This is a working overview of LKKTETQ, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-05-24 and is reviewed periodically as new material appears.
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.
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.
| 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 |
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.
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.
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.
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.
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.
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.
Certain lithium compounds, also known as lithium salts, are used as psychiatric medication, primarily for bipolar disorder and for major depressive disorder. Lithium is taken orally (by mouth). Common side effects include increased urination, shakiness of the hands, and increased thirst. Serious side effects include hypothyroidism, diabetes insipidus, and lithium toxicity. Blood level monitoring is recommended to decrease the risk of potential toxicity. If levels become too high, diarrhea, vomiting, poor coordination, sleepiness, and ringing in the ears may occur. Lithium is teratogenic and can cause birth defects at high doses, especially during the first trimester of pregnancy. The use of lithium while breastfeeding is controversial; many international health authorities advise against it, and the long-term outcomes of perinatal lithium exposure have not been studied. The American Academy of Pediatrics lists lithium as contraindicated for pregnancy and lactation. The United States Food and Drug Administration (FDA) categorizes lithium as having positive evidence of risk for pregnancy and possible hazardous risk for lactation. Lithium salts are classified as mood stabilizers. Lithium's mechanism of action is not known. In the nineteenth century, lithium was used in people who had gout, epilepsy, and cancer. Its use in the treatment of mental disorders began with Carl Lange in Denmark and William Alexander Hammond in New York City, who used lithium to treat mania from the 1870s onwards, based on now-discredited theories involving its effect on uric acid.
Substantial cephalopelvic disproportion Unfavorable fetal position or presentation (e.g., transverse lies) undeliverable without conversion before delivery Obstetric emergencies where maternal or fetal risk-to-benefit ratio favors surgery Fetal distress when delivery is not imminent Umbilical cord prolapse Uterine activity fails to progress adequately Hyperactive or hypertonic uterus Vaginal delivery is contraindicated (e.g., invasive cervical carcinoma, active genital herpes infection, total placenta previa, vasa previa, cord presentation or prolapse) Uterine or cervical scarring from previous cesarean section or major cervical or uterine (e.g., transfundal) surgery Unengaged fetal head History of hypersensitivity to oxytocin or any ingredient in the formulation
=== Gene mutations === Several gene mutations have been identified in patients with camptocormia. These include the RYR1 gene in axial myopathy, the DMPK gene in myotonic dystrophy, and genes related to dysferlinopathy and Parkinson's disease. These genes could serve as targets for gene therapy to treat the condition in the years to come.
A major part of EU law, and most of the EU's budget, concerns public regulation of enterprise and public services. A basic norm of the Treaty on the Functioning of the EU, in article 345, is that the "Treaties shall in no way prejudice the rules in Member States governing the system of property ownership", meaning the EU remains neutral between private or public ownership, but that it can require common standards. In the cases of education and health, member states generally organise public services and the EU requires free movement. There is a unified European Central Bank that funds private banks, and adopts a common monetary policy for price stability, employment and sustainability. The EU's policies on energy, agriculture and forestry, transport and buildings are crucial to end climate damage and shift completely to clean energy that does not heat the planet. Among these, 33% of the entire EU budget is spent on agricultural subsidies to farm corporations and owners. The EU also has an increasing number of policies to raise standards for communications, the internet, data protection, and online media. It has limited involvement in the military and security, but a Common Foreign and Security Policy.
On 27 August 2025, President Luiz Inácio Lula da Silva signed Decree No. 12,595/2025, establishing the DTV+ system (also called TV 3.0) as the new standard for Brazilian free-to-air television, based on ATSC 3.0. The standard covers physical, transport, video, audio, subtitles and emergency alert layers. The preparatory phase is expected to be completed in 2025, with the first TV 3.0 transmissions beginning in the first half of 2026 in major capitals. The expansion process to reach coverage across the entire national territory is estimated to take up to 15 years. The system also incorporates internet integration, greater interactivity, accessibility and public services via the television platform. The signing of the decree followed years of studies, research, discussions and debates led by the MCom, involving companies in the sector, academics and specialists. Following the regulation, Brazilian broadcasters may begin implementing the new system. According to the minister of communications, Frederico Siqueira, the signing of the decree marked a historic moment for Brazil, strengthening free-to-air television as a democratic and popular meeting space. He highlighted that TV 3.0 will not change a central principle: free access. The new technology will modernize Brazilian digital television, offering 4K and 8K images, immersive sound, greater interactivity and integration with the internet. The goal is to provide a richer and more personalized experience for viewers, bringing free-to-air television closer to streaming services.
Sources: en.wikipedia.org
Among the Buddhists there was a Tocharian (Tho-gar) king called Men-dre, or Polosi, or Ānandavarmā. He had the caves painted by restorers and painters: Mitradatta; Naravāhanadatta from the lands of the "naked ones" (Niganthas); Priyaratna from Romakam (Byzantine Empire); and other experts in restoration. The king of the Rgya-ser and King Men-dre's bodies were taken by Amitābha and he went to the land of bliss. When the son of the great king of Rgya-ser came to the fort of Mir-li, thanks to the power of prayer, all the "naked ones" (Niganthas) were killed by the followers of Kālacakra, and all of the Buddhist caves were restored. According to Sam van Schaik, "Mendre" could be the Indo-Greek king Menander, or the mythical king Manadhatṛ of Buddhist sources; "Polosi" could be a Chinese abbreviation for king Prasenajit; "Romakam" may be the Byzantine Empire; the "naked ones" would be the Niganthas. In Tibetan, the country named "Tho-gar" "Thod-kar" corresponds to Tokharistan (ancient Bactria).
Antimicrobial peptides are produced by species across the tree of life, including: bacteria (e.g. bacteriocin, and many others) fungi (e.g. peptaibols, plectasin, and many others) cnidaria (e.g. hydramacin, aurelin) many from insects and arthropods (e.g. cecropin, attacin, melittin, mastoparan, drosomycin, thioester-containing protein 1) amphibia, frogs (magainin, dermaseptin, aurein, and others) birds (e.g. avian defensins) and mammals (e.g. cathelicidins, alpha- and beta-defensins, regIII peptides) Research has increased in recent years to develop artificially-engineered mimics of antimicrobial peptides such as SNAPPs, in part due to the prohibitive cost of producing naturally-derived AMPs. An example of this is the facially cationic peptide C18G, which was designed from the C-terminal domain of human platelet factor IV. Currently, the most widely used antimicrobial peptide is nisin; being the only FDA approved antimicrobial peptide, it is commonly used as an artificial preservative.
=== Radiological hazards === Available evidence suggests that the radiation risk is small relative to the chemical hazard. The primary radiation from pure depleted uranium is due to alpha particles, which do not travel far through air and do not penetrate clothing and skin. However, as uranium-238 decays into its daughter nuclei from its decay series, pure depleted uranium will generate thorium-234 (half-life of ~24 days) followed by protactinium-234 (half life of ~7 hours), which emit more penetrating beta particles at almost the same rate as the uranium emits alpha particles. Total activity then settles to a plateau as the more stable isotope uranium-234 accumulates. A quasi-steady state of roughly 3 times the initial activity is reached within months. Once an equilibrium level of uranium-234 (and its 11 shorter-lived daughter nuclei) has built up after about a million years there will be another radiation plateau at about 14 times the initial activity, finally reaching levels comparable to natural uranium. According to the World Health Organization, radiation dose from DU would be about 60% of that from purified natural uranium with the same mass; the radiological dangers are lower due to its longer half-life and the removal of the more radioactive isotopes. Surveying the veteran-related evidence pertaining to the Gulf War, a 2001 editorial in the BMJ concluded that it was not possible to justify claims of radiation-induced lung cancer and leukaemia in veterans of that conflict.
U+039B Λ GREEK CAPITAL LETTER LAMDA (Λ) U+03BB λ GREEK SMALL LETTER LAMDA (λ) U+1D27 ᴧ GREEK LETTER SMALL CAPITAL LAMDA U+2C96 Ⲗ COPTIC CAPITAL LETTER LAULA U+2C97 ⲗ COPTIC SMALL LETTER LAULA U+A7DA LATIN CAPITAL LETTER LAMBDA U+A7DB LATIN SMALL LETTER LAMBDA U+1038D 𐎍 UGARITIC LETTER LAMDA U+1D6B2 𝚲 MATHEMATICAL BOLD CAPITAL LAMDA U+1D6CC 𝛌 MATHEMATICAL BOLD SMALL LAMDA U+1D6EC 𝛬 MATHEMATICAL ITALIC CAPITAL LAMDA U+1D706 𝜆 MATHEMATICAL ITALIC SMALL LAMDA U+1D726 𝜦 MATHEMATICAL BOLD ITALIC CAPITAL LAMDA U+1D740 𝝀 MATHEMATICAL BOLD ITALIC SMALL LAMDA U+1D760 𝝠 MATHEMATICAL SANS-SERIF BOLD CAPITAL LAMDA U+1D77A 𝝺 MATHEMATICAL SANS-SERIF BOLD SMALL LAMDA U+1D79A 𝞚 MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL LAMDA U+1D7B4 𝞴 MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL LAMDA
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.