This is a working overview of research peptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-06-02. Anything still debated is marked as such rather than presented as settled.
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.
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 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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Calculated for the acetylated heptapeptide |
| Molecular weight | ~889 Da | Monoisotopic mass approximately 889.0 Da |
| Amino acid sequence | Ac-LKKTETQ | N-terminal acetylated seven-residue peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Water-soluble | Peptides of this size generally dissolve in aqueous media |
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.
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.
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.
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.
Flutamide has been used to prevent the effects of the testosterone flare at the start of GnRH agonist therapy in men with prostate cancer. The combination of flutamide with an estrogen such as ethinylestradiol sulfonate has been used as a form of combined androgen blockade and as an alternative to the combination of flutamide with surgical or medical castration.
== Dietary concentrations == Detailed reviews on occurrence of CoQ10 and dietary intake were published in 2010. Besides the endogenous synthesis within organisms, CoQ10 also is supplied by various foods. CoQ10 concentrations in various foods are:
== Geography == Sanlúcar de Barrameda is located on the Atlantic coast of the autonomous community of Andalusia, in the province of Cadiz, specifically on the left side of the mouth of the Guadalquivir River, which separates the provinces of Huelva and Seville. The municipality covers an area of 174.3 km2 with 6 km of beaches. The city is part of the tourist area known as the Costa de la Luz (Coast of the Light), about 44 km from the provincial capital of Cádiz. This includes the marshes of the Pinar de la Bonanza Algaida and the marshes of the Guadalquivir, part of the Doñana Natural Park. Sanlúcar de Barrameda borders the municipalities of Trebujena, Jerez de la Frontera, Rota, Puerto de Santa María, and Chipiona. Its topography is shown in the MTN50 sheet (scale 1:50,000) No. 1047 of the National Topographic Map.
Sources: en.wikipedia.org
=== Acute toxicity === Although a low dosis of arenobufagin can be used as a medicine to treat heart rate problems, a high dose can lead to acute heart problems and even death. Arenobufagin is also toxic for hepatocellular carcinoma cells, which is a positive result for the body.
=== 1980–2009: Expansion globally === As the Japanese economy worsened in the 1980s, Ajinomoto sought to outsource more of its production overseas, which increased the number of employees the company employed overseas from 4,000 in 1979 to more than 11,000 in 1996. Starting in 1980, Ajinomoto began to refocus its diversification efforts from food products to its amino acid business. Following the US FDA's re-approval of aspartame in 1981, Ajinomoto began producing the sweetener at its Tokai factory in 1982. In 1987, Ajinomoto began researching drug development in the fields of clinical nutrition, anti-cancer drugs, infectious diseases, and cardiovascular drugs. Through this research, the company developed ELENTAL for use in clinical nutrition, LIVACT to fight liver disease, and Lentinan in collaboration with the Japanese Foundation for Cancer Research. Ajinomoto later released JINO as a cosmetic and amino acid for athletes, followed by Amino Vital, a supplement to JINO released in 1995. In 2000, Ajinomoto acquired NutraSweet and Euro-Aspartame from Monsanto. In December 1995, Ajinomoto's Philippine CEO and President Leonardo K. Ty was assassinated by two members of the communist guerrilla group Alex Boncayao Brigade. The group cited Ty's allegedly poor safety standards for one of his other companies that they claimed to have led to the deaths of several of his employees. Ty had been head of Union Ajinomoto Inc. with his brother Alejandro since the late 1960s, and prior to his death, Ty had been seeking the protection of the National Bureau of Investigation.
Unidirectional chiral inversion (enzyme mediated) was described only with 2-arylpropionate nonsteroidal anti-inflammatory drugs (NSAIDs), namely ibuprofen, ketoprofen, fenoprofen, benoxaprophen, etc. For this group, only S-enantiomer (eutomer) is active i.e. has analgesic and anti-inflammatory effect. In the body, only inactive R-enantiomer can undergo chiral inversion by hepatic enzymes into the active S-enantiomer and not vice versa. The “inactive” R-isomer (distomer) may be responsible for the gastrointestinal irritation and related side-effects associated with NSAIDs. In certain situations, carbenicillin, ethiazide, etoposide, zopiclone, pantoprazole, clopidogrel, ketorolac, albendazole-sulfoxide, lifibrol, and 5-aryl-thiazolidinedione also go through unidirectional chiral inversion. Chiral inversions were found to happen in a group of important compounds called α-amino acids. Amino acids exist in two mirror-image versions (D- and L- configurations). Several D-amino acids, like D-methionine, D-proline, D-serine, D-alanine, D-aspartate, D-leucine, and D-phenylalanine, have been shown to go through unidirectional chiral inversion in mammals. Bidirectional chiral inversion or racemization type of inversion is shown by pharmaceutical drugs including 3-hydroxy-benzodiazapine class of drugs (Oxazepam, lorazepam, temazepam), thalidomide, and tiaprofenic acid. A brief list of select pharmaceutical drugs that go through chiral inversion are presented in Table below..
Sources: en.wikipedia.org
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.
No. Thymosin beta-4 is a 43-amino-acid protein, while TB-500 represents only a short N-terminal segment. The two should not be treated as interchangeable in experimental design.
It is often called a thymosin beta-4 fragment, Tβ4 fragment, or Ac-LKKTETQ. The name TB-500 is mainly a commercial or catalog label rather than a formal chemical name.
No. Thymosin beta-4 is a 43-residue natural peptide, while TB-500 is a commercial label applied to a short synthetic fragment of it. The two differ in length, sequence coverage and how they are handled in the laboratory.