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.
Updated 2026-05-22. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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 interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
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.
Sigma is the Sigma-Aldrich's main biochemical supplier, with offerings including antibiotics, buffers, carbohydrates, enzymes, forensic tools, hematology and histology, nucleotides, proteins, peptides, amino acids and their derivatives.
Oxazepam is generally less toxic in overdose than other benzodiazepines. Important factors which affect the severity of a benzodiazepine overdose include the dose ingested, the age of the patient, and health status prior to overdose. Benzodiazepine overdoses can be much more dangerous if a coingestion of other CNS depressants such as opiates or alcohol has occurred. Symptoms of an oxazepam overdose include:
Biden made several false or exaggerated claims about his early life: that he had earned three degrees in college, that he attended law school on a full scholarship, that he had graduated in the top half of his class, and that he had marched in the civil rights movement. The limited amount of other news about the presidential race amplified these disclosures, and on September 23, 1987, Biden withdrew his candidacy.
Liraglutide and semaglutide should not be used in those with a personal or family history of medullary type thyroid cancers as they may increase the risk of these types of tumors. Their use is further contraindicated in those with acute kidney injury, gallbladder disease or a history of pancreatitis. The FDA prescribing information for semaglutide recommends monitoring for depression or suicidal thoughts during treatment, though a real-world retrospective study of adolescents with obesity found that treatment with liraglutide or semaglutide was associated with a reduced risk for suicidal ideation or attempt. Setmelanotide is approved for children six years or older with certain types of secondary obesity. It may cause skin hyperpigmentation or other dermatologic effects as well as gastrointestinal side effects, with rare instances of depression and suicidal ideation. Metformin is often used off-label in children or adolescents with obesity, and has been found to cause a 1.1 decrease in BMI. A Cochrane review in 2016 concluded that medications might reduce BMI and bodyweight to a small extent in obese children and adolescents. This conclusion was based only on low-quality evidence.
Sources: en.wikipedia.org
As of 2021, the largest producers of milk powder are New Zealand, China, Argentina and Brazil. European production of milk powder in fiscal year 2019–2020 was estimated at around 3.0 million tonnes of which the main volume was exported in bulk packing or consumer packs. Australia also has a significant milk powder export industry, exporting over 13,000 tonnes of skim and whole milk powder in fiscal year 2020–2021, to a value of approximately AUD $83 000 000. Brands on the market include Nido, from the company Nestlé, Incolac from the company Milcobel, Dutch Lady from FrieslandCampina and Puck from Arla Foods. Some of the largest businesses in the industry are Nestlé, Danone, Lactalis, Fonterra, FrieslandCampina, Dean Foods, Arla Foods, Dairy Farmers of America, Kraft Foods, Saputo, and Parmalat.
Gutierrez-Marcos JF, Roberts MA, Campbell EI, Wray JL (1996). "Three members of a novel small gene-family from Arabidopsis thaliana able to complement functionally an Escherichia coli mutant defective in PAPS reductase activity encode proteins with a thioredoxin-like domain and "APS reductase" activity". Proc. Natl. Acad. Sci. U.S.A. 93 (23): 13377–82. Bibcode:1996PNAS...9313377G. doi:10.1073/pnas.93.23.13377. PMC 24101. PMID 8917599. Setya A, Murillo M, Leustek T (1996). "Sulfate reduction in higher plants: Molecular evidence for a novel 5′-adenylylsulfate reductase". Proc. Natl. Acad. Sci. U.S.A. 93 (23): 13383–8. Bibcode:1996PNAS...9313383S. doi:10.1073/pnas.93.23.13383. PMC 24102. PMID 8917600. Bick JA, Aslund F, Chen Y, Leustek T (1998). "Glutaredoxin function for the carboxyl-terminal domain of the plant-type 5′-adenylylsulfate reductase". Proc. Natl. Acad. Sci. U.S.A. 95 (14): 8404–9. Bibcode:1998PNAS...95.8404B. doi:10.1073/pnas.95.14.8404. PMC 20988. PMID 9653199.
Calcium gluconate is the calcium salt of gluconic acid and is used as a mineral supplement and medication. As a medication it is used by injection into a vein to treat low blood calcium, high blood potassium, and magnesium toxicity. Supplementation is generally only required when there is not enough calcium in the diet. Supplementation may be done to treat or prevent osteoporosis or rickets. It can also be taken by mouth but is not recommended for injection into a muscle. Side effects when injected include slow heart rate, pain at the site of injection, and low blood pressure. When taken by mouth side effects may include constipation and nausea. Blood calcium levels should be measured when used and extra care should be taken in those with a history of kidney stones. At normal doses, use is regarded as safe in pregnancy and breastfeeding. Calcium gluconate is made by mixing gluconic acid with calcium carbonate or calcium hydroxide. Calcium gluconate came into medical use in the 1920s. It is on the World Health Organization's List of Essential Medicines. Calcium gluconate is available as a generic medication. It is closely related to calcium borogluconate, which is commonly used in veterinary medicine owing to its higher solubility. It is used for intravenous administration of calcium, notably in ruminants.
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.