The short version of heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-01-15. Anything still debated is marked as such rather than presented as settled.
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.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
| 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 |
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.
Lyophilised material is stable for extended periods when kept dry and cold, and suppliers typically recommend storage well below freezing. Once dissolved, the peptide is handled at refrigeration temperatures and used within a short period, because peptide bonds and the acetylated terminus can be affected by repeated freeze-thaw cycles, proteases, or extreme pH. Bacteriostatic water and saline are both described as solvents, although preservatives can interfere with some analytical workflows. Reconstituted solutions are inspected for particulates before use.
Sports authorities classify the peptide as a prohibited substance, and it appears on the World Anti-Doping Agency list under peptide hormones, growth factors, and related substances. Racing jurisdictions for horses and dogs have issued separate restrictions, and several national bodies treat it as a controlled or prescription-only item. As a research chemical it is sold without a therapeutic indication, and labels usually state that the product is not for human or veterinary use. Regulatory treatment therefore varies by country.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
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.
After completing her PhD, Dayhoff studied electrochemistry under Duncan A. MacInnes at the Rockefeller Institute from 1948 to 1951. In 1952, she moved to Maryland with her family and later received research fellowships from the University of Maryland (1957–1959), working on a model of chemical bonding with Ellis Lippincott. At Maryland, she gained her first exposure to a new high-speed computer, the IBM model 7094. After this ended, she joined the National Biomedical Research Foundation in 1960 as associate director (a position she held for 21 years). At the NBRF, she began to work with Robert Ledley, a dentist who had obtained a degree in physics and become interested in the possibilities of applying computational resources to biomedical problems. He had authored one of the earliest studies of biomedical computation, "Report on the Use of Computer in Biology and Medicine." With their combined expertise, they published a paper in 1962 entitled "COMPROTEIN: A computer program to aid primary protein structure determination" that described a "completed computer program for the IBM 7090" that aimed to convert peptide digests to protein chain data. They actually began this work in 1958, but were not able to start programming until late 1960.
On September 12–17, 2013, at the 2013 IBC Conference in Amsterdam, Nagra introduced an Ultra HD User Interface called Project Ultra based on HTML5, which works with OpenTV 5. On October 4, 2013, DigitalEurope announced the requirements for their UHD logo in Europe. The DigitalEurope UHD logo requires that the display support a resolution of at least 3840 × 2160, a 16∶9 aspect ratio, the Rec. 709 (HDTV) color space, 8 bpc color depth, a frame rate of 24, 25, 30, 50, or 60 fps, and at least 2-channel audio. On October 29, 2013, Elemental Technologies announced support for real-time 4K Ultra HD HEVC video processing. Elemental provided live video streaming of the 2013 Osaka Marathon on October 27, 2013, in a workflow designed by K-Opticom, a telecommunications operator in Japan. Live coverage of the race in 4K Ultra HD was available to viewers at the International Exhibition Center in Osaka. This transmission of 4K Ultra HD HEVC video in real-time was an industry-first. On November 28, 2013, Organizing Committee of the XXII Olympic Winter Games and XI Paralympic Winter Games 2014 in Sochi chief Dmitri Chernyshenko stated that the 2014 Olympic Winter Games would be shot in 8K Super Hi-Vision. On December 25, 2013, YouTube added a "2160p 4K" option to its videoplayer. Previously, a visitor had to select the "original" setting in the video quality menu to watch a video in 4K resolution. With the new setting, YouTube users can much more easily identify and play 4K videos.
=== Mask squeeze === If a diver's mask is not equalized during descent the relative negative internal pressure can produce petechial hemorrhages in the area covered by the mask along with subconjunctival hemorrhages.
Sources: en.wikipedia.org
Protein phosphorylation is a reversible post-translational modification of proteins in which an amino acid residue is phosphorylated by a protein kinase by the addition of a covalently bound phosphate group. Phosphorylation alters the structural conformation of a protein, causing it to become activated, deactivated, or otherwise modifying its function. Approximately 13,000 human proteins have sites that are phosphorylated. The reverse reaction of phosphorylation is called dephosphorylation, and is catalyzed by protein phosphatases. Protein kinases and phosphatases work independently and in a balance to regulate the function of proteins. The amino acids most commonly phosphorylated are serine, threonine, tyrosine, and histidine. These phosphorylations play important and well-characterized roles in signaling pathways and metabolism. However, other amino acids can also be phosphorylated post-translationally, including arginine, lysine, aspartic acid, glutamic acid and cysteine, and these phosphorylated amino acids have been identified to be present in human cell extracts and fixed human cells using a combination of antibody-based analysis (for pHis) and mass spectrometry (for all other amino acids). Protein phosphorylation was first reported in 1906 by Phoebus Levene at the Rockefeller Institute for Medical Research with the discovery of phosphorylated vitellin. However, it was nearly 50 years until the enzymatic phosphorylation of proteins by protein kinases was discovered.
Ford won an 36-seat majority in the 44th Ontario general election. Originally scheduled by election date laws to be held by June 4, 2026, Ford triggered an early provincial election, called a snap election, for February 27, 2025, after meeting with Ontario's lieutenant-governor.
== Exam preparation == AAB developed a two-day review program to help individuals prepare for the HEW Proficiency Examination, known as the “Proficiency Examination Reviews” or “PERs”. The notes used during the reviews were compiled into a reference manual that became the PER Handbook which continued into its tenth edition in 2016.
Sources: en.wikipedia.org
== External links == Media related to Counterfeit medications at Wikimedia Commons "Fake Prescription Pills". Drug Enforcement Administration (DEA). "Misuse of Prescription, Opioids, and Fake Pills". www.samhsa.gov. June 6, 2023.
==== Food ==== In the 1980s, W. R. Grace had owned the following restaurants: American Cafe, Del Taco, Coco's Bakery, El Torito, Hungry Tiger and various restaurants it had purchased from General Mills. In 1986, the company sold its restaurants and retained a 49 percent interest in the restaurant operations. The restaurant chains included Coco's, Houlihan's Old Place, Charley Brown's and Bristol Bar and Grill. The transaction also included El Torito Restaurants Inc., of which Grace had owned 73 percent. Charles H. Erhart Jr., vice chairman of Grace, said:While it is still too early to make a definitive estimate, we expect total proceeds to Grace to exceed $500 million from this transaction. In the process of leaving the restaurant business, the company later sold Del Taco to PepsiCo's Taco Bell in 1992.
=== March === 4 March – Banco Master scandal: The Supreme Federal Court orders the arrest of former Banco Master president and major shareholder Daniel Vorcaro in a potential fraud case worth up to 12 billion reais. The Federal Senate ratifies the EU–Mercosur Partnership Agreement. 5 March – A nursing home collapses in Belo Horizonte, killing eight people and leaving four missing. 10 March – Ski racer Cristian Ribera becomes the first athlete representing Brazil to win a medal in the Paralympics after achieving silver in the para-cross-country skiing men's seated sprint at the 2026 Winter Paralympics in Italy. 14 March – President Lula revokes the visa of US diplomat Darren Beattie after the latter tries to visit former president Jair Bolsonaro in prison. Three Israeli nationals are arrested after clashing with pro-Palestine demonstrators in Itacare. 17 March – A law restricting access to social media by minors comes into effect. 18 March – Eight people, including Comando Vermelho commander Claudio Augusto dos Santos, are killed in police raids across Rio de Janeiro. 20 March – Fernando Haddad resigns as finance minister after announcing that he would run for governor of Sao Paulo.
4-Hydroxymandelate is subsequently oxidized by hydroxymandelate oxidase (Hmo) to 4-hydroxylbenzoylformate, using FMN as a cofactor. Finally, 4-hydroxyphenylglycine transaminase (HpgT) transfers an ammonia moiety from a donor to 4-hydroxylbenzoylformate to form HPG. Several different molecules can serve as the nitrogen donor for the transamination, however, Hubbard et al suspect L-tyrosine to serve as the most efficient donor. By doing so, the following cycle is constructed:
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.
No. Thymosin beta-4 is a 43-residue natural peptide, while TB-500 is a commercial label applied to a short synthetic fragment of it. The two differ in length, sequence coverage and how they are handled in the laboratory.