Everything below concerns TB-500. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-02-07. Where a claim depends on a specific study, the study is described rather than over-claimed.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Physical form | Lyophilised powder | Sealed vial; reconstituted before laboratory use |
| Appearance | White to off-white solid | Visual descriptor used on certificates of analysis |
| Solubility class | Water-soluble | Dissolves in water and aqueous buffers |
| Reported mass, fragment | Near 889 Da | Value depends on the stated sequence |
| Reported mass, parent protein | Near 4963 Da | 43-residue thymosin beta-4 |
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.
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.
Research peptides are typically supplied as a white to off-white lyophilised powder in a sealed vial. The dry solid is more stable than a solution and is normally kept refrigerated or frozen until use. Dissolution is usually done in water, phosphate-buffered saline or a similar aqueous medium, depending on the assay. Because the material is hygroscopic and easily contaminated, opening vials in a low-humidity environment and recording the lot number before use are standard laboratory practices.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
Purity is normally assessed by reversed-phase HPLC, with the main peak reported as a percentage of total peak area, while identity is confirmed by mass spectrometry. Electrospray and MALDI-TOF instruments are both used, and the observed mass is compared with the value calculated from the stated sequence. Ion-exchange or size-exclusion methods appear where aggregation or charge variants are of interest. Water content, counter-ion content and residual trifluoroacetate from purification are separate variables that can shift the measured mass and should be weighed when reading a certificate of analysis.
=== Intrauterine administration === A one-year progesterone intrauterine device (IUD) for hormonal birth control was previously available in the United States and a few other countries under the brand name Progestasert. It was marketed between 1976 and 2001. The IUD was never widely used due to a relatively high contraceptive failure rate of 2.9% and the requirement of annual replacement. It contained 38 mg progesterone and released 65 μg progesterone into the uterus per day (totaling up to about 35 mg after one year). For comparison, a woman's body produces on average about 25 mg progesterone per day during the luteal phase. While effective as a form of contraception and for decreasing menstrual bleeding and discomfort, long-lived IUDs can fundamentally only deliver small amounts of progesterone per day, and hence intrauterine progesterone cannot achieve adequate circulating progesterone levels and is unsuitable as a form of systemic therapy. Aside from progesterone, IUDs of progestins, such as levonorgestrel (Mirena/Levosert/Skyla), are available as well.
=== 24 March === The RSF launched a series of attacks in eastern Khartoum, killing at least five people and injuring dozens. At the same time, the group retreated from the Salama, Azhari, Ad Hussein, Mayo, Gereif West, Burri, Sahafat and Kalakla neighbourhoods of Khartoum and were seen moving south towards Jebel Aulia. The Darfur Initiative for Justice and Peace said that hundreds of civilians were killed in an SAF airstrike on the Tur'rah market near El Fasher.
=== Hair loss disorder === The first LLLT (low-level laser device) device (at a wavelength of 635 nm) for androgenetic alopecia was approved by the FDA two decades ago. The FDA then approved a similar device (at a wavelength of 655 nm) for alopecia two years later, in 2009. Low-level laser therapy (LLLT) is the traditional FDA-approved therapy for hair loss disorders, while LEDT has become a more advanced treatment due to its safety and efficacy. The commonly used wavelengths targeting hair loss disorder are red and infrared. In-vivo studies show that the red-light LEDT at the wavelength of 655 nm contributes to dramatic improvements in the hair counts of androgenetic alopecia patients. A more recent study indicates a similar therapeutic effect of yellow-light LEDT on androgenetic alopecia and alopecia areata patients.
== Food sources == Nicotinamide occurs in trace amounts mainly in meat, fish, nuts, and mushrooms, as well as to a lesser extent in some vegetables. It is commonly added to cereals and other foods. Many multivitamins contain 20–30 mg of vitamin B3, and it is also available in higher doses.
Sources: en.wikipedia.org
== Literature == Michael Bliss: Theodore Ryder: The Last Living Link to the Discovery of Insulin. In: Practical Diabetes International. 12(4)/1995. John Wiley & Sons, S. 187–188, ISSN 1357-8170 Katharine Martyn: Teddy Ryder's Scrapbook. In: The Halcyon. The Newsletter of the Friends of the Thomas Fisher Library. Ausgabe 24, November 1999; online under Teddy Ryder's Scrapbook
Association between HLA and Sjögren’s is restricted to patients with anti-SSA/Ro or anti-SSB/La antibodies. Seropositivity for anti-Ro and anti-La is associated with greater severity and longer duration of disease, and findings of their high abundance from the salivary glands of Sjögren's patients suggests their imperative role in the pathogenesis of Sjögren’s. Beyond genetics, epigenetic abnormality related to DNA methylation, histone acetylation, or microRNA expression probably has a key role in the pathogenesis of autoimmune diseases, including Sjögren's disease. However, research in this area is very limited.
Cooper's ligaments (also known as the suspensory ligaments of Cooper and the fibrocollagenous septa) are connective tissue in the breast that help maintain structural integrity. They are named for Astley Cooper, who first described them in 1840. Their anatomy can be revealed using transmission diffraction tomography. Cooper's suspensory ligament should not be confused with the pectineal ligament (sometimes called the inguinal ligament of Cooper) which shares the same eponym. Also, the intermediate fibers and/or the transverse part of the ulnar collateral ligament are sometimes called Cooper's ligament(s).
Sources: en.wikipedia.org
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.
Naming for research peptides is not standardised, and suppliers sometimes apply the same label to different chain lengths. Certificates of analysis and mass data are the practical way to determine what a given lot contains.
The fragment commonly cited under this label is reported near 889 Da, and the parent protein near 4963 Da. Reported values shift with the exact sequence and with residual counter-ions or water in the sample.
Standard practice is a desiccated container at −20 °C, protected from light and kept sealed between uses. Letting the vial reach room temperature before opening reduces condensation on the powder. Repeated warming and cooling of the whole container is generally avoided.