This is a working overview of research chemical, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-25. Anything still debated is marked as such rather than presented as settled.
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
Thymosin beta-4 itself is a small, widely expressed protein that sequesters monomeric actin and participates in cell migration, angiogenesis, and tissue repair. Researchers have examined the shortened fragment as a possible mimic of some of these activities, reasoning that the actin-binding motif lies within the first few residues. Binding to monomeric actin has been observed in cell-free systems. Whether the fragment reproduces the broader effects of the full protein in living tissue remains an open question, and findings from animal models are frequently cited without a clear bridge to human physiology.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | N-terminal fragment of thymosin beta-4 |
| Residue count | Seven | Sequence LKKTETQ |
| Approximate mass | 889 Da | Acetylated seven-residue peptide |
| Common synonyms | TB4 fragment, TB500 | Not identical to full-length TB4 |
| Reported activity | Actin binding | Observed mainly in cell-free systems |
The seven-residue chain carries several polar and charged side chains, so it dissolves readily in water and in aqueous buffers near neutral pH. No cysteine is present, so disulphide formation is not a concern and reducing agents are unnecessary. Dilute ammonium hydroxide or acetonitrile-water mixtures are sometimes used for stock solutions when initial dissolution is slow. Strongly alkaline conditions and prolonged contact with oxidising agents are avoided because they can modify lysine-containing stretches, and haze in solution usually signals incomplete dissolution or aggregated material.
Identity and purity are checked with reversed-phase high-performance liquid chromatography, which separates the target sequence from truncated or deletion analogues, and with mass spectrometry, which confirms the expected molecular mass. Amino acid analysis and peptide mapping give orthogonal confirmation but are used less often outside specialist laboratories. Counter-ion content varies: material purified on trifluoroacetic acid gradients retains trifluoroacetate, and ion exchange can convert the salt form. Residual water and solvent are measured by Karl Fischer titration or thermogravimetric analysis, and any purity figure should be read together with the method used to obtain it.
Lyophilised peptide powders are hygroscopic, and the fragment absorbs atmospheric moisture when a vial is opened at room temperature. Weighing and aliquoting are normally done quickly in a dry environment, and stock solutions are divided into single-use portions before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and can shift the measured content of a vial. These practices are general to synthetic peptides rather than unique to this sequence, but they matter more for short chains kept for long periods.
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.
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.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
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.
Usually, an enzyme molecule has only one active site, and the active site fits with one specific type of substrate. An active site contains a binding site that binds the substrate and orients it for catalysis. The orientation of the substrate and the close proximity between it and the active site is so important that in some cases the enzyme can still function properly even though all other parts are mutated and lose function. Initially, the interaction between the active site and the substrate is non-covalent and transient. There are four important types of interaction that hold the substrate in a defined orientation and form an enzyme-substrate complex (ES complex): hydrogen bonds, van der Waals interactions, hydrophobic interactions and electrostatic force interactions. The charge distribution on the substrate and active site must be complementary, which means all positive and negative charges must be cancelled out. Otherwise, there will be a repulsive force pushing them apart. The active site usually contains non-polar amino acids, although sometimes polar amino acids may also occur. The binding of substrate to the binding site requires at least three contact points in order to achieve stereo-, regio-, and enantioselectivity. For example, alcohol dehydrogenase which catalyses the transfer of a hydride ion from ethanol to NAD+ interacts with the substrate methyl group, hydroxyl group and the pro-(R) hydrogen that will be abstracted during the reaction.
== Mechanism of action == In-vitro binding inhibition data showed that Epelsiban is a highly potent and selective non-peptide oxytocin antagonist with sub-namomolar potency at the human oxytocin receptor (hOTR) Ki = 0.13 nM and with>50000-fold, >63000-fold, and >31000-fold selectivity over the human V1a, V1b and V2 vasopressin receptors. It is also 100-fold more potent at the hOTR than atosiban (a marketed intravenous peptide oxytocin antagonist) and is 5-fold more potent against the hOTR, and more selective against the human vasopressin receptors, especially V2, than retosiban. High in vivo oxytocin antagonist potency was demonstrated in the anesthetized rat model, where uterine contractions were elicited by intravenous administration of oxytocin and reduction in uterine contractility was measured after subsequent intravenous administrations of increasing doses of Epelsiban, which gave an IC50 of 192nM.
In these brooding species, the eggs are relatively large, supplied with yolk, and generally develop directly into miniature starfish without an intervening larval stage, called "lecithotrophic". In Parvulastra parvivipara, an intragonadal brooder, the young starfish obtain nutrients by eating other eggs and embryos in the brood pouch. Brooding occurs in species that live in colder waters, as well as in smaller species that produce just a few eggs. The timing of spawning may be influenced by lighting conditions, water temperature, food availability, and other factors. Individuals may gather together to release their gametes at once, using pheromones to attract each other. In some species, a male and female may come together and form a pair. They engage in pseudocopulation which involves the male crawling on the female; the male fertilises the gametes while the female releases them.
=== Vickers Instruments === In 1989, Bio-Rad purchased the British instrument-making firm, Vickers (1828 - 1999), apart from their defense products, which were sold to British Aerospace. This company had been known until 1963 as Cooke, Troughton & Simms. Cooke, Troughton & Simms was formed in 1922 by the merging of T. Cooke & Sons, a York-based instrument maker founded in 1837 by the self-taught schoolmaster Thomas Cooke, and the London instrument-maker, Troughton & Simms founded in 1828 by Edward Troughton who began his apprenticeship in 1773.
Oligonucleotides are short DNA or RNA molecules, oligomers, that have a wide range of applications in genetic testing, research, and forensics. Commonly made in the laboratory by solid-phase chemical synthesis, these small fragments of nucleic acids can be manufactured as single-stranded molecules with any user-specified sequence, and so are vital for artificial gene synthesis, polymerase chain reaction (PCR), DNA sequencing, molecular cloning and as molecular probes. In nature, oligonucleotides are usually found as small RNA molecules that function in the regulation of gene expression (e.g. microRNA), or are degradation intermediates derived from the breakdown of larger nucleic acid molecules. Oligonucleotides are characterized by the sequence of nucleotide residues that make up the entire molecule. The length of the oligonucleotide is usually denoted by "-mer" (from Greek meros, "part"). For example, an oligonucleotide of six nucleotides (nt) is a hexamer, while one of 25 nt would usually be called a "25-mer". Oligonucleotides readily bind, in a sequence-specific manner, to their respective complementary oligonucleotides, DNA, or RNA to form duplexes or, less often, hybrids of a higher order. This basic property serves as a foundation for the use of oligonucleotides as probes for detecting specific sequences of DNA or RNA. Examples of procedures that use oligonucleotides include DNA microarrays, Southern blots, ASO analysis, fluorescent in situ hybridization (FISH), PCR, and the synthesis of artificial genes.
Sources: en.wikipedia.org
=== Foods === Sucrose esters are used as food additives in a variety of food. European Parliament and Council Directive No 95/2/EC limited the use of sucrose esters under E 473 in each kind of food. No longer in force, Date of end of validity: 20/01/2010; Repealed by 32008R1333 .
) without multiplying by 1000 unless the basic SI unit of mol/s were to be used, which would otherwise require the molar mass to be converted to kg/mol. For convenience in avoiding conversions in the imperial (or US customary units), some engineers adopted the pound-mole (notation lb-mol or lbmol), which is defined as the number of entities in 12 lb of 12C. One lb-mol is equal to 453.59237 g‑mol, which is the same numerical value as the number of grams in an international avoirdupois pound. Greenhouse and growth chamber lighting for plants is sometimes expressed in micromoles per square metre per second, where 1 mol photons ≈ 6.02×1023 photons. The obsolete unit einstein is variously defined as the energy in one mole of photons and also as simply one mole of photons.
While exiting totally from Sabah and Sarawak. There had about 16 stores in both of the states which they transferred the business to local stores as new owners rather than closing them permanently. In 2020, Many branches would be replaced by TF Value-Mart or NSK Trade City. Similar downsize also observed in Singapore with the closure of two stores located at Bukit Panjang and Jalan Tenteram in Whampoa estate, and its VivoCity hypermarket in 2019. It also closed its Parkway Parade hypermarket on 29 February 2020. In May 2021, Giant announced its withdrawal from Indonesia since 31 July 2021. Some branches would be replaced with Hero Supermarket and IKEA small stores. Hero is previously owned by the DFI Retail Group, as it was spun off in 2024.
==== Disadvantages ==== There is an increasing risk of the practice of coprophagy when providing low-protein diets to dogs; a negative correlation exists between the amount of protein fed and the occurrence of coprophagy. Maintenance needs should still be met by low-protein diets, and the muscle turnover (i.e. synthesis and breakdown) will also remain at an optimal rate, as long as the amino acid intake remains balanced and there are no limiting amino acids. There is a greater opportunity for amino acids to balance in diets containing more protein.
Sources: en.wikipedia.org
No. Thymosin beta-4 is a 43-residue protein, while TB-500 refers to a seven-residue fragment corresponding to its N-terminal region. The two names are often used loosely in commercial and community writing, which obscures the difference in size, sequence, and likely behavior.
The fragment contains an actin-binding motif, and cell-free experiments show that it can interact with monomeric actin. That observation is the basis for interest in cell migration and repair processes. Effects reported in animals are not established for humans.
Purity is usually stated by the supplier rather than fixed by a pharmacopoeial monograph, and typical listings report a percentage from reverse-phase HPLC. Independent verification is uncommon. Because no single accepted specification exists, comparisons between lots and between suppliers are difficult.
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.