thymosin beta-4 comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-02-04. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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 |
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.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Pizza Pizza is a primarily Ontario-based pizza chain founded in 1967 by Michael Overs with more than 700 traditional and non-traditional restaurants coast to coast with over 3,000 employees. Its sister brand is western chain, Pizza 73. Pizza Pizza fills approximately 29 million orders annually and has won a Webby for their iPhone App.
== Alginate hydrogels == In research on bone reconstruction, alginate composites have favorable properties encouraging regeneration, such as improved porosity, cell proliferation, and mechanical strength. Alginate hydrogel is a common biomaterial for bio-fabrication of scaffolds and tissue regeneration. Covalent bonding of thiol groups to alginate improves in-situ gelling and mucoadhesive properties; the thiolated polymer (thiomer) forms disulfide bonds within its polymeric network and with cysteine-rich subdomains of the mucus layer. Thiolated alginates are used as in situ gelling hydrogels, and are under preliminary research as possible mucoadhesive drug delivery systems. Alginate hydrogels may be used for drug delivery, exhibiting responses to pH changes, temperature changes, redox, and the presence of enzymes.
== June 27, 1915 (Sunday) == Born: Grace Lee Boggs, American author and social activist, author of The Invading Socialist Society and The Next American Revolution; as Grace Chin Lee, in Providence, Rhode Island, United States (d. 2015)
Villhauer at Novartis started to explore N-substituted glycinyl-cyanopyrrolidines based on the fact that DPP-4 identifies N-methylglycine as an N-terminal amino acid. This group of new cyanopyrrolidines became extremely popular field of research in the following years. Some trials with dual inhibitors of DPP-4 and vasopeptidase have been represented, since vasopeptidase inhibition is believed to enhance the antidiabetic effect of DPP-4 inhibition by stimulating insulin secretion. Vasopeptidase-inhibiting motif is connected to the DPP-4 inhibitor at the N-substituent.
Sources: en.wikipedia.org
=== Society === Little is revealed of the Combine's activities outside of Earth, but dialogue in Half-Life 2 states that they control worlds of various dimensions inhabited by a range of species. The Combine occupation of Earth is shown to be a brutal totalitarian police state. In City 17, an Eastern European city, Civil Protection units routinely conduct searches of apartment blocks, interrogating human citizens, and engaging in wanton police brutality. The military Overwatch forces of the Combine attack human resistance bases in an effort to further solidify their authority in the urban centers. Human citizens are clad in blue uniforms, living in designated apartment blocks and move around to different cities or locales in passenger trains by the Combine's will. Vortigaunts, enemy alien creatures from Half-Life, have also been enslaved, and are observed in various professions such as janitors. According to Half-Life 2: Raising the Bar, the Combine are draining Earth's oceans and resources to be used on other Combine worlds. The heart of the Combine's command over Earth in Half-Life 2 is the Citadel, a large tower constructed by them which reaches both tens of thousands of feet (several or several tens of kilometres) into the sky and deep underground. Located within City 17, the Citadel serves as the Combine's headquarters on Earth, housing Combine Advisors and the office of Earth's administrator, Dr. Wallace Breen. Breen, a puppet ruler, is frequently seen on large screens around the city on which he spreads propaganda and makes announcements.
==== Females ==== Outcomes have generally indicated that early onset of puberty in females can be psychologically damaging. The main reason for this detrimental effect is the issue of body image. As they physically develop, gaining weight in several areas of the body, early-maturing females usually look larger than females who have not yet entered puberty. A result of the social pressure to be thin, the early-maturing females develop a negative view of their body image. In addition, people may tease the females about their visible breasts, forcing the early-maturing female to hide her breasts by dressing differently. Embarrassment about a more developed body may also result in the refusal to undress for gym. These experiences lead to lower self-esteem, more depression and poorer body image in these early-maturing females. Furthermore, as physical and emotional differences set them apart from people in their same age group, early-maturing females develop relationships with older people. For instance, some early-maturing females have older malefriends, "attracted to the females' womanly physique and femaleish innocence." While having an older malefriend might improve popularity among peers, it also increases the risk of alcohol and drug use, increased sexual relations (often unprotected), eating disorders and bullying. Generally, later onset of puberty in females produces positive outcomes. They exhibit positive behaviors in adolescence that continue to adulthood.
Instead, the German forces were equipped with US nuclear weapons. On 13 November 1957, in the Konzerthaus (Concert Hall) in Vienna, Hahn warned of the "dangers of A- and H-bomb-experiments", and declared that "today war is no means of politics anymore – it will only destroy all countries in the world". His highly acclaimed speech was transmitted internationally by the Austrian radio, Österreichischer Rundfunk (ÖR). On 28 December 1957, Hahn repeated his appeal in an English translation for the Bulgarian Radio in Sofia, which was broadcast in all Warsaw pact states.
== Other animals == Hyaluronan is used in treatment of articular disorders in horses, in particular those in competition or heavy work. It is indicated for carpal and fetlock joint dysfunctions, but not when joint sepsis or fracture are suspected. It is especially used for synovitis associated with equine osteoarthritis. It can be injected directly into an affected joint, or intravenously for less localized disorders. It may cause mild heating of the joint if directly injected, but this does not affect the clinical outcome. Intra-articularly administered medicine is fully metabolized in less than a week. According to Canadian regulation, hyaluronan in HY-50 preparation should not be administered to animals to be slaughtered for horse meat. In Europe, however, the same preparation is not considered to have any such effect, and edibility of the horse meat is not affected.
=== Genetics === Genetic diseases of thiamine transport are rare but serious. Thiamine responsive megaloblastic anemia syndrome (TRMA) with diabetes mellitus and sensorineural deafness is an autosomal recessive disorder caused by mutations in the gene SLC19A2, a high affinity thiamine transporter. TRMA patients do not show signs of systemic thiamine deficiency, suggesting redundancy in the thiamine transport system. This has led to the discovery of a second high-affinity thiamine transporter, SLC19A3. Leigh disease (subacute necrotising encephalomyelopathy) is an inherited disorder that affects mostly infants in the first years of life and is invariably fatal. Pathological similarities between Leigh disease and WE led to the hypothesis that the cause was a defect in thiamine metabolism. One of the most consistent findings has been an abnormality of the activation of the pyruvate dehydrogenase complex. Mutations in the SLC19A3 gene have been linked to biotin-thiamine responsive basal ganglia disease, which is treated with pharmacological doses of thiamine and biotin, another B vitamin. Other disorders in which a putative role for thiamine has been implicated include subacute necrotising encephalomyelopathy, opsoclonus myoclonus syndrome (a paraneoplastic syndrome), and Nigerian seasonal ataxia (or African seasonal ataxia). In addition, several inherited disorders of ThDP-dependent enzymes have been reported, which may respond to thiamine treatment.
Sources: en.wikipedia.org
=== Glycine === Glycine is biosynthesized from serine, catalyzed by serine hydroxymethyltransferase (SHMT). The enzyme effectively replaces a hydroxymethyl group with a hydrogen atom. SHMT is coded by the gene glyA. The regulation of glyA is complex and is known to incorporate serine, glycine, methionine, purines, thymine, and folates, The full mechanism has yet to be elucidated. The methionine gene product MetR and the methionine intermediate homocysteine are known to positively regulate glyA. Homocysteine is a coactivator of glyA and must act in concert with MetR. On the other hand, PurR, a protein which plays a role in purine synthesis and S-adeno-sylmethionine are known to down regulate glyA. PurR binds directly to the control region of glyA and effectively turns the gene off so that glycine will not be produced by the bacterium.
The Gulf War began with an extensive aerial bombing campaign on 16 January 1991. For 42 consecutive days and nights, the coalition forces subjected Iraq to one of the most intensive air bombardments in military history. The coalition flew over 100,000 sorties, dropping 88,500 tonnes of bombs, which widely destroyed military and civilian infrastructure. Iraqi anti-aircraft defenses, including man-portable air-defense systems, were surprisingly ineffective against enemy aircraft, and the coalition suffered only 75 aircraft losses in over 100,000 sorties, 44 due to Iraqi action. Two of these losses are the result of aircraft colliding with the ground while evading Iraqi ground-fired weapons. One of these losses is a confirmed air-air victory.
=== Diseases === The moth is susceptible to viral diseases including nucleopolyhedrovirus (NPV). This is a naturally occurring virus whose natural hosts include Lepidoptera, arthropods, and Hymenoptera. From the family Baculoviridae, it is a type of Alphabaculovirus and its genome is 80–180kb long. NPVs are commonly used as pesticides for the cabbage looper. There are numerous NPVs, many of which were isolated from the cabbage looper or the alfalfa looper. NPVs vary in infectivity and virulence. For example, the AcMNPV isolates are more infectious than the TnSNPV (the SNPV/single nuclear polyhedrosis virus specific to the cabbage looper) isolates in the first instar, while the TnSNPV isolates produced more occlusion bodies, protein structures that protect the virus and increase long term infectivity. TnSNPVs are their most lethal during the third and fourth instars; they have detrimental effects such as delayed development, reduced egg production, and fewer hatched eggs. These effects are significantly diminished when the larvae are infected during the fifth instar, suggesting that the earlier infection is more effective. Bacillus thuringiensis (Bt) is a gram-positive soil bacterium from the phylum Bacillota. It is often used as a biological insecticide for numerous insect pests, including the cabbage looper, and reduces both growth rate and pupal weight. The cabbage looper has demonstrated resistance to Bt, specifically the toxin Cry1Ac, due to an autosomal recessive allele.
== Appendix: Download surveys / evaluations == The AIDA developers have undertaken a range of surveys and evaluations of usage of the AIDA diabetes simulator — to better understand who is downloading the program, and why. One initial study analysed data from 1,360 downloads of the AIDA software. The intended goals of the survey were: (i) to establish the feasibility of using the Internet for auditing and surveying diabetes software users; (ii) to identify the proportion of people with diabetes and their relatives who are actually making use of the program; and (iii) to establish certain technical details about downloaders' computer setups to facilitate the distribution of upgrades to the software. 1,360 responses were received over an 8-month period (from November 1999 to July 2000). During the corresponding period 3,821 actual downloads of the software were independently logged at the Website — giving a response rate to this survey of 35.6%. Responses were received from participants in 67 countries — although over half of these (n=730, 54%) originated from the US and UK. 762 responses (56%) were received from people with diabetes and 184 (13.5%) from relatives of patients, with lesser numbers from doctors, students, diabetes educators, nurses, pharmacists, and other end users. Useful technical information about computers and operating systems being used were also obtained. The initial study established the feasibility of using the Internet to survey, at no real cost, a large number of medical software downloaders / users.
These include effects on chaperone proteins, which help fold proteins and remove misfolded ones; interactions with caspases, which play a role in the process of removing cells; the toxic effects of glutamine on nerve cells; impairment of energy production within cells; and effects on the expression of genes. Mutant huntingtin protein has been found to play a key role in mitochondrial dysfunction. The impairment of mitochondrial electron transport can result in higher levels of oxidative stress and release of reactive oxygen species. Glutamine is known to be excitotoxic when present in large amounts, that can cause damage to numerous cellular structures. Excessive glutamine is not found in HD, but the interactions of the altered huntingtin protein with numerous proteins in neurons lead to an increased vulnerability to glutamine. The increased vulnerability is thought to result in excitotoxic effects from normal glutamine levels. A somatic expansion of CAG repeats is involved in the progression of the disease. Over decades, the HTT gene first sees its CAG repeats expand to about 80 copies: the 35+ CAG locus causes additional slippage errors that expand the repeat. Then the process accelerates, reaching 150 copies within years. There is no significant toxic effect on the cell until 150 copies, at which point a large number of genes become progressively dysregulated. Over months, the medium spiny neuron slowly loses its cell identity until cell death pathways are activated.
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 lyophilised powder is typically held at -20 C or lower in a dry, dark place. Reconstituted solutions are aliquoted and frozen to avoid repeated freeze-thaw cycles.