TB-500 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.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | N-terminal fragment of thymosin beta-4 |
| Residue count | Seven | Sequence LKKTETQ |
| Approximate mass | 889 Da | Acetylated seven-residue peptide |
| Common synonyms | TB4 fragment, TB500 | Not identical to full-length TB4 |
| Reported activity | Actin binding | Observed mainly in cell-free systems |
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.
The regulatory position is broadly consistent across major jurisdictions: no thymosin beta-4 fragment is an approved medicine, and laboratory material is commonly labelled as not intended for human consumption. Anti-doping rules in sport list thymosin beta-4 and its fragments among prohibited peptide hormones. Because these products travel through research-chemical channels rather than pharmaceutical supply chains, quality varies considerably between vendors. Independent testing of identity, purity and sterility is the only dependable check, and a certificate of analysis describes one batch rather than a supplier's whole catalogue.
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
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.
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.
Normally, when an item is quenched, the final temperature is ambient. The only reason for this is that most heat treaters do not have cooling equipment. There is nothing metallurgically significant about ambient temperature. The cryogenic process continues this action from ambient temperature down to −320 °F (140 °R; 78 K; −196 °C). In most instances the cryogenic cycle is followed by a heat tempering procedure. As all alloys do not have the same chemical constituents, the tempering procedure varies according to the material's chemical composition, thermal history and/or a tool's particular service application. The entire process takes 3–4 days.
Due to its success in livestock operations cryobranding has attracted the attention of humans in pursuit of novel body modifications. It remains a rare practice, with many instances carried out in an amateur setting. Most report pain, edema and sloughing of skin. Branding times vary but most are strongly overbranded, perhaps due a naive assumption that human skin requires the same brand durations as those of cattle and horses. Branding times up to 30 seconds have been recorded, although even 10 seconds have proved sufficient to produce a third degree cryoburn. This instance of a 10-second freeze brand formed the basis of the first medical report on a case of human cryobranding. The case involved a 33-year-old woman who received a large runic cryobrand to her inner forearm. The brand was cooled in a dry ice isopropanol bath for 5 minutes and then applied to her hairless skin for 10 seconds. The woman developed a third degree burn at the center of the imprint and sought medical attention 18 days after being branded. Her wound was treated with the same protocol for thermal burns and closed approximately 8 weeks after branding and 5 weeks after treatment began. At six months the final brand was somewhat hyperpigmented, with a central scar from the open wound. The mild steel branding iron used in this case bore a combination of two vowels from the Elder Futhark alphabet, an ᛁ superimposed on a ᛟ (equivalent to the English vowels i and o). Ranchers strongly advise that a gap be left in a brand face where the pattern has crossing lines.
Glucagon binds to the glucagon receptor, a G protein-coupled receptor, located in the plasma membrane of the cell. The conformation change in the receptor activates a G protein, a heterotrimeric protein with αs, β, and γ subunits. When the G protein interacts with the receptor, it undergoes a conformational change that results in the replacement of the GDP molecule that was bound to the α subunit with a GTP molecule. This substitution results in the releasing of the α subunit from the β and γ subunits. The alpha subunit specifically activates the next enzyme in the cascade, adenylate cyclase.
=== Elevated levels === Hyperprolactinaemia, or excess serum prolactin, is associated with hypoestrogenism, anovulatory infertility, oligomenorrhoea, amenorrhoea, unexpected lactation and loss of libido in women and erectile dysfunction and loss of libido in men. Causes of Elevated Prolactin Levels
=== Alphabet methods === A special class of protein structural alignment programs convert the input structure into a sequence of letters describing the structure. This allows methods from sequence alignment to be translated into this field to enable more efficient searching, and in some implementations, to also align and superimpose in real 3D space.
Sources: en.wikipedia.org
== References == (in French) Michel de Boüard, History of Normandy, Toulouse, 2001, ISBN 2-7089-1707-2 (in French) Pierre Gras, The Time of Ports, Decline and Recovery of Port Cities (1940–2010), Tallandier, 2010, 298 pages, ISBN 978-2-84734-675-6 (in French) Claire Étienne-Steiner, Le Havre. City, Port, and Agglomeration, Connaissance du patrimoine de Haute-Normandie, Rouen, 1999, ISBN 2-910316-19-X
== Early career == Shambhu Nath De was born in Hooghly District, West Bengal, India. His father Mr Dasarathi De was a not so successful businessman. Supported by his uncle Asutosh De, De completed the Matriculation examination with distinction from Garbati High School that helped him to get the District scholarship as well as to pursue further education in Hooghly Mohsin College, which was then affiliated with the prestigious University of Calcutta. His higher education was supported by Kestodhan Seth, who identified De as an extraordinary student. De passed his M.B. examination in 1939 from Calcutta Medical College and completed a Diploma in Tropical Medicine (DTM) in 1942. Soon after graduation he joined Calcutta Medical College as a Demonstrator of Pathology and initiated his research under Professor B. P. Tribedi. In 1947, De joined as a PhD student under Sir Roy Cameron at the Department of Morbid Anatomy, University College Hospital Medical School, London, and obtained his PhD degree in Pathology in 1949. After his return, De worked on pathogenesis of cholera and started publishing his findings. In 1955, De became the Head of Pathology and Bacteriology Division of the Calcutta Medical College, which he continued until his retirement. De published more than 30 research papers and has written an excellent monograph on cholera and its pathogenesis.
Early occupational studies revealed elevated levels of fluorochemicals, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), in the blood of exposed industrial workers, but cited no ill health effects. From 2005 to 2013, three epidemiologists known as the C8 Science Panel conducted health studies as part of a contingency to a class action lawsuit brought by communities in the Ohio River Valley against DuPont. Based on PFOA blood serum concentrations in 69,000 individuals from around DuPont's Washington Works Plant in Parkersburg, West Virginia, this panel reported probable links between elevated PFOA blood concentration and high cholesterol, ulcerative colitis, thyroid disease, testicular cancer, kidney cancer, delayed puberty onset, and pregnancy induced hypertension and preeclampsia. The findings on thyroid disease and ulcerative colitis have since been supported by further studies. The severity of suspected PFAS-associated health effects can vary based on the length of exposure, level of exposure, and health status. Infants may be exposed to PFAS both gestationally and by transfer from mother to child via breastfeeding. Children and infants may be particularly susceptible to PFAS contamination, with potential symptoms of abnormally small birth weight syndrome, preterm birth, one or more neurodevelopmental disorders, and decreased response to childhood vaccines. A study with a population of 2,525 adults from the US National Health and Nutrition Examination Survey (NHANES) reported hearing losses consistent with dose-response trends.
Sickle-cell anemia is caused by a point mutation in the β-globin chain of hemoglobin, causing the hydrophilic amino acid glutamic acid to be replaced with the hydrophobic amino acid valine at the sixth position. The β-globin gene is found on the short arm of chromosome 11. The association of two wild-type α-globin subunits with two mutant β-globin subunits forms hemoglobin S (HbS). Under low-oxygen conditions (being at high altitude, for example), the absence of a polar amino acid at position six of the β-globin chain promotes the non-covalent polymerisation (aggregation) of hemoglobin, which distorts red blood cells into a sickle shape and decreases their elasticity. Hemoglobin is a protein found in red blood cells, and is responsible for the transportation of oxygen through the body. There are two subunits that make up the hemoglobin protein: beta-globins and alpha-globins. Beta-hemoglobin is created from the genetic information on the HBB, or "hemoglobin, beta" gene found on chromosome 11p15.5. A single point mutation in this polypeptide chain, which is 147 amino acids long, results in the disease known as Sickle Cell Anemia. Sickle-cell anemia is an autosomal recessive disorder that affects 1 in 500 African Americans, and is one of the most common blood disorders in the United States. The single replacement of the sixth amino acid in the beta-globin, glutamic acid, with valine results in deformed red blood cells.
Sources: en.wikipedia.org
No. Thymosin beta-4 is a 43-residue protein, while TB-500 refers to a seven-residue fragment corresponding to its N-terminal region. The two names are often used loosely in commercial and community writing, which obscures the difference in size, sequence, and likely behavior.
The fragment contains an actin-binding motif, and cell-free experiments show that it can interact with monomeric actin. That observation is the basis for interest in cell migration and repair processes. Effects reported in animals are not established for humans.
Purity is usually stated by the supplier rather than fixed by a pharmacopoeial monograph, and typical listings report a percentage from reverse-phase HPLC. Independent verification is uncommon. Because no single accepted specification exists, comparisons between lots and between suppliers are difficult.
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.