If you have been reading about reconstitution 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 2026-02-22. Numbers and descriptions here follow the published literature rather than marketing material.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
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.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
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.
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.
== Construction == The tablets were originally made of wood and wax, though only the wood was preserved and recoverable. A typical tablet would have been made of a thin piece of wood, 15–25 cm wide, with a rectangular depression carved into the centre. Warm beeswax, blackened by the addition of atramentum, would then be poured into the centre depression and allowed to cool. Once the wax had set, a metal stylus would be used to scratch letters into the wax, showing a lighter colour against the darker wax. These wax tablets could be recycled, in that the tablet could be heated (to approximately 50 °C), allowing the wax to soften and reform a smooth writing surface. The tablets were likely made from wood recycled from barrel staves, and often were made in diptych style, where two tablets were loosely linked and could fold together to close, like a book with only two pages, protecting the soft wax on the inside. Evidence suggests the tablets were made from staves due to the discovery of several staves and glazing objects at the site alongside the tablets. These staves are of the same type of wood (silver fir) as the tablets. However there were two ink leaf tablets inscribed with a pen that were discovered at the same site.
The highest dose of a drug or treatment that does not cause unacceptable side effects. The maximum tolerated dose is determined in clinical trials by testing increasing doses on different groups of people until the highest dose with acceptable side effects is found. Also called MTD. (NCI) Medication
Soybeans suffer from the fungus Pythium spinosum in Arkansas and Indiana (United States), and China. In Japan and the United States, the Soybean dwarf virus (SbDV) causes a disease in soybeans and is transmitted by aphids.
amount of substance Also enplethy, chemical amount, or simply amount. The number of discrete particles (such as molecules, atoms, ions, electrons, or any other atomic-scale entity) in a given sample of matter, divided by the Avogadro constant. The SI unit for amount of substance is the mole (mol).
Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the N-terminus (beginning), of proteins or peptides. They are found in many organisms; in the cell, they are found in many organelles, in the cytosol (internal cellular fluid), and as membrane proteins. Aminopeptidases are used in essential cellular functions, and are often zinc metalloenzymes, containing a zinc cofactor. Aminopeptidases occur in both water-soluble and membrane-bound forms and can be found both in various cellular compartments and in the extracellular environment (outside of cells). Their broad substrate specificity, their ability to strongly bind to their targets, allows them to remove beginning N-terminal amino acids from almost all unsubstituted oligopeptides. For instance, Aminopeptidase N (AP-N) is particularly abundant in the brush border membranes of the kidney, the small intestine, and the placenta, and is also found in the liver. AP-N is involved in the final digestion of peptides generated from the hydrolysis (cleaving) of proteins by gastric and pancreatic proteases. Some aminopeptidases are monomeric, and others are found as assemblies of relatively high mass (50 kDa) subunits. cDNA sequences are available for several aminopeptidases and a crystal structure of the open state of human endoplasmic reticulum aminopeptidase 1 is available.
Sources: en.wikipedia.org
== Accords == On February 19, 2015, representatives from the Malian government and the Coordination of Azawad Movements (CMA) agreed upon a new document, including the cessation of hostilities, as negotiations to end the broader war continued in Algiers. On March 1, a mediation agreement was proposed by Algeria, which was accepted by Mali and pro-government militias. The CMA asked for some time to consider the agreement, as there were no propositions for autonomy or federalism for northern Mali, which angered a large portion of Tuareg rebels. The CMA announced their refusal to sign the agreement on April 10. On April 27, the pro-government GATIA and Arab Movement of Azawad (MAA) captured Menaka, initiating new clashes between Tuareg rebels and the pro-government militias. On May 10, the CMA initialized the agreement, but did not sign the text. The peace agreement was signed on May 15 in Bamako by the Malian government, representatives of pro-government militias, and representatives from Algeria, Burkina Faso, Mauritania, Niger, Nigeria, Chad, the African Union, the United Nations, ECOWAS, the Organisation of Islamic Cooperation, the European Union, and France. No CMA representatives were present for the signing on May 15. That same day, fighting broke out near Menaka. Under pressure from international organizations, the CMA finally signed the agreement in Bamako on June 20. The CMA's representative was Sidi Brahim Ould Sidati, a leader of the MAA.
=== Individual protein immunoprecipitation (IP) === Involves using an antibody that is specific for a known protein to isolate that particular protein out of a solution containing many different proteins. These solutions will often be in the form of a crude lysate of a plant or animal tissue. Other sample types could be body fluids or other samples of biological origin.
Ethanol does induce non-lamellar phases (non-bilayer) but this process is concentration-dependent. On average the bilayers is preserved at approximately less than 10 mol%. Ethanol prefers to bond in the hydrophilic region near phosphate groups which could be contributed to its amphiphilic character. The effects of ethanol can be reversed or hindered in the presence of cholesterol (sterol compounds) It may be necessary to perform a future study to compare the maximum amount of cholesterol (30 mol%) obtained in the NNR study to varied concentrations of ethanol as depicted in the AMDS study to see if ethanol is still hindered in the presence of sterol compounds.
This is a list of published International Organization for Standardization (ISO) standards and other deliverables. For a complete and up-to-date list of all the ISO standards, see the ISO catalogue. The standards are protected by copyright and most of them must be purchased. However, about 300 of the standards produced by ISO and IEC's Joint Technical Committee 1 (JTC 1) have been made freely and publicly available.
Straight-chain alkanes are sometimes indicated by the prefix n- (for "normal") where a non-linear isomer exists. Although this is not strictly necessary and is not part of the IUPAC naming system, the usage is still common in cases where one wishes to emphasize or distinguish between the straight-chain and branched-chain isomers, e.g., "n-butane" rather than simply "butane" to differentiate it from isobutane. Alternative names for this group used in the petroleum industry are linear paraffins or n-paraffins. The first eight members of the series (in terms of number of carbon atoms) are named as follows:
Sources: en.wikipedia.org
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
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.