This is a working overview of actin binding, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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 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.
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 formula | C38H68N10O14 | Calculated for the acetylated heptapeptide |
| Molecular weight | ~889 Da | Monoisotopic mass approximately 889.0 Da |
| Amino acid sequence | Ac-LKKTETQ | N-terminal acetylated seven-residue peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Water-soluble | Peptides of this size generally dissolve in aqueous media |
The regulatory position is broadly consistent across major jurisdictions: no thymosin beta-4 fragment is an approved medicine, and laboratory material is commonly labelled as not intended for human consumption. Anti-doping rules in sport list thymosin beta-4 and its fragments among prohibited peptide hormones. Because these products travel through research-chemical channels rather than pharmaceutical supply chains, quality varies considerably between vendors. Independent testing of identity, purity and sterility is the only dependable check, and a certificate of analysis describes one batch rather than a supplier's whole catalogue.
Lyophilized peptide powder is normally held desiccated at −20 °C, with −80 °C used for longer storage periods. Allowing a sealed vial to reach room temperature before opening is standard practice, because condensation forming on cold powder introduces moisture. Once dissolved, solutions are typically kept cold and shielded from light. Repeated freeze-thaw cycles are avoided because they encourage aggregation and gradual loss of material. These conventions are general to synthetic peptides rather than unique to any one sequence.
Purity and identity are separate measurements and are often confused. Reverse-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, reports the share of total peak area belonging to the target compound. Mass spectrometry by electrospray or matrix-assisted laser desorption then checks whether the observed mass matches the expected sequence. Neither measurement alone shows that a vial holds the intended peptide. Peptide content, meaning the fraction of vial mass that is genuine peptide rather than counter-ion, water or residual acid, is reported separately and is frequently lower than the stated purity figure.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
is obtained. Note, however, that all published dissociation constant values refer to the specific ionic medium used in their determination and that different values are obtained with different conditions, as shown for acetic acid in the illustration above. When published constants refer to an ionic strength other than the one required for a particular application, they may be adjusted by means of specific ion theory (SIT) and other theories.
At the end of the twentieth century, the world was at a major crossroads. Throughout the century, more technological advances had been made than in all of preceding history. Computers, the Internet, and other technologies radically altered daily lives. However, several problems faced the world during the Cold War period and the 1990s that followed. First of all, the gap between rich and poor nations continued to widen. Some said that this problem could not be fixed, arguing that there was a set amount of wealth and it could only be shared by so many. Others claimed that powerful nations with large economies were not doing enough to help improve the rapidly evolving economies of the Third World. Developing countries faced many challenges, including the scale of the task to be surmounted, rapidly growing populations, and the need to protect the environment, along with the associated costs. Secondly, disease threatened to destabilize many regions of the world. Viruses such as West Nile and Avian influenza continued to spread quickly and easily. In poor nations, malaria and other diseases affected the majority of the population. Millions were infected with HIV, the virus that causes AIDS, which was becoming an epidemic in southern Africa and around the world. Increased globalization, specifically Americanization, was also occurring. While not necessarily a threat, it was causing anti-Western and anti-American feelings in parts of the world, especially in the Middle East.
=== 5: Electron carriers === The transmembrane electron transfer carriers in the membrane include two-electron carriers, such as the disulfide bond oxidoreductases (DsbB and DsbD in E. coli) as well as one-electron carriers such as NADPH oxidase. Often these redox proteins are not considered transport proteins.
The psi-loop (Ψ-loop) motif consists of two antiparallel strands with one strand in between that is connected to both by hydrogen bonds. There are four possible strand topologies for single Ψ-loops. This motif is rare as the process resulting in its formation seems unlikely to occur during protein folding. The Ψ-loop was first identified in the aspartic protease family. β-sheets are present in all-β, α+β and α/β domains, and in many peptides or small proteins with poorly defined overall architecture. All-β domains may form β-barrels, β-sandwiches, β-prisms, β-propellers, and β-helices.
Tranexamic acid can be used in skincare products as a cosmetic active to reduce the appearance of inflammation and hyperpigmentation. Tranexamic acid is a zwitterion amino acid, and has a low permeability coefficient in the stratum corneum. Tranexamic acid can be combined with penetration enhancers and microneedling to overcome this limitation. Cosmetic uses may also employ lipophilic derivatives of tranexamic acid (ester prodrugs like Cetyl tranexamate mesylate) that are not zwitterionic and thus have improved skin permeability. Allergic to tranexamic acid History of seizures History of venous or arterial thromboembolism or active thromboembolic disease Severe kidney impairment due to accumulation of the medication, dose adjustment is required in mild or moderate kidney impairment
Sources: en.wikipedia.org
Because of the numerous effects claimed by traditional medicine, there has been considerable basic research to investigate the biological properties of the fruit phytochemicals. The composition of the fruits, seeds, roots, and other constituents has been analyzed, and extracts are under study. Constituents include carotenoids, polysaccharides (comprising 30% of the pulp), vitamins, fatty acids, and peptidoglycans. Various polyphenols occur in the fruit, leaves, and root bark. One monograph indicated that consuming goji for three months or longer may improve cardiometabolic risk factors in healthy Chinese adults, although there was only low-quality evidence for such effects. A limited analysis of four studies concluded that healthy Chinese adults who consumed dried goji berries, juice or capsules for 4-16 weeks had slightly lower blood triglyceride levels and higher HDL cholesterol levels.
In 1976, Guillaume played Nathan Detroit in the Broadway revival of Guys and Dolls and was nominated for a Tony Award. In 1990, Guillaume was cast in the Los Angeles production of The Phantom of the Opera, replacing Michael Crawford in the title role. Guillaume was the first Black actor to portray the character.
27 September Physicists report studies, for the first time, supporting the notion that antimatter particles behave in a similar way as normal matter in a gravitational field. Astronomers report studies suggesting that the rings of Saturn may have resulted from the collision of two moons "a few hundred million years ago". A breakthrough in desalination is achieved by engineers, using a solar-powered device to create freshwater at lower cost than tap water.
Acanthaster planci, starfish (2014) Apostichopus japonicus, sea cucumber (2017) Arbacia lixula, black sea urchin (2024) Astropecten irregularis, sand sea star (2024) Australostichopus mollis, Australian sea cucumber (2016) Chiridota hydrothermica, deep sea cucumber (2024) Diadema setosum, Long-spined sea urchin (2024) Echinometra lucunter, rock boring urchin (2023) Ophionereis fasciata, mottled brittlestar (2016) Patiriella regularis, the New Zealand common cushion star (2016) Plazaster borealis, Octopus starfish (2022) Strongylocentrotus purpuratus, a sea urchin and model deuterostome (2006)
Platelet disorders (thrombocytopenic purpura) Primary thrombocytopenic purpura Secondary thrombocytopenic purpura Post-transfusion purpura Vascular disorders (nonthrombocytopenic purpura) Microvascular injury, as seen in senile (old age) purpura, when blood vessels are more easily damaged Hypertensive states Deficient vascular support Vasculitis, as in the case of Henoch–Schönlein purpura Coagulation disorders Disseminated intravascular coagulation (DIC) Scurvy (vitamin C deficiency) – defect in collagen synthesis due to lack of hydroxylation of procollagen results in weakened capillary walls and cells Meningococcemia Clumping fibrillary protein deposits caused by Amyloidosis Cocaine use with concomitant use of the one-time chemotherapy drug and now veterinary deworming agent levamisole can cause purpura of the ears, face, trunk, or extremities, sometimes needing reconstructive surgery. Levamisole is purportedly a common cutting agent. Decomposition of blood vessels including purpura is a symptom of acute radiation poisoning in excess of 2 Grays of radiation exposure. This is an uncommon cause in general, but is commonly seen in victims of nuclear disaster. Cases of psychogenic purpura are also described in the medical literature, some claimed to be due to "autoerythrocyte sensitization". Other studies suggest the local (cutaneous) activity of tissue plasminogen activator can be increased in psychogenic purpura, leading to substantial amounts of localized plasmin activity, rapid degradation of fibrin clots, and resultant bleeding.
Sources: en.wikipedia.org
== Personal life == Fischer married Agnes Gerlach in 1888. She died seven years later, leaving him a widower with three sons. The younger two died during their military service in World War I, but the oldest, Hermann, became an organic chemist. Fischer died in Berlin on 15 July 1919 at the age of 66. He was Protestant
==== Australia ==== Oxycodone is in Schedule I (derived from the Single Convention on Narcotic Drugs) of the Commonwealth's Narcotic Drugs Act 1967. In addition, it is in Schedule 8 of the Australian Standard for the Uniform Scheduling of Drugs and Poisons ("Poisons Standard"), meaning it is a "controlled drug... which should be available for use but require[s] restriction of manufacture, supply, distribution, possession and use to reduce abuse, misuse and physical or psychological dependence".
It is an attractive target for combinatorial biosynthesis for many reasons: second generation derivatives are currently in the clinic for development; Streptomyces roseosporus, the producer organism of daptomycin, is amenable to genetic manipulation; the daptomycin biosynthetic gene cluster has been cloned, sequenced, and expressed in S. lividans; the lipopeptide biosynthetic machinery has the potential to be interrupted by variations of natural precursors, as well as precursor-directed biosynthesis, gene deletion, genetic exchange, and module exchange; the molecular engineering tools have been developed to facilitate the expression of the three individual NRPS genes from three different sites in the chromosome, using ermEp* for expression of two genes from ectopic loci; other lipopeptide gene clusters, both related and unrelated to daptomycin, have been cloned and sequenced, thus providing genes and modules to allow the generation of hybrid molecules; derivatives can be afforded via chemoenzymatic synthesis; and lastly, efforts in medicinal chemistry are able to further modify these products of molecular engineering. New derivatives of daptomycin (Figure 9) were originally generated by exchanging the third NRPS subunit (dptD) with the terminal subunits from the A54145 (Factor B1) or calcium-dependent antibiotic pathways to create molecules containing Trp13, Ile13, or Val13. dptD is responsible for incorporating the penultimate amino acid, 3-methyl-glutamic acid (3mGlu12), and the last amino acid, Kyn13, into the chain.
21st International Symposium on Chirality STEREOISOMERISM - OPTICAL ISOMERISM Symposium highlights-Session 5: New technologies for small molecule synthesis IUPAC nomenclature for amino acid configurations. Michigan State University's explanation of R/S nomenclature Chirality & Odour Perception at leffingwell.com Chirality & Bioactivity I.: Pharmacology Chirality and the Search for Extraterrestrial Life "The Handedness of the Universe" by Roger A Hegstrom and Dilip K Kondepudi, Scientific American, January 1990
Sources: en.wikipedia.org
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.
No. Thymosin beta-4 is a 43-amino-acid protein, while TB-500 represents only a short N-terminal segment. The two should not be treated as interchangeable in experimental design.
It is often called a thymosin beta-4 fragment, Tβ4 fragment, or Ac-LKKTETQ. The name TB-500 is mainly a commercial or catalog label rather than a formal chemical name.
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.