Ac-SDKP is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-01-06. Numbers and descriptions here follow the published literature rather than marketing material.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
Regulatory status differs by country, but TB-500 is not an approved pharmaceutical in major jurisdictions. It is commonly sold as a research chemical for laboratory use, which places responsibility for identity and purity on the supplier and the laboratory. Published human data are limited, and most reports involve preclinical models or cell culture. Questions about whether the fragment mimics all actions of thymosin beta-4, and under which conditions, remain open. Independent verification of any material is therefore a practical requirement in research settings.
TB-500 is a synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Calculated for the acetylated heptapeptide |
| Molecular weight | ~889 Da | Monoisotopic mass approximately 889.0 Da |
| Amino acid sequence | Ac-LKKTETQ | N-terminal acetylated seven-residue peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Water-soluble | Peptides of this size generally dissolve in aqueous media |
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Lyophilized peptide powder is normally held desiccated at −20 °C, with −80 °C used for longer storage periods. Allowing a sealed vial to reach room temperature before opening is standard practice, because condensation forming on cold powder introduces moisture. Once dissolved, solutions are typically kept cold and shielded from light. Repeated freeze-thaw cycles are avoided because they encourage aggregation and gradual loss of material. These conventions are general to synthetic peptides rather than unique to any one sequence.
Purity and identity are separate measurements and are often confused. Reverse-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, reports the share of total peak area belonging to the target compound. Mass spectrometry by electrospray or matrix-assisted laser desorption then checks whether the observed mass matches the expected sequence. Neither measurement alone shows that a vial holds the intended peptide. Peptide content, meaning the fraction of vial mass that is genuine peptide rather than counter-ion, water or residual acid, is reported separately and is frequently lower than the stated purity figure.
The regulatory position is broadly consistent across major jurisdictions: no thymosin beta-4 fragment is an approved medicine, and laboratory material is commonly labelled as not intended for human consumption. Anti-doping rules in sport list thymosin beta-4 and its fragments among prohibited peptide hormones. Because these products travel through research-chemical channels rather than pharmaceutical supply chains, quality varies considerably between vendors. Independent testing of identity, purity and sterility is the only dependable check, and a certificate of analysis describes one batch rather than a supplier's whole catalogue.
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.
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.
Founded in 1896 by Fritz Hoffmann-La Roche, the company was known early on for producing various vitamin preparations and derivatives. In 1934, it became the first company to mass-produce synthetic vitamin C, under the brand name Redoxon. During the Second World War, Roche collaborated with the Nazi regime in Germany and used forced labour in its German and Polish-based factories. It also moved all its Jewish employees to the United States to save them from Nazi attention. In 1957, Hoffmann-La Roche introduced the class of tranquilizers known as benzodiazepines (with Valium and Rohypnol being the best known members). It manufactures and sells several cancer drugs and is a leader in this field. In 1956, the first antidepressant, iproniazid, was accidentally created during an experiment while synthesizing isoniazid. Originally, it had been intended to create a more efficient drug at combatting tuberculosis. Iproniazid, however, was revealed to have its own benefits; some people felt it made them feel happier. It was withdrawn from the market in the early 1960s due to toxic side-effects. In 1976, an accident at a chemical factory in Seveso, Italy, owned by a subsidiary of Roche, caused a large dioxin contamination. In 1982, the United States arm of the company acquired Biomedical Reference Laboratories for US$163.5 million. That company dated from the late 1960s, and was located in Burlington, North Carolina. That year Hoffmann-La Roche then merged it with all of its laboratories, and incorporated the merged company as Roche Biomedical Laboratories, Inc. in Burlington.
== Encoded split and pool synthesis == Although in the S&P synthesis a single compound forms on each bead its structure is not known. For this reason, encoding methods had been introduced to help to determine the identity of the compound contained in a selected bead. Encoding molecules are coupled to the beads in parallel with the coupling of the BBs. The structure of the encoding molecule has to be easier determined than that of the library member on the bead. Ohlmeyer et al. published a binary encoding method. They used mixtures of 18 tagging molecules that after cleaving them from the beads could be identified by Electron Capture Gas Chromatography. Nikolajev et al. applied peptide sequences for encoding Sarkar et al. described chiral oligomers of pentenoic amides (COPAs) that can be used to construct mass encoded OBOC libraries. Kerr et al. introduced an innovative kind of encoding. An orthogonally protected removable bifunctional linker was attached to the beads. One end of the linker was used to attach the non-natural BBs of the library while to the other end the encoding amino acid triplets were linked. One of the earliest and very successful encoding methods was introduced by Brenner and Lerner in 1992. They proposed to attach DNA oligomers to the beads for encoding their content. The method was implemented by Nielsen, Brenner, and Janda using the bifunctional linker of Kerr et al. to attach the encoding DNA oligomers. This made it possible to cleave down the compound with the DNA encoding oligomer attached to it.
=== As an ornamental plant === Live plants and seeds of the opium poppy are widely sold by seed companies and nurseries in most of the western world, including the United States. Poppies are sought after by gardeners for the vivid colour of the flowers, the hardiness and reliability of the poppy plants, the exotic chocolate-vegetal fragrance note of some cultivars, and the ease of growing the plants from purchased flats of seedlings or by direct sowing of the seed. Poppy seed pods are also sold for dried flower arrangements. Though "opium poppy and poppy straw" are listed in Schedule II of the United States' Controlled Substances Act, P. somniferum can be grown legally in the United States as a seed crop or as an ornamental plant. During the summer, opium poppies can be seen flowering in gardens throughout North America and Europe, and displays are found in many private plantings, as well as in public botanical and museum gardens such as United States Botanical Garden, Missouri Botanical Garden, and North Carolina Botanical Garden. Many countries grow the plants, and some rely heavily on the commercial production of the drug as a major source of income. As an additional source of profit, the seeds of the same plants are sold for use in foods, so the cultivation of the plant is a significant source of income. This international trade in seeds of P. somniferum was addressed by a UN resolution "to fight the international trade in illicit opium poppy seeds" on 28 July 1998.
Sources: en.wikipedia.org
Holistic wound assessment that includes periwound assessment. Elimination of factors causing moisture-associated skin damage. Maintaining optimal moisture balance over the wound and periwound: effective exudate management in heavily draining wounds as well as adequate hydration of dry wounds. Proper patient nutrition. Treatment of underlying conditions. Protection of periwound from damage, infection, and contaminants. Systemic treatment may include medication appropriate for the patient's condition. Local treatment may include wound care products that protect periwound and help maintain its healthy functionality, for example, moisture barriers (ointments, salves and films), topical corticosteroids, antiseptics and antifungal agents, as well as moisture balancing dressings, such as self-adaptive wound dressing.
=== 2007–2013: Repatriation === On June 29, 2009, Tim Hortons Inc. announced that, pending shareholder approval, the chain's operations would be reorganized under a new publicly traded company, also named "Tim Hortons Incorporated", incorporated under the Canada Business Corporations Act. The change was being made primarily for tax purposes. On September 28, 2009, Tim Hortons Inc. announced it had completed the reorganization of its corporate structure to become a Canadian public company. In November 2010, Tim Hortons extended Interac debit payment system acceptance to most of its stores. The company previously began accepting Interac in its stores in Western Canada in 2003 and, later, MasterCard and MasterCard PayPass across most of its stores in 2007. The company often indicated the delay of broader or wider electronic payment acceptance was to "ensure speed of service." In 2012, Tim Hortons began accepting Visa cards, and in 2013, began accepting American Express cards. In late 2013, Tim Hortons had "4,350 cafes across the world, out of which 3,500 are in Canada, 817 in the U.S. and 33 in the GCC. The Toronto Stock Exchange listed company recorded revenues of $794 million and net profit of $111 million in the September quarter."
Trump's second term foreign policy has been described as a mixture of both imperialist and expansionist policies. He engaged in a realist and isolationist "America First" foreign policy agenda. His administration favored hard power to achieve foreign policy goals, and dismantled or withdrew support from domestic and international organizations dedicated to advancing American soft power. The moves were described as ceding American global influence and creating a void filled by Russia and China. His relations with allies were transactional and ranged from indifference to hostility, and he threatened them with economic tariffs or annexation. He was described as taking the side of Russia in the Russian invasion of Ukraine, and overseeing a rupture of the post-1945 rules-based liberal international order and abandonment of multilateralism. Michael Klare wrote that containing the influence of China and preventing the rise of any rival power is the central foreign policy objective of the administration. Trump has attempted to deepen the U.S.-India partnership. Trump's administration saw large drops in global public opinion of the U.S. Countries like Canada, Germany, the U.K., Denmark, and Finland warned their citizens about traveling to the U.S.
== Occurrence == Obsidian is found near volcanoes in locations which have undergone rhyolitic eruptions. It can be found in Argentina, Armenia, Azerbaijan, Australia, Canada, Chile, Georgia, Ecuador, El Salvador, Greece, Guatemala, Hungary, Iceland, Indonesia, Italy, Japan, Kenya, Mexico, New Zealand, Papua New Guinea, Peru, Russia, Scotland, the Canary Islands, Turkey and the United States. Obsidian flows which are so large that they can be hiked on are found within the calderas of Newberry Volcano (Big Obsidian Flow, 700 acres) and Medicine Lake Volcano in the Cascade Range of western North America, and at Inyo Craters east of the Sierra Nevada in California. Yellowstone National Park has a mountainside containing obsidian located between Mammoth Hot Springs and the Norris Geyser Basin, and deposits can be found in many other western U.S. states including Arizona, Colorado, New Mexico, Texas, Utah, and Washington, Oregon and Idaho.
Sources: en.wikipedia.org
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.
No. Thymosin beta-4 is a 43-amino-acid protein, while TB-500 represents only a short N-terminal segment. The two should not be treated as interchangeable in experimental design.
It is often called a thymosin beta-4 fragment, Tβ4 fragment, or Ac-LKKTETQ. The name TB-500 is mainly a commercial or catalog label rather than a formal chemical name.
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.