The short version of prohibited list fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-16. Anything still debated is marked as such rather than presented as settled.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | ≈889 Da for the 7-residue fragment | Full-length thymosin beta-4 is ≈4.9 kDa; catalogs differ |
| Appearance | White to off-white powder | Hygroscopic; weight shifts with residual moisture |
| Solubility class | Freely soluble in water | Also dissolves in aqueous buffers; poorly soluble in nonpolar solvents |
| Typical storage temperature | −20 °C, desiccated, protected from light | Once rehydrated, short-term holding at 2-8 °C |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity by UV absorbance; identity by ESI-MS or MALDI-TOF |
No major regulatory agency has approved TB-500 for therapeutic use, and it holds no pharmacopoeial monograph. The name appears on the World Anti-Doping Agency prohibited list within the class covering peptide hormones, growth factors, and related substances. Detection in doping control relies on mass spectrometric methods applied to urine, often after preparation steps that concentrate the analyte. Discussion of TB-500 therefore clusters in biochemistry, sports medicine, and anti-doping literature rather than in registered clinical trials.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
Laboratory work on thymosin beta-4 describes binding to monomeric actin and effects on cell migration, angiogenesis, and inflammatory signaling in cultured cells. Animal models have examined skin, corneal, and cardiac repair after injury, with outcomes reported mainly in preclinical literature. Most of that evidence concerns the parent protein rather than preparations labelled TB-500, so extrapolation from animal findings to a specific commercial product remains uncertain. Whether the two behave identically in living systems has not been established in controlled human studies.
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.
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.
A glycoprotein is a compound containing carbohydrate (or glycan) covalently linked to protein. The carbohydrate may be in the form of a monosaccharide, disaccharide(s), oligosaccharide(s), polysaccharide(s), or their derivatives (e.g. sulfo- or phospho-substituted). One, a few, or many carbohydrate units may be present. Proteoglycans are a subclass of glycoproteins in which the carbohydrate units are polysaccharides that contain amino sugars. Such polysaccharides are also known as glycosaminoglycans.
== Treatment == There is no cure for HCP caused by the deficient activity of coproporphyrinogen oxidase. Treatment of the acute symptoms of HCP is the same as for other acute porphyrias. Intravenous hemin (as heme arginate or hematin) is the recommended therapy for acute attacks. Acute attacks can be severe enough to cause death if not treated quickly and correctly. Hospitalization is typically required for administration of hemin, and appropriate drug selection is key to avoid exacerbating symptoms with drugs that interact poorly with porphyrias. Proper drug selection is most difficult when it comes to treatment of the seizures that can accompany HCP, as most anti-seizure medications can make the symptoms worse. Gabapentin and levetiracetam are two anti-seizure drugs that are thought to be safe. In patients where management of symptoms is difficult even with hemin, liver transplant is an option before the symptoms have progressed to advanced paralysis. Combined liver and kidney transplants are sometimes undertaken in people with kidney failure. Long-term treatment of acute porphyrias is centered on the avoidance of acute attacks by eliminating precipitating factors, such as drugs, dietary changes, and infections. Females often have attacks coincident with their menstrual cycle, which can be managed effectively with hormonal birth control. Because of the reduced penetrance of HCP, family members of a patient may carry the same mutation without ever presenting with symptoms.
=== Types === The conditions included under the term "congenital myopathy" can vary. One source includes nemaline myopathy, myotubular myopathy, central core myopathy, congenital fiber type disproportion, and multicore myopathy. The term can also be used more broadly, to describe conditions present from birth.
This requires duties of disclosure in how a retirement fund is run, funding and insurance to guard against insolvency, but not yet that voting rights are only cast on the instructions of investors. By contrast, the Undertakings for Collective Investment in Transferable Securities Directive 2009 does suggest that investors in a mutual fund or ("collective investment scheme") should control the voting rights. The UCITS Directive 2009 is primarily concerned with creating a "passport". If a firm complies with rules on authorisation, and governance of the management and investment companies in an overall fund structure, it can sell its shares in a collective investment scheme across the EU. This forms a broader package of Directives on securities and financial market regulation, much of which has been shaped by experience in the 2008 financial crisis. Additional rules on remuneration practices, separating depositary bodies in firms from management and investment companies, and more penalties for violations were inserted in 2014. These measures are meant to decrease the risk to investors that an investment goes insolvent. The Markets in Financial Instruments Directive 2004 applies to other businesses selling financial instruments. It requires similar authorisation procedures to have a "passport" to sell in any EU country, and transparency of financial contracts through duties to disclose material information about products being sold, including disclosure of potential conflicts of interest with clients.
== Theca externa == The theca externa is the outer layer of the theca in the follicle. It is derived from connective tissue, the cells resemble fibroblasts, and contain abundant collagen. During ovulation, the surge in luteinizing hormone (LH surge) increases cAMP which increases progesterone and PGF2α production. PGF2α induces the contraction of the smooth muscle cells of the theca externa, increasing intrafollicular pressure. This aids in rupture of the mature oocyte, or immature oocyte at the germinal vesicle stage in the canine, along with plasmin and collagenase degradation of the follicle wall.
Sources: en.wikipedia.org
The aromaticity varies for PAHs. According to Clar's rule, the resonance structure of a PAH that has the largest number of disjoint aromatic pi sextets—i.e. benzene-like moieties—is the most important for the characterization of the properties of that PAH.
==== October ==== On 1 October, shootings broke out after the infiltration of drones belonging to Ministry of Defense. On 7 October, the National Guard repelled an infiltration attempt by Syrian government forces in the town of Rima Hazem. On 8 October, protesters in Shahba demonstrated in support of the residents of Ashrafieh and Sheikh Maqsoud, during its siege in Aleppo clashes, waving flags of Syrian Democratic Forces and banners reading: "The siege of Sheikh Maqsoud and Ashrafieh is a siege of Suwayda" and "Long live the resistance of the SDF!" On 9 October, unknown Druze fighters attacked a government position in Walgha; the National Guard denied its participation. On 10 October, Syrian government forces and the National Guard clashed in northern Suwayda, with 23 mm cannons. On 11 October, a US delegation met with Hikmat al-Hijri and the National Guard, without the knowledge of Jihad Ghoutani, which created divisions in the National Guard. On the same day al-Hijri changed the name of Jabal al-Arab to "Jabal al-Bashan", a Hebrew term, which generated controversy in Suwayda, the matters were legally resolved by the National Guard. On 20 October, the National Guard repelled an infiltration attempt by Syrian government forces with 23mm heavy machine guns towards the town of Majdal. On 28 October, an attack occurred on a bus carrying Druze people on the Suwayda-Damascus highway, where two people, Aya Salam and Kamal Abdulbaqi, died.
If compelling archaeological reasons for supposing that the ages come from exactly contemporary samples do not exist, then results must be regarded as suspect. If there exists no prior reason to believe that two samples are truly of the same age, and even if their ages are statistically indistinguishable, they are as likely to be as far apart in true age as the measured difference between them as they are to be of the same age. Charcoal was seen historically as an ideal medium for carbon dating. When long-lived tree species, such as oak and juniper, are used, however, there is a particular danger of encountering the "old wood" problem. For example, the date being measured may be from heartwood, which is already many centuries old by the time the tree was felled. Another difficulty is that of a possible time-lag between felling and final deposition. The timber may have had an extensive history of use and re-use. A method of ameliorating this problem is to date young growth, if available, for example hazel twigs. Dating of artefacts using accelerator mass spectrometry is the gold standard dating method of today; charcoal-sourced dates are seen as unreliable. In establishing the chronology of a site, a representative spread of dates is required before interpretation can be attempted.
Cetacaine is a topical anesthetic that contains the active ingredients benzocaine (14%), butamben (2%), and tetracaine hydrochloride (2%). Cetacaine also contains small amounts of benzalkonium chloride at 0.5% and 0.005% of cetyl dimethyl ethyl ammonium bromide all in a bland water-soluble base. Although Cetacaine has been widely used in the medical and dental fields, it has yet to be officially approved by the FDA. Cetacaine is produced by the company Cetylite Industries, Inc. and they provide Cetacaine in three forms: liquid, gel, and spray.
=== Public engagement === Olabisi works with Mae Jemison on the grant project 100 Year Starship, an interdisciplinary initiative that is exploring the technologies necessary to achieve interstellar travel, with the goal that all such technologies would improve life on Earth (e.g., better power sources, clean energy, clothing that doesn't need washing). She presented the program and how it intersected with her work at the European Parliament in 2013. In 2016, she featured in a Vanity Fair and IBM collaboration celebrating women in science. In 2019, she was interviewed by Forbes.
Sources: en.wikipedia.org
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.
The name is a commercial label rather than a systematic chemical designation, so different vendors and papers attach it to different sequences. Some treat it as a fragment and others as the whole protein. Comparing two reports therefore requires checking what each one actually analyzed.
Typically it reflects the relative area of the main peak in a reversed-phase chromatogram at a given wavelength. It does not confirm the amino acid sequence, the counter-ion, or the amount of peptide by mass. Identity is normally established by a separate mass measurement.
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.