If you have been reading about research chemical and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-11-10. Numbers and descriptions here follow the published literature rather than marketing material.
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.
No major regulatory agency has approved TB-500 for therapeutic use, and it holds no pharmacopoeial monograph. The name appears on the World Anti-Doping Agency prohibited list within the class covering peptide hormones, growth factors, and related substances. Detection in doping control relies on mass spectrometric methods applied to urine, often after preparation steps that concentrate the analyte. Discussion of TB-500 therefore clusters in biochemistry, sports medicine, and anti-doping literature rather than in registered clinical trials.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
Laboratory work on thymosin beta-4 describes binding to monomeric actin and effects on cell migration, angiogenesis, and inflammatory signaling in cultured cells. Animal models have examined skin, corneal, and cardiac repair after injury, with outcomes reported mainly in preclinical literature. Most of that evidence concerns the parent protein rather than preparations labelled TB-500, so extrapolation from animal findings to a specific commercial product remains uncertain. Whether the two behave identically in living systems has not been established in controlled human studies.
| 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 |
Purity and identity are separate measurements and are often confused. Reverse-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, reports the share of total peak area belonging to the target compound. Mass spectrometry by electrospray or matrix-assisted laser desorption then checks whether the observed mass matches the expected sequence. Neither measurement alone shows that a vial holds the intended peptide. Peptide content, meaning the fraction of vial mass that is genuine peptide rather than counter-ion, water or residual acid, is reported separately and is frequently lower than the stated purity figure.
The regulatory position is broadly consistent across major jurisdictions: no thymosin beta-4 fragment is an approved medicine, and laboratory material is commonly labelled as not intended for human consumption. Anti-doping rules in sport list thymosin beta-4 and its fragments among prohibited peptide hormones. Because these products travel through research-chemical channels rather than pharmaceutical supply chains, quality varies considerably between vendors. Independent testing of identity, purity and sterility is the only dependable check, and a certificate of analysis describes one batch rather than a supplier's whole catalogue.
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.
where c = composition, p = polarity, and v = molecular volume; and are constants of squares of the inverses of the mean distance for each property, respectively equal to 1.833, 0.1018, 0.000399. According to Grantham's distance, most similar amino acids are leucine and isoleucine and the most distant are cysteine and tryptophan.
Over 1,000 Kuwaiti civilians were killed by Iraqis. More than 600 Kuwaitis went missing during Iraq's occupation, and approximately 375 remains were found in mass graves in Iraq. The increased importance of air attacks from both coalition warplanes and cruise missiles led to controversy over the number of civilian deaths caused during Desert Storm's initial stages. Within Desert Storm's first 24 hours, more than 1,000 sorties were flown, many against targets in Baghdad. In one noted incident, two USAF stealth planes bombed a bunker in Amiriyah, killing 408 Iraqi civilians. Scenes of burned and mutilated bodies were subsequently broadcast, and controversy arose over the bunker's status, with some stating that it was a civilian shelter, while others contended that it was a center of Iraqi military operations, and that the civilians had been deliberately moved there to act as human shields. The Iraqi government claimed that 2,300 civilians died during the air campaign. A Project on Defense Alternatives study found that 3,664 Iraqi civilians were killed in the conflict. During the nationwide uprisings against the Ba'athist Iraqi government that directly followed the end of the Gulf War in March and April, an estimated 25,000 to 100,000 Iraqis were killed, overwhelmingly civilians. A Harvard University study released in June 1991 predicted that there would be tens of thousands of additional Iraqi civilian deaths by the end of 1991 due to the "public health catastrophe" caused by the destruction of the country's electrical generating capacity.
Professor of Chemistry and Biochemistry at the University of Colorado at Boulder, whose research is focussed on understanding the mechanisms of cell signalling, with a speciality in phosphorylation and cancers. Member Natl. Acad. Sci. USA.
=== Metric ounce === A metric ounce is an approximation of the imperial ounce, US dry ounce, or US fluid ounce. These three customary units vary. However, the metric ounce is usually taken as 25 or 30 ml (0.88 or 1.06 imp fl oz; 0.85 or 1.01 US fl oz) when volume is being measured, or in grams when mass is being measured. The US Food and Drug Administration (FDA) defines the "food labeling ounce" as 30.0 ml (1.06 imp fl oz; 1.01 US fl oz), slightly larger than the 29.6 ml (1.04 imp fl oz; 1.00 US fl oz) fluid ounce. Several Dutch units of measurement have been replaced with informal metric equivalents, including the ons or ounce. It originally meant 1⁄16 of a pound, or a little over 30 g (1.1 oz) depending on which definition of the pound was used, but was redefined as 100 g (3.5 oz) when the country metricated.
== Drug overdose and management == Cardiovascular agents generally have narrow therapeutic indices, implying that small differences in dose or blood concentration may give rise to adverse drug reactions. Serious acute toxicity may result from accidental, intentional or iatrogenic overdose. Therefore, patients need to be aware of any unusual and serious side effects. Seek immediate medical attention if a drug overdose is suspected.
Sources: en.wikipedia.org
== History == The code name "Looking Glass" came from the aircraft's ability to "mirror" the command and control functions of the underground command post at the U.S. Air Force's Strategic Air Command (SAC) headquarters at Offutt AFB, Nebraska.
The exact dose of lithium given varies depending on factors such as the patient's serum lithium concentrations, which must be closely monitored by a physician to avoid lithium toxicity and potential kidney damage (or even kidney failure) from lithium-induced nephrogenic diabetes insipidus. Dehydration and certain drugs, including NSAIDs such as ibuprofen, can increase serum lithium concentrations to unsafe levels whereas other drugs, such as caffeine, may decrease concentrations.
Raleigh receives an average of 5.2 in (13.2 cm) of snow in winter. Freezing rain and sleet also occur most winters, and occasionally the area experiences a major damaging ice storm. On January 24–25, 2000, Raleigh received its greatest snowfall from a single storm – 20.3 in (52 cm) – the Winter Storm of January 2000. Storms of this magnitude are generally the result of cold air damming that affects the city due to its proximity to the Appalachian Mountains. Winter storms have caused traffic problems in the past as well.
Sequence comparisons indicate an evolutionary relationship between gelsolin, villin, fragmin, and severin. Six large repeating segments occur in gelsolin and villin, and 3 similar segments in severin and fragmin. The multiple repeats are related in structure (but barely in sequence) to the ADF-H domain, forming a superfamily (InterPro: IPR029006). The family appears to have evolved from an ancestral sequence of 120 to 130 amino acid residues. Asgard archaea encode many functional gelsolins.
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.
Not necessarily. TB-500 is a commercial label that suppliers apply to synthetic peptides described as thymosin beta-4 or a fragment of it. Published research most often studies the full-length protein, so statements about one do not automatically transfer to the other.