Everything below concerns thymosin beta-4. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-11-30. Numbers and descriptions here follow the published literature rather than marketing material.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | ≈889 Da for the 7-residue fragment | Full-length thymosin beta-4 is ≈4.9 kDa; catalogs differ |
| Appearance | White to off-white powder | Hygroscopic; weight shifts with residual moisture |
| Solubility class | Freely soluble in water | Also dissolves in aqueous buffers; poorly soluble in nonpolar solvents |
| Typical storage temperature | −20 °C, desiccated, protected from light | Once rehydrated, short-term holding at 2-8 °C |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity by UV absorbance; identity by ESI-MS or MALDI-TOF |
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.
Reconstitution of a lyophilized peptide is normally done with sterile water or a suitable buffer under aseptic conditions. Adding solvent down the vial wall and allowing gentle dissolution instead of vigorous vortexing reduces the chance of aggregation, which can lower the effective concentration of the resulting solution. Concentrated stocks are usually diluted into working buffer shortly before use. Because no standard preparation protocol exists for TB-500 specifically, laboratories adapt general peptide handling practice, and reported results may reflect differing preparation choices.
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.
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.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
=== In Vietnam === The clinical trials of the vaccine in Vietnam are completely sponsored and funded by Vinbiocare, a Vingroup subsidiary. On 2 August, Vinbiocare received regulatory approval to start a clinical trial of its COVID-19 vaccine candidate in Vietnam. The company will coordinate with the Ministry of Health to carry out Phase I-III clinical trials of VBC-COV19-154 vaccine on 21,000 adults in three phases in August 2021. The clinical trial Phase 1 will recruit 100 volunteers to evaluate the safety, tolerability, and initial assessment of immunogenicity of the vaccine. The clinical trial Phase 2 enrolled 300 volunteers at designated medical facilities in multiple provinces, while the third phase of human trials is expected to involve 20,600 volunteers, including phase 3a (600 volunteers) and 3b (20,000 volunteers). Those receiving placebo will receive active vaccine after 6 months, while all participants will be followed up for 1 year. In December 2021, the company plans to complete and submit procedures to the Ministry of Health, applying for an emergency authorization in Vietnam.
This information is saved and analyzed in the last step, data analysis, using bioinformatics software. This compares the sequences to a reference genome to align the fragments and show mutations in the targeted area of the sequence.
===== North America ===== The U.S. National Academy of Medicine (NAM), on behalf of both the U.S. and Canada, sets Dietary Reference Intakes, including Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs), or Adequate Intakes (AIs) for when there is not sufficient information to set EARs and RDAs. For both males and females under 9 years of age, the AIs for potassium are: 400 mg of potassium for 0 to 6-month-old infants, 860 mg of potassium for 7 to 12-month-old infants, 2,000 mg of potassium for 1 to 3-year-old children, and 2,300 mg of potassium for 4 to 8-year-old children. For males 9 years of age and older, the AIs for potassium are: 2,500 mg of potassium for 9 to 13-year-old males, 3,000 mg of potassium for 14 to 18-year-old males, and 3,400 mg for males that are 19 years of age and older. For females 9 years of age and older, the AIs for potassium are: 2,300 mg of potassium for 9 to 18-year-old females, and 2,600 mg of potassium for females that are 19 years of age and older. For pregnant and lactating females, the AIs for potassium are: 2,600 mg of potassium for 14 to 18-year-old pregnant females, 2,900 mg for pregnant females that are 19 years of age and older; furthermore, 2,500 mg of potassium for 14 to 18-year-old lactating females, and 2,800 mg for lactating females that are 19 years of age and older. As for safety, the NAM also sets tolerable upper intake levels (ULs) for vitamins and minerals, but for potassium the evidence was insufficient, so no UL was established. As of 2004, most Americans adults consume less than 3,000 mg.
Spy&Go purification of proteins with either N-terminal, internal or C-terminal SpyTag have all been reported. SpyDock resin is compatible with all SpyTag generations (SpyTag, SpyTag002, SpyTag003) and it does not interfere with the later covalent conjugation of the purified proteins with SpyCatcher.
Sources: en.wikipedia.org
The Cossack homelands were often very fertile, and during the collectivisation campaign many Cossacks shared the fate of the kulaks. According to historian Michael Kort, "During 1919 and 1920, out of a population of approximately 1.5 million Don Cossacks, the Bolshevik regime killed or deported an estimated 300,000 to 500,000". Others, such as Peter Holquist, estimate a figure of 10,000 deaths during this period, while a far greater number died during the engineered Soviet famines of 1932–33 and the Holodomor.
At certain times in the geological past, reef-building organisms similar to corals were very abundant. Like modern corals, these ancient organisms built reefs, some of which ended as great structures in sedimentary rocks. Fossils of fellow reef-dwellers algae, sponges, and the remains of many echinoids, brachiopods, bivalves, gastropods, and trilobites appear along with coral fossils. This makes some corals useful index fossils. Coral fossils are not restricted to reef remnants, and many solitary fossils are found elsewhere, such as Cyclocyathus, which occurs in England's Gault clay formation.
The effect is also apparent in experiments where a polydimethylsiloxane (PDMS) stamp is made with small periodic post structures. The surface with the posts is placed face down on a smooth surface, such that the surface area in between each post is elevated above the smooth surface, like a roof supported by columns. Because of these attractive dispersive forces between the PDMS and the smooth substrate, the elevated surface – or "roof" – collapses down onto the substrate without any external force aside from the van der Waals attraction. Simple smooth polymer surfaces – without any microstructures – are commonly used for these dispersive adhesive properties. Decals and stickers that adhere to glass without using any chemical adhesives are fairly common as toys and decorations and useful as removable labels because they do not rapidly lose their adhesive properties, as do sticky tapes that use adhesive chemical compounds. These forces also act over very small distances – 99% of the work necessary to break van der Waals bonds is done once surfaces are pulled more than a nanometer apart. As a result of this limited motion in both the van der Waals and ionic/covalent bonding situations, practical effectiveness of adhesion due to either or both of these interactions leaves much to be desired. Once a crack is initiated, it propagates easily along the interface because of the brittle nature of the interfacial bonds. As an additional consequence, increasing surface area often does little to enhance the strength of the adhesion in this situation.
Sources: en.wikipedia.org
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.
The name is a commercial label rather than a systematic chemical designation, so different vendors and papers attach it to different sequences. Some treat it as a fragment and others as the whole protein. Comparing two reports therefore requires checking what each one actually analyzed.
Typically it reflects the relative area of the main peak in a reversed-phase chromatogram at a given wavelength. It does not confirm the amino acid sequence, the counter-ion, or the amount of peptide by mass. Identity is normally established by a separate mass measurement.
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.