even-neutron, where all numbers Z, N, and A are even. The odd-A stable nuclides are divided (roughly evenly) into odd-proton-even-neutron, and even-proton-odd-neutron nuclides. Stable odd-proton-odd-neutron nuclides are the least common.
== Products and services == Railway freight: Rolling stock, components (bogies, couplers, locomotive shells, gears); Railway transit: Rolling stock (electric locomotives, EMU trainsets, DEMU trainsets, metros, body shells, bogies, propulsion & electrical equipment); Automobile: Commercial electric vehicles, commercial vehicle load bodies; Containers: Marine container, refrigerated container, truck mounted container & cold chain transport container
The most common and widely known tempeh is made from fermented soybeans, called tempeh kedele or tempeh dele, made from controlled fermentation of soybeans. However, traditionally other ingredients such as ampas tahu (tofu dregs/okara), ampas kelapa (coconut dregs) and peanuts may be used in a fashion similar to the tempeh-making process, although perhaps using different fungi or attracting other microbes like kara benguk or kara pedhang, which can be toxic if not prepared correctly. A related product to tempeh is oncom, which is made from peanut press cake or soy dregs and is prevalent in Sundanese culture in West Java. There are two types of oncom: a bright red-orange kind with Neurospora sitophila, and a black one with the same fungi as tempeh uses.
In 1927, fossils of an ancient wild species of cow, Hanaizumi Moriushi (Leptobison hanaizumiensis), dating from the Paleolithic period about 20,000 years ago, were discovered at the Hanaizumi Site in Ichinoseki City, Iwate Prefecture. The Hanaizumi Moriushi is a species similar to the bison and is said to be close to the steppe bison (Bison priscus) lineage. Fossil bones of Aurochs (Bos primigenius) have also been found in Ichinoseki City. Since Hokkaido and Honshu were land-locked with the Eurasian continent during the Ice Age, these animals came from the continent via Hokkaido. In addition, projectile points made from polished wild cattle bones have been found at the same site, although in small quantities, suggesting that humans existed during this period and that Hanaizumi Moriushi and aurochs were hunted. At the Ohama Site in Goto City, Nagasaki Prefecture, cattle teeth dating to the middle Yayoi period were excavated. Among them were also processed cattle molars. However, this excavation was controversial because it contradicted the statement in Chen Shou's Records of the Three Kingdoms (Wajinden) that there were no cattle or horses in Japan. Later, radiocarbon dating of the excavated cattle molars yielded a date of around 40 AD (±90 years).
Sources: en.wikipedia.org
== Structure == LH is a heterodimeric glycoprotein. Each monomeric unit is a glycoprotein molecule; one alpha and one beta subunit make the full, functional protein. Its structure is similar to that of the other glycoprotein hormones, follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and human chorionic gonadotropin (hCG). The protein dimer contains 2 glycopeptidic subunits (labeled alpha- and beta- subunits) that are non-covalently associated:
Coating defines the biocompatibility of the therapeutic agent and its ability to travel in the body. When the agent is not biocompatible, it will quickly be excreted from the body, and there will be magnetic accumulation or off-target therapeutic effects. The use of organic or inorganic coating molecules increases the half-life of the nanocarrier by delaying its clearance by the reticuloendothelial system (RES). This delay occurs because the coating overcomes the pH, hydrophobicity, and surface charge of the magnetic nanoparticles. Additionally, coating allows molecules to covalently bind to specific molecules, such as ligands, proteins, or antibodies, which provides binding specificity to target tissues. A common structure of coating includes the core-shell structure. In this structure, metal oxide cores are coated with biocompatible materials which allows for increased control and biocompatibility. The most common coatings used for optimum response involve the use of polysaccharides like dextran and polymers like polyethylene glycol. Furthermore, carbon coatings have proved to be biocompatible and have high capacity for absorption into cells. Even polyaniline with anti-cancer agent epirubicin can be used for tumor exploration of the brain. Polyethyleneimine has displayed high cellular accumulation and low toxicity. This coating was found to have poor pharmacokinetic properties when used alone, but with magnetic field induction, it was found to accumulate on tumors at clinically significant rates.
=== T-boxes === These elements are bound by specific uncharged tRNAs and modulate the expression of corresponding aminoacyl-tRNA synthetase operons. High levels of uncharged tRNA promote the anti-terminator sequence leading to increased concentrations of charged tRNA. These are considered by some to be a separate family of riboswitches but are significantly more complex than the previous class of attenuators.
=== Critical addiction studies === Some historians and sociologists have suggested that the meanings and uses attributed to anti-craving medicine, such as naltrexone, are context-dependent. Studies have suggested the use of naltrexone in drug courts or healthcare rehabs is a form of "post-social control," or "post-disciplinary control," whereby control strategies for managing offenders and addicts shift from imprisonment and supervision toward more direct control over biological processes.
=== Mammalian === BCATs in mammals catalyze the first step in branched-chain amino acid metabolism, a reversible transamination followed by the oxidative decarboxylation of the transamination products α-ketoisocaproate, α-keto-β-methylvalerate, and α-ketoisovalerate to isovaleryl-CoA, 3-methylbutyryl-CoA, and isobutyryl-CoA, respectively. This reaction regulates metabolism of amino acids and is a crucial step in nitrogen shuttling throughout the whole body. Branched-chain amino acids (BCAA) are ubiquitous in many organisms, comprising 35% of all proteins and 40% of the amino acids required in all mammals. Mammalian BCATs come in two isoforms: cytosolic (BCATc) and mitochondrial (BCATm). The isoforms share 58% homology, but vary in location and catalytic efficiency.
Sources: en.wikipedia.org
Most listings describe it as a short acetylated peptide with the sequence Ac-LKKTETQ, presented as a region of thymosin beta-4. The label is a trade-style name rather than a standardized chemical name, so the exact content of a given vial depends on the supplier.
No. Thymosin beta-4 is a protein of 43 amino acids, while TB-500 is described as a short fragment of it. The two differ in size, structure, and the range of interactions each can support.
Naming for research peptides is not centrally coordinated, so vendors set their own labels and specifications. Differences in stated sequence, molecular weight, or purity documentation usually trace back to those independent labeling choices.
TB-500 is a trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.