If you have been reading about TB-500 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.
Last reviewed on 2025-10-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
Lyophilised material is stable for extended periods when kept dry and cold, and suppliers typically recommend storage well below freezing. Once dissolved, the peptide is handled at refrigeration temperatures and used within a short period, because peptide bonds and the acetylated terminus can be affected by repeated freeze-thaw cycles, proteases, or extreme pH. Bacteriostatic water and saline are both described as solvents, although preservatives can interfere with some analytical workflows. Reconstituted solutions are inspected for particulates before use.
Sports authorities classify the peptide as a prohibited substance, and it appears on the World Anti-Doping Agency list under peptide hormones, growth factors, and related substances. Racing jurisdictions for horses and dogs have issued separate restrictions, and several national bodies treat it as a controlled or prescription-only item. As a research chemical it is sold without a therapeutic indication, and labels usually state that the product is not for human or veterinary use. Regulatory treatment therefore varies by country.
Detection in biological matrices generally relies on liquid chromatography coupled with tandem mass spectrometry, because the peptide lacks a convenient ultraviolet chromophore beyond the amide backbone. Immunoassays have been described, but antibodies raised against the fragment can cross-react with the full-length protein or with unrelated peptides, so findings usually require confirmation by a second technique. Sample preparation typically involves protein precipitation followed by solid-phase extraction. Reported detection windows depend on dose, route, matrix, and instrument sensitivity.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Analytical method | LC-MS/MS | Preferred confirmatory technique |
| Appearance | White to off-white powder | Lyophilised form |
| Solubility | Freely soluble in water | Also described in saline |
| Storage temperature | Below -20 °C for powder | Short-term refrigeration for solutions |
| Regulatory status | Prohibited in sport | Listed under peptide hormones |
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.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
The American Medical Association (AMA) declared war on Christian Scientists; in 1895 its journal called Christian Science and similar ideas "molochs to infants, and pestilential perils to communities in spreading contagious diseases." Juries were nevertheless reluctant to convict when defendants believed they were helping the patient. There was also opposition to the AMA's effort to strengthen medical licensing laws. Historian Shawn Peters writes that, in the courts and public debate, Christian Scientists and Jehovah's Witnesses linked their healing claims to early Christianity to gain support from other Christians. Vaccination was another battleground. A Christian Scientist in Wisconsin won a case in 1897 that allowed his son to attend public school despite not being vaccinated against smallpox. Others were arrested in 1899 for avoiding vaccination during a smallpox epidemic in Georgia. In 1900 Eddy advised adherents to obey the law, "and then appeal to the gospel to save ...[themselves] from any bad results." In October 1902, after seven-year-old Esther Quimby, the daughter of Christian Scientists, died of diphtheria in White Plains, New York (she had received no medical care and had not been quarantined), the authorities pursued manslaughter charges. The controversy prompted Eddy to declare that "until public thought becomes better acquainted with Christian Science, the Christian Scientists shall decline to doctor infectious or contagious diseases", and from that time the church required Christian Scientists to report contagious diseases to health boards.
==== Sexist remarks ==== On several occasions throughout his third term, Lula, speaking extemporaneously, made comments which were largely regarded as sexist. In May 2024, while announcing measures for those affected by the floods in Rio Grande do Sul, he said that "a washing machine is a very important thing for women". The next day, at a ceremony for the delivery of housing units, he said he had spoken with a 27-year-old woman with 5 children, and asked "When are you going to close the gate, comrade?". At a meeting held in the Palácio do Planalto in July 2024, Lula commented on the result of a study that found that violence against women increases after football matches, concluding: "Unbelievable. If the guy is a Corinthians supporter, that's fine". At the event marking the 2 years since the January 8 attacks, he said "I am a lover of democracy, I am not even a husband, I am a lover of democracy, because, most of the time, lovers are more passionate about their lovers than about their wives". In March 2025, at a ceremony at the Palácio do Planalto, Lula said that he had appointed a "beautiful woman" as Minister of Institutional Relations to get closer to the presidents of the Senate and the Chamber. At the opening of the 29th International Construction and Architecture Fair, held in April 2025, Lula referred disparagingly to the managing director of the International Monetary Fund, Kristalina Georgieva, calling her "a little woman".
== Awards and honors == 1990 - Robert J. and Claire Pasarow Foundation Medical Research Award 1990 - American Association for Cancer Research - G.H.A. Clowes Memorial Award Archived 2017-10-24 at the Wayback Machine 1991 - Honorary doctorate in medicine from Lund University, Sweden 1995 - Nobel Fellow at the Karolinska Institutet in Stockholm 1997 - Gairdner Foundation International Award 1998 - Jacobaeus International Prize 2003 - Jubilee Lecturer, Biochemical Society 2005 - Japan Prize in Cell Biology 2012 - Thomson Reuters Citation Laureate Knight of the Order of the White Rose of Finland Commander of the Order of the Lion of Finland 2022 - Albert Lasker Award for Basic Medical Research. 2023 - Fellow of the American Association for Cancer Research. Member of National Academy of Sciences National Academy of Medicine American Academy of Arts and Sciences European Molecular Biology Organization
According to the North American Mycological Association (NAMA) however, "[i]n humans, no reliably documented cases of death from toxins in these mushrooms [mushrooms that contain isoxazole derivatives] in the past 100 years, though there is one case where a camper froze to death while in the comatose state".
== The role of specific tissues and organs in transamination == Transamination takes place in several tissues and organs, especially the liver and skeletal muscle, which work together to manage amino groups generated during amino acid catabolism. The liver is the primary site of transamination. After proteins are digested into their monomers, amino acids, these amino acids are transported to the liver. In the cytoplasm of hepatocytes, the amino groups from many amino acids are transferred to α-ketoglutarate, forming glutamate in a transamination reaction. Through this process the amino groups from different amino acids are combined into glutamate, reducing the need for multiple enzymes in subsequent elimination or biosynthetic processes. After this transamination reaction, glutamate is transported into the mitochondria, where glutamate dehydrogenase catalyzes an oxidative deamination reaction, releasing ammonium. Free ammonium is toxic to cells, so the liver rapidly converts it to carbamoyl phosphate through a reaction with bicarbonate, allowing it to enter the urea cycle for excretion. The liver also contains aspartate aminotransferase. This enzyme catalyzes a unique reaction where oxaloacetate, instead of α-ketoglutarate, serves as the amino-group acceptor. In this reaction, glutamate transfers an amino group to oxaloacetate, forming the amino acid aspartate and regenerating α-ketoglutarate. Aspartate can then enter the urea cycle, where it combines with citrulline. Skeletal muscles is another site of transamination.
Sources: en.wikipedia.org
The third generation of the Familia Presto was announced in September 1973, a month before the 1973 oil crisis. It was basically an updated version of the 1970 Familia Presto, reintroduced with 60 mm wider bodywork and reworked front and rear designs. It was promoted and marketed as the "Widebody" in Japan. These changes were made only to the saloons and coupé, while the van/wagon and pickups remained in production and retaining the original narrower bodywork with minor changes. The Familia Presto continued using the "Mazda 1000/1300" name in most export markets, "Mazda Marella" name was also retained in Finland. The Rotary Presto saloon/coupé was discontinued in Japan, having been replaced by the larger Grand Familia-based Mazda Savannah. The piston-engined 1000/1300 and rotary-engined R100 coupés were also replaced by 808/818/RX-3 coupé for export market. This generation was not available in North America and replaced by the bigger 808/Mizer/RX-3. Developed to meet new stricter emissions standards in the domestic market, the Presto featured the 1272 cc TC engine or the by now familiar, pushrod 1.0-litre PB unit. Power outputs in Japan (JIS gross) are 62 PS (46 kW; 61 hp) and 87 PS (64 kW; 86 hp) respectively, 50 PS (37 kW; 49 hp) and 66 PS (49 kW; 65 hp) (DIN) for export markets. Production of the third generation Familia ended in January 1977, but not before another minor facelift and emissions scrubbing had taken place in February 1976. This changes were not applied for export market.
Mathematical descriptions of protein-DNA binding taking into account sequence-specificity, and competitive and cooperative binding of proteins of different types are usually performed with the help of the lattice models. Computational methods to identify the DNA binding sequence specificity have been proposed to make a good use of the abundant sequence data in the post-genomic era. In addition, progress has happened on structure-based prediction of binding specificity across protein families using deep learning.
== Non-insulin dependent (type 2) diabetes mellitus == The current releases of the downloadable AIDA software, and AIDA on-line, do not incorporate functions to model endogenous insulin secretion — which takes place in people with non-insulin dependent diabetes mellitus type 2, and healthy subjects without diabetes. Nevertheless, a wide number of people with insulin-treated type 2 diabetes mellitus have reported finding the AIDA diabetes simulator of use for learning about balancing insulin and diet in diabetes. This is because many of the principles of insulin dosage adjustment are remarkably similar in both type 1 and type 2 diabetes mellitus, and even without an endogenous insulin secretion model function, AIDA still can offer realistic simulations (from an educational perspective) for people with non-insulin dependent (type 2) diabetes mellitus. The AIDA developers have published a research paper in 2011 which includes reference to the incorporation of a dedicated function for pancreatic insulin secretion — to be added to a future release of the simulator.
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel forming a blood clot. The process involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation results in hemostasis, the cessation of blood loss from a damaged vessel, allowing repair. Coagulation begins almost instantly after an injury to the endothelium that lines a blood vessel. Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial platelet tissue factor to coagulation factor VII, which ultimately leads to cross-linked fibrin formation. Platelets immediately form a plug at the site of injury; this is called primary hemostasis. Secondary hemostasis occurs simultaneously: additional coagulation factors beyond factor VII (listed below) respond in a cascade to form fibrin strands, which strengthen the platelet plug. Coagulation is highly conserved throughout biology. In all mammals, coagulation involves both cellular components (platelets) and proteinaceous components (coagulation or clotting factors). The pathway in humans has been the most extensively researched and is the best understood. Disorders of coagulation can result in problems with hemorrhage, bruising, or thrombosis.
Sources: en.wikipedia.org
The most common approach is liquid chromatography with tandem mass spectrometry after extraction from blood or urine. Immunoassays exist but are generally treated as screening tools because of cross-reactivity.
Dry lyophilised powder is normally kept frozen and protected from moisture and light. Dissolved material is handled cold and used promptly to limit degradation.
It is not licensed as a medicine in major markets and is distributed as a research chemical. Sports organisations prohibit its use, and some countries restrict import and supply.
Not necessarily. TB-500 is a commercial label that suppliers apply to synthetic peptides described as thymosin beta-4 or a fragment of it. Published research most often studies the full-length protein, so statements about one do not automatically transfer to the other.