The short version of synthetic peptide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-07-12 and is reviewed periodically as new material appears.
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.
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.
| 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 |
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
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.
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.
There is currently no use for any isotope of berkelium outside basic scientific research. Berkelium-249 is a common target nuclide to prepare still heavier transuranium elements and superheavy elements, such as lawrencium, rutherfordium and bohrium. It is also useful as a source of the isotope californium-249, which is used for studies on the chemistry of californium in preference to the more radioactive californium-252 that is produced in neutron bombardment facilities such as the HFIR. A 22 milligram batch of berkelium-249 was prepared in a 250-day irradiation and then purified for 90 days at Oak Ridge in 2009. This target yielded the first 6 atoms of tennessine at the Joint Institute for Nuclear Research (JINR), Dubna, Russia, after bombarding it with calcium ions in the U400 cyclotron for 150 days. This synthesis was a culmination of the Russia-US collaboration between JINR and Lawrence Livermore National Laboratory on the synthesis of elements 113 to 118 which was initiated in 1989.
== Collaboration == Tecemotide was developed – until Clinical trial phase II – by the Canadian biotech company Biomira Inc., which changed its company name to Oncothyreon Inc. in 2007. Oncothyreon is now located in Seattle, Washington, and it changed its name to SGEN after a merger and acquisition in March 2018. In 2001, Merck KGaA, of Darmstadt, Germany, entered into a collaboration and supply agreement with Biomira. In 2007, Merck KGaA acquired the exclusive worldwide marketing rights from Biomira, and Merck KGaA has since then been entirely responsible for the further clinical development of tecemotide. In 2008, Merck KGaA acquired the manufacturing rights for tecemotide from Oncothyreon. In 2011, Ono Pharmaceutical Company, of Japan, acquired a co-development and co-marketing license for tecemotide in Japan; Ono paid Merck KGaA 5 million euros.
A given stereocenter has two possible configurations (R and S), which give rise to stereoisomers (diastereomers and enantiomers) in molecules with one or more stereocenter. For a chiral molecule with one or more stereocenter, the enantiomer corresponds to the stereoisomer in which every stereocenter has the opposite configuration. An organic compound with only one stereogenic carbon is always chiral. On the other hand, an organic compound with multiple stereogenic carbons is typically, but not always, chiral. In particular, if the stereocenters are configured in such a way that the molecule can take a conformation having a plane of symmetry or an inversion point, then the molecule is achiral and is known as a meso compound. Molecules with chirality arising from one or more stereocenters are classified as possessing central chirality. There are two other types of stereogenic elements that can give rise to chirality, a stereogenic axis (axial chirality) and a stereogenic plane (planar chirality). Finally, the inherent curvature of a molecule can also give rise to chirality (inherent chirality). These types of chirality are far less common than central chirality. BINOL is a typical example of an axially chiral molecule, while trans-cyclooctene is a commonly cited example of a planar chiral molecule. Finally, helicene possesses helical chirality, which is one type of inherent chirality. Chirality is an important concept for stereochemistry and biochemistry.
The Cape, more specifically the small area around present day Cape Town, was the first part of South Africa to be settled by Europeans. The Dutch East India Company (Vereenigde Oost-Indische Compagnie, VOC) officials did not favour the permanent settlement of Europeans in their trading empire, although during the 140 years of Dutch rule many VOC servants retired or were discharged and remained as private citizens. A small number of longtime VOC employees, however, expressed interest in applying for grants of land with the objective of retiring at the Cape as farmers. In time, they came to form a class of former VOC employees, vrijlieden, also known as vrijburgers (free citizens) who stayed in Dutch territories overseas after serving their contracts. Over generations, this settled European population came to form a distinct identity as Afrikaners (formerly sometimes Afrikaander or Afrikaaner, from the Dutch Africaander) or Boers (farmers). In 1806, the Cape was colonised by the British Empire. Initially British control was aimed to protect the trade route to the East from Napoleon, however, the British soon realised the potential to develop the Cape colony further. Antipathy towards British control and the introduction of new systems and institutions grew amongst a substantial portion of the Afrikaner/Boer community. Between 1834 and 1840 about 15 000 Boers left the Cape Colony in parties of ox-wagons, in search of sovereignty beyond British-claimed territories.
Sources: en.wikipedia.org
Phthalates have been banned from use in feeding bottles in the EU. In the US, there have been repeated calls for the removal of phthalates by the U.S. Consumer Product Safety Commission (CPSC) and others. Their use in children's toys and products was somewhat restricted by the Consumer Product Safety Improvement Act of 2008. Plastics labeled #3 may leach phthalates. Latex rubber nipples may contain phthalates, so silicone nipples may be recommended instead. Packaging may indicate whether a product is "BPA-free" or "phthalate-free". Plastics may degrade over time in other ways, There are concerns that small beads of plastic may be released into fluids from some types of plastic bottles. In 2020 researchers reported that infant feeding bottles made out of polypropylene caused microplastics exposure to infants ranging from 14,600 to 4,550,000 particles per capita per day in 48 regions with contemporary preparation procedures. Microplastics release is higher with warmer liquids and similar with other polypropylene products such as lunchboxes. In 2022, the first study to examine the presence of plastic polymers in human blood found plastics of multiple types in the blood samples of 17 out of 22 healthy adults tested (nearly 80%). Medical experts have suggested reducing exposure to microplastics by not shaking plastic bottles or exposing them to high temperatures. Some recommend using alternative materials such as glass, silicone, or stainless steel.
A regular working electrode has a radius within an order of magnitude of 1 mm. Having a controlled surface area with a well-defined shape is necessary for being able to interpret cyclic voltammetry results. To run cyclic voltammetry experiments at very high scan rates a regular working electrode is insufficient. High scan rates create peaks with large currents and increased resistances, which result in distortions. Ultramicroelectrodes can be used to minimize the current and resistance. The counter electrode, also known as the auxiliary or second electrode, can be any material that conducts current easily, will not react with the bulk solution, and has a surface area much larger than the working electrode. Common choices are platinum and graphite. Reactions occurring at the counter electrode surface are unimportant as long as it continues to conduct current well. To maintain the observed current the counter electrode will often oxidize or reduce the solvent or bulk electrolyte.
Knoxville's Greek community is perhaps best known for its restaurateurs, namely the Regas family, who operated a restaurant on North Gay Street from 1919 to 2010, and the Paskalis family, who founded the Gold Sun Cafe on Market Square around 1909. Notable members of Knoxville's Jewish community included jeweler Max Friedman and department store owner Max Arnstein. One of Knoxville's largest migrant groups consisted of rural people who moved to the city from the surrounding rural counties, often seeking wage-paying jobs in mills. Many of Knoxville's political and business leaders throughout the 20th century hailed from rural areas of Southern Appalachia.
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 trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.