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Updated 2025-08-08. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| 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 |
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.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
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.
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.
== External links == Open source software for calculating SPINA-GBeta and other parameters for endotyping glucose homeostasis. (Permanent DOI), (General information and US mirror) Functions for R and S for calculating SPINA-GBeta, SPINA-GR and SPINA-DI. (Permanent DOI) Package "SPINA" for the statistical environment R
=== Carl Hardee Sr. campaign === In March 2017, Hardee's began to move away from the sexualized ads by releasing a commercial featuring a white bearded character played by Charles Esten as "Carl Hardee Sr." who had come back into the office (much to the delight of the employees) to find his son (Drew Tarver), a.k.a. "Carl Jr." who was focusing on sex appeal over its food. The commercial marked a turning point in CKE's advertising, as the company wanted to move away from its provocative ads and focus more on food and as a competitor to Five Guys, Steak 'n Shake, and In-N-Out Burger. "Carl Hardee Sr." was also expected to become the new company spokesperson.
== Binding and activation == Ligand binding is an equilibrium process. Ligands bind to receptors and dissociate from them according to the law of mass action in the following equation, for a ligand L and receptor, R. The brackets around chemical species denote their concentrations.
An unexpected series of experimental results for the rate of decay of heavy highly charged radioactive ions circulating in a storage ring provoked theoretical activity in an effort to find a convincing explanation. The rates of weak decay of two radioactive species with half-lives of about 40 s and 200 s were reported to have a significant oscillatory modulation, with a period of about 7 s. The reported phenomenon is known as the GSI anomaly, as the storage ring is a facility at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. As the decay process produces an electron neutrino, some of the proposed explanations for the observed rate oscillation invoked neutrino properties. Initial ideas related to flavour oscillation met with skepticism. A 2016 proposal involved mass differences between neutrino mass eigenstates. In a follow-up study published in 2019, measurements of about 9,000 electron-capture decays of hydrogen-like promethium-142 ions showed no periodic modulation. The results were consistent with exponential decay.
Sources: en.wikipedia.org
=== Glycogen synthesis === The phosphorylation of glucose to glucose 6-phosphate has role in regulating glycogen synthase. Glucose is phosphorylated to glucose 6-phosphate to allow its transport across the membrane by ATP-D-glucose 6-phosphotransferase and non-specific hexokinase (ATP-D-hexose 6-phosphotransferase). Liver cells are freely permeable to glucose, and the initial rate of phosphorylation of glucose is the rate-limiting step in glucose metabolism by the liver. The liver's crucial role in controlling blood sugar concentrations by breaking down glucose into carbon dioxide and glycogen is characterized by the negative Gibbs free energy (ΔG) value, which indicates that this is a point of regulation with. The hexokinase enzyme has a low Michaelis constant (Km), indicating a high affinity for glucose, so this initial phosphorylation can proceed even when glucose levels at nanoscopic scale within the blood. The phosphorylation of glucose can be enhanced by the binding of fructose 6-phosphate (F6P), and lessened by the binding fructose 1-phosphate (F1P). Fructose consumed in the diet is converted to F1P in the liver. This negates the action of F6P on glucokinase, which ultimately favors the forward reaction. The capacity of liver cells to phosphorylate fructose exceeds capacity to metabolize fructose-1-phosphate. Consuming excess fructose ultimately results in an imbalance in liver metabolism, which indirectly exhausts the liver cell's supply of ATP.
== Size exclusion chromatography == A study was done looking at the application of size exclusion chromatography in the purification of cross-link peptides within samples. When the eluted peptides were analyzed, cross-linked peptides could be detected at higher concentrations in the earlier fractions, eluting before modified or unmodified peptides.
In addition to relaxin production by the horse embryo, the maternal placenta is the main source of relaxin production, whereas in most animals the main source of relaxin is the corpus luteum. Placental trophoblast cells produce relaxin, however, the size of the placenta does not determine the level of relaxin production. This is seen because different breeds of horses show different relaxin levels. From 80 day of gestation onwards, relaxin levels will increase in the mare's serum with levels peaking in late gestation. Moreover, the pattern of relaxin expression will follow the expression of oestrogen, however, there is not yet a known link between these two hormones. During labour, there is a spike in relaxin 3–4 hours before delivery, which is involved in myometrial relaxation and softening of the pelvic ligaments to aid preparation of the birth canal for the delivery of the horse foetus. Following birth, the levels of relaxin will gradually decrease if the placenta is also delivered, however, if the placenta is retained in the mare then the levels will remain high. In addition, if the mare undergoes an abortion then the relaxin levels will decline as the placenta ceases to function.
==== Film, stage, and television influenced by Jung's ideas ==== Federico Fellini brought to the screen exuberant imagery shaped by his encounter with Jung's ideas, especially Jungian dream interpretation. Fellini preferred Jung to Freud because Jungian analysis defined the dream not as a symptom of a disease that required a cure but rather as a link to archetypal images shared by all of humanity. Stanley Kubrick's 1987 film Full Metal Jacket has an underlying theme about the duality of man. In one scene, a colonel asks a soldier, "You write 'Born to Kill' on your helmet and you wear a peace button. What's that supposed to be, some kind of sick joke?" The soldier replies, "I think I was trying to suggest something about the duality of man, sir...the Jungian thing, sir." (The colonel in this scene is played by the brother of famed Jungian psychologist Marion Woodman.) In the 1994 Frasier episode, "Frasier Crane's Day Off", Niles fills in for his brother, declaring: "Although I feel perfectly qualified to fill Frasier's radio shoes, I should warn you that while Frasier is a Freudian, I am a Jungian. So there'll be no blaming Mother today." Robert Eggers's 2019 psychological thriller The Lighthouse has elements strongly influenced by Jung's work, with Eggers hoping that "it's a movie where both Jung and Freud would be furiously eating their popcorn".
=== Radio-frequency identification and smart labels === Radio-frequency identification tags use radio waves to identify and track products, packages, pallets, and unit loads. Passive tags receive power from a reader, while active tags contain their own power source. RFID tags may be combined with temperature, humidity, shock, or other sensors. They can support inventory control, authentication, cold-chain monitoring, and supply-chain traceability. Near-field communication tags allow compatible smartphones and other devices to retrieve product information or interact with digital services.
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.
Divide it into single-use aliquots and hold them frozen at -20 °C or below, protected from light. Repeated thawing of one container is the main avoidable source of variability.