Everything below concerns actin-binding motif. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-07-20. Numbers and descriptions here follow the published literature rather than marketing material.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized cake or fluffy solid |
| Water solubility | High | Dissolves in water and neutral buffers |
| Dry storage | -20 °C or below | Dry, dark, desiccated |
| Reconstituted storage | Frozen, single thaw | Repeated freeze-thaw promotes loss |
| Purity method | Reverse-phase HPLC | Peak area read at 214 or 220 nm |
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.
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.
Reconstitution practices affect downstream measurements. The dry powder is typically dissolved in sterile water or a suitable aqueous buffer, then mixed gently rather than vortexed at high speed. Visible particles or cloudiness suggest incomplete dissolution or contamination and should be investigated. For long-term storage, aliquots should be labeled with concentration, solvent, and date. Open questions include how different buffers alter peptide conformation and whether specific container materials adsorb the peptide. Those variables can change apparent concentration in assays even when the chemical identity is correct.
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.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
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.
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.
Apoptosis, a form of controlled cell death, has been suggested to be regulated by O-GlcNAc. In various cancers, elevated O-GlcNAc levels have been reported to suppress apoptosis. Caspase-3, caspase-8, and caspase-9 have been reported to be modified by O-GlcNAc. Caspase-8 is modified near its cleavage/activation sites; O-GlcNAc modification may block caspase-8 cleavage and activation by steric hindrance. Pharmacological lowering of O-GlcNAc with 5S-GlcNAc accelerated caspase activation while pharmacological raising of O-GlcNAc with thiamet-G inhibited caspase activation.
Small size provides many advantages to arboreal species: such as increasing the relative size of branches to the animal, lower center of mass, increased stability, lower mass (allowing movement on smaller branches) and the ability to move through more cluttered habitat. Size relating to weight affects gliding animals such as the sugar glider. Some species of primate, bat and all species of sloth achieve passive stability by hanging beneath the branch. Both pitching and tipping become irrelevant, as the only method of failure would be losing their grip.
== Dietary sources == Good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans. Another common source of phenylalanine is anything sweetened with the artificial sweetener aspartame, such as diet drinks, diet foods and medication; the metabolism of aspartame produces phenylalanine as one of the compound's metabolites.
Chikungunya vaccines are vaccines intended to provide acquired immunity against the chikungunya virus. As of 2025, two vaccines have been licensed in some countries. These are Ixchiq, a live attenuated vaccine from Valneva, and Vimkunya manufactured by Bavarian Nordic which utilises virus-like particle technology. The most commonly reported side effects of Ixchiq include tenderness at the injection site, as well as headache, fatigue, muscle pain, joint pain, fever, and nausea. However the license for Ixchiq has been suspended or restricted in some countries due to the risk of severe side effects, particularly in older people.
Cys arylation Free thiols has been considered unfavorable for Pd-mediated reactions due to Pd-catalyst decomposition. However, PdII oxidative addition complexes (OACs) supported by dialkylbiaryl phosphine ligands have shown to work efficiently towards cysteine S-arylation. The first example is the use of PdII OAC with RuPhos: The PdII complex resulting from the oxidative addition of aryl halides or trifluoromethanesulfonates and using RuPhos as the ligand could chemoselectively modify cysteines in various buffer with 5% organic co-solvent under neutral pH. This method has been shown to modify peptides and proteins, achieve peptide macrocyclization (by using bis-palladium reagent and peptides with two unprotected cysteines) and synthesizing antibody-drug conjugates (ADCs). Changing the ligand to sSPhos supports the PdII complex to be sufficiently water soluble to achieve cysteine S-arylation under cosolvent-free aqueous conditions.
Sources: en.wikipedia.org
Continuity equations more generally can include "source" and "sink" terms, which allow them to describe quantities that are often but not always conserved, such as the density of a molecular species which can be created or destroyed by chemical reactions. In an everyday example, there is a continuity equation for the number of people alive; it has a "source term" to account for people being born, and a "sink term" to account for people dying. Any continuity equation can be expressed in an "integral form" (in terms of a flux integral), which applies to any finite region, or in a "differential form" (in terms of the divergence operator) which applies at a point. Continuity equations underlie more specific transport equations such as the convection–diffusion equation, Boltzmann transport equation, and Navier–Stokes equations. Flows governed by continuity equations can be visualized using a Sankey diagram.
Despite their ethnic diversity and linguistic distinctions, the various Quechua ethnic groups have numerous cultural characteristics in common. They also share many of these with the Aymara or other Indigenous peoples of the central Andes. Traditionally, Quechua identity is locally oriented and inseparably linked in each case with the established economic system. It is based on agriculture in the lower altitude regions, and on pastoral farming in the higher regions of the Puna. The typical Andean community extends over several altitude ranges and thus includes the cultivation of a variety of arable crops and/or livestock. The land is usually owned by the local community (ayllu) and is either cultivated jointly or redistributed annually.
=== Interactions === IRAP has been reported to interact through its cytoplasmic domain with various proteins involved in vesicular trafficking, organelle tethering, and cytoskeleton remodeling. These proteins include tankyrase-1, tankyrase-2, and p115, which regulate Golgi vesicle trafficking; vimentin, an intermediate cytoskeleton filament; and the actin remodeling protein FHOS. Furthermore, IRAP was found to associate with AS160/Tbc1d4, a Rab GTPase activating protein (GAP) specific for Rab8, 10, and 14. This suggests that IRAP plays a role in recruiting AS160 to endocytic membranes. Apart from its association with intracellular trafficking proteins, IRAP has also been also observed to interact with proteins present in Glut4 storage vesicles (GSVs), such as sortilin, LRP1 and Glut4 in adipocytes. Under inflammatory conditions its role in GSV trafficking in adipocytes is regulated by the TNFa protein via glycosylation. Recently, its interaction with the z chain of the TCR (T-cell receptor) and the Lck kinase in T lymphocytes was discovered. In dendritic cells, IRAP-dependent vesicle trafficking and translocation to the phagocytic cup is regulated by immune receptors, such as TLR4 and FcgRs. Finally, IRAP has been proposed to interact with major histocompatibility complexes class-I (MHC-I) in specialized endosomes in DCs. There it exhibits roles in antigen cross-presentation.
=== Metabolism === DHEA is transformed into DHEA-S by sulfation at the C3β position via the sulfotransferase enzymes SULT2A1 and to a lesser extent SULT1E1. This occurs naturally in the adrenal cortex and during first-pass metabolism in the liver and intestines when exogenous DHEA is administered orally. Levels of DHEA-S in circulation are approximately 250 to 300 times those of DHEA. DHEA-S in turn can be converted back into DHEA in peripheral tissues via steroid sulfatase (STS). The terminal half-life of DHEA is short at only 15 to 30 minutes. In contrast, the terminal half-life of DHEA-S is far longer, at 7 to 10 hours. As DHEA-S can be converted back into DHEA, it serves as a circulating reservoir for DHEA, thereby extending the duration of DHEA. Metabolites of DHEA include DHEA-S, 7α-hydroxy-DHEA, 7β-hydroxy-DHEA, 7-keto-DHEA, 7α-hydroxyepiandrosterone, and 7β-hydroxyepiandrosterone, as well as androstenediol and androstenedione.
Sources: en.wikipedia.org
=== Non-canonical/alternate pathway === A select set of cell-differentiating or developmental stimuli, such as lymphotoxin β-receptor (LTβR), BAFF or RANKL, activate the non-canonical NF-κB pathway to induce NF-κB/RelB:p52 dimer in the nucleus. In this pathway, activation of the NF-κB inducing kinase (NIK) upon receptor ligation led to the phosphorylation and subsequent proteasomal processing of the NF-κB2 precursor protein p100 into mature p52 subunit in an IKK1/IKKa dependent manner. Then p52 dimerizes with RelB to appear as a nuclear RelB:p52 DNA binding activity. RelB:p52 regulates the expression of homeostatic lymphokines, which instructs lymphoid organogenesis and lymphocyte trafficking in the secondary lymphoid organs. In contrast to the canonical signaling that relies on NEMO-IKK2 mediated degradation of IκBα, -β, -ε, non-canonical signaling depends on NIK mediated processing of p100 into p52. Given their distinct regulations, these two pathways were thought to be independent of each other. However, it was found that syntheses of the constituents of the non-canonical pathway, viz RelB and p52, are controlled by canonical IKK2-IκB-RelA:p50 signaling. Moreover, generation of the canonical and non-canonical dimers, viz RelA:p50 and RelB:p52, within the cellular milieu are mechanistically interlinked. These analyses suggest that an integrated NF-κB system network underlies activation of both RelA and RelB containing dimer and that a malfunctioning canonical pathway will lead to an aberrant cellular response also through the non-canonical pathway.
== Sponsorship == In April 2022, the team announced their sponsorship with car retailer Cazoo starting in July 2022. The Cazoo brand is visible on the front of the new jerseys as the team's main sponsor. In addition to the Bundesliga professionals, Cazoo appeared as shirt sponsor and advertising partner of the second team of SC Freiburg in the third division and as co-sponsor of the Freiburg Football School, and became visible at all matches of the SC junior teams. Cazoo also became a co-sponsor and sleeve sponsor of SC Freiburg's Bundesliga women.
The dye substance is a mucous secretion from the hypobranchial gland of one of several species of medium-sized predatory sea snails that are found in the eastern Mediterranean Sea, and off the Atlantic coast of Morocco. David Jacoby remarks that "twelve thousand snails of Murex brandaris yield no more than 1.4 grams (22 grains) of pure dye, enough to colour only the trim of a single garment." These are the marine gastropods Bolinus brandaris the spiny dye-murex (originally known as Murex brandaris Linnaeus, 1758), the banded dye-murex Hexaplex trunculus, the rock-shell Stramonita haemastoma, and less commonly a number of other species such as Bolinus cornutus. The dye is an organic compound of bromine (i.e., an organobromine compound), a class of compounds often found in algae and in some other sea life, but much more rarely found in the biology of land animals. This dye is in contrast to the imitation purple that was commonly produced using cheaper materials than the dyes from the sea snail. In nature, the snails use the secretion as part of their predatory behaviour to sedate prey and as an antimicrobial lining on egg masses. The snail also secretes this substance when it is attacked by predators, or physically antagonized by humans (e.g., poked). Therefore, the dye can be collected either by "milking" the snails, which is more labor-intensive but is a renewable resource, or by collecting and destructively crushing the snails. The dye is collected via the snail-harvesting process, involving the extraction of the hypobranchial gland (located under the mollusk's mantle).
=== From minerals and other natural occurrences === In some places, there is no clear source of perchlorate, and it may be naturally occurring. Natural perchlorate on Earth was first identified in terrestrial nitrate deposits /fertilizers of the Atacama Desert in Chile as early as the 1880s and for a long time considered a unique perchlorate source. The perchlorate released from historic use of Chilean nitrate based fertilizer which the U.S.imported by the hundreds of tons in the early 19th century can still be found in some groundwater sources of the United States, for example Long Island, New York. Recent improvements in analytical sensitivity using ion chromatography based techniques have revealed a more widespread presence of natural perchlorate, particularly in subsoils of Southwest USA, salt evaporites in California and Nevada, Pleistocene groundwater in New Mexico, and even present in extremely remote places such as Antarctica. The data from these studies and others indicate that natural perchlorate is globally deposited on Earth with the subsequent accumulation and transport governed by the local hydrologic conditions. Despite its importance to environmental contamination, the specific source and processes involved in natural perchlorate production remain poorly understood. Laboratory experiments in conjunction with isotopic studies have implied that perchlorate may be produced on earth by oxidation of chlorine species through pathways involving ozone or its photochemical products.
=== Implementing agencies === Bureau of Industry and Security Directorate of Defense Trade Controls Office of Foreign Assets Control U.S. Customs and Border Protection United States Department of Commerce (Export Administration Regulations, EAR) United States Department of Defense United States Department of Energy (nuclear technology) United States Department of Homeland Security (border crossings) United States Department of Justice (including ATF and FBI) United States Department of State (International Traffic in Arms Regulations, ITAR) United States Department of the Treasury
Sources: en.wikipedia.org
Short transit at ambient temperature is generally tolerated, but long-term storage at room temperature is not recommended. Heat, moisture, and light all accelerate degradation. Cold, dry, dark storage is the conventional choice.
Suppliers typically quote a percentage derived from reverse-phase HPLC peak area. That figure reflects the relative amount of the main peak and does not by itself confirm identity or exclude related impurities. Mass spectrometry is commonly paired with it for confirmation.
Peptides purified by reverse-phase chromatography often carry trifluoroacetate as a counter-ion, which adds mass and can affect solubility and apparent behavior in assays. Acetate and hydrochloride forms are also offered. Knowing which form is present matters when calculating how much peptide a given weight contains.
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.