The short version of thymosin beta-4 fragment fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-01-14 and is reviewed periodically as new material appears.
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.
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 | 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 |
Discussion of TB-500 appears in several distinct literatures that rarely cite one another. Peer-reviewed studies usually describe in vitro assays or small animal experiments and are cautious about extrapolation. Veterinary and sports communities circulate anecdotal reports with limited methodological detail. Commercial listings add a third layer, often using the name interchangeably with thymosin beta-4 even though the two molecules differ in size and sequence. Regulatory status varies by country, and the compound is not a licensed medicine in most jurisdictions, so readers comparing sources should check which molecule and which purity each source actually describes.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
Thymosin beta-4 itself is a small, widely expressed protein that sequesters monomeric actin and participates in cell migration, angiogenesis, and tissue repair. Researchers have examined the shortened fragment as a possible mimic of some of these activities, reasoning that the actin-binding motif lies within the first few residues. Binding to monomeric actin has been observed in cell-free systems. Whether the fragment reproduces the broader effects of the full protein in living tissue remains an open question, and findings from animal models are frequently cited without a clear bridge to human physiology.
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.
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.
TB-500 is a research peptide whose sequence matches residues 17 to 23 of thymosin beta-4, a 43-residue protein present in most mammalian cells. The chain is seven amino acids long, written as LKKTETQ, and is normally supplied with an acetyl group on the N-terminus. Suppliers list it as a lyophilised powder under the code name TB-500, and the same sequence appears elsewhere in catalogues as the thymosin beta-4 actin-binding fragment. The label is commercial rather than systematic, so no single authority fixes exactly what TB-500 denotes.
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.
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.
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.
== Clinical significance == Homozygous mutations, heterozygous compound (bi-allelic) mutations or haploinsufficiency in TN-X cause classical-like Ehlers–Danlos syndrome (EDS), a rare and hereditary connective tissue disorder in mice and humans. This pathology is characterized by skin hyperlaxity, joint hypermobility and global tissue weakness as a consequence of elastin fragmentation and reduced collagen density, especially in skin.
Vortioxetine, sold under the brand names Trintellix (in the US) and Brintellix (in Europe) among others, is an antidepressant medication of the serotonin modulator and stimulator (SMS) class used in the treatment of major depressive disorder. Its effectiveness is viewed as similar to that of other antidepressants. It is taken orally. Common side effects include nausea, dry mouth, diarrhea, constipation, vomiting (3-6% of people), and sexual dysfunction. Serious side effects may include suicide in those under the age of 25, serotonin syndrome, bleeding, mania, and SIADH. A withdrawal syndrome may occur if the medication is abruptly stopped or the dose is decreased. Use during pregnancy and breastfeeding is not generally recommended. Vortioxetine's mechanism of action is not entirely understood, but is believed to be related to increasing serotonin levels and possibly interacting with certain serotonin receptors. It was approved for medical use in the United States and in the European Union in 2013. In 2020, it was the 243rd most commonly prescribed medication in the United States, with more than 1 million prescriptions.
Due to his high popularity, Duterte remained influential before the national elections as several presidential candidates were open to his endorsement. As the Cusi faction was left without a standard bearer following Go's withdrawal, allies of Duterte endorsed different candidates. The Cusi faction eventually endorsed presidential candidate Marcos and some officials called for Duterte to do the same. Stressing he would remain neutral, Duterte refused to heed their calls and insisted on endorsing only Sara as vice president and 17 senatorial candidates. Additionally, in an effort to protect their integrity, Duterte barred his Cabinet members from campaigning for any candidate. Despite non-endorsement, Duterte hinted on the next president's preferred qualities: decisive, compassionate, a good judge of a person, and preferably, a lawyer; this led a PDP-Laban official to believe Duterte gave a "virtual endorsement" for Vice President Leni Robredo, who was Marcos' chief rival in the presidential race. In March 2022, Go said Duterte briefly met with Marcos and gave him advice on the presidency, but could not say whether Duterte gave Marcos an endorsement.
Contemporary global warming is driven by human activities, despite claims that it is not occurring, lacks strong scientific consensus, or that warming is mostly caused by non-human factors. No scientific body of national or international standing disagrees with the decades-old, near-complete scientific consensus on climate change. Global warming is primarily a result of the increase in atmospheric greenhouse gas concentrations (like CO2 and methane) via the burning of fossil fuels as well as other human activities such as deforestation, with secondary climate change feedback mechanisms (such as the melting of the polar ice increasing the Earth's absorption of sunlight) assisting to perpetuate the change. Global warming is not caused by the hole in the ozone layer. Ozone depletion is a separate problem caused by chlorofluorocarbons (CFCs) which have been released into the atmosphere. CFCs are strong greenhouse gases; however, the hole in the ozone layer is shrinking and in 2019 was the smallest it had been since 1982, while global warming continues. Cooling towers in power stations and other facilities do not emit smoke, harmful fumes, or radiation; they emit water vapor and do not contribute to climate change. Nuclear power is one of the safest sources of energy, resulting in orders of magnitude fewer deaths than conventional power sources per unit of energy produced. Extremely few people are killed or injured due to nuclear power on a yearly basis. (See also: Radiophobia) Earthquake strength (or magnitude) is not commonly measured using the Richter scale.
Ajahn Brahm agrees, writing that the main purpose of dependent origination is to explain "how there can be rebirth without a soul" and "why there is suffering, and where suffering comes to an end." Brahm cites the definitions of the nidanas in the Vibhaṅgasutta (SN 12.2) which clearly indicate that birth and death is meant literally. According to Brahm,Paṭicca-samuppāda shows the empty process, empty of a soul that is, which flows within a life and overflows into another life. It also shows the forces at work in the process, which drive it this way and that, even exercising sway in a subsequent life. Dependent origination also reveals the answer to how kamma done in a previous life can affect a person in this life. Brahm argues that there are two parallel processes at work in dependent origination (which are really one process looked at from different angles), one is delusion and kamma leading to rebirth consciousness (nidanas # 1 – 3) and the other is craving and clinging leading to existence and rebirth (# 8 – 11). Brahm describes this as follows: "deluded kamma and craving produce the fuel which generates existence and rebirth (into that existence), thereby giving rise to the start of the stream of consciousness that is at the heart of the new life." Furthermore, dependent origination explains rebirth without appeal to an unchanging self or soul (atman). Paul Williams sees dependent origination as closely connected with the doctrine of not-self (anatman) which rejects the idea there is an unchanging essence that moves across lives.
Sources: en.wikipedia.org
Federal agencies in the United States, such as the National Institute of Health (NIH) and National Science Foundation (NSF), have also funded research that pertains to best practices in teaching and learning of neuroscience concepts.
=== Story === For the first year of development, the team focused mostly on the gameplay without narrative structure. Playtesters found the game fun but asked about what these test chambers were leading towards. This prompted the team to come up with a narrative for Portal. The team worked with Marc Laidlaw, the writer of the Valve's Half-Life series, to fit Portal into the Half-Life universe. This was done in part because of the project's limited art resources; instead of creating art assets for Portal, the team reused the Half-Life 2 assets. Laidlaw opposed the crossover, feeling it "made both universes smaller", and said later: "I just had to react as gracefully as I could to the fact that it was going there without me. It didn't make any sense except from a resource-restricted point of view." Valve hired Erik Wolpaw and Chet Faliszek to write Portal. Wolpaw felt that the constraints improved the game. The concept of a computer AI guiding the player through experimental facilities to test the portal gun was arrived at early in the writing process. They drafted early lines for a "polite" AI with humorous situations, such as requesting the player's character to "assume the party escort submission position", and found this style of approach to be well-suited to the game they wanted to create, leading to the creation of the GLaDOS character. GLaDOS was central to the plot.
Flushing (serotonin itself does not cause flushing). Potential causes of flushing in carcinoid syndrome include bradykinins, prostaglandins, tachykinins, substance P, and/or histamine, diarrhea, and heart problems. Because of serotonin's growth-promoting effect on cardiac myocytes, a serotonin-secreting carcinoid tumour may cause a tricuspid valve disease syndrome, due to the proliferation of myocytes onto the valve. Diarrhea Wheezing Abdominal cramping Peripheral edema The outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency. Niacin deficiency, also known as pellagra, is associated with dermatitis, dementia, and diarrhea. This constellation of symptoms is called carcinoid syndrome or (if acute) carcinoid crisis. Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. The most common originating site of carcinoid is the small bowel, particularly the ileum; carcinoid tumors are the most common malignancy of the appendix. Carcinoid tumors may rarely arise from the ovary or thymus. They are most commonly found in the midgut at the level of the ileum or in the appendix. The next most commonly affected area is the respiratory tract, with 28% of all cases—per PAN-SEER data (1973–1999). The rectum is also a common site.
Italian forces entered British Somaliland from Abyssinia on 4 August 1940, overcame the garrison at Hargeisa, and advanced north-east towards the capital Berbera. The British force, including a platoon of 43 Rhodesians in the 2nd Battalion of the Black Watch, took up positions on six hills overlooking the only road towards Berbera and engaged the Italians at the Battle of Tug Argan. Amid heavy fighting, the Italians gradually made gains and by 14 August had almost pocketed the Commonwealth forces. The British retreated to Berbera between 15 and 17 August, the Rhodesians making up the left flank of the rearguard, and by 18 August had evacuated by sea. The Italians took the city and completed their conquest of British Somaliland a day later. No. 237 Squadron embarked on reconnaissance flights and supported ground assaults on Italian desert outposts during July and August 1940. Two British brigades from West Africa arrived to reinforce Kenya's northern frontier in early July—the partly Rhodesian-officered Nigeria Regiment joined the front at Malindi and Garissa, while a battalion of the Gold Coast Regiment, also with Rhodesian commanders attached, relieved the KAR at Wajir. The British forces in East Africa adopted the doctrine of "mobile defence" that was already being used in the Western Desert in North Africa—units embarked on long, constant patrols to guard wells and deny water supplies to the Italians. The British evacuated their north forward position at Buna in September 1940, and expected an attack on Wajir soon after, but the Italians never attempted an assault.
== External links == "Astragalus membranaceus – Moench". Plants for a Future. "Astragalus membranaceus (FISCH. EX LINK) BUNGE – Fabaceae". Dr. Duke's Phytochemical and Ethnobotanical Databases. ARS / GRIN. Archived from the original on 2004-11-15.
Sources: en.wikipedia.org
=== Non-canonical consensus motif === As a first non-canonical consensus motif targeted by CK1δ the so-called SLS motif (Ser-Leu-Ser) has been described, which can be found in β-catenin and nuclear factor of activated T-cells (NFAT). In several sulfatide and cholesterol-3-sulfate (SCS)-binding proteins the consensus motif Lys/Arg-X-Lys/Arg-X-X-Ser/Thr has been identified and phosphorylation of this motif has been demonstrated for myelin basic protein (MBP), the Ras homolog family member A (RhoA), and tau.
It is not known how mature RALF peptide is produced from its precursor, but a dibasic amino acid motif (typical of recognition sites of processing enzymes in yeast and animals) is located two residues upstream from the amino terminus of mature RALF. RALF has been identified to bind to potential membrane bound receptors complex containing proteins 25 kDa and 120 kDa in size. SCR/SP11 — are small polymorphic peptides produced by the tapetal cells of anthers and is involved in self-incompatibility of Brassica species. This secreted polypeptide is between 78 and 80 amino acid residues in length. Unlike other peptide hormones, no further post-translational processing occurs, except for the removal of the N-terminal signal peptide. SCR/SP11 like other small peptide hormones binds to a membrane bound LRR receptor like kinase (SRK). ROTUNDIFOLIA4/DEVIL1 (ROT4/DVL1) — The ROT4 and DVL1 are peptides of 53 and 51 amino acids respectively, which have a high degree of sequence homology. They are two members of 23 member peptide family. ROT4 and DVL1 are involved in regulating polar cell proliferation on the longitudinal axis of organs. Inflorescence deficient in abscission (IDA) — a family of secreted peptides identified to be involved in petal abscission. The peptides are 77 amino acids in length and possess an amino-terminal secretions signal. Like the CLE peptide family these proteins have a conserved carboxy-terminal domain that is bordered by potentially cleavable basic residues. These proteins are secreted from cells in the floral abscission zone.
=== Parvocellular neurosecretory neurons === The axons of the parvocellular neurosecretory neurons of the PVN project to the median eminence, a neurohemal organ at the base of the brain, where their neurosecretory nerve terminals release their hormones at the primary capillary plexus of the hypophyseal portal system. The median eminence contains fiber terminals from many hypothalamic neuroendocrine neurons, secreting different neurotransmitters or neuropeptides, including vasopressin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), growth hormone-releasing hormone (GHRH), dopamine (DA) and somatostatin (growth hormone release inhibiting hormone, GIH) into blood vessels in the hypophyseal portal system. The blood vessels carry the peptides to the anterior pituitary gland, where they regulate the secretion of hormones into the systemic circulation. The parvocellular neurosecretory cells include those that make:
Flexibility is the anatomical range of movement in a joint or series of joints, and length in muscles that cross the joints to induce a bending movement or motion. Flexibility varies between individuals, particularly in terms of differences in muscle length of multi-joint muscles. Flexibility in some joints can be increased to a certain degree by exercising, with stretching being a common exercise component to maintain or improve flexibility. Limberness is the condition of having flexibility to a positive or superior degree, which is also spoken of as a person having flexibility or being flexible.
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.
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.