A practical reference on Ac-SDKP: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilized powder | Typical form for short synthetic peptides |
| Solubility class | Freely soluble in water and aqueous buffer | Dissolution aided by gentle mixing, not vigorous shaking |
| Typical storage temperature | −20 °C, desiccated | −80 °C used for long-term holding |
| Common analytical method | Reverse-phase HPLC with UV detection near 214 nm | Identity confirmed separately by mass spectrometry |
| Common synonyms | Thymosin beta-4 fragment; TB4 fragment | Naming varies between suppliers and publications |
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 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.
Lyophilised peptide powders are hygroscopic, and the fragment absorbs atmospheric moisture when a vial is opened at room temperature. Weighing and aliquoting are normally done quickly in a dry environment, and stock solutions are divided into single-use portions before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and can shift the measured content of a vial. These practices are general to synthetic peptides rather than unique to this sequence, but they matter more for short chains kept for long periods.
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.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
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.
=== Incidental === Nanomaterials may be unintentionally produced as a byproduct of mechanical or industrial processes through combustion and vaporization. Sources of incidental nanoparticles include vehicle engine exhausts, smelting, welding fumes, combustion processes from domestic solid fuel heating and cooking. For instance, the class of nanomaterials called fullerenes are generated by burning gas, biomass, and candle. It can also be a byproduct of wear and corrosion products. Incidental atmospheric nanoparticles are often referred to as ultrafine particles, which are unintentionally produced during an intentional operation, and could contribute to air pollution.
Analogues of 4-HO-NiPT include 4-hydroxytryptamine (4-HT or 4-HO-T), 4-HO-MiPT (miprocin), 4-HO-DiPT (diprocin), psilocin (4-HO-DMT), norpsilocin (4-HO-NMT), 4-HO-NET, 4-HO-NPT, 4-HO-NALT, and 4-HO-NBnT, among others.
== History == The predecessor of LGD-4033, LG121071 (LGD-121071), was discovered by Ligand Pharmaceuticals and was first described in the literature in January 1999. It was the first orally active nonsteroidal androgen receptor agonist to be discovered. LG121071 is a tricyclic quinoline derivative, and is structurally distinct from arylpropionamide SARMs like andarine and enobosarm (ostarine). LGD-2226, a bicyclic quinoline SARM, was subsequently developed by Ligand Pharmaceuticals and TAP Pharmaceuticals in 2001. Other quinoline SARMs, like LGD-2941 and LGD-3303, were also subsequently developed by Ligand Pharmaceuticals prior to the development of LGD-4033. LGD-4033 was developed by Ligand Pharmaceuticals and was first described in the literature in 2010. On the basis of a favorable preclinical profile, phase 1 clinical trials of LGD-4033 began in 2009. The results of a single-dose phase 1 clinical trial were published as a conference abstract in 2010 and the findings of a multi-dose phase 1 trial were published as a journal article in 2013. A third phase 1 trial was also conducted. By 2012, a phase 2 trial of LGD-4033 for the treatment of muscle wasting related to cancer cachexia, acute rehabilitation (e.g., hip fracture), and acute illness was being prepared by Ligand Pharmaceuticals. On 22 May 2014, Viking Therapeutics licensed the developmental rights of LGD-4033 from Ligand Pharmaceuticals and intended to advance the compound into mid-to-late-stage clinical trials.
=== Lupron "flare" === During the initial phase of luteinizing hormone-releasing hormone (LHRH) agonist therapy in male patients, there is a notable phenomenon known as the "flare." This occurs when testosterone levels temporarily surge by approximately 50% within the first 1 to 2 weeks of therapy. This increase is a response to the initial stimulation of luteinizing hormone (LH) by the LHRH agonist, leading to a rise in testosterone levels before they begin to decrease as intended. For individuals receiving LHRH agonists as part of gender-affirming care, this temporary increase in testosterone can be particularly distressing, exacerbating gender dysphoria and discomfort. To manage and mitigate these effects, healthcare providers often prescribe antiandrogens during this phase to help block the unwanted increase in testosterone and alleviate the associated distress.
Muscle loss can be quantified with advanced imaging studies but this is not frequently pursued. Treatment depends on the underlying cause but will often include exercise and adequate nutrition. Anabolic agents may have some efficacy but are not often used due to side effects. There are multiple treatments and supplements under investigation but there are currently limited treatment options in clinical practice. Given the implications of muscle atrophy and limited treatment options, minimizing immobility is critical in injury or illness.
Sources: en.wikipedia.org
==== 1700–1799 ==== A249 Trunk Road (Brielle Way/Docks Entrance) Order 1993 (S.I. 1993/1700) Craigie College of Education (Closure) (Scotland) Order 1993 (S.I. 1993/1701) Supply of Razors and Razor Blades (Interim Provision) (Revocation) Order 1993 (S.I. 1993/1702) Merger Situation (Stora/Swedish Match/Gillette) (Interim Provision) (Revocation) Order 1993 (S.I. 1993/1703) Land Registration (Charities) Rules 1993 (S.I. 1993/1704) A65 Trunk Road (Gargrave Bypass) Order 1990 Amendment and New Trunk Road Order 1993 (S.I. 1993/1705) A65 Trunk Road (Horse Pasture Laithe to Heber Barn) (Detrunking) Order 1993 (S.I. 1993/1706) Removal and Disposal of Vehicles(Amendment) (No. 3) Regulations 1993 (S.I. 1993/1708) Inshore Fishing (Prohibition of Fishing for Cockles) (Scotland) Order 1993 (S.I. 1993/1709) Motor Vehicles (Designation of Approval Marks) (Amendment) Regulations 1993 (S.I. 1993/1710) Plant Breeders' Rights (Trees, Shrubs and Woody Climbers) (Variation) Scheme 1993 (S.I. 1993/1733) Beef Special Premium Regulations 1993 (S.I. 1993/1734) Reconstitution of the Upper Witham Internal Drainage Board Order 1993 (S.I. 1993/1738) Social Security (Introduction of Disability Living Allowance) (Amendment) (No.2) Regulations 1993 (S.I. 1993/1739) Kent and East Sussex (County Boundaries) Order 1993 (S.I. 1993/1742) Coal Industry (Restructuring Grants) Order 1993 (S.I. 1993/1745) Chemicals (Hazard Information and Packaging) Regulations 1993 (S.I. 1993/1746) A35 Trunk Road (Tolpuddle to Puddletown Bypass and Slip Roads) Order 1993 (S.I.
=== 68Ga radiolabeling === 68Ga-Trivehexin is a radioactive drug. The radioactive atom, gallium-68 (68Ga), decays with a half-life of approximately 68 min to the stable isotope zinc-68 (68Zn), to 89% by β+ decay whereby a positron with a maximum kinetic energy of 1.9 MeV is emitted (the remaining 11% are EC decays). Due to the short half-life, 68Ga-Trivehexin can not be manufactured long before use but the 68Ga has to be introduced into the molecule shortly before application. This process is referred to as radiolabeling, and is done by complexation of the trivalent cation 68GaIII by the TRAP chelator in Trivehexin. 68GaIII is usually obtained from a dedicated mobile radionuclide source, a Gallium-68 generator, in form of a solution in dilute (0.04–0.1 M) hydrochloric acid (frequently and imprecisely referred to as "68Ga chloride solution in HCl" despite it contains no species with a Ga–Cl bond but [68Ga(H2O)6]3+ complex hydrate cations). For radiolabeling, the pH of the 68Ga containing generator eluate has to be raised from its initial value (depending on HCl concentration, pH 1–1.5) to pH 2–3.5 using suitable buffers, such as sodium acetate. Then, Trivehexin (5–10 nmol) is added to the buffered 68Ga-containing solution, and the mixture is briefly heated to 50–100 °C (usually 2–3 min) to finalize the complexation reaction.
In 1808, Andrew Johnson, the United States' future 17th President, was born at Casso's Inn in Raleigh. The city's first water supply network was completed in 1818, although due to system failures, the project was abandoned. In 1817, the Episcopal Diocese of North Carolina was established and headquartered in Raleigh. In 1819, Raleigh's first volunteer fire company was founded, followed in 1821 by a full-time fire company. In 1831, a fire destroyed the North Carolina State House. Two years later, reconstruction began with quarried gneiss being delivered by the first railroad in the state. Raleigh celebrated the completion of the new State Capitol and new Raleigh & Gaston Railroad Company in 1840. The first State Fair was held near Raleigh in 1853. The first institution of higher learning in Raleigh, Peace College, was established in 1857. Raleigh's Historic Oakwood contains many houses from the 19th century that are still in good condition. North Carolina seceded from the Union during the American Civil War on May 20, 1861. After the war began, Governor Zebulon Baird Vance ordered the construction of breastworks around the city as protection from Union troops. The North Carolina State School for the Blind and Deaf, currently known as the Governor Morehead School, served as Raleigh's arsenal. Near the end of the Civil War, Governor Vance arranged his evacuation to avoid capture as Union General William Sherman's forces approached the city. Before leaving, Vance met with former governors Graham and Swain to draft a letter of surrender for Raleigh.
Working with E. R. Giblett in 1972, Ammann described the first patient with purine nucleoside phosphorylase deficiency in association with a unique genetic profile that included depressed T-cell immunity with normal levels of immunoglobulins. The resulting publication was listed as one of the 500 most widely cited articles in 1984. Ammann's discovery represented an essential step to understanding new treatments for immunodeficiency diseases and developing drugs that could interfere with the immune response.
=== Cathinones === Cathinones include some stimulants and entactogens, which are derivatives of cathinone. They feature a phenethylamine core with an alkyl group attached to the alpha carbon, and a ketone group attached to the beta carbon, along with additional substitutions.
Sources: en.wikipedia.org
== Dietary concentrations == Detailed reviews on occurrence of CoQ10 and dietary intake were published in 2010. Besides the endogenous synthesis within organisms, CoQ10 also is supplied by various foods. CoQ10 concentrations in various foods are:
== Fifth Ministry == On 16 December 1977, following the 1977 election on 12 November, the Ministry was reconstituted. Due to the death of Keith Hooper on 23 August 1977, there was a vacancy in the outgoing ministry, to which Charles Porter was appointed. A number of minor changes occurred:
=== Other organizations and programs === HOL LiNK program (Literacy and Numeracy Knowledge), by Hands On Learning Australia Liberty in North Korea (LiNK), a refugee resettling group Link Campus University, Rome, Italy LINKS units, later student volunteering units, of St John Ambulance in England and Wales Local involvement networks (LINks), National Health Service England Project LINK, a UN project to build global macroeconomic models The Link (UK organization) for "Anglo-German friendship", UK pro-Nazi organization, 1937–1939 The Links, a social and service organization of American Black women
Two Greeks submerged and surfaced in the river Tagus near the City of Toledo several times in the presence of The Holy Roman Emperor Charles V, without getting wet and with the flame they carried in their hands still alight. In 1578, the English mathematician William Bourne recorded in his book Inventions or Devises one of the first plans for an underwater navigation vehicle. A few years later the Scottish mathematician and theologian John Napier wrote in his Secret Inventions (1596) that "These inventions besides devises of sayling under water with divers other devises and strategems for harming of the enemyes by the Grace of God and worke of expert Craftsmen I hope to perform." It is unclear whether he carried out his idea. Jerónimo de Ayanz y Beaumont (1553–1613) created detailed designs for two types of air-renovated submersible vehicles. They were equipped with oars, autonomous floating snorkels worked by inner pumps, portholes and gloves used for the crew to manipulate underwater objects. Ayanaz planned to use them for warfare, using them to approach enemy ships undetected and set up timed gunpowder charges on their hulls. The first submersible of whose construction there exists reliable information was designed and built in 1620 by Cornelis Drebbel, a Dutchman in the service of James I of England. It was propelled by means of oars.
These drugs have been derived from NSAIDs. The cyclooxygenase enzyme inhibited by NSAIDs was discovered to have at least two different versions: COX-1 and COX-2. Research suggested most of the adverse effects of NSAdiated by blocking the COX-1 (constitutive) enzyme, with the analgesic effects being mediated by the COX-2 (inducible) enzyme. Thus, the COX-2 inhibitors were developed to inhibit only the COX-2 enzyme (traditional NSAIDs block both versions in general). These drugs (e.g., rofecoxib, celecoxib, and etoricoxib) are equally effective analgesics when compared with NSAIDs, but cause less gastrointestinal hemorrhage in particular. After widespread adoption of the COX-2 inhibitors, it was discovered that most of the drugs in this class increase the risk of cardiovascular events by 40% on average. This led to the withdrawal of rofecoxib and valdecoxib, and warnings on others. Etoricoxib seems relatively safe, with the risk of thrombotic events similar to that of non-coxib NSAID diclofenac.
Sources: en.wikipedia.org
TB-500 is a trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.
Not necessarily. Some vendors use the name for the full 43-residue protein, while others apply it to a short actin-binding fragment or to a related tetrapeptide. The sequence should be confirmed from documentation rather than assumed from the label.
No thymosin beta-4 fragment holds marketing approval as a medicine in major jurisdictions. Material offered for sale is typically labelled for laboratory research only.
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.