If you have been reading about LKKTETQ 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.
Updated 2026-04-28. Numbers and descriptions here follow the published literature rather than marketing material.
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 synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
| 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 |
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.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
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 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.
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.
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.
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.
HPG is synthesized from prephenate, an intermediate in the shikimic acid pathway and also a precursor to tyrosine. Prephenate is aromatized by prephenate dehydrogenase (Pdh) using NAD+ as a cofactor to produce 4-hydroxyphenylpyruvate. 4-Hydroxyphenylpyruvate is then oxidized by 4-hydroxymandelate synthase (4HmaS) using oxygen to form 4-hydroxymandelate and hydrogen peroxide. 4HmaS is a non-heme iron-dependent dioxygenase. The reaction mechanism of this unique oxidation was proposed by Choroba et al in 2000
== Implications == The Father Tongue hypothesis has far-reaching implications for several processes in linguistics such as language change, language acquisition and sociolinguistics. The Father Tongue hypothesis also has implications for language acquisition, as the hypothesis suggests an evolutionary explanation for why females may be better in some aspects of language performance and acquisition. Van Driem interpreted the correlation of Y-chromosomal haplogroups and language families as indicating that the spread of language families was often mediated by male-biased migration, whether these intrusions were martial or something less spectacular. He conjectured that the majority of language communities spoke father tongues rather than mother tongues. The Father Tongue hypothesis has implications for linguists' understanding of language change. It must be assumed that the dynamics of language change whereby mothers pass on the language of their spouses to their offspring differ from the dynamics of language change in a monolingual community and even from the dynamics of change in a bilingual community where mothers pass on their own language to their children. As a consequence, such dynamics can introduce a discontinuity with the past. For example, it has been observed that Michif, genetically an Algonquian language (like Plains Cree), was relexified by Métis women with Métis French, the language of their husbands, and so the genetic affinity of Michif has come to be almost unidentifiable.
=== 1971–1972: Islands === After a search for a drummer to replace McCulloch, Ian Wallace was secured. Fripp was re-energised by the addition of a new member, and he joined Collins and Wallace to audition singers and bassists. Singers who tried out included Bryan Ferry of Roxy Music (Sinfield would produce Roxy Music's first album in 1972) and even one of the band's managers, John Gaydon. The position eventually went to Raymond "Boz" Burrell. John Wetton was invited to join on bass, but declined in order to join Family instead. Rick Kemp (later of Steeleye Span) rehearsed with the band, but declined the final offer to formally join. Fripp decided to teach Burrell to play bass rather than continue the labored auditions. Though he had not played bass before, Burrell had played enough acoustic guitar to assist him in learning the instrument quickly. Wallace was able to further instruct Burrell in functioning on the instrument in a rhythm section.With a line-up now complete, King Crimson began touring in May 1971, the first time they had played live since the original line-up's last show on 14 December 1969. The concerts were well received, but musical differences and the somewhat wilder lifestyles of Collins, Wallace, and Burrell alienated the non-drug-taking Fripp, who began to withdraw socially from his bandmates, creating further tension. In 1971, the new King Crimson formation recorded Islands.
Sources: en.wikipedia.org
McArdle disease (GSD-V) is inherited in an autosomal recessive manner. If both parents are carriers (not having the disease, but each parent having one copy of the mutated allele), then each child of the couple will have a 25% chance of being affected (having McArdle disease), a 50% chance of being a carrier, and a 25% chance of being unaffected (neither a carrier nor diseased). Two autosomal recessive forms of this disease occur, childhood-onset and adult-onset. The gene for myophosphorylase, PYGM (the muscle-type of the glycogen phosphorylase gene), is located on chromosome 11q13. According to the most recent publications, 95 different mutations have been reported. The forms of the mutations may vary between ethnic groups. For example, the R50X (Arg50Stop) mutation (previously referred to as R49X) is most common in North America and Western Europe, and the Y84X mutation is most common among central Europeans. The exact method of protein disruption has been elucidated in certain mutations. For example, R138W is known to disrupt to pyridoxal phosphate binding site. In 2006, another mutation (c.13_14delCT) was discovered which may contribute to increased symptoms in addition to the common Arg50Stop mutation.
The New Zealand Parliament is a unicameral legislature made up of the monarch and the House of Representatives. A "member of Parliament" is a member of the House of Representatives, which has a minimum of 120 members, elected at a general election for a three-year term. There are 72 electorate MPs, of which seven are elected only by Māori who have chosen to be registered on a separate Māori electoral roll. The remaining members are elected by proportional representation from published party lists. Since 1907, members of the House of Representatives have been referred to as "Member of Parliament", abbreviated MP. From the 1860s until 1907 they were designated as "Member of the House of Representatives", abbreviated MHR. Between the first general election, in 1853, and the 1860s, the designation was "Member of the General Assembly", abbreviated MGA. Before 1951, New Zealand had an upper house, the Legislative Council, whose members were appointed.
=== Hemorrhagic Infiltration === Many authors state that blood and its breakdown products acting as foreign-body substance in the subarachnoid space produce local adhesive arachnoiditis with no symptoms, but it also can create cystic degeneration. The subarachnoid space abhors all foreign body substances. Even the presence of injected air is considered to be a "foreign body". Blood definitely is considered a foreign body, particularly in its breakdown products. Repeated exposure to foreign body substances in the subarachnoid space or spinal injury can initiate auto-immune amnestic reactions which may potentiate and magnify the ongoing inflammatory process causing cystic cavitation in spinal tissue.
Sources: en.wikipedia.org
=== 23 January === Polish Prime Minister Mateusz Morawiecki stated that Poland will provide 14 Leopard tanks to Ukraine regardless of Germany's approval; the next day, Poland officially requested permission to export them. German Defence Minister Boris Pistorius encouraged other countries to provide training on the tanks for Ukrainian soldiers. French President Emmanuel Macron stated that France would send Leclerc tanks to Ukraine. Norwegian defence chief General Eirik Kristoffersen stated that around 180,000 Russian soldiers were dead or wounded and there were around 100,000 military casualties and 30,000 civilian dead from Ukraine.
The company was founded in Pittsburgh, Pennsylvania, in 1902 by Chester Garfield Fisher (1881–1965), originally called the "Scientific Materials Co.". After obtaining his degree in engineering at Western University of Pennsylvania (now University of Pittsburgh), C.G. Fisher purchased the stockroom of the Pittsburgh Testing Laboratory. Fisher became a supplier of lab equipment and reagents for the area's industrial research. Early products included microscopes, burets, pipettes, litmus, balances, colorimeters, dissecting kits, and anatomical models. The first catalog, the 400 page Scientific Materials Co. Catalog of Laboratory Apparatus & Supplies, was published in 1904. Fisher established an R&D lab at his company in 1915. Edwin Fisher, Chester's brother, developed the Meker-Fisher burner in 1921, an advancement on the design of the Bunsen burner. The company manufactured an electric-combustion furnace and combustion train for analyzing carbon levels in steel, and an electrically heated and thermostatically controlled bacteriological incubator. In 1925, the company purchased Montreal-based Scientific Supplies, Ltd. The same year, the company was renamed Fisher Scientific. In 1940, Fisher Scientific acquired the New York supply company Eimer & Amend, which was founded in 1851 by Bernard G. Amend. Aiken Fisher, Chester's oldest son, became president of the company in 1949. In 1955, Fisher established a chemical manufacturing facility in Fair Lawn, New Jersey. In 1957, the company purchased the New York–based medical apparatus supply company E. Machlett & Sons.
== Examples == β-Amino acids with a wide variety of substituents exist. Named by analogy to the biological α-amino acids, the following have been found naturally: β-alanine, β-leucine, β-lysine, β-arginine, β-glutamate, β-glutamine, β-phenylalanine and β-tyrosine. Of these, β-alanine is found in mammals and incorporated in pantothenic acid, an essential nutrient. Aspartic acid is structurally a β-amino acids. Microcystins are a class of compounds containing a β-isoaspartyl (i.e. aspartic acid linked with its beta-carboxyl) residue.
The atheroma ("lump of gruel", from Greek ἀθήρα (athera) 'gruel'), which is the nodular accumulation of a soft, flaky, yellowish material at the center of large plaques, composed of macrophages nearest the lumen of the artery Underlying areas of cholesterol crystals Calcification at the outer base of older or more advanced lesions. Atherosclerotic lesions, or atherosclerotic plaques, are separated into two broad categories: Stable and unstable (also called vulnerable). The pathobiology of atherosclerotic lesions is very complicated, but generally, stable atherosclerotic plaques, which tend to be asymptomatic, are rich in extracellular matrix and smooth muscle cells. On the other hand, unstable plaques are rich in macrophages and foam cells, and the extracellular matrix separating the lesion from the arterial lumen (also known as the fibrous cap) is usually weak and prone to rupture. Ruptures of the fibrous cap expose thrombogenic material, such as collagen, to the circulation and eventually induce thrombus formation in the lumen. Upon formation, intraluminal thrombi can occlude arteries outright (e.g., coronary occlusion), but more often they detach, move into the circulation, and eventually occlude smaller downstream branches, causing thromboembolism. Apart from thromboembolism, chronically expanding atherosclerotic lesions can cause complete closure of the lumen. Chronically expanding lesions are often asymptomatic until the lumen stenosis is so severe (usually over 80%) that blood supply to downstream tissue(s) is insufficient, resulting in ischemia.
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.
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.