freeze-dried powder raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-04-24 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
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.
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.
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.
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 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 1939 Molotov–Ribbentrop Pact, a non-aggression agreement between Nazi Germany and the Soviet Union, had left the KSČ in disarray. But ever faithful to the Soviet line, the KSČ began a more active struggle against the Germans after Operation Barbarossa, Germany's attack on the Soviet Union in June 1941.
Calcium sulfate (or calcium sulphate) is an inorganic salt with the chemical formula CaSO4. It occurs in several hydrated forms; the anhydrous state (known as anhydrite) is a white crystalline solid often found in evaporite deposits. Its dihydrate form is the mineral gypsum, which may be dehydrated to produce bassanite, the hemihydrate state. Gypsum occurs in nature as crystals (selenite) or fibrous masses (satin spar), typically colorless to white, though impurities can impart other hues. All forms of calcium sulfate are sparingly soluble in water and cause permanent hardness when dissolved therein.
On September 16, 1952, Pauling opened a new research notebook with the words "I have decided to attack the problem of the structure of nuclei." On October 15, 1965, Pauling published his Close-Packed Spheron Model of the atomic nucleus in two well respected journals, Science and the Proceedings of the National Academy of Sciences. For nearly three decades, until his death in 1994, Pauling published numerous papers on his spheron cluster model. The basic idea behind Pauling's spheron model is that a nucleus can be viewed as a set of "clusters of nucleons". The basic nucleon clusters include the deuteron [np], helion [pnp], and triton [npn]. Even–even nuclei are described as being composed of clusters of alpha particles, as has often been done for light nuclei. Pauling attempted to derive the shell structure of nuclei from pure geometrical considerations related to Platonic solids rather than starting from an independent particle model as in the usual shell model. In an interview given in 1990 Pauling commented on his model:
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It has been scientifically shown to improve the rate of wound healing, but the mechanism responsible for this effect is not understood. A 2008 study has claimed that emu oil has a better anti-oxidative and anti-inflammatory potential than ostrich oil, and linked this to emu oil's higher proportion of unsaturated to saturated fatty acids. While there are no scientific studies showing that emu oil is effective in humans, it is marketed and promoted as a dietary supplement with a wide variety of claimed health benefits. Commercially marketed emu oil supplements are poorly standardised.
Carbetocin, sold under the brand names Pabal among others, is a medication used to prevent excessive bleeding after childbirth, particularly following Cesarean section. It appears to work as well as oxytocin. Due to it being less economical than other options, use is not recommended by NHS Scotland. It is given by injection into a vein or muscle. Side effects differ little from that of no treatment or placebo. Use is not recommended in people with epilepsy or eclampsia. Carbetocin is a manufactured long acting form of oxytocin. It works by activating the oxytocin receptor which causes the uterus to contract. Carbetocin was synthesized before 1971 at the Czechoslovak Institute of Organic Chemistry and Biochemistry and was first described by 1974. It was approved for medical use in Canada and the United Kingdom in 1997. It is on the World Health Organization's List of Essential Medicines. It is not available in the United States or Japan.
== Typical activities == Organized crime groups provide a range of illegal services and goods. Organized crime often victimizes businesses through the use of extortion or theft and fraud activities like hijacking cargo trucks and ships, robbing goods, committing bankruptcy fraud (also known as "bust-out"), insurance fraud or stock fraud (insider trading). Organized crime groups also victimize individuals by car theft (either for dismantling at "chop shops" or for export), art theft, Metal theft, bank robbery, burglary, jewelry and gems theft and heists, shoplifting, computer hacking, credit card fraud, economic espionage, embezzlement, identity theft, and securities fraud ("pump and dump" scam). Some organized crime groups defraud national, state, or local governments by bid rigging public projects, counterfeiting money, smuggling or manufacturing untaxed alcohol (rum-running) or cigarettes (buttlegging), and providing immigrant workers to avoid taxes. Organized crime groups seek out corrupt public officials in executive, law enforcement, and judicial roles so that their criminal rackets and activities on the black market can avoid, or at least receive early warnings about, investigation and prosecution. Activities of organized crime include:
== Conservation == In 1997, kutki was listed in appendix II of the Convention on International Trade in Endangered Species (CITES). This listing resulted ultimately from a request by the Indian government. Overharvesting of the wild species for use as medicine was cited as the main reason for the listing. The species is not widely cultivated, though this has been discussed as a potential way to preserve wild stands, especially since the Dunagiri Foundation Trust has created, implemented, and successfully employed protocols to generate export-quality organic ethical 'Dunagiri Certified' Kutki since 2014. The International Union for Conservation of Nature Red List did not have a listing for this species as of 2014. Picrorhiza scrophulariiflora appears to be used heavily as a substitute for P. kurroa and is considered non-threatened by CITES.
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Fusion proteins or chimeric proteins (literally, made of parts from different sources) are proteins created through the joining of two or more genes that originally coded for separate proteins. Translation of this fusion gene results in a single or multiple polypeptides with functional properties derived from each of the original proteins. Recombinant fusion proteins are created artificially by recombinant DNA technology for use in biological research or therapeutics. Chimeric or chimera usually designate hybrid proteins made of polypeptides having different functions or physico-chemical patterns. Chimeric mutant proteins occur naturally when a complex mutation, such as a chromosomal translocation, tandem duplication, or retrotransposition creates a novel coding sequence containing parts of the coding sequences from two different genes. Naturally occurring fusion proteins are commonly found in cancer cells, where they may function as oncoproteins. The bcr-abl fusion protein is a well-known example of an oncogenic fusion protein, and is considered to be the primary oncogenic driver of chronic myelogenous leukemia. In the International nonproprietary name scheme, drugs based on fusion proteins are given the -fusp suffix.
Several different types of fluorescent probes, like cyanine dyes, methyl violegen, or semiconductor quantum dots can be conjugated to silica nanoparticles and delivered into specific cells or injected in vivo. Carrier molecule RGD peptide has been very useful of targeted in vivo imaging. Topically applied surface-enhanced resonance Raman ratiometric spectroscopy (TAS3RS)- TAS3RS is another technique that is starting to make advancement in the medical field. It is an imaging technique that uses Folate Receptors (FR) to detect tumor lesions as small as 370 micrometers. Folate Receptors are membrane bound surface proteins that bind folates and folate conjugates with high affinity. FR is frequently overexpressed in a number of human malignancies including cancer of the ovary, lung, kidney, breast, bladder, brain, and endometrium. Raman imaging is a type of spectroscopy that is used in chemistry to provide structural fingerprint by which molecules can be identified. It relies upon inelastic scattering of photons, which result in ultra high sensitivity. There was a study that was done where two different surface enhanced resonance Raman scattering were synthesized (SERRS).
The State Union of Serbia and Montenegro (often shortened to Serbia and Montenegro), known from 1992 to 2003 as the Federal Republic of Yugoslavia (FRY) and commonly referred to as Yugoslavia, was a country in Southeastern Europe. It was established on 27 April 1992 as a federation comprising the Republic of Serbia and the Republic of Montenegro, following the breakup of the Socialist Federal Republic of Yugoslavia (SFR Yugoslavia). In February 2003, the federation was reconstituted as a state union. Following the secession of Montenegro in June 2006, Serbia proclaimed independence. Its aspirations to be the sole legal successor state to the SFR Yugoslavia were not recognized by the United Nations, following the passing of United Nations Security Council Resolution 777, which affirmed that the Socialist Federal Republic of Yugoslavia had ceased to exist, and the Federal Republic of Yugoslavia was a new state. This made the Federal Republic ineligible to inherit the Socialist Federal Republic's international legal personality, since it had dissolved, with all former republics entitled to state succession. The government of Slobodan Milošević opposed any such claims, and as such, the FR Yugoslavia was not allowed to join the United Nations. Throughout its existence, the FR Yugoslavia had a tense relationship with the international community, as economic sanctions were issued against the state during the course of the Yugoslav Wars and Kosovo War. This also resulted in hyperinflation between 1992 and 1994.
==== Notable cases of toxicity ==== On 19 April 2009, 21 polo ponies died shortly before a match in the United States Polo Open. Three days later, a pharmacy released a statement explaining that the horses had received an incorrect dose of one of the ingredients used in a vitamin/mineral supplement compound that had been incorrectly prepared by a compounding pharmacy. Analysis of blood levels of inorganic compounds in the supplement indicated the selenium concentrations were 10 to 15 times higher than normal in the blood samples and 15 to 20 times higher than normal in the liver samples. Selenium was later confirmed to be the toxic factor.
== Resistance == Resistance is a major cause of treatment failure in chemotherapeutic drugs and results in cancer cell survival despite exposure to such toxins. Broadly, resistance types can be classified based on the points at which cancer cells are no longer susceptible to the effects of chemotherapeutic drugs. One form of resistance is known as primary, or natural resistance, where cancer cells possess innate mechanisms that allow them to be unresponsive to chemotherapeutic drug exposure from the very beginning of its administration. Contrarily, acquired resistance is characterized by an initial, brief period of cancer cell susceptibility to the applied chemotherapeutic agent, followed by later stages of poor drug response. Despite these differences between the points at which resistance emerges, either form can result in what is known as multi-drug resistance, essentially allowing cancer cells to evade the effects of both similarly and differently functioning chemotherapeutic drugs regardless of their previous exposure to them. There are various contributors to emerging resistance in cancer, one of which is the presence of small pumps on the surface of cancer cells that actively transport concentrations of chemotherapy drugs from inside the cell to the outside, otherwise known as efflux pumps. However, these pumps are not unique characteristics of cancer cells whereas in normal functioning cells, efflux pumps are actually engaged in life-sustaining processes that help avoid the accumulation of waste and toxin absorption in the body.
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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.
The most common approach is liquid chromatography with tandem mass spectrometry after extraction from blood or urine. Immunoassays exist but are generally treated as screening tools because of cross-reactivity.