This is a working overview of trifluoroacetate, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-03-21. Anything still debated is marked as such rather than presented as settled.
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.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
| Property | Value | Notes |
|---|---|---|
| Water content | Low in freshly lyophilised material | Rises after repeated opening of the same vial |
| Solution stability | Lower than powder stability | Frozen aliquots are preferred over repeated thawing |
| Purity assessment | Reversed-phase HPLC with UV detection | Peak-area percentage excludes salts and water |
| Salt form | Often the trifluoroacetate salt | Retained from acidic purification gradients |
| Light sensitivity | Not strongly photoreactive | Dark storage still advised for long-term keeping |
Interest in the peptide grew during the 2000s and 2010s, when studies of tendon and ligament injuries in horses reported changes in lesion size after treatment. Those reports circulated widely outside the scientific literature and shaped much of the current online discussion. Subsequent reviews noted inconsistent study design, small groups, and a shortage of independent replication. Popular descriptions often blur the line between the fragment, the complete protein, and unrelated growth factors, which complicates comparisons across sources.
TB-500 is a synthetic peptide whose sequence corresponds to a short fragment near the N-terminus of thymosin beta-4, a small protein present in most mammalian cells. The fragment is commonly cited as containing the actin-binding region of the parent molecule, which is why it appears in laboratory work on cell migration and tissue repair. Suppliers distribute it as a lyophilised powder intended for research use. Its identity is defined by amino acid sequence and by the presence of an acetyl group on the N-terminal residue.
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.
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.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
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.
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.
=== Synthesis === Neurotransmitters are generally synthesized in neurons and are made up of, or derived from, precursor molecules that are found abundantly in the cell. Classes of neurotransmitters include amino acids, monoamines, and peptides. Monoamines are synthesized by altering a single amino acid. For example, the precursor of serotonin is the amino acid tryptophan. Peptide neurotransmitters, or neuropeptides, are protein transmitters which are larger than the classical small-molecule neurotransmitters and are often released together to elicit a modulatory effect. Purine neurotransmitters, like ATP, are derived from nucleic acids. Metabolic products such as nitric oxide and carbon monoxide have also been reported to act like neurotransmitters.
In Albania, the World Headquarters of the Bektashi (Albanian: Kryegjyshata) divides the country into 6 different administrative districts (similar to Christian parishes and patriarchates), each of which is called a gjyshata.
=== Pilgrim Fathers === A meeting of the Pilgrim Fathers, prior to their sailing in the Mayflower, is said to have taken place on the High Street; many local names and much historical imagery reflect this, such as Mayflower House, Mayflower Morris Men, Mayflower Taxis, Mayflower School and Mayflower Hall. Sunnymede school's houses were called Mayflower, Pilgrim and Chantry. Christopher Martin, who was born in Great Burstead and later became a Billericay goods merchant and property owner, travelled on the Mayflower in 1620; he was the official ship's governor and purchasing agent, procuring ships supplies for the voyage. The Mayflower ship set sail once the Pilgrim Fathers had all boarded and set to meet the Speedwell in the English Channel; the Speedwell was sailing from the Netherlands. Unfortunately, the Speedwell developed leaks and so the ships headed for the Devon coast to repair her, but this proved impossible; the Mayflower eventually sailed from Plymouth without her. Four people from Billericay were on board, including Christopher Martin, his wife Mary Prowe, along with Solomon Prowe - her son from her first marriage - and John Langemore, the Martins' servant. All four pilgrims perished after their arrival at Cape Cod, Massachusetts. Martin died of fever on 8 January 1621 and his wife perished in Plymouth in the same year. Both Christopher and Mary are buried in the Cole Hill Burial ground in Plymouth. The unfortunate fate of the would-be pioneers did not deter other inhabitants of Billericay from setting sail for the New World.
A scavenger in chemistry is a chemical substance added to a mixture in order to remove or de-activate impurities and unwanted reaction products, for example oxygen, to make sure that they will not cause any unfavorable reactions. Their use is wide-ranged:
Sources: en.wikipedia.org
Mexico (south-eastern): Among the ancient Maya, Nicotiana was considered a sacred plant, closely associated with deities of earth and sky, and used for both visionary and therapeutic ends. The contemporary Tzeltal and Tzotzil Maya of Highland Chiapas (Mexico) are bearers of this ethnobotanical inheritance, preserving a rich and varied tradition of Nicotiana use and folklore. The entire tobacco plant is viewed as a primordial medicine and a powerful botanical "helper" or "protector". Depending on the condition to be treated, whole Nicotiana leaves are used alone or in combination with other herbs in the preparation of various medicinal plasters and teas. In its most common form, fresh or green leaves are ground with slaked lime to produce an intoxicating oral snuff that serves as both a protective and therapeutic agent. United States: Extract of N. tabacum is taken orally to treat tiredness, ward off diseases, and quiet fear. Tanzania: Leaves of Nicotiana tabacum are placed in the vagina to stimulate labor. Zimbabwe: Leaves or root of the plant are infused and taken by mouth for asthma and other respiratory problems. Leaves and roots are also rubbed against warts and wounds as ointment.
== Overdose == Gastric decontamination measures such as activated charcoal are sometimes recommended in cases of overdose. The symptoms are usually indicative of CNS depression (or conversely CNS stimulation in some) and excess anticholinergic side effects. The LD50 in mice is 123 mg/kg and 295 mg/kg in rats.
Fibroin presents a unique combination of properties rarely found in one material. It is strong and tough, dissolves and reconstitutes in water rather than aggressive solvents, and breaks down in the body over a period that can be lengthened or shortened as required. Once the sericin is removed, it provokes only a mild immune response. A single quantity of purified protein can therefore be shaped into many different forms, each suited to a particular use. Until the late 1990s, reliable methods for dissolving silk fibres and forming the resulting solution were not available, and most of the work after that has been based on them. Silk biomaterials are used in tissue engineering, drug delivery, wound care and bioelectronics, and a small number have reached clinical use. The factors limiting them are specific: the raw material varies from batch to batch, silk is difficult to sterilise without damaging the protein, and production is hard to scale.
=== Regime type and polarization === Hybrid regimes are more vulnerable to coups than very authoritarian states or democratic states. A 2021 study found that democratic regimes were not substantially more likely to experience coups. A 2015 study finds that terrorism is strongly associated with re-shuffling coups. A 2016 study finds that there is an ethnic component to coups: "When leaders attempt to build ethnic armies, or dismantle those created by their predecessors, they provoke violent resistance from military officers." Another 2016 study shows that protests increase the risk of coups, presumably because they ease coordination obstacles among coup plotters and make international actors less likely to punish coup leaders. A third 2016 study finds that coups become more likely in the wake of elections in autocracies when the results reveal electoral weakness for the incumbent autocrat. A fourth 2016 study finds that inequality between social classes increases the likelihood of coups. A fifth 2016 study finds no evidence that coups are contagious; one coup in a region does not make other coups in the region likely to follow. One study found that coups are more likely to occur in states with small populations, as there are smaller coordination problems for coup-plotters. In autocracies, the frequency of coups seems to be affected by the succession rules in place, with monarchies with a fixed succession rule being much less plagued by instability than less institutionalized autocracies.
=== No development reported === 4-Chlorokynurenine (4-CL-KYN; 7-CL-KYNA; AV-101) – ionotropic glutamate NMDA receptor antagonist and 3-hydroxyanthranilate oxidase inhibitor [146] α-Synuclein picobody (a-syn-pico) – positron-emission tomography (PET) enhancer – diagnosis [147] A-86929 – dopamine D1 receptor agonist [148] AB-4166 – microbiome modulator [149] ACI-12589 – positron-emission tomography (PET) enhancer – diagnosis [150] Affitope-PD03 (PD03; PD03A) – α-synuclein inhibitor and immunostimulant [151] ANPD-002 (ANPD002) – dopaminergic cell replacement [152] AP-472 – metabotropic glutamate mGlu4 receptor positive allosteric modulator [153] Aplindore (DAB-452; palindore; SLS-006; WAY-DAB 452) – dopamine D2 receptor agonist [154] Armesocarb (MLR-1019) – atypical dopamine reuptake inhibitor (DRI) [155] Atuzaginstat (COR-388) – peptide hydrolase inhibitor [156] ATV:aSyn (ATV:α-synuclein; ATV:αSyn) – α-synuclein inhibitor [157] Autologous adipose derived mesenchymal stem cells - Hope Biosciences – cell replacement [158] AZ-001 – undefined mechanism of action [159] Beperminogene perplasmid (AMG-0001; Collategene; hepatocyte growth factor gene therapy) – gene transference and hepatocyte growth factor (HGF) expression stimulant [160] BTRX-246040 (LY-2940094) – nociceptin receptor (NOP) antagonist [161] Cannabidiol/tetrahydrocannabinol (CBD/THC; CanChew; MedChew; THC/CBD) – cannabinoid CB1 and CB2 receptor agonist and other actions [162] Carbidopa/levodopa (WD-1603) – combination of carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) and levodopa (dopamine precursor) [163] Carbidopa/levodopa oral solution (EXN-32) – combination of carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) and levodopa (dopamine precursor) [164] Ciforadenant (CPI-444, V-81444) – adenosine A2A receptor antagonist CM-4612 (CM-ADHD; CM-AT; CM-PK) – enzyme replacement and modulator [165] Crisdesalazine (AAD-2004) – microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibitor [166] CTx-GBA1 – gene transference [167] Cu(II)ATSM (copper(II)-ATSM; Cu-ATSM) – neuron modulator [168] Debamestrocel (autologous bone marrow derived mesenchymal stem cell therapy; NurOwn) – dopaminergic cell replacement [169] DNL-201 – leucine-rich repeat kinase 2 (LRRK2) inhibitor [170] Dopamine intranasal – non-selective dopamine receptor agonist [171] DX-0308 (DX-308) – retinoic acid metabolism modulator [172] Emrusolmin (anle-138b; TEV-56286) – α-synuclein inhibitor and protein aggregation inhibitor [173] ESB-1609 – sphingosine-1-phosphate (S1P) receptor agonist [174] ESB-5070 – leucine-rich repeat kinase 2 (LRRK2) inhibitor [175] F-14413 – α2-adrenergic receptor inverse agonist [176] FB-101 (1ST-102) – Bcr-Abl tyrosine kinase inhibitor [177] Fibroblast growth factor 1 (FGF-1) – fibroblast growth factor stimulant and angiogenesis-inducing agent [178] GO-101 – gene transference [179] GT-02329 – β-glucocerebrosidase (GCase) activator and/or chaperone [180] ISC-hpNSC (human parthenogenetic neural stem cells) – dopaminergic cell replacement [181] Itanapraced (CHF-5074; CSP-1103) – γ-secretase modulator and non-steroidal anti-inflammatory drug (NSAID) derivative lacking cyclooxygenase (COX) inhibition [182] Levodopa deuterated (deuterium-containing levodopa; SD-1077) – dopamine precursor and indirect non-selective dopamine receptor agonist [183] Liatermin (BVF-014; GDNF; glial-derived neutrotrophic factor; r-metHuGDNF) – neuron stimulant [184] Lu-AE-04621 (Lu-AE04621) – dopamine receptor agonist (prodrug of Lu-AA40326) [185] Masupirdine (SUVN-502; SUVN502) – serotonin 5-HT6 receptor antagonist [186] Mesocarb (MLR-1017) – atypical dopamine reuptake inhibitor (DRI) [187] MTK-458 – protein-serine-threonine kinase stimulant [188] NPT-200-11 (NPT200-11; UCB-1332) – α-synuclein inhibitor [189] NPT-520-34 (NPT520-34) – 1-phosphatidylinositol 3 kinase modulator and other actions [190] ODM-104 – catechol O-methyltransferase (COMT) inhibitor [191] OP-101 (dendrimer N-acetylcysteine) – various actions [192] OP-501 – catechol O-methyltransferase (COMT) inhibitor [193] Ordopidine (ACR-325) – low-affinity dopamine D2 receptor antagonist and dopaminergic stabilizer [194] PD-04 (a-Syn-PD-04; Affitope PD-04; PD04) – peptide vaccine against α-synuclein [195] Rasagiline – monoamine oxidase B (MAO-B) inhibitor [196] Rasagiline transdermal patch (TPU-002RA) – monoamine oxidase B (MAO-B) inhibitor [197] Research programme: adenosine A2A/A1 selective antagonists - Domain Therapeutics/CleveXel Pharma (CVXL-0069; DT-1133; DT0926; FP-0692; FP-1133) – adenosine A1 receptor antagonists and adenosine A2A receptor antagonists [198] Research programme: catalytic antioxidants - Aeolus Pharmaceuticals (AEOL-10113; AEOL-11207) – antioxidants [199] Research programme: central nervous system therapeutics - Delpor – undefined mechanism of action [200] Research programme: cGAS/STING antagonists - IFM Due – nucleotidyltransferase inhibitors [201] Research programme: COMT inhibitors - Avalo Therapeutics (AVTX-406; CERC-425; CERC-406) – catechol O-methyltransferase (COMT) inhibitors [202] Research programme: dopamine D1 receptor agonists - Takeda – dopamine D1 receptor agonists [203] Research programme: exosome therapeutics - ArunA Biomedical – undefined mechanism of action [204] Research programme: GPCR modulators - Nxera Pharma – various actions [205] Research programme: KEAP1 inhibitors - Keapstone Therapeutics – Kelch-like ECH-associated protein 1 (KEAP1) inhibitors [206] Research programme: long-acting neuropsychiatric therapeutics - Teva (NP-201; NP-202; risperidone/ropinirole implants) – various actions [207] Research programme: LRRK2 inhibitor - GlaxoSmithKline – leucine-rich repeat kinase 2 (LRRK2) inhibitors [208] Research programme: LRRK2 inhibitors - Novartis – leucine-rich repeat kinase 2 (LRRK2) inhibitors [209] Research programme: neurodegenerative disorder gene therapies - Denali Therapeutics (AAV-LF2; CNS-directed AAV-based gene therapies) – gene transference [210] Research programme: neurodegenerative disorders therapeutics - BioArctic Neuroscience (AD-0802; AD-1502; AD-2203; AE-1501; BAN-2203; BAN-2502; BAN2401 back-up) – various actions [211] Research programme: neurodegenerative disorder therapeutics - Celgene Corporation/Evotec (BMSxxx) – cell replacements [212] Research programme: neurodegenerative disease therapeutics - ProteoTech (DP-68; DP-74; PD-61-W3; PeptiClere; PTI-19; PTI-51; PTI-51-CH3; Synuclere; TauPro) – various actions [213] Research programme: neurological disorders therapeutics - Gloriana therapeutics (ECB-PD; ECT-PD; Meteorin; Ns-G34; NsG-0301; NsG-33) – glial cell line-derived neurotrophic factor modulators [214] Research programme: Parkinson's disease therapeutics - Alectos Therapeutics – glucocerebrosidase 2 (GBA2) protein inhibitor [215] Research programme: Parkinson's disease therapies - Zymes (co-Q10; coenzyme Q10; ubidecarenone) – antioxidants [216] Research programme: Parkinson's disease therapy - AbbVie – dopamine D2 and D3 receptor agonists [217] Research programme: positive allosteric modulators - Proximagen – various actions [218] Research programme: protective autoimmunity enhancer - Proneuron Biotechnologies (PN-277) – immunomodulators [219] Research programme: protein phosphatase 2A modulators - Signum Biosciences (SIG-1012; SIG-1106) – protein phosphatase 2A (PP2A) modulator [220] Research programme: small molecule therapeutics - Amathus Therapeutics – mitochondrial protein stimulants [221] Research programme: small molecule therapeutics - Aranda Pharma/Tarrex Biopharma (ADA-308; ADA-409; Backup; MDA-308; MDA-409) – androgen receptor antagonists [222] Research programme: transmembrane protein 175 agonists - AbbVie/Caraway Therapeutics – TMEM175 stimulants [223] Rotigotine controlled release (SER-214) – non-selective dopamine receptor agonist and other actions [224] S-32504 – dopamine D2 and D3 receptor agonist [225] SAGE-324 (BIIB-124) – GABAA receptor positive allosteric modulator and neurosteroid [226] Saracatinib (AZD-0530) – Src-family kinase inhibitor [227] Selegiline transdermal (Emsam) – monoamine oxidase B (MAO-B) inhibitor and other actions [228] Seridopidine (ACR343; ACR-343) – dopamine receptor modulator and so-called "dopaminergic stabilizer" [229] SLS-004 (LV-dCas9-DNMT3A) – gene therapy and α-synuclein expression inhibitor [230] Sonlicromanol (KH-176) – prostaglandin-E synthase inhibitor and reactive oxygen species modulator [231] SPN-803 (SPN803) – undefined mechanism of action [232] STEL-101 (AMA-101; STL-101) – undefined mechanism of action [233] UB-312 – immunostimulant [234] YKP-10461 (SKL-PD; YKP10461) – monoamine oxidase B (MAO-B) inhibitor [235] YTX-7739 – stearoyl-CoA desaturase inhibitor [236] Xenon (NBTX-001) – ionotropic glutamate NMDA receptor antagonist [237]
Sources: en.wikipedia.org
Divide it into single-use aliquots and hold them frozen at -20 °C or below, protected from light. Repeated thawing of one container is the main avoidable source of variability.
Mass spectrometry confirms identity, because the measured mass is compared with the value expected from the sequence. Chromatography mainly reports how much of the material elutes as the target peak.
It usually describes the share of the chromatographic peak area recorded at a set wavelength. Salts, residual water, and solvent are excluded from that number, so it is not the same as mass fraction.
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.