The short version of Ac-LKKTETQ fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
Identity and purity are checked with chromatographic and mass spectrometric methods. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities, while mass spectrometry confirms the expected molecular mass. A certificate of analysis may report a purity percentage, but the laboratory should still verify the material independently. Common quality concerns include truncated sequences, deamidation, oxidation, and residual solvents from synthesis. Because TB-500 is short, some impurities can differ from the target by only a few mass units.
Reconstitution practices affect downstream measurements. The dry powder is typically dissolved in sterile water or a suitable aqueous buffer, then mixed gently rather than vortexed at high speed. Visible particles or cloudiness suggest incomplete dissolution or contamination and should be investigated. For long-term storage, aliquots should be labeled with concentration, solvent, and date. Open questions include how different buffers alter peptide conformation and whether specific container materials adsorb the peptide. Those variables can change apparent concentration in assays even when the chemical identity is correct.
Lyophilized TB-500 is hygroscopic and should be kept dry before use. The usual storage recommendation for the solid is -20 °C, protected from light and moisture. Once dissolved, the peptide is less stable, and repeated freeze-thaw cycles can promote aggregation or degradation. Laboratories often divide a reconstituted solution into single-use aliquots and store them at -80 °C. Exact stability limits depend on buffer, pH, and concentration, so published data do not define a single universal condition.
| 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 |
Regulatory status differs by country, but TB-500 is not an approved pharmaceutical in major jurisdictions. It is commonly sold as a research chemical for laboratory use, which places responsibility for identity and purity on the supplier and the laboratory. Published human data are limited, and most reports involve preclinical models or cell culture. Questions about whether the fragment mimics all actions of thymosin beta-4, and under which conditions, remain open. Independent verification of any material is therefore a practical requirement in research settings.
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.
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.
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.
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.
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.
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.
The ribosomal tunnel, or peptide tunnel, is a part of the ribosome that holds the nascent polypeptide chain during translation. The ribosomal tunnel is located in the large subunit of the ribosome and connects the catalytic site of the ribosome with its surface.
In Peranakan cuisine across Maritime Southeast Asia, fish maw is a traditional Chinese New Year food. The ingredient features particularly in hee pio soup (a.k.a. hu pioh t'ng), a clear soup of fish maw paired with a varied selection of other vegetables and proteins. In Thailand, a Thai cuisine fish maw dish is kaeng tai pla (Thai: แกงไตปลา), a Southern Thai fishermen dish featuring tai pla, fermented fish maw. Krapaw pla is a Thai-Chinese fish maw stew in a red braise. Vietnamese cuisine does not typically feature fish maw, but fish maw is sometimes featured in xúp cua, a Vietnamese crab soup (súp cua bong bóng cá).
== Role in bone decomposition == Diagenesis alters the proportions of organic collagen and inorganic components (hydroxyapatite, calcium, magnesium) of bone exposed to environmental conditions, especially moisture. This is accomplished by the exchange of natural bone constituents, deposition in voids or defects, adsorption onto the bone surface and leaching from the bone.
She has released two albums on the Karaoke Kalk label: Kids with Sticks in 2001 and the collaboration Kuchen Meets Mapstation in 2003 with Stefan Schneider of To Rococo Rot (who also records as Mapstation). Horner is a film producer based in Newcastle upon Tyne. Browne went on to play with Warm Jets, Rialto, and White Hotel (with Jean-Marc Butty, longtime drummer for PJ Harvey) before briefly returning to Canada in 2001, then relocating to San Francisco in 2002. There she played with local rock noir chanteuse Rykarda Parasol, appearing on her Here She Comes EP and the Our Hearts First Meet album, then went on to record and tour with The Wronglers, an old-time band with Warren Hellman, founder and financer of San Francisco's free Hardly Strictly Bluegrass festival, who also made an album with Jimmie Dale Gilmore called "Heirloom Music".
Sources: en.wikipedia.org
==== 15–16 March ==== On the morning of 15 March, German troops entered the remaining Czech parts of Czechoslovakia (referenced as "Rest-Tschechei" by Nazi Germany), meeting practically no resistance (the only instance of organized resistance took place in Místek where an infantry company commanded by Karel Pavlík fought invading German troops). The Hungarian invasion of Carpatho-Ukraine encountered resistance but the Hungarian army quickly crushed it. On 16 March, Hitler went to the Czech lands and from Prague Castle proclaimed the German protectorate of Bohemia and Moravia. The British historian Victor Rothwell wrote that the Czechoslovak reserves of gold and hard currency seized in March 1939 were "invaluable in staving off Germany's foreign exchange crisis". In addition, the Germans seized all of the factories for making weapons, mines that provided crucial raw materials for the armament program of the Four Year Plan and a "huge weapons haul, including nearly 500 tanks and nearly 1600 aircraft".
Although Tg2576 mice do not perfectly replicate late-stage AD with cell death, they do offer a platform for researching the physiology and biochemistry of the illness. With the help of transgenic mouse models, researchers can make progress in AD research by understanding the intricate relationships between gene products that are involved in the production of Aβ peptide.e physiology and biochemistry of the illness.
Line 14: Since 10 September 2016, the Moscow Central Circle (MCC) renovated railroad (the former Moskovskaya Okruzhnaya Zheleznaya Doroga) has been operated as Line 14 of the Moscow Metro. This cone-shaped railroad opened in 1908 (as a freight-only railway from 1934 until the reopening in 2016). Line 11: Another circular metro line—the Big Circle Line (Bolshaya Koltsevaya Liniya)—opened its first stations in 2018 and the remaining stations in 2023. The Kakhovskaya-Savyolovskaya western half of the line was launched in late 2021. The outermost ring within the city is the Moscow Ring Road—often called the MKAD, an acronym for the Russian Московская Кольцевая Автомобильная Дорога—which forms the city's cultural boundary; it was established during the 1950s. It was built at ground level, rather than being elevated, so it forms a barrier to roads that would otherwise pass beneath it. (Before Moscow's 2012 expansion, the MKAD was considered an approximate city boundary.) Outside Moscow, some roads encompassing the city follow the same circular pattern as within city limits; notable examples are the Betonka roads (highways A107 and A108), originally constructed of concrete pads. To reduce traffic on the MKAD, a new ring road—called CKAD, Centralnaya Koltsevaya Avtomobilnaya Doroga, Central Ring Road—was completed outside the MKAD in 2021.
glutathione + a lactate The catalysis of S-lactoylglutathione hydrolysis by glutathione thiolesterase has been noted in Saccharomyces cerevisiae. Additionally, human red blood cells have been found to contain at least four separate glutathione thiol esterases. The enzymes found supported the potential substrate activity of S-lactoylglutathione and S-propionylglutathione.
== Contraindications == The only absolute contraindication to the use of ivermectin is hypersensitivity to the active ingredient or any component of the formulation. In children under the age of five or those who weigh less than 15 kilograms (33 pounds), there is limited data regarding the efficacy or safety of ivermectin, though the available data demonstrate few adverse effects. However, the American Academy of Pediatrics cautions against use of ivermectin in such patients, as the blood–brain barrier is less developed, and thus there may be an increased risk of particular CNS side effects such as encephalopathy, ataxia, coma, or death. The American Academy of Family Physicians also recommends against use in these patients, given a lack of sufficient data to prove drug safety. Ivermectin is secreted in very low concentration in breast milk. It remains unclear if ivermectin is safe during pregnancy.
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.
The dry powder is normally kept at -20 °C, protected from light and moisture. Reconstituted solutions are often divided into aliquots and stored at -80 °C to reduce freeze-thaw damage.