This is a working overview of TB-500, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-22. Anything still debated is marked as such rather than presented as settled.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilised cake or powder |
| Solubility class | Freely soluble in water | Aqueous buffers also used |
| Typical storage temperature | About -20 degrees Celsius | Dry, sealed and protected from light |
| Typical analytical method | Reversed-phase HPLC or LC-MS/MS | Used for purity, identity and quantification |
| Common synonyms | Thymosin beta-4 fragment | Also listed under fragment-based descriptions |
The seven-residue chain carries several polar and charged side chains, so it dissolves readily in water and in aqueous buffers near neutral pH. No cysteine is present, so disulphide formation is not a concern and reducing agents are unnecessary. Dilute ammonium hydroxide or acetonitrile-water mixtures are sometimes used for stock solutions when initial dissolution is slow. Strongly alkaline conditions and prolonged contact with oxidising agents are avoided because they can modify lysine-containing stretches, and haze in solution usually signals incomplete dissolution or aggregated material.
Identity and purity are checked with reversed-phase high-performance liquid chromatography, which separates the target sequence from truncated or deletion analogues, and with mass spectrometry, which confirms the expected molecular mass. Amino acid analysis and peptide mapping give orthogonal confirmation but are used less often outside specialist laboratories. Counter-ion content varies: material purified on trifluoroacetic acid gradients retains trifluoroacetate, and ion exchange can convert the salt form. Residual water and solvent are measured by Karl Fischer titration or thermogravimetric analysis, and any purity figure should be read together with the method used to obtain it.
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.
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.
22 April 2016: Phua Han Chuan Jeffery, a Singaporean and chronic ketamine abuser who was arrested on 20 January 2010 for trafficking more than 100g of heroin into Singapore at Woodlands Checkpoint. He was found guilty and sentenced to death in September 2011. Phua, who lost his three previous appeals against the sentence between July 2012 to September 2015, was granted a re-trial two years and eight months after the government implemented new changes to the death penalty laws (in 2013). He was diagnosed to be suffering from persistent depressive disorder, and the condition, coupled with his chronic ketamine addiction, was argued by Phua's lawyers as sufficient to impair his mental responsibility at the time of the crime. The High Court accepted the defence's arguments and thus re-sentenced Phua, then 30 years old, to life-long incarceration on 22 April 2016, with his sentence backdated to the date of his remand. 27 April 2022: Nagaenthran K Dharmalingam, a Malaysian convicted of trafficking heroin in 2009 and sentenced to death in 2010. After changes to the law took effect in 2013, he applied for re-sentencing but had his application rejected. His appeals to the Court of Appeal were dismissed in 2019. In May 2019 he planned to appeal to the President of Singapore for clemency, but he lost his plea and his execution date was scheduled on 10 November 2021. However, Nagaenthran contracted COVID-19 while in prison and he also made an appeal, hence his execution was postponed and the appeal itself was also postponed twice.
=== Research === During his long career at WSLH, Inhorn pursued many different lines of medical research and public health intervention. In 1960, WSLH was involved in a large community program to promote the new Pap smear test for detecting the early stages of cervical cancer. Inhorn devoted many hours to training personnel in family planning clinics on how to carefully make and screen the Pap smear, both of which are essential to its success. During this time, Inhorn also became active in the American Society of Cytopathology. He chaired its committees to develop best practices in laboratory operation, and he eventually became president of ASC, later receiving the Papanicolaou Award for his contributions to the field of cytopathology. In addition, by 1960, new techniques in the field of cytogenetics permitted the study of infants and children with congenital malformations. Inhorn provided the laboratory component that permitted pediatricians from the UW Medical Center to study a large number of affected children. In particular, Down syndrome had been identified as having three chromosome 21s, instead of two. The Cytogenetics Lab at WSLH identified another trisomy (trisomy 13), an important discovery contributing to the genomic revolution that followed.
Enzymes are not rigid, static structures; instead they have complex internal dynamic motions – that is, movements of parts of the enzyme's structure such as individual amino acid residues, groups of residues forming a protein loop or unit of secondary structure, or even an entire protein domain. These motions give rise to a conformational ensemble of slightly different structures that interconvert with one another at equilibrium. Different states within this ensemble may be associated with different aspects of an enzyme's function. For example, different conformations of the enzyme dihydrofolate reductase are associated with the substrate binding, catalysis, cofactor release, and product release steps of the catalytic cycle, consistent with catalytic resonance theory. The transitions between the different conformations during the catalytic cycle involve internal viscoelastic motion that is facilitated by high-strain regions where amino acids are rearranged.
Sources: en.wikipedia.org
=== Comments on homosexuality === During a performance in Nashville, Tennessee, on June 3, 2011, Morgan made remarks about homosexuals, reportedly stating that if his son were gay, his son better speak to him like a man or he would "pull out a knife and stab him." Morgan apologized, saying that he had "gone too far." In response, head of NBC Entertainment Bob Greenblatt and Morgan's coworker on 30 Rock, Tina Fey, stated they did not condone the comments made by Morgan, and were happy to see him make a sincere apology.
==== Liquid samples ==== Liquid samples can be sandwiched between two plates of a salt—commonly sodium chloride, but a number of other salts such as potassium bromide or calcium fluoride are sometimes. The plates themselves are transparent in the infrared band, allowing the IR effects of the sample itself to be seen through them without substantial interference. If the IR spectrum of the plates themselves is known, this "background spectrum" can be subtracted from the experimental spectrum of the sample to remove artifacts and allow the spectrum of the substance of interest to be seen more clearly. Solutions can also be measured and then the spectrum of the solvent, which would otherwise overwhelm the experimental spectrum, to be removed.
In most of the world, a "hot dog" is recognized as a sausage in a bun, but the type varies considerably. The name is often applied to something that would not be described as a hot dog in North America. For example, in New Zealand a "hot dog" is a battered sausage, often on a stick, which is known as a corn dog in North America; an "American hot dog" is the version in a bun.
== Evolutionary role of cysteine == Cysteine is considered a "newcomer" amino acid, being the 17th amino acid incorporated into the genetic code. Similar to other later-added amino acids such as methionine, tyrosine, and tryptophan, cysteine exhibits strong nucleophilic and redox-active properties. These properties contribute to the depletion of cysteine from respiratory chain complexes, such as Complexes I and IV, since reactive oxygen species (ROS) produced by the respiratory chain can react with the cysteine residues in these complexes, leading to dysfunctional proteins and potentially contributing to aging. The primary response of a protein to ROS is the oxidation of cysteine and the loss of free thiol groups, resulting in increased thiyl radicals and associated protein cross-linking. In contrast, another sulfur-containing, redox-active amino acid, methionine, does not exhibit these biochemical properties and its content is relatively upregulated in mitochondrially encoded proteins.
Sources: en.wikipedia.org
=== Anti-jamming technologies === The British had been aware that the Germans would determine the purpose of the system and attempt to interfere with it, and had designed in a variety of features and methods in order to address some of these issues even as the first stations were being built. The most obvious of these was CH's ability to operate on different frequencies, which was added to allow the stations to avoid any sort of continuous-broadcast interference on their operating frequency. Additionally, the Interference Rejection Unit, or IFRU, allowed the output of the intermediate stages of the amplifiers to be clipped in an attempt to finely tune the receiver to the station's own signals and help reject broadband signals. More complex was a system built into the CH displays, implemented in order to remove spurious signals from unsynchronized jamming pulses. It consisted of two layers of phosphor in the CRT screen, a quick-reacting layer of zinc sulphide below, and a slower "afterglow" layer of zinc cadmium sulphide on top. During normal operation the bright blue signal from the zinc sulphide was visible, and its signal would activate the yellow zinc cadmium sulphide layer, causing an "averaged" signal to be displayed in yellow. To filter out jamming pulses, a yellow plastic sheet was placed in front of the display, rendering the blue display invisible and revealing the dimmer yellow averaged signal. This is the reason many radars from the War through to the 1960s have yellow displays.
== Flavour == Pepper gets its spicy heat mostly from piperine derived from both the outer fruit and the seed. Black pepper contains between 4.6 and 9.7% piperine by mass, and white pepper slightly more than that. Refined piperine, by weight, is about one percent as hot as the capsaicin found in chilli peppers. The outer fruit layer, left on black pepper, also contains aroma-contributing terpenes, including germacrene (11%), limonene (10%), pinene (10%), alpha-phellandrene (9%), and beta-caryophyllene (7%), which give citrusy, woody, and floral notes. These scents are mostly missing in white pepper, as the fermentation and other processing removes the fruit layer (which also contains some of the spicy piperine). Other flavours also commonly develop in this process, some of which are described as off-flavours when in excess: Primarily 3-methylindole (pig manure-like), 4-methylphenol (horse manure), 3-methylphenol (phenolic), and butyric acid (cheese). The aroma of pepper is attributed to rotundone (3,4,5,6,7,8-Hexahydro-3α,8α-dimethyl-5α-(1-methylethenyl)azulene-1(2H)-one), a sesquiterpene originally discovered in the tubers of Cyperus rotundus, which can be detected in concentrations of 0.4 nanograms/l in water and in wine: rotundone is also present in marjoram, oregano, rosemary, basil, thyme, and geranium, as well as in some Shiraz wines.Pepper loses flavour and aroma through evaporation, so airtight storage helps preserve its spiciness longer. Pepper can also lose flavour when exposed to light, which can transform piperine into nearly tasteless isochavicine.
==== Tectonic processes and climate change ==== Isotopes with extremely long half-lives and their decay products can be used to study multi-million year processes, such as tectonics and extreme climate change. For example, in rubidium–strontium dating, the isotopic ratio of strontium (87Sr/86Sr) can be analyzed within ice cores to examine changes over the earth's lifetime. Differences in this ratio within the ice core would indicate significant alterations in the earth's geochemistry.
Sources: en.wikipedia.org
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.
Reported purity reflects the batch tested, the chromatographic method used and whether an independent laboratory performed the work. Values quoted without method detail or a traceable certificate are difficult to compare directly.
Short peptides are rapidly broken down by proteases and appear at low concentrations in urine, so the detection window is narrow. Sensitive extraction combined with tandem mass spectrometry is typically required.
The leading proposal involves sequestration of monomeric actin, which would alter cytoskeletal turnover and cell movement. The actin-binding motif shared with the parent protein is central to that idea. Direct confirmation in whole organisms remains limited.