The short version of actin binding fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-20. Anything still debated is marked as such rather than presented as settled.
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.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilized powder | Typical form for short synthetic peptides |
| Solubility class | Freely soluble in water and aqueous buffer | Dissolution aided by gentle mixing, not vigorous shaking |
| Typical storage temperature | −20 °C, desiccated | −80 °C used for long-term holding |
| Common analytical method | Reverse-phase HPLC with UV detection near 214 nm | Identity confirmed separately by mass spectrometry |
| Common synonyms | Thymosin beta-4 fragment; TB4 fragment | Naming varies between suppliers and publications |
TB-500 is a synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
Regulatory status differs by country, but TB-500 is not an approved pharmaceutical in major jurisdictions. It is commonly sold as a research chemical for laboratory use, which places responsibility for identity and purity on the supplier and the laboratory. Published human data are limited, and most reports involve preclinical models or cell culture. Questions about whether the fragment mimics all actions of thymosin beta-4, and under which conditions, remain open. Independent verification of any material is therefore a practical requirement in research settings.
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.
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.
=== Foods === Sucrose esters are used as food additives in a variety of food. European Parliament and Council Directive No 95/2/EC limited the use of sucrose esters under E 473 in each kind of food. No longer in force, Date of end of validity: 20/01/2010; Repealed by 32008R1333 .
== Subsidiaries == Following declining earnings in 1965, HVEC reorganized into profit centers and established three wholly owned subsidiaries to diversify beyond particle accelerators. After U.S. orders for new accelerators ceased in the early 1970s, HVEC transformed into a miniconglomerate with more than ten subsidiaries, and industrial products from these units accounted for 80 percent of company revenues by 1972.
== Overdose == Excessive doses of metoprolol can cause bradycardia, hypotension, metabolic acidosis, seizures, and cardiorespiratory arrest. Blood or plasma concentrations may be measured to confirm a diagnosis of overdose or poisoning in hospitalized patients or to assist in a medicolegal death investigation. Plasma levels are usually less than 200 μg/L during therapeutic administration, but can range from 1–20 mg/L in overdose victims.
== Commercial and clinical products == The clearest commercial example is the SERI Surgical Scaffold, a knitted mesh of highly purified silk fibroin that originated in research at Tufts University and was first marketed by Serica Technologies. The U.S. Food and Drug Administration cleared it in 2009 as a temporary scaffold for the support and reinforcement of soft tissue; the product was subsequently held by Allergan and then by Sofregen Medical. After implantation the mesh provides immediate mechanical support and is gradually resorbed and replaced by the patient's own collagen. Silk sutures remain in widespread clinical use, and other silk-based products and devices are in development or early clinical testing.
Sources: en.wikipedia.org
=== Plants === In green plants, oxygen is a byproduct generated during photosynthesis, and exits through stomata, root cell walls, and other routes. Other materials that are exuded by some plants — resin, saps, latex, are forced from the interior of the plant by hydrostatic pressures inside the plant and by absorptive forces of plant cells. These latter processes do not require added energy, as they act passively. During the pre-abscission phase, deciduous plants excrete by leaf-fall.
In Australia, two distinctly different coloured sodas exist, red and brown, both usually called creaming soda, although some brands such as Bickford's, use the term creamy soda. Almost all varieties are predominantly vanilla based, but red or pink varieties introduce raspberry flavoring. Another local variant produced by Golden Circle is vanilla and fruit-flavored, and coloured yellow to distinguish it from existing brands. More traditional brown varieties are also available, but less common. Brands include Kirks' Sno Drop (only available in South Australia, Victoria, and the Northern Territory), Tarax, River Port, Hartz, Saxby's, Bert's Snowette (the original recipe of Shelley's Snowcap (Snowcap Champagne) before the line was acquired) and Schweppes, which also produce a red variety as part of its "Traditionals" range. Bundaberg Burgundee creaming soda is based on red grapes and is alternately made by other producers under the name portello. The term "creaming soda" is used to refer to the drink itself, whereas the combination of soda and ice-cream is called a spider.
=== Glycoproteins === Glycoproteins are conjugated proteins that consist of one or more carbohydrate groups bound to the polypeptide chain. Glycoproteins are generally the biggest groups of conjugated proteins. These carbohydrates are generally shorter polymers of monosaccharide that are covalently bonded. Glycoproteins can be found all around and in living organisms. They range from glycoproteins in cell surface membranes that constitute the glycocalyx, to important antibodies produced by leukocytes. The main function of glycoproteins is cell recognition and communication. They act as receptors and help cells interact with their environment by responding to different signals. In the immune system, glycoproteins work as antibodies to help the body recognize and destroy foreign organisms like bacteria and viruses. Glycoproteins also have other uses like Adhesion procedure, hormone activity, and protein stability.
Sources: en.wikipedia.org
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.
Not necessarily. Some vendors use the name for the full 43-residue protein, while others apply it to a short actin-binding fragment or to a related tetrapeptide. The sequence should be confirmed from documentation rather than assumed from the label.
No thymosin beta-4 fragment holds marketing approval as a medicine in major jurisdictions. Material offered for sale is typically labelled for laboratory research only.
No. Thymosin beta-4 is a 43-residue natural peptide, while TB-500 is a commercial label applied to a short synthetic fragment of it. The two differ in length, sequence coverage and how they are handled in the laboratory.