Thymosin beta-4 raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-01-16 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
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.
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.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
From 1928 to 1932, Albert Szent-Györgyi and Joseph L. Svirbely's Hungarian team, and Charles Glen King's American team, identified the anti-scorbutic factor. Szent-Györgyi isolated hexuronic acid from animal adrenal glands, and suspected it to be the antiscorbutic factor. In late 1931, Szent-Györgyi gave Svirbely the last of his adrenal-derived hexuronic acid with the suggestion that it might be the anti-scorbutic factor. By the spring of 1932, King's laboratory had proven this, but published the result without giving Szent-Györgyi credit for it. This led to a bitter dispute over priority. In 1933, Walter Norman Haworth chemically identified the vitamin as l-hexuronic acid, proving this by synthesis in 1933. Haworth and Szent-Györgyi proposed that L-hexuronic acid be named a-scorbic acid, and chemically l-ascorbic acid, in honor of its activity against scurvy. The term's etymology is from Latin, "a-" meaning away, or off from, while -scorbic is from Medieval Latin scorbuticus (pertaining to scurvy), cognate with Old Norse skyrbjugr, French scorbut, Dutch scheurbuik and Low German scharbock. Partly for this discovery, Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine, and Haworth shared that year's Nobel Prize in Chemistry. In 1957, J. J. Burns showed that some mammals are susceptible to scurvy as their liver does not produce the enzyme l-gulonolactone oxidase, the last of the chain of four enzymes that synthesize vitamin C. American biochemist Irwin Stone was the first to exploit vitamin C for its food preservative properties.
In most of Central and Eastern Europe, poppy seed is commonly used for traditional pastries and cakes, and it is legal to grow poppies throughout the region, although Germany requires a license. Since January 1999 in the Czech Republic, according to the 167/1998 Sb. Addictive Substances Act, poppies growing in fields larger than 100 square metres (120 sq yd) is obliged for reporting to the local Custom Office. Extraction of opium from the plants is prohibited by law (§ 15 letter d/ of the act). It is also prohibited to grow varieties with more than 0.8% of morphine in dry matter of their capsules, excluding research and experimental purposes (§24/1b/ of the act). The name Czech blue poppy refers to blue poppy seeds used for food. The United Kingdom does not require a license for opium poppy cultivation, but does for extracting opium for medicinal products. When the European Union attempted to ban the cultivation of Papaver somniferum by private individuals on a small scale (such as personal gardens), citizens in EU countries where poppy seed is eaten heavily, such as countries in the Central-Eastern region, strongly resisted the plan, causing the EU to change course.
Alfentanil, sold under the brand name Alfenta among others, is a potent, short-acting synthetic opioid analgesic drug used for anesthesia in surgery. It is an analogue of fentanyl with around one-fourth to one-tenth the potency, one-third the duration of action, and an onset of action four times faster than that of fentanyl. Alfentanil has a pKa of approximately 6.5, which leads to a very high proportion of the drug being uncharged at physiologic pH, a characteristic responsible for its rapid-onset. It is an agonist of the μ-opioid receptor. While alfentanil tends to cause fewer cardiovascular complications than other similar drugs such as fentanyl and remifentanil, it tends to give stronger respiratory depression and so requires careful monitoring of breathing and vital signs. Almost exclusively used by anesthesia providers during portions of a case where quick, fast-acting (though not long-lasting) pain control is needed (as, for example, during nerve blocks), alfentanil is administered by the parenteral (injected) route for fast-onset and precise control of dosage. Discovered at Janssen Pharmaceutica in 1976, alfentanil is classified as a Schedule II drug in the United States.
Improving metabolism (improving insulin sensitivity, inhibiting de novo lipogenesis, or increasing fatty acid oxidation). Metabolic modulators tested in MASH include glucagon-like peptide-1 receptor agonists (GLP-1 agonists), GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) or glucagon co-agonists and thyromimetics. Some of these drugs may treat MASFLD by significantly reducing body weight. Reducing inflammation, for example reducing oxidative stress and hepatocyte death. These drugs, such as chemokine antagonists, anti-apoptotics, vascular adhesion protein-1 inhibitors, and c-Jun N-terminal kinase inhibitors, have not shown benefit. "Gut-liver axis targets" that either change a person's microbiome, or act on bile acids Anti-fibrotic drugs, such as fibroblast growth factor analogues, which have largely not met their endpoints Other treatments such as farnesoid X receptor (FXR) agonists, peroxisome proliferator-activated receptor (PPAR) agonists, and ASK1 (apoptosis signal-regulating kinase 1) inhibitors may improve MASFLD by multiple mechanisms simultaneously.
Sources: en.wikipedia.org
==== Prostacyclin ==== Prostacyclin (PGI2) is released by endothelium and activates platelet Gs protein-linked receptors. This, in turn, activates adenylyl cyclase, which synthesizes cAMP. cAMP inhibits platelet activation by decreasing cytosolic levels of calcium and, by doing so, inhibits the release of granules that would lead to activation of additional platelets and the coagulation cascade.
Xanthoria parietina serves as both a food source and shelter for certain gastropods. The snail Balea perversa uses the lichen for shelter and nourishment. Similarly, other gastropods, such as Helicigona lapicida, feed on Xanthoria parietina. This grazing may contribute to lichen dispersal: photobiont cells from X. parietina partially survive passage through the snail's digestive tract, retaining some photosynthetic activity even after digestion. Such survival raises the possibility that snail herbivory could facilitate lichen relichenization—either by recombining surviving symbionts from the same thallus or by mixing photobionts and mycobionts from different individuals in fecal deposits. However, digestion significantly reduces photobiont viability, with photobiont fluorescence (a measure of photosynthetic activity) declining by 41–44% after passage through the snail gut. While some cells remain intact, they often suffer morphological damage (including shrunken chloroplasts and enlarged cell wall-to-membrane distances), leaving it unclear whether surviving photobionts can effectively establish new lichens without viable fungal spores or hyphae.
== External links == International Rett Syndrome Foundation Rett UK Support and Research Charity Reverse Rett UK Rett Registry UK Rett Syndrome Research Trust Ensembl Gene ref Protein ref GeneCard RettBASE: IRSA MECP2 Variation Database Archived 2005-12-17 at the Wayback Machine GeneReview/NIH/UW entry on MECP2-Related Disorders GeneReviews/NCBI/NIH/UW entry on MECP2 Duplication Syndrome UK Site for Families Affected by MECP2. Site for Families Affected by MECP2. Site officiel français sur la duplication MeCP2
Sources: en.wikipedia.org
The US Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for B vitamins in 1998. At that time, there was not sufficient information to establish EARs and RDAs for pantothenic acid. In instances such as this, the Board sets Adequate Intakes (AIs), with the understanding that at some later date, AIs may be replaced by more exact information. The current AI for teens and adults ages 14 and up is 5 mg/day. This was based in part on the observation that for a typical diet, urinary excretion was approximately 2.6 mg/day, and that bioavailability of food-bound pantothenic acid was roughly 50%. AI for pregnancy is 6 mg/day. AI for lactation is 7 mg/day. For infants up to 12 months, the AI is 1.8 mg/day. For children ages 1–13 years, the AI increases with age from 2 to 4 mg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
== External links == A collection of photosynthesis pages for all levels from a renowned expert (Govindjee) In depth, advanced treatment of photosynthesis, also from Govindjee Science Aid: Photosynthesis Article appropriate for high school science Metabolism, Cellular Respiration and Photosynthesis – The Virtual Library of Biochemistry and Cell Biology Overall examination of Photosynthesis at an intermediate level Overall Energetics of Photosynthesis The source of oxygen produced by photosynthesis Interactive animation, a textbook tutorial
Essendon's first recorded jumpers were navy blue (The Footballers, edited by Thomas Power, 1875) although the club wore 'red and black caps and hose'. In 1877, The Footballers records the addition of 'a red sash over left shoulder'. This is the first time a red sash as part of the club jumper, and by 1878 there are newspaper reports referring to Essendon players as 'the men in the sash'. Given that blue and navy blue were the most popular colours at the time, it is thought that Essendon adopted a red sash in 1877 to distinguish its players from others in similar-coloured jumpers.
== Medical uses == Ropinirole is prescribed for mainly Parkinson's disease, restless legs syndrome, and extrapyramidal symptoms. It can also reduce the side effects caused by selective serotonin reuptake inhibitors, including Parkinsonism syndrome as well as sexual dysfunction and erectile dysfunction caused by either SSRIs or antipsychotics. A 2008 meta-analysis found that ropinirole was less effective than pramipexole in the treatment of restless legs syndrome.
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.
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.