A practical reference on reversed-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-05-14 and is reviewed periodically as new material appears.
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.
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.
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.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
| 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 |
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
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.
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.
==== European Commission ==== In February 2024, the European Commission launched an investigation into TikTok for potential violations of the Digital Services Act (DSA), involving content aiming at children and advertising transparency. In April 2024, the European Commission opened a second investigation into TikTok to assess whether it broke EU law. In October 2024, the European Commission requested additional information from TikTok relating to its algorithm and risks around elections, mental health, and protection of minors. In December 2024, the European Commission announced an investigation into TikTok over accusations of Russian interference in the 2024 Romanian presidential election. In May 2025, the European Commission found TikTok had violated digital advertising rules under the DSA.
=== Injections and implants === In 1933 or 1934, Schering introduced progesterone in oil solution as a medication by intramuscular injection under the brand name Proluton. This was the first pharmaceutical formulation of progesterone to be marketed for medical use. It was initially a corpus luteum extract, becoming pure synthesized progesterone only subsequently. A clinical study of the formulation was published in 1933. Multiple formulations of progesterone in oil solution for intramuscular injection, under the brand names Proluton, Progestin, and Gestone, were available by 1936. A parenteral route was used because oral progesterone had very low activity and was thought to be inactive. Progesterone was initially very expensive due to the large doses required. However, with the start of steroid manufacturing from diosgenin in the 1940s, costs greatly decreased. Subcutaneous pellet implants of progesterone were first studied in women in the late 1930s. They were the first long-acting progestogen formulation. Pellets were reported to be extruded out of the skin within a few weeks at high rates, even when implanted beneath the deep fascia, and also produced frequent inflammatory reactions at the site of implantation. In addition, they were absorbed too slowly and achieved unsatisfactorily low progesterone levels. Consequently, they were soon abandoned, in favor of other preparations such as aqueous suspensions.
The Moskovskaya Okruzhnaya Zheleznaya Doroga (orbital railway line) has formed a ring around Moscow's current downtown since 1903. However, this line was a non-electrified, locomotive-only railway before reconstruction into the MCC during the 2010s. The Moscow Central Circle is a 54-kilometer (34 mi) orbital urban rail transit line that encircles historic Moscow. This line was built alongside the Little Ring of the Moscow Railway, incorporating some of its tracks. The MCC was opened for passenger use on 10 September 2016. The MCC line is operated by the Moscow government-owned company MKZD through the Moscow Metro, with the federal government-owned Russian Railways as the operations subcontractor.
== Structure == Mammalian GPX1, GPX2, GPX3, and GPX4 (this protein) have been shown to be selenium-containing enzymes, whereas GPX6 is a selenoprotein in humans with cysteine-containing homologues in rodents. In selenoproteins, the amino acid selenocysteine is inserted in the nascent polypeptide chain during the process of translational recoding of the UGA stop codon. GPX4 shares the amino acid motif of selenocysteine, glutamine, and tryptophan (catalytic triad) with other glutathione peroxidases.
==== MeSH E05.318.760 – epidemiologic study characteristics ==== MeSH E05.318.760.500 – epidemiologic studies MeSH E05.318.760.500.500 – case-control studies MeSH E05.318.760.500.500.500 – retrospective studies MeSH E05.318.760.500.750 – cohort studies MeSH E05.318.760.500.750.500 – longitudinal studies MeSH E05.318.760.500.750.500.350 – follow-up studies MeSH E05.318.760.500.750.500.650 – prospective studies MeSH E05.318.760.500.875 – cross-sectional studies MeSH E05.318.760.500.950 – seroepidemiologic studies MeSH E05.318.760.500.950.375 – hiv seroprevalence MeSH E05.318.760.535 – clinical trials MeSH E05.318.760.535.200 – clinical trials, phase i MeSH E05.318.760.535.210 – clinical trials, phase ii MeSH E05.318.760.535.220 – clinical trials, phase iii MeSH E05.318.760.535.230 – clinical trials, phase iv MeSH E05.318.760.535.365 – controlled clinical trials MeSH E05.318.760.535.365.500 – randomized controlled trials MeSH E05.318.760.535.500 – multicenter studies MeSH E05.318.760.550 – feasibility studies MeSH E05.318.760.565 – intervention studies MeSH E05.318.760.750 – pilot projects MeSH E05.318.760.875 – sampling studies MeSH E05.318.760.900 – twin studies
Sources: en.wikipedia.org
== Further reading == Zachara, Natasha; Akimoto, Yoshihiro; Hart, Gerald W. (2015), Varki, Ajit; Cummings, Richard D.; Esko, Jeffrey D.; Stanley, Pamela (eds.), "The O-GlcNAc Modification", Essentials of Glycobiology (3rd ed.), Cold Spring Harbor Laboratory Press, PMID 28876858.
=== The catalytic domain === X-ray crystallographic structures of several MMP catalytic domains have shown that this domain is an oblate sphere measuring 35 x 30 x 30 Å (3.5 × 3 x 3 nm). The active site is a 20 Å (2 nm) groove that runs across the catalytic domain. In the part of the catalytic domain forming the active site there is a catalytically important Zn2+ ion, which is bound by three histidine residues found in the conserved sequence HExxHxxGxxH. Hence, this sequence is a zinc-binding motif. The gelatinases, such as MMP-2, incorporate Fibronectin type II modules inserted immediately before in the zinc-binding motif in the catalytic domain.
=== Channel 5 === In 2010, Willis replaced Melinda Messenger on the Channel 5 series Live from Studio Five, but she left after only two months to co-present Big Brother's Little Brother and was replaced by Jayne Middlemiss. In August 2011, she returned to the revived series, presenting the spin-off show Big Brother's Bit on the Side. On 13 March 2013, it was reported that Brian Dowling would be axed from Big Brother and be replaced by Willis with a source saying, 'Brian has been a great host but Emma is seen by channel chiefs as a true successor to Davina. They're talking to her now about taking over the role from the summer.' Her appointment as host was confirmed on 2 April 2013. On 13 June 2013, she began presenting the fourteenth series of Big Brother. As well as presenting the main Big Brother and celebrity series, she continued to host the spin-off show Bit on the Side, sharing the presenting duties with Rylan Clark. On 2 February 2015, it was announced that Willis was to present her final edition of Bit on the Side that night, and Clark would take over as the main presenter of the spin off show. Willis interrogated Winston McKenzie during his exit interview on Celebrity Big Brother over his controversial opinions. Willis has expressed personal pride on this moment in her career. On 30 March 2014, Willis presented the Mum of the Year Awards, with the highlights being shown on Channel 5 that same evening.
== Purpose == Without trichrome staining, discerning one feature from another can be extremely difficult. Smooth muscle tissue, for example, is hard to differentiate from collagen. A trichrome stain can colour the muscle tissue red, and the collagen fibres green or blue. Liver biopsies may have fine collagen fibres between the liver cells, and the amount of collagen may be estimated based on the staining method. Trichrome methods are now used for differentiating muscle from collagen, pituitary alpha cells from beta cells, fibrin from collagen, and mitochondria in fresh frozen muscle sections, among other applications. It helps in identifying increases in collagenous tissue (i.e., fibrotic changes) such as in liver cirrhosis and distinguishing tumours arising from muscle cells and fibroblasts.
=== Environmental factors === A significant number of environmental factors have been implicated in the development and progression of various autoimmune diseases, either directly or as catalysts. Current research suggests that up to seventy percent of autoimmune diseases could be attributed to environmental influences, which encompass an array of elements such as chemicals, infectious agents, dietary habits, and gut dysbiosis. However, a unifying theory that definitively explains the onset of autoimmune diseases remains elusive, emphasizing the complexity and multifaceted nature of these conditions. Various environmental triggers are identified, some of which include:
Sources: en.wikipedia.org
=== Voice acting === As an actor, French appeared on the 1996 NBC miniseries Pandora's Clock as a non-commissioned officer. He was best known for voice acting work in video games by Valve Corporation, most notably Father Grigori in Half-Life 2, Bill in Left 4 Dead and Left 4 Dead 2 and the Elder Titan in Dota 2. He additionally voiced the Scientist in Gunman Chronicles and the Fisherman in the tech demo Half-Life 2: Lost Coast.
Despite pushes for talks, Israeli defense minister Israel Katz publicly vowed to "intensify and expand" Israeli attacks in Iran. The same day, the Shahid Khondab Heavy Water Complex in Arak—which has in the past been used to test uranium enrichment—and the Ardakan yellowcake production plant in Yazd Province were confirmed to have been damaged in Israeli airstrikes.
The next day, a rescue operation was organised, with a C-54 being deployed to Faya-Largeau to support one Skyraider and one French Army Light Aviation SA 330 Puma helicopter. However, a few minutes after taking off from Faya-Largeau, the C-54 was hit by two SA-7s, and its pilot performed an emergency landing while two of the aircraft's engines were on fire. All five crew members survived, and were picked up by the Puma helicopter. The SA-7 threat effectively put an end to the ENT's operations in the Faya area. Unsupported, the town's garrison collapsed on 18 February. In the face of the Libyan-supported rebel onslaught, the Chadian president, General Félix Malloum, requested a French military intervention. The French government agreed, and thus Opération Tacaud was launched in early April. The ENT went back into action on 16 April during the FROLINAT's offensive on Salal, together with French Air Force aircraft. One of its Skyraiders was shot down by an SA-7, and its pilot was killed. Even though the ANT garrison in Salal was eventually overrun by the insurgents, the French intervention was successful in stopping the rebels' advance towards the capital, N'Djamena. It also exacerbated the dissensions between the different rebel factions. The situation culminated in late summer 1978, when Hissène Habré's faction, the Armed Forces of the North (Forces Armées du Nord or FAN), defected and joined the government's forces. In turn, Habré was appointed as Chad's prime minister by Malloum.
=== Physical characteristics === Diallyl disulfide has a strong garlic smell. It is a clear, yellowish liquid which boils at 138–139 °C (for the typical 80% purity) and has its flash point at 50 °C, a density of about 1.0 g/mL and a vapor pressure of 1 mmHg at 20 °C. It is non-polar; therefore, diallyl disulfide is insoluble in water and is soluble in fats, oils, lipids, and non-polar solvents such as hexane or toluene.
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.
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.