If you have been reading about actin-binding motif 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 2026-01-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | Approximately 0.9 kDa | Depends on exact fragment sequence and counterion |
| Amino acid sequence | LKKTETQ (commonly cited) | Short actin-binding motif from thymosin beta-4 |
| Common salt form | Acetate salt | Trifluoroacetate also reported in research material |
| Reconstitution solvent | Sterile water or buffer | Gentle mixing; avoid vigorous agitation |
| Solution storage | -20 °C or lower | Aliquot to avoid repeated freeze-thaw cycles |
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.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
Identity and purity checks for peptide material typically combine reversed-phase high-performance liquid chromatography with mass measurement, since retention time alone cannot confirm a sequence. Mass measurement verifies the expected molecular mass within instrument tolerance, while chromatographic peak area provides a purity estimate. Anti-doping analysis of urine uses related but more sensitive workflows, sometimes after solid-phase extraction. For research material, batch documentation, certificate content, and independent testing are common points of scrutiny, because supply chains outside pharmaceutical regulation vary widely in the paperwork they provide.
=== The 53Mn – 53Cr chronometer === The short-lived 53Mn-53Cr chronometer is based on the radioactive decay of 53Mn to 53Cr with a half-life of 3.80 ± 0.23 million years. Because manganese and chromium are moderately volatile elements, their fractionation in the cooling solar nebula makes this chronometer particularly suited for dating volatile element depletion events in early Solar System materials. The initial homogeneous distribution of 53Mn in the Solar System, a prerequisite for its use as a chronometer, was established in early studies of Solar System materials. Applied to meteorites, 53Mn-53Cr systematics have provided key insights into the origin of chondrite parent bodies and the volatile element depletion history of the early Earth. The volatile element depletion of proto-Earth was established no later than ~3 million years after the formation of calcium-aluminium-rich inclusions (CAIs), contemporaneous with the dissipation of the protoplanetary disk, while full planetary accretion was completed within ~70 million years.
=== Antiviral activity === Lactoferrin in sufficient strength acts on a wide range of human and animal viruses based on DNA and RNA genomes, including the herpes simplex virus 1 and 2, cytomegalovirus, HIV, hepatitis C virus, hantaviruses, rotaviruses, poliovirus type 1, human respiratory syncytial virus, murine leukemia viruses and Mayaro virus. Activity against COVID-19 has been speculated but not proven. The most studied mechanism of antiviral activity of lactoferrin is its diversion of virus particles from the target cells. Many viruses tend to bind to the lipoproteins of the cell membranes and then penetrate into the cell. Lactoferrin binds to the same lipoproteins thereby repelling the virus particles. Iron-free apolactoferrin is more efficient in this function than hololactoferrin; and lactoferricin, which is responsible for antimicrobial properties of lactoferrin, shows almost no antiviral activity. Beside interacting with the cell membrane, lactoferrin also directly binds to viral particles, such as the hepatitis viruses. This mechanism is also confirmed by the antiviral activity of lactoferrin against rotaviruses, which act on different cell types. Lactoferrin also suppresses virus replication after the virus penetrated into the cell. Such an indirect antiviral effect is achieved by affecting natural killer cells, granulocytes and macrophages – cells, which play a crucial role in the early stages of viral infections, such as severe acute respiratory syndrome (SARS).
Dominic Lawson, Former editor of The Spectator magazine and Sunday Telegraph newspaper, has been writing column for The Independent since 2006; also writes for the Sunday Times Nigella Lawson, (born 6 January 1960) is an English food writer and television cook. In 1998, her first cookery book, How to Eat, was published and sold 300,000 copies, becoming a best-seller. Her second book, How to Be a Domestic Goddess, was published in 2000, winning the British Book Award for Author of the Year. Nicole Lampert, journalist and commentator. Former show business editor for the Daily Mail. Columnist for the Jewish Chronicle. Writes extensively about antisemitism and Israel for national newspapers. Norman Lebrecht (born 11 July 1948) is a British music journalist and author who specialises in classical music. Lebrecht worked at the Kol Yisrael news department, part of the Israel Broadcasting Authority. He returned to London in 1972, where he was a news executive Visnews Ltd. from 1973 to 1978;was a special contributor to The Sunday Times until 1991; in 2019, Lebrecht published Genius and Anxiety: How Jews Changed the World, 1847–1947. It was published by Oneworld (UK) in October 2019 and by Simon & Schuster (USA) in December 2019. Natasha Lehrer; journalist, writer and literary translator; her translations have received multiple awards, and been shortlisted for several prizes; was joint winner of Scott Moncrieff Prize for translation of Nathalie Léger's Suite for Barbara Loden.
According to the Journal Citation Reports, the journal has a 2014 impact factor of 5.03, ranking it second out of 30 journals in the category "Medical Laboratory Technology", 17th out of 153 journals in the category "Medicine, General & Internal" and 17th out of 123 journals in the category "Medicine, Research & Experimental"
In the Pilbara region of Western Australia, compelling evidence of early life was found in pyrite-bearing sandstone in a fossilized beach, with rounded tubular cells that oxidized sulfur by photosynthesis in the absence of oxygen. Carbon isotope ratios on graphite inclusions from the Jack Hills zircons suggest that life could have existed on Earth from 4.1 Gya. A 2024 study inferred LUCA's age as around 4.2 Gya (4.09–4.33 Gya) by analysing pre-LUCA gene duplicates, with calibration from fossil micro-organisms, much sooner after the origin of life than previously thought. The Pilbara region of Western Australia contains the Dresser Formation with rocks 3.48 Gya, including layered structures called stromatolites. Their modern counterparts are created by photosynthetic micro-organisms including cyanobacteria. These lie within undeformed hydrothermal-sedimentary strata; their texture indicates a biogenic origin. Parts of the Dresser formation preserve hot springs on land, but other regions seem to have been shallow seas. A molecular clock analysis suggests the LUCA emerged prior to 3.9 Gya.
Sources: en.wikipedia.org
Opium was traded from Egypt by the Phoenicians and Minoans to destinations around the Mediterranean Sea, including Greece, Carthage, and Europe. By 1100 BC, opium was cultivated on Cyprus, where surgical-quality knives were used to score the poppy pods, and opium was cultivated, traded, and smoked. Opium was also mentioned after the Persian conquest of Assyria and Babylonian lands in the 6th century BC.
== Anatomy == The blood–brain barrier is formed by special tight junctions between endothelial cells lining brain blood vessels. Blood vessels of all tissues contain this monolayer of endothelial cells, however only brain endothelial cells have tight junctions preventing passive diffusion of most substances into the brain tissue. The structure of these tight junctions was first determined in the 1960s by Tom Reese, Morris Kranovsky, and Milton Brightman. Furthermore, astrocytic "end feet", the terminal regions of the astrocytic processes, surround the outside of brain capillary endothelial cells". The astrocytes are glial cells restricted to the brain and spinal cord and help maintain blood-brain barrier properties in brain endothelial cells.
As a result, Singapore has increasingly used polders for reclamation works, a method most notably used at Tekong Island in which an area is enclosed and then pumped dry. The country is projected to reclaim roughly another 100 km2 (40 sq mi) by 2040, which includes major projects such as Tuas Port, the Long Island project located south of East Coast Park for commercial and residential developments, and an aviation park at Changi Bay.
A special form of clubbing is hypertrophic pulmonary osteoarthropathy (HPOA), known in continental Europe as Pierre Marie-Bamberger syndrome. This is the combination of clubbing and thickening of periosteum (connective tissue lining of the bones) and synovium (lining of joints), and is often initially diagnosed as arthritis. It is commonly associated with lung cancer.
Sources: en.wikipedia.org
==== Princes of the Royal Secret ==== In April 1818, a member of the Grand Orient de France named Louis de Clouet, who went by the Masonic codename d'Obernay, established a Grand Consistory of the Scottish Rite in Havana, Principes del Real Secreto (English: Princes of the Royal Secret). D'Obernay authorized the Grand Consistory to establish Lodges, chapters, and councils. He also authorized it to confer the 32nd Degree. The Grand Orient of France further authorized this work under the charter of the Grand Consistory dated April 7, 1819. Exactly how many Lodges were merged to create Principes del Real Secreto is debated. However, D'Obernay and this Grand Consistory did create several lodges, including L'Humanite, and La Constante Sophie, which received its charter directly from the Grand Orient of France. The Blue Lodges of the Grand Consistory were formed under the Gran Oriente Simbolico de la Nueva Thebaida (English: Symbolic Grand Orient of New Thebes), which was also known as the Gran Oriente Simbolico de la Isla de Cuba (English: Symbolic Grand Orient of the Island of Cuba). When the Grand Consistory was established, the Grand Orient of France relinquished their authority, handing it over to the National Grand Oriente of Spain. However, because the Grand Orient of Spain was bifurcated politically, the Cubans rejected its authority, preferring to remain autochthonous, instead of finding themselves on either side of the mainland Spanish divisions.
It has been long observed that the licking of their wounds by dogs might be beneficial. Indeed, a dog's saliva is bactericidal against the bacteria Escherichia coli and Streptococcus canis, although not against coagulase-positive Staphylococcus or Pseudomonas aeruginosa. Wound licking is also important in other animals. Removal of the salivary glands of mice and rats slows wound healing, and communal licking of wounds among rodents accelerates wound healing. Communal licking is common in several primate species. In macaques, hair surrounding a wound and any dirt is removed, and the wound is licked, healing without infection. An Elizabethan collar may be used on pet animals to prevent them from biting an injury or excessively licking it, which can cause a lick granuloma. These lesions are often infected by pathogenic bacteria such as Staphylococcus intermedius. Horses that lick wounds may become infected by a stomach parasite, Habronema, a type of nematode worm. The rabies virus may be transmitted between animals, such as the kudu antelopes by wound licking of wounds with residual infectious saliva.
Following a new level of cooperation between Roscomos and NASA in the 1990s the decision to implement the project that was called, the "most complex scientific and political multi-stage project ever undertaken by the Great Powers, the project promises to push the boundaries of what is possible, operates entirely in the New Frontier and represents a new epoch in this history of mankind" began. The station took multiple decades to develop and has been continually occupied since 2000.
According to legend, one of the first blue cheeses, Roquefort, was discovered when a young boy, eating bread and ewes' milk cheese, abandoned his meal in a nearby cave after seeing a beautiful girl in the distance. When he returned months later, the mold (Penicillium roqueforti) had transformed his cheese into Roquefort. Gorgonzola is one of the oldest known blue cheeses, having been created around AD 879, though it is said that it did not contain blue veins until around the 11th century. Stilton is a relatively new addition, becoming popular sometime in the early 1700s. Many varieties of blue cheese originated subsequently, such as the 20th century Danablu and Cambozola, which were an attempt to fill the demand for Roquefort-style cheeses.
Over the years, Ferasse has resisted Eastern Bloc pressure to break with South Africa. At one point Moscow threatened to set up a rival Federation, but the Rumanians, with whom the French have long had good relationships, stood by France. Moscow tried again later by threatening to call off the France v. USSR match in Toulouse in November 1978. Once again Ferasse held firm and the Russians went to France, where they were beaten 29-7 In September 1981, South Africa was due to play the Mid-West in Chicago. To avoid protestors, they drove 77 miles to Racine and played in front of 247 spectators, winning 46–12. By the time they returned to Chicago, none of the protestors knew that the game had happened. In 1989 a World XV, sanctioned by the IRB and funded by South African Breweries, played two tests against South Africa in 1989 in celebration of the centenary of the South African Rugby Board (SARB). The Springboks won both, by 20–19 at Newlands Stadium in Cape Town and the second test 22–16 on 2 September at Ellis Park in Johannesburg .
Sources: en.wikipedia.org
Dry lyophilized powder is usually kept frozen, desiccated, and out of direct light. Sealed vials are not opened until needed, because moisture uptake can degrade short peptides. Longer archival storage is often done at lower temperatures than routine working stock.
Reversed-phase liquid chromatography separates components and reports purity from peak area. Mass spectrometry confirms the molecular mass expected for the sequence. Additional approaches such as peptide mapping or amino acid analysis provide independent confirmation.
Reported percentages depend on the analytical method, the detection wavelength, and whether salts and water are counted. A value above ninety-five percent by chromatography does not by itself establish a correct sequence. Different suppliers also calculate purity against different reference standards.
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.