This is a working overview of thymosin beta-4, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-11-19. Anything still debated is marked as such rather than presented as settled.
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 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.
| 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 |
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.
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.
== Contraindications == Thiopental should be used with caution in cases of liver disease, Addison's disease, myxedema, severe heart disease, severe hypotension, a severe breathing disorder, or a family history of porphyria. Co-administration of pentoxifylline and thiopental causes death by acute pulmonary edema in rats. This pulmonary edema was not mediated by cardiac failure or by pulmonary hypertension but was due to increased pulmonary vascular permeability.
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Sources: en.wikipedia.org
=== Familial (ATTRm-CM) === This type is caused by mutations of genes encoding amino acids of the transthyretin protein (TTR) causing transthyretin misfolding. Due to the multiple number of potential genetic causes (approximately 130 gene variants are known) the incidence of this form is variable in different populations, depending on the genetic variant. The vast majority of familial cardiac amyloidosis still present after the age of 60. A common mutation is the TTR gene mutation Val122Ile. It is estimated that 3.5–4% of African Americans in the United States have the Val 122lle mutation. This type of amyloidosis can be identified by genetic testing for protein mutation. Histological evaluation involves special stains being utilized to visualize the amyloid deposits. One such stain is Congo Red, which binds specifically to the amyloid deposits and can be characterized by various lighting methods. Under polarized light, the amyloid deposits show characteristic apple green birefringence, and under plain light the deposits will appear a light salmon pink color. Familial amyloidosis usually causes a combination of heart failure and peripheral neuropathy or autonomic neuropathy. Whereas wild-type transthyretin amyloidosis usually causes heart failure, with neuropathy being more rare.
== Toxicity == The recommended therapeutic dose is 80-100 mg/m2 body area. Optimal dosage is determined based on measurements of unbound platinum concentration following intravenous infusion, combined with rate of creatine clearance as an assessment of renal function using Ishibashi’s formula: DoseNDP = AUC × CLNDP, where CLNDP = 0.0738 × creatinine clearance + 4.47 The exact mechanism of uptake into the cell is unknown, with information being considerably less available compared to cisplatin. What is known is that nedaplatin does not interact with the Oct2 or apical multidrug and toxin extrusion transporter (MATE) transporters, potentially explaining the difference in nephrotoxicity due to reduced accumulation in the proximal tubules of the kidney. Toxicogenomics has helped elucidate some of the mechanisms behind nephrotoxicity, where oxidative stress has been shown to deregulate gene expression via Hmox1 and other genes.
=== Melted sample analysis === Methods used to study larger eukaryotes present in sea ice are also used to study other smaller microbes. Regardless of sea ice type, standard practice has been to eventually melt the collected sea ice sample before analysis for convenience. Analytical methods developed to investigate pelagic microbes can readily be applied to these melted sea ice samples. One drawback of this approach is that melting the sea ice exposes microbes accustomed to the hypersaline conditions of brine pockets and channels to significantly fresher water. The melting sea ice contains little-to-no salt, greatly diluting the salt concentration of the liquid phase of the sea ice sample. Osmotic shock and lysis may occur if the salinity decreases too much; additionally, careless warming of the sea ice sample may cause the microbes present to undergo thermal shock. One solution has been to melt the ice into a known volume of seawater kept at subzero temperatures filtered by pelagic microbes. This minimizes the decrease in salinity and drop in temperature and subsequently minimizes the loss of live microbes in the sample. Ice samples colder than –10 °C, however, will still see the loss of over half of the microbial population in the sample when using this approach.
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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. 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.