Everything below concerns thymosin beta-4 fragment. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
| 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 |
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.
TB-500 refers to a synthetic peptide fragment derived from the actin-binding region of thymosin beta-4, a protein present in most mammalian cells. The full protein contains forty-three amino acids, while the commonly sold fragment is a much shorter acetylated sequence, often cited as LKKTETQ. The fragment retains part of the actin-binding motif but lacks the remainder of the parent protein. Material sold under this name is usually lyophilized powder intended for laboratory research, and it is not a finished pharmaceutical product.
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.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
The hair shaft is majorly composed of hair keratins and their associated proteins (KRTAPs). KRTAPs are products of diverse gene families resulting from gene duplication events in their evolutionary history. These genes are typically small, comprising a single exon less than 1,000 base pairs long. Over the last decade, numerous KRTAP genes have been identified across mammals, including humans. They are categorized into three groups based on their amino acid composition: high sulfur (with <30 mol% cysteine), ultrahigh sulfur (>30 mol% cysteine), and high glycine/tyrosine. Hair keratins form intermediate filaments (KIFs) within trichocytes, specialized cells that contribute to hair formation. As these cells move upward in the cortex, KIFs aggregate, surrounded by a space called the matrix. KRTAPs, also known as KAPs, are a significant part of this matrix between KIFs. It's suggested that KRTAPs play a role in establishing a cross-linked network with KIFs, contributing to the creation of the rigid hair shaft.
== Tumor cells and haptotaxis == A characteristic of many cancers is the ability to move throughout the body. These are malignant cells, and pose a serious threat to the health of an individual. It has been indicated that haptotaxis plays a role in the ability of malignant cells to metastasize. One factor that was initially found to influence haptotaxis is serum spreading factor, which is present in blood serum and interstitial tissues. The presence of serum spreading factor was shown to influence directed migration along a gradient of substrate molecules in a few types of cancer cells. Another component important in the haptotaxis of tumor cells is MenaINV, which is an actin regulatory protein that becomes increasingly expressed in tumor cells. This actin regulatory protein binds to fibronectin receptors and aids in the haptotactic and chemotactic processes of tumor cells.
Vaccinations will begin in March in Scotland, early April in England and Wales, and mid-April in Northern Ireland. RMT staff working for Network Rail call off a strike planned for 16 March after being given a fresh pay offer. 8 March The UK experiences its coldest March night since 2010, with −15.2 °C recorded in Kinbrace, Scotland, dipping even further to −15.4 °C by the morning. The Health Security Agency issues a level 3 cold alert for the whole of England, while more than 100 schools across Wales are closed due to snow. The National Institute for Health and Care Excellence (NICE) approves the use of the weight loss drug semaglutide (marketed as Wegovy) by the NHS in England. 9 March The UK government announces a two-year delay in the construction of the Birmingham to Crewe leg of HS2 in order to save costs. Asda and Morrisons lift their restrictions on the sale of fresh produce. Following a trial at the High Court in Aberdeen, retired research scientist Christopher Harrison, 82, is convicted of the murder of his ex-wife, Brenda Page, in 1978. 10 March The UK economy grew by 0.3% in January 2023, official figures show, much more than the 0.1% that was predicted by economists. The King bestows the title of Duke of Edinburgh on his younger brother, Prince Edward. Prime Minister Rishi Sunak attends a summit in Paris with French president Emmanuel Macron and announces the UK will give France £500m over three years to help the UK stop the influx of migrants arriving by boat.
=== Inhibition of nitrification === Oxidative dissolution of AgNPs, which gives rise to Ag+, potentially inhibits nitrification within Ammonia oxidizing bacteria. A key step in nitrification is the oxidation of ammonia to hydroxylamine (NH2OH) catalyzed by the enzyme ammonia monooxyganase (AMO). The enzymatic activity of AMO is highly vulnerable to interference due to its intracytoplasmic location and its abundance of copper. It is speculated that Ag+ ions from AgNPs interfere with AMO's copper bonds by replacing copper with Ag+ causing a decrease in enzymatic activity, and thus nitrification.
Sources: en.wikipedia.org
=== Construction === Coral reefs in places such as the East African coast are used as a source of building material. Ancient (fossil) coral limestone, notably including the Coral Rag Formation of the hills around Oxford (England), was once used as a building stone, and can be seen in some of the oldest buildings in that city including the Saxon tower of St Michael at the Northgate, St. George's Tower of Oxford Castle, and the medieval walls of the city.
== Preparation == Several preparation methods exist. Basic versions may be prepared using chopped meat, tomato, spices, and elbow macaroni. Another basic preparation method incorporates boxed, prepared macaroni and cheese and canned chili. Some recipes incorporate all of the ingredients together, while others are prepared with the ingredients separately layered. Those that use cheese may use grated cheese atop the dish, while others mix the cheese throughout the dish. Sometimes, onions or beans are added. Some diners in St. Louis, Missouri, serve a version called "chili mac a la mode", in which the dish is served topped with fried eggs. The dish may be prepared on a range top in a skillet, in a slow cooker, or baked as a casserole. Vegetarian and vegan versions of the dish are sometimes prepared.
== Books == The Malay Dilemma (1970) ISBN 981-204-355-1 The Challenge (1986) ISBN 967-978-091-0 Regionalism, Globalism, and Spheres of Influence: ASEAN and the Challenge of Change into the 21st century (1989) ISBN 981-303-549-8 Mahathir, Great Malaysian Hero (1990) ISBN 983-9683-00-4 The Asia That Can Say No (1994) ISBN 433-405-217-7 The Pacific Rim in the 21st century (1995) The Challenges of Turmoil (1998) ISBN 967-978-652-8 The Way Forward (1998) ISBN 0-297-84229-3 A New Deal for Asia (1999) Islam & The Muslim Ummah (2001) ISBN 967-978-738-9 Globalisation and the New Realities (2002) Reflections on Asia (2002) ISBN 967-978-813-X The Malaysian Currency Crisis: How and why it Happened (2003) ISBN 967-978-756-7 Mahathir: 22 Years, 22 Voices (2003) Dr Mahathir Mohamad - Father of Sports Development (2003) Achieving True Globalisation (2004) ISBN 967-978-904-7 Islam, Knowledge, and Other Affairs (2006) ISBN 983-3698-03-4 Principles of Public Administration: An Introduction (2007) ISBN 978-983-195-253-5 Chedet.com Blog Merentasi Halangan (Bilingual) (2008) ISBN 967-969-589-1 A Doctor in the House: The Memoirs of Tun Dr Mahathir Mohamad (2011) ISBN 9789675997228 Doktor Umum: Memoir Tun Dr. Mahathir Mohamad (2012) ISBN 9789674150259 Blogging to Unblock (Book 2): A Citizen's Rights (2013) ISBN 9789679696288 Dr. M: Apa Habaq Orang Muda? (2016) ISBN 9789671367995 Capturing Hope: The Struggle Continues for a New Malaysia (2021) ISBN 9789672923183 A Conversation with Tun Dr Mahathir bin Mohamad: A Legacy of Leadership and Vision (2025) ISBN 9789670821436
=== Lozano-Fernandez et al. (2019) === In 2019, similar to previous studies, such as Oakley et al. (2013) and Schwentner et al. (2017), Lozano-Fernandez et al. divided Pancrustacea into Allotriocarida, along with Oligostraca and Multicrustacea, as the three main divisions of subphylum Pancrustacea, embracing the traditional crustaceans and the hexapods (including insects). Lozano-Fernandez et al. also proposed a new group Athalassocarida for the Labiocarida plus Branchiopoda clade (derived from "Athalasso" [Greek: nonmarine] and "carida" [Greek: prawn]), thereby referring to a grouping of pancrustaceans where all extant members either live in nonmarine settings or reverted to a marine life-style secondarily.
Be in the region of the binding energy curve where a fission chain reaction is possible (i.e., above radium) Have a high probability of fission on neutron capture Release more than one neutron on average per neutron capture. (Enough of them on each fission, to compensate for non-fissions and absorptions in non-fuel material) Have a reasonably long half-life Be available in suitable quantities.
Sources: en.wikipedia.org
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.
The lyophilised powder is typically held at -20 C or lower in a dry, dark place. Reconstituted solutions are aliquoted and frozen to avoid repeated freeze-thaw cycles.