A practical reference on prohibited list: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Literature and online discussion often conflate TB-500 with full-length thymosin beta-4, even though the two differ in size and are not interchangeable in analytical terms. The fragment is produced by solid-phase peptide synthesis, and the product is a defined seven-residue chain rather than a biological extract. Because the term is a trade-style label, two vendors may supply materials of the same nominal sequence but different counter-ion content, purity, or water content. Comparisons across studies are therefore difficult unless the exact sequence and purity are reported.
TB-500 is a research peptide whose sequence matches residues 17 to 23 of thymosin beta-4, a 43-residue protein present in most mammalian cells. The chain is seven amino acids long, written as LKKTETQ, and is normally supplied with an acetyl group on the N-terminus. Suppliers list it as a lyophilised powder under the code name TB-500, and the same sequence appears elsewhere in catalogues as the thymosin beta-4 actin-binding fragment. The label is commercial rather than systematic, so no single authority fixes exactly what TB-500 denotes.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
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 |
|---|---|---|
| Appearance | White to off-white powder | Supplied as a lyophilised cake in sealed vials |
| Solubility class | Freely soluble in water | Polar and charged side chains dominate the sequence |
| Typical storage temperature | -20 °C or below | Dry and dark; a desiccant is often recommended |
| Identity confirmation | Mass spectrometry | Observed mass compared with the theoretical value |
| Common synonyms | Thymosin beta-4 fragment | Also written as T beta 4 fragment 17-23 |
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.
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.
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.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
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.
=== Politics === DiCaprio endorsed Democratic candidate Hillary Clinton for the 2016 United States presidential election. In March 2020, DiCaprio attended a fundraiser for Joe Biden at the home of Paramount Pictures executive Sherry Lansing. Prior to the 2020 election, DiCaprio narrated a Netflix documentary series about voting rights, stating, "All of us may have been created equal. But we'll never actually be equal until we all vote. So don't wait." On social media, DiCaprio urged voters to make a plan to cast their ballots and to draw attention to voter suppression and restrictive voter ID laws, citing VoteRiders as a source of information and assistance. In 2023, DiCaprio testified during the trial against Prakazrel Michel, who is being accused of participating in a foreign influence campaign that was aimed at the Obama and Trump administrations. In 2024, DiCaprio formally endorsed Kamala Harris for president due to her policies on climate change mitigation, and criticized her Republican opponent Donald Trump.
== Z-plasty == This is based upon the principle of mobilizing a full segment of skin from an area to the site needing tissue replacement. The flaps are triangularly shaped opposite each other. It can be used in direct excision and closure of a contracted scar to produce a better looking and healing scar. It helps to elongate and break up a linear scar. It also gives a good result in the release of linear contractures. Z-plasty is of paramount importance to the plastic surgeon and a frequently used method in both single multiple forms.
=== Adverse effects === The most common adverse effects of medicinal nicotinic acid (500–3000 mg) are flushing (e.g., warmth, redness, itching or tingling) of the face, neck and chest, headache, abdominal pain, diarrhea, dyspepsia, nausea, vomiting, rhinitis, pruritus and rash. These can be minimized by initiating therapy at low dosages, increasing dosage gradually, and avoiding administration on an empty stomach. The acute adverse effects of high-dose nicotinic acid therapy (1–3 grams per day) – which is commonly used in the treatment of hyperlipidemias – can further include hypotension, fatigue, glucose intolerance and insulin resistance, heartburn, blurred or impaired vision, and macular edema. With long-term use, the adverse effects of high-dose nicotinic acid therapy (750 mg per day) also include liver failure (associated with fatigue, nausea, and loss of appetite), hepatitis, and acute liver failure; these hepatotoxic effects of nicotinic acid occur more often when extended-release dosage forms are used. The long-term use of nicotinic acid at greater than or equal to 2 grams per day also significantly increases the risk of cerebral hemorrhage, ischemic stroke, gastrointestinal ulceration and bleeding, diabetes, dyspepsia, and diarrhea.
== Biography == Stern was born and raised in Auvergne; her father is a Portuguese immigrant. After graduating secondary school and receiving her baccalauréat littéraire, she left Auvergne for Paris, where she studied visual arts at Paris 8 University Vincennes-Saint-Denis. She further studied architecture in Brussels.
Sources: en.wikipedia.org
It has only been within the last decade that technical advances (specifically in the field of Cryo-EM) have allowed for preliminary investigation into ribosomal behavior in other eukaryotes. In yeast, the LSU contains the 5S, 5.8S and 28S rRNAs. The combined 5.8S and 28S are roughly equivalent in size and function to the prokaryotic 23S rRNA subtype, minus expansion segments (ESs) that are localized to the surface of the ribosome which were thought to occur only in eukaryotes. However recently, the Asgard phyla, namely, Lokiarchaeota and Heimdallarchaeota, considered the closest archaeal relatives to Eukarya, were reported to possess two supersized ESs in their 23S rRNAs. Likewise, the 5S rRNA contains a 108‐nucleotide insertion in the ribosomes of the halophilic archaeon Halococcus morrhuae. A eukaryotic SSU contains the 18S rRNA subunit, which also contains ESs. SSU ESs are generally smaller than LSU ESs. SSU and LSU rRNA sequences are widely used for study of evolutionary relationships among organisms, since they are of ancient origin, are found in all known forms of life and are resistant to horizontal gene transfer. rRNA sequences are conserved (unchanged) over time due to their crucial role in the function of the ribosome. Phylogenic information derived from the 16s rRNA is currently used as the main method of delineation between similar prokaryotic species by calculating nucleotide similarity. The canonical tree of life is the lineage of the translation system.
A chromatography column is a device used in chromatography for the separation of chemical compounds. A chromatography column contains the stationary phase, allowing the mobile phase to pass through it.
There may be flocculation in some gels, which may produce an unstable gel. The rheology of some gels are easily altered by environmental factors such as temperature and humidity, resulting in stricter storage requirements. Syneresis of the gel may occur during storage, causing the gel to shrink unpredictably or even dry out. The gelators may precipitate and salt out, and some drugs may degrade in gel formulation due to the other ingredients present in the formulation. Some additives and gelators added into the formulation may cause irritation problems, such as skin irritation, dermatitis or allergic conditions. The increased water content in gels increases the chances of bacterial or fungal attack, which may contaminate the gel, making it unsuitable for use. Considering the direct route of administration, drugs must be very small in size to have an effective plasma concentration for action. The particle size and other properties of the drug may also affect its absorption through the skin barrier, resulting in an unreliable effect.
From a biochemical perspective, other challenges that immunoliposome therapies face are drug instability due to the phospholipid bilayer and the known possibility for hepatotoxicity. From a manufacturing perspective, designing liposome drug delivery systems at an industrial scale can present a challenge due to the complexity of these drug release mechanisms and their related biosafety.
== Health effects == Trifluoroacetic acid is a strong acid. TFA is harmful when inhaled, causes severe skin burns and is toxic for aquatic organisms even at low concentrations. Skin burns are severe, heal poorly and can be necrotic. Vapour fumes have an LC50 of 10.01 mg/L, tested on rats over 4 hours. Inhalation symptoms include mucus irritation, coughing, shortness of breath and possible formation of oedemas in the respiratory tract. Exposure damages the kidneys. TFA is also thought to be responsible for halothane-induced hepatitis. In 2024, the German Federal Institute for Risk Assessment (BfR) formally requested that the European Chemicals Agency (ECHA) reclassify TFA as "presumed" toxic to human reproduction, based on studies showing damage to animal fetuses. In June 2026, ECHA's Risk Assessment Committee (RAC) concluded that TFA fulfils the criteria for toxic to the reproduction class 1B, persistent, mobile and toxic (PMT) as well as very persistent and very mobile (vPvM). In July 2026, the European Food Safety Authority (EFSA) reduced the acceptable daily intake for TFA by 72%, from 0.05 mg/kg body weight/day down to 0.014. It also set the acute reference dose (ARfD) to 0.07 mg/kg body weight. These reductions were based on an assessment of new evidence, including changes in levels of the hormone thyroxine.
Sources: en.wikipedia.org
==== United States ==== In July 2025, the US Food and Drug Administration (FDA) formally recommended that the Drug Enforcement Administration (DEA) classify 7-OH-MIT as a controlled substance. This action was publicized to not be targeting Mitragyna speciosa leaf powder itself. Despite claims by marketers for products that contain 7-OH-MIT that they can be used to treat anxiety and pain, the drug is not approved by the FDA for any medical use or as a food supplement.
Durability of the effect of mitomycin gel in subjects with a complete response was also evaluated using urine cytology, ureteroscopy and biopsy (if warranted) every three months for a year following the initiation of therapy. Nineteen subjects (46%) who achieved a complete response continued to have a complete response at the twelve-month mark. The US Food and Drug Administration (FDA) granted the application for mitomycin gel priority review along with breakthrough therapy, fast track, and orphan drug designations. The FDA granted approval of Jelmyto to UroGen Pharma, Inc. The efficacy of mitomycin C for the treatment of recurrent low-grade intermediate-risk non-muscle invasive bladder cancer was evaluated in ENVISION (NCT05243550), a single-arm, multi-center trial in 240 adults with low-grade non-muscle invasive bladder cancer that recurred after prior transurethral resection of bladder tumor and met 1-2 of the following criteria: multiple tumors, a solitary tumor >3 cm, and/or recurrence within one year. Participants received 75 mg mitomycin intravesical solution instilled once a week for six consecutive weeks. Assessment of tumor status was performed every three months by cystoscopy, for-cause biopsy, and urine cytology.
This step is the enzymatic transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP by phosphoglycerate kinase, forming ATP and 3-phosphoglycerate. At this step, glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have now been synthesized. This step, one of the two substrate-level phosphorylation steps, requires ADP; thus, when the cell has plenty of ATP (and little ADP), this reaction does not occur. Because ATP decays relatively quickly when it is not metabolized, this is an important regulatory point in the glycolytic pathway. ADP actually exists as ADPMg−, and ATP as ATPMg2−, balancing the charges at −5 both sides. Cofactors: Mg2+
=== Military === As of 2020, three modified Ilyushin Il-86VKP remained in service with the Russian Air Force, down from four aircraft in 2010. The type had already been operated by and taken over from the former Soviet Air Force.
Sources: en.wikipedia.org
No. Thymosin beta-4 is a 43-residue protein, while TB-500 matches only residues 17 to 23 of that chain. The two are related but differ in size, and a method that identifies one does not automatically identify the other.
It corresponds to the actin-binding region of thymosin beta-4. Commercial synthesis reproduces that seven-residue stretch, usually with an acetyl group on the N-terminus.
It is not authorised as a medicine in the United States or the European Union and is distributed as a research chemical. Labels consequently carry research-use-only statements rather than clinical indications.
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.