The short version of TB-500 fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-01-21 and is reviewed periodically as new material appears.
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.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
| Property | Value | Notes |
|---|---|---|
| Purity determination | Reversed-phase HPLC | UV detection commonly at 214 nm |
| Mass confirmation | Mass spectrometry | Compared against theoretical 888.5 Da |
| Powder storage | -20 C or below | Dry and protected from light |
| Reconstituted storage | Aliquoted and frozen | Avoid repeated freeze-thaw cycles |
| Reconstitution solvent | Sterile water or neutral buffer | Avoid extreme pH conditions |
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.
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.
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.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
=== Etymology === Lactobacillic acid and Lactobacillussäure are translations of the English term 'lactobacillic acid', which scientists proposed when this fatty acid was discovered (1950) in a Lactobacillus species. In the German-language literature, the term lactobacillic acid is used more frequently than lactobacillus acid. As early as 1938, another group of researchers discovered an unusual fatty acid from the bacterium Agrobacterium tumefaciens (at that time called Bacterium tumefaciens or Phytomonas tumefaciens) was isolated and after the generic name as phytomonic acid. According to the knowledge of scientists at the time, this saturated fatty acid had the molecular formula C20H40O2. The proposed structure was a branched-chain fatty acid with a methyl group as a branch, methylnonadecanoic acid. However, K. Homann et al. were able to show in 1955 that this compound isolated from P. tumefaciens was in fact lactobacillic acid. According to them, the substance originally investigated had been contaminated.
On the less mountainous islands, the raising of sheep and reindeer was once believed to be practicable. There are bison on islands near Sand Point. Sheep raising seems to have died off with the advent of synthetic fibers, which lowered the value of wool. During the 1980s, there were some llama being raised on Unalaska. The current economy is primarily based on fishing, and the presence of U.S. military. The only crop is potato. Chickens are raised in barns under protection from the cold.
=== Gene regulation === Crystallin recruitment may occur by changes in gene regulation that leads to high lens expression. One such example is gluthathione S-transferase/S11-crystallin that was specialized for lens expression by change in gene regulation and gene duplication. The fact that similar transcriptional factors such as Pax-6, and retinoic acid receptors, regulate different crystalline genes, suggests that lens-specific expression have played a crucial role for recruiting multifunctional protein as crystallins. Crystallin recruitment has occurred both with and without gene duplication, and tandem gene duplication has taken place among some of the crystallins with one of the duplicates specializing for lens expression. Ubiquitous α –crystallins and bird δ –crystallins are two examples.
diffusion The net movement of atoms or molecules from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in chemical potential of the diffusing species and depends on the random walk of particles; hence it results in mixing or mass transport without required directed bulk motion.
Sources: en.wikipedia.org
== External links == American Association for Clinical Chemistry American Society for Clinical Pathology American Board of Pathology College of American Pathologists European Federation of Clinical Chemistry and Laboratory Medicine Academy of Clinical Laboratory Physicians and Scientists
Svetlana Mojsov is a Yugoslav-born Macedonian American chemist who is a Lulu Chow Wang and Robin Chemers Neustein Research Professor at the Rockefeller University. Her research considers peptide synthesis. She discovered the glucagon-like peptide-1 (GLP-1) and uncovered its role in glucose metabolism and the secretion of insulin. Her breakthroughs were transformed by Novo Nordisk into therapeutic agents against diabetes and obesity.
The shoulder girdle was longer than the entire forelimb. The shoulder blade had a narrow shaft but was exceptionally expanded at its upper end. It connected via a long forward protrusion to the coracoid, which was rounded. Both shoulder blades were connected by a small furcula. The paired breast bones possibly were made of cartilage only. The forelimb or arm was very short. The upper arm bone, the humerus, was short but robust. It had a narrow upper end with an exceptionally rounded head. The lower arm bones, the ulna and radius, were straight elements, much shorter than the humerus. The second metacarpal was longer and wider than the first, whereas normally in theropods the opposite is true. The forelimbs had only two clawed fingers, along with an additional splint-like small third metacarpal representing the remnant of a third digit.
=== Mobility === People with mild (type I) OI as adults need few pieces of adaptive equipment, although in infancy they reach motor milestones at a significant delay compared to the general population. With adaptive equipment such as crutches, motorized wheelchairs, splints, reach extenders, and/or modifications to the home, many individuals with moderate to severe OI can achieve or maintain a significant degree of independence. With treatment and physical therapy, the maximum levels of mobility are expected to be unassisted community walking for type I, household or exercise walking for type III, and household or community walking for type IV; due to the variability of OI between individuals, mobility achieved varies and may be below this expected maximum.
== Structure and discovery == In 1902, Hermann Emil Fischer isolated hydroxyproline from hydrolyzed gelatin. In 1905, Hermann Leuchs synthesized a racemic mixture of 4-hydroxyproline. Hydroxyproline differs from proline by the presence of a hydroxyl (OH) group attached to the gamma carbon atom.
Sources: en.wikipedia.org
=== Osteoclast === Osteoclasts are very large multinucleate cells that are responsible for the breakdown of bones by the process of bone resorption. New bone is then formed by the osteoblasts. Bone is constantly remodeled by the resorption of osteoclasts and created by osteoblasts. Osteoclasts are large cells with multiple nuclei located on bone surfaces in what are called Howship's lacunae (or resorption pits). These lacunae are the result of surrounding bone tissue that has been reabsorbed. Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with phagocytic-like mechanisms similar to circulating macrophages. Osteoclasts mature and/or migrate to discrete bone surfaces. Upon arrival, active enzymes, such as tartrate-resistant acid phosphatase, are secreted against the mineral substrate. The reabsorption of bone by osteoclasts also plays a role in calcium homeostasis.
There are seven naturally occurring isotopes of thorium but none are stable. 232Th is the only isotope of thorium occurring in quantity in nature; its half-life is 14.0 billion years, about three times the age of the Earth, and slightly longer than the age of the universe, and longest of all nuclides heavier than bismuth. Its stability is attributed to its closed nuclear subshell with 142 neutrons. Thorium has a characteristic terrestrial isotopic composition, with atomic weight 232.0377±0.0004. It is one of only four radioactive elements (along with bismuth, protactinium and uranium) that occur in large enough quantities on Earth for a standard atomic weight to be determined. Thorium nuclei are susceptible to alpha decay because the strong nuclear force cannot overcome the electromagnetic repulsion between their protons. The alpha decay of 232Th initiates the 4n decay chain, or thorium series, which includes isotopes with a mass number divisible by 4. This chain of consecutive alpha and beta decays begins with the decay of 232Th to 228Ra and terminates at 208Pb. Any sample of thorium or its compounds contains traces of these daughters, which are isotopes of thallium, lead, bismuth, polonium, radon, radium, and actinium. Natural thorium samples can be chemically purified to extract useful daughter nuclides, such as 212Pb, which is used in nuclear medicine for cancer therapy. 227Th (alpha emitter, 18.693 days half-life) can also be used in cancer treatments such as targeted alpha therapies.
== Protein identification via sequence database searching == Sequence database searching is widely used currently for mass spectra based protein identification. In this approach, a protein sequence database is used to calculate all putative peptide candidates in the given setting (proteolytic enzymes, miscleavages, post-translational modifications). The sequence search engines use various heuristics to predict the fragmentation pattern of each peptide candidate. Such derivative patterns are used as templates to find a sufficiently close match within experimental mass spectra, which serves as the basis for peptide/protein identification. Many tools have been developed for this practice, which have enabled many past discoveries, e.g. SEQUEST, Mascot.
In September, the missile was fired at Israel and landed in an open area near Ben Gurion Airport, traveling a distance of 2,000 kilometres (1,200 mi) in 11 minutes. The Houthis claimed that the rocket used two stage solid fuel, had a range of 2,150 kilometres (1,340 mi), and had a maximum speed of Mach 16. Israel and the US denied that the missile was hypersonic.
=== Biocompatibility, biodegradability, and biodistribution === One major concern with any form of drug delivery system, including nanogels, is potential side effects and damage to healthy tissue in addition to causing a negative immune response with the introduction of a foreign substance. This has to be balanced with the need for nanogels to remain within circulation for an adequate period to deliver cargo and produce a therapeutic effect. To combat a significant immune response, degradable nanogels are the typical default since they are considered less toxic compared to non degradable nanogels. The compliance and small size of degradable nanogels also allows them to travel through blood vessels and reach their target area before consumption by immune cells or filtration by the liver and spleen.
Sources: en.wikipedia.org
The lyophilised powder is typically held at -20 C or lower in a dry, dark place. Reconstituted solutions are aliquoted and frozen to avoid repeated freeze-thaw cycles.
Mass spectrometry is the usual confirmatory method because it measures the intact mass. Reversed-phase chromatography is used alongside it to estimate purity.
Not directly. Reported percentages depend on the chromatographic method, detection wavelength, and integration criteria, so the underlying method details matter.
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.