This is a working overview of lyophilised powder, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-15. Anything still debated is marked as such rather than presented as settled.
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 synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Calculated for the acetylated heptapeptide |
| Molecular weight | ~889 Da | Monoisotopic mass approximately 889.0 Da |
| Amino acid sequence | Ac-LKKTETQ | N-terminal acetylated seven-residue peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Water-soluble | Peptides of this size generally dissolve in aqueous media |
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.
Identity and purity checks for peptide material typically combine reversed-phase high-performance liquid chromatography with mass measurement, since retention time alone cannot confirm a sequence. Mass measurement verifies the expected molecular mass within instrument tolerance, while chromatographic peak area provides a purity estimate. Anti-doping analysis of urine uses related but more sensitive workflows, sometimes after solid-phase extraction. For research material, batch documentation, certificate content, and independent testing are common points of scrutiny, because supply chains outside pharmaceutical regulation vary widely in the paperwork they provide.
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.
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.
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.
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.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
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.
=== Nuclear isomers, including a "stable" one === The 251 known stable nuclides include tantalum-180m, since even though its decay is automatically implied by it being "metastable", this has not been observed. All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, except for tantalum-180m, which is a nuclear isomer or excited state. The ground state, tantalum-180, is radioactive with half-life 8 hours; in contrast, the decay of the nuclear isomer is extremely strongly forbidden by spin-parity selection rules. It has been reported by direct observation that the half-life of 180mTa to gamma decay must be >1015 years. Other possible modes of 180mTa decay (beta decay, electron capture, and alpha decay) have also never been observed.
A 2021 study confirmed these findings, noting that "the protective allele of rs7170637(A) CYFIP1, [one of the genes associated with autism spectrum disorder (ASD)], was present in primates to Neanderthals, and reemerged in modern humans, while absent in early modern humans"; "identified significant positive selection signals in 18 ASD risk SNPs"; that "ancient genome analysis identified de novo mutations...representing genes involved in cognitive function...and conserved evolutionary selection clusters"; and that "relative enrichment of the ASD risk SNPs from the respective evolutionary cluster or biological interaction networks may help in addressing the phenotypic diversity in ASD", with "cognitive genomic tradeoff signatures impacting the biological networks [explaining] the paradoxical phenotypes in ASD".
The Colombia national football team (Spanish: Selección de fútbol de Colombia), nicknamed Los Cafeteros, represents Colombia in men's international association football. It is administered by the Colombian Football Federation (Spanish: Federación Colombiana de Fútbol), the governing body for football in Colombia. The federation has been affiliated with FIFA and CONMEBOL since 1936. Colombia have appeared at seven FIFA World Cups, first qualifying for the 1962 FIFA World Cup. Their best performance came at the 2014 FIFA World Cup, where they reached the quarter-finals for the first time; James Rodríguez won the Golden Boot after scoring six goals. Colombia have also reached the knockout stage at the 1990, 2018 and 2026 tournaments. Colombia won the 2001 Copa América as hosts, winning all six matches without conceding a goal. The team has also finished as runners-up in 1975 and 2024, and third in 1987, 1993, 1995, 2016 and 2021.
White for hydrogen Black for carbon Blue for nitrogen Red for oxygen Deep yellow for sulfur Purple for phosphorus Light, medium, medium dark, and dark green for the halogens (F, Cl, Br, I) Silver for metals (Co, Fe, Ni, Cu)
=== Time === Moscow serves as the reference point for the time zone used in most of European Russia, Belarus, and Crimea. These areas operate in Moscow Standard Time (MSK, МСК), which is 3 hours ahead of UTC (or UTC+3). Daylight saving time is no longer observed in Moscow. According to geographical longitude, the average solar noon in Moscow occurs at 12:30.
Sources: en.wikipedia.org
=== Glutamatergic gliotransmission === Some specialized astrocytes mediate glutamatergic gliotransmission in the central nervous system. Such cells have been called hybrid brain cells because they exhibit both neuron-like and glial-like properties. Unlike traditional neurons, these cells not only transmit electrical signals but also provide supportive roles typically associated with glial cells, such as regulating the brain's extracellular environment and maintaining overall homeostasis.
A vial can be tubular, or have a bottle-like shape with a neck. The volume defined by the neck is known as the headspace. The English word "vial" is derived from the Greek phiale, meaning "a broad flat container". Comparable terms include the Latin phiala, Late Latin fiola and Middle English fiole and viole.
Its floral axes, or flower-bearing structures, bear bracteoles, or specialised leaves, that sprout from the flower stems; the latter are known as pedicels. After aestivating in spring, the plant sends up its true leaves, each up to 40 cm (16 in) in length. Only in October, after most other flowering plants have released their seeds, do its brilliantly hued flowers develop; they range from a light pastel shade of lilac to a darker and more striated mauve. The flowers possess a sweet, honey-like fragrance. Upon flowering, the plants are 20–30 cm (8–12 in) in height and bear up to four flowers. A three-pronged style 25–30 mm (1–1+3⁄16 in) in length, emerges from each flower. Each prong terminates with a vivid crimson stigma, which is the distal end of a carpel.
Lee Waise Lee as Edward Lai (黎永廉), Secretary of Justice / co-conspirator of Peter Choi King Kong Lam as Gary Fu, Ex-Senior Inspector of Police Vincent Lam as Neo Chan, Ex-Senior Inspector of Police Wong Man-piu as Eric Ma, Ex-Senior Inspector of Police Brian Wong as Mark Cheng, Ex-Senior Inspector of Police Felix Lok as C.Y. Ma, Member of the Legislative Council / Chairman of Security Panel Council / co-conspirator of Peter Choi Terence Yin as To Man, Chief Superintendent, Director of Information Technology Jeannie Chan as Nicole Chan, ICAC Assistant Investigator Kathy Yuen as Cecilia Lai, Probationary Inspector of Police and secretary to Commissioner Dexter Young as Senior Inspector of Police, Technology Crime Division Queenie Chu as Amber Tsui, cigar lounge owner / co-conspirator of Peter Choi Leila Tong as Karen Tang, hostage
Sources: en.wikipedia.org
The length and nature of parental care varies widely amongst different orders and species. At one extreme, parental care in megapodes ends at hatching; the newly hatched chick digs itself out of the nest mound without parental assistance and can fend for itself immediately. At the other extreme, many seabirds have extended periods of parental care, the longest being that of the great frigatebird, whose chicks take up to six months to fledge and are fed by the parents for up to an additional 14 months. The chick guard stage describes the period of breeding during which one of the adult birds is permanently present at the nest after chicks have hatched. The main purpose of the guard stage is to aid offspring to thermoregulate and protect them from predation.
Draculin (named after Count Dracula) is a glycoprotein found in the saliva of vampire bats, Desmodus rotundus. It is a member of the lactotransferrin protein family. It is a single-chain polypeptide protein composed of 708 amino acids, weighing about 88.5 kDa when reduced and 83 kDa when non-reduced, and selectively inhibits FIXa and FXa. It functions as an anticoagulant, inhibiting coagulation factors IX (IXa) and X (Xa) by establishing rapid equilibrium with factor Xa, and is the first natural polypeptide which has been described to show immediate anti-IXa and anti-Xa properties. The rapid equilibrium achieved at comparable concentrations of FXa and Draculin, as well as the lack of any detectable lag phases in assays, supports the conclusion that Draculin is a tight-binding inhibitor. In addition, Draculin inhibits the conversion of prothrombin to thrombin, preventing fibrinogen from converting to fibrin. These two processes inhibit blood coagulation thus keeping the blood of the bitten victim from clotting while the bat is drinking. The activation of factor X is a common point between the intrinsic and extrinsic pathway of blood coagulation.
Tetrahydrocannabinol (THC) is the primary psychoactive component of the Cannabis plant. Delta-9-tetrahydrocannabinol (Δ9-THC, THC) and delta-8-tetrahydrocannabinol (Δ8-THC) induce anandamide and 2-arachidonoylglycerol synthesis through intracellular CB1 activation. These cannabinoids produce the psychoactive effects of cannabis by binding to CB1 receptors in the brain.
Sources: en.wikipedia.org
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.
No. Thymosin beta-4 is a 43-amino-acid protein, while TB-500 represents only a short N-terminal segment. The two should not be treated as interchangeable in experimental design.
It is often called a thymosin beta-4 fragment, Tβ4 fragment, or Ac-LKKTETQ. The name TB-500 is mainly a commercial or catalog label rather than a formal chemical name.
Short transit at ambient temperature is generally tolerated, but long-term storage at room temperature is not recommended. Heat, moisture, and light all accelerate degradation. Cold, dry, dark storage is the conventional choice.