actin-binding motif comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-03-14. Numbers and descriptions here follow the published literature rather than marketing material.
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.
TB-500 refers to a synthetic peptide fragment derived from the actin-binding region of thymosin beta-4, a protein present in most mammalian cells. The full protein contains forty-three amino acids, while the commonly sold fragment is a much shorter acetylated sequence, often cited as LKKTETQ. The fragment retains part of the actin-binding motif but lacks the remainder of the parent protein. Material sold under this name is usually lyophilized powder intended for laboratory research, and it is not a finished pharmaceutical product.
Proposed activity centers on actin sequestration and on the movement of cells during repair processes. In cell culture and animal models, the fragment has been associated with migration, tube formation, and tissue remodeling. These observations are frequently described as preliminary, because most published work uses rodent or in vitro systems rather than controlled human trials. Whether the short fragment reproduces the effects of the full protein remains an open question, and the relationship between dose, route, and measured outcome is not well characterized.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Supplied as a lyophilised cake in sealed vials |
| Solubility class | Freely soluble in water | Polar and charged side chains dominate the sequence |
| Typical storage temperature | -20 °C or below | Dry and dark; a desiccant is often recommended |
| Identity confirmation | Mass spectrometry | Observed mass compared with the theoretical value |
| Common synonyms | Thymosin beta-4 fragment | Also written as T beta 4 fragment 17-23 |
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.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
=== Warfare and weapons === At RAF Bomber Command, Dyson and colleagues proposed removing two gun turrets from Avro Lancaster bombers, to cut the catastrophic losses due to German fighters in the Battle of Berlin. A Lancaster without turrets could fly 50 mph (80 km/h) faster and be much more manoeuvrable.
===== MeSH D08.811.520.241 – carbon-oxygen lyases (EC 4.2) ===== MeSH D08.811.520.241.225 – DNA-(apurinic or apyrimidinic site) lyase MeSH D08.811.520.241.300 – hydro-lyases MeSH D08.811.520.241.300.050 – aconitate hydratase MeSH D08.811.520.241.300.050.500 – iron regulatory protein 1 MeSH D08.811.520.241.300.050.750 – iron regulatory protein 2 MeSH D08.811.520.241.300.150 – carbonic anhydrases MeSH D08.811.520.241.300.150.100 – carbonic anhydrase i MeSH D08.811.520.241.300.150.200 – carbonic anhydrase ii MeSH D08.811.520.241.300.150.300 – carbonic anhydrase iii MeSH D08.811.520.241.300.150.400 – carbonic anhydrase iv MeSH D08.811.520.241.300.150.500 – carbonic anhydrase v MeSH D08.811.520.241.300.200 – cystathionine beta-synthase MeSH D08.811.520.241.300.250 – enoyl-coa hydratase MeSH D08.811.520.241.300.300 – fumarate hydratase MeSH D08.811.520.241.300.500 – phosphopyruvate hydratase MeSH D08.811.520.241.300.500.500 – tau-crystallins MeSH D08.811.520.241.300.550 – porphobilinogen synthase MeSH D08.811.520.241.300.600 – prephenate dehydratase MeSH D08.811.520.241.300.650 – propanediol dehydratase MeSH D08.811.520.241.300.850 – tryptophan synthase MeSH D08.811.520.241.300.900 – urocanate hydratase MeSH D08.811.520.241.300.950 – uroporphyrinogen iii synthetase MeSH D08.811.520.241.700 – polysaccharide-lyases MeSH D08.811.520.241.700.350 – chondroitinases and chondroitin lyases MeSH D08.811.520.241.700.350.500 – chondroitin lyases MeSH D08.811.520.241.700.350.500.500 – chondroitin abc lyase MeSH D08.811.520.241.700.512 – heparin lyase MeSH D08.811.520.241.700.675 – hyaluronoglucosaminidase
=== Pharmacodynamics === While specific studies on 1S-LSD are limited due to its recent introduction, it is presumed to share pharmacological properties with LSD and its analogues. These substances typically act as partial agonists at serotonin receptors, particularly the serotonin 5-HT2A receptor, which is responsible for their hallucinogenic effects. The addition of the trimethylsilyl group in 1S-LSD is thought to slightly alter its binding affinity and metabolic profile, although empirical data is still needed.
Sources: en.wikipedia.org
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Diazepam was detected in 26% of cases of people suspected of driving under the influence of drugs in Sweden, and its active metabolite nordazepam, was detected in 28% of cases. Other drugs, zolpidem, and zopiclone were also found in high numbers. Many drivers had blood levels far exceeding the therapeutic dose range, suggesting a high degree of potential for misuse of the drugs zolpidem, and zopiclone. In Northern Ireland, in cases where drugs were detected in samples from impaired drivers who were not impaired by alcohol, benzodiazepines were found in 87% of cases. Diazepam was the most commonly detected benzodiazepine.
Sources: en.wikipedia.org
No. Thymosin beta-4 is a 43-residue protein, while TB-500 matches only residues 17 to 23 of that chain. The two are related but differ in size, and a method that identifies one does not automatically identify the other.
It corresponds to the actin-binding region of thymosin beta-4. Commercial synthesis reproduces that seven-residue stretch, usually with an acetyl group on the N-terminus.
It is not authorised as a medicine in the United States or the European Union and is distributed as a research chemical. Labels consequently carry research-use-only statements rather than clinical indications.
TB-500 is a name used for a short synthetic peptide fragment taken from the actin-binding region of thymosin beta-4. Material sold under this label is usually a lyophilized powder supplied for laboratory research rather than a licensed medicine. The commonly cited sequence is LKKTETQ.