This is a working overview of acetylated peptide, 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.
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.
TB-500 is a synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
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.
Detection in biological matrices generally relies on liquid chromatography coupled with tandem mass spectrometry, because the peptide lacks a convenient ultraviolet chromophore beyond the amide backbone. Immunoassays have been described, but antibodies raised against the fragment can cross-react with the full-length protein or with unrelated peptides, so findings usually require confirmation by a second technique. Sample preparation typically involves protein precipitation followed by solid-phase extraction. Reported detection windows depend on dose, route, matrix, and instrument sensitivity.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Calculated for the acetylated heptapeptide |
| Molecular weight | ~889 Da | Monoisotopic mass approximately 889.0 Da |
| Amino acid sequence | Ac-LKKTETQ | N-terminal acetylated seven-residue peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Water-soluble | Peptides of this size generally dissolve in aqueous media |
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
Thymosin beta-4 is a naturally occurring protein of 43 amino acids found in most mammalian cells, where it binds actin monomers and influences filament dynamics. It was first isolated from thymus tissue in the early 1980s, and its actin-binding activity was later mapped to a short region near the N-terminus. The synthetic fragment sold as TB-500 was designed to reproduce that region rather than the full protein. Whether a short fragment reproduces the behavior of the intact molecule remains an open question, since the parent protein carries additional structural elements outside the binding region.
Published research on the intact protein is substantial, covering actin regulation, cell migration, and wound models. Research using the heptapeptide fragment specifically is far smaller, and much of the circulating material originates in supplier documentation rather than peer-reviewed reports. Where fragment studies do exist, they often employ different sequences, chain lengths, or terminal modifications, which complicates direct comparison across papers. Readers encountering claims about TB-500 should therefore separate evidence about thymosin beta-4 from evidence about the fragment itself.
Discussion of the compound frequently appears alongside other short peptides described as fragments of larger proteins. That grouping is convenient but can be misleading, because fragment length, charge, and modification state determine how a peptide behaves in solution and in any experimental system. A seven-residue acetylated peptide and a full-length protein differ in mass by roughly an order of magnitude, and they cannot be assumed to share distribution or binding properties. Precision about which molecule is under discussion is the single most useful step when reading such material.
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.
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.
For example, the α decay of 239Pu to 235U can be used as an example of this procedure. with the assumption of a perfect purification time T0 then there will be a linear relationship between the in-growth of 235U and time elapsed since purification. There are, however, various instances where the correlation is not as clear. This strategy may not apply when the parent-daughter pair achieve secular equilibrium very rapidly or when the half-life of the daughter nuclide is significantly shorter than the time that has elapsed since purification of the nuclear material, e.g. 237Np/233Pa. Another possible complication is if in environmental samples, non-equivalent metal/ion transport for parents and daughter species may complicate or invalidate the use of chronometric measurements. Special age-dating relationships exist, including the commonly employed 234U/230Th and 241Pu/241Am chronometers. In special circumstances, parent-granddaughter relationships can be used to elucidate the age of nuclear materials when the material is intentionally made to look older through the addition of daughter nuclides. Chronometry is based on the concept that the composition of the nuclear material changes as samples are prepared and analyzed. This barrier can be substantial for species that decay quickly or whose daughter products put forth spectral interferences. The decay of 233U, for example, has a t1/2~1.6×105years which is rapid in comparison to many species and yield 229Th, which emits an α particle that is isoenergetic, having the same energy, as the parent.
== Structure == VEGFR-2 are a part of the VEGF family. The other receptors in the family are VEGFR-1 and VEGFR-3. These receptors are a type of transmembrane kinase receptors and have similar structure. They have an extracellular part that is made up of an N-terminus signal and a 7 immunoglobulin-like domain. The intracellular part of the receptor consists of a juxtamembrane (the tyrosine kinase domain), which is divided to proximal and distal kinase domains and a C-terminus tail.
Nortilidine is the major active metabolite of tilidine. It is formed from tilidine by demethylation in the liver. The racemate has opioid analgesic effects roughly equivalent in potency to that of morphine. The (1R,2S)-isomer has NMDA antagonist activity. The drug also acts as a dopamine reuptake inhibitor. The reversed-ester of nortilidine is also known, as is the corresponding analogue with the cyclohexene ring replaced by cyclopentane, which have almost identical properties to nortilidine.
I don't think there was anything else like it at the time. Before TGI Fridays, four single twenty-five-year-old girls were not going out on Friday nights, in public and with each other, to have a good time. They went to people's apartments for cocktail parties or they might go to a real restaurant for a date or for somebody's birthday, but they weren't going out with each other to a bar for a casual dinner and drinks because there was no such place for them to go. TGI Fridays was one of the first to use promotions such as ladies' night, and Stillman achieved his hopes of meeting women; "Have you seen the movie Cocktail? Tom Cruise played me!...Why do girls want to date the bartender? To this day, I'm not sure that I get it." He and the restaurant benefited from its location—according to Stillman, 480 stewardesses lived in the apartment building next door—and received publicity in national magazines. TGI Fridays became so popular that it had to install ropes to create an area for those waiting in line, also unusual at the time for a restaurant. A competitor, Maxwell's Plum, opened across the street, and others soon followed. With fellow Bucknell University graduate Ben Benson, Stillman opened other restaurants, including Tuesday's, Thursday's, Wednesday's, and Ice Cream Sunday's. Franchising of TGI Fridays began two years after the Manhattan location opened, in a since-closed location in Memphis, Tennessee's Overton Square district. In 1971, Daniel R. Scoggin acquired the rights to eight major Midwest cities. In 1972, he opened with the first of a new prototype in Dallas.
=== Competing reactions === The most common side reactivity associated with the Stille reaction is homocoupling of the stannane reagents to form an R2-R2 dimer. It is believed to proceed through two possible mechanisms. First, reaction of two equivalents of organostannane with the Pd(II) precatalyst will yield the homocoupled product after reductive elimination. Second, the Pd(0) catalyst can undergo a radical process to yield the dimer. The organostannane reagent used is traditionally tetravalent at tin, normally consisting of the sp2-hybridized group to be transferred and three "non-transferable" alkyl groups. As seen above, alkyl groups are normally the slowest at migrating onto the palladium catalyst.
Sources: en.wikipedia.org
Human serum albumin is the main protein of human blood plasma. It makes up around 50% of human plasma proteins. It binds water, cations (such as Ca2+, Na+ and K+), fatty acids, hormones, bilirubin, thyroxine (T4) and pharmaceuticals (including barbiturates). Its main function is to regulate the oncotic pressure of blood. The isoelectric point of albumin is 4.7. Alpha-fetoprotein is a fetal plasma protein that binds various cations, fatty acids and bilirubin. Vitamin D-binding protein binds to vitamin D and its metabolites, as well as to fatty acids. Afamin binds vitamin E. It seems to carry lipidated Wnt proteins and Vitamin E around. Extracellular matrix protein 1 is a less canonical albumin. It regulates bone mineralization. The four canonical human albumins are arranged on chromosome 4 region 4q13.3 in a tandem manner.
Jonathan E. Mangum is an Australian biomedical scientist, entrepreneur, and executive known for his contributions to translational proteomics and the development of diagnostic technologies in oral health. He is a co-founder of Incisive Technologies and the scientific lead behind BlueCheck, a diagnostic tool for early detection of dental caries, which received FDA clearance in 2023. Mangum earned his Bachelor and Master of Science degrees in Biochemistry from the University of Otago in New Zealand (1995–2000). He completed a PhD in Biomedical Sciences at the University of Melbourne in 2013. He also holds a Graduate Certificate in Commercialisation from Melbourne Business School.
The Pearl Index, also called the Pearl rate, is the most common technique used in clinical trials for reporting the effectiveness of a birth control method. It is a very approximate measure of the number of unintended pregnancies in 100 woman-years of exposure that is simple to calculate, but has a number of methodological deficiencies. The index was introduced by Raymond Pearl in 1934. It has remained popular for over eighty years, in large part because of the simplicity of the calculation. Several kinds of information are needed to calculate a Pearl Index for a particular study: the total number of months or cycles of exposure by women in the study the number of pregnancies the reason for leaving the study (pregnancy or other reason) There are two calculation methods for determining the Pearl Index:
CooA is a homodimeric, heme-containing transcription factor of the CAP/CRP family, with each monomer comprising an N-terminal heme-binding regulatory domain and a C-terminal helix-turn-helix motif that acts as a DNA-binding domain. The N-terminal domain coordinates a b-type heme whose axial ligands differ between species (for example, His-Pro versus His-His), and carbon monoxide (CO) binding to this heme triggers conformational changes that activate DNA binding. The two subunits associate through a coiled-coil-like interface, positioning the paired helix–turn–helix motifs to recognize target palindromic sequences in promoter DNA and thereby regulate genes involved in CO oxidation. Several structures of CooA have been solved, including: RrCooA in the ferrous state (1FT9), ChCooA in the ferrous, imidazole-bound state (2FMY), ChCooA in the ferrous, CO-bound state (2HKX).
3. Bremelanotide. Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006–. 2025 Feb 15. No information is available on the clinical use of bremelanotide during breastfeeding. Because bremelanotide is a cyclic peptide molecule with a molecular weight of 1025, the amount in milk is likely to be very low and absorption is unlikely because it is probably destroyed in the infant's gastrointestinal tract. Until more data become available, bremelanotide should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant.
Sources: en.wikipedia.org
In the fibrillar collagens, molecules are staggered to adjacent molecules by about 67 nm (a unit that is referred to as 'D' and changes depending upon the hydration state of the aggregate). In each D-period repeat of the microfibril, there is a part containing five molecules in cross-section, called the "overlap", and a part containing only four molecules, called the "gap". These overlap and gap regions are retained as microfibrils assemble into fibrils, and are thus viewable using electron microscopy. The triple helical tropocollagens in the microfibrils are arranged in a quasihexagonal packing pattern.
=== Production of other elements === Americium is a starting material for the production of other transuranic elements and transactinides – for example, 82.7% of 242Am decays to 242Cm and 17.3% to 242Pu. In the nuclear reactor, 242Am is also up-converted by neutron capture to 243Am and 244Am, which transforms by β-decay to 244Cm:
Insulin glargine/lixisenatide, sold under the brand name Soliqua among others, is a fixed-dose combination medication that combines insulin glargine and lixisenatide and is used to treat diabetes. The most common side effects include hypoglycemia (low blood glucose), diarrhea, vomiting and nausea (feeling sick). Insulin glargine/lixisenatide was approved for medical use in the United States in November 2016, and in the European Union in January 2017.
== Role in disease == High levels of kynurenic acid have been identified in patients with tick-borne encephalitis, schizophrenia and HIV-related illnesses. In all these situations, increased levels were associated with confusion and psychotic symptoms. Kynurenic acid acts in the brain as a glycine-site NMDAr antagonist, key in glutamatergic neurotransmission system, which is thought to be involved in the pathophysiology and pathogenesis of schizophrenia. The kynurenic acid hypothesis of schizophrenia was proposed in 2007, based on its action on midbrain dopamine activity and NMDArs, thus linking dopamine hypothesis of schizophrenia with the glutamate hypothesis of the disease. Kynurenic acid is reduced in individuals with mood disorders, such as major depressive disorder and bipolar disorder, especially during depressive episodes. High levels of kynurenic acid have been identified in human urine in certain metabolic disorders, such as marked pyridoxine deficiency and deficiency/absence of kynureninase. When researchers decreased the levels of kynurenic acid in the brains of mice, their cognition was shown to improve markedly. However, kynurenic acid also shows neuroprotective properties. Some researchers have posited that the increased levels found in cases of neurological degradation is due to a failed attempt to protect the cells.
== Other methods == Hydrogen–deuterium exchange Mass spectrometry Protein sequencing Protein synthesis Proteomics Peptide mass fingerprinting Ligand binding assay Eastern blotting Metabolic labeling Heavy isotope labeling Radioactive isotope labeling
Sources: en.wikipedia.org
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.
No. Thymosin beta-4 is a 43-amino-acid protein, while TB-500 represents only a short N-terminal segment. The two should not be treated as interchangeable in experimental design.
It is often called a thymosin beta-4 fragment, Tβ4 fragment, or Ac-LKKTETQ. The name TB-500 is mainly a commercial or catalog label rather than a formal chemical name.
The most common approach is liquid chromatography with tandem mass spectrometry after extraction from blood or urine. Immunoassays exist but are generally treated as screening tools because of cross-reactivity.