The short version of RP-HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-04-30. 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 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.
Full-length thymosin beta-4 consists of roughly forty-three amino acids and ranks among the more abundant small proteins in the cytoplasm. The fragment is much shorter, so it cannot reproduce every function attributed to the intact molecule. In cell culture, short actin-binding motifs can interfere with filament dynamics and cell movement, but such observations come from controlled experiments rather than from whole-animal work. Whether a truncated fragment produces the same effects as the parent protein remains an open question.
| 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 |
Identity and purity are checked with chromatographic and mass spectrometric methods. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities, while mass spectrometry confirms the expected molecular mass. A certificate of analysis may report a purity percentage, but the laboratory should still verify the material independently. Common quality concerns include truncated sequences, deamidation, oxidation, and residual solvents from synthesis. Because TB-500 is short, some impurities can differ from the target by only a few mass units.
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.
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.
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.
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.
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.
=== Based on evolutionary phylogeny === An up-to-date classification of protease evolutionary superfamilies is found in the MEROPS database. In this database, proteases are classified firstly by 'clan' (superfamily) based on structure, mechanism and catalytic residue order (e.g. the PA clan where P indicates a mixture of nucleophile families). Within each 'clan', proteases are classified into families based on sequence similarity (e.g. the S1 and C3 families within the PA clan). Each family may contain many hundreds of related proteases (e.g. trypsin, elastase, thrombin and streptogrisin within the S1 family). Currently more than 50 clans are known, each indicating an independent evolutionary origin of proteolysis.
=== Interface with connective tissue === The epithelial–connective tissue interface is relatively smooth, with fewer and shallower rete ridges than seen in masticatory mucosa. This smooth interface reduces mechanical stress and is consistent with its protected location within the sulcus. The underlying lamina propria contains a dense collagen network and a rich vascular supply that supports the rapid turnover of epithelial cells.
The sans-culottes ... campaigned for a more democratic constitution, price controls, harsh laws against political enemies, and economic legislation to assist the needy. They expressed their demands through petitions of the sections presented to the assemblies (the Legislative, and Convention) by the delegates. The sans-culottes had a third way of applying pressure to achieve their demands: the police and the courts received thousands of denunciations of traitors and supposed conspirators. The height of their influence spanned roughly from the original overthrow of the monarchy in 1792 to the Thermidorian Reaction in 1794. Throughout the revolution, the sans-culottes provided the principal support behind the more radical and anti-bourgeoisie factions of the Paris Commune, such as the Enragés and the Hébertists, and were led by populist revolutionaries such as Jacques Roux and Jacques Hébert.
Sources: en.wikipedia.org
=== Music === Doillon's love for music was enkindled by her father: "When my parents split, I discovered with Jacques, his taste for eclectic and a strange form of radicalness in music. He would say: 'sit down, shut up and listen to the music' while playing records from Chet Baker, Billie Holiday, Siouxsie and the Banshees, Patti Smith and Nick Drake." She often quotes Bob Dylan and Leonard Cohen, and mentions Lhasa, Lead Belly, Fiona Apple, Cat Power, Nina Simone, Tim Buckley and Bobbie Gentry as her influences. Doillon recorded with many musicians in New York and Paris during the 2000s before starting a solo career in 2010. Her genre has been described as haunted folk, and her voice has been described as "equal parts Marianne Faithfull, Nina Simone, Anohni and Joanna Newsom." She writes her songs on Canadian Guild guitars (D55) or the piano and performs on an Eko electric guitar.
==== 1.A α-type channels ==== 1.A.1 Voltage-gated ion channel superfamily 1.A.2 Inward-rectifier K+ channel family 1.A.3 Ryanodine-inositol-1,4,5-trisphosphate receptor Ca2+ channel family 1.A.4 Transient receptor potential Ca2+ channel family 1.A.5 Polycystin cation channel family 1.A.6 Epithelial Na+ channel family 1.A.7 ATP-gated P2X receptor cation channel family 1.A.8 Major intrinsic protein superfamily 1.A.9 Neurotransmitter receptor, Cys loop, ligand-gated ion channel family 1.A.10 Glutamate-gated ion channel family of neurotransmitter receptors 1.A.11 Ammonium channel transporter family 1.A.12 Intracellular chloride channel family 1.A.13 Epithelial chloride channel family 1.A.14 Testis-enhanced gene transfer family 1.A.15 Nonselective cation channel-2 family 1.A.16 Formate-nitrite transporter family 1.A.17 Calcium-dependent chloride channel family 1.A.18 Chloroplast envelope anion-channel-forming Tic110 family 1.A.19 Type A influenza virus matrix-2 channel family 1.A.20 BCL2/Adenovirus E1B-interacting protein 3 family 1.A.21 Bcl-2 family 1.A.22 Large-conductance mechanosensitive ion channel 1.A.23 Small-conductance mechanosensitive ion channel 1.A.24 Gap-junction-forming connexin family 1.A.25 Gap-junction-forming innexin family 1.A.26 Mg2+ transporter-E family 1.A.27 Phospholemman family 1.A.28 Urea transporter family 1.A.29 Urea/amide channel family 1.A.30 H+- or Na+-translocating bacterial MotAB flagellar motor/ExbBD outer-membrane transport energizer superfamily 1.A.31 Annexin family 1.A.32 Type B influenza virus NB channel family 1.A.33 Cation-channel-forming heat shock protein 70 family 1.A.34 Bacillus gap junction-like channel-forming complex family 1.A.35 CorA metal ion transporter family 1.A.36 Intracellular chloride channel family 1.A.37 CD20 Ca2+ channel family 1.A.38 Golgi pH regulator family 1.A.39 Type C influenza virus CM2 channel family 1.A.40 Human immunodeficiency virus type I Vpu channel family 1.A.41 Avian reovirus p10 Vvroporin family 1.A.42 HIV viral protein R family 1.A.43 Camphor resistance or fluoride exporter family 1.A.44 Pore-forming tail Tip pb2 protein of phage T5 family 1.A.45 Phage P22 injectisome family 1.A.46 Anion channel-forming bestrophin family 1.A.47 Nucleotide-sensitive anion-selective channel, ICln family 1.A.48 Anion channel Tweety family 1.A.49 Human coronavirus ns12.9 viroporin family 1.A.50 Phospholamban (Ca2+-channel and Ca2+-ATPase regulator) family 1.A.51 The Voltage-gated Proton Channel (VPC) Family 1.A.52 The Ca2+ Release-activated Ca2+ (CRAC) Channel (CRAC-C) Family 1.A.53 The Hepatitis C Virus P7 Viroporin Cation-selective Channel (HCV-P7) Family 1.A.54 The Presenilin ER Ca2+ Leak Channel (Presenilin) Family 1.A.55 The Synaptic Vesicle-Associated Ca2+ Channel, Flower (Flower) Family 1.A.56 The Copper Transporter (Ctr) Family 1.A.57 The Human SARS Coronavirus Viroporin (SARS-VP) 1.A.58 The Type B Influenza Virus Matrix Protein 2 (BM2-C) Family 1.A.59 The Bursal Disease Virus Pore-Forming Peptide, Pep46 (Pep46) Family 1.A.60 The Mammalian Reovirus Pre-forming Peptide, Mu-1 (Mu-1) Family 1.A.61 The Insect Nodavirus Channel-forming Chain F (Gamma-Peptide) Family 1.A.62 The Homotrimeric Cation Channel (TRIC) Family 1.A.63 The Ignicoccus Outer Membrane α-helical Porin (I-OMP Family 1.A.64 The Plasmolipin (Plasmolipin) Family 1.A.65 The Coronavirus Viroporin E Protein (Viroporin E) Family 1.A.66 The Pardaxin (Pardaxin) Family 1.A.67 The Membrane Mg2+ Transporter (MMgT) Family 1.A.68 The Viral Small Hydrophobic Viroporin (V-SH) Family 1.A.69 The Heteromeric Odorant Receptor Channel (HORC) Family 1.A.70 The Molecule Against Microbes A (MamA) Family 1.A.71 The Brain Acid-soluble Protein Channel (BASP1 Channel) Family 1.A.72 The Mer Superfamily 1.A.73 The Colicin Lysis Protein (CLP) Family 1.A.74 The Mitsugumin 23 (MG23) Family 1.A.75 The Mechanical Nociceptor, Piezo (Piezo) Family 1.A.76 The Magnesium Transporter1 (MagT1) Family 1.A.77 The Mg2+/Ca2+ Uniporter (MCU) Family 1.A.78 The K+-selective Channel in Endosomes and Lysosomes (KEL) Family 1.A.79 The Cholesterol Uptake Protein (ChUP) or Double Stranded RNA Uptake Family 1.A.80 The NS4a Viroporin (NS4a) Family 1.A.81 The Low Affinity Ca2+ Channel (LACC) Family 1.A.82 The Hair Cell Mechanotransduction Channel (HCMC) Family 1.A.83 The SV40 Virus Viroporin VP2 (SV40 VP2) Family 1.A.84 The Calcium Homeostasis Modulator Ca2+ Channel (CALHM-C) Family 1.A.85 The Poliovirus 2B Viroporin (2B Viroporin) Family 1.A.86 The Human Papilloma Virus type 16 (HPV16) L2 Viroporin (L2 Viroporin) Family 1.A.87 The Mechanosensitive Calcium Channel (MCA) Family 1.A.88 The Fungal Potassium Channel (F-Kch) Family 1.A.89 The Human Coronavirus 229E Viroporin (229E Viroporin) Family 1.A.90 The Human Metapneumovirus (HMPV) Viroporin (HMPV-Viroporin) Family 1.A.91 The Cytoadherence-linked Asexual Protein 3.2 of Plasmodium falciparum (Clag3) Family 1.A.92 The Reovirus Viroporin VP10 (RVP10) Family 1.A.93 The Bluetongue Virus Non-Structural Protein 3 Viroporin (NS3) Family 1.A.94 The Rotavirus Non-structural Glycoprotein 4 Viroporin (NSP4) Family 1.A.95 The Ephemerovirus Viroporin (EVVP) Family 1.A.96 The Human Polyoma Virus Viroporin (PVVP) Family 1.A.97 The Human Papillomavirus type 16 E5 Viroporin (HPV-E5) Family 1.A.98 Human T-Lymphotropic Virus 1 P13 protein (HTLV1-P13) Family 1.A.99 The Infectious Bronchitis Virus Envelope Small Membrane Protein E (IBV-E) Family 1.A.100 The Rhabdoviridae Putative Viroporin, U5 (RV-U5) Family 1.A.101 The Peroxisomal Pore-forming Pex11 (Pex11) Family 1.A.102 Influenza A viroporin PB1-F2 (PB1-F2) Family 1.A.103 The Simian Virus 5 (Parainfluenza Virus 5) SH (SV5-SH) Family 1.A.104 The Proposed Flagellar Biosynthesis Na+ Channel, FlaH (FlaH) Family 1.A.105 The Mixed Lineage Kinase Domain-like (MLKL) Family 1.A.106 The Calcium Load-activated Calcium Channel (CLAC) Family 1.A.107 The Pore-forming Globin (Globin) Family
== Other ACPAs and citrullinated targets in RA == Vimentin, fibrin, filaggrin, enolase and keratin are common citrullination targets. The list of proteins that undergo citrullination and make up the citrullinome continues to increase. The RA associated citrullinome has been reported to include targets from synovial fluid and tissue that range from proteases, receptors, and carrier proteins. These proteins are components of complement, proteolytic activity, cell recognition, endocytosis, and response to biotic stimuli amongst others. 14-3-3η (YWHAH) is also another synovial derived protein that has been reported as a citrullination target.
Portugal is a high-income country with an advanced economy that follows the Mediterranean model. The country's economic policy is framed by strategic guidelines called Major Options, which are subsequently implemented through the State Budget. Portugal has the EU's 14th-largest economy by nominal GDP and the 12th-largest economy by PPP-adjusted GDP. Its PPP-adjusted GDP per capita stood at to 81% of the EU average in 2025. As of 2024, Portugal's service sector contributed the most for its economic output followed the industrial sector and its primary sector. In 2025, Portugal unemployment rate was 5.8%. As of 2024, its poverty rate after social transfers was 15.4% of the population while in 2023, the at-risk-of-poverty rate before social transfers stood at 40.3%. The national debt of Portugal was estimated at 89.2% relative to GDP as of 2025. Portugal is part of the European single market which represents more than 450 million consumers. Portugal replaced the escudo with the euro in 2002. Its monetary policy is set by the European Central Bank. The country has been a part of the Eurozone since its inception. Portugal's central bank is the Banco de Portugal and it is part of the European System of Central Banks. In 2024, Portugal had a combined share of exports and imports that amounted to 90% of its total GDP. In February 2026, Portugal's main export markets were Spain at 26% and Germany at 13.9%. Its main exports are machinery and mechanical appliances, vehicles and other transportation equipment, base metals, and plastics.
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.
It is a synthetic peptide based on a short sequence near the start of thymosin beta-4. It is supplied as a research chemical rather than as a licensed pharmaceutical product.