A practical reference on heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-06-16 and is reviewed periodically as new material appears.
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.
Discussion of the compound frequently appears alongside other short peptides described as fragments of larger proteins. That grouping is convenient but can be misleading, because fragment length, charge, and modification state determine how a peptide behaves in solution and in any experimental system. A seven-residue acetylated peptide and a full-length protein differ in mass by roughly an order of magnitude, and they cannot be assumed to share distribution or binding properties. Precision about which molecule is under discussion is the single most useful step when reading such material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Reported sequence | Ac-LKKTETQ | Described in most listings as the actin-binding region of thymosin beta-4 |
| Reported molecular weight | Approximately 889 Da | Value shifts with the stated sequence; compare against the certificate of analysis |
| Parent protein length | 43 amino acids | Thymosin beta-4; the fragment covers only a small part of it |
| Common synonyms | TB4 fragment; thymosin beta-4 fragment | Trade-style names rather than formal nomenclature |
| Formal monographs | Not established | Labeling conventions differ by supplier and region |
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.
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 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.
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.
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.
=== Distribution === The drug is distributed rapidly and widely to most tissues and fluids, including sputum, pleural fluid, peritoneal fluid, interstitial fluid, bile, aqueous humor, reproductive organs, and bone; highest concentrations occur in pleural fluid, interstitial fluid, peritoneal fluid, and reproductive organs; low concentrations occur in CSF; it crosses the placenta, and enters breast milk
==== Road to war ==== Liu Wenhui's 1990 biography asserts that conflict between the two Lius was almost inevitable. Due to the consolidation of power in Sichuan that had occurred over the 1920s, Liu Wenhui and Liu Xiang had become the two most powerful warlords in the province. Liu Wenhui's assumption of the governorship in 1929 had turned many smaller warlords against him. By controlling the lower reaches of the Yangtze and the Qutang Gorge, Liu Xiang held the geographic advantage over his uncle, having priority in purchasing weapons from abroad (which entered Sichuan through the Yangtze), and had built a navy of three gunboats by fitting merchant ships with iron hulls. This also meant that Liu Xiang could block weapons from reaching Liu Wenhui's upstream domains, an ability that he would use to his advantage. Liu Xiang was also reportedly under the sway of his Taoist mystic advisor, Liu Congyun, who had told him that he was destined to unite the province under his rule. Yet another supposed factor contributing to conflict was the interference of Chiang Kai-shek, who did not want either warlord to become too powerful. Most sources agree that Liu Wenhui's abortive attempt to acquire military aviation assets in 1931 was the spark that led him to conflict with his nephew. Official Chinese sources state that a shipment ordered by Liu of foreign aircraft components worth 2 million yuan was seized by Liu Xiang at the port of Wanxian in Chongqing, leading to heightened tensions between the two Lius.
skin wound healing and regeneration of other tissues such as bone (PDGF-BB) neutropenia myelodysplastic syndrome (MDS) leukemias aplastic anaemia bone marrow transplantation angiogenesis for cardiovascular diseases
Sources: en.wikipedia.org
=== Cardiac muscle sarcomeric contractile function === PKCε translocates to cardiac muscle sarcomeres and modulates contractility of the myocardium. PKCε binds RACK2 at Z-lines with an EC50 of 86 nM; PKCε also binds at costameres to syndecan-4. PKCε has been shown to bind F-actin in neurons, which modulates synaptic function and differentiation; however it is unknown whether PKCε binds sarcomeric actin in muscle cells. Sarcomeric proteins have been identified in PKCε signaling complexes, including actin, cTnT, tropomyosin, desmin, and myosin light chain-2; in mice expressing a constitutively-active PKCε, all sarcomeric proteins showed greater association with PKCε, and the cTnT, tropomyosin, desmin and myosin light chain-2 exhibited changes in post-translational modifications. PKCε binds and phosphorylates cardiac troponin I (cTnI) and cardiac troponin T (cTnT) in complex with troponin C (cTnC); phosphorylation on cTnI at residues Serine-43, Serine-45, and Threonine-144 cause depression of actomyosin S1 MgATPase function. These studies were further supported by those performed in isolated, skinned cardiac muscle fibers, showing that in vitro phosphorylation of cTnI by PKCε or Serine-43/45 mutation to Glutamate to mimic phosphorylation desensitized myofilaments to calcium and decreased maximal tension and filament sliding speed. Phosphorylation on cTnI at Serine-5/6 also showed this depressive effect. Further support was gained from in vivo studies in which mice expressing a mutant cTnI (Serine43/45Alanine) exhibited enhanced cardiac contractility.
==== School education ==== Positive psychology is beneficial to schools and students because it encourages individuals to strive to do their best, whereas scolding has the opposite effect. Clifton and Rath discussed research conducted by Dr. Elizabeth Hurlock in 1925, where fourth, fifth and sixth graders were either praised, criticized or ignored, based on their work on math problems. Praised students improved by 71%, those criticized improved by 19%, and students provided with no feedback improved a mere 5%. Praise seems an effective method of fostering improvement. According to Clifton and Rath ninety nine out of one hundred people prefer the influence of positive people. The benefits include: increased productivity, and contagious positive emotions, which assists one in working to the best of their abilities. Even a single negative person can ruin the entire positive vibe in an environment. Clifton and Rath cited 'positive emotions as an essential daily requirement for survival'. In 2008, in conjunction with the Positive Psychology Center at the University of Pennsylvania, a whole-of-school implementation of Positive Psychology was undertaken by Geelong Grammar School (Victoria, Australia). This involved training of teaching staff in the principles and skills of positive psychology. Ongoing support was provided by The Positive Psychology Center staff, who remained in-residence for the entire year. Staats, Hupp and Hagley (2008) used positive psychology to explore academic honesty.
=== Subdivision === Viola is a large genus that has traditionally been treated in sections. One of these was that of Gingins (1823), based on stigma morphology, with five sections (Nomimium, Dischidium, Chamaemelanium, Melanium, Leptidium). The extensive taxonomic studies of Wilhelm Becker, culminating in his 1925 conspectus, resulted in 14 sections and many infrasectional groups. The largest and most diverse, being section Viola, with 17 subsections. In addition to subsections, series were also described. Alternatively, some authors have preferred to subdivide the genus into subgenera. Subsequent treatments were by Gershoy (1934) and Clausen (1964), using subsections and series. These were all based on morphological characteristics. Subsequent studies using molecular phylogenetic methods, such as that of Ballard et al. (1998) have shown that many of these traditional divisions are not monophyletic, the problem being related to a high degree of hybridization. In particular section Nomimium was dismembered into several new sections and transferring part of it to section Viola. Section Viola s. lat. is represented by four sections, Viola sensu stricto, Plagiostigma s. str., Nosphinium sensu lato. and the V. spathulata group. In that analysis, the S American sections appear to be the basal groups, starting with Rubellium, then Leptidium. However, the exact phylogenetic relationships remain unresolved, as a consequence many different taxonomic nomenclatures are in use, including groupings referred to as Grex. Marcussen et al.
Sources: en.wikipedia.org
Most listings describe it as a short acetylated peptide with the sequence Ac-LKKTETQ, presented as a region of thymosin beta-4. The label is a trade-style name rather than a standardized chemical name, so the exact content of a given vial depends on the supplier.
No. Thymosin beta-4 is a protein of 43 amino acids, while TB-500 is described as a short fragment of it. The two differ in size, structure, and the range of interactions each can support.
Naming for research peptides is not centrally coordinated, so vendors set their own labels and specifications. Differences in stated sequence, molecular weight, or purity documentation usually trace back to those independent labeling choices.
The lyophilised powder is typically held at -20 C or lower in a dry, dark place. Reconstituted solutions are aliquoted and frozen to avoid repeated freeze-thaw cycles.