thymosin beta-4 fragment is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-07-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Thymosin beta-4 is a naturally occurring protein of 43 amino acids found in most mammalian cells, where it binds actin monomers and influences filament dynamics. It was first isolated from thymus tissue in the early 1980s, and its actin-binding activity was later mapped to a short region near the N-terminus. The synthetic fragment sold as TB-500 was designed to reproduce that region rather than the full protein. Whether a short fragment reproduces the behavior of the intact molecule remains an open question, since the parent protein carries additional structural elements outside the binding region.
Published research on the intact protein is substantial, covering actin regulation, cell migration, and wound models. Research using the heptapeptide fragment specifically is far smaller, and much of the circulating material originates in supplier documentation rather than peer-reviewed reports. Where fragment studies do exist, they often employ different sequences, chain lengths, or terminal modifications, which complicates direct comparison across papers. Readers encountering claims about TB-500 should therefore separate evidence about thymosin beta-4 from evidence about the fragment itself.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
| Property | Value | Notes |
|---|---|---|
| Reported sequence | Ac-LKKTETQ | Described in most listings as the actin-binding region of thymosin beta-4 |
| Reported molecular weight | Approximately 889 Da | Value shifts with the stated sequence; compare against the certificate of analysis |
| Parent protein length | 43 amino acids | Thymosin beta-4; the fragment covers only a small part of it |
| Common synonyms | TB4 fragment; thymosin beta-4 fragment | Trade-style names rather than formal nomenclature |
| Formal monographs | Not established | Labeling conventions differ by supplier and region |
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.
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.
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.
Purity is normally assessed by reversed-phase HPLC, with the main peak reported as a percentage of total peak area, while identity is confirmed by mass spectrometry. Electrospray and MALDI-TOF instruments are both used, and the observed mass is compared with the value calculated from the stated sequence. Ion-exchange or size-exclusion methods appear where aggregation or charge variants are of interest. Water content, counter-ion content and residual trifluoroacetate from purification are separate variables that can shift the measured mass and should be weighed when reading a certificate of analysis.
Research peptides are typically supplied as a white to off-white lyophilised powder in a sealed vial. The dry solid is more stable than a solution and is normally kept refrigerated or frozen until use. Dissolution is usually done in water, phosphate-buffered saline or a similar aqueous medium, depending on the assay. Because the material is hygroscopic and easily contaminated, opening vials in a low-humidity environment and recording the lot number before use are standard laboratory practices.
Proposed activity centers on actin sequestration and on the movement of cells during repair processes. In cell culture and animal models, the fragment has been associated with migration, tube formation, and tissue remodeling. These observations are frequently described as preliminary, because most published work uses rodent or in vitro systems rather than controlled human trials. Whether the short fragment reproduces the effects of the full protein remains an open question, and the relationship between dose, route, and measured outcome is not well characterized.
The compound circulates in the literature as a research reagent rather than an approved therapeutic. Regulatory agencies in several countries have not authorized it for medical use, and sporting bodies list related thymosin beta-4 peptides among prohibited substances. Suppliers typically market it with a purity figure and a certificate of analysis, while peer-reviewed clinical reports remain sparse. Discussions therefore often separate laboratory findings from anecdotal reports, and reviewers tend to note the small size and methodological limits of the available studies.
== Plot summary == Anathem is set on the fictional planet of Arbre. Thousands of years before the events in the novel, the planet's intellectuals entered concents (monastic communities) to protect their activities from the collapse of society. The avout (intellectuals separated from Sæcular society) are banned from possessing or operating most advanced technology and are supervised by the Inquisition, which answers to the outside world. The avout are normally allowed to communicate with people outside the walls of the concent only once every year, decade, century, or millennium, depending on the particular vows they have taken. The narrator and protagonist, Fraa Erasmas, is an avout at the Concent of Saunt Edhar. His teacher, Fraa Orolo, discovers that an alien spacecraft is orbiting Arbre – a fact that the world government (Sæcular Power) attempts to cover up. Erasmas becomes aware of Orolo's discovery after Orolo is banished (in a rite called Anathem) from the concent for using a video camera (a forbidden technology) to observe the ship. The presence of the alien ship soon becomes an open secret among many of the avout at Saunt Edhar. The alien ship eventually declares its presence by shining a laser upon several Millenarian Maths (the bastions of those avout who have taken a thousand-year vow of isolation). Shortly after that, the Sæcular Power summons many avout from Saunt Edhar, including Erasmas and a Millenarian named Fraa Jad. The avout are told to travel to the concent of Saunt Tredegarh to attend a Convox (a joint conference of the avout and the Sæcular Power).
== Awards and honours == Uhlmann was elected a Fellow of the Royal Society (FRS) in 2015. His certificate of election reads: Frank Uhlmann's discovery with Nasmyth of 'separase', the protease that cleaves the cohesive links between sister chromatids to trigger anaphase is a key contribution to our understanding of the cell cycle. He has made major contributions to our understanding of the mechanisms of sister chromatid cohesion, and their relationship to cell cycle regulation. He generated the first chromosome-wide high resolution maps of proteins involved in chromosome packaging and segregation. He showed that yeast cohesins accumulate at sites of converging transcription distinct from the sites where their loading factors bind, apparently reflecting interaction with the transcription apparatus; and that cohesin loading factors are recruited to specific chromosomal sites through interaction with the nucleosome remodelling complex Rsc. He has identified genes required for cohesion establishment, and shown that one of these, EcoI, acetylates cohesin during DNA replication, thereby locking it onto DNA and his studies of the link between cohesion regulation and the cell cycle have shown that as well as cleaving cohesin, separase promotes mitotic exit by activating the Cdc14 phosphatase in a protease-independent manner. In 2006, Uhlmann was also elected a member of the European Molecular Biology Organization (EMBO) and awarded the EMBO Gold Medal.
People who inherit one copy of the HbE gene and one copy of the normal β-globin gene (HbA) are said to "carry the HbE trait", and are asymptomatic, as are most people who inherit two copies of HbE. However, inheritance of one HbE copy and one copy of HBB with a different mutation, such as one that causes β-thalassemia or sickle cell anemia, leads to a thalassemia ranging from mild to severe depending on the nature of the second mutation. Minnich was the first person to describe hemoglobin E/β-thalassemia, in 1951. Her work led to further research into this disease, which is estimated to affect a million people worldwide. HbE is considered to be one of the most common genetic mutations, with carrier rates approaching 60% in some parts of Southeast Asia, and testing for HbE is now part of routine neonatal screening and genetic counseling. Pica In 1965, while in Turkey setting up a hematology laboratory at the University of Ankara, Minnich noticed a form of pica involving clay eating. When she followed up this research upon her return to Washington University, she found a similar clay eating practice in parts of the United States. Pica had been known to be associated with iron deficiency but the cause/effect relationship was unclear; Minnich found that that clay actually made iron deficiency worse by acting as a chelating agent, binding iron in the bloodstream and removing it from the body.
=== RNA polymerase is purified === The biochemical purification and characterization of RNA polymerase from the bacterium Escherichia coli (E. coli) enabled the understanding of the mechanisms through which RNA polymerase initiates and terminates transcription, and how those processes are regulated to regulate gene expression (i.e. turning genes on and off). Following the isolation of E. coli RNA polymerase, the three RNA polymerases of the eukaryotic nucleus were identified, as well as those associated with viruses and organelles. Studies of transcription also led to the identification of many protein factors that influence transcription, including repressors, activators and enhancers. The availability of purified preparations of RNA polymerase permitted investigators to develop a wide range of novel methods for studying RNA in the test tube, and led directly to many of the subsequent key discoveries in RNA biology.
Sources: en.wikipedia.org
== Premise == One decade after most members of the Justice Society of America (JSA) are killed in battle against the Injustice Society of America (ISA), Courtney Whitmore, a high school student who moved to Blue Valley, discovers the Cosmic Staff of Starman and learns that her stepfather Pat Dugan used to be his sidekick. After encountering the remnants of the ISA which now include the mysterious Dragon King and his daughter Cindy Burman, Courtney becomes the inspiration for a whole new generation of superheroes and recruits Yolanda Montez, Rick Tyler, and Beth Chapel. In the second season, Stargirl and the JSA contend with the re-emergence of former ISA member Shade and a mysterious entity known as Eclipso, who works with Cindy to create a new ISA called Injustice Unlimited. When Eclipso breaks free from Cindy's control, the JSA works to stop him and finds new allies in Jennie-Lynn Scott, Jakeem Williams, Thunderbolt, a rescued Charles McNider, a revived Starman, and former ISA members Solomon Grundy, Sportsmaster, and Tigress. In the third and final season, the heroes and villains living in Blue Valley become embroiled in a murder mystery after former ISA member Steven Sharpe is found dead, while someone has been spying on them with cameras placed all over town. It turns out that a reconstituted Icicle was responsible as he is in league with the JSA's old enemy Ultra-Humanite and a surviving Dragon King.
Eucalyptus globulus, commonly known as southern blue gum, is a species of flowering plant in the family Myrtaceae. It is a tall, evergreen tree endemic to southeastern Australia. This Eucalyptus species has mostly smooth bark, juvenile leaves that are whitish and waxy on the lower surface, glossy green, lance-shaped adult leaves, glaucous, ribbed flower buds arranged singly or in groups of three or seven in leaf axils, white flowers and woody fruit. There are four subspecies, each with a different distribution across Australia, occurring in New South Wales, Victoria and Tasmania. The subspecies are the Victorian blue gum, Tasmanian blue gum, Maiden's gum, and Victorian eurabbie.
Perchlorate was detected in Martian soil at the level of ~0.6% by weight. It was shown that at the Phoenix landing site it was present as a mixture of 60% Ca(ClO4)2 and 40% Mg(ClO4)2. These salts, formed from perchlorates, act as antifreeze and substantially lower the freezing point of water. Based on the temperature and pressure conditions on present-day Mars at the Phoenix lander site, conditions would allow a perchlorate salt solution to be stable in liquid form for a few hours each day during the summer. The possibility that the perchlorate was a contaminant brought from Earth was eliminated by several lines of evidence. The Phoenix retro-rockets used ultra pure hydrazine and launch propellants consisting of ammonium perchlorate or ammonium nitrate. Sensors on board Phoenix found no traces of ammonium nitrate, and thus the nitrate in the quantities present in all three soil samples is indigenous to the Martian soil. Perchlorate is widespread in Martian soils at concentrations between 0.5 and 1%. At such concentrations, perchlorate could be an important source of oxygen, but it could also become a critical chemical hazard to astronauts. In 2006, a mechanism was proposed for the formation of perchlorates that is particularly relevant to the discovery of perchlorate at the Phoenix lander site. It was shown that soils with high concentrations of chloride converted to perchlorate in the presence of titanium dioxide and sunlight/ultraviolet light. The conversion was reproduced in the lab using chloride-rich soils from Death Valley.
== Safety == Leucine toxicity, as seen in decompensated maple syrup urine disease, causes delirium and neurologic compromise, and can be life-threatening. A high intake of leucine may cause or exacerbate symptoms of pellagra in people with low niacin status because it interferes with the conversion of L-tryptophan to niacin. Leucine at a dose exceeding 500 mg/kg/d was observed with hyperammonemia. As such, unofficially, a tolerable upper intake level (UL) for leucine in healthy adult men can be suggested at 500 mg/kg/d or 35 g/d under acute dietary conditions.
== Modern bioanalytical chemistry == Many scientific endeavors are dependent upon accurate quantification of drugs and endogenous substances in biological samples; the focus of bioanalysis in the pharmaceutical industry is to provide a quantitative measure of the active drug and/or its metabolite(s) for the purpose of pharmacokinetics, toxicokinetics, bioequivalence and exposure–response (pharmacokinetics/pharmacodynamics studies). Bioanalysis also applies to drugs used for illicit purposes, forensic investigations, anti-doping testing in sports, and environmental concerns. Bioanalysis was traditionally thought of in terms of measuring small molecule drugs. However, the past twenty years has seen an increase in biopharmaceuticals (e.g. proteins and peptides), which have been developed to address many of the same diseases as small molecules. These larger biomolecules have presented their own unique challenges to quantification.
Sources: en.wikipedia.org
Most listings describe it as a short acetylated peptide with the sequence Ac-LKKTETQ, presented as a region of thymosin beta-4. The label is a trade-style name rather than a standardized chemical name, so the exact content of a given vial depends on the supplier.
No. Thymosin beta-4 is a protein of 43 amino acids, while TB-500 is described as a short fragment of it. The two differ in size, structure, and the range of interactions each can support.
Naming for research peptides is not centrally coordinated, so vendors set their own labels and specifications. Differences in stated sequence, molecular weight, or purity documentation usually trace back to those independent labeling choices.
Short transit at ambient temperature is generally tolerated, but long-term storage at room temperature is not recommended. Heat, moisture, and light all accelerate degradation. Cold, dry, dark storage is the conventional choice.