This is a working overview of prohibited list, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | Approximately 4963 Da for full-length thymosin beta-4 | Value applies to the parent protein; fragment products may differ |
| Appearance | White to off-white lyophilized powder | Typical form of supplied synthetic peptide |
| Solubility | Freely soluble in water | Polar peptide; dissolves readily in aqueous buffer |
| Storage of dry powder | −20 °C, desiccated, protected from light | Standard laboratory practice for peptides |
| Typical detection method | Liquid chromatography–tandem mass spectrometry | Used in purity testing and anti-doping analysis |
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
Identity and purity checks for peptide material typically combine reversed-phase high-performance liquid chromatography with mass measurement, since retention time alone cannot confirm a sequence. Mass measurement verifies the expected molecular mass within instrument tolerance, while chromatographic peak area provides a purity estimate. Anti-doping analysis of urine uses related but more sensitive workflows, sometimes after solid-phase extraction. For research material, batch documentation, certificate content, and independent testing are common points of scrutiny, because supply chains outside pharmaceutical regulation vary widely in the paperwork they provide.
Reconstitution of a lyophilized peptide is normally done with sterile water or a suitable buffer under aseptic conditions. Adding solvent down the vial wall and allowing gentle dissolution instead of vigorous vortexing reduces the chance of aggregation, which can lower the effective concentration of the resulting solution. Concentrated stocks are usually diluted into working buffer shortly before use. Because no standard preparation protocol exists for TB-500 specifically, laboratories adapt general peptide handling practice, and reported results may reflect differing preparation choices.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
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.
TB-500 is a catalogue name applied to a synthetic peptide related to thymosin beta-4, an actin-binding protein found in most mammalian cells. Suppliers do not use the label consistently: some describe it as the full 43-residue protein, others as a short fragment from the actin-binding region, and others as a related tetrapeptide. Because the name is commercial rather than chemical, two products sold under it may not contain the same molecule. This naming ambiguity is the first point to check in any description of the material.
In the past, the People's Republic of China executed prisoners primarily by means of shooting. Recently, lethal injection has become more common. The specific lethal injection procedures, including the drug or drugs used, are a state secret and not publicly known. Lethal injection in China was legalized in 1996. The number of shooting executions slowly decreased, and in February 2009, the Supreme People's Court ordered the discontinuation of firing squads by the following year under the conclusion that injections were more humane to the prisoner. It has been suggested that the switch is also in response to executions being horrifying to the public. Lethal injections are less expensive than firing squads, with a single dose costing 300 yuan compared to 700 yuan for a shooting execution.
== Prevention == The American College of Obstetricians and Gynecologists recommends all people thinking of becoming pregnant be tested to see if they have thalassemia. Genetic counseling and genetic testing are recommended for families who carry a thalassemia trait. Understanding the genetic risk, ideally before a family is started, would hopefully allow families to understand more about the condition and make an informed decision that is best for their family. A screening policy exists in Cyprus to reduce the rate of thalassemia, which, since the program's implementation in the 1970s (also including prenatal screening and abortion), has reduced the number of children born with the disease from one of every 158 births to almost zero. Greece also has a screening program to identify people who are carriers. In Iran as a premarital screening, the man's red cell indices are checked first. If he has microcytosis (mean cell hemoglobin < 27 pg or mean red cell volume < 80 fl), the woman is tested. When both are microcytic, their hemoglobin A2 concentrations are measured. If both have a concentration above 3.5% (diagnostic of thalassemia trait) they are referred to the local designated health post for genetic counseling. Large-scale awareness campaigns are being organized in India both by government and non-government organizations to promote voluntary premarital screening, with marriage between carriers strongly discouraged.
As a result, bicalutamide appears to not be able to compete with testosterone in this sole part of the body to an extent sufficient to considerably interfere with androgen signaling and function. However, while bicalutamide does not seem to be able to adversely influence testicular spermatogenesis, it may interfere with AR-dependent sperm maturation and transport outside of the testes in the epididymides and vas deferens where androgen levels are far lower, and hence may still be able to impair male fertility. In addition, the combination of bicalutamide with other medications, such as estrogens, progestogens, and GnRH analogues, can compromise spermatogenesis due to their own adverse effects on male fertility. These medications are able to strongly suppress gonadal androgen production, which can severely impair or abolish testicular spermatogenesis, and estrogens also appear to have direct and potentially long-lasting cytotoxic effects in the testes at sufficiently high concentrations.
Sources: en.wikipedia.org
=== Sexual role reversal === It is common among Lepidoptera for females to use pheromones to attract males for mating. In T. ni, both males and females produce pheromones capable of attracting the opposite sex. This has been cited as an example of sexual role reversal.
44 (9): 1829. doi:10.1016/0009-2509(89)85125-5. M. König (2008). Herstellung und Charakterisierung nanoporöser Monolithe auf Basis poröser Gläser mit optimierter geometrischer Form zur Anwendung in der Sensortechnik. Diplomarbeit, Halle.
Directed by David Cohen, made by Psychology News 7 November Life and Art, about assisted reproductive technology (ART) and zygote intrafallopian transfer; Debra Hauer gives a talk at Acland Burghley School; Hossam Abdalla (now on the Human Tissue Authority at the Lister Hospital, Chelsea; the assisted zona hatching technique; intracytoplasmic sperm injection; Robert Winston, Baron Winston of Hammersmith Hospital. Directed by Debra Hauer, produced by Christopher Rawlence, made by Hauer Rawlence 21 November Building for Earthquakes, earthquake engineering in Mexico City; Edward Bortugno of the Office of Emergency Services, California; structural engineer Enrique Martinez Romero of Mexico, and the building of the Mexican Social Security Institute; an earthquake was expected near Acapulco in the next ten years; the North Anatolian Fault is the world's most energetic fault; seismologist Polat Gulkan of the Middle East Technical University; Attilla Ansal, editor of the Bulletin of Earthquake Engineering; Müzeher Erciyastepe of the İnşaat Mühendisleri Odası (IMO, Chamber of Engineers); the gecekondu unsafe buildings; the recent 1992 Erzincan earthquake. Narrated by Seán Barrett (actor), directed by Nick Read, produced by Bill Redway, made by October Films 28 November Space Shuttle Discovery, the Johnson Space Center in Texas, and the ACTS satellite (launched in September 1993 on STS-51) and the shuttle pallet satellite (SPAS) system; the 57th mission of the shuttle - STS-51; Commander Frank L.
== Specialties == Proline is one of the two amino acids that do not follow along with the typical Ramachandran plot, along with glycine. Due to the ring formation connected to the beta carbon, the ψ and φ angles about the peptide bond have fewer allowable degrees of rotation. As a result, it is often found in "turns" of proteins as its free entropy (ΔS) is not as comparatively large to other amino acids and thus in a folded form vs. unfolded form, the change in entropy is smaller. Furthermore, proline is rarely found in α and β structures as it would reduce the stability of such structures, because its side chain α-nitrogen can only form one nitrogen bond. Additionally, proline is the only amino acid that does not form a red-purple colour when developed by spraying with ninhydrin for uses in chromatography. Proline, instead, produces an orange-yellow colour.
Sources: en.wikipedia.org
== External links == Clinical trial number NCT02782741 for "Study to Compare the Efficacy and Safety of Enzyme Replacement Therapies Avalglucosidase Alfa and Alglucosidase Alfa Administered Every Other Week in Patients With Late-onset Pompe Disease Who Have Not Been Previously Treated for Pompe Disease (COMET)" at ClinicalTrials.gov Clinical trial number NCT01898364 for "Safety and Efficacy Evaluation of Repeat neoGAA Dosing in Late Onset Pompe Disease Patients" at ClinicalTrials.gov Clinical trial number NCT02032524 for "Avalglucosidase Alfa Extension Study (NEO-EXT)" at ClinicalTrials.gov Clinical trial number NCT03019406 for "A Study to Assess Safety and Efficacy of Avalglucosidase Alfa Administered Every Other Week in Pediatric Patients With Infantile-onset Pompe Disease Previously Treated With Alglucosidase Alfa (Mini-COMET)" at ClinicalTrials.gov
=== Policy on Scouting America === In November 2025, Hegseth in a draft memo proposed eliminating the promotion for Eagle Scouts who join the Army and other services due to the lack of "masculine values" and "promoting gender confusion." He also threatened to cut all support from the Department of Defense to Scouting America. The proposal in the draft memo would eliminate support to the National Jamboree as well as ban military bases from hosting or sponsoring scout units. He claimed that the organization was attacking "boy-friendly" spaces by allowing girls to join the organization in 2018. Military families and retired military have criticized the possible actions by Hegseth, stating it will harm military dependent children who depend on the organization as a stabilizing force. Other critics stated that this proposal would harm the military, as 20 percent of military academy students are former scouts and a number of scouts go directly into the military due to the partnership. Navy Secretary John Phelan wrote a memo of his own, stating, "Passive support to Scouting America through access to military installations and educational opportunities aboard said installations serve as a crucial recruiting and community engagement tool for the [Navy]". On February 27, 2026, Scouting America announced that they would immediately drop the Citizenship in the Society merit badge, will create a military service merit badge and waive registration fees for dependent children of active duty military, National Guard and reserve families.
== Taxonomy and distribution == Within the world of taxonomy, the stable 'Classical System' of Michaelsen (1900) and Stephenson (1930) was gradually eroded by the controversy over how to classify earthworms, such that Fender and McKey-Fender (1990) went so far as to say, "The family-level classification of the megascolecid earthworms is in chaos." Over the years, many scientists have developed their own classification systems for earthworms, which led to confusion, and these systems have been and still continue to be revised and updated. The classification system used here which was developed by Blakemore (2000), is a modern reversion to the Classical System that is historically proven and widely accepted. Categorization of a megadrile earthworm into one of its taxonomic families under suborders Lumbricina and Moniligastrida is based on such features as the makeup of the clitellum, the location and disposition of the sex features (pores, prostatic glands, etc.), number of gizzards, and body shape. Currently, over than 6,000 species of terrestrial earthworms are named, as provided in a species name database, but the number of synonyms is unknown. The families, with their known distributions or origins:
Sources: en.wikipedia.org
Not necessarily. TB-500 is a commercial label that suppliers apply to synthetic peptides described as thymosin beta-4 or a fragment of it. Published research most often studies the full-length protein, so statements about one do not automatically transfer to the other.
No. No major regulatory authority lists an approved product under this name, and no pharmacopoeial monograph exists for it. Material sold under the label is therefore supplied outside approved pharmaceutical channels, which affects the quality documentation available.
It falls within a prohibited class covering peptide hormones and growth factors, based on presumed effects on tissue repair and blood vessel formation. Anti-doping laboratories have published mass spectrometry methods for detecting thymosin beta-4 related peptides in urine samples.
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.