If you have been reading about TB-500 and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-05-16. Where a claim depends on a specific study, the study is described rather than over-claimed.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
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 formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
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.
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.
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.
Another fifteen years were required before new and more sophisticated technologies, united today under the name of genetic engineering, would permit the isolation and characterization of genes, in particular those of highly complex organisms.
=== Lysosomal damage inhibits mTOR and induces autophagy === Active mTORC1 is positioned on lysosomes. mTOR is inhibited when lysosomal membrane is damaged by various exogenous or endogenous agents, such as invading bacteria, membrane-permeant chemicals yielding osmotically active products (this type of injury can be modeled using membrane-permeant dipeptide precursors that polymerize in lysosomes), amyloid protein aggregates (see above section on Alzheimer's disease) and cytoplasmic organic or inorganic inclusions including urate crystals and crystalline silica. The process of mTOR inactivation following lysosomal/endomembrane damage is mediated by the protein complex termed GALTOR. At the heart of GALTOR is galectin-8, a member of β-galactoside binding superfamily of cytosolic lectins termed galectins, which recognizes lysosomal membrane damage by binding to the exposed glycans on the lumenal side of the delimiting endomembrane. Following membrane damage, galectin-8, which normally associates with mTOR under homeostatic conditions, no longer interacts with mTOR but now instead binds to SLC38A9, RRAGA/RRAGB, and LAMTOR1, inhibiting Ragulator's (LAMTOR1-5 complex) guanine nucleotide exchange function. mTOR is a negative regulator of autophagy in general, best studied during response to starvation, which is a metabolic response. During lysosomal damage however, mTOR inhibition activates autophagy response in its quality control function, leading to the process termed lysophagy that removes damaged lysosomes.
=== Post-classical development === During the Middle Ages, the word "anarchia" came into use in Latin, in order to describe the eternal existence of the Christian God. It later came to reconstitute its original political definition, describing a society without government. Christian theologists came to claim that all humans were inherently sinful and ought to submit to the omnipotence of higher power, with the French Protestant reformer John Calvin declaring that even the worst form of tyranny was preferable to anarchy. The Scottish Quaker Robert Barclay also denounced the "anarchy" of libertines such as the Ranters. In contrast, radical Protestants such as the Diggers advocated for anarchist societies based on common ownership. Although following attempts to establish such a society, the Digger Gerard Winstanley came to advocate for an authoritarian form of communism. During the 16th century, the term "anarchy" first came into use in the English language. It was used to describe the disorder that results from the absence of or opposition to authority, with John Milton writing of "the waste/Wide anarchy of Chaos" in Paradise Lost. Initially used as a pejorative descriptor for democracy, the two terms began to diverge following the Atlantic Revolutions, when democracy took on a positive connotation and was redefined as a form of elected, representational government.
Wind direction plays a critical role in shaping the inland extent of X. parietina. Southwesterly winds in the warmer months carry marine aerosols further inland, while easterly storms contribute additional sea salt deposition through precipitation. The influence of these aerosols is evident in Maine cemeteries: X. parietina is more frequent in open cemeteries exposed to prevailing winds, compared to wooded cemeteries, which block or capture airborne sea salts, and have significantly lower frequencies of the lichen. In recent decades, inland populations of X. parietina have been discovered in southern Ontario, suggesting an expansion beyond its traditionally coastal range. Once considered extirpated from the region, the species was rediscovered growing on trees in several inland locations. This inland occurrence raises questions about whether the lichen has reestablished after a long absence or has persisted undetected for decades. The expansion may be linked to increasing nitrogen deposition from agricultural runoff and air pollution, which create conditions favorable for nitrophilous lichens like X. parietina. Another possible factor in its inland spread is the widespread use of road salt in Ontario over the past 50–70 years. Since X. parietina thrives in salt-rich coastal environments, roadside salt deposition may have provided an artificial habitat, mimicking the chemical conditions of maritime regions.
== Alternatives == RGD is the most widely used of a larger class of cell adhesive peptides. These short amino acid sequences are the minimum motif of a larger protein that is necessary for binding to a cell surface receptor that drives cell adhesion. The majority (89%) of published studies on biomaterials functionalized with cell adhesive peptides use RGD, whereas IKVAV and YIGSR are used in 6%, and 4% of those studies, respectively. Cell adhesive peptides isolated from fibronectin include RGD, RGDS, PHSRN, and REDV. YIGSR and IKVAV are isolated from laminin, whereas DGEA and GFOGER/GFPGER are isolated from collagen. Artificial amino acid sequences, which bear no biological similarity to ECM proteins, have also been synthesized, and include the α5β1-specific peptide RRETAWA.
Sources: en.wikipedia.org
=== Climate === Located in northwestern Italy at the foot of the Alps, Turin features a mid-latitude, four seasons humid subtropical climate (Köppen: Cfa), similar to that of Grenoble, located not far away in the French Alps. Winters are moderately cold and dry; summers are mild in the hills and quite hot in the plains. Rain falls mostly during spring and autumn; during the hottest months, otherwise, rains are less frequent but heavier (thunderstorms are frequent). During the winter and autumn months banks of fog, which are sometimes very thick, form in the plains but rarely on the city because of its location at the end of the Susa Valley. Snowfalls are not uncommon during the winter months, though substantial accumulation is quite uncommon. Its position on the east side of the Alps makes the weather drier than on the west side because of the föhn wind effect. The highest temperature ever recorded was 37.1 °C (98.8 °F) on 11 August 2003, and the lowest was −21.8 °C (−7.2 °F) on 12 February 1956.
=== Nonsense === Nonsense mutations are changes in DNA sequence that introduce a premature stop codon, causing any resulting protein to be abnormally shortened. This often causes a loss of function in the protein, as critical parts of the amino acid chain are no longer assembled. Because of this terminology, stop codons have also been referred to as nonsense codons.
There are 25 known isotopes of potassium, three of which occur naturally: 39K (93.3%), 40K (0.0117%), and 41K (6.7%) (by mole fraction). Naturally occurring 40K has a half-life of 1.250×109 years. It decays to stable 40Ar by electron capture or positron emission (11.2%) or to stable 40Ca by beta decay (88.8%). This decay results in a relatively higher concentration of Argon in the atmosphere. The decay of 40K to 40Ar is the basis of a common method for dating rocks. The conventional potassium–argon dating method depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon (40Ar) was quantitatively retained. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 40Ar that has accumulated. The minerals best suited for dating include biotite, muscovite, metamorphic hornblende, and volcanic feldspar; whole rock samples from volcanic flows and shallow instrusives can also be dated if they are unaltered. Apart from dating, potassium isotopes have been used as tracers in studies of weathering and for nutrient cycling studies because potassium is a macronutrient required for life on Earth. 40K occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. 40K is the radioisotope with the largest abundance in the human body. In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C.
== Applications == LPC was first suggested as a human food in the early 20th century, but it has not achieved much success, despite early promise. Norman Pirie, the Copley Medal winner from the UK, studied LPC and promoted its use for human consumption. He and his team developed machines for extraction of LPC, including low-maintenance "village units" intended for poor rural communities. These were installed in places such as villages in south India. The non profit organization, Leaf for Life, maintains a list of human edible leaves and provides recommendations for the top choices of plants. There has recently been an interest in using LPCs as an alternative food (or resilient food) during times of catastrophe or food shortages. Such resilient food LPCs would be derived from widely geographically dispersed tree leaves from forests or agricultural waste. LPC have been evaluated for infant weaning foods. The increasing reliance on feedlot based animal rearing to satisfy human appetites for meat has increased demand for cheaper vegetable protein sources. This has recently led to renewed interest in LPC to reduce the use of human-edible vegetable protein sources in animal feed. Leaf protein has had successful trials as a substitute for soy feed for chickens and pigs. LPC from alfalfa can be included in feed for tilapia as a partial replacement for fish meal.
=== 2028 === Kennedy has been floated as a possible presidential candidate for the Republican Party in 2028. When asked about a possible 2028 presidential run during a Politics and Eggs event for New Hampshire Institute of Politics at Saint Anselm College, Kennedy said: "I'm happy as a United States senator, plan to run for reelection. You never say never."
Sources: en.wikipedia.org
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
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.