Everything below concerns thymosin beta-4. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-08-29. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Name type | Commercial trade name | Not a systematic chemical identifier |
| Parent peptide | Thymosin beta-4 | 43-residue natural peptide |
| Common fragment sequence | LKKTETQ | Maps to part of the actin-binding region |
| Molecular size class | Roughly 0.8-1.0 kDa | Depends on exact fragment and terminal modification |
| Regulatory status | Prohibited in sport | Grouped with peptide hormones in many frameworks |
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.
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.
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.
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.
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.
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.
The use of additional manipulation tools may be needed to organize 3D co-cultures into a configuration similar enough to native tissue architecture. Endothelial cells (PEC), smooth muscle cells (SMC), fibroblasts (PF), and epithelial cells (EpiC) cultured through magnetic levitation can be sequentially layered in a drag-and-drop manner to create bronchioles that maintain phenotype and induce extracellular matrix formation. Below is a list of cell types (primary and cell lines) that have been successfully cultured by the magnetic levitation method.
In addition to regulating the experiments that were conducted, the guidelines also forbade the performance of other experiments. One such experiment was the cloning of recombinant DNAs derived from highly pathogenic organisms. In addition, neither the cloning of DNA containing toxin genes nor large-scale experiments using recombinant DNAs that were able to make products that were potentially harmful to humans, animals, or plants were allowed under the guidelines. These experiments were banned because the potential biohazards could not be contained by the then-current safety precautions.
Infant formulas made with soy protein phytoestrogens are considered safe alternatives to formulas containing dairy ingredients, which may be excluded for infants with galactosemia and hereditary lactose intolerance. Some reviews express the opinion that more research is needed to answer the question of what effect phytoestrogens may have on infants, but their authors did not find any adverse effects. Studies conclude there are no adverse effects in human growth, development, or reproduction as a result of the consumption of soy-based infant formula compared to conventional cow-milk formula. The American Academy of Pediatrics states: "although isolated soy protein-based formulas may be used to provide nutrition for normal growth and development, there are few indications for their use in place of cow milk-based formula. These indications include (a) for infants with galactosemia and hereditary lactase deficiency (rare) and (b) in situations in which a vegetarian diet is preferred."
There have been a variety of long-overlap-based assembly methods developed in recent years. One of the most commonly used methods, the Gibson assembly method, was developed in 2009, and provides a one-pot DNA assembly method that does not require the use of restriction enzymes or integrases. Other similar overlap-based assembly methods include Circular Polymerase Extension Cloning (CPEC), Sequence and Ligase Independent Cloning (SLIC) and Seamless Ligation Cloning Extract (SLiCE). Despite the presence of many overlap assembly methods, the Gibson assembly method is still the most popular. Besides the methods listed above, other researchers have built on the concepts used in Gibson assembly and other assembly methods to develop new assembly strategies like the Modular Overlap-Directed Assembly with Linkers (MODAL) strategy, or the Biopart Assembly Standard for Idempotent Cloning (BASIC) method.
Sources: en.wikipedia.org
3. Int J Pharm Compd. 2026 Jul-Aug;30(4):329-336. Synthetic Peptides in Pharmacy Compounding: Analysis of PCAC Recommendations and Industry Safety Standards. Willis J(1), Vu N(2)(3). Author information: (1)University of Oklahoma College of Pharmacy. (2)ARL Bio Pharma, Oklahoma City, Oklahoma. Nvu@arlok.com. (3)University of Oklahoma College of Pharmacy, Oklahoma City, Oklahoma. Compounded peptides have quickly moved from a niche topic to a growing area of interest among patients and prescribers. These products are promoted for a wide range of uses, including tissue repair, inflammation, metabolic health, and healthy aging. This article examines the proposed uses of these peptides, the concerns raised during the review, and the practical implications for compounders. Copyright© by International Journal of Pharmaceutical Compounding, Inc.
In an effort to prevent incidents such as the disappearance of Malaysia Airlines Flight MH370, a new standard has been issued requiring all commercial aircraft to report their position every 15 minutes to air traffic controllers regardless of the country of origin. Introduced in 2016 by the ICAO, the regulation has no initial requirement for any new aircraft equipment to be fitted. The standard is part of a long-term plan, called the Global Aeronautical Distress and Safety System (GADSS), which will require new aircraft to be equipped with data broadcast systems that are in constant contact with air traffic controllers. The GADSS is similar to the Global Maritime Distress and Safety System (GMDSS) used for maritime safety.
In May 2023, the FDA approved the iLet Bionic Pancreas system for people with Type 1 diabetes of six years and older. The device uses a closed-loop system to deliver both insulin and glucagon in response to sensed blood glucose levels. The 4th generation iLet prototype, presented in 2017, is around the size of an iPhone, with a touchscreen interface. It contains two chambers for both insulin and glucagon, and the device is configurable for use with only one hormone, or both. A 440-patient study of type I diabetes ran in 2020 and 2021 using a device configuration that delivered only insulin in comparison to standard of care; device use led to better circulating glucose control (measured by continuous monitoring) and a reduction in glycated hemoglobin (versus no change for the standard of care group). However, the incidence of severe hypoglycemic events was more than 1.5 times higher among device users versus standard care patients. There are several non-commercial, non-FDA approved DIY options, using open source code, including OpenAPS, Loop, and/or AndroidAPS.
Sources: pubmed.ncbi.nlm.nih.gov
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.
Published work usually examines actin binding, cell migration and tissue repair endpoints in cell and animal models. Findings are generally described as preliminary, and controlled human data remain limited.
Because TB-500 is a trade name rather than a chemical identifier, different vendors and papers may attach it to different fragment lengths. Checking the stated sequence is the practical way to resolve the ambiguity.
TB-500 is a trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.