This is a working overview of thymosin beta-4, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-05-03 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.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
| 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 |
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
Identity and purity are checked with reversed-phase high-performance liquid chromatography, which separates the target sequence from truncated or deletion analogues, and with mass spectrometry, which confirms the expected molecular mass. Amino acid analysis and peptide mapping give orthogonal confirmation but are used less often outside specialist laboratories. Counter-ion content varies: material purified on trifluoroacetic acid gradients retains trifluoroacetate, and ion exchange can convert the salt form. Residual water and solvent are measured by Karl Fischer titration or thermogravimetric analysis, and any purity figure should be read together with the method used to obtain it.
Lyophilised peptide powders are hygroscopic, and the fragment absorbs atmospheric moisture when a vial is opened at room temperature. Weighing and aliquoting are normally done quickly in a dry environment, and stock solutions are divided into single-use portions before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and can shift the measured content of a vial. These practices are general to synthetic peptides rather than unique to this sequence, but they matter more for short chains kept for long periods.
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.
1848: American astronomer Maria Mitchell became the first woman elected to the American Academy of Arts and Sciences; she had discovered a new comet the year before. 1848–1849: English scientist Mary Anne Whitby, a pioneer in western silkworm cultivation, collaborated with Charles Darwin in researching the hereditary qualities of silkworms. 1850: The American Association for the Advancement of Sciences accepted its first women members: astronomer Maria Mitchell, entomologist Margaretta Morris, and science educator Almira Hart Lincoln Phelps.
== Personal life == In 1971, Parsons married Gretchen Burrell (née Gretchen Lisl Berrill) at his stepfather's New Orleans estate. Parsons and Burrell went to England, where they visited their friend Ric Grech. With the help of Grech and his friend Hank Wangford, Parsons stopped using heroin. In the summer of 1973, Parsons' Topanga Canyon home burned to the ground, the result of a stray cigarette. Nearly all of his possessions were destroyed with the exception of a guitar and a prized Jaguar. The fire proved to be the last straw in the relationship between Burrell and Parsons, who moved into a spare room in Kaufman's house. Parsons rekindled his relationship with Margaret Fisher, a high school sweetheart from Waycross. Parsons had one child, born to Nancy Ross in 1967, Polly Parsons.
=== Differential Diagnosis === While Kwashiorkor is primarily characterized by edema, growth failure, and dermatitis, it can sometimes be misdiagnosed as Acrodermatitis Enteropathica (AE), as both conditions present with similar dermatological symptoms. However, AE is caused by zinc deficiency, not protein deficiency, and is associated with a significant decrease in serum zinc levels. Unlike kwashiorkor, which is diagnosed based on clinical signs like edema and low serum albumin levels, AE requires additional diagnostic tests, such as zinc uptake tests and genetic screening, to differentiate it from other disorders with similar symptoms. Therefore, while both conditions can present with dermatitis, the underlying etiology helps distinguish the two.
== Amino-acid preferences == One might expect that larger side chains would result in more restrictions and consequently a smaller allowable region in the Ramachandran plot, but the effect of side chains is small. In practice, the major effect seen is that of the presence or absence of the methylene group at Cβ. Glycine has only a hydrogen atom for its side chain, with a much smaller van der Waals radius than the CH3, CH2, or CH group that starts the side chain of all other amino acids. Hence it is least restricted, and this is apparent in the Ramachandran plot for glycine (see Gly plot in gallery) for which the allowable area is considerably larger. In contrast, the Ramachandran plot for proline, with its 5-membered-ring side chain connecting Cα to backbone N, shows a limited number of possible combinations of ψ and φ (see Pro plot in gallery). The residue preceding proline ("pre-proline") also has limited combinations compared to the general case.
=== Other African countries === Nando's has been operating in Botswana since 1993. There are 19 restaurants in Botswana; 10 in Gaborone, two in Francistown and Palapye, and one each in Jwaneng, Maun, Mahalapye, Kasane and Letlhakane. There are four outlets in Eswatini; in Mbabane, Matsapha, Ezulwini and Manzini (2022). There are six Nando's restaurant outlets in Mauritius, in Curepipe, Grand-Baie, Moka, Riche Terre, Cascavelle and Vacoas-Phoenix. Nando's began operating in Zambia in 2002. As of August 2021, Nando's has nine restaurants in Zambia; seven in Lusaka and one each in Ndola and Kitwe. Nando's has been operating in Zimbabwe since 1995. As of August 2021, Nando's has 14 restaurants in Zimbabwe; nine in Harare and one each in Bulawayo, Mutare, Gweru, Kwekwe and Victoria Falls.
Sources: en.wikipedia.org
Members of the group held no voting privileges, so they could not affect the outcome of the parent group. The Order evolved into other fraternal groups during the 1920s. Teepee Order of America - Founded in 1915 by Red Fox Francis St. James, an alleged Blackfoot Indian. Open to Indians and non-Indians from the US, Canada, and Latin America, it excluded blacks and European immigrants. Originally similar to the Boy Scouts of America in appealing to youth and "focusing on Indian activities and ceremonies that were romantic in nature." It was a Pan-Indian group, but not as successful as the Society of American Indians, though there was some membership overlap. It advocated for Native American citizenship and questioned the efficacy of the Bureau of Indian Affairs.
=== Treatment and telemedicine === Providing treatment including prescribing medications based on remote information gathering without a proper established relationship is not accepted as good practice with few exceptions. These exceptions include cross-coverage within a practice and certain public health urgent or emergent issues. The ethics of telemedicine including questions on its impact to diagnosis, doctor-patient relationship, and continuity of care have been raised. However, with appropriate use and specific guidelines, risks may be minimized and the benefits including increased access to care may be realized.
=== Contrast properties === Neutron scattering techniques particularly profit from availability of deuterated samples: The 1H and 2H cross sections are very distinct and different in sign, which allows contrast variation in such experiments. Further, a nuisance problem of normal hydrogen is its large incoherent neutron cross section, which is nil for 2H. The substitution of deuterium for normal hydrogen thus reduces scattering noise. Hydrogen is an important and major component in all materials of organic chemistry and life science, but it barely interacts with X-rays. As hydrogen atoms (including deuterium) interact strongly with neutrons; neutron scattering techniques, together with a modern deuteration facility, fills a niche in many studies of macromolecules in biology and many other areas.
The total period of time beginning with the date of manufacture, date of cure (for elastomeric and rubber products only), date of assembly, or date of pack (subsistence only), and terminated by the date by which an item must be used (expiration date) or subjected to inspection, test, restoration, or disposal action; or after inspection/laboratory test/restorative action that an item may remain in the combined wholesale (including manufacture's) and retail storage systems and still be suitable for issue or use by the end user. Shelf-life is not to be confused with service-life (defined as, A general term used to quantify the average or standard life expectancy of an item or equipment while in use. When a shelf-life item is unpacked and introduced to mission requirements, installed into intended application, or merely left in storage, placed in pre-expended bins, or held as bench stock, shelf-life management stops and service life begins.)
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.
Dry lyophilized powder is usually kept frozen, desiccated, and out of direct light. Sealed vials are not opened until needed, because moisture uptake can degrade short peptides. Longer archival storage is often done at lower temperatures than routine working stock.