TB-500 is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-04-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
TB-500 is a catalogue name applied to a synthetic peptide related to thymosin beta-4, an actin-binding protein found in most mammalian cells. Suppliers do not use the label consistently: some describe it as the full 43-residue protein, others as a short fragment from the actin-binding region, and others as a related tetrapeptide. Because the name is commercial rather than chemical, two products sold under it may not contain the same molecule. This naming ambiguity is the first point to check in any description of the material.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilized powder | Typical form for short synthetic peptides |
| Solubility class | Freely soluble in water and aqueous buffer | Dissolution aided by gentle mixing, not vigorous shaking |
| Typical storage temperature | −20 °C, desiccated | −80 °C used for long-term holding |
| Common analytical method | Reverse-phase HPLC with UV detection near 214 nm | Identity confirmed separately by mass spectrometry |
| Common synonyms | Thymosin beta-4 fragment; TB4 fragment | Naming varies between suppliers and publications |
Published research on the intact protein is substantial, covering actin regulation, cell migration, and wound models. Research using the heptapeptide fragment specifically is far smaller, and much of the circulating material originates in supplier documentation rather than peer-reviewed reports. Where fragment studies do exist, they often employ different sequences, chain lengths, or terminal modifications, which complicates direct comparison across papers. Readers encountering claims about TB-500 should therefore separate evidence about thymosin beta-4 from evidence about the fragment itself.
Discussion of the compound frequently appears alongside other short peptides described as fragments of larger proteins. That grouping is convenient but can be misleading, because fragment length, charge, and modification state determine how a peptide behaves in solution and in any experimental system. A seven-residue acetylated peptide and a full-length protein differ in mass by roughly an order of magnitude, and they cannot be assumed to share distribution or binding properties. Precision about which molecule is under discussion is the single most useful step when reading such material.
TB-500 is a shorthand label used in supplier catalogs and online discussion for a short synthetic peptide described as a fragment of thymosin beta-4. Most product listings present it as the N-terminally acetylated heptapeptide Ac-LKKTETQ, a sequence corresponding to the actin-binding region of the parent protein. The name is not a formal chemical designation and does not appear in standard nomenclature systems. Because labeling practices vary between vendors, two products sold under the same name may not contain the same molecule, and the stated sequence should be treated as a claim rather than a fixed definition.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
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.
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 synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
== Medical uses == Saxagliptin is used as monotherapy or in combination with other drugs for the treatment of type 2 diabetes. It does not appear to decrease the risk of heart attacks or strokes. One study showed a 3.5% risk of hospitalization for heart failure compared to 2.8% in a placebo-controlled group. Like other DPP-4 inhibitors, it has relatively modest HbA1c lowering ability, is associated with a relatively low risk of hypoglycemia, and does not cause weight gain. Saxagliptin improved mean HbA1c levels (relative to placebo) in a 24-week trial in people with type 2 diabetes. Combination therapy with saxagliptin and metformin was more effective than saxagliptin or metformin monotherapy. When the relative benefits of increasing the dose of a sulfonylurea or adding saxagliptin were assessed in a study of 768 patients, combination treatments were shown to have a significantly greater impact on fasting blood glucose than increasing the tested glibenclamide dose alone.
By establishing the presence of two distinct steps in the process the possibility of identifying the factors involved was established and led on to the identification of the importin family of NLS receptors and the GTPase Ran.
=== Industrial === EDTA is mainly used to sequester (bind or confine) metal ions in aqueous solution. In the textile industry, it prevents metal ion impurities from modifying colours of dyed products. In the pulp and paper industry, EDTA inhibits the ability of metal ions, especially Mn2+, from catalysing the disproportionation of hydrogen peroxide, which is used in chlorine-free bleaching.
=== Lutathera for neuroendocrine tumors === Lutathera is a peptide receptor radioligand/radionuclide therapy (approved by the FDA in 2018) specifically for patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs) that express somatostatin hormone receptors (SSTR). The radioisotope is Lu-177 and the ligand is a SSTR on the surface of tumor cells.
== Interactions == The main IGFBP-3 ligands in the circulation are IGF-1 and IGF-2, and the acid-labile subunit (ALS). The serum proteins transferrin, fibronectin, and plasminogen are also known to bind IGFBP-3. In the cell and tissue environment many other interactions have been described (see Table). Two unrelated cell-surface proteins have been designated as IGFBP-3 receptors: low density lipoprotein receptor-related protein 1 (LRP1), also known as alpha-2-macroglobulin receptor or type V TGFβ receptor and the transmembrane protein TMEM219. Both are believed to mediate antiproliferative effects. Functional interactions with the EGF receptor and the type I/type II TGFβ receptor system have also been reported, and other cell-surface proteins such as proteoglycans also bind IGFBP-3. IGFBP-3 can enter cells by both clathrin-mediated and caveolin-mediated endocytosis. possibly involving the transferrin receptor. IGFBP-3 enters the cell nucleus by a mechanism that is incompletely understood, but involves its binding to importin-β. Within the nucleus, it can modulate nuclear hormone receptor activity by direct binding to retinoid X receptor, retinoic acid receptor, vitamin D receptor, PPARγ, and nur77, IGFBP-3 also interacts with DNA-dependent protein kinase within the nucleus to promote the repair of DNA damage. IGFBP3 has been shown to interact with:
Sources: en.wikipedia.org
Some studies report increased depressive symptoms and anxiety, potentially linked to the sensitization of the hypothalamic-pituitary-adrenal (HPA) axis and elevated cortisol levels. Others find no association or even reduced symptoms. Copper IUDs confer an increased risk of longer, heavier, and/or more painful menstrual periods.
Silicosis is the most common occupational lung disease worldwide. Because of work-exposure to silica dust, silicosis is an occupational hazard to construction, railroad, demolition, mining, sandblasting, quarry, tunnelling, ceramics and foundry workers, as well as grinders, stone countertop fabricators, refractory brick workers, tombstone workers, workers in the oil and gas industry, pottery workers, fiberglass manufacturing, glass manufacturing, flintknappers and others. Brief or casual exposure to low levels of crystalline silica dust do not produce clinically significant lung disease. In the United States, it is estimated that between one and two million workers have had occupational exposure to crystalline silica dust and 59,000 of these workers will develop silicosis sometime in the course of their lives. In the US between 1995 and 2004, there was an annual recorded average of roughly 30 silicosis-related deaths. In the UK, the latest data from The Health and Safety Executive show that there are typically between 10 and 20 annual silicosis deaths in recent years, with an average of 12 per year over the last 10 years. There has been a recent rise of cases in Australia, China and the United States associated with the manufacture and installation of engineered stone surfaces in kitchens and bathrooms. Engineered stone has become increasingly common, and it contains a very high proportion of silica, more than natural stone.
Of the two fungal groups with the largest number of species in Malaysia, the Ascomycota and their asexual states have been surveyed in some habitats (decaying wood, marine, and freshwater ecosystems, as parasites of some plants, and as agents of biodegradation), but have not been or have been only poorly surveyed in other habitats (as endobionts, in soils, on dung, as human and animal pathogens); the Basidiomycota are only partly surveyed: bracket fungi, mushrooms and toadstools have been studied, but Malaysian rust and smut fungi remain little known. Without a doubt, many more fungal species in Malaysia are yet to be recorded, and it is likely that many of those, when found, will be new to science.
== Occurrence == Quercetin is a flavonoid widely distributed in nature. The name has been used since 1857, and is derived from quercetum (oak forest), after the oak genus Quercus. It is a naturally occurring polar auxin transport inhibitor. Quercetin is one of the most abundant dietary flavonoids, with an average daily consumption of 25–50 mg.
C-value enigma Also C-value paradox. A term used to describe a diverse variety of questions regarding the immense variation in nuclear C-value or genome size among eukaryotic species, in particular the observation that genome size does not correlate with the perceived complexity of organisms, nor necessarily with the number of genes they possess; for example, many single-celled protists have genomes containing thousands of times more DNA than the human genome. This was considered paradoxical until the discovery that eukaryotic genomes consist mostly of non-coding DNA, which lacks genes by definition. The focus of the enigma has since shifted to understanding why and how eukaryotic genomes came to be filled with so much non-coding DNA, and why some genomes have a higher gene content than others.
Sources: en.wikipedia.org
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.
Not necessarily. Some vendors use the name for the full 43-residue protein, while others apply it to a short actin-binding fragment or to a related tetrapeptide. The sequence should be confirmed from documentation rather than assumed from the label.
No thymosin beta-4 fragment holds marketing approval as a medicine in major jurisdictions. Material offered for sale is typically labelled for laboratory research only.
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.