TB-500 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.
Updated 2025-12-15. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| 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 |
Research interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
TB-500 is a catalogue name applied to a synthetic peptide related to thymosin beta-4, an actin-binding protein found in most mammalian cells. Suppliers do not use the label consistently: some describe it as the full 43-residue protein, others as a short fragment from the actin-binding region, and others as a related tetrapeptide. Because the name is commercial rather than chemical, two products sold under it may not contain the same molecule. This naming ambiguity is the first point to check in any description of the material.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
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.
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.
Both the first and second dimensions of 2DE are adaptable and easily modified to enhance proteome coverage as necessary (e.g. to focus on specific pI ranges, or to best resolve lower or higher MW species). This flexibility and adaptability further complements the additional analytical capacity enabled by excision and third electrophoretic separations of primary gel regions, as well as the subsequent deep imaging of the primary gel to expand the dynamic range of detection to even very low abundance proteoforms. Generally straightforward data analysis. High quality iTDP analyses are fully enabled by established mid-range LC/MS systems; while advanced and/or specialized systems continue to drive throughput and/or sequence coverage, these are not essential to enabling iTDP analyses. Western blotting after 2DE can also be used to capitalize on the availability of high-quality antibodies. Indeed, this was one of the first approaches to identify multiple variants (i.e. proteoforms) of a given protein in the same sample. Criteria to ensure the highest quality (quantitative) western blots are well-established if not always widely followed. The primary focus of the iTDP approach is the comprehensiveness of analyses (i.e. depth) and thus data quality, rather than high throughput. "It is not the rate or volume of data generated but rather the quality that ultimately matters".
== Preparation == The highly basic character of caricain makes it relatively easy to separate from the other papaya cysteine endopeptidases in cation-exchange chromatography of preparations of commercially available papaya latex. A sodium acetate gradient, pH 5.0, was first used successfully by Robinson and has since been adopted by others. Caricain is found in the latest-eluting protein peak. Due to the charge heterogeneity of caricain the peak may not be symmetrical, but this does not necessarily indicate the presence of contaminants. Covalent chromatography on thiol-Sepharose allows isolation of fully active caricain from the material obtained by cation exchange.
=== Column === The column used for GPC is filled with a microporous packing material. The column is filled with the gel. Since the total penetration volume is the maximum volume permeated by the analytes, and there is no retention on the surface of the stationary phase, the total column volume is usually large, relatively to the sample volume.
Lactinex is a brand name for a probiotic supplement used to replace microorganisms (gut flora) in the human intestines and colon. The brand is a registered trademark of Becton, Dickinson and Company. It may be used to treat diarrhea resulting from infection or when an antibiotic regimen destroys harmful bacteria and beneficial gut flora alike. The principal ingredient is one or more bacteria from the genus Lactobacillus regularly found in unpasteurized milk products (a blend of Lactobacillus acidophilus and Lactobacillus helveticus (bulgaricus)). It is considered a dietary supplement and is not a prescription. The brand Lactinex requires refrigeration because it contains live microorganisms. Similar ingredients are also found in freeze dried varieties that do not require refrigeration.
=== Applications for oceanography === Tracers are also used extensively in oceanography to study a wide array of processes. The isotopes used are typically naturally occurring with well-established sources and rates of formation and decay. However, anthropogenic isotopes may also be used with great success. The researchers measure the isotopic ratios at different locations and times to infer information about the physical processes of the ocean.
Sources: en.wikipedia.org
Das RC, Heath EC (1980). "Dolichyldiphosphoryloligosaccharide--protein oligosaccharyltransferase; solubilization, purification, and properties". Proc. Natl. Acad. Sci. U.S.A. 77 (7): 3811–5. Bibcode:1980PNAS...77.3811D. doi:10.1073/pnas.77.7.3811. PMC 349716. PMID 6933437.
Thermospray is a soft ionization source by which a solvent flow of liquid sample passes through a very thin heated column to become a spray of fine liquid droplets. As a form of atmospheric pressure ionization in mass spectrometry these droplets are then ionized via a low-current discharge electrode to create a solvent ion plasma. A repeller then directs these charged particles through the skimmer and acceleration region to introduce the aerosolized sample to a mass spectrometer. It is particularly useful in liquid chromatography-mass spectrometry (LC-MS). In more technical terms thermospray is the controlled partial vaporization of a liquid as it flows through a heated capillary tube. The nebulization is accomplished by pumping a liquid sample at moderately high pressure through an electrothermally heated capillary tube. When sufficient power is coupled to the flowing sample stream, a partially vaporized mixture is produced consisting of some fraction of vaporized sample and some remaining liquid sample. Upon exiting the heated capillary, the rapidly expanding sample vapor converts the remaining liquid stream to an aerosol. The produced vapor acts as a nebulizing 'gas' and aids the breakup of the liquid stream into droplets, in a process similar to pneumatic nebulization. Thus, conceptually this can be thought of as a pneumatic process where the expanding solvent vapor is used as a nebulizer gas. The solution leaves the tube as a supersonic jet or spray of very small droplets in solvent vapor.
== O == oligo - oligodeoxyribonucleotide - oligonucleotide - oligosaccharide-transporting ATPase - oncogene - oncovirus - open reading frame - operator - operon - origin of replication - ornithine(lysine) transaminase - osteomimicry
In fact, as revealed by the documentary, many men within the Mexican-American community considered women who received sterilizations as “mujeres de la calle”; wanton street walkers who wanted to sleep with multiple men at the same time. Such a reaction from their male counterparts had harmful effects on immigrant mothers. Maria Figueroa was barred from testifying in the lawsuit by her husband, and even attempted suicide in the aftermath of losing the ability to bear children. Gendered issues of bodily autonomy and sexual power relations were also a concern amongst Mexican-American women advancing the Chicano Student Movement. A lack of reproductive health counseling on college campuses contributed to the increasing dropout rates amongst Chicana students. Unplanned pregnancies and little to no access to birth control barred Chicana students from completing their undergraduate studies, though they tended to excel academically. There was also a general sense of skepticism amongst Mexican-American families about sending their children to American universities, as children were culturally expected to economically support their loved ones. Young Mexican-American women would also be expected to help raise their siblings—not have kids of their own just yet. Such a phenomenon across college campuses reflected a common double standard; Chicanos could enjoy their sexual freedom while assuming leadership positions in student activist groups while Chicana students were limited to supplemental roles in the movement and obligated to bear the brunt of an unplanned pregnancy.
Olaratumab, sold under the brand name Lartruvo, is a monoclonal antibody medication developed by Eli Lilly and Company for the treatment of solid tumors. It is directed against the platelet-derived growth factor receptor alpha. It was removed from the United States and European Union markets in 2019, due to insufficient proof of its medical advantage (see below "Medical uses").
Sources: en.wikipedia.org
He is also one of only two players in history to have two 40-30 seasons (Barry Bonds being the other). Bagwell is also the only first baseman to reach both 400 home runs and 200 stolen bases. He is just one of 21 players in history to win both a Rookie of the Year Award and an MVP. His 1,529 RBI during the span of his playing career ranked second for all hitters (first among right-handed hitters), and he was fifth in home runs. He was in the top 10 in the MVP voting five times. From 1994 to 2003, he led all first basemen in stolen bases, doubles, hits, runs, walks, and extra-base hits, was second in games and RBI, and was third in home runs. He is the Astros' all-time leader in home runs and RBI and is the first Astro to win an MVP. In addition to stealing over 200 bases in his career, Bagwell contributed significantly around the field as a whole. During one series against Pittsburgh in 1994, the Pirates shifted while he batted, and Bagwell responded with seven opposite-field hits. A standout defender at first base, he won the 1994 Gold Glove award. Remarked The Sporting News, "he's an extraordinary fielder who excels at charging bunts and throwing runners out at second and third. Although he has average speed, he's one of the game's smartest baserunners. ..." From 1999 to 2000, his 295 runs scored led the major leagues and set a National League two-season record.
The Cantley lab also was one of a few labs that nearly simultaneously identified LKB1 as a regulator of AMPK that also serves to regulate TORC1. For the discovery of PI-3-Kinase and its role in cancer metabolism, Cantley was one of eleven recipients of the inaugural Breakthrough Prize in Life Sciences, "the world's richest academic prize for medicine and biology. The prize, which carries a $3 million cash award, recognizes excellence in research aimed at curing intractable diseases and human life." The fundamental and far-reaching nature of the discovery of PI-3-kinase, together with Cantley's role in mapping the upstream regulation of PI-3-kinase and the downstream signaling pathways, have led to speculation that Cantley is a likely candidate for the Nobel prize in Medicine or Physiology. The growing evidence for a primary role for PI-3-kinase in cancer and its critical role in insulin signaling have served to strengthen the significance of this fundamentally important discovery. The first drug targeting the PI-3-kinase pathway as a treatment for cancer – Idelalisib (PI3K Delta inhibitor) – was approved by the FDA as a treatment for leukemia and two types of lymphoma in July 2014. Other drugs are currently in clinical development.
=== Legal status === In 2003, Bahrain classified tianeptine a controlled substance due to increasing reports of misuse and recreational use. In Russia, tianeptine (sold under the brand name "Coaxil") is a schedule III controlled substance in the same list as the majority of benzodiazepines and barbiturates. On 13 March 2020, with a decree approved by the Minister of Health, Italy became the first European country to outlaw tianeptine considering it a Class I controlled substance.
=== First Nations relations === In March 2021, Ford publicly accused MPP Sol Mamakwa of "jumping the line" to receive his second dose of a COVID-19 vaccine, despite being eligible to receive it. Mamakwa went to his riding to receive the vaccine as an attempt to prevent vaccine hesitancy amongst his constituents. On Thursday, March 11, 2021, Ford apologised for his remark and later said he "got a little personal" when throwing the accusation at Mamakwa. Mamakwa did not say that he accepted Ford's apology but stated that he appreciated the call from Ford. In September 2021, an Ontario judge issued an injunction on mining in Wiisinin Zaahgi'igan (an area sacred to the Ginoogaming First Nation peoples). The judge ruled that the Ontario government did not consult with the Ginoogaming as is their constitutional duty. Ford's 2024 Reducing Gridlock, Saving you Time Act removed the requirement for future Indigenous consultation for the upcoming Highway 413 in a possible contravention of Ontario's Environmental Assessment Act. In addition, the Indigenous consultation period for the bill was only 30 days, decried by the regional chief as 'too short'. Many Indigenous and environmental advocacy groups opposed his government's Protecting Ontario by Unleashing Our Economy Act, or Bill 5, which gives Ford's cabinet the ability to create special economic zones and exempt companies or projects from having to comply with any provincial law, provincial regulation or municipal bylaw. Ford also apologized for saying that First Nations "keep coming hat in hand" for government money in June 2025.
=== Cholesterol === In 1997, the FDA recognized the cholesterol lowering effect of oat β-glucan. In Europe, several health claim requests were submitted to the EFSA NDA Panel (Dietetic Products, Nutrition and Allergies), related to the role of β-glucans in maintenance of normal blood cholesterol concentrations and maintenance or achievement of a normal body weight. In July 2009, the Scientific Committee issued the following statements:
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.
Dry lyophilized powder is usually kept frozen, desiccated, and out of direct light. Sealed vials are not opened until needed, because moisture uptake can degrade short peptides. Longer archival storage is often done at lower temperatures than routine working stock.