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 2025-10-02. 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.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
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.
| 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 |
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
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.
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.
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.
== Drug pricing issue and exit in the Swiss market == In July 2025, Roche withdrew Lunsumio from the Swiss market following failed price negotiations with the Swiss Federal Office of Public Health (BAG). The drug had been available since February 2023 through a special "Early Access" program that allowed reimbursement before complete clinical data was available. Under this arrangement, Roche initially covered treatment costs until efficacy was demonstrated, after which the remaining therapy could exceed 100,000 Swiss francs. When Swissmedic extended the temporary authorization in February 2025 due to still-missing complete clinical data from Phase III studies, Roche rejected the previously negotiated pricing model and demanded higher prices. The BAG refused to modify the agreement, citing concerns that exceptions would set a precedent for other pharmaceutical companies and demanding additional efficacy evidence despite the drug showing positive effects in Phase II studies. According to Swissmedic pricing data, a single 60-mg dose (two vials) of Lunsumio costs over 7,000 Swiss francs. The withdrawal was announced to oncologists on July 1, 2025, affecting approximately 24 patients annually who suffer from follicular lymphoma—a slowly progressing cancer of the lymph nodes with about 500 new cases per year in Switzerland. Roche also refused to provide individual case reimbursements—a standard Swiss mechanism for exceptional medical situations.
=== mzXML === mzXML is an XML-based common file format for proteomics mass spectrometric data, developed at the Seattle Proteome Center/Institute for Systems Biology while the HUPO-PSI was trying to specify the standardized mzData format. As of 2026, it is still used by members of the proteomics community.
Tomato – in culinary terms, the tomato is regarded as a vegetable, but it is botanically classified as a fruit and a berry. Banana – the fruit has been described as a "leathery berry". In cultivated varieties, the seeds are diminished nearly to non-existence. Pepo – berries with skin that is hardened: cucurbits, including gourds, squash, melons. Hesperidium – berries with a rind and a juicy interior: most citrus fruit. Cranberry, gooseberry, redcurrant, grape. The strawberry, regardless of its appearance, is classified as a dry, not a fleshy fruit. Botanically, it is not a berry; it is an aggregate-accessory fruit, the latter term meaning the fleshy part is derived not from the plant's ovaries but from the receptacle that holds the ovaries. Numerous dry achenes are attached to the outside of the fruit-flesh; they appear to be seeds but each is actually an ovary of a flower, with a seed inside. Schizocarps are dry fruits, though some appear to be fleshy. They originate from syncarpous ovaries but do not actually dehisce; rather, they split into segments with one or more seeds. They include a number of different forms from a wide range of families, including carrot, parsnip, parsley, cumin.
Sources: en.wikipedia.org
== Structure and function == GMP synthase forms a tetramer in an open box shape, which is a dimer of dimers. The R interfaces are held together with a hydrophobic core and a beta sheet, while the P dimer interfaces do not have a hydrophobic core and are more variable than the R interfaces. This enzyme also binds several ligands, including phosphate, pyrophosphate, AMP, citrate and Magnesium.
=== Radiation processes === Some proponents for the authenticity of the Shroud of Turin have argued that the image on the shroud was created by some form of radiation emission at the "moment of resurrection". However, the STURP member Alan Adler has stated that this theory is not generally accepted as scientific, given that it runs counter to the laws of physics, while agreeing that the darkening of the fabric could be produced by exposure to light (and predicting that despite the fact that the Shroud is normally stored in darkness and rarely displayed, it will eventually become darker in the future). Raymond Rogers also criticized the theory, saying: "It is clear that a corona discharge (plasma) in air will cause easily observable changes in a linen sample. No such effects can be observed in image fibers from the Shroud of Turin. Corona discharges or plasmas made no contribution to image formation." Even if ultraviolet radiation were proven to have formed the image, it cannot be proven that it was not natural, that of the sun, applied to the prepared cloth unevenly to create the image. Others have hypothesized that an earthquake after Jesus’ death could have released a burst of neutrons that irradiated the shroud and changed some of the nuclei to different isotopes by neutron capture.
Although the dissolution of the Soviet Union ended the Cold War in 1991 and greatly reduced the political tensions between the United States and Russia, the Soviet Union's formal successor state, both countries remained in a "nuclear stand-off" due to the continuing presence of a very large number of deliverable nuclear warheads on both sides. Additionally, the end of the Cold War led the United States to become increasingly concerned with the development of nuclear technology by other nations outside of the former Soviet Union. In 1995, a branch of the U.S. Strategic Command produced an outline of forward-thinking strategies in the document "Essentials of Post–Cold War Deterrence". In 1995, a Black Brant sounding rocket launched from the Andøya Space Center caused a high alert in Russia, known as the Norwegian Rocket Incident. The Russians thought it might be a nuclear missile launched from an American submarine. In 1996, a Russian continuity of government facility, Kosvinsky Mountain, which is believed to be a counterpart to the US Cheyenne Mountain Complex, was completed. It was designed to resist US earth-penetrating nuclear warheads, and is believed to host the Russian Strategic Rocket Forces alternate command post, a post for the general staff built to compensate for the vulnerability of older Soviet era command posts in the Moscow region. In spite of this, the primary command posts for the Strategic Rocket Forces remains Kuntsevo in Moscow and the secondary is the Kosvinsky Mountain in the Ural Mountains.
Neuroendocrinology is the branch of biology (specifically of physiology) which studies the interaction between the nervous system and the endocrine system; i.e. how the brain regulates the hormonal activity in the body. The nervous and endocrine systems often act together in a process called neuroendocrine integration, to regulate the physiological processes of the human body. Neuroendocrinology arose from the recognition that the brain, especially the hypothalamus, controls secretion of pituitary gland hormones, and has subsequently expanded to investigate numerous interconnections of the endocrine and nervous systems. The endocrine system consists of numerous glands throughout the body that produce and secrete hormones of diverse chemical structure, including peptides, steroids, and neuroamines. Collectively, hormones regulate many physiological processes. The neuroendocrine system is the mechanism by which the hypothalamus maintains homeostasis, regulating reproduction, metabolism, eating and drinking behaviour, energy utilization, osmolarity and blood pressure.
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.
No. Thymosin beta-4 is a 43-residue protein, while TB-500 refers to a seven-residue fragment corresponding to its N-terminal region. The two names are often used loosely in commercial and community writing, which obscures the difference in size, sequence, and likely behavior.