A practical reference on TB-500: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-04-26 and is reviewed periodically as new material appears.
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Thymosin beta-4 fragment; TB4 fragment | Naming is inconsistent across suppliers and publications |
| Reported sequence | Ac-LKKTETQ | Corresponds to residues 17-23 of the parent protein |
| Frequently cited registry number | 77591-33-4 | Associated with full-length thymosin beta-4 rather than the fragment |
| Common supplied form | Freeze-dried solid | Often presented as an acetate or trifluoroacetate salt |
| Regulatory treatment | Varies by country | Frequently handled as a research chemical; not broadly approved as a therapeutic |
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.
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.
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.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Normally pathogenic bacteria are weakened so they are no longer pathogenic. Commensal or food-grade bacteria which are not pathogenic. Using bacterial surface display of antigens is a valuable alternative to conventional vaccine design for various reasons, one of them being that the proteins expressed on the bacterial cell surface can act favourably as an adjuvant. Conventional vaccines require the addition of adjuvants. Another advantage of generating vaccines using bacterial display systems is that the whole bacterial cell can be incorporated in the live vaccine Unlike bacteriophage display systems which are generally used in vaccine development to find unknown epitopes, bacterial display systems are used to express known epitopes and the cells act as a vaccine delivery system.
=== Occurrence in space === Nitriles are among the most abundant organic molecules in space, and more than ten distinct compounds have been unequivocally detected. Hydrogen cyanide was one of the first polyatomic species identified in space and occurs there relatively frequently and in substantial quantities. Other nitriles detected in space include acetonitrile and aminoacetonitrile, as well as butyronitrile, cyanoacetylene, and cyanopolyins containing two to five conjugated triple bonds. Hydrogen cyanide, cyanoacetylene, and cyanogen are present in the atmosphere of Saturn's moon Titan.
== Factors affecting topical drug absorption == Topical drug absorption depends on two major factors – biological and physicochemical properties. The first factor concerns body structure effects on the drugs. The degradation of drugs can be affected by the site of applications. Some studies discovered different percutaneous absorption patterns. Apart from the place, age also affects the absorption as the skin structure changes with age. The lowered collagen and broadened blood capillary networks happen with aging. These features alter the effectiveness of absorption of both hydrophilic and lipophilic substances into stratum corneum underneath the surface of the skin. The skin surface integrity can also affect the permeability of drugs such as the density of hair follicles, sweat glands or disintegrated by inflammation or dehydration. The other factor concerns metabolism of medications on skin. When the percutaneous drug is applied on skin, it will be gradually absorbed down the skin. Normally, when the drugs are absorbed, they will be metabolised by various enzymes in our body and the amount will be lower. The exact amount delivered to the target action site determines the potency and bioavailability of the drugs. If the concentration is too low, the therapeutic effect is impeded; if the concentration is too high, drug toxicity may happen to cause side effects or even do harm to our body. For the topical drug delivery way, degradation of drugs in skin is very low compared to liver.
==== Horticulture ==== Some horticulturists and users of hydroponics advocate the use of weak hydrogen peroxide solution in watering solutions. Its spontaneous decomposition releases oxygen that enhances a plant's root development and helps to treat root rot (cellular root death due to lack of oxygen) and a variety of other pests. For general watering concentrations, around 0.1% is in use. This can be increased up to one percent for antifungal actions. Tests show that plant foliage can safely tolerate concentrations up to 3%.
Sources: en.wikipedia.org
Pickled tofu (豆腐乳 in Chinese, pinyin: dòufurǔ, or 腐乳 fŭrŭ; chao in Vietnamese), also called "preserved tofu" or "fermented tofu", consists of cubes of dried tofu that have been allowed to fully air dry under hay and slowly ferment with the help of aerial bacteria. The dry fermented tofu is then soaked in salt water, Chinese rice wine, vinegar or minced chili peppers, or in a mixture of whole rice, bean paste, and soybeans. In the case of red pickled tofu (紅豆腐乳 in Chinese, Pinyin: hóng dòufurǔ), red yeast rice (cultivated with Monascus purpureus) is added for color. In Japan, pickled tofu with miso paste is called tofu no misodzuke, and is a traditional preserved food in Kumamoto. In the Ryukyu Islands, pickled and fermented tofu is called tōfuyō (豆腐餻). It is made from Shima-dōfu (an Okinawan variety of large and firm tofu). It is fermented and matured with koji mold, red koji mold, and awamori. Stinky tofu (臭豆腐 in Chinese, Pinyin: chòudòufu) is soft tofu that has been fermented in a vegetable and fish brine. The blocks of tofu have a pungent cheese smell, sometimes resembling rotting food. Despite its strong odor, the flavor and texture of stinky tofu is appreciated by aficionados, who describe it as delightful. The texture of this tofu is similar to the soft East Asian tofu from which it is made. The rind that stinky tofu develops when fried is said to be best when especially crisp, and fried stinky tofu is usually served with soy sauce, sweet sauce, or hot sauce.
Grade 1 qualitative filter paper has the pore size of 11 μm. This grade of filter paper is widely used for many different fields in agricultural analysis, air pollution monitoring and other similar experiments. Grade 2 qualitative filter paper has the pore size of 8 μm. This grade of filter paper requires more filtration time than Grade 1 filter paper. This filter paper is used for monitoring specific contaminants in the atmosphere and soil testing. Grade 3 qualitative filter paper has the pore size of 6 μm. This grade of filter paper is very suitable for carrying samples after filtration. Grade 4 qualitative filter paper has the pore size of 20~25 μm. This grade of filter paper has the largest pore size among all standard qualitative filter papers. It is very useful as rapid filter for cleanup of geological fluids or organic extracts during experiment. Grade 602 h qualitative filter paper has the pore size of 2 μm. This grade of filter paper has the smallest pore size among all standard qualitative filter papers. It is used for collecting or removing fine particles.
Rentrop did not generalize about the functional significance of these collaterals, which he said was "unknown," but their existence suggests that they may exert a preemptive, protective effect. Subsequently, Rentrop's associate Cohen prospectively evaluated 23 patients undergoing PTCA and observed that during balloon inflation, the mean grade of collateral filling increased dramatically. Nineteen of 23 patients showed improvement (p=0.01) but post-PTCA arteriography revealed no visible collaterals in any patient. The functional effect of filling was dramatic: using an index of ischemia (based on the percent of hypocontractile perimeter of myocardium, sum of ST segment elevation, and time of onset of angina), Cohen found that grade 0 or 1 filling confers only nominal protection from ischemia (i.e., filling is non-existent or of side branches only), but partial filling (i.e. grade 2 or greater) of these segments provides almost complete preservation of the affected myocardium from the asynergy associated with critical coronary stenosis. Pain was observed in all nine patients with 0 or 1 filling, but in only five of 14 patients with grade 2 or 3 filling. Thus, the severity of symptoms correlated inversely with the degree of observed collateral filling. In another often-cited study, Freedman focused on the issue of MI prevention by selecting 121 patients with severe single vessel disease. 64 had Q-wave infarction and 57 did not; 32 had unstable angina or subendocardial infarction.
=== No development reported === AB-101 (RJ-101) – undefined mechanism of action – female sexual dysfunction [41] Apomorphine intranasal – non-selective dopamine receptor agonist, other actions – erectile dysfunction, female sexual dysfunction [42] Armodafinil ((R)-modafinil; D-modafinil; NH-02D; NH02D) – atypical dopamine reuptake inhibitor (DRI) – premature ejaculation [43] [44] Deuterated testosterone (d3-testosterone) – androgen (androgen receptor agonist) – female sexual dysfunction [45] Epelsiban (GSK557296; GSK-557296) – oxytocin receptor antagonist – premature ejaculation [46] Estradiol/testosterone topical gel (LibiGel-E/T; testosterone/estradiol topical gel) – combination of estradiol (estrogen) and testosterone (androgen) – female sexual dysfunction [47] Fibroblast growth factor 1 (FGF-1; FGF1; Acidic FGF; aFGF; Cardio Vascu-Grow; CVBT-141P; CVBT-141S; CVBT-141A; CVBT-141B; CVBT-141C; CVBT-141D; CVBT-141E; CVBT-141ED; CVBT-141F; CVBT-141G; CVBT-141H; FGF-1(141); VT-141D; VT-141ED; VT-141P; VT-141S) – fibroblast growth factor receptor (FGFR) agonist – erectile dysfunction [48] FKK-01PD (FKK-01PD; TGHW-01AP; TGHW01AP) – non-selective dopamine receptor agonist, other actions (apomorphine prodrug) – erectile dysfunction [49] GSK-958108 (GSK958108) – serotonin 5-HT1A receptor antagonist – premature ejaculation [50] HCP-1302 (HCP1302) – undefined mechanism of action – erectile dysfunction [51] Lidocaine topical gel – sodium channel blocker, local anesthetic – dyspareunia [52] PTL-2015 – undefined mechanism of action – erectile dysfunction [53] Research programme: nerve-targeted gene therapy - Periphagen (NC-3; NE-2; NE2-Endomorphin; NG-2; NG2-GAD; NN1-Neurotrophin) – various actions – erectile dysfunction [54] Research programme: sexual dysfunction therapy - Palatin Technologies (PL-6983) – melanocortin receptor modulators – erectile dysfunction, female sexual dysfunction [55] Sildenafil (KW-25084) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [56] Sildenafil orally soluble film (CURE-5003; CUREfilm Blue) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [57] Sildenafil oral spray (Duromist; NVD-401; SUD-003; SUD-004; SUDA-004; Sudamist) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [58] Tadalafil dry powder inhalation (Tadalafil Technosphere) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [59] Tadalafil orodispersible film tablet (Caliberi) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [60] Tadalafil topical (Extrinsa) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction [61] Tadalafil/tamsulosin – combination of tadalafil (phosphodiesterase PDE5 inhibitor) and tamsulosin (α1-adrenergic receptor antagonist) – erectile dysfunction [62] Tunodafil (ecocarbamate; gluconocin; yonkenafil) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [63] Vilazodone (EMD-68843; SB-659746A; Viibryd) – serotonin reuptake inhibitor (SRI), serotonin 5-HT1A receptor agonist – sexual function disorders [64] Zotarolimus (ABT-578; Endeavor; Endeavor Resolute; MDT-4107 DES; Resolute DES; Resolute Integrity; Resolute Onyx; ZoMaxx) – FK-binding protein 12 (FKBP12) ligand and mechanistic target of rapamycin (mTOR) inhibitor – erectile dysfunction [65]
The two substrates of this enzyme are allyl alcohol and oxidsed nicotinamide adenine dinucleotide phosphate (NADP+). Its products are acrolein, reduced NADPH, and a proton. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is allyl-alcohol:NADP+ oxidoreductase.
Sources: en.wikipedia.org
The leading proposal involves sequestration of monomeric actin, which would alter cytoskeletal turnover and cell movement. The actin-binding motif shared with the parent protein is central to that idea. Direct confirmation in whole organisms remains limited.
Very few controlled human studies focus on the seven-residue sequence itself. Most clinical data concern the full-length protein in cardiac or ophthalmic settings. Conclusions drawn for one form should not be assumed to transfer to the other.
Detection normally relies on reversed-phase liquid chromatography paired with mass spectrometry. Chromatographic retention time establishes the expected elution window, and the mass spectrum confirms the molecular ion. Immunoassays exist but can cross-react with related peptides.
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.