The short version of freeze-dried powder fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-07-30 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
Proposed activity centers on actin sequestration and on the movement of cells during repair processes. In cell culture and animal models, the fragment has been associated with migration, tube formation, and tissue remodeling. These observations are frequently described as preliminary, because most published work uses rodent or in vitro systems rather than controlled human trials. Whether the short fragment reproduces the effects of the full protein remains an open question, and the relationship between dose, route, and measured outcome is not well characterized.
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.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
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.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
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.
== Humans == In contrast to chimpanzees, a common morphological variant found in humans called hirsuties coronae glandis, or pearly penile papules, are substantially larger, appear to be an outpocketing of both surface and underlying connective tissue layers, and lack the rich innervation seen in other animals. These are sometimes described as vestigial remnants of penile spines. However, the relationship between the structures is still uncertain. When the hominin lineage split into the genera Homo and Pan, a regulatory DNA sequence associated with the formation of small keratinized penile spines was lost in the Homo lineage. This simplification of penis anatomy may be associated with the sexual habits of humans. In some species which retain full expression, penile spines contribute to increased sexual sensation and quicker orgasms. An hCONDEL (highly conserved region of DNA that contains deletions in humans) located near the locus of the androgen receptor gene may be responsible for the loss of penile spines in humans.
To demonstrate just how deadly this species is, an estimate was made on the number of mice and adult human fatalities it is capable of causing in a single bite that yields the maximum dose of 400 mg. Based on the study by Ernst and Zug et al. 1996, which listed the LD50 of the coastal taipan at 0.106 mg SC and a venom yield of 400 mg, this would be sufficient to kill 208,019 mice and 59 adult humans in a single bite that delivers 400 mg of venom. The venom apparatus of this species is well developed. The fangs are the longest of any Australian elapid snake, being up to 1.2 cm (0.5 in) long, and are able to be brought forward slightly when a strike is contemplated. Coastal taipans can inject large amounts of highly toxic venom deep into the tissue. Its venom contains primarily taicatoxin, a highly potent neurotoxin known to cause hemolytic and coagulopathic reactions. The venom affects the nervous system and the blood's ability to clot, and bite victims may experience headache, nausea and vomiting, collapse, convulsions (especially in children), paralysis, internal bleeding, myolysis (destruction of muscle tissue) and kidney damage. In a single study done in Papua New Guinea, 166 patients with enzyme immunoassay-proven bites by Papuan taipans (Oxyuranus scutellatus canni) were studied in Port Moresby, Papua New Guinea. Of the 166 bite victims, 139 (84%) showed clinical evidence of envenoming: local signs were trivial, but the majority developed hemostatic disorders and neurotoxicity.
The New Zealand Parliament is a unicameral legislature made up of the monarch and the House of Representatives. A "member of Parliament" is a member of the House of Representatives, which has a minimum of 120 members, elected at a general election for a three-year term. There are 72 electorate MPs, of which seven are elected only by Māori who have chosen to be registered on a separate Māori electoral roll. The remaining members are elected by proportional representation from published party lists. Since 1907, members of the House of Representatives have been referred to as "Member of Parliament", abbreviated MP. From the 1860s until 1907 they were designated as "Member of the House of Representatives", abbreviated MHR. Between the first general election, in 1853, and the 1860s, the designation was "Member of the General Assembly", abbreviated MGA. Before 1951, New Zealand had an upper house, the Legislative Council, whose members were appointed.
Sources: en.wikipedia.org
Parallel to Via Roma, the other two popular pedestrian streets, namely Via Lagrange and Via Carlo Alberto, cross the old town from Via Po to Corso Vittorio Emanuele II. Their recent pedestrianisation has improved their original commercial vocation. In particular, Via Lagrange has recently increased the presence of luxury boutiques. This street also hosts the Egyptian Museum of Turin, home to what is regarded as one of the largest collections of Egyptian antiquities outside of Egypt. Via Lagrange and Via Carlo Alberto cross two significant squares of the city, respectively. The former crosses Piazza Carignano, well known mainly for the undulating "concave – convex-concave" Baroque façade of Palazzo Carignano. This building used to host the Parlamento Subalpino (the 'Subalpine Parliament', Parliament of the Kingdom of Sardinia which also became the Italian Parliament for a few years, after the Italian unification) and today houses the Museum of the Risorgimento. The square also features the Teatro Carignano, a well-conserved Baroque theatre. Via Carlo Alberto crosses Piazza Carlo Alberto, a big square hosting the rear façade of Palazzo Carignano, in eclectic style. On the other side stands the monumental Biblioteca Nazionale (National Library).
==== Topoisomerases and helicases ==== Topoisomerases are enzymes with both nuclease and ligase activity. These proteins change the amount of supercoiling in DNA. Some of these enzymes work by cutting the DNA helix and allowing one section to rotate, thereby reducing its level of supercoiling; the enzyme then seals the DNA break. Other types of these enzymes are capable of cutting one DNA helix and then passing a second strand of DNA through this break, before rejoining the helix. Topoisomerases are required for many processes involving DNA, such as DNA replication and transcription. Helicases are proteins that are a type of molecular motor. They use the chemical energy in nucleoside triphosphates, predominantly adenosine triphosphate (ATP), to break hydrogen bonds between bases and unwind the DNA double helix into single strands. These enzymes are essential for most processes where enzymes need to access the DNA bases.
=== GLC (1981–1985) === The equivalent American Mazda GLC (Great Little Car) appeared in the 1981 model year, although the rear-wheel drive wagon also continued to be offered. It was only offered with a single engine – the twin-barrel 1.5-litre with 68 hp (51 kW)—and lasted through 1985, after which it was replaced by the next-generation Mazda 323. With this, the GLC nameplate was retired. The BD was the only front-wheel drive Mazda vehicle using the GLC name. Originally it was offered with three- or five-door bodywork, in standard, Custom, Custom L, or Sport equipment levels. The five-door only came as a Custom and was sold only in Hawaii and Puerto Rico. All cars received exposed rectangular sealed-beam units. The later four-door saloon, introduced for 1983, was available in Custom, Custom L, and Sport models. The Sport received blacked out trim, a steering wheel borrowed from the RX-7, full instrumentation, and a special rear interior which closely integrates the side trim with the rear seat design – an early iteration of a design philosophy taken to its extreme with the 1988 Persona and the 1990 Eunos Cosmo. Unlike the sporting 323s in other markets, the Sport only received special hubcaps, rather than alloy wheels. For 1982, the Sport was made to live up to its name a little bit more, with the installation of a front anti-roll bar and cast aluminum wheels. The five-door GLC gained a fully carpeted trunk for 1982.
The layers of the body can be approximated as a thin layer of epidermis, dermis, adipose tissue (subcutaneous fat), and muscle tissue. At dozens of gigahertz, the radiation is absorbed in the top fraction to top few millimeters of skin. Muscle tissue is a much more efficient absorber than fat, so at lower frequencies that can penetrate sufficiently deep, most energy gets deposited there. In a homogeneous medium, the energy-depth dependence is an exponential curve with the exponent depending on the frequency and tissue. For 2.5 GHz, the first millimeter of muscle tissue absorbs 11% of the heat energy, the first two millimeters together absorb 20%. For lower frequencies, the attenuation factors are much lower, the achievable heating depths are higher, and the temperature gradient within the tissue is lower.
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.
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.