This is a working overview of TB-500, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-09. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
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.
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.
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.
=== Monitoring response to therapy === The clinical usefulness of ESR is limited to monitoring the response to therapy in certain inflammatory diseases such as temporal arteritis, polymyalgia rheumatica and rheumatoid arthritis. It can also be used as a crude measure of response in Hodgkin's lymphoma. Additionally, ESR levels are used to define one of the several possible adverse prognostic factors in the staging of Hodgkin's lymphoma.
The formation of the peptide bond consumes energy, which, in organisms, is derived from ATP. Peptides and proteins are chains of amino acids held together by peptide bonds (and sometimes by a few isopeptide bonds). Organisms use enzymes to produce nonribosomal peptides, and ribosomes to produce proteins via reactions that differ in details from dehydration synthesis. Some peptides, like alpha-amanitin, are called ribosomal peptides as they are made by ribosomes, but many are nonribosomal peptides as they are synthesized by specialized enzymes rather than ribosomes. For example, the tripeptide glutathione is synthesized in two steps from free amino acids, by two enzymes: glutamate–cysteine ligase (forms an isopeptide bond, which is not a peptide bond) and glutathione synthetase (forms a peptide bond).
== Disadvantages == There are some concerns about how physicians can be sure that all of the drug or vaccine has entered the skin when microneedles are applied. Hollow and coated microneedles both possess the risk that the drug will not properly enter the skin and will not be effective. Both of these types of microneedles can leak onto a person's skin either by damage of the microneedle or incorrect application by the physician. This is why it is essential that physicians are trained how to properly apply the arrays. Another concern is that incorrectly applied arrays could leave foreign material in the body. Although there is a lower risk of infection associated with microneedles, the arrays are more fragile than a typical hypodermic needle due to their small size and thus have a chance of breaking off and remaining in the skin. Some of the material used to construct the microneedles, such as titanium, cannot be absorbed by the body and any fragments of the needles would cause irritation. There is a limited amount of literature available on the subject of microneedle drug delivery, as current research is still exploring how to make effective needles. In terms of design and manufacture, low drug loading is a key barrier towards reaching the clinics.
=== Molecular and genetic changes === UVB rays are a primary mutagen that can only penetrate through the epidermal (outermost) layer of the skin and can cause DNA mutations. These mutations arise due to chemical changes within skin cells. These mutations may be clinically related to specific signs of photoaging, including wrinkling.
Sources: en.wikipedia.org
Extracellular matrix has been found to cause regrowth and healing of tissue. Although the mechanism of action by which extracellular matrix promotes constructive remodeling of tissue is still unknown, researchers now believe that Matrix-bound nanovesicles (MBVs) are a key player in the healing process. In human fetuses, for example, the extracellular matrix works with stem cells to grow and regrow all parts of the human body, and fetuses can regrow anything that gets damaged in the womb. Scientists have long believed that the matrix stops functioning after full development. It has been used in the past to help horses heal torn ligaments, but it is being researched further as a device for tissue regeneration in humans. In terms of injury repair and tissue engineering, the extracellular matrix serves two main purposes. First, it prevents the immune system from triggering from the injury and responding with inflammation and scar tissue. Next, it facilitates the surrounding cells to repair the tissue instead of forming scar tissue. For medical applications, the required ECM is usually extracted from pig bladders, an easily accessible and relatively unused source. It is currently being used regularly to treat ulcers by closing the hole in the tissue that lines the stomach, but further research is currently being done by many universities as well as the U.S. Government for wounded soldier applications. As of early 2007, testing was being carried out on a military base in Texas. Scientists are using a powdered form on Iraq War veterans whose hands were damaged in the war.
== Spatial xenon oscillations == Large thermal reactors with low flux coupling between regions may experience spatial power oscillations because of the non-uniform presence of xenon-135. Xenon-induced spatial power oscillations occur as a result of rapid perturbations to power distribution that cause the xenon and iodine distribution to be out of phase with the perturbed power distribution. This results in a shift in xenon and iodine distributions that causes the power distribution to change in an opposite direction from the initial perturbation. The instantaneous production rate of xenon-135 is dependent on the iodine-135 concentration and therefore on the local neutron flux history. On the other hand, the destruction rate of xenon-135 is dependent on the instantaneous local neutron flux. The combination of delayed generation and high neutron-capture cross section produces a diversity of impacts on nuclear reactor operation. The mechanism is described in the following four steps.
== Pharmacology == Pramlintide is an analogue of amylin, a small peptide hormone that is released into the bloodstream by the β cells of the pancreas along with insulin after a meal. Like insulin, amylin is completely absent in individuals with Type I diabetes. In synergy with endogenous amylin, pramlintide aids in the regulation of blood glucose by slowing gastric emptying, promoting satiety via hypothalamic receptors (different receptors than for GLP-1), and inhibiting inappropriate secretion of glucagon, a catabolic hormone that opposes the effects of insulin and amylin. Pramlintide also has effects in raising the acute first-phase insulin response threshold following a meal. Both a reduction in glycated hemoglobin and weight loss have been shown in insulin-treated patients with type 2 diabetes taking pramlintide as an adjunctive therapy.
== Biological significance == In general, most biochemical reactions are stereoselective, so only one stereoisomer will produce the intended product while the other simply does not participate or can cause side-effects. Of note, the L form of amino acids and the D form of sugars (primarily glucose) are usually the biologically reactive form. This is due to the fact that many biological molecules are chiral and thus the reactions between specific enantiomers produce pure stereoisomers. Also notable is the fact that all amino acid residues exist in the L form. However, bacteria produce D-amino acid residues that polymerize into short polypeptides which can be found in bacterial cell walls. These polypeptides are less digestible by peptidases and are synthesized by bacterial enzymes instead of mRNA translation which would normally produce L-amino acids. The stereoselective nature of most biochemical reactions meant that different enantiomers of a chemical may have different properties and effects on a person. Many psychotropic drugs show differing activity or efficacy between isomers, e.g. amphetamine is often dispensed as racemic salts while the more active dextroamphetamine is reserved for refractory cases or more severe indications; another example is methadone, of which one isomer has activity as an opioid agonist and the other as an NMDA antagonist. Racemization of pharmaceutical drugs can occur in vivo.
Potassium is a chemical element; it has symbol K (from Neo-Latin kalium) and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge (which combines with anions to form salts). In nature, potassium occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in seawater (which is 0.04% potassium by weight), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks. Potassium is chemically very similar to sodium, the previous element in group 1 of the periodic table. They have a similar first ionization energy, which allows for each atom to give up its sole outer electron. It was first suggested in 1702 that they were distinct elements that combine with the same anions to make similar salts, which was demonstrated in 1807 when elemental potassium was first isolated via electrolysis. Naturally occurring potassium is composed of three isotopes, of which 40K is radioactive.
Sources: en.wikipedia.org
Many brain functions can be influenced at the cellular and molecular level by variations and changes in gene expression, without altering the sequence of DNA in an organism. This is otherwise known as epigenetic regulation. Examples of epigenetic mechanisms include histone modifications and DNA methylation. Such changes have been found to be strongly influential in the incidence of brain disease, mental illness, and addiction. Epigenetic control has been shown to be involved in high levels of plasticity in early development, thereby defining its importance in the critical period of an organism. Examples of how epigenetic changes can affect the human brain are as follows:
== Function == The edited region contains a proposed heparin binding site and is also part of the recognition sequence for proteolytic cleavage. Heparin binding inhibits cell binding and cell adhesion functions of the protein. Cleavage which occurs at amino acid position 97 reduces heparin binding but modulates the growth stimulatory activity of the protein. Since the editing site occurs within this proposed heparin binding region the effects of editing may have implications for heparin binding and proteolytic cleavage and therefore have other affects downstream. Since the protein has been implicated in these processes it is believed editing might effect apoptosis, regulation of cell growth and angiogenesis.
Representatives of member and observer countries meet in specialised committees on specific policy areas, such as economics, trade, science, employment, education, development assistance or financial markets. There are about 200 committees, working groups and expert groups. Committees discuss policies and review progress in the given policy area.
== Nomenclature == The name γ-glutamyltransferase is preferred by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. The Expert Panel on Enzymes of the International Federation of Clinical Chemistry also used this name. The older name is gamma-glutamyl transpeptidase (GGTP).
Activation energies consistent with proline isomerization, which typically has an activation of about 20 kcal/mol. Two-state folding kinetics indicative of both fast-folding and slow-folding populations in the unfolded or denatured state. "Double-jump" assays in which proline-containing proteins are unfolded and refolded, and the population of non-native proline conformations are studied as a function of the extent of folding. Acceleration of the in vitro folding rate by the addition of a prolyl isomerase. Acceleration of the in vitro folding rate in mutant protein variants with one or more proline residues replaced by another amino acid. Not every proline peptide bond is critical to the structure or function of a protein, and not every such bond has a significant influence on folding kinetics, especially trans bonds. Furthermore, some prolyl isomerases have a degree of sequence specificity and therefore may not catalyze the isomerization of prolines in certain sequence contexts.
Sources: en.wikipedia.org
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.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
Desiccated storage at −20 °C is conventional, with −80 °C for extended periods. Vials should be warmed to room temperature before opening to prevent condensation on the powder.