The short version of thymosin beta-4 fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-05-13 and is reviewed periodically as new material appears.
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.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
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.
Purity and identity are separate measurements and are often confused. Reverse-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, reports the share of total peak area belonging to the target compound. Mass spectrometry by electrospray or matrix-assisted laser desorption then checks whether the observed mass matches the expected sequence. Neither measurement alone shows that a vial holds the intended peptide. Peptide content, meaning the fraction of vial mass that is genuine peptide rather than counter-ion, water or residual acid, is reported separately and is frequently lower than the stated purity figure.
The regulatory position is broadly consistent across major jurisdictions: no thymosin beta-4 fragment is an approved medicine, and laboratory material is commonly labelled as not intended for human consumption. Anti-doping rules in sport list thymosin beta-4 and its fragments among prohibited peptide hormones. Because these products travel through research-chemical channels rather than pharmaceutical supply chains, quality varies considerably between vendors. Independent testing of identity, purity and sterility is the only dependable check, and a certificate of analysis describes one batch rather than a supplier's whole catalogue.
Lyophilized peptide powder is normally held desiccated at −20 °C, with −80 °C used for longer storage periods. Allowing a sealed vial to reach room temperature before opening is standard practice, because condensation forming on cold powder introduces moisture. Once dissolved, solutions are typically kept cold and shielded from light. Repeated freeze-thaw cycles are avoided because they encourage aggregation and gradual loss of material. These conventions are general to synthetic peptides rather than unique to any one sequence.
| Property | Value | Notes |
|---|---|---|
| Physical form | Lyophilised powder | Sealed vial; reconstituted before laboratory use |
| Appearance | White to off-white solid | Visual descriptor used on certificates of analysis |
| Solubility class | Water-soluble | Dissolves in water and aqueous buffers |
| Reported mass, fragment | Near 889 Da | Value depends on the stated sequence |
| Reported mass, parent protein | Near 4963 Da | 43-residue thymosin beta-4 |
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
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.
=== Regulatory steps === Food may be contaminated during all stages of food production and retailing. In order to prevent viral contamination, regulatory authorities in Europe have enacted several measures:
Freeman's sole film release of 2010 was Red with co-stars Bruce Willis, Helen Mirren, and John Malkovich. Red is loosely adapted from the comic-book series Red, created by Warren Ellis and Cully Hamner and published by the DC Comics imprint Homage. Freeman plays CIA mentor Joe, who helps retired fellow agent Frank (Willis) to uncover some assassins. The film was a critical and commercial success; writing for Melbourne's The Age, Jim Schembri praised Freeman and the cast who "bring an infectious comic energy to their roles". Besides film, Freeman worked on other projects. In January 2010, he replaced Walter Cronkite as the voiceover introduction to the CBS Evening News presented by Katie Couric. CBS gave the need for consistency in introductions for regular news broadcasts and special reports as the basis for the change. Deborah Myers, head of Science Channel, approached Freeman to be the presenter of Through the Wormhole (2010–17). She had heard that he was "really interested in space and the universe", and the pair agreed to develop the series together. In 2011, Freeman narrated the fantasy Conan the Barbarian and appeared in the family drama Dolphin Tale, as prosthetic specialist Dr. McCarthy. Returning to theater in 2011, Freeman was featured with John Lithgow in the Broadway debut of Dustin Lance Black's play, 8, a staged reenactment of Perry v. Brown, the federal trial that overturned California's Proposition 8 ban on same-sex marriage. Freeman played Attorney David Boies.
Larger species are mostly nestbrooding (making a nest of vegetation at the water surface), and the dwarfs mostly paternal mouthbrooding, but exceptions occur; the large C. barca is a paternal mouthbrooder and the dwarf C. bleheri is a free-spawner (the eggs float to the surface where the parents take care of them, but they do not mouthbrood or built a nest). Some species in the Channa gachua group also provision their offspring with trophic eggs. Females of Channa andrao and C. gachua have been observed releasing unfertilised eggs above newly hatched larvae, which consume the eggs. Similar trophic-egg provisioning has been observed in several other species of the C. gachua group, suggesting that the behaviour may be widespread within the group.
The three substrates of this enzyme are saccharopine, oxidised nicotinamide adenine dinucleotide (NAD+), and water. Its products are L-lysine, reduced NADH, α-ketoglutaric acid, and a proton. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is N6-(L-1,3-dicarboxypropyl)-L-lysine:NAD+ oxidoreductase (L-lysine-forming). Other names in common use include lysine-2-oxoglutarate reductase, dehydrogenase, saccharopine (nicotinamide adenine dinucleotide,, lysine forming), epsilon-N-(L-glutaryl-2)-L-lysine:NAD oxidoreductase (L-lysine, forming), N6-(glutar-2-yl)-L-lysine:NAD oxidoreductase (L-lysine-forming), 6-N-(L-1,3-dicarboxypropyl)-L-lysine:NAD+ oxidoreductase, and (L-lysine-forming). This enzyme participates in lysine biosynthesis and lysine degradation.
Sources: en.wikipedia.org
=== Inflammatory bowel disease === High red and processed meat consumption is associated with an increased risk of inflammatory bowel disease. The American Gastroenterological Association have stated that a diet low in red and processed meat may reduce ulcerative colitis flares.
=== Mechanism of action === Plecanatide works as a laxative by drawing water in to the gastrointestinal tract thereby softening stool and encouraging its natural passage. Similar to its endogenous counterpart, plecanatide activates guanylate cyclase-C on endothelial cells within the gastrointestinal tract. The activation of guanylate cyclase-C catalyses the production of the second messenger guanosine 3’,5’-cyclic monophosphate (cGMP) which leads to the protein kinase A (PKA) and protein kinase G II (PKGII)-mediated phosphorylation of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CFTR is an anion channel and upon activation it will secrete negatively charged ions, particularly chloride (Cl−) and bicarbonate (HCO3−) in to the GI tract lumen. This disruption to the electrochemical gradient is in part rectified by the passive secretion of positively charged sodium ions in to the lumen and water follows by osmosis. Plecanatide is also known to have an anti-nociceptive effect in animal models, however the exact mechanism of action is not yet fully elucidated. It has been suggested that this may be in part to the anti-inflammatory action of guanylate cyclase-C by its inhibition of pro-inflammatory cytokines, or through the inhibition of associated sensory neurons.
=== Other endurance sports === In triathlon, 2004 Hawaii Ironman winner Nina Kraft, was disqualified for a positive test to EPO. She remains the only Hawaii Ironman winner to be disqualified for doping offences. Sports lawyer Michelle Gallen has said that the pursuit of doping athletes has turned into a modern-day witch-hunt.
Sources: en.wikipedia.org
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.
Naming for research peptides is not standardised, and suppliers sometimes apply the same label to different chain lengths. Certificates of analysis and mass data are the practical way to determine what a given lot contains.
The fragment commonly cited under this label is reported near 889 Da, and the parent protein near 4963 Da. Reported values shift with the exact sequence and with residual counter-ions or water in the sample.
Desiccated storage at −20 °C is conventional, with −80 °C for extended periods. Vials should be warmed to room temperature before opening to prevent condensation on the powder.