Everything below concerns Thymosin beta-4. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-03-04. Numbers and descriptions here follow the published literature rather than marketing material.
TB-500 is a research peptide whose sequence matches residues 17 to 23 of thymosin beta-4, a 43-residue protein present in most mammalian cells. The chain is seven amino acids long, written as LKKTETQ, and is normally supplied with an acetyl group on the N-terminus. Suppliers list it as a lyophilised powder under the code name TB-500, and the same sequence appears elsewhere in catalogues as the thymosin beta-4 actin-binding fragment. The label is commercial rather than systematic, so no single authority fixes exactly what TB-500 denotes.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
Literature and online discussion often conflate TB-500 with full-length thymosin beta-4, even though the two differ in size and are not interchangeable in analytical terms. The fragment is produced by solid-phase peptide synthesis, and the product is a defined seven-residue chain rather than a biological extract. Because the term is a trade-style label, two vendors may supply materials of the same nominal sequence but different counter-ion content, purity, or water content. Comparisons across studies are therefore difficult unless the exact sequence and purity are reported.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
Research interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
TB-500 is a catalogue name applied to a synthetic peptide related to thymosin beta-4, an actin-binding protein found in most mammalian cells. Suppliers do not use the label consistently: some describe it as the full 43-residue protein, others as a short fragment from the actin-binding region, and others as a related tetrapeptide. Because the name is commercial rather than chemical, two products sold under it may not contain the same molecule. This naming ambiguity is the first point to check in any description of the material.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Supplied as a lyophilised cake in sealed vials |
| Solubility class | Freely soluble in water | Polar and charged side chains dominate the sequence |
| Typical storage temperature | -20 °C or below | Dry and dark; a desiccant is often recommended |
| Identity confirmation | Mass spectrometry | Observed mass compared with the theoretical value |
| Common synonyms | Thymosin beta-4 fragment | Also written as T beta 4 fragment 17-23 |
Lyophilized TB-500 is hygroscopic and should be kept dry before use. The usual storage recommendation for the solid is -20 °C, protected from light and moisture. Once dissolved, the peptide is less stable, and repeated freeze-thaw cycles can promote aggregation or degradation. Laboratories often divide a reconstituted solution into single-use aliquots and store them at -80 °C. Exact stability limits depend on buffer, pH, and concentration, so published data do not define a single universal condition.
Identity and purity are checked with chromatographic and mass spectrometric methods. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities, while mass spectrometry confirms the expected molecular mass. A certificate of analysis may report a purity percentage, but the laboratory should still verify the material independently. Common quality concerns include truncated sequences, deamidation, oxidation, and residual solvents from synthesis. Because TB-500 is short, some impurities can differ from the target by only a few mass units.
Reconstitution practices affect downstream measurements. The dry powder is typically dissolved in sterile water or a suitable aqueous buffer, then mixed gently rather than vortexed at high speed. Visible particles or cloudiness suggest incomplete dissolution or contamination and should be investigated. For long-term storage, aliquots should be labeled with concentration, solvent, and date. Open questions include how different buffers alter peptide conformation and whether specific container materials adsorb the peptide. Those variables can change apparent concentration in assays even when the chemical identity is correct.
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.
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.
Conway's first auction was at Albany Anthrocon 1997. Since then, he has presided over auctions which have raised over US$66,000 for a variety of local wildlife charities at Anthrocon alone. He has performed similar services at other fan conventions, including Midwest FurFest. Conway says his techniques are influenced by Phil Foglio and Joe Mayhew; they include humor and appeals to pity, novelty and scarcity.
. Whenever the integer nature of the number of agents is evident (populations with fewer than tens of thousands of individuals), inherent fluctuations in the disease spreading process caused by discrete agents result in uncertainties. In this scenario, the evolution of the disease predicted by compartmental equations deviates significantly from the observed results. These uncertainties may even cause the epidemic to end earlier than predicted by the compartmental equations. As a special case, one obtains the usual logistic function by assuming
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Mixed-mode chromatography (MMC), or multimodal chromatography, refers to chromatographic methods that utilize more than one form of interaction between the stationary phase and analytes in order to achieve their separation. What is distinct from conventional single-mode chromatography is that the secondary interactions in MMC cannot be too weak, and thus they also contribute to the retention of the solutes.
Sources: en.wikipedia.org
== Use and effects == In his book PiHKAL (Phenethylamines I Have Known and Loved) and other publications, Alexander Shulgin lists 3,4-DMA's dose as "a few hundred milligrams" (route unspecified) and its duration as unknown. A dose of approximately 70 mg intravenously produced insignificant to slight psychoactive effects in two individuals. Conversely, a subsequent approximate 700 mg dose intravenously in the same two people produced a definite mescaline-like state, including visual hallucinations (e.g., geometric figures and occasional structured forms), visual distortions, after-images, feelings of unreality, paranoia, marked pupil dilation, and gross body tremors. Gordon Alles reported 3,4-DMA to be inactive at doses of 10 to 120 mg orally but active at 160 mg orally, with reported effects including increased blood pressure, slight pupil dilation, lacrimation, and gastrointestinal uneasiness. He estimated that the response at this dose was equivalent to that of about 60 to 80 mg 3,4-methylenedioxyamphetamine (MDA), suggesting that 3,4-DMA's potency may be about 2- to 3-fold lower than that of MDA and may fall midway between that of MDA and mescaline. Alternatively, according to Shulgin, 3,4-DMA may have comparable potency to mescaline, with an effective dose of perhaps 300 to 400 mg orally, or may be less potent than mescaline. Richard Glennon suggested that the dose may be 400 to 700 mg orally.
First, a coma is induced by intravenous administration of 1 g sodium thiopental (Nesdonal); if necessary, 1.5–2.0 g of the product is given in case of strong tolerance to barbiturates. Then, 45 mg alcuronium chloride (Alloferin) or 18 mg pancuronium bromide (Pavulon) is injected. To ensure optimal availability, these agents are preferably given intravenously. However, they can also be injected intramuscularly. In severe hepatitis or cirrhosis of the liver, alcuronium is the agent of first choice. A coma is first induced by intravenous administration of 20 mg/kg sodium thiopental in a small volume (10 ml physiological saline). Then, a triple intravenous dose of a nondepolarizing neuromuscular muscle relaxant is given, such as 20 mg pancuronium bromide or 20 mg vecuronium bromide (Norcuron). The muscle relaxant should preferably be given intravenously to ensure optimal availability. Only for pancuronium dibromide, the agent may also be given intramuscularly in a dose of 40 mg. A euthanasia machine may allow an individual to perform the process alone.
== Sources == Samuel W. Mitcham (2007). German Order of Battle. Volume Two: 291st–999th Infantry Divisions, Named Infantry Divisions, and Special Divisions in WWII. Stackpole Books. ISBN 978-0-8117-3437-0, p. 148–149. Georg Tessin: Verbände und Truppen der deutschen Wehrmacht und Waffen-SS im Zweiten Weltkrieg 1939–1945. Volume 11. Die Landstreitkräfte 501–630. Biblio-Verlag, Bissendorf 1975, ISBN 3-7648-1181-1, p. 128.
Sources: en.wikipedia.org
No. Thymosin beta-4 is a 43-residue protein, while TB-500 matches only residues 17 to 23 of that chain. The two are related but differ in size, and a method that identifies one does not automatically identify the other.
It corresponds to the actin-binding region of thymosin beta-4. Commercial synthesis reproduces that seven-residue stretch, usually with an acetyl group on the N-terminus.
It is not authorised as a medicine in the United States or the European Union and is distributed as a research chemical. Labels consequently carry research-use-only statements rather than clinical indications.
TB-500 is a trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.