A practical reference on lyophilised powder: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-05-12 and is reviewed periodically as new material appears.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
Thymosin beta-4 itself is a small, widely expressed protein that sequesters monomeric actin and participates in cell migration, angiogenesis, and tissue repair. Researchers have examined the shortened fragment as a possible mimic of some of these activities, reasoning that the actin-binding motif lies within the first few residues. Binding to monomeric actin has been observed in cell-free systems. Whether the fragment reproduces the broader effects of the full protein in living tissue remains an open question, and findings from animal models are frequently cited without a clear bridge to human physiology.
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | N-terminal fragment of thymosin beta-4 |
| Residue count | Seven | Sequence LKKTETQ |
| Approximate mass | 889 Da | Acetylated seven-residue peptide |
| Common synonyms | TB4 fragment, TB500 | Not identical to full-length TB4 |
| Reported activity | Actin binding | Observed mainly in cell-free systems |
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.
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.
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.
Reconstitution of a lyophilized peptide is normally done with sterile water or a suitable buffer under aseptic conditions. Adding solvent down the vial wall and allowing gentle dissolution instead of vigorous vortexing reduces the chance of aggregation, which can lower the effective concentration of the resulting solution. Concentrated stocks are usually diluted into working buffer shortly before use. Because no standard preparation protocol exists for TB-500 specifically, laboratories adapt general peptide handling practice, and reported results may reflect differing preparation choices.
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
== Full list == The tables are based now on the standard reference NUBASE2020 and its companion, based on the same data, AME2020. All observational data not otherwise cited should be found in those sources, or calculated from them, and only observed data, not theoretical extrapolations, should be present in these tables.
When HypSys is silenced the production of protease inhibitors induced by wounding is halved compared to wild type plants indicating that both systemin and HypSys are required for a strong defence response against herbivores in tomato. When applied through cut petioles in Petunia, HypSys did not induce the production of protease inhibitors, but instead increased expression of defensin, a gene which produces a protein that inserts into microbial membranes, forming a pore. Defensin expression is also induced by AtPEP1. Tomato plants over-expressing systemin produced more volatile organic compounds (VOCs) than normal plants and parasitoid wasps found them more attractive. Systemin also upregulates the expression of genes involved in the production of biologically active VOCs. Such a response is crucial if antinutritional defences are to be effective, since without predators, developing insects would consume more plant material while completing their development. It is likely that VOC production is upregulated through different pathways, including oxylipin pathway that synthesises jasmonic acid aldehydes and alcohols that function in wound healing. Different AtPeps may allow A. thaliana to distinguish between different pathogens. When inoculated with a fungus, oomycete and a bacterium, the increases in AtPep expression varied depending on the pathogen. A. thaliana overexpressing AtProPep1 was more resistant to the oomycete Phythium irregulare.
== Notable people == Pope Pius I is believed to have been born at Aquileia during the late first century. Saint Chrysogonus was martyred here in the beginning of the fourth century. Licia Kokocinski - Australian politician
=== Diagnostic uses === Diagnostic qualitative PCR is applied to rapidly detect nucleic acids that are diagnostic of, for example, infectious diseases, cancer and genetic abnormalities. The introduction of qualitative PCR assays to the clinical microbiology laboratory has significantly improved the diagnosis of infectious diseases, and is deployed as a tool to detect newly emerging diseases, such as new strains of flu and coronavirus, in diagnostic tests.
Sources: en.wikipedia.org
=== Radioactive contamination === RTGs pose a risk of radioactive contamination: if the container holding the fuel leaks, the radioactive material may contaminate the environment. For spacecraft, the main concern is that if an accident were to occur during launch or a subsequent passage of a spacecraft close to Earth, harmful material could be released into the atmosphere; therefore their use in spacecraft and elsewhere has attracted controversy. However, this event is not considered likely with current RTG cask designs. For instance, the environmental impact study for the Cassini–Huygens probe launched in 1997 estimated the probability of contamination accidents at various stages in the mission. The probability of an accident occurring which caused radioactive release from one or more of its three RTGs (or from its 129 radioisotope heater units) during the first 3.5 minutes following launch was estimated at 1 in 1,400; the chances of a release later in the ascent into orbit were 1 in 476; after that the likelihood of an accidental release fell off sharply to less than 1 in a million. If an accident which had the potential to cause contamination occurred during the launch phases (such as the spacecraft failing to reach orbit), the probability of contamination actually being caused by the RTGs was estimated at 1 in 10. The launch was successful and Cassini–Huygens reached Saturn. To minimize the risk of the radioactive material being released, the fuel is stored in individual modular units with their own heat shielding.
=== Parathyroid hormone-related protein === Parathyroid hormone-related protein (PTHrP) is a multifunctional peptide that plays a crucial role in calcium homeostasis, vascular regulation, and cellular proliferation. While it is traditionally recognized as a secreted factor that binds to surface receptors, PTHrP also functions as an intracrine regulator within cardiac cells. Its intracrine actions influence myocardial growth, vascular remodeling, and responses to stress, making it a key factor in cardiovascular physiology and pathology.
Sheikha Fatima bint Hazza bin Zayed Al Nahyan. Sheikha Salama bint Hazza bin Zayed Al Nahyan. Sheikh Zayed bin Hazza bin Zayed Al Nahyan (born 1995). He has one son. Sheikh Hazza bin Zayed Al Nahyan (born 2026). Sheikha Meera bint Hazza bin Zayed Al Nahyan. She married Sheikh Zayed bin Mansour bin Zayed Al Nahyan on May 5, 2022. Sheikh Mohammed bin Hazza bin Zayed Al Nahyan (born 2002).
==== Zonal necrosis ==== This is the most common type of drug-induced liver cell necrosis where the injury is largely confined to a particular zone of the liver lobule. It may manifest as a very high level of ALT and severe disturbance of liver function leading to acute liver failure.
The Quantum-Mechanical Calculation of the Resonance Energy of Benzene and Naphthalene and the Hydrocarbon Free Radicals" (PDF). The Journal of Chemical Physics. 1 (6): 362. Bibcode:1933JChPh...1..362P. doi:10.1063/1.1749304. Archived (PDF) from the original on 2022-10-09. —— (1935). "The Structure and Entropy of Ice and of Other Crystals with Some Randomness of Atomic Arrangement". Journal of the American Chemical Society. 57 (12): 2680–2684. Bibcode:1935JAChS..57.2680P. doi:10.1021/ja01315a102. —— (1940). "A Theory of the Structure and Process of Formation of Antibodies*". Journal of the American Chemical Society. 62 (10): 2643–2657. Bibcode:1940JAChS..62.2643P. doi:10.1021/ja01867a018. —— (1947). "Atomic Radii and Interatomic Distances in Metals". Journal of the American Chemical Society. 69 (3): 542–553. Bibcode:1947JAChS..69..542P. doi:10.1021/ja01195a024. ——; Itano, H. A.; Singer, S. J.; Wells, I. C. (1949). "Sickle Cell Anemia, a Molecular Disease". Science. 110 (2865): 543–548. Bibcode:1949Sci...110..543P. doi:10.1126/science.110.2865.543. PMID 15395398. S2CID 31674765. ——; Corey, R. B.; Branson, H. R. (1951). "The structure of proteins: Two hydrogen-bonded helical configurations of the polypeptide chain". Proceedings of the National Academy of Sciences. 37 (4): 205–11. Bibcode:1951PNAS...37..205P. doi:10.1073/pnas.37.4.205. PMC 1063337. PMID 14816373. —— (1964). "The Architecture of Molecules". Proceedings of the National Academy of Sciences. 51 (5): 977–984. Bibcode:1964PNAS...51..977P. doi:10.1073/pnas.51.5.977. ISSN 0027-8424. PMC 300194. PMID 16591181.
Sources: en.wikipedia.org
=== Pharmacodynamics === Nor-LSD showed 5- to 29-fold lower affinity for the serotonin 5-HT2 receptor compared to LSD (Ki = 30–158 nM vs. 5.4 nM, respectively). It also showed affinity for the serotonin 5-HT1 receptor. In another more recent study however, nor-LSD showed similar or even higher affinities, activational potencies, and/or efficacies at the serotonin 5-HT1A, 5-HT2A, and 5-HT2B receptors as LSD, whereas it showed 36-fold lower affinity for the serotonin 5-HT2C receptor compared to LSD. Nor-LSD failed to completely substitute for LSD in rodent drug discrimination tests even at very high doses. The greatest degree of substitution with nor-LSD was 75% at a dose of 7,420 nM/kg, whereas 100% substitution occurred with LSD at a dose of 186 nM/kg (a 40-fold lower dose). The ED50Tooltip median effective dose was 2,594 nM/kg for nor-LSD and 46 nM/kg for LSD. Hence, nor-LSD was approximately 56-fold less potent than LSD in terms of producing LSD-like effects in rodents and failed to produce full LSD-like effects even at the highest assessed dose. In another study, nor-LSD failed to produce LSD-like electroencephalogram (EEG) changes in rabbits.
A protein usually undergoes reversible structural changes in performing its biological function. The alternative structures of the same protein are referred to as different conformations, and transitions between them are called conformational changes.
Further, they found that the hormone was produced from pancreatic islets by cells differing from the insulin-producing beta cells; presumably these were alpha cells. It was de Duve who realised that Sutherland's HG factor was in fact the same as glucagon; this rediscovery led to its permanent name, which de Duve reintroduced it in 1951. The pair's work showed that glucagon was the major hormone influencing the breakdown of glycogen in the liver—the process known as glycogenolysis—by which more sugars are produced and released into the blood. De Duve's original hypothesis that glucagon was produced by pancreatic alpha cells was proven correct when he demonstrated that selectively cobalt-damaged alpha cells stopped producing glucagon in guinea pigs; he finally isolated the purified hormone in 1953, including those from birds. De Duve was first to hypothesise that the production of insulin (which decreased blood sugar levels), stimulated the uptake of glucose in the liver; he also proposed that a mechanism was in-place to balance the productions of insulin and glucagon in order to maintain normal blood sugar level, (see homeostasis). This idea was much disputed at the time, but his rediscovery of glucagon confirmed his theses. In 1953 he experimentally demonstrated that glucagon did influence the production (and thus the uptake) of glucose.
==== Predation theory for multicellularity ==== This theory postulates that multicellularity arose as a means for prey to escape predation. Larger prey are less likely to be preyed upon, and larger predators are more likely to catch prey. Therefore it is likely that multicellularity arose when the first predators evolved. By assembling as a larger, multicelled organism, prey could escape the attempts of a predator. Therefore multicellularity was selectively favoured over unicellularity. This can be seen in a simple experiment conducted by Boraas et al. (1998). When a predatory protist, Ochromonas valencia, was introduced to a prey population of Chlorella vulgaris, it was seen that within less than 100 generations of the prey species a multicellular growth form of the alga became dominant. This is interesting because before the predator was introduced, the population of Chlorella vulgaris retained its unicellular growth form for thousands of generations. It is likely that it would have remained unicellular indefinitely if the selective pressure that was induced by the predators had not been introduced. After multiple generations with the predator, the algal species retained a growth form of 8-10 cells, which was large enough to avoid the predator, but small enough that each cell still had access to nutrients. This predator-prey relationship provides a likely reason for why it was beneficial for organisms to be multicellular.
Sources: en.wikipedia.org
No. Thymosin beta-4 is a 43-residue protein, while TB-500 refers to a seven-residue fragment corresponding to its N-terminal region. The two names are often used loosely in commercial and community writing, which obscures the difference in size, sequence, and likely behavior.
The fragment contains an actin-binding motif, and cell-free experiments show that it can interact with monomeric actin. That observation is the basis for interest in cell migration and repair processes. Effects reported in animals are not established for humans.
Purity is usually stated by the supplier rather than fixed by a pharmacopoeial monograph, and typical listings report a percentage from reverse-phase HPLC. Independent verification is uncommon. Because no single accepted specification exists, comparisons between lots and between suppliers are difficult.
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.