Everything below concerns RP-HPLC. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-03-27. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Lyophilized TB-500 is hygroscopic and should be kept dry before use. The usual storage recommendation for the solid is -20 °C, protected from light and moisture. Once dissolved, the peptide is less stable, and repeated freeze-thaw cycles can promote aggregation or degradation. Laboratories often divide a reconstituted solution into single-use aliquots and store them at -80 °C. Exact stability limits depend on buffer, pH, and concentration, so published data do not define a single universal condition.
Identity and purity are checked with chromatographic and mass spectrometric methods. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities, while mass spectrometry confirms the expected molecular mass. A certificate of analysis may report a purity percentage, but the laboratory should still verify the material independently. Common quality concerns include truncated sequences, deamidation, oxidation, and residual solvents from synthesis. Because TB-500 is short, some impurities can differ from the target by only a few mass units.
| 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 |
Reconstitution of a lyophilized peptide is normally done with sterile water or a suitable buffer under aseptic conditions. Adding solvent down the vial wall and allowing gentle dissolution instead of vigorous vortexing reduces the chance of aggregation, which can lower the effective concentration of the resulting solution. Concentrated stocks are usually diluted into working buffer shortly before use. Because no standard preparation protocol exists for TB-500 specifically, laboratories adapt general peptide handling practice, and reported results may reflect differing preparation choices.
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
TB-500 is a synthetic peptide whose sequence corresponds to a short fragment near the N-terminus of thymosin beta-4, a small protein present in most mammalian cells. The fragment is commonly cited as containing the actin-binding region of the parent molecule, which is why it appears in laboratory work on cell migration and tissue repair. Suppliers distribute it as a lyophilised powder intended for research use. Its identity is defined by amino acid sequence and by the presence of an acetyl group on the N-terminal residue.
Full-length thymosin beta-4 consists of roughly forty-three amino acids and ranks among the more abundant small proteins in the cytoplasm. The fragment is much shorter, so it cannot reproduce every function attributed to the intact molecule. In cell culture, short actin-binding motifs can interfere with filament dynamics and cell movement, but such observations come from controlled experiments rather than from whole-animal work. Whether a truncated fragment produces the same effects as the parent protein remains an open question.
The original game left her in a deserted parking lot after destroying GLaDOS, but the update involved Chell being dragged back into the facility by a "Party Escort Bot". Though Portal 2 was originally announced for a Q4 2010 release, the game was released on April 19, 2011. A modding community has developed around Portal, with users creating their own test chambers and other in-game modifications. The group "We Create Stuff" created an Adobe Flash version of Portal, titled Portal: The Flash Version, just before release of The Orange Box. This flash version was well received by the community and the group has since converted it to a map pack for the published game. Another mod, Portal: Prelude, is an unofficial prequel developed by an independent team of three that focuses on the pre-GLaDOS era of Aperture Science, and contains nineteen additional "crafty and challenging" test chambers. An ASCII version of Portal was created by Joe Larson. An unofficial port of Portal to the iPhone using the Unity game engine was created but only consisted of a single room from the game. Mari0 is a fan-made four-player coop mashup of the original Super Mario Bros. and Portal. An unofficial port for the Nintendo 64 console titled Portal 64 was under development by James Lambert. By September 2023, he had a working copy but still had ways to go to be completely finished. The project was taken down in January 2024 due to a request by Valve; according to Lambert, the port's reliance on "Nintendo's proprietary libraries" was the reason.
=== Effects on humans and animals === Ethylene oxide is an alkylating agent; it has irritating, sensitizing, and narcotic effects. Chronic exposure to ethylene oxide is also mutagenic. The International Agency for Research on Cancer classifies ethylene oxide into group 1, meaning it is a proven carcinogen. Ethylene oxide is classified as a class 2 carcinogen by the German MAK commission and as a class A2 carcinogen by the ACGIH. A 2003 study of 7,576 women exposed while at work in commercial sterilization facilities in the US suggests ethylene oxide is associated with breast cancer incidence. A 2004 follow up study analyzing 18,235 men and women workers exposed to ethylene oxide from 1987 to 1998 concluded "There was little evidence of any excess cancer mortality for the cohort as a whole, with the exception of bone cancer based on small numbers. Positive exposure-response trends for lymphoid tumors were found for males only. Reasons for the sex specificity of this effect are not known. There was also some evidence of a positive exposure-response for breast cancer mortality." An increased incidence of brain tumors and mononuclear cell leukemia was found in rats that had inhaled ethylene oxide at concentrations of 10, 33 or 100 mL/m3 (0.0100, 0.0329 or 0.0997 imp fl oz/cu ft) over a period of two years. An increased incidence of peritoneal mesotheliomas was also observed in the animals exposed to concentrations of 33 and 100 mL/m3 (0.0329 and 0.0997 imp fl oz/cu ft). Results of human epidemiological studies on workers exposed to ethylene oxide differ.
In humans, 24 copies of E2 arranged in octahedral symmetry form the core of the BCKDC. Non-covalently linked to this polymer of 24 E2 subunits are 12 E1 α2β2 tetramers and 6 E3 homodimers. In addition to the E1/E3-binding domain, there are 2 other important structural domains in the E2 subunit: (i) a lipoyl-bearing domain in the amino-terminal portion of the protein and (ii) an inner-core domain in the carboxy-terminal portion. The inner-core domain is linked to the other two domains of the E2 subunit by two interdomain segments (linkers). The inner-core domain is necessary to form the oligomeric core of the enzyme complex and catalyzes the acyltransferase reaction (shown in the "Mechanism" section below). The lipoyl domain of E2 is free to swing between the active sites of the E1, E2, and E3 subunits on the assembled BCKDC by virtue of the conformational flexibility of the aforementioned linkers (see Figure 2). Thus, in terms of function as well as structure, the E2 component plays a central role in the overall reaction catalyzed by the BCKDC.
Sources: en.wikipedia.org
A way to provide an investigational therapy to a patient who is not eligible to receive that therapy in a clinical trial, but who has a serious or life-threatening illness for which other treatments are not available. Compassionate use trials allow patients to receive promising but not yet fully studied or approved therapies when no other treatment option exists. Also called expanded access trial. (NCI) Complementary and alternative therapy
The soybean, soy bean, or soya bean (Glycine max) is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key food source, owing to its high protein and oil content. Soybean oil is widely used in cooking, as well as in industry. Traditional unfermented food uses of soybeans include edamame, as well as soy milk, from which tofu and tofu skin are made. Fermented soy foods include soy sauce, fermented bean paste, nattō, and tempeh. Fat-free (defatted) soybean meal is a significant and cheap source of protein for animal feeds and many packaged meals. For example, soybean products, such as textured vegetable protein (TVP), are ingredients in many meat and dairy substitutes. Soy-based foods are traditionally associated with East Asian cuisines, and still constitute a major part of East Asian diets, but processed soy products are increasingly used in Western cuisines. Soy was domesticated from the wild soybean (Glycine soja) in north-central China between 6,000 and 9,000 years ago. Brazil and the United States lead the world in modern soy production. The majority of soybeans are genetically modified, usually for either insect, herbicide, or drought resistance. Three-quarters of soy is used to feed livestock, which in turn go to feed humans. Increasing demand for meat has substantially increased soy production since the 1980s, and contributed to deforestation in the Amazon. Soybeans contain significant amounts of phytic acid, dietary minerals, and B vitamins.
In light of these events, Rush's record label tried to pressure the members into moulding their next album in a more commercially friendly and accessible fashion; the band ignored the requests and developed their next album 2112 (1976) with a 20-minute title track divided into seven sections. Despite that, the album was the Rush's first taste of significant commercial success as it reached No. 5 in Canada, becoming their first to reach double platinum certification. Rush toured in support of 2112 between February 1976 and June 1977 with concerts in Canada, the US, and for the first time Europe, with dates in the UK, Sweden, Germany, and the Netherlands. The three sold-out shows at Massey Hall in Toronto in June 1976 were recorded for Rush's debut live album, All the World's a Stage. Released in September of that year, the double album reached No. 6 in Canada and became Rush's first to crack the US top 40. Record World wrote: "Building its American reputation slowly but steadily Rush stands poised for breaking through all the way via this two record live set [...] All the highly charged electricity is here in an explosive setting." The liner notes include the statement, "This album to us, signifies the end of the beginning, a milestone to mark the close of chapter one, in the annals of Rush."
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.
The dry powder is normally kept at -20 °C, protected from light and moisture. Reconstituted solutions are often divided into aliquots and stored at -80 °C to reduce freeze-thaw damage.