This is a working overview of actin-binding motif, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-04-18 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Generic designation | Synthetic thymosin beta-4 N-terminal fragment | Peptide nomenclature varies by supplier |
| Peptide length | Approximately 17 amino acid residues | Reported length sometimes differs between sources |
| N-terminal modification | Acetyl group | Affects mass and chromatographic behaviour |
| Compound class | Small synthetic peptide | Not a small-molecule drug |
| Common synonyms | TB4 fragment; thymosin beta-4 fragment | Naming is inconsistent in popular media |
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.
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.
Purity is normally assessed by reversed-phase HPLC, with the main peak reported as a percentage of total peak area, while identity is confirmed by mass spectrometry. Electrospray and MALDI-TOF instruments are both used, and the observed mass is compared with the value calculated from the stated sequence. Ion-exchange or size-exclusion methods appear where aggregation or charge variants are of interest. Water content, counter-ion content and residual trifluoroacetate from purification are separate variables that can shift the measured mass and should be weighed when reading a certificate of analysis.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
== Definition == Carbapenem-resistant Enterobacteriaceae (CRE) have been defined as carbapenem-nonsusceptible and extended-spectrum cephalosporin-resistant Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae complex, Klebsiella pneumoniae, or Klebsiella oxytoca. Some exclude ertapenem resistance from the definition.
The Downstream-peptide motif refers to a conserved RNA structure identified by bioinformatics in the cyanobacterial genera Synechococcus and Prochlorococcus and one phage that infects such bacteria. It was also detected in marine samples of DNA from uncultivated bacteria, which are presumably other species of cyanobacteria. Downstream-peptide RNAs are found upstream of short open reading frames (ORFs) that are predicted to encode short peptides (usually between 17 and 100 amino acids). One of the ORFs is apparently down-regulated when cells are grown with an insufficient supply of nitrogen sources. The Downstream-peptide motif has a structural resemblance to a different candidate RNA structure called the glnA RNA motif which was shown to be a functional glutamine binding riboswitch in cyanobacteria. The most striking similarity is the nucleotide conservation within the P1 stem of both motifs, and this and other similarities was discussed previously. It was hypothesized that Downstream-peptide RNAs correspond to riboswitches, based on multiple lines of evidence. First, glnA RNAs are often located in the presumed 5′ untranslated regions of multiple classes of genes involved in nitrogen metabolism. This, and other evidence, suggests that glnA RNAs are riboswitches, and their structural similarity to Downstream-peptide RNAs in turn suggests that Downstream-peptide RNAs are also riboswitches.
Throughout the 15th and 16th centuries, Portuguese explorers sailed the coast of Africa, established trading posts [[Economic history of Portugal#Expansion of the Portuguese empire (15th and 16th centuries)|for commodities]] especially gold and slaves, explored the Indian Ocean and eastern Asia, and established trade routes in most of southern Asia, taxing most trade criss-crossing the Indian Ocean. However, by the 16th century its enterprise in Asia was already in decline. The 1494 Treaty of Tordesillas divided newly encountered non-European territories between Portugal and Spain along a meridian west of Cape Verde, while the 1529 Treaty of Zaragoza extended this partition to the Pacific Ocean. In 1498, Vasco da Gama reached India by sea, and two years later Pedro Álvares Cabral landed in Brazil and claimed it for Portugal. During the 15th century, Portugal established the transatlantic slave-trade circuits and, by the mid-19th century, had become one of the longest-active and a significant participant in the Atlantic slave trade.
By the turn of the 20th century, the science of forensics had become largely established in the sphere of criminal investigation. Scientific and surgical investigation was widely employed by the Metropolitan Police during their pursuit of the mysterious Jack the Ripper, who had killed a number of women in the 1880s. This case is a watershed in the application of forensic science. Large teams of policemen conducted house-to-house inquiries throughout Whitechapel. Forensic material was collected and examined. Suspects were identified, traced and either examined more closely or eliminated from the inquiry. Police work follows the same pattern today. Over 2000 people were interviewed, "upwards of 300" people were investigated, and 80 people were detained. The investigation was initially conducted by the Criminal Investigation Department (CID), headed by Detective Inspector Edmund Reid. Later, Detective Inspectors Frederick Abberline, Henry Moore, and Walter Andrews were sent from Central Office at Scotland Yard to assist. Initially, butchers, surgeons and physicians were suspected because of the manner of the mutilations. The alibis of local butchers and slaughterers were investigated, with the result that they were eliminated from the inquiry. Some contemporary figures thought the pattern of the murders indicated that the culprit was a butcher or cattle drover on one of the cattle boats that plied between London and mainland Europe. Whitechapel was close to the London Docks, and usually such boats docked on Thursday or Friday and departed on Saturday or Sunday.
Sources: en.wikipedia.org
The brain's hypothalamus begins to release pulses of GnRH. Cells in the anterior pituitary respond by secreting LH and FSH into the circulation. The ovaries or testes respond to the rising amounts of LH and FSH by growing and beginning to produce estradiol and testosterone. Rising levels of estradiol and testosterone produce the body changes of female and male puberty. The onset of this neurohormonal process may precede the first visible body changes by 1–2 years.
28 Malay representatives, including all the chief ministers, 14 Chinese representatives, 6 Indian representatives, and 14 Europeans (the ex officio and official members). Dato' Onn Jaafar stressed at the first meeting that the citizens of the Federation of Malaya did not want the interference of external powers in the affairs of the Federation; the Chinese representative Ong Chong Keng asserted that the Chinese people would be loyal to the Federation of Malaya. At this first council meeting, several minor committees were formed:
=== Social brain interconnectivity === A number of discrete brain regions and networks among regions that are involved in dealing with other people have been discussed together under the rubric of the social brain. As of 2012, there is a consensus that autism spectrum is likely related to problems with interconnectivity among these regions and networks, rather than problems with any specific region or network.
Sources: en.wikipedia.org
== Pharmacology == Like ALD-52 (1A-LSD), 1P-LSD is believed to act as a prodrug for LSD via hydrolysis of the propionyl group. When 1P-LSD is incubated in human serum or liver cells, administered intravenously to rats, or administered either orally or intravenously to human subjects, high levels of LSD and relatively low levels of 1P-LSD are quickly detected, demonstrating that 1P-LSD is rapidly hydrolyzed into LSD in vivo following ingestion. Indeed, following intravenous administration in humans 1P-LSD is detectable in serum for no longer than 4 hours, after which it is completely converted to LSD. These findings are supported by the similar duration and behavioral effects of 1P-LSD and LSD in both animal and human experiments.
Two different Dromaius species were present in Australia at the time of European settlement, and one additional species is known from fossil remains. The insular dwarf emus, D. n. baudinianus and D. n. minor, originally present on Kangaroo Island and King Island respectively, both became extinct shortly after the arrival of Europeans. D. n. diemenensis, another insular dwarf emu from Tasmania, became extinct around 1865. The mainland subspecies, D. n. novaehollandiae, remains common. The population of these birds varies from decade to decade, largely being dependent on rainfall; in 2009, it was estimated that there were between 630,000 and 725,000 birds. Emus were introduced to Maria Island off Tasmania, and Kangaroo Island off the coast of South Australia, during the 20th century. The Maria Island population died out in the mid-1990s. The Kangaroo Island birds have successfully established a breeding population. In 1912, the Australian ornithologist Gregory M. Mathews recognised three living subspecies of emu, D. n. novaehollandiae (Latham, 1790), D. n. woodwardi Mathews, 1912 and D. n. rothschildi Mathews, 1912. The Handbook of the Birds of the World, however, argues that the last two of these subspecies are invalid; natural variations in plumage colour and the nomadic nature of the species make it likely that there is a single race in mainland Australia. Examination of the DNA of the King Island emu shows this bird to be closely related to the mainland emu and hence best treated as a subspecies.
Pradhan Mantri Krishi Sinchai Yojana (Hindi: प्रधानमंत्री कृषि सिंचाई योजना) is a national mission to improve farm productivity and ensure better utilization of the resources in the country. The budget of ₹53 billion (US$550 million) in a time span of one year 2015-2016 has been allocated to this scheme. The decision was taken on 1 July 2015 at the meeting of Cabinet Committee on Economic Affairs, approved with an outlay of 50000 crore for period of 5 years (2015-16 to 2019-20).
Sources: en.wikipedia.org
It is a synthetic peptide based on a short sequence near the start of thymosin beta-4. It is supplied as a research chemical rather than as a licensed pharmaceutical product.
No. Thymosin beta-4 is the full-length protein of about forty-three amino acids, while the fragment covers only its beginning. The two are related but are not interchangeable in experimental or analytical terms.
The label is a catalogue designation that became common in non-technical discussion. Scientific papers usually refer to the fragment by sequence or as a thymosin beta-4 N-terminal peptide.
TB-500 is a name used for a short synthetic peptide fragment taken from the actin-binding region of thymosin beta-4. Material sold under this label is usually a lyophilized powder supplied for laboratory research rather than a licensed medicine. The commonly cited sequence is LKKTETQ.