Everything below concerns actin binding. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-04-29. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
In June 2013, two biosimilar versions (Inflectra and Remsima) were submitted for approval in the European Union, by Hospira and Celltrion Healthcare respectively. Both had a positive opinion from European Medicines Agency's (EMA) Committee for Medicinal Products for Human Use (CHMP) for sale in the European Union (EU). Celltrion obtained marketing authorization approval (MAA) from 27 EU countries and 3 EEA (European Economic Area) countries by September 2013. Inflectra was approved for use in the European Union in September 2013, and Remsima was approved for use in the European Union in October 2013. In Japan, Celltrion received marketing authorization for Remsima from Japan's Ministry of Health, Labour and Welfare (MHLW) in July 2014. In India, Epirus Biopharmaceuticals obtained approval to produce biosimilar infliximab under the brand name "Infimab" (trail name BOW015). The US Food and Drug Administration (FDA) approved Celltrion/Hospira/Pfizer's Inflectra (infliximab-dyyb) in April 2016. The FDA approved Samsung Bioepis Co., Ltd.'s Renflexis (infliximab-abda) in April 2017. Biogen released another biosimilar, Flixabi, which was approved in Germany, the UK, and the Netherlands. Flixabi was approved for use in the European Union in May 2016. In December 2017, Ixifi (infliximab-qbtx) was approved in the United States. Zessly was approved for use in the European Union in May 2018. In December 2019, Avsola (infliximab-axxq) was approved in the United States. Avsola was approved for medical use in Canada in March 2020.
== Leucine starvation == Starvation induces the lysosomal retention of leucine such that it requires RAG-GTPases and the lysosomal protein complex regulator. PCAF is recruited specifically to the CHOP amino acid response element to enhance the ATF4 transcriptional activity.
As agreed at the Potsdam Conference, 200,000 troops of the Chinese 1st Army occupied northern Indochina to the 16th parallel, while the British under the South-East Asia Command of Lord Mountbatten occupied the south. The Chinese troops had been sent by Chiang Kai-shek under General Lu Han to accept the surrender of Japanese forces occupying that area, then to supervise the disarming and repatriation of the Japanese Army. In the North, the Chinese permitted the DRV government to remain in charge of local administration and food supply. Initially, the Chinese kept the French Colonial soldiers interned, with the acquiescence of the Americans. The Chinese used the VNQDĐ, the Vietnamese branch of the Chinese Kuomintang, to increase their influence in Indochina and put pressure on their opponents. Chiang Kai-shek deliberately withheld his best soldiers from Vietnam, holding them in reserve for the fight against the Communists inside China, and instead sent undisciplined warlord troops from Yunnan under Lu Han to occupy Vietnam north of the 16th parallel and accept the Japanese surrender. In total, 200,000 of General Lu Han's Chinese soldiers occupied north Vietnam starting August 1945. 90,000 arrived by October, the 62nd army came on 26 September to Nam Dinh and Haiphong, later arriving at Lang Son and Cao Bang and the Red River region and Lai Cai were occupied by a column from Yunnan. Vietnamese VNQDD fighters accompanied the Chinese soldiers. Lu Han occupied the French governor general's palace after ejecting the French staff under Sainteny.
== Personal life == Kahn is married to Susan Becker Kahn, also formerly of Louisville. They have two children. Stacy Anne Kahn is a pediatric gastroenterologist at the Boston Children's Hospital. Jeffrey Adam Kahn is managing partner of Continuum Search based in Denver, Colorado. His brother Arnold Kahn was emeritus professor of developmental biology of the University of California San Francisco.
=== Specific activity === The specific activity of an enzyme is another common unit. This is the activity of an enzyme per milligram of total protein (expressed in μmol min−1 mg−1). Specific activity gives a measurement of enzyme purity in the mixture. It is the micro moles of product formed by an enzyme in a given amount of time (minutes) under given conditions per milligram of total proteins. Specific activity is equal to the rate of reaction multiplied by the volume of reaction divided by the mass of total protein. The SI unit is katal/kg, but a more practical unit is μmol/(mg*min). Specific activity is a measure of enzyme processivity (the capability of enzyme to be processed), at a specific (usually saturating) substrate concentration, and is usually constant for a pure enzyme. An active site titration process can be done for the elimination of errors arising from differences in cultivation batches and/or misfolded enzyme and similar issues. This is a measure of the amount of active enzyme, calculated by e.g. titrating the amount of active sites present by employing an irreversible inhibitor. The specific activity should then be expressed as μmol min−1 mg−1 active enzyme. If the molecular weight of the enzyme is known, the turnover number, or μmol product per second per μmol of active enzyme, can be calculated from the specific activity. The turnover number can be visualized as the number of times each enzyme molecule carries out its catalytic cycle per second.
Sources: en.wikipedia.org
== See also == Body image Eating recovery Evolutionary psychiatry Idée fixe Inedia List of people with anorexia nervosa List of deaths from anorexia nervosa National Association of Anorexia Nervosa and Associated Disorders Muscle dysmorphia Orthorexia nervosa Pro-ana
== Career == He joined the Ethiopian Ministry of Foreign Affairs in 1978, serving as Ethiopia/EEC Relations Desk Officer. In 1983 he was mandated to the Diplomatic Mission in Brussels, with the title of economist. Berhanu participated in negotiations leading to the 1981 and 1985 extensions of the Lomé Convention – an agreement concerning international aid and trade between the African, Caribbean and Pacific countries and the European Union – as well as participating in the committees that managed this convention. In 1992 Berhanu returned to Addis Ababa to lead the Western European Division at the Ministry at the rank of Counselor, before taking on the role of Acting Director General for International Organisation and Economic Cooperation in 1993. Later that year he was promoted to Director General, and it was in this role that he represented Ethiopia at all of the Organisation of African Unity Council and Summit conferences held between 1992 and 2000, as well as the Economic Commission for Africa Ministerial Conferences held in this period, chaired the Economic and Social Council meeting of the African Economic Community in June 1998, and served as deputy leader of the Ethiopian delegation to the United Nations from 1993 to 2000. On 7 December 2000, he was appointed the Ethiopian ambassador to Russia. In February 2002, he was appointed Ambassador of Ethiopia to Sweden and concurrently Norway, Denmark, Finland and Iceland. In March 2006 he was appointed as Ambassador of Ethiopia to the United Kingdom, a position he held during 10 years. In 2016, H.E.
Cdc25 phosphatase catalytic domain non-catalytic domains of eukaryotic dual-specificity MAPK-phosphatases non-catalytic domains of yeast PTP-type MAPK-phosphatases non-catalytic domains of yeast Ubp4, Ubp5, Ubp7 non-catalytic domains of mammalian Ubp-Y Drosophila heat shock protein HSP-67BB several bacterial cold-shock and phage shock proteins plant senescence associated proteins catalytic and non-catalytic domains of rhodanese Rhodanese has an internal duplication. This domain is found as a single copy in other proteins, including phosphatases and ubiquitin C-terminal hydrolases. While cyanide is the most well-characterized sulfur acceptor from rhodanese, biological thiols such as glutathione are capable of acting as acceptors to form free low-molecular weight hydropersulfides such as glutathione hydropersulfide.
Ribosomal RNA (rRNA) is the catalytic component of the ribosomes. The rRNA is the component of the ribosome that hosts translation. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA. Three of the rRNA molecules are synthesized in the nucleolus, and one is synthesized elsewhere. In the cytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis. Several ribosomes may be attached to a single mRNA at any time. Nearly all the RNA found in a typical eukaryotic cell is rRNA. Transfer-messenger RNA (tmRNA) is found in many bacteria and plastids. It tags proteins encoded by mRNAs that lack stop codons for degradation and prevents the ribosome from stalling.
During his first year in the House, Sanders often alienated allies and colleagues with his criticism of both political parties as working primarily on behalf of the wealthy. In 1991, he co-founded the Congressional Progressive Caucus, a group of mostly liberal Democrats that he chaired for its first eight years, while still refusing to join the Democratic Party or caucus. In 2005, Rolling Stone called Sanders the "amendment king" for his ability to get more roll call amendments passed than any other congressman during the period since 1995, when Congress was entirely under Republican control. Being an independent allowed him to form coalitions across party lines.
Sources: en.wikipedia.org
Two-dimensional SDS-PAGE uses the principles and techniques outlined above. 2-D SDS-PAGE, as the name suggests, involves the migration of polypeptides in 2 dimensions. For example, in the first dimension, polypeptides are separated according to isoelectric point, while in the second dimension, polypeptides are separated according to their molecular weight. The isoelectric point of a given protein is determined by the relative number of positively (e.g. lysine, arginine) and negatively (e.g. glutamate, aspartate) charged amino acids, with negatively charged amino acids contributing to a low isoelectric point and positively charged amino acids contributing to a high isoelectric point. Samples could also be separated first under nonreducing conditions using SDS-PAGE, and under reducing conditions in the second dimension, which breaks apart disulfide bonds that hold subunits together. SDS-PAGE might also be coupled with urea-PAGE for a 2-dimensional gel. In principle, this method allows for the separation of all cellular proteins on a single large gel. A major advantage of this method is that it often distinguishes between different isoforms of a particular protein – e.g. a protein that has been phosphorylated (by addition of a negatively charged group). Proteins that have been separated can be cut out of the gel and then analysed by mass spectrometry, which identifies their molecular weight.
=== Molecular Weight === Since the molecular weight (or extent of polymerization) of a solute will correspond to a specific refractive index increment, the relationship between increasing solute weight and refractive index increment can be plotted to determine the exact molecular weight of an unknown solute.
Bacterial vaginosis is a condition of the vaginal microbiota in which an excessive growth of Gardnerella vaginalis and other mostly anaerobic bacteria displace the beneficial Lactobacilli species that maintain healthy vaginal microbial populations. Bacterial meningitis is a bacterial inflammation of the meninges, which are the protective membranes covering the brain and spinal cord. Bacterial pneumonia is a bacterial infection of the lungs. Urinary tract infection is predominantly caused by bacteria. Symptoms include the strong and frequent sensation or urge to urinate, pain during urination, and urine that is cloudy. The most frequent cause is Escherichia coli. Urine is typically sterile but contains a variety of salts and waste products. Bacteria can ascend into the bladder or kidney and causing cystitis and nephritis. Bacterial gastroenteritis is caused by enteric, pathogenic bacteria. These pathogenic species are usually distinct from the usually harmless bacteria of the normal gut flora. But a different strain of the same species may be pathogenic. The distinction is sometimes difficult as in the case of Escherichia. Bacterial skin infections include: Impetigo is a highly contagious bacterial skin infection commonly seen in children. It is caused by Staphylococcus aureus, and Streptococcus pyogenes. Erysipelas is an acute streptococcus bacterial infection of the deeper skin layers that spreads via with lymphatic system. Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin.
==== Social services and Social Security ==== Following Republican efforts to pass the Medicare Act of 2003, Bush signed the bill, which included major changes to the Medicare program by providing beneficiaries with some assistance in paying for prescription drugs, while relying on private insurance for the delivery of benefits. The retired persons lobby group AARP worked with the Bush Administration on the program and gave its endorsement. Bush said the law, estimated to cost $400 billion over the first ten years, would give the elderly "better choices and more control over their health care". Bush began his second term by outlining a major initiative to reform Social Security, which was facing record deficit projections beginning in 2005. Bush made it the centerpiece of his domestic agenda despite opposition from some in the U.S. Congress. In his 2005 State of the Union Address, Bush discussed the potential impending bankruptcy of the program and outlined his new program, which included partial privatization of the system, personal Social Security accounts, and options to permit Americans to divert a portion of their Social Security tax (FICA) into secured investments. Democrats opposed the proposal to partially privatize the system. Bush embarked on a 60-day national tour, campaigning for his initiative in media events known as "Conversations on Social Security" in an attempt to gain public support.
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.