This is a working overview of Ac-LKKTETQ, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-01 and is reviewed periodically as new material appears.
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.
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.
Identity and purity checks for peptide material typically combine reversed-phase high-performance liquid chromatography with mass measurement, since retention time alone cannot confirm a sequence. Mass measurement verifies the expected molecular mass within instrument tolerance, while chromatographic peak area provides a purity estimate. Anti-doping analysis of urine uses related but more sensitive workflows, sometimes after solid-phase extraction. For research material, batch documentation, certificate content, and independent testing are common points of scrutiny, because supply chains outside pharmaceutical regulation vary widely in the paperwork they provide.
| 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 |
Lyophilised material is stable for extended periods when kept dry and cold, and suppliers typically recommend storage well below freezing. Once dissolved, the peptide is handled at refrigeration temperatures and used within a short period, because peptide bonds and the acetylated terminus can be affected by repeated freeze-thaw cycles, proteases, or extreme pH. Bacteriostatic water and saline are both described as solvents, although preservatives can interfere with some analytical workflows. Reconstituted solutions are inspected for particulates before use.
Sports authorities classify the peptide as a prohibited substance, and it appears on the World Anti-Doping Agency list under peptide hormones, growth factors, and related substances. Racing jurisdictions for horses and dogs have issued separate restrictions, and several national bodies treat it as a controlled or prescription-only item. As a research chemical it is sold without a therapeutic indication, and labels usually state that the product is not for human or veterinary use. Regulatory treatment therefore varies by country.
Detection in biological matrices generally relies on liquid chromatography coupled with tandem mass spectrometry, because the peptide lacks a convenient ultraviolet chromophore beyond the amide backbone. Immunoassays have been described, but antibodies raised against the fragment can cross-react with the full-length protein or with unrelated peptides, so findings usually require confirmation by a second technique. Sample preparation typically involves protein precipitation followed by solid-phase extraction. Reported detection windows depend on dose, route, matrix, and instrument sensitivity.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
Thymosin beta-4 itself is a small, widely expressed protein that sequesters monomeric actin and participates in cell migration, angiogenesis, and tissue repair. Researchers have examined the shortened fragment as a possible mimic of some of these activities, reasoning that the actin-binding motif lies within the first few residues. Binding to monomeric actin has been observed in cell-free systems. Whether the fragment reproduces the broader effects of the full protein in living tissue remains an open question, and findings from animal models are frequently cited without a clear bridge to human physiology.
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
=== Category:EC 4.1 (carbon–carbon lyases) === Category:EC 4.1.1 Ornithine decarboxylase (EC 4.1.1.17) Uridine monophosphate synthetase (EC 4.1.1.23) Aromatic-L-amino-acid decarboxylase (EC 4.1.1.28) RubisCO (EC 4.1.1.39) Category:EC 4.1.2 Fructose-bisphosphate aldolase (EC 4.1.2.13)
=== Further manifestations of solvent hydrogen bonding === Increase in the melting point, boiling point, solubility, and viscosity of many compounds can be explained by the concept of hydrogen bonding. Negative azeotropy of mixtures of HF and water. The fact that ice is less dense than liquid water is due to a crystal structure stabilized by hydrogen bonds. Dramatically higher boiling points of NH3, H2O, and HF compared to the heavier analogues PH3, H2S, and HCl, where hydrogen-bonding is absent. Viscosity of anhydrous phosphoric acid and of glycerol. Dimer formation in carboxylic acids and hexamer formation in hydrogen fluoride, which occur even in the gas phase, resulting in gross deviations from the ideal gas law. Pentamer formation of water and alcohols in apolar solvents.
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance or separating the different components of a mixture. In preparative chromatography, GC can be used to prepare pure compounds from a mixture. Gas chromatography is also sometimes known as vapor-phase chromatography (VPC), or gas–liquid partition chromatography (GLPC). These alternative names, as well as their respective abbreviations, are frequently used in scientific literature. Gas chromatography is the process of separating compounds in a mixture by injecting a gaseous or liquid sample into a mobile phase, typically called the carrier gas, and passing the gas through a stationary phase. The mobile phase is usually an inert gas or an unreactive gas such as helium, argon, nitrogen or hydrogen. The stationary phase can be solid or liquid, although most GC systems today use a polymeric liquid stationary phase. The stationary phase is contained inside of a separation column. Today, most GC columns are fused silica capillaries with an inner diameter of 100–320 micrometres (0.0039–0.0126 in) and a length of 5–60 metres (16–197 ft). The GC column is located inside an oven where the temperature of the gas can be controlled and the effluent coming off the column is monitored by a suitable detector.
Sources: en.wikipedia.org
In her autobiography, Out of the Shadows, Anne Marie reflects on how when she asked why her mother had collected Charmaine — who was part-Pakistani, while Anne Marie was fully white — but not her, Fred callously replied: "She wouldn't want you, love. You're the wrong colour." Charmaine's body was initially stowed in the coal cellar of Midland Road until Fred was released from prison. He later buried her naked body in the yard close to the back door of the flat, and remained adamant that he had not dismembered her. A subsequent post-mortem suggested the body had been severed at the hip, but that this damage may have been caused by building work Fred conducted at the property in 1976. Several bones—particularly patellae, finger, wrist, toe and ankle bones—were missing from Charmaine's skeleton, leading to speculation that the missing parts had been retained as keepsakes. This trait would prove to be a distinctive finding in all the autopsies of the Wests' victims when they were exhumed in 1994.
=== Sources of toxicity === Diet – Liver is high in vitamin A. The liver of certain animals, including the polar bear, bearded seal, fish and walrus, are particularly toxic (see Liver (food) § Poisoning). It has been estimated that consumption of 500 grams (18 oz) of polar bear liver would result in an acute toxic dose for humans. Supplements – Dietary supplements can be toxic when taken above recommended dosages. Cod liver oil - According to the United States Department of Agriculture, a tablespoon (13.6 grams or 14.8 mL) of cod liver oil contains 4,080 μg of vitamin A. The tolerable upper intake level (UL) is 3000 μg/day for adults, 600 μg/day for children ages 1–3 years and 900 μg/day for children ages 4–8 years, so for all ages, but especially for young children, a tablespoon a day exceeds the UL.
== Epidemiology == MG occurs in all ethnic groups and both sexes. It most commonly affects women under 40 and people from 50 to 70 years old of either sex, but it has been known to occur at any age. Younger people rarely have thymoma. Prevalence in the United States is estimated at between 0.5 and 20.4 cases per 100,000, with an estimated 60,000 Americans affected. In the United Kingdom, an estimated 15 cases of MG occur per 100,000 people. The mortality rate of MG is around 5-9%.
1993/851) Value Added Tax (General) (Amendment) (No.3) Regulations 1993 (S.I. 1993/856) Social Security (Industrial Injuries and Adjudication) Regulations 1993 (S.I. 1993/861) Social Security (Industrial Injuries) (Prescribed Diseases) Amendment Regulations 1993 (S.I. 1993/862) Official Secrets (Prohibited Places) (Amendment) Order 1993 S.I. 1993/863) Devon and Cornwall Police (Amalgamation) (Amendment) Order 1993 (S.I. 1993/864) West Mercia Police (Amalgamation) (Amendment) Order 1993 (S.I. 1993/865) Sussex Police (Amalgamation) (Amendment) Order 1993 (S.I. 1993/866) Avon and Somerset Police (Amalgamation) (Amendment) Order 1993 (S.I. 1993/867) Thames Valley Police (Amalgamation) (Amendment) Order 1993 (S.I. 1993/868) South Wales Police (Amalgamation) (Amendment) Order 1993 (S.I. 1993/869) Education (Designated Institutions in Further and Higher Education) (Interpretation) (Amendment) Order 1993 (S.I. 1993/870) A13 Trunk Road (Newham, Barking and Dagenham, and Havering) (Speed Limits) Order 1988 (Variation) Order 1993 (S.I. 1993/871) Western Isles Islands Council (Lochmaddy) Water Order 1993 (S.I. 1993/872) Oil Related and Petrochemical Plants (Rateable Values) (Scotland) Order 1993 (S.I. 1993/873) Electricity Generators (Rateable Values) (Scotland) Order 1993 (S.I. 1993/874) Scottish Hydro-Electric plc. (Rateable Values) (Scotland) Order 1993 (S.I. 1993/875) Industrial and Freight Transport (Rateable Values) (Scotland) Order 1993 (S.I. 1993/876) Scottish Nuclear Limited (Rateable Values) (Scotland) Order 1993 (S.I. 1993/877) Scottish Power plc.
Sources: en.wikipedia.org
=== Synthesis === Mescaline was the first ever psychedelic drug synthesized by chemists. Ernst Späth's 1919 total synthesis started from 3,4,5-trimethoxybenzoyl chloride. Several approaches using different starting materials have been developed since, including the following:
Type I Group I (2 cysteines): IFNa, IFNd, IFNe Group II (4 cysteines): IFNb, IFNc, IFNf Type II: IFNg (gamma), IFNgrel/IGNgl (gamma-related, gamma-like) Type III is not known to exist in teleosts as of 2011. Type IV: IFNu (upsilon) Their receptors are (parenthesized are human ortholog-based nomenclature; there tends to be two because of the whole genome duplication, hence -1 and -2):
== Commercial sources == The world's supply of pure (mostly anhydrous) caffeine for adding to drinks, pharmaceuticals, and other products comes from two sources: industrial synthesis and decaffeination of natural sources. Despite the different production methods, the final products are chemically identical, as are their effects on the body. Research on synthetic caffeine supports that it has the same stimulating effects on the body as natural caffeine. Although many claim that natural caffeine is absorbed slower and therefore leads to a gentler caffeine crash, there is little scientific evidence supporting the notion. Nevertheless, a demand for natural caffeine to satisfy consumer perception has grown so large that the decaffeinated product may be now considered a byproduct for the production of caffeine. The global market exchanged 128,127 tons of anhydrous caffeine in 2022. Most of the world's synthetic caffeine is produced by Chinese pharmaceutical companies, but an exact breakdown of supply between synthetic and natural does not seem to be available. It is possible to distinguish between natural and synthetic caffeine using carbon-13-to-carbon-12 isotope ratios, as most of the carbon from synthetic caffeine comes from petroleum sources with a more "ancient" carbon isotope signature.
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.
Standard practice is a desiccated container at −20 °C, protected from light and kept sealed between uses. Letting the vial reach room temperature before opening reduces condensation on the powder. Repeated warming and cooling of the whole container is generally avoided.