A practical reference on prohibited list: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-03-22. Anything still debated is marked as such rather than presented as settled.
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.
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.
| 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 |
Laboratory work on thymosin beta-4 describes binding to monomeric actin and effects on cell migration, angiogenesis, and inflammatory signaling in cultured cells. Animal models have examined skin, corneal, and cardiac repair after injury, with outcomes reported mainly in preclinical literature. Most of that evidence concerns the parent protein rather than preparations labelled TB-500, so extrapolation from animal findings to a specific commercial product remains uncertain. Whether the two behave identically in living systems has not been established in controlled human studies.
No major regulatory agency has approved TB-500 for therapeutic use, and it holds no pharmacopoeial monograph. The name appears on the World Anti-Doping Agency prohibited list within the class covering peptide hormones, growth factors, and related substances. Detection in doping control relies on mass spectrometric methods applied to urine, often after preparation steps that concentrate the analyte. Discussion of TB-500 therefore clusters in biochemistry, sports medicine, and anti-doping literature rather than in registered clinical trials.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
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.
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.
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.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
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.
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.
Eoox = −Eored The oxidation potential is a measure of the tendency of the reducing agent to be oxidized but does not represent the physical potential at an electrode. With this notation, the cell voltage equation is written with a plus sign
=== Parkinson's === Similar to Alzheimer's, Parkinson's is the most common neurodegenerative disease associated with balance and coordination issues, muscle stiffness, and tremors. During the early 1800s, James Parkinson medically defined this disease. A study observed improvement in locomotor abilities in rats with Parkinson's after intranasal delivery of conjugated mitochondrial systems. Another study demonstrated delivery of neuroactive drugs in a hydrogel increased residence times in the nasal cavity and concentration in the brain. Administering therapeutics combined with nanocarriers is shown to directly transfer drugs to the target cells and enhance accumulation. The observed effects include improved neuronal signaling and locomotion. Furthermore, intranasal delivery of biodegradable nanoparticles surface-modified with lactoferrin increase accumulation in the brain and cellular uptake.
Composition C-4 exists in the U.S. Army Hazardous Components Safety Data Sheet on sheet number 00077. Impact tests done by the U.S. military indicate composition C-4 is less sensitive than composition C-3 and is fairly insensitive. The insensitivity is attributed to using a large amount of binder in its composition. A series of shots were fired at vials containing C-4 in a test referred to as "the rifle bullet test". Only 20% of the vials burned, and none exploded. While C-4 passed the Army's bullet impact and fragment impact tests at ambient temperature, it failed the shock stimulus, sympathetic detonation and shaped charge jet tests. Additional tests were done including the "pendulum friction test", which measured a five-second explosion temperature of 263 °C to 290 °C. The minimum initiating charge required is 0.2 grams of lead azide or 0.1 grams of tetryl. The results of 100 °C heat test are: 0.13% loss in the first 48 hours, no loss in the second 48 hours, and no explosions in 100 hours. The vacuum stability test at 100 °C yields 0.2 cubic centimeters of gas in 40 hours. Composition C-4 is essentially nonhygroscopic. The shock sensitivity of C-4 is related to the size of the nitramine particles. The finer they are the better they help to absorb and suppress shock.
Sources: en.wikipedia.org
== Separation process and principle == The separation of compounds is due to the differences in their attraction to the stationary phase and because of differences in solubility in the solvent. Different compounds in the sample mixture travel at different rates due to the differences in their partition coefficients. Different solvents, or different solvent mixtures, give different separations. The retardation factor (RF) quantifies the results. It is the distance traveled by a given substance divided by the distance traveled by the mobile phase.
To model schizophrenia, animals were injected with phencyclidine (PCP) and, therefore, exhibited symptoms of the disorder, such as social withdrawal and motor responses. Upon injection with ZJ43, these behaviors were decreased, suggesting that an increase in NAAG in the synapse — and its subsequent activation of mGluR3 receptors — has potential as a co-therapy for schizophrenia. In these cases, NAAG peptidase inhibition reduces the adverse effects in these disorders. Future research focuses on the role of NAAG in pain perception, brain injury, and schizophrenia while developing NAAG peptidase inhibitors with even greater ability to cross the blood–brain barrier.[16][17]
The isotope pattern in the spectrum, which is unique for elements that have many natural isotopes, can also be used to identify the various elements present. Once a chemical formula has been matched to the spectrum, the molecular structure and bonding can be identified, and must be consistent with the characteristics recorded by GC–MS. Typically, this identification is done automatically by programs which come with the instrument, given a list of the elements which could be present in the sample. A "full spectrum" analysis considers all the "peaks" within a spectrum. Conversely, selective ion monitoring (SIM) only monitors selected ions associated with a specific substance. This is done on the assumption that at a given retention time, a set of ions is characteristic of a certain compound. This is a fast and efficient analysis, especially if the analyst has previous information about a sample or is only looking for a few specific substances. When the amount of information collected about the ions in a given gas chromatographic peak decreases, the sensitivity of the analysis increases. So, SIM analysis allows for a smaller quantity of a compound to be detected and measured, but the degree of certainty about the identity of that compound is reduced.
==== Hydrogels ==== Hydrogels have a high water content, with some hydrogels containing up to 90% water. Active drugs and other substances dispersed as colloids or dissolved in water can be easily taken up by hydrogels. Hydrogels are biocompatible. They also swell to a greater volume than organogels when in contact with water and other natural liquids. Hydrogels can be used as drug delivery vehicles, for transdermal application, ophthalmic drug delivery, cancer treatment or for wound dressing. As a type of water based formulation, hydrogels are generally less greasy and are easier to be removed than oil-based formulations like organogels. Examples of hydrogels include [[aluminium hydroxide|aluminum hydroxide]] gels and [[bentonite magma]].
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.
Desiccated storage at −20 °C is conventional, with −80 °C for extended periods. Vials should be warmed to room temperature before opening to prevent condensation on the powder.