If you have been reading about actin binding 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.
Updated 2026-02-03. Numbers and descriptions here follow the published literature rather than marketing material.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
Laboratory work on thymosin beta-4 describes binding to monomeric actin and effects on cell migration, angiogenesis, and inflammatory signaling in cultured cells. Animal models have examined skin, corneal, and cardiac repair after injury, with outcomes reported mainly in preclinical literature. Most of that evidence concerns the parent protein rather than preparations labelled TB-500, so extrapolation from animal findings to a specific commercial product remains uncertain. Whether the two behave identically in living systems has not been established in controlled human studies.
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.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | Approximately 4963 Da for full-length thymosin beta-4 | Value applies to the parent protein; fragment products may differ |
| Appearance | White to off-white lyophilized powder | Typical form of supplied synthetic peptide |
| Solubility | Freely soluble in water | Polar peptide; dissolves readily in aqueous buffer |
| Storage of dry powder | −20 °C, desiccated, protected from light | Standard laboratory practice for peptides |
| Typical detection method | Liquid chromatography–tandem mass spectrometry | Used in purity testing and anti-doping analysis |
Research peptides are typically supplied as a white to off-white lyophilised powder in a sealed vial. The dry solid is more stable than a solution and is normally kept refrigerated or frozen until use. Dissolution is usually done in water, phosphate-buffered saline or a similar aqueous medium, depending on the assay. Because the material is hygroscopic and easily contaminated, opening vials in a low-humidity environment and recording the lot number before use are standard laboratory practices.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
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.
== Mistaken portrait == For two centuries, until the discovery of the error in 2005, books, paintings and articles had incorrectly shown a profile portrait of the obscure French politician Louis Legendre (1752–1797) as a portrait of the mathematician. The error arose from the fact that the sketch was labelled simply "Legendre" and appeared in a book along with contemporary mathematicians such as Lagrange. One of only two known portraits of Legendre, rediscovered in 2008, is found in the 1820 book Album de 73 portraits-charge aquarellés des membres de I'Institut, a book of caricatures of seventy-three members of the Institut de France in Paris by the French artist Julien-Léopold Boilly as shown below. The other portrait is from the book Le Panthéon scientifique de la tour Eiffel.
=== Presentation === The clinical manifestations of this disease are anaemia, jaundice, fever, hepatomegaly, splenomegaly, lymphadenopathy, haematochezia and persistent bleeding from the nose, oral cavity and the tips, margins and outer surface of the pinnae. Other features include lethargy, loss of appetite, weakness, weight loss, dyspnoea, petechiae and haematemesis.
Come What(ever) May was met with generally positive critical reviews. Several reviewers noted how it helped to further establish Stone Sour. Chad Bower of About.com stated that the band had "progressed a lot since their debut", noting that the album was "very diverse and [allows] the band to show many different sides of their musical personality". Megan Frye of Allmusic opened her review of the album by distinguishing what sets Stone Sour apart musically, writing "[it's their] ability to create smooth, radio-friendly alternative metal songs while simultaneously not boring the people who have heard way too much from post-grunge groups." On a similar note, Michael Melchor of 411mania said, "The band is much better at the craft of songwriting than many of their peers." In contrast, reviewer William Fry of IGN criticized the album, writing, "Stone Sour doesn't do anything inspired, original, or fresh here," even calling the album "completely misdirected, and stonewalled". A particular point of interest for reviewers was how Come What(ever) May is more melodic than the band's previous album Stone Sour. Melchor of 411mania said the album is "much more liberal with the balladry and acoustic sounds than its predecessor"; of the track "Sillyworld" he said, "It sounds like what Nickelback could be if Chad Kroeger could write a good melody." In his review, Chad Bower labeled Come What(ever) May as a "very melodic and accessible album" writing that "it has a little something for everyone". Similarly, Megan Frye praised the album as an "unyielding effort from a promising talent".
Sources: en.wikipedia.org
4 On 21 December 1995, a major reshuffle took place amongst existing Ministers, mainly to discharge particular Ministers of portfolios which had proven troublesome for the government. 5 On 26 April 1996, George Cash resigned from the ministry due to ill health. Graham Kierath and Kevin Minson adopted his portfolios, whilst Norman Moore was elected leader of the Government in the Legislative Council four days later.
A study on the age of the carbonate thin layers covering or underlying rock art from the Cave of Altamira (Spain), providing evidence of several periods of cave art from the ceiling of the studied cave, is published by Pons-Branchu et al. (2026). Evidence from the Velika Pećina, Velika Vranovica and Pećina kod Stene cave sites (Serbia), indicative of human presence in central Balkans during the Last Glacial Maximum, is presented by Kuhn et al. (2026). Masojć et al. (2026) describe a Late Pleistocene human tooth from the Khutul Usny Cave site, representing the first fossil of an early Homo sapiens in Mongolia with secure geological context and providing evidence of presence of the species in southern Mongolia around the onset of the Last Glacial Maximum. A study on the frontal and mandibular morphology of the Red Deer Cave people, interpreted as consistent of affinities with Homo sapiens and indicative of diversity cranial morphology of late Pleistocene hominins from eastern Asia, is published by Fan et al. (2026). Evidence indicating that Solutrean artifacts from the Peña Capón rock shelter (Muriel-Tamajón, Spain) were sourced 600 to 700 kilometers away from this site, in the present-day territory of southwest France, is presented by Sánchez de la Torre et al. (2026). Nash et al. (2026) report rediscovery of putative Upper Paleolithic cave art from the Bacon Hole site (Wales, United Kingdom) originally discovered by William Sollas and Henri Breuil in 1912 and support the interpretation of the studied horizontal lines as cave art. Reiche et al.
To assist with settling on the best form of treatment for cauliflower ear, Yotsuyanagi et al. created a classification system for deciding when surgery is needed and as a guide to what the best approach would be.
Sources: en.wikipedia.org
=== Signaling pathways used in electrotaxis === In the absence of a complete explanation of the mechanism behind electrotaxis, certain signaling pathways have been found to have an involvement in electrotaxis. In both neutrophils and keratinocytes, Zhau et al. experimentally determined that physiological strength EFs induce phosphorylation of extracellular-signal-regulated kinase (ERK), p38 mitogen-activated Kinase (MAPK), Src, and Akt on ser 473. In chemotaxis, Src and Akt are polarized by phosphatidylinositol-3-OH kinase-γ (PI(3)Kγ) activation and inhibition of phosphate tensin homolog (PTEN). In the experiment, phosphorylated Src polarized in the direction of migration when influenced by physiological strength EFs, as is also seen in chemotaxis. Phosphatidylinositol-3,4,5-triphosphate (PtdIns(3,4,5)P3), another molecule used in signaling, polarized to the leading edge of HL60 cells when subjected to an EF. Upon reversal of the EF, polarization PtdIns(3,4,5)P3 rapidly reversed to the new direction of migration. Treatment with lantruculin did not prevent this from occurring, indicating that polarization is not actin-dependent. Cells in which the gene encoding PI(3)Kγ, Pik3cg, was disrupted exhibited reduced electrotaxic responses. Pharmocological inhibition of PI(3)K in keratinocytes produced the same results. Similarly, genetic disruption of PTEN resulted in increased phosphorylation of ERK and Akt and a greater electrotaxic response. Consideration of these results suggests that PI(3)Kγ and PTEN are involved in the signaling pathway used in electrotaxis.
=== Early works and origins === The Fisher King first appears in Chrétien de Troyes's Perceval, the Story of the Grail in the late 12th century, but the character's roots may lie in Welsh mythology. He may be derived from the figure of Brân the Blessed in the Mabinogion. In the Second Branch of the Mabinogi, Bran has a cauldron that can resurrect the dead, albeit imperfectly: the revived dead can no longer speak. He gives this cauldron to the king of Ireland as a wedding gift for him and Bran's sister Branwen. Later, Bran wages war on the Irish and is wounded in the foot or leg, and the cauldron is destroyed. He asks his followers to sever his head and take it back to Britain, and his head continues talking and keeps them company on their trip. The group lands on the island of Gwales, where they spend 80 years in a castle of joy and abundance, but eventually they leave and bury Bran's head in London. This story has analogues in two other important Welsh texts: the Mabinogion tale "Culhwch and Olwen", in which King Arthur's men must travel to Ireland to retrieve a magical cauldron, and the poem The Spoils of Annwn, which speaks of a similar mystical cauldron sought by Arthur in the otherworldly land of Annwn.
=== Economic vegetarianism === Similar to environmental vegetarianism is the concept of economic vegetarianism. An economic vegetarian is someone who practices vegetarianism from either the philosophical viewpoint concerning issues such as public health and curbing world starvation, the belief that the consumption of meat is economically unsound, part of a conscious simple living strategy or just out of necessity. According to the Worldwatch Institute, "Massive reductions in meat consumption in industrial nations will ease their health care burden while improving public health; declining livestock herds will take pressure off rangelands and grainlands, allowing the agricultural resource base to rejuvenate. As populations grow, lowering meat consumption worldwide will allow more efficient use of declining per capita land and water resources, while at the same time making grain more affordable to the world's chronically hungry." According to estimates in 2016, adoption of vegetarianism would contribute substantially to global healthcare and environmental savings.
Sources: en.wikipedia.org
Not necessarily. TB-500 is a commercial label that suppliers apply to synthetic peptides described as thymosin beta-4 or a fragment of it. Published research most often studies the full-length protein, so statements about one do not automatically transfer to the other.
No. No major regulatory authority lists an approved product under this name, and no pharmacopoeial monograph exists for it. Material sold under the label is therefore supplied outside approved pharmaceutical channels, which affects the quality documentation available.
It falls within a prohibited class covering peptide hormones and growth factors, based on presumed effects on tissue repair and blood vessel formation. Anti-doping laboratories have published mass spectrometry methods for detecting thymosin beta-4 related peptides in urine samples.
No. Thymosin beta-4 is a 43-residue protein, while TB-500 matches only residues 17 to 23 of that chain. The two are related but differ in size, and a method that identifies one does not automatically identify the other.