If you have been reading about freeze-dried powder and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-09-25. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilized powder | Typical form for short synthetic peptides |
| Solubility class | Freely soluble in water and aqueous buffer | Dissolution aided by gentle mixing, not vigorous shaking |
| Typical storage temperature | −20 °C, desiccated | −80 °C used for long-term holding |
| Common analytical method | Reverse-phase HPLC with UV detection near 214 nm | Identity confirmed separately by mass spectrometry |
| Common synonyms | Thymosin beta-4 fragment; TB4 fragment | Naming varies between suppliers and publications |
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.
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.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
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.
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.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
== Pharmacokinetics == The molecular weight, bioavailability, protein binding, elimination half-life, the time to achieve maximum plasma concentration and binding affinity are present in the table below.
== Commercial activities == Borchers co-founded MRM Proteomics Inc. in 2010 as a spin-off commercializing proteomics technology developed at the University of Victoria–Genome BC Proteomics Centre. He serves as a scientific advisor to the company and chairs its board of directors. MRM Proteomics commercializes targeted proteomics assay kits, marketed under the name PeptiQuant, applying the MRM-based quantitation methods developed in Borchers' academic laboratories, and is developing kits based on the SysQuan method. The company has since built a series of industry partnerships around this technology: it granted the lung cancer diagnostics firm Biodesix rights to use its iMALDI technology in blood-based diagnostic test development in 2018, and entered a co-marketing agreement with Agilent Technologies in 2022 to develop targeted proteomics assay kits for Agilent's mass spectrometry platforms. In 2023, a project led by Borchers with MRM Proteomics received $3.03 million through Genome Canada's Genomic Applications Partnership Program to develop "MutaQuant" mass spectrometry kits measuring the protein-level impact of around 1,000 known cancer mutations, to be commercialized by MRM Proteomics and Agilent. In addition to MRM Proteomics, Borchers co-founded Molecular You, a Vancouver-based company offering blood-based multi-omic health assessments, where he serves as chief lab analytics officer, and Creative Molecules, Inc.
About 60% of all casualties were civilians, who died as a result of disease, starvation, genocide (in particular, the Holocaust), and aerial bombing. The former Soviet Union and China suffered the most casualties. Estimates place deaths in the Soviet Union at around 23 million, while China suffered about 10 million. No country lost a greater portion of its population than Poland: approximately 5.6 million, or 16%, of its pre-war population of 34.8 million died. The Holocaust (which roughly means "burnt whole") was the deliberate and systematic murder of millions of Jews and other "unwanted" groups during World War II by the Nazi regime in Germany. Several differing views exist regarding whether it was intended to occur from the war's beginning or if the plans for it came about later. Regardless, persecution of Jews extended well before the war even started, such as during Kristallnacht (Night of Broken Glass). The Nazis used propaganda to great effect to stir up anti-Semitic feelings within ordinary Germans. After World War II, Europe was informally split into Western and Soviet spheres of influence. Western Europe later aligned as NATO, and Eastern Europe as the Warsaw Pact. There was a shift in power from Western Europe and the British Empire to the two new superpowers, the United States and the Soviet Union. These two rivals would later face off in the Cold War. In Asia, the defeat of Japan led to its democratization. China's civil war continued through and after the war, eventually resulting in the establishment of the People's Republic of China.
=== In genetic disorders === Many genetic disorders involve hereditary defects in receptor genes. Often, it is hard to determine whether the receptor is nonfunctional or the hormone is produced at decreased level; this gives rise to the "pseudo-hypo-" group of endocrine disorders, where there appears to be a decreased hormonal level while in fact it is the receptor that is not responding sufficiently to the hormone.
Sources: en.wikipedia.org
=== Intracellular receptors === Intracellular receptors exist freely in the cytoplasm, nucleus, or can be bound to organelles or membranes. For example, the presence of nuclear and mitochondrial receptors is well documented. The binding of a ligand to the intracellular receptor typically induces a response in the cell. Intracellular receptors often have a level of specificity, this allows the receptors to initiate certain responses when bound to a corresponding ligand. Intracellular receptors typically act on lipid soluble molecules. The receptors bind to a group of DNA binding proteins. Upon binding, the receptor-ligand complex translocates to the nucleus where they can alter patterns of gene expression. Steroid hormone receptors are found in the nucleus, cytosol, and also on the plasma membrane of target cells. They are generally intracellular receptors (typically cytoplasmic or nuclear) and initiate signal transduction for steroid hormones which lead to changes in gene expression over a time period of hours to days. The best studied steroid hormone receptors are members of the nuclear receptor subfamily 3 (NR3) that include receptors for estrogen (group NR3A) and 3-ketosteroids (group NR3C). In addition to nuclear receptors, several G protein-coupled receptors and ion channels act as cell surface receptors for certain steroid hormones.
Medical and dietary management using methimazole and Hill's y/d cat food will give hyperthyroid cats an average of 2 years before dying due to secondary conditions such as heart and kidney failure. Drugs used to help manage the symptoms of hyperthyroidism are methimazole and carbimazole. Drug therapy is the least expensive option, even though the drug must be administered daily for the remainder of the cat's life. Carbimazole is only available as a once-daily tablet. Methimazole is available as an oral solution, a tablet, and compounded as a topical gel that is applied using a finger cot to the hairless skin inside a cat's ear. Many cat owners find this gel a good option for cats that do not like being given pills. Radioiodine treatment, however, is not available in all areas, as this treatment requires nuclear radiological expertise and facilities that not only board the cat, but are specially equipped to manage the cat's urine, sweat, saliva, and stool, which are radioactive for several days after the treatment, usually for a total of 3 weeks (the cat spends the first week in total isolation and the next two weeks in close confinement). In the United States, the guidelines for radiation levels vary from state to state; some states such as Massachusetts allow hospitalization for as little as two days before the animal is sent home with care instructions.
=== Field artillery === M116 howitzer – Saw use into 1950s in its mountain and airborne artillery role Ordnance QF 25-pounder – Still saw active use till 1960s when they were relegated to non-combat roles. OTO Melara Mod 56 – Saw short service as L5 pack howitzer from 1960s to mid-1970s. L118 light gun – entered service in mid 1970s and today is main field artillery piece.
For services to War Pensions Committees. June Elizabeth Coleman. For services to the community in Bath. Allan Barratt Collins, General Assistant, Tesco, Sutton, Surrey. For services to Food Retailing. John Frederick Collis, Constable, Metropolitan Police. For services to the Police. Leonard Conaway. For services to the Community in Cumbria Allison Gardner Cook. For political and public service. Dorothy Mary Cooke. For services to the community in Leicester. Joseph John Cooke, Mayor's Office, Lincoln City Council. For services to Local Government. Kathleen Roberta Joyce Cooper. For services to the St. John Ambulance Brigade. Tony Corfield, National Co-ordinator, National Health and Safety Groups Council. For services to Health and Safety. Ronald Stanley Cornwell. For services to the community in Crawley, West Sussex. Mary Barbara Corrall, lately Senior Executive Officer, Her Majesty's Board of Customs and Excise Myrna Jean Corrie, Principal, Farm Secretarial Business, and President, Scottish Young Farmers' Association. For services to Farming. Colin Cotton. For services to the Royal Naval Sailing Association. Henry Cottrell, lately Butler, Dorneywood Trust. For services to Government Hospitality. Olwen Jessie Couldridge, Secretary, Park Primary School, Newham, London. For services to Education. Derek Coulthard, Senior Executive Officer, Department of Social Security. Roger Brian Courtney. For services to people who are homeless. Eileen Frances Coutts. For services to the Sea Cadet Corps in East London. Derrick Stanley Cox, Head Chef, Pembroke College, University of Oxford.
=== Lakes, reservoirs and waterfalls === Elan Valley Reservoirs Lake Vyrnwy Llangorse Lake Clywedog Reservoir Pistyll y Llyn – one of the highest waterfalls in Wales Pistyll Rhaeadr Water-breaks-its-neck – waterfall in Radnor Forest Waterfall Country – waterfalls on the upper tributaries of the River Neath
Sources: en.wikipedia.org
TB-500 is a trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.
Not necessarily. Some vendors use the name for the full 43-residue protein, while others apply it to a short actin-binding fragment or to a related tetrapeptide. The sequence should be confirmed from documentation rather than assumed from the label.
No thymosin beta-4 fragment holds marketing approval as a medicine in major jurisdictions. Material offered for sale is typically labelled for laboratory research only.
The leading proposal involves sequestration of monomeric actin, which would alter cytoskeletal turnover and cell movement. The actin-binding motif shared with the parent protein is central to that idea. Direct confirmation in whole organisms remains limited.