The short version of TB-500 fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-12-03 and is reviewed periodically as new material appears.
The seven-residue chain carries several polar and charged side chains, so it dissolves readily in water and in aqueous buffers near neutral pH. No cysteine is present, so disulphide formation is not a concern and reducing agents are unnecessary. Dilute ammonium hydroxide or acetonitrile-water mixtures are sometimes used for stock solutions when initial dissolution is slow. Strongly alkaline conditions and prolonged contact with oxidising agents are avoided because they can modify lysine-containing stretches, and haze in solution usually signals incomplete dissolution or aggregated material.
Identity and purity are checked with reversed-phase high-performance liquid chromatography, which separates the target sequence from truncated or deletion analogues, and with mass spectrometry, which confirms the expected molecular mass. Amino acid analysis and peptide mapping give orthogonal confirmation but are used less often outside specialist laboratories. Counter-ion content varies: material purified on trifluoroacetic acid gradients retains trifluoroacetate, and ion exchange can convert the salt form. Residual water and solvent are measured by Karl Fischer titration or thermogravimetric analysis, and any purity figure should be read together with the method used to obtain it.
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.
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 |
|---|---|---|
| Water content | Low in freshly lyophilised material | Rises after repeated opening of the same vial |
| Solution stability | Lower than powder stability | Frozen aliquots are preferred over repeated thawing |
| Purity assessment | Reversed-phase HPLC with UV detection | Peak-area percentage excludes salts and water |
| Salt form | Often the trifluoroacetate salt | Retained from acidic purification gradients |
| Light sensitivity | Not strongly photoreactive | Dark storage still advised for long-term keeping |
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.
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.
DHA (dihydroxyacetone, also known as glycerone) is not a dye, stain or paint, but causes a chemical reaction with the amino acids in the dead layer on the skin surface. One of the pathways is a free radical-mediated Maillard reaction. The other pathway is the conventional Maillard reaction, a process well known to food chemists that causes the browning that occurs during food manufacturing and storage. It does not involve the underlying skin pigmentation nor does it require exposure to ultraviolet light to initiate the color change. However, for the 24 hours after self-tanner is applied, the skin is especially susceptible to ultraviolet, according to a 2007 study led by Katinka Jung of the Gematria Test Lab in Berlin. Forty minutes after the researchers treated skin samples with high levels of DHA they found that more than 180 percent additional free radicals formed during sun exposure compared with untreated skin. Another self-tanner ingredient, erythrulose, produced a similar response at high levels. For a day after self-tanner application, excessive sun exposure should be avoided and sunscreen should be worn outdoors, they say; an antioxidant cream could also minimize free radical production. Although some self-tanners contain sunscreen, its effect will not last long after application, and a fake tan itself will not protect the skin from UV exposure. The study by Jung et al. further confirms earlier results demonstrating that dihydroxyacetone in combination with dimethylisosorbide enhances the process of (sun-based) tanning.
While the band found success and critical acclaim, creative tensions were already developing. Giles and McDonald, still striving to cope with King Crimson's rapid success and the realities of touring life, became uneasy with their musical direction. Although he was neither the dominant composer nor the frontman, Fripp was very much the group's driving force and spokesman, leading them into progressively darker and more intense musical areas. McDonald and Giles, now favouring a lighter and more nuanced romantic style, became increasingly uncomfortable, and told Fripp they would be leaving the band upon the conclusion of the US tour. To keep the band together, Fripp offered to resign himself, but McDonald declared that King Crimson was "more (him) than them" and that he and Giles should therefore be the ones to leave. McDonald later said he "was probably not emotionally mature enough to handle it" and made a "rash decision to leave without consulting anyone". The original line-up played their last show at the Fillmore West in San Francisco on 14 December 1969, a little over one year after forming, with McDonald's and Giles's departures made official in January 1970. Live recordings of the band from 1969 were released in 1997 on Epitaph and in 2010 on the In the Court of the Crimson King (1969) box set. McDonald and Giles, as a spin-off duo from King Crimson, released a self-tiled album in 1971. Giles would go on to work as a session drummer, while McDonald would co-form Foreigner in 1976.
The etymology of the various words for tea reflects the history of transmission of tea drinking and trade from China. Nearly all of the words for tea worldwide fall into three broad groups: te, cha and chai, present in English as tea, cha or char, and chai. The earliest of the three to enter English is cha, which came in the 1590s via the Portuguese, who traded in Macao and picked up the Cantonese pronunciation of the word. The more common tea form arrived in the 17th century via the Dutch, who acquired it via trades from their colonial empire either indirectly from the Malay teh, or directly from the tê pronunciation in Min Chinese. The third form chai (meaning "spiced tea") originated from a northern Chinese pronunciation of cha, which travelled via the overland Silk Road to Central Asia and Persia, where it picked up a Persian ending yi. The Chinese word for tea itself was perhaps derived from the non-Sinitic languages of the botanical homeland of the tea plant in southwest China and northeastern Burma (modern-day Kachin and Shan), possibly from an archaic Austro-Asiatic root word *la, meaning "leaf".
Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspots. The dispersal of hydrothermal fluids throughout the global ocean at active vent sites creates hydrothermal plumes. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents. Hydrothermal vents exist because the Earth is both geologically active and has large amounts of water on its surface and within its crust. Under the sea, they may form features called black smokers or white smokers, which deliver a wide range of elements to the world's oceans, thus contributing to global marine biogeochemistry. Relative to the majority of the deep sea, the areas around hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic bacteria and archaea found around hydrothermal vents form the base of the food chain, supporting diverse organisms including giant tube worms, clams, limpets, and shrimp. Active hydrothermal vents are thought to exist on Jupiter's moon Europa and Saturn's moon Enceladus, and it is speculated that ancient hydrothermal vents once existed on Mars. Hydrothermal vents have been hypothesized to have been a significant factor to starting abiogenesis and the survival of primitive life. The conditions of these vents have been shown to support the synthesis of molecules important to life.
Driessen HP, de Jong WW, Tesser GI, Bloemendal H (1985). "The mechanism of N-terminal acetylation of proteins". CRC Crit. Rev. Biochem. 18 (4): 281–325. doi:10.3109/10409238509086784. PMID 3902358. Glembotski CC (1982). "Characterization of the peptide acetyltransferase activity in bovine and rat intermediate pituitaries responsible for the acetylation of beta-endorphin and alpha-melanotropin". J. Biol. Chem. 257 (17): 10501–9. doi:10.1016/S0021-9258(18)34046-8. PMID 6286657. O'Donohue TL (1983). "Identification of endorphin acetyltransferase in rat brain and pituitary gland". J. Biol. Chem. 258 (4): 2163–7. doi:10.1016/S0021-9258(18)32902-8. PMID 6296134. Tsunasawa S, Kamitani K, Narita K (February 1980). "Partial purification and properties of the amino-terminal amino acid-acetylating enzyme from hen's oviduct". J. Biochem. 87 (2): 645–50. doi:10.1093/oxfordjournals.jbchem.a132789. PMID 6244269.
Sources: en.wikipedia.org
Portugal has a literary tradition that predates the Portuguese language going back into the early 13th century. Portuguese literature developed through song as well as the written page known as cantigas. The cantigas drew practitioners from all social ranging from King Denis I to Martin Codax who was a minstrel. The earliest known work of literature produced by a Portuguese is the Ora faz ost'o senhor de Navarra, a cantiga de escárnio e maldizer written in Galician–Portuguese by João Soares de Paiva at around the year 1200. Portuguese literature developed under the influence of both European geopolitical developments and broader European literary traditions. The Hundred Years' War helped foster the development of Portuguese chronicles by Fernão Lopes, which constitute a valuable record of some of Europe's early encounters with peoples beyond the continent. European medieval chivalric literature, together with didactic religious literature transmitted through adaptations and partial translations, contributed to the development of Portuguese poetry in the translated works of Norman French Arturian narratives. Portuguese literature flourished during the Age of Discovery with writers such as Luís Vaz de Camões and António Ferreira. Modern Portuguese literature took shape through the work of Almeida Garrett, one of the founders of Portuguese Romanticism. Portugal has one Nobel Prize–winning author—José Saramago (1998).
Various authorities (e.g. ITIS 16, GRIN 27, WCSP, NCBI, DELTA) differ on the exact number of genera included in Liliaceae s.s., but generally there are about fifteen to sixteen genera, depending on whether or not Amana is included in Tulipa and Lloydia in Gagea. Currently the APWeb lists fifteen genera, arranged as shown in this table:
extein Any part of an amino acid sequence which is retained within a precursor polypeptide, i.e. not excised by post-translational protein splicing, and is therefore present in the mature protein, analogous to the exons of RNA transcripts. Contrast intein.
The earliest known reference to morphine can be traced back to Theophrastus in the 3rd century BC, however, possible references to morphine may go as far back as 2100 BC as Sumerian clay tablets which records lists of medical prescriptions including opium-based cures. An opium-based elixir has been ascribed to alchemists of Byzantine times, but the specific formula was lost during the Ottoman conquest of Constantinople (Istanbul). Around 1522, Paracelsus made reference to an opium-based elixir that he called laudanum from the Latin word laudāre, meaning "to praise". He described it as a potent painkiller but recommended that it be used sparingly. The recipe given differs substantially from that of modern-day laudanum. Morphine was discovered as the first active alkaloid extracted from the opium poppy plant in December 1804 in Paderborn by German pharmacist Friedrich Sertürner. Sertürner noticed the compound induced drowsiness in rats and stray dogs and he reported his findings in 1805. In 1817, Sertürner reported experiments in which he administered morphine to himself, three young boys, three dogs, and a mouse; all four people almost died. Sertürner originally named the substance morphium after the Greek god of dreams, Morpheus, as it has a tendency to cause sleep. Sertürner's morphium was six times stronger than opium. He hypothesized that, because lower doses of the drug were needed, it would be less addictive.
Blood is composed of a fluid portion, called plasma, and a cellular portion that contains red blood cells, white blood cells and platelets. The complete blood count evaluates the three cellular components of blood. Some medical conditions, such as anemia or thrombocytopenia, are defined by marked increases or decreases in blood cell counts. Changes in many organ systems may affect the blood, so CBC results are useful for investigating a wide range of conditions. Because of the amount of information it provides, the complete blood count is one of the most commonly performed medical laboratory tests. The CBC is often used to screen for diseases as part of a medical assessment. It is also called for when a healthcare provider suspects a person has a disease that affects blood cells, such as an infection, a bleeding disorder, or some cancers. People who have been diagnosed with disorders that may cause abnormal CBC results or who are receiving treatments that can affect blood cell counts may have a regular CBC performed to monitor their health, and the test is often performed each day on people who are hospitalized. The results may indicate a need for a blood or platelet transfusion. The complete blood count has specific applications in many medical specialties. It is often performed before a person undergoes surgery to detect anemia, ensure that platelet levels are sufficient, and screen for infection, as well as after surgery, so that blood loss can be monitored.
Sources: en.wikipedia.org
Divide it into single-use aliquots and hold them frozen at -20 °C or below, protected from light. Repeated thawing of one container is the main avoidable source of variability.
Mass spectrometry confirms identity, because the measured mass is compared with the value expected from the sequence. Chromatography mainly reports how much of the material elutes as the target peak.
It usually describes the share of the chromatographic peak area recorded at a set wavelength. Salts, residual water, and solvent are excluded from that number, so it is not the same as mass fraction.
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.