This is a working overview of actin binding, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-28 and is reviewed periodically as new material appears.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
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.
| Property | Value | Notes |
|---|---|---|
| Physical form | Lyophilised powder | Sealed vial; reconstituted before laboratory use |
| Appearance | White to off-white solid | Visual descriptor used on certificates of analysis |
| Solubility class | Water-soluble | Dissolves in water and aqueous buffers |
| Reported mass, fragment | Near 889 Da | Value depends on the stated sequence |
| Reported mass, parent protein | Near 4963 Da | 43-residue thymosin beta-4 |
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.
Proposed activity centers on actin sequestration and on the movement of cells during repair processes. In cell culture and animal models, the fragment has been associated with migration, tube formation, and tissue remodeling. These observations are frequently described as preliminary, because most published work uses rodent or in vitro systems rather than controlled human trials. Whether the short fragment reproduces the effects of the full protein remains an open question, and the relationship between dose, route, and measured outcome is not well characterized.
The compound circulates in the literature as a research reagent rather than an approved therapeutic. Regulatory agencies in several countries have not authorized it for medical use, and sporting bodies list related thymosin beta-4 peptides among prohibited substances. Suppliers typically market it with a purity figure and a certificate of analysis, while peer-reviewed clinical reports remain sparse. Discussions therefore often separate laboratory findings from anecdotal reports, and reviewers tend to note the small size and methodological limits of the available studies.
TB-500 refers to a synthetic peptide fragment derived from the actin-binding region of thymosin beta-4, a protein present in most mammalian cells. The full protein contains forty-three amino acids, while the commonly sold fragment is a much shorter acetylated sequence, often cited as LKKTETQ. The fragment retains part of the actin-binding motif but lacks the remainder of the parent protein. Material sold under this name is usually lyophilized powder intended for laboratory research, and it is not a finished pharmaceutical product.
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.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
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.
== Other activities == LL-37 plays a role in the activation of cell proliferation and migration, contributing to the wound closure process. All these mechanisms together play an essential role in tissue homeostasis and regenerative processes. Moreover, it has an agonistic effect on various pleiotropic receptors, for example, formyl peptide receptor like-1 (FPRL-1), purinergic receptor P2X7, epidermal growth factor receptor (EGFR). Furthermore, it induces angiogenesis and regulates apoptosis.
The Rejuvant study (a human clinical trial) reported that the median and range of the biological age of females before treatment was 62.15 (range, 46.4 to 73) years and fell to 55.55 (range 33.4 to 63.7) years after an average of 7 months treatment. These values for men were 61.85 (range 41.9 to 79.7) years before and 53.3 (33 to 74.9) years after treatment. Overall, the combined group of males and females showed an average fall in biological age of 8 years compared to before treatment. The p-value for this difference was extraordinarily significant, i.e., 6.538x10-12, in showing that this treatment decreased the participants' biological ages. However, the study did not: a) include a control group (i.e., concurrent study of individuals taking a placebo instead of Rejuvant®); b) determine if the retinyl palmitate, vitamin A, and/or calcium given with α-ketoglutarate contributed to the changes in biological ages; and c) disclose which genes were tracked for the methylation of their CpG island. The study recommended that studies need to include control groups taking a placebo or the appropriate dosages of retinyl palmitate, vitamin A, and calcium. Also, TruMe Labs, who were the maker and marketer of the biological age assay used in this study, sponsored part of the study and contributed three of its employees as authors to the study.
=== Consumer Products === The General Product Safety Regulation (GPSR) is a European regulation on consumer protection. It replaces Directive 2001/95/EC on general product safety. The regulation is intended to ensure that products placed on the market in the European internal market do not endanger the health and safety of consumers through a high level of consumer protection. The GPSR mandates a risk-based approach to product safety, requiring manufacturers and other economic operators to conduct comprehensive risk assessments before placing products on the market. These assessments must consider:
===== Venezuela ===== In May 2023, ahead of a South American summit to which all the presidents of the region were invited, Lula met with Venezuelan president Nicolás Maduro and stated that "you know the narrative that was built against Venezuela, of anti-democracy, of authoritarianism" and "it is in your hands, comrade, to build your narrative and turn this party around so that we can definitively win and Venezuela becomes a sovereign country again where only its people, through a free vote, say who will govern". Chilean president Gabriel Boric and Uruguayan president Luis Lacalle Pou, who were some of the summit attendees, disapproved of Lula's comments.
=== Research === AM-1006 – undefined mechanism of action (short-acting subperceptual psychoactive drug) – substance use disorders EQL-101 – undefined mechanism of action (non-hallucinogenic non-cardiotoxic ibogaine derivative) – substance use disorders – Equulus Therapeutics Ibogaine – various actions, oneirogen/hallucinogen – substance-related disorders Mebufotenin (5-MeO-DMT; LSR-2000) – non-selective serotonin receptor agonist, serotonin 5-HT1A and 5-HT2A receptor agonist, serotonergic psychedelic – alcoholism MYCO-004 (patch-delivered tryptamine compound) – undefined mechanism of action, serotonergic psychedelic – smoking withdrawal, substance-related disorders Research programme: Ibogaine derivatives - MindMed/Nextage Therapeutics – various actions – opioid-related disorders Research programme: monoclonal antibody therapeutics - CounterX Therapeutics – undefined mechanism of action – opioid-related disorders Research programme: psychedelic and empathogenic compounds subcutaneous - Bexson Biomedical – undefined mechanism of action – substance-related disorders Substance-related disorders therapeutics - Tessara Therapeutics/Xylo Bio/University of Sydney – neuronal plasticity modulators – substance-related disorders VVZ-2471 – metabotropic glutamate mGlu5 receptor antagonist, serotonin 5-HT2A receptor antagonist – opioid-related disorders
Sources: en.wikipedia.org
=== Cookbooks === Buwei Yang Chao. How to Cook and Eat in Chinese. (New York: John Day, 1945; revisions and reprints). Fuchsia Dunlop. Land of Plenty: A Treasury of Authentic Sichuan Cooking. (New York: Norton, 2003). ISBN 0393051773. Fuchsia Dunlop. Revolutionary Chinese Cookbook: Recipes from Hunan Province. (New York: Norton, 2007). ISBN 0393062228. Fuchsia Dunlop. Shark's Fin and Sichuan Pepper: A Sweet-Sour Memoir of Eating in China. (New York: Norton, 2008). ISBN 9780393066579. Chinese cook book by Vernon Galster Emily Hahn, Recipes, The Cooking of China. (Alexandria, Va.: Time-Life Books, Foods of the World, 1981). Hsiang-Ju Lin and Tsuifeng Lin. Chinese Gastronomy. (London: Nelson, 1969; rpr.). ISBN 0171470575. Yan-Kit So. Classic Food of China. (London: Macmillan, rpr 1994, 1992). ISBN 9780333576717. Martin Yan. Martin Yan's Chinatown Cooking: 200 Traditional Recipes from 11 Chinatowns around the World. (New York: Morrow, 2002). ISBN 0060084758. Georgina Freedman. Cooking South of The Clouds: Recipes and Stories From China's Yunnan Province. (Octopus; Kyle, 2018). ISBN 9780857834980.
=== Continuing Claim === His only son, Ernest Augustus, Crown Prince of Hanover, inherited the claim upon George's death in 1878. Ernest Augustus was also first in line to the throne of the Duchy of Brunswick, whose rulers had been a junior branch of the House of Hanover. In 1884, that branch became extinct with the death of William, a distant cousin of Ernest Augustus. Since Ernest Augustus refused to renounce his claim to annexed Hanover, the Bundesrat of the German Empire ruled that he would disturb the peace of the empire if he ascended the throne of Brunswick. As a result, Brunswick was ruled by a regency until 1913, when his son, also named Ernest Augustus, married the German Emperor's daughter, Princess Viktoria Luise and swore allegiance to the German Empire. The Duke then renounced his claim to Brunswick in favour of his son, and the Bundesrat allowed the younger Ernest Augustus to take possession of Brunswick as a kind of dowry compensation for Hanover. The German-Hanoverian Party, which at times supported secession from the Reich, demanded a separate status for the province in the Reichstag. The party existed until banned by the Nazi government.
Phosphorus pentachloride: SO2 + PCl5 → SOCl2 + POCl3 Chlorine and sulfur dichloride: SO2 + Cl2 + SCl2 → 2 SOCl2 SO3 + Cl2 + 2SCl2 → 3 SOCl2 Phosgene: SO2 + COCl2 → SOCl2 + CO2 The second of the above five reactions also affords phosphorus oxychloride (phosphoryl chloride), which resembles thionyl chloride in many of its reactions. They may be separated by distillation, since thionyl chloride boils at a much lower temperature than phosphoryl chloride.
According to the European Union Drugs Agency, the estimated minimum lethal dose is 1.2 grams. However, sensitive individuals have died from as little as 30 milligrams applied to mucous membranes-an amount that is 40 times less than the minimum lethal dose. In contrast, addicts may tolerate doses as high as 5 grams per day. Use of cocaine causes abnormally fast heart rhythms and a marked elevation of blood pressure (hypertension), which can be life-threatening. This can lead to death from acute myocardial infarction, acute respiratory failure (i.e., hypoxemia, with or without hypercapnia), stroke, cerebral hemorrhage, and sudden cardiac arrest. Overdose can also cause acute hepatotoxicity—typically due to toxic metabolites—though most cases resolve quickly; however, fatal outcomes from multiple organ dysfunction syndrome are possible, and there is no specific antidote. Cocaine overdose may result in hyperthermia as stimulation and increased muscular activity cause greater heat production. Heat loss is also inhibited by the cocaine-induced vasoconstriction. In 2024, drug-related deaths in England and Wales reached their highest level in three decades, with a notable increase in fatalities involving cocaine and experts urging urgent government intervention to address the crisis. Martin Powell, from the charity Transform, which campaigns for the legal regulation of drugs, suggested that the recent rise in cocaine-related deaths in the UK may be due to the increased purity of cocaine, leading users to consume it more frequently and alongside other substances.
=== Catalyst support === Magnetic nanoparticles are of potential use as a catalyst or catalyst supports. In chemistry, a catalyst support is the material, usually a solid with a high surface area, to which a catalyst is affixed. The reactivity of heterogeneous catalysts occurs at the surface atoms. Consequently, great effort is made to maximize the surface area of a catalyst by distributing it over the support. The support may be inert or participate in the catalytic reactions. Typical supports include various kinds of carbon, alumina, and silica. Immobilizing the catalytic center on top of nanoparticles with a large surface to volume ratio addresses this problem. In the case of magnetic nanoparticles it adds the property of facile a separation. An early example involved a rhodium catalysis attached to magnetic nanoparticles .
Sources: en.wikipedia.org
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.
Naming for research peptides is not standardised, and suppliers sometimes apply the same label to different chain lengths. Certificates of analysis and mass data are the practical way to determine what a given lot contains.
The fragment commonly cited under this label is reported near 889 Da, and the parent protein near 4963 Da. Reported values shift with the exact sequence and with residual counter-ions or water in the sample.
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.