A practical reference on thymosin beta-4 fragment: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
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.
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.
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.
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.
Hard and soft acid–base theory (HSAB). This is used mainly for qualitative purposes. Drago and Wayland proposed a two-parameter equation which predicts the standard enthalpy of formation of a very large number of adducts quite accurately. −ΔH⊖ (A − B) = EAEB + CACB. Values of the E and C parameters are available. Guttmann donor numbers: for bases the number is derived from the enthalpy of reaction of the base with antimony pentachloride in 1,2-Dichloroethane as solvent. For acids, an acceptor number is derived from the enthalpy of reaction of the acid with triphenylphosphine oxide.
The majority of early research suggested that the translocation of polycationic CPPs across biological membranes occurred via an energy-independent cellular process. It was believed that translocation could progress at 4 °C and most likely involved a direct electrostatic interaction with negatively charged phospholipids. Researchers proposed several models in attempts to elucidate the biophysical mechanism of this energy-independent process. Although CPPs promote direct effects on the biophysical properties of pure membrane systems, the identification of fixation artifacts when using fluorescent labeled probe CPPs caused a reevaluation of CPP-import mechanisms. These studies promoted endocytosis as the translocation pathway. An example of direct penetration has been proposed for TAT. The first step in this proposed model is an interaction with the unfolded fusion protein (TAT) and the membrane through electrostatic interactions, which disrupt the membrane enough to allow the fusion protein to cross the membrane. After internalization, the fusion protein refolds due to the chaperone system. This mechanism was not agreed upon, and other mechanisms involving clathrin-dependent endocytosis have been suggested. Many more detailed methods of CPP uptake have been proposed including transient pore formation.
For example, Lynda Bonewald determined that osteocytes make FGF23, which travels through the bloodstream to trigger the release of phosphorus by the kidneys. Without enough phosphorus bones and teeth soften, and muscles become weak, as in X-linked hypophosphatemia.
Sources: en.wikipedia.org
Interferon beta-1a (also interferon beta 1-alpha) is a cytokine in the interferon family used to treat multiple sclerosis (MS). It is produced by mammalian cells, while interferon beta-1b is produced in modified E. coli. Some research indicates that interferon injections may result in an 18–38% reduction in the rate of MS relapses. Interferon beta has not been shown to slow the advance of disability. Interferons are not a cure for MS (there is no known cure); the claim is that interferons may slow the progress of the disease if started early and continued for the duration of the disease.
There is an obvious similarity between use of molecular or phenotypic data in the field of cladistics and analyses of morphological characters using a substitution model. However, there has been a vociferous debate in the systematics community regarding the question of whether or not cladistic analyses should be viewed as "model-free". The field of cladistics (defined in the strictest sense) favor the use of the maximum parsimony (MP) criterion for phylogenetic inference. Many cladists reject the position that maximum parsimony is based on a substitution model and (in many cases) they justify the use of parsimony using the philosophy of Karl Popper. However, the existence of "parsimony-equivalent" models (i.e., substitution models that yield the maximum parsimony tree when used for analyses) makes it possible to view parsimony as a substitution model. Even when maximum parsimony is used to construct a tree, substitution models can still play a role in checking the statistical validity of a tree. An example is Sun et al. (2018), where the majority-rule consensus of MP trees is annotated with Bayesian posterior probabilities under the Mk model.
== Biomolecular Analysis Mass Spectrometry == A Biomolecular Analysis Mass Spectrometry (BAMS) facility was officially opened in 2003, headed by Professor Newton and Dr Dudley. It was a collaborative entity between the Department of Biological Sciences and the Medical School. It focused on the study of nucleosides, nucleotides and cyclic nucleotides.
In preparation for the 1998 finals series, and despite losing six of their last eight to the Roos, legendary Essendon coach Kevin Sheedy publicly labelled North executives Greg Miller and Mark Dawson soft in response to comments from commentators that his Essendon team was soft. The Kangaroos beat Essendon in the much-hyped encounter that followed (a Qualifying Final), and North fans pelted Sheedy with marshmallows as he left the ground, although Sheedy was seemingly unfazed by the incident, encouraging a "Marshmallow Game" the next year and relishing in the fact that Sheedy's ulterior motive was to build up the game and draw a large crowd, which proved to be correct, drawing in 71,154 people to attend the game. In 2000, the Bombers thrashed North by 125 points in the 1st Qualifying Final. The biggest VFL/AFL comeback of all time occurred between the two teams when Essendon managed to come back from a 69-point deficit to win by 12 points in 2001. A meeting of the two rivals at the MCG in the 2014 AFL finals series in the 2nd Elimination Final resulted in North winning by 12 points. West Coast – A three-decade rivalry between the Essendon Bombers and the West Coast Eagles kicked off when Essendon coach Kevin Sheedy tied the windsock down on the School End outer terrace so the opposition would not know which way the wind was blowing. Sheedy later said of the incident three decades later, in jest, that it was because the brand sponsor had neglected to pay their account. When West Coast won the toss and kicked against the breeze, it looked as if Sheedy's plan had worked.
Sources: en.wikipedia.org
== Uses == Piperidine is used as a solvent and as a base. The same is true for certain derivatives: N-formylpiperidine is a polar aprotic solvent with better hydrocarbon solubility than other amide solvents, and 2,2,6,6-tetramethylpiperidine is a highly sterically hindered base, useful because of its low nucleophilicity and high solubility in organic solvents. A significant industrial application of piperidine is for the production of dipiperidinyl dithiuram tetrasulfide, which is used as an accelerator of the sulfur vulcanization of rubber.
=== Others === Unlike varenicline (brand name Chantix), naltrexone is not useful for smoking cessation. Naltrexone has also been under investigation for reducing behavioral addictions such as gambling, non-suicidal self-injury disorder, and kleptomania, as well as compulsive sexual behaviors in both offenders and non-offenders (e.g., compulsive porn viewing and masturbation). The results were promising. In one study, the majority of sexual offenders reported a strong reduction in sexual urges and fantasies, which reverted to baseline once the medication was discontinued. Case reports have also shown cessation of gambling and other compulsive behaviors, for as long as the medication was taken. When taken at much smaller doses, a regimen known as low-dose naltrexone (LDN), naltrexone may reduce pain and help to address symptoms of conditions other than those related to addiction. Reports have been published on the usefulness of LDN in the settings of ME/CFS, multiple sclerosis, fibromyalgia, and autoimmune diseases. Although its mechanism of action is unclear, some have speculated that it may act as an anti-inflammatory. As of October 2022, LDN was also being considered as a potential treatment for long COVID.
== History == Delafloxacin was known as ABT-492, RX-3341, and WQ-3034 while it was under development. Rib-X Pharmaceuticals acquired delafloxacin from Wakunaga Pharmaceutical in 2006. Rib-X was renamed to Melinta Therapeutics in 2013. It was developed and marketed by Melinta Therapeutics (formerly Rib-X Pharmaceuticals), which subsequently merged with Cempra. Key clinical trials for delafloxacin have been performed by Melinta regarding indications for skin and skin structure infections as well as complicated bacterial infections and uncomplicated gonorrhea. The trial on gonorrhea was terminated before data was released. Delafloxacin was approved by the FDA in June 2017, after it was noninferior to vancomycin plus aztreonam in two trials on 1042 patients with acute bacterial skin and skin structure infection. New Drug Applications (NDA) for delafloxacin (Baxdela) 450 mg tablets and 300 mg injections were approved by the FDA in June 2017. The FDA obligated Melinta to conduct further studies as follows:
Sources: en.wikipedia.org
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.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
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.