If you have been reading about prohibited list and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| 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 |
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.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
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.
in his eagerness to weaken it, has cut off all possibility of understanding between the two Masonic Bodies existing and recognized in the Republic of Cuba." They also stated that since the signing of the Treaty of Friendship and Mutual Recognition in 1876, whenever a sanction was issued by the Supreme Council, that the Grand Lodge would show solidarity in issuing the same sanction. If Urquía Carreño did not step down, it would not only be a violation of Masonic Law, but also break almost a century and a half of tradition. If the Treaty of Friendship broke down, they said, it would only be an invitation for the State Security Unit to further infiltrate the brotherhood. Urquía Carreño still refused to step down. After this, certain Lodge Masters sent letters to the United States government, requesting that if Urquía Carreño tried to claim asylum there, to deny him this right for his alleged involvement and collaboration with the State Security Unit.
== Jung's wound == Scholars suggest that Jung's childhood vulnerabilities compelled him to heal his own life. Jung stated that "certain psychic disturbances can be extremely infectious if the doctor himself has a latent predisposition in that direction...For this reason he runs a risk - and must run it in the nature of things". Further he stated that "it is no loss, either, if [the analyst] feels that the patient is hitting him, or even scoring off him: it is his own hurt that gives the measure of his power to heal". Jungians acknowledge that Jung's own wounds could cause damage to those he was attempting to heal.
==== Pharmacokinetics ==== Dronabinol reaches its highest concentration in blood within 1–2 hours of administration. Food intake increases the time and extent of drug absorption, causing a higher drug concentration in blood at a later time. The high lipid solubility of Dronabinol causes its accumulation in fatty organs such as the heart, liver and spleen. Dronabinol is mostly metabolized by CYP2C9 (an enzyme majorly found in the liver) into 11-hydroxy-delta-9-THC, an active molecule that can enter the brain and cause depression or anxiety. More side effects may be seen in patients with diminished CYP2C9 enzyme activity due to the reduced dronabinol metabolism. Dronabinol is majorly eliminated from the body with faeces.
=== August === 6 August – Tom O'Connor, journalist, author, senior citizens' advocate and local politician, president of Grey Power (2016–2018), Waimate District Councillor (since 2013) (born 1944). 8 August Judy Bailey, pianist, composer, jazz musician and educator (Sydney Conservatorium of Music), and television presenter (Play School) (born 1935). Peter Lester, sailor, sailing coach and commentator, OK dinghy world champion (1977), Admiral's Cup winner (1987, 1993) (born 1954). 10 August – Patrick Waddington, Russian linguist, literary critic and historian (Victoria University of Wellington) (born 1934). 13 August – Grant Tavinor, philosopher (Lincoln University) (born c. 1973). 15 August – John Rowan, lawyer, King's Counsel (since 1997) (born 1944). 16 August – Janet Grieve, biological oceanographer (New Zealand Oceanographic Institute, NIWA), New Zealand Association of Scientists president (1998–2000), World Association of Copepodologists president (2008–2011) (born 1940). 17 August – John Bartley, cinematographer (Lost, The X Files, The Chronicles of Riddick), Emmy Award (1996) (born 1947). 18 August Lloyd Ashby, rugby union player (Southland, national team) (born 1931). Lindsay Sparks, cricketer (Central Districts, Auckland) and rugby union player (Marlborough) (born 1944). 19 August – Tony Smith, legal scholar (University of Reading, University of Cambridge, Victoria University of Wellington) (born 1947). 21 August Evelyn Attwood, tennis player (born 1924). Keith Nelson, rugby union player (Otago, Auckland, national team) and dentist (born 1938).
Sources: en.wikipedia.org
This enzyme is an excellent drug target because it is essential, is accessible from the periplasm, and has no equivalent in mammalian cells. DD-Transpeptidase is the target protein of β-lactam antibiotics (e.g. penicillin). This is because the structure of the β-lactam closely resembles the D-ala-D-ala residue. β-Lactams exert their effect by competitively inactivating the serine DD-transpeptidase catalytic site. Penicillin is a cyclic analogue of the D-Ala-D-Ala terminated carbonyl donors, therefore in the presence of this antibiotic, the reaction stops at the level of the serine ester-linked penicilloyl enzyme. Thus β-lactam antibiotics force these enzymes to behave like penicillin binding proteins. Kinetically, the interaction between the DD-peptidase and β-lactams is a three-step reaction:
The GC–MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer. The gas chromatograph utilizes a capillary column whose properties regarding molecule separation depend on the column's dimensions (length, diameter, film thickness) as well as the phase properties (e.g. 5% phenyl polysiloxane). The difference in the chemical properties between different molecules in a mixture and their relative affinity for the stationary phase of the column will promote separation of the molecules as the sample travels the length of the column. The molecules are retained by the column and then elute (come off) from the column at different times (called the retention time), and this allows the mass spectrometer downstream to capture, ionize, accelerate, deflect, and detect the ionized molecules separately. The mass spectrometer does this by breaking each molecule into ionized fragments and detecting these fragments using their mass-to-charge ratio.
Migraine is common, with around 33% of women and 18% of men affected at some point in their lifetime. According to the Global Burden of Disease Study 2021, approximately 14% (1.16 billion) of people worldwide are affected by migraine in a given year. In the United States, about 6% of men and 18% of women experience a migraine attack in a given year, with a lifetime risk of about 18% and 43%, respectively. In Europe, migraine affects 12–28% of people at some point in their lives, with about 6–15% of adult men and 14–35% of adult women getting at least one attack yearly. Rates of migraine are slightly lower in Asia and Africa than in Western countries. Chronic migraine occurs in approximately 1.4–2.2% of the population; and affects around 8% of individuals with migraines. Onset can be at any age, but prevalence rises sharply around puberty, and remains high until declining after age 50. Before puberty, boys and girls are equally impacted, with around 5% of children experiencing migraine attacks. From puberty onwards, women experience migraine attacks at greater rates than men. From age 30 to 50, up to 4 times as many women experience migraine attacks as men; this is most pronounced in migraine without aura.
The core structure of immunoliposomes is a lipid bilayer. This lipid bilayer forms a hydrophilic core, which provides stable encapsulation for a therapeutic payload. Common lipids used are phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol. The lipid bilayer is surface modified through conjugation using monoclonal antibodies for specific recognition of the target cells or tissues of interest. The core of the immunoliposome contains the therapeutic payload, which can be anything from small drugs, nucleic acids, peptides, or imaging agents. There are often stabilizers and excipients present for formulation, stability, and functionality. Some include polyethylene glycol (PEG), antioxidants to prevent degradation of lipids, and buffering agents for optimal pH.
== Nomenclature == Ortho: variously known as 1,2-diethenylbenzene, 1,2-divinylbenzene, o-vinylstyrene, o-divinylbenzene Meta: known as 1,3-diethenylbenzene, 1,3-divinylbenzene, m-vinylstyrene, m-divinylbenzene Para: known as 1,4-diethenylbenzene, 1,4-divinylbenzene, p-vinylstyrene, p-divinylbenzene. These compounds are systematically called diethenylbenzene, although this nomenclature is rarely encountered.
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.
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.