reverse-phase HPLC raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-05-16. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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 |
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.
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.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
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.
TB-500 is a synthetic peptide whose sequence corresponds to a short fragment near the N-terminus of thymosin beta-4, a small protein present in most mammalian cells. The fragment is commonly cited as containing the actin-binding region of the parent molecule, which is why it appears in laboratory work on cell migration and tissue repair. Suppliers distribute it as a lyophilised powder intended for research use. Its identity is defined by amino acid sequence and by the presence of an acetyl group on the N-terminal residue.
Full-length thymosin beta-4 consists of roughly forty-three amino acids and ranks among the more abundant small proteins in the cytoplasm. The fragment is much shorter, so it cannot reproduce every function attributed to the intact molecule. In cell culture, short actin-binding motifs can interfere with filament dynamics and cell movement, but such observations come from controlled experiments rather than from whole-animal work. Whether a truncated fragment produces the same effects as the parent protein remains an open question.
=== Cancer === Macrophages can contribute to tumor growth and progression by promoting tumor cell proliferation and invasion, fostering tumor angiogenesis and suppressing antitumor immune cells. Inflammatory compounds, such as tumor necrosis factor (TNF)-alpha released by the macrophages activate the gene switch nuclear factor-kappa B. NF-κB then enters the nucleus of a tumor cell and turns on production of proteins that stop apoptosis and promote cell proliferation and inflammation. Moreover, macrophages serve as a source for many pro-angiogenic factors including vascular endothelial factor (VEGF), tumor necrosis factor-alpha (TNF-alpha), macrophage colony-stimulating factor (M-CSF/CSF1) and IL-1 and IL-6, contributing further to the tumor growth. Macrophages have been shown to infiltrate a number of tumors. Their number correlates with poor prognosis in certain cancers, including cancers of breast, cervix, bladder, brain and prostate. Some tumors can also produce factors, including M-CSF/CSF1, MCP-1/CCL2 and Angiotensin II, that trigger the amplification and mobilization of macrophages in tumors. Additionally, subcapsular sinus macrophages in tumor-draining lymph nodes can suppress cancer progression by containing the spread of tumor-derived materials.
Under normal conditions, acetyl-CoA is further oxidized by the citric acid cycle (TCA/Krebs cycle) and then by the mitochondrial electron transport chain to release energy. However, if the amounts of acetyl-CoA generated in fatty-acid β-oxidation challenge the processing capacity of the TCA cycle; i.e. if activity in TCA cycle is low due to low amounts of intermediates such as oxaloacetate, acetyl-CoA is then used instead in biosynthesis of ketone bodies via acetoacetyl-CoA and β-hydroxy-β-methylglutaryl-CoA (HMG-CoA). Furthermore, since there is only a limited amount of coenzyme A in the liver, the production of ketone bodies allows some of the coenzyme to be freed to continue fatty-acid β-oxidation. Depletion of glucose and oxaloacetate can be triggered by fasting, vigorous exercise, high-fat diets or other medical conditions, all of which enhance ketone production. Deaminated amino acids that are ketogenic, such as leucine, also feed TCA cycle, forming acetoacetate & ACoA and thereby produce ketones. Besides its role in the synthesis of ketone bodies, HMG-CoA is also an intermediate in the synthesis of cholesterol, but the steps are compartmentalised. Ketogenesis occurs in the mitochondria, whereas cholesterol synthesis occurs in the cytosol, hence both processes are independently regulated.
== Structure == It was part of the organizational structure of the Ethiopian regular army as one of the 4 divisions that comprised the regular army. The Ethiopian Imperial Host included the 40,000 men and women of the Regular Army and the approximately 100,000 men and women of the National Guard/Biherawi Tor/. The 1st Division or Kebur Zabagna (as it was later reconstituted under Emperor Haile Selassie) was based at Addis Ababa. It was divided into 4 battalions with the 2nd battalion charged with its primary tasking, protection of the person of the Emperor. The 2nd Battalion had an infantry and cavalry regiment based out of Menelik and Jubilee Palaces as well as the soccer stadium in the Lagare area. The other 3 battalions incorporated its marching band, an elite airborne regiment Berari Neber or flying tigers, a medical corps and staff of its own hospital and a headquarters corps. It roughly numbered about 10,000 during the reign of Haile Selassie I.
Methylglyoxal (MGO) is the organic compound with the formula CH3C(O)CHO. It is a reduced derivative of pyruvic acid. It is a reactive compound that is implicated in the biology of diabetes. Methylglyoxal is produced industrially by degradation of carbohydrates using overexpressed methylglyoxal synthase.
Sources: en.wikipedia.org
Another possible example is the Second Congo War (1998–2003) even though it was only waged on one continent. It involved nine nations and led to ongoing low-intensity warfare despite official peace and the first democratic elections in 2006. It has been referred to as "Africa's World War". Similarly, other historians suggest even earlier conflicts to be world wars. For example, Russian ethnologist L. N. Gumilyov called the Byzantine–Sasanian War of 602–628 "the World War of the 7th century" because it evolved into a war between the fourfold informal alliance of the Chinese Empire, the Western Turkic Khaganate, the Khazars, and the Byzantine Empire against a triple union of the Sasanian Empire, the Avars, and the Eastern Turkic Khaganate, with proxy conflicts in Afro-Eurasia (like the Aksumite–Persian wars) and across the Old World.
== Fragile states == The Fragile States Index 2019, compiled by the NGO, Fund for Peace, ranked Thailand 77th in the world for fragility (178=least fragile; 1=most fragile). Finland topped the ranking; Yemen was at the bottom. Other ASEAN nations were ranked: Singapore, 162; Brunei, 124; Malaysia, 119; Vietnam, 109; Indonesia, 93; Laos, 62; Cambodia, 54; Philippines, 50; Myanmar, 22.
Jennifer McDowall/Interpro: Protein of the Month: Fibrinogen. Peter D'Eustachio/reactome: fibrinogen → fibrin monomer + 2 fibrinopeptide A + 2 fibrinopeptide B Khan Academy Medicine (on YouTube): Clotting 1 - How do we make blood clots? Overview of all the structural information available in the PDB for UniProt: P02671 (Fibrinogen alpha chain) at the PDBe-KB. Overview of all the structural information available in the PDB for UniProt: P02675 (Fibrinogen beta chain) at the PDBe-KB. Overview of all the structural information available in the PDB for UniProt: P02679 (Fibrinogen gamma chain) at the PDBe-KB.
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.