heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-12-07. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
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.
| 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 |
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
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.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
Research interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
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.
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.
=== Electronic spectrum === Electrons propagating through the graphene honeycomb lattice effectively lose their mass, producing quasi-particles described by a 2D analogue of the Dirac equation rather than the Schrödinger equation for spin-1/2 particles.
=== Selected books === Diagnosis and Management of Renal Disease and Hypertension (1988) ISBN 9780812111293 Immunohistology in Diagnostic Pathology (1989) ISBN 9780849349874 Non-neoplastic Kidney Diseases (2005) ISBN 9781881041962 Primer on Kidney Diseases (2009) ISBN 9781416051855 Fundamentals of Renal Pathology (2013) ISBN 9783642390791 Heptinstall's Pathology of the Kidney (2024) ISBN 9781975161538
=== Design for affinity === Protein–protein interactions are involved in most biotic processes. Many of the hardest-to-treat diseases, such as Alzheimer's disease, many forms of cancer (e.g., TP53), and human immunodeficiency virus (HIV) infection involve protein–protein interactions. Thus, to treat such diseases, it is desirable to design protein or protein-like therapeutics that bind one of the partners of the interaction and, thus, disrupt the disease-causing interaction. This requires designing protein-therapeutics for affinity toward its partner. Protein–protein interactions can be designed using protein design algorithms because the principles that rule protein stability also rule protein–protein binding. Protein–protein interaction design, however, presents challenges not commonly present in protein design. One of the most important challenges is that, in general, the interfaces between proteins are more polar than protein cores, and binding involves a tradeoff between desolvation and hydrogen bond formation. To overcome this challenge, Bruce Tidor and coworkers developed a method to improve the affinity of antibodies by focusing on electrostatic contributions. They found that, for the antibodies designed in the study, reducing the desolvation costs of the residues in the interface increased the affinity of the binding pair.
After acetylation, the solvent is evaporated to remove the acetic anhydride, and finally water is added. The amount of water added depends on the amount of plant material used in the beginning of the process, most often 30 milliliters per kilogram of dry plant material. Although the drug is primarily intended for intravenous injection, kompot extraction as described here produces an end product containing residual plant matter, waste chemicals, impure water, and other contaminants, making this a dangerous substance to inject since such impurities can lead to abscesses or anaphylactic shock. Use of Polish heroin has been in decline since the break-up of the Soviet Union and its Central and Eastern European satellite states (Hungary, Poland, Czechoslovakia, Romania, et al.) as after 1991 the availability of heroin and other drugs smuggled into those countries from abroad increased enormously. Since then, in Poland "kompot"/"Polish heroin" has all but disappeared, except in a few rural areas where cheaper, purer, more potent drugs have not overwhelmed the illicit marketplace. In Belarus, compote is the most popular psychoactive substance among people on the list of narcological supervision in health care facilities. In 1998 they constituted 75.8% of registered persons, and in 2012 - 53%, and their number increased 2.5 times in the years 1998–2012.
Sources: en.wikipedia.org
== Medical uses == Thiamazole is a drug used to treat hyperthyroidism such as in Graves' disease, a condition that occurs when the thyroid gland begins to produce an excess of thyroid hormone. The drug may also be taken before thyroid surgery to lower thyroid hormone levels and minimize the effects of thyroid manipulation. Additionally, thiamazole is used in the veterinary setting to treat hyperthyroidism in cats.
== Namibian independence == The initial terms of the Geneva Protocol and Security Council Resolution 435 provided the foundation from which a political settlement in South West Africa could proceed: holding of elections for a constitutional assembly, confinement of both PLAN and the SADF to their respective bases, the subsequent phased withdrawal of all but 1,500 SADF troops, demobilisation of all paramilitary forces that belonged to neither the SADF nor to the police, and the return of refugees via designated entry points to participate in elections. Responsibility for implementing these terms rested with UNTAG, which would assist in the SADF withdrawal, monitor the borders, and supervise the demobilisation of paramilitary units.
=== Buoyancy control === Surface-supplied divers may be required to work in mid-water or on the bottom. They must be able to stay down without effort, and this usually requires weighting. When working in mid-water the diver may wish to be neutrally buoyant or negative, and when working on the bottom, will usually want to be several kilograms negative. The only time the diver may want to be positively buoyant is when on the surface or during a limited range of emergencies where uncontrolled ascent is less life-threatening than remaining under water. Surface-supplied divers generally have a secure supply of breathing gas, and there are very few occasions where weights should be jettisoned, so in most cases the surface-supplied diver weighting arrangement does not provide for quick release. On those occasions when surface supplied divers need variable buoyancy, it may be provided by inflation of the dry suit, if used, or by a buoyancy control device similar in principle to those used by scuba divers, or both.
== Green sample preparation == SPME is recognized as a green analytical method for sample preparation, particularly in forensic drug analysis. This technique offers several advantages over traditional methods like liquid–liquid extraction (LLE) and solid-phase extraction (SPE), including automation, rapid sample processing, and reduced solvent usage. SPME allows for the extraction of analytes directly from complex matrices, such as biological and environmental samples, while minimizing the environmental impact associated with conventional extraction techniques.
== Signs and symptoms == The symptoms of CMT often appear in childhood and adolescence, but in some cases, they may not develop until adulthood. The severity and progression of symptoms can vary widely between individuals even among members of the same family. Some people do not experience symptoms until their early 30s or 40s. The most common early sign of CMT is difficulty walking, often due to weakness in the muscles of the lower legs and feet. This muscle weakness can lead to foot drop, where patients have trouble lifting the front part of the foot, causing them to trip or adopt a high-stepping gait. Over time, individuals may develop distinctive foot deformities, such as high arches (known as pes cavus) and curled toes (hammertoes), due to muscle imbalance. As the disease progresses, the weakness often spreads to the hands and forearms, making tasks that require fine motor skills—like buttoning a shirt or writing—more difficult. In addition to motor symptoms, many people with CMT also experience a gradual loss of sensation in the feet, legs, hands, and arms. This sensory loss may affect the ability to feel pain, temperature, or touch, and can lead to problems with balance, especially in low-light conditions. Symptoms and progression of the disease can vary. Involuntary grinding of teeth and squinting are prevalent and often go unnoticed by the person affected. Breathing can be affected in some, as can hearing, vision, and neck and shoulder muscles. Scoliosis is common, causing hunching and loss of height. Hip sockets can be malformed.
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.
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.