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 2026-04-27 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
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.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Full-length thymosin beta-4 consists of roughly forty-three amino acids and ranks among the more abundant small proteins in the cytoplasm. The fragment is much shorter, so it cannot reproduce every function attributed to the intact molecule. In cell culture, short actin-binding motifs can interfere with filament dynamics and cell movement, but such observations come from controlled experiments rather than from whole-animal work. Whether a truncated fragment produces the same effects as the parent protein remains an open question.
Interest in the peptide grew during the 2000s and 2010s, when studies of tendon and ligament injuries in horses reported changes in lesion size after treatment. Those reports circulated widely outside the scientific literature and shaped much of the current online discussion. Subsequent reviews noted inconsistent study design, small groups, and a shortage of independent replication. Popular descriptions often blur the line between the fragment, the complete protein, and unrelated growth factors, which complicates comparisons across sources.
TB-500 is a synthetic peptide whose sequence corresponds to a short fragment near the N-terminus of thymosin beta-4, a small protein present in most mammalian cells. The fragment is commonly cited as containing the actin-binding region of the parent molecule, which is why it appears in laboratory work on cell migration and tissue repair. Suppliers distribute it as a lyophilised powder intended for research use. Its identity is defined by amino acid sequence and by the presence of an acetyl group on the N-terminal residue.
== Related compounds == A dual DOR and κ-opioid receptor (KOR) PAM, BMS-986187, derived from BMS-986122, has been developed and is selective for these receptors over the MOR. Another MOR PAM with a simpler synthesis, MS1, was subsequently developed and has shown similar effects to those of BMS-986122. Additionally, ignavine, a natural MOR PAM found in Aconitum, has also been identified. In 2024, ketamine and its metabolites norketamine and hydroxynorketamine (HNK) were identified as highly potent MOR, DOR, and KOR PAMs (active at a concentration of as low as 1 nM). These actions were implicated in their potential antidepressant and analgesic effects.
=== Remote sensing data === As with field notes, remote sensing data (aerial and satellite photography, for example), is raw and uninterpreted. It may contain holes (due to cloud cover for example) or inconsistencies (due to the timing of specific image captures). Most modern topographic mapping includes a large component of remotely sensed data in its compilation process.
== Uses == It is used as a wood product and in folk medicine. This valuable wood was used in Chinese furniture from the late Ming and early Qing dynasties, and new furniture in the same styles are sought after as luxury and prestige items.
=== Post-traumatic stress disorder === Witnessing a devastating or terrifying situation can lead to post-traumatic stress disorder (PTSD). This mental health condition triggers anxiety, depression, and extreme fear with memories. Intranasal administration of temperature-sensitive hydrogels loaded with PTSD medications showed enhanced brain targeting effects and tissue distribution. Similarly, another study observed anti-PTSD effects with intranasal administration of loaded hydrogels.
==== Base Editing ==== Base editing is the third major class of rRNA modification, specifically in eukaryotes. There are 8 categories of base edits that can occur at the gap between the small and large ribosomal subunits. RNA methyltransferases are the enzymes that introduce base methylation. Acetyltransferases are the enzymes responsible for acetylation of cytosine in rRNA. Base methylation plays a role in translation. These base modifications all work in conjunction with the two other main classes of modification to contribute to RNA structural stability. An example of this occurs in N7-methylation, which increases the nucleotide's charge to increase ionic interactions of proteins attaching to the RNA before translation.
Sources: en.wikipedia.org
=== 1990–1992: Facelift and Sap === Alice in Chains soon became a top priority of the label, which released the band's first official recording in July 1990, a promotional EP called We Die Young. The EP's lead single, "We Die Young", became a hit on metal radio. After its success, the label rushed Alice in Chains' debut album into production with producer Dave Jerden. Cantrell stated the album was intended to have a "moody aura" that was a "direct result of the brooding atmosphere and feel of Seattle." The resulting album, Facelift, was released on August 21, 1990, peaking at number 42 in mid-1991 on the Billboard 200 chart. Facelift was not an instant success, selling under 40,000 copies in the first six months of release, until MTV added "Man in the Box" to regular daytime rotation. The single hit number 18 on the Mainstream rock charts, with the album's follow up single, "Sea of Sorrow", reaching number 27, and in six weeks Facelift sold 400,000 copies in the US. The album was a critical success, with Steve Huey of AllMusic citing Facelift as "one of the most important records in establishing an audience for grunge and alternative rock among hard rock and heavy metal listeners." Sammy Hagar claimed he invited the band to tour with Van Halen after he saw the music video for "Man In The Box" on MTV.
Upon hearing of the assassination of socialist candidate Jorge Eliécer Gaitán, many poor workers saw the death of Gaitán as a political assassination orchestrated by the rich. Workers began rioting and destroying the Colombian capital of Bogotá, leading to the death of 4,000 people. When news of the death of Gaitán reached the countryside, the local militias were furious and immediately started a civil war, known as La Violencia. Joined by fellow leftists, a brutal war was fought for over 10 years, leading to the death of 200,000 people and the destruction of much of the country, resulting in a peace settlement and the changing of power from the Colombian Conservative Party to the Colombian Liberal Party and the Colombian Communist Party in 1958. As La Violencia wound down, most self-defense and guerrilla units composed of Liberal Party supporters were demobilized. At the same time, some former liberals and active communist groups continued operating in several rural enclaves. One of the Liberal bands was a group known as the "Fuerzas Armadas Revolucionarias de Colombia" (Revolutionary Armed Forces of Colombia), or FARC, formed by Pedro Antonio Marín in 1964. The FARC was founded out of fighters who were unhappy with the peace settlement. The goal of the FARC, among other things, was land redistribution that would benefit poor peasant farmers like Marín, along with the desire to establish a socialist state. In 1958, an exclusively bipartisan political alternation system, known as the National Front, resulted from an agreement between the Liberal and Conservative parties.
=== Defensive behavior === The primary defense strategy performed by P. phalangioides in moments of predation is whirling. Whirling, or a gyration of the body, consists of the spider swinging its body around in a circle repeatedly while its legs remain fixed on the web. This whirling strategy is induced as soon as the individual recognizes any sort of movement occurring in its web. The duration of this whirling is related to the specific kind of predator that the spider encounters. Short-duration whirling can be induced simply by a human touching the spider's web or occasionally by spider of a different species. Long-duration whirling, which can last several hours or even days, is performed specifically in response to the presence of the more threatening Salticid, or jumping spiders, much more often than for spiders of other families. The rapid gyrating associated with the whirling disturbs the vision of the Salticid spiders such that they can no longer rely on their acute eyesight to pinpoint the location of P. phalangioides. This disruption results in the safety of the spiders from an otherwise deadly predator.
==== Luminal ions ==== In addition to NAADP gating the channel, there is evidence that the luminal pH also affects TPC channel activity, either TPC1 [1] or TPC2 [2][3]. However, a clear consensus on the effect of pH has not been reached with some suggesting that acidic pH favours TPC1 or TPC2 opening, whereas others report that a more alkaline pH favours TPC2 opening. Furthermore, luminal Ca2+ also promotes TPC1 and TPC2 opening (in the latter case, luminal Ca2+ also sensitizes TPCs to NAADP (analogous to luminal Ca2+ regulation of IP3Rs and RyRs), but this demands wider study across isoforms and species. This is one way by which cross-talk can occur between acidic Ca2+ stores and the ER i.e. Ca2+ release from the ER can 'prime' acidic Ca2+ stores and promote further NAADP-dependent Ca2+ responses [4].
Sources: en.wikipedia.org
== Predicted properties == According to the periodic law, dubnium should belong to group 5, with vanadium, niobium, and tantalum. Several studies have investigated the properties of element 105 and found that they generally agreed with the predictions of the periodic law. Significant deviations may nevertheless occur, due to relativistic effects, which dramatically change physical properties on both atomic and macroscopic scales. These properties have remained challenging to measure for several reasons: the difficulties of production of superheavy atoms, the low rates of production, which only allows for microscopic scales, requirements for a radiochemistry laboratory to test the atoms, short half-lives of those atoms, and the presence of many unwanted activities apart from those of synthesis of superheavy atoms. So far, studies have only been performed on single atoms.
== Community metabolism == The common ancestor of the now existing cellular lineages (eukaryotes, bacteria, and archaea) may have been a community of organisms that readily exchanged components and genes. It would have contained:
=== Standard addition === The method of standard addition is used in instrumental analysis to determine the concentration of a substance (analyte) in an unknown sample by comparison to a set of samples of known concentration, similar to using a calibration curve. Standard addition can be applied to most analytical techniques and is used instead of a calibration curve to solve the matrix effect problem.
Sources: en.wikipedia.org
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
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.