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.
Updated 2025-11-23. Numbers and descriptions here follow the published literature rather than marketing material.
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 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.
| 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 |
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 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.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
Literature and online discussion often conflate TB-500 with full-length thymosin beta-4, even though the two differ in size and are not interchangeable in analytical terms. The fragment is produced by solid-phase peptide synthesis, and the product is a defined seven-residue chain rather than a biological extract. Because the term is a trade-style label, two vendors may supply materials of the same nominal sequence but different counter-ion content, purity, or water content. Comparisons across studies are therefore difficult unless the exact sequence and purity are reported.
TB-500 is a research peptide whose sequence matches residues 17 to 23 of thymosin beta-4, a 43-residue protein present in most mammalian cells. The chain is seven amino acids long, written as LKKTETQ, and is normally supplied with an acetyl group on the N-terminus. Suppliers list it as a lyophilised powder under the code name TB-500, and the same sequence appears elsewhere in catalogues as the thymosin beta-4 actin-binding fragment. The label is commercial rather than systematic, so no single authority fixes exactly what TB-500 denotes.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
Identity and purity checks for peptide material typically combine reversed-phase high-performance liquid chromatography with mass measurement, since retention time alone cannot confirm a sequence. Mass measurement verifies the expected molecular mass within instrument tolerance, while chromatographic peak area provides a purity estimate. Anti-doping analysis of urine uses related but more sensitive workflows, sometimes after solid-phase extraction. For research material, batch documentation, certificate content, and independent testing are common points of scrutiny, because supply chains outside pharmaceutical regulation vary widely in the paperwork they provide.
Reconstitution of a lyophilized peptide is normally done with sterile water or a suitable buffer under aseptic conditions. Adding solvent down the vial wall and allowing gentle dissolution instead of vigorous vortexing reduces the chance of aggregation, which can lower the effective concentration of the resulting solution. Concentrated stocks are usually diluted into working buffer shortly before use. Because no standard preparation protocol exists for TB-500 specifically, laboratories adapt general peptide handling practice, and reported results may reflect differing preparation choices.
19 June The PAVN 4th Regiment attacked Firebase Tomahawk occupied by the 2nd Battalion, 501st Infantry Regiment and 2nd Battalion, 138th Artillery. The assault was repulsed for the loss of 13 U.S. (including 9 National Guardsmen from the 138th Artillery) and 23 PAVN killed.
==== Increasing mandatory tests in California ==== Many rare diseases have not historically been tested for or testing that has been available has not been mandatory. One such disease is glutaric acidemia type I, a neurometabolic disease present in approximately 1 out of every 100,000 live births. A short-term California testing pilot project in 2003 and 2004 demonstrated the cost of forgoing rare disease testing on newborns. While both Zachary Wyvill and Zachary Black were both born with the same disease during the pilot program, Wyvill's birth hospital tested only for four state-mandated diseases while Black was born at a hospital participating in the pilot program. Wyvill's disease went undetected for over six months during which irreversible damage occurred but Black's disease was treated with diet and vitamin supplements. Both sets of parents became advocates for expanded neonatal testing and testified in favor of expanding tandem mass spectrometry (MS/MS) testing of newborns for rare diseases. By August, 2004, the California state budget law had passed requiring the use of tandem mass spectroscopy to test for more than 30 genetic illnesses and provided funding. California now mandates newborn screening for all infants and tests for 80 congenital and genetic disorders.
=== Available forms === The dosage should be applied directly to the site where anesthesia is required. The dosage should be modified according to the patient and there has not been a dosage specified for children. Spray: Cetacaine spray should be applied for only one second and dosage should not exceed an application spray longer than 2 seconds. Gel: Use a cotton swab to apply 200 mg to the needed area and the dosage should not exceed 400 mg. Liquid: Apply 200 mg either directly or by using cotton applicator to the location and the dosage should not exceed 400 mg.
There is much research currently underway looking at ways to protect the nerve (neuroprotection) or even regenerate new fibers within the optic nerve. So far there is no evidence in human studies that the so-called neuroprotectors have any beneficial effect in NAION. However, there is a new current clinical trial for the treatment of NAION in the United States with plans to include sites in India, Israel, Germany and Australia (see NORDICclinicaltrials.com and https://clinicaltrials.gov/). This trial will test the use of a synthetic siRNA that blocks caspase 2, an important enzyme in the apoptosis cycle. In addition to such research, patents have been applied for by Pfizer, The University of Southern California, Otsuka Pharmaceutical and other individual inventors for innovations related to the treatment of anterior ischemic optic neuropathy. In recent years, pentoxifylline has emerged as a potential treatment option for NAION and other diseases involving ocular ischemia. Pentoxifylline has been shown to reduce erythrocyte rigidity, resulting in decreased blood viscosity and increased flow velocity. Animal studies have demonstrated that pentoxifylline can inhibit TNF and, in turn, prevent retinal ganglion cell death and axonal degeneration associated with optic neuropathy in a dose-dependent manner.
Sources: en.wikipedia.org
After the start of treatment, cats must be kept indoors for four weeks, and contact with pregnant women and children under the age of 16 must be avoided due to residual radioactivity. Just like a medical practice, any veterinary practice operating an X-ray machine must have sufficient staff with the appropriate expertise, as required by Section 18 of the X-Ray Ordinance 2002. The corresponding training for paraveterinary workers (then called veterinary nurses) took place in 1990. In 2017, Linsengericht (Hesse) opened Europe's first clinic for horses with cancer. Radiation therapy is administered in a treatment room that is eight meters wide, on a specially designed table that can withstand heavyweight. The surrounding area is protected from radiation by three-meter thick walls. Mobile equipment is used to irradiate tumors in small animals at various locations.
== Publication == The first peer reviewed publication describing SEA native peptide ligation was published in Organic Letters by Melnyk, O. et al. (Ollivier, N.; Dheur, J.; Mhidia, R.; Blanpain, A.; Melnyk, O., Bis(2-sulfanylethyl)amino native peptide ligation. Org. Lett. 2010, 12, (22), 5238–41; Publication Date (Web): October 21, 2010. A few weeks later, the same reaction was published in the same journal by Liu, C. F (Hou, W.; Zhang, X.; Li, F.; Liu, C. F., Peptidyl N,N-Bis(2-mercaptoethyl)-amides as Thioester Precursors for Native Chemical Ligation. Org. Lett. 2011, 13, 386–389; Publication Date (Web): December 22, 2010).
== External links == "Opioid Receptors: κ". The International Union of Basic and Clinical Pharmacology, The British Pharmacological Society, The University of Edinburgh. International Union of Basic and Clinical Pharmacology. Archived from the original on 2014-02-23. Retrieved 2007-07-23. kappa+Opioid+Receptor at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
== Natural occurrences == Taxifolin is found in non-glutinous rice boiled with adzuki bean (adzuki-meshi). It can be found in conifers like the Siberian larch, Larix sibirica, in Russia, in Pinus roxburghii, in Cedrus deodara and in the Chinese yew, Taxus chinensis var. mairei. It is also found in the silymarin extract from the milk thistle seeds. Taxifolin is present in vinegars aged in cherry wood. Taxifolin, and flavonoids in general, can be found in many beverages and products. Specifically, taxifolin is found in plant-based foods like fruit, vegetables, wine, tea, and cocoa.
Liraglutide, a GLP-1 receptor agonist taken by subcutaneous injection once daily. Naltrexone/bupropion, a combination of naltrexone and bupropion taken by mouth twice daily. Orlistat is a lipase inhibitor taken by mouth three times daily with each main meal containing fat. Orlistat reduces intestinal fat absorption by inhibiting pancreatic lipase. Over the longer term, average weight loss on orlistat is 2.9 kg (6.4 lb). It leads to a reduced incidence of diabetes, and has some effect on cholesterol. However, there is little information on how it affects the longer-term complications or outcomes of obesity. It also inhibits absorption of fat soluble vitamins; vitamins A, D, E and K, so supplementation is needed for those on orlistat. Phentermine/topiramate combination of phentermine and topiramate taken by mouth once daily. Semaglutide, a GLP-1 receptor agonist taken by subcutaneous injection once weekly. Tirzepatide is a gastric inhibitory polypeptide (GIP) analog and a GLP-1 receptor agonist taken by subcutaneous injection once weekly. As of 2023, tirzepatide has shown the greatest weight reduction of medications. Phendimetrazine, diethylpropion, and phentermine are approved by the FDA for short term use, up to 12 weeks at a time.
Sources: en.wikipedia.org
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.
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.