actin-binding motif 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 2026-07-21 and is reviewed periodically as new material appears.
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.
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.
| 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 |
Interest in the peptide grew during the 2000s and 2010s, when studies of tendon and ligament injuries in horses reported changes in lesion size after treatment. Those reports circulated widely outside the scientific literature and shaped much of the current online discussion. Subsequent reviews noted inconsistent study design, small groups, and a shortage of independent replication. Popular descriptions often blur the line between the fragment, the complete protein, and unrelated growth factors, which complicates comparisons across sources.
TB-500 is a synthetic peptide whose sequence corresponds to a short fragment near the N-terminus of thymosin beta-4, a small protein present in most mammalian cells. The fragment is commonly cited as containing the actin-binding region of the parent molecule, which is why it appears in laboratory work on cell migration and tissue repair. Suppliers distribute it as a lyophilised powder intended for research use. Its identity is defined by amino acid sequence and by the presence of an acetyl group on the N-terminal residue.
Full-length thymosin beta-4 consists of roughly forty-three amino acids and ranks among the more abundant small proteins in the cytoplasm. The fragment is much shorter, so it cannot reproduce every function attributed to the intact molecule. In cell culture, short actin-binding motifs can interfere with filament dynamics and cell movement, but such observations come from controlled experiments rather than from whole-animal work. Whether a truncated fragment produces the same effects as the parent protein remains an open question.
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.
In the Philippines, the first Mister Donut store opened in 1982 in Manila and has become the country's second largest doughnut chain, with Dunkin' Donuts as its main competitor. In 1995, the Ramcar Group took over the Philippine franchise of Mister Donut through its subsidiary, Food Fest, Inc. In 1997, Mister Donut helped finance the country's first ever feature-length animated film, Adarna: The Mythical Bird. Of its 1,800 outlets, the majority are stalls, often located inside shopping malls, while 200 are full-scale stores. Mister Donut products are also sold in 7-Eleven stores and KFC restaurants, the latter also franchised locally by Ramcar. Some locations sell coffee, but they mostly focus on doughnuts, including pasalubong, gifts by visitors to friends and family. The doughnuts sold are adjusted to suit the local market, with smaller sizes, therefore cheaper, and different flavors.
== Locomotion == The slime coat of some fish aids in more efficient swimming by reducing drag, attributed to the Toms effect. Slime can reduce the friction experienced by the fish by up to 65%. Generally, the faster the fish, the greater reduction in drag provided by the slime, but there are a few exceptions. In schooling fish, slime shed by leading fish is thought to provide a hydrodynamic benefit to following fish.
=== Discovery === Gliotoxin was first described in 1936 by Weindling and Emerson as a metabolic product from the fungus Trichoderma lignorum. However, afterwards Weindling reported that the fungus had been misidentified based on the advice of C. Thom and M. Timonin, and that the compound instead was isolated from Gliocladium finbriatum. Contention remains on whether the fungus used by Weindling was G. finbriatum or a species of Trichoderma. The chemical structure of gliotoxin was resolved in 1958 by Bell et al. by treatment of gliotoxin on alkaline alumina. Bell and colleagues were able to determine through their structural analyses that the attachment of the disulfide bridge could not occur at any positions other than 3 and 11. This led to the elucidation that gliotoxin was an anhydropeptide related to the amino acids serine and phenylalanine. Additionally, they found that it was noteworthy that the α-carbon atoms of the cooperating α-thio-α-amino acids must have the same configuration.
== See also == Myanmar Politics of Myanmar List of heads of state of Myanmar List of Burmese monarchs List of heads of state of Myanmar since 1948 List of colonial governors of Burma Vice President of Myanmar Prime Minister of Myanmar List of heads of government of Myanmar since 1948 State Counsellor of Myanmar Lists of office-holders
Sources: en.wikipedia.org
The Raleigh area has hosted the Professional Golfers' Association (PGA) Nationwide Tour Rex Hospital Open since 1994, with the current location of play at Raleigh's Country Club at Wakefield Plantation. Nearby Prestonwood Country Club hosts the PGA SAS Championship every fall.
Curran TW, Lawrence DN, Jaffe HS, Kaplan JE, Zyla LD, Chamberland M, Weinstein R, Lui KJ, Schonberger LB, Spira TJ, Alexander WJ, Swinger G, Ammann AJ, Solomon S, Auerbach D, Mildvan D, Stoneburner R, Jason JM, Haverkos HW, Evat BL. Acquired immunodeficiency associated with transfusions. NEJM, 310:69-75, 1984. Cowan MJ, Hellmann D, Chudwin D, Wara DW, Chang RS, Ammann AJ. Maternal transmission of acquired immune deficiency syndrome. Pediat, 73:382-386, 1984. Cao Y, Krogstad P, Korber BT, Koup RA, Muldoon M, Macken C, Song J-L, Jin Z, Zhao J-Q, Clapp S, Chen ISY, Ho DD., Ammann AJ and the Ariel Project Investigators. Maternal HIV-1 viral load and vertical transmission of infection: The Ariel Project for the prevention of HIV transmission from mother to infant. Nature Medicine 3: 549-552 1997. Ammann AJ. HIV in China: An Opportunity to Halt an Emerging Epidemic. Ammann AJ AIDS Patient Care and STDs 14:109-112, 2000. Ammann AJ. Introduction to the Second Conference on Global Strategies for the Prevention of HIV Transmission from Mothers to Infants. Annals NY Academy of Sciences 918:1-2, 2000. Kim JY, Ammann AJ. Is the "3 by 5" initiative the best approach to tackling the HIV pandemic? PLoS Med. 2004 Nov;1(2):e37. Epub 2004 Nov 30. Ammann AJ. Feminization of the HIV Epidemic. Radix 32:8-13 2006 Ammann AJ. Advances in HIV Care and Treatment in Resource Poor Countries. HIV Therapy. 2009 3:329-338.
== Ligands == Ac-Val-Gln-(pI)DPhe-DTic-NH2, first MC3 selective agonist, 100x selectivity over MC4. Ac-Val-Gln-DBip-DTic-NH2, 140x selectivity over MC4. Pyrrolidine bis-cyclic guanidines, non-peptide small molecule MC3 agonists, good selectivity over MC4 but not over MC1 or MC5. SHU-9119, mixed MC3/MC4 antagonist.
== Research == A 2014 Cochrane review found insufficient evidence to make a conclusion about its use for the prevention of heart disease. A 2016 Cochrane review concluded that CoQ10 had no effect on blood pressure. A 2021 Cochrane review found "no convincing evidence to support or refute" the use of CoQ10 for the treatment of heart failure. A 2017 meta-analysis of people with heart failure taking 30–100 mg/d of CoQ10 found a 31% lower mortality and increased exercise capacity, with no significant difference in the endpoints of left heart ejection fraction. A 2021 meta-analysis found that CoQ10 was associated with a 31% lower all-cause mortality in HF patients. In a 2023 meta-analysis of older people, ubiquinone had evidence of a cardiovascular effect, but ubiquinol (the reduced form) did not. Although CoQ10 has been studied as a potential remedy to treat purported muscle-related side effects of statin medications, the results were mixed. Although a 2018 meta-analysis concluded that there was preliminary evidence for oral CoQ10 reducing statin-associated muscle symptoms, including muscle pain, muscle weakness, muscle cramps, and muscle tiredness, 2015 and 2024 meta-analysis found that CoQ10 had no effect on statin myopathy.
UV-Vis spectrophotometer: Measures light absorption in UV and visible ranges (200-800 nm). Used for quantification of many inorganic and organic compounds. Infrared spectrophotometer: Measures infrared light absorption, allowing identification of chemical bonds and functional groups. Atomic absorption spectrophotometer (AAS): Uses absorption of light by vaporized analyte atoms to determine concentrations of metals and metalloids. Fluorescence spectrophotometer: Measures intensity of fluorescent light emitted from samples after excitation. Allows highly sensitive analysis of samples with native or induced fluorescence. Colorimeter: Simple spectrophotometers used to measure light absorption for colorimetric assays and tests.
Sources: en.wikipedia.org
== Modes of separation == The separation of compounds by capillary electrophoresis is dependent on the differential migration of analytes in an applied electric field. The electrophoretic migration velocity (
=== Casting === In February 2025, Jessica Lange, who starred in the first four seasons and briefly appeared in the eight season in 2018, answered a question about her potential return for the thirteenth season: "Oh Christ, no. I mean, I haven't done it for more than 10 years, 12 years, so, no, I'm not doing it." Murphy revealed that Lange was the first person he turned to about the return and she agreed under the condition she would have a musical number. Subsequently, he turned to Sarah Paulson and Evan Peters, who agreed instantly. They both last appeared in the tenth season in 2021. In October 2025, Lange, Paulson, Peters, Emma Roberts, Billie Lourd, Kathy Bates, Angela Bassett, Leslie Grossman, Jessica Lange, and Gabourey Sidibe were all confirmed to return for the thirteenth season, along with the newcomer Ariana Grande. Bates, Bassett and Sibide last appeared in the eight season in 2018. Bates revealed that she would have only one day of filming. In February 2026, John Waters joined the cast, while Joey Pollari joined in April, and Alex Consani and Paul Anthony Kelly joined in May. John Carroll Lynch and Matt Fraser were also confirmed to reprise their roles from Freak Show, with Mena Suvari and Berto Colón also joining the cast. In July, Frances Conroy was confirmed to reprise her role from Coven, with Avantika, Grace Dumdaw, Cara Delevingne, and Charlie Carver also joining the cast. In July 2026, it was reported that Grande dropped out due to scheduling conflicts with the season's production schedule and her Eternal Sunshine Tour.
== Detecting peptides == Typically, peptide signals are detected at the MS1 level and distinguished from chemical noise through their characteristic isotopic pattern. These patterns are then tracked across the retention time dimension and used to reconstruct a chromatographic elution profile of the mono-isotopic peptide mass. The total ion current of the peptide signal is then integrated and used as a quantitative measurement of the original peptide concentration. For each detected peptide, all isotopic peaks are first found and the charge state is then assigned. Label-free quantification may be based on precursor signal intensity and has problems due to isolation interference: in high-throughput studies, the identity of the peptide precursor ion being measured could easily be a completely different peptide with a similar m/z ratio and which elutes in a time frame overlapping with that of the former peptide. Spectral counting has problems due to the fact that the peptides are identified, thus making it necessary to run an additional MS/MS scan which takes time and therefore reduces the resolution of the experiment.
Roller chains are used in low- to mid-speed drives at around 600 to 800 feet per minute; however, at higher speeds, around 2,000 to 3,000 feet per minute, V-belts are normally used due to wear and noise issues. A bicycle chain is a roller chain. Bicycle chains may have a master link, or may require a chain tool for removal and installation. A similar but larger and thus stronger chain is used on most motorcycles although it is sometimes replaced by either a toothed belt or a shaft drive, which offer lower noise level and fewer maintenance requirements. A timing chain is a roller chain used in some internal combustion automobile engines to drive a camshaft. Very high performance engines often use gear drive, and starting in the early 1960s toothed belts were used by some manufacturers.
=== Patenting === In the U.S., efforts into creating a chimeric entity appeared to be legal when the topic first came up. Developmental biologist Stuart Newman, a professor at New York Medical College in Valhalla, N.Y., applied for a patent on a human-animal chimera in 1997 as a challenge to the U.S. Patent and Trademark Office and the U.S. Congress, motivated by his moral and scientific opposition to the notion that living things can be patented at all. Prior legal precedent had established that genetically engineered entities, in general, could be patented, even if they were based on beings occurring in nature. After a seven-year process, Newman's patent finally received a flat rejection. The legal process had created a paper trail of arguments, giving Newman what he claimed was a victory. The Washington Post ran an article on the controversy that stated that it had raised "profound questions about the differences—and similarities—between humans and other animals, and the limits of treating animals as property."
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.
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.