heptapeptide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-04-19 and is reviewed periodically as new material appears.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
TB-500 is a synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
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.
| Property | Value | Notes |
|---|---|---|
| Physical form | Lyophilised powder | Sealed vial; reconstituted before laboratory use |
| Appearance | White to off-white solid | Visual descriptor used on certificates of analysis |
| Solubility class | Water-soluble | Dissolves in water and aqueous buffers |
| Reported mass, fragment | Near 889 Da | Value depends on the stated sequence |
| Reported mass, parent protein | Near 4963 Da | 43-residue thymosin beta-4 |
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.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
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.
TB-500 is a shorthand label used in supplier catalogs and online discussion for a short synthetic peptide described as a fragment of thymosin beta-4. Most product listings present it as the N-terminally acetylated heptapeptide Ac-LKKTETQ, a sequence corresponding to the actin-binding region of the parent protein. The name is not a formal chemical designation and does not appear in standard nomenclature systems. Because labeling practices vary between vendors, two products sold under the same name may not contain the same molecule, and the stated sequence should be treated as a claim rather than a fixed definition.
Thymosin beta-4 is a naturally occurring protein of 43 amino acids found in most mammalian cells, where it binds actin monomers and influences filament dynamics. It was first isolated from thymus tissue in the early 1980s, and its actin-binding activity was later mapped to a short region near the N-terminus. The synthetic fragment sold as TB-500 was designed to reproduce that region rather than the full protein. Whether a short fragment reproduces the behavior of the intact molecule remains an open question, since the parent protein carries additional structural elements outside the binding region.
Published research on the intact protein is substantial, covering actin regulation, cell migration, and wound models. Research using the heptapeptide fragment specifically is far smaller, and much of the circulating material originates in supplier documentation rather than peer-reviewed reports. Where fragment studies do exist, they often employ different sequences, chain lengths, or terminal modifications, which complicates direct comparison across papers. Readers encountering claims about TB-500 should therefore separate evidence about thymosin beta-4 from evidence about the fragment itself.
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.
=== Lawsuit === In November 2012, GlaxoSmithKline was ordered by a Rennes appeals court to pay Frenchman Didier Jambart 197,000 euros ($255,824); Jambart had taken ropinirole from 2003 to 2010 and exhibited risky hypersexual behavior and gambled excessively until stopping the medication. This behavior displayed is characteristic of Dopamine Dysregulation Syndrome.
=== 1949 === January 5–8: The Council for Economic Mutual Assistance (Comecon) formed. March 8: The Élysée Accords recognize Vietnam as an associated state within the French Union. April 4: The North Atlantic Treaty Organization (NATO) is founded by Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom, and the United States, in order to resist Communist expansion. May 11: The Soviet blockade of Berlin ends with the re-opening of access routes to Berlin. The airlift continues until September, in case the Soviets re-establish the blockade. Brune argues, "Moscow realized the blockade had not been successful – it had drawn the Western powers closer together rather than dividing them. Finally, Western countermeasures had inflicted considerable damage on the economic life of East Germany and the other Soviet satellites." May 23: In Germany, the Bizone merges with the French zone of control to form the Federal Republic of Germany, with Bonn as its capital. June 14: The State of Vietnam is proclaimed. July 20: The 1948 Arab–Israeli War ends with an Israeli victory. As a result of the war, the Transjordanians annex the West Bank and Egypt occupies the Gaza Strip, turning it into the All-Palestine Protectorate. August 29: The Soviet Union tests its first atomic bomb. The test, known to Americans as Joe 1, succeeds, as the Soviet Union becomes the world's second nuclear power. September 13: The USSR vetoes the United Nations membership of Ceylon, Finland, Iceland, Italy, Jordan, and Portugal.
FHA-HUD policy guaranteed that pay lenders would be compensated in full for the mortgage of foreclosed homes and by creating a housing market dominated by mortgage bankers, the FHA incentivized mortgage bankers to drive desperate black families to low-income homeownership, allowing bankers to inflate their economic gains by cycling these black families through tax foreclosures. Therefore, this racist and predatory provision of low-income housing through FHA-HUD policy elucidates that federal government was an inevitable perpetrator of racial segregation within Detroit's housing market. Despite having access to mortgage loans, black Detroiters continued to be preyed upon by real estate bankers who earned tremendous profits from the inability of black Detroiters to keep up with the FHA-insured mortgage payments. For many black Detroiters, the dismissal of FHA redlining did not end the economic exploitation and residential segregation of black families at the hands of wealth-hungry bankers and lenders. Colorblind universalism within Detroit's housing market remained a far-fetched aspiration of Black families in their pursuit of homeownership as FHA-HUD policy failed to dismantle the segregative impulses of the real estate industry. Furthermore, the threat of racial integration in white communities facilitated the rise of neighborhood associations, which were coalitions of independent white homeowners that fervently protected homeownership rights through advocacy for residential segregation.
Sources: en.wikipedia.org
Folgers is an American brand of coffee produced and sold in the United States, with additional distribution in Asia, Canada and Mexico. It forms part of the food and beverage division of the J.M. Smucker Company. Folgers roasts its coffee in New Orleans.
=== Cross-linking immunoprecipitation (CLIP) === CLIP analyzes protein interactions with RNA by combining UV cross-linking and immunoprecipitation. CLIP-based techniques are able to map RNA binding protein binding sites of interest on a genome-wide scale. There are many CLIP-based methods including:
Mary Osborn and Klaus Weber wrote a classic paper in biochemistry on determination of the molecular weight of a protein via SDS polyacrylamide gel electrophoresis, published in 1969 in Journal of Biological Chemistry. They knew that in 1967 Shapiro, Vinuela, and Maisel had shown that electrophoresis of proteins along with Sodium Dodecyl Sulfate (SDS) in polyacrylamide gels (PAGE) could separate the tested polypeptide chains by molecular weight. To see if this method applied to proteins of various sizes and shapes, Osborn and Weber took 40 known proteins, including globular and filamentous proteins, analyzed them via SDS PAGE, and plotted the logarithms of their molecular weights against their electrophoretic mobilities. The results showed convincingly that "the good resolution and the fact that an estimate of the molecular weight can be obtained within a day, together with the small amount of protein needed, makes the method strongly competitive with others commonly employed." This method has been used extensively by biochemists in all kinds of studies involving protein purification and identification as part of the process.
Sources: en.wikipedia.org
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.
Naming for research peptides is not standardised, and suppliers sometimes apply the same label to different chain lengths. Certificates of analysis and mass data are the practical way to determine what a given lot contains.
The fragment commonly cited under this label is reported near 889 Da, and the parent protein near 4963 Da. Reported values shift with the exact sequence and with residual counter-ions or water in the sample.
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.