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 2026-02-04 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.
The compound circulates in the literature as a research reagent rather than an approved therapeutic. Regulatory agencies in several countries have not authorized it for medical use, and sporting bodies list related thymosin beta-4 peptides among prohibited substances. Suppliers typically market it with a purity figure and a certificate of analysis, while peer-reviewed clinical reports remain sparse. Discussions therefore often separate laboratory findings from anecdotal reports, and reviewers tend to note the small size and methodological limits of the available studies.
TB-500 refers to a synthetic peptide fragment derived from the actin-binding region of thymosin beta-4, a protein present in most mammalian cells. The full protein contains forty-three amino acids, while the commonly sold fragment is a much shorter acetylated sequence, often cited as LKKTETQ. The fragment retains part of the actin-binding motif but lacks the remainder of the parent protein. Material sold under this name is usually lyophilized powder intended for laboratory research, and it is not a finished pharmaceutical product.
| 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 |
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.
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.
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.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
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.
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.
Duterte's father, Vicente, died in 1968 while his mother, Soledad, died on February 4, 2012, at the age of 95. In 1973, Duterte married Elizabeth Zimmerman, a flight attendant of German American descent who traces her roots in Tuburan, Cebu. They have three children (from eldest to youngest): Paolo ("Pulong"), Sara ("Inday Sara") and Sebastian ("Baste"). In the 1990s, his son Paolo left the family for more than five years after having a son (Omar Vincent) with Lovelie Sangkola in 1994, which Duterte acknowledged to be "[o]ne of my sad events in my life". Sara and Paolo both entered politics in 2007 and 2008 respectively, while Baste, with no interest in politics, initially concentrated on business and surfing but eventually ran and won as vice mayor of Davao City in 2019. Sara was elected as Vice President in 2022. Duterte has been publicly open about his infidelity while married to Zimmerman and cited it as the reason for his failed marriage. According to newspaper columnist Ramon Tulfo, Duterte's various alleged partners included "a then agriculture undersecretary, a governor of a province, a local TV newscaster and a policewoman", with Duterte himself admitting in 2016 to having multiple girlfriends such as a cosmetics worker in a shopping mall and a cashier. In 1998, Zimmerman filed a petition in the Regional Trial Court of Pasig to nullify her marriage. Duterte never appeared in court and did not contest Zimmerman's petition. Two years later, the court decided in her favor, ending the 27-year marriage of Duterte and Zimmerman.
== Other projects == Hari is listed as a producer and writer on the 2021 film The United States vs. Billie Holiday. As of April 2018, Hari was working on a biography of American linguist and intellectual Noam Chomsky.
== Modifications == The threonine residue is susceptible to numerous posttranslational modifications. The hydroxyl side-chain can undergo O-linked glycosylation. In addition, threonine residues undergo phosphorylation through the action of a threonine kinase. In its phosphorylated form, it can be referred to as phosphothreonine. Phosphothreonine has three potential coordination sites (carboxyl, amine and phosphate group) and determination of the mode of coordination between phosphorylated ligands and metal ions occurring in an organism is important to explain the function of the phosphothreonine in biological processes.
==== Motion of censure against Betssy Chávez ==== On 26 May 2022, minister of labour Betssy Chávez was censured by the Congress of the Republic with 71 votes in favor, 28 against, and 12 abstentions. The opposition groups Fuerza Popular, RP, Avanza País, and APP motivated the censure by mentioning poor management of the ministry's actions and an air traffic controller strike in April 2022. During a previous motion for interpellation and convening of the minister on 12 May 2022, Betssy Chávez had answered questions from elected officials about this same strike. The minister's answers, according to right-wing parliamentarians, were not satisfactory. According to the minister, she was further censured for projects not mentioned on 12 May such as the reform of the draft Labor Code. This decision to censure the Minister of Labor comes in a context of tensions between Pedro Castillo and Perú Libre, with the appointment of four new independent ministers in May 2022. The day before the vote the motion of censure, Waldemar Cerrón met with Pedro Castillo at the Government Palace, referring to a “conversation with the president as allies, not colleagues,” hardening his tone toward the president. On 30 May 2022, Pedro Castillo decided to appoint Juan Lira Loayza as to replace Chávez.
Lariocidin (abbreviated as LAR) is a naturally occurring lasso peptide antibiotic. It is the first lasso peptide reported to inhibit protein synthesis in bacteria through interactions with the ribosome. LAR kills a broad spectrum of bacteria, including multiple human pathogens that are classified as priority pathogens by the World Health Organization such as Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, and Escherichia coli.
Sources: en.wikipedia.org
John's wort), seseli, thlaspi, Daucus carota (carrot), Piper nigrum (black pepper), Piper longum (long pepper), Juniperus (juniper), Syzygium aromaticum (clove), Canary Island wine, Agaricus fruiting bodies Gums, oils and resins: Acaciae (acacia), Styrax benzoin, Gummi arabicum, Sagapeni (wax of an unknown tree, possibly some kind of Ferula), Gummi Opopanax chironium, Gummi Ferula foetida, Commiphora (myrrh), incense, Turpentine from Cyprus, oil from Myristica fragans (nutmeg), Papaver somniverum latex (opium). Animal parts and products: Castoreum, Trochisci Viperarum, Narbonne white honey Mineral substances: Boli armen. verae, Chalciditis (copper salts), Dead Sea bitumen
== Mechanism of action == PAMORAs act by inhibiting the binding of opioids agonist to the μ-opioid receptor (MOR). The objective of PAMORAs treatment is to restore the enteric nervous system function (ENS). The MOR is found in several places in the body and PAMORAs is a competitive antagonist for binding to the receptor. The MORs in the gastrointestinal tract are the main receptors that PAMORAs are intended to block and prevent the binding of opioid agonists. PAMORAs are used in the treatment of opioid-induced bowel dysfunction (OIBD), a potential adverse effect caused by chronic opioid use. PAMORAs act on the three pathophysiological mechanisms of this adverse effect. They act on gut motility, gut secretion and sphincter function. PAMORAs effect on gut motility is that it can increase the resting tone in the circular muscle layer. The antagonist enhances the effect on tonic inhibition of the muscle tone. This will normalize the tone in the circular muscle layer and therefore prevent opioid-induced rhythmic contractions. When these two factors are combined, it results in decreased transit time. Impliedly these effects will decrease the passive absorption of fluids which helps with decreasing OIBD symptoms such as constipation, gut spasm and abdominal cramp. PAMORAs effect on gut secretion will help reverse the decreased cAMP formation that opioid agonists induce. Also, the antagonist will establish a normal secretion of chloride.
Reticular (linear) pattern (sometimes called "reticulonodular" because of the appearance of nodules at the intersection of the lines, even though there are no true nodules present) idiopathic pulmonary fibrosis connective tissue disease sarcoidosis radiation fibrosis asbestosis lymphangitis carcinomatosa PCP Nodular pattern
== Presentation == MFS usually afflicts individuals in their fifth to seventh decades of life although uncommon cases occur in adults outside of this age range In one large study, MFS was diagnosed in individuals 21 to 96 years old (median age 66 years). Most studies have diagnosed MFS slightly more often in men than women but one large study conducted in France found it to be 50% more common in men. Individuals with MFS present with a tumor located in an extremity (77% of cases, usually in the lower extremity), trunk (12% of cases), and head and neck areas (3% of cases). Rarely, these tumors have presented in the breast, heart, paratesticular region (i.e. area inside the scrotum including the epididymis the spermatic cord along with its coverings), eye, bone, liver, or multiple sites concurrently. Primary tumors presenting in the abdominal cavity, retroperitoneum, or pelvis have been diagnosed as MFS but larger studies indicate that these tumors are far more likely to be dedifferentiated liposarcomas. MFS tumors usually develop as painless, slowly enlarging masses in a muscle, skin (usually below the fascia i.e. a sheet of connective tissue, primarily collagen, running beneath the skin), or one of the non-cutaneous areas described above. In one study of 69 FBS cases 36 were <5 cm, 23 were between 5 and 10 cm, and 19 were > 10 cm in diameter with the largest tumor being 27 cm. MFS tumors often infiltrate along vascular and fascial planes, are incompletely removed at surgery, and consequently recur at the surgical site.
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.
TB-500 is a name used for a short synthetic peptide fragment taken from the actin-binding region of thymosin beta-4. Material sold under this label is usually a lyophilized powder supplied for laboratory research rather than a licensed medicine. The commonly cited sequence is LKKTETQ.