thymosin beta-4 fragment comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-11-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
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.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
In 1996 Merck paid $1.8 million for polluting the air. New machines were installed to reduce smog emissions by 680,000 lb (310,000 kg) a year. In November 1993, Merck & Co. acquired Medco Containment Services for $6 billion. Merck & Co. spun Medco off ten years later. Merck's supply chain reduction programme has been referred to as an example of successful change. Merck reduced its number of global suppliers from 40,000 to less than 10,000 during the period from 1992 to 1997.
=== Scientific era === In 1500 polymath Leonardo da Vinci provided the first illustration of the thyroid. In 1543 anatomist Andreas Vesalius gave the first anatomic description and illustration of the gland. In 1656 the thyroid received its modern name, by the anatomist Thomas Wharton. The gland was named thyroid, meaning shield, as its shape resembled the shields commonly used in Ancient Greece. The English name thyroid gland is derived from the medical Latin used by Wharton – glandula thyreoidea. Glandula means 'gland' in Latin, and thyreoidea can be traced back to the Ancient Greek word θυρεοειδής, meaning 'shield-like/shield-shaped'. French chemist Bernard Courtois discovered iodine in 1811, and in 1896 Eugen Baumann documented it as the central ingredient in the thyroid gland. He did this by boiling the thyroid glands of a thousand sheep, and named the precipitate, a combination of the thyroid hormones, 'iodothyrin'. David Marine in 1907 proved that iodine is necessary for thyroid function. Graves' disease was described by Robert James Graves in 1834. The role of the thyroid gland in metabolism was demonstrated in 1895 by Adolf Magnus-Levy. Thyroxine was first isolated in 1914 and synthesized in 1927, and triiodothyroxine in 1952. The conversion of T4 to T3 was discovered in 1970. The process of discovering TSH took place over the early to mid twentieth century. TRH was discovered by Polish endocrinologist Andrew Schally in 1970, contributing in part to his Nobel Prize in Medicine in 1977.
The (Princely) County of Tyrol was an estate of the Holy Roman Empire established about 1140. After 1253, it was ruled by the House of Gorizia and from 1363 by the House of Habsburg. In 1804, the County of Tyrol, unified with the secularised prince-bishoprics of Trent and Brixen, became a crown land of the Austrian Empire, then was part of Bavaria from 1805 to 1814 when it returned to Austrian rule. From 1867, it was a Cisleithanian crown land of Austria-Hungary. Today the territory of the historic crown land is divided between the Italian autonomous region of Trentino-Alto Adige/Südtirol and the Austrian state of Tyrol. The two parts are today associated again in the Tyrol–South Tyrol–Trentino Euroregion.
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== Hormones == FGF21, a protein hormone that induces mitochondrial oxidation of fatty acids, hepatic gluconeogenesis, and ketogenesis in response to fasting. Hepcidin, a peptide hormone that regulates iron homeostasis. Insulin-like growth factor 1, a polypeptide protein hormone which plays an important role in childhood growth and continues to have anabolic effects in adults Thrombopoietin, a glycoprotein hormone that regulates the production of platelets by the bone marrow
== Research == Wu's research has focused on cardiac biomarkers, clinical toxicology, point-of-care diagnostics, and pharmacogenomics. He has published over 550 peer-reviewed papers and co-authored multiple book chapters and clinical textbooks. In the area of cardiac markers, he and his research group were among the first to evaluate the clinical value of cardiac troponin and the natriuretic peptides that are in widespread clinical use today. He has been active on committees to standardize testing and has participated in the creation and authorship of clinical practice guidelines for cardiac markers. More recently, he has conducted research on biomarkers for traumatic brain injury and contributed a textbook on this topic. His group was among the first clinical labs to initiate untargeted identifications using exact molecular formula. During the COVID-19 pandemic, Wu suspended his normal research work to conduct laboratory-based studies on SARS-CoV-2 molecular, antigen and antibody testing. In addition to his scientific publications, Wu is the author of eight books of short stories designed to raise public awareness of laboratory medicine. His stories are based on real cases, where the and aim to depict the behind-the-scenes role of lab professionals in patient care. He has also launched a social media campaign to educate the general public as to the value of the clinical laboratory. His advocacy stresses that clinical labs are essential in both diagnosis and long-term health management, especially in emergency settings and public health crises.
Pakistan cricket spot-fixing scandal – in 2010, three Pakistan players—team captain Salman Butt, Mohammad Asif and Mohammad Amir—were accused of involvement in a spot-fixing scheme in which they allegedly accepted large sums of money to influence specific events within a match, as opposed to an actual match result. After an investigation, the ICC banned all three from the sport for periods from 5 to 10 years. Later, Butt and Asif were tried in a London court and found guilty of charges related to the scheme, whilst Amir pleaded guilty to similar charges in the same court. All received prison sentences ranging from 6 to 30 months. 2013 Indian Premier League spot-fixing and betting case 2018 Australian ball-tampering scandal - In 2018, When Australia toured South Africa, Australia's Cameron Bancroft was seen on camera rubbing the ball with a small yellow object then hid the object in his underwear. The umpires then ruled he was ball tampering. It was then found that Australian captain Steve Smith and vice captain David Warner were also found to have been involved in the incident. Smith and Warner were then banned for 12 months from international and domestic cricket while Bancroft was banned for 9 months. Smith was also temporarily banned from captaining Australia while Warner received a life ban from captaining. 2018 Sri Lankan cricket pitch fixing and betting scandal
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No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
Sealed, desiccated and protected from light, at -20 °C or lower for long-term storage. Short-term storage at refrigerator temperature is common in working laboratories.