The short version of TB-500 fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | ≈889 Da for the 7-residue fragment | Full-length thymosin beta-4 is ≈4.9 kDa; catalogs differ |
| Appearance | White to off-white powder | Hygroscopic; weight shifts with residual moisture |
| Solubility class | Freely soluble in water | Also dissolves in aqueous buffers; poorly soluble in nonpolar solvents |
| Typical storage temperature | −20 °C, desiccated, protected from light | Once rehydrated, short-term holding at 2-8 °C |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity by UV absorbance; identity by ESI-MS or MALDI-TOF |
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.
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.
Lyophilised peptide powders are hygroscopic, and the fragment absorbs atmospheric moisture when a vial is opened at room temperature. Weighing and aliquoting are normally done quickly in a dry environment, and stock solutions are divided into single-use portions before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and can shift the measured content of a vial. These practices are general to synthetic peptides rather than unique to this sequence, but they matter more for short chains kept for long periods.
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.
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
The capture and marking of birds enable detailed studies of life history. Techniques for capturing birds are varied and include the use of bird liming for perching birds, mist nets for woodland birds, cannon netting for open-area flocking birds, the bal-chatri trap for raptors, decoys and funnel traps for water birds.
In some cases soon after the operation, there were indeed noticeable positive changes in appearance and behavior (with a rapid senility of the body soon following). There were many messages about wonderful results of the operations that, apparently, were false advertising of unscrupulous doctors. But numerous failures became apparent, for which the method was sharply criticized and banned. Serge Voronoff and some other doctors, who claimed producing wonderful results after the operations, got bad reputation. However, despite the failure in the main direction, the conducted research led to the emergence of allotransplantation and xenotransplantation directions in surgery, brought significant knowledge about the effect of sex hormones on the body, stimulated their study. It may be just a coincidence but in 1929–33 several varieties of estrogen were discovered, and testosterone was isolated in 1935. Also these experiments formed the basis for several works of public culture (for example, Heart of a Dog by Mikhail Bulgakov, The Adventure of the Creeping Man from the series about Sherlock Holmes, a song Monkey-Doodle-Doo of Irving Berlin). 1926–1928 Experiments on rejuvenation by blood transfusion, conducted by Alexander Bogdanov in the world's first Institute for Blood Transfusion especially created for that purpose. Bogdanov himself died during one of the experiments, because at that time little was known about the factors of blood compatibility of different people. The institute, having undergone several renames, exists and is still actively working.
ubiquitination Also ubiquitylation. The labelling of a biomolecule (often another protein) by covalently attaching a ubiquitin protein to it—generally via the formation of an amide bond between the ubiquitin's C-terminal glycine and positively charged side chains (often lysine or arginine residues) of the labelled molecule, an ATP-dependent reaction catalyzed by ubiquitin-conjugating enzymes—thus making it identifiable to molecules capable of recognizing ubiquitin epitopes. Ubiquitination is a widely used post-translational modification by which proteins are tagged; the attachment of a single ubiquitin molecule (monoubiquitination) can variously activate or inhibit a protein's activity, while the attachment of a chain of multiple consecutively linked ubiquitin molecules (polyubiquitination) commonly targets the protein for degradation by proteasomes.
His method of testing won the Intel International Science and Engineering Fair Gordon E. Moore Award in the spring of 2012. The Boeing Company has patented the use of carbon nanotubes for structural health monitoring of composites used in aircraft structures. This technology is hoped to greatly reduce the risk of an in-flight failure caused by structural degradation of aircraft. Zyvex Technologies has also built a 54' maritime vessel, the Piranha Unmanned Surface Vessel, as a technology demonstrator for what is possible using CNT technology. CNTs help improve the structural performance of the vessel, resulting in a lightweight 8,000 lb boat that can carry a payload of 15,000 lb over a range of 2,500 miles. IMEC is using carbon nanotubes for pellicles in semiconductor lithography. In tissue engineering, carbon nanotubes have been used as scaffolding for bone growth. Carbon nanotubes can serve as additives to various structural materials. For instance, nanotubes form a tiny portion of the material(s) in some (primarily carbon fiber) baseball bats, golf clubs, car parts, or damascus steel. IBM expected carbon nanotube transistors to be used on Integrated Circuits by 2020.
Sources: en.wikipedia.org
==== Micrococcus lysodeikticus ==== By the measurement of decrease in turbidity of M. lysodeikticus by incubating it with lysozyme, enzymatic activity can be evaluated. 7.5 μL of 0.1 - 1 mg/mL proteins is added to 200 μL of M. lysodeikticus at its optical density (OD) of 1.7 AU, and the mixture is measured at 450 nm periodically for reaction rate calculation. On the contrary to the result from glycol chitosan enzymatic activity, the increasing degree of PEGylation decreased the enzymatic activity. This difference in the trend of the enzymatic activity can be due to PEGylation to free lysine causing steric hindrance and subsequently preventing from forming enzyme-substrate complex in the case of reacting with macromolecule, such as M. lysodeikticus.
Great Britain, Ireland, Germany, the Netherlands, Sweden, and Denmark have produced a number of bog bodies, mummies of people deposited in sphagnum bogs, apparently as a result of murder or ritual sacrifices. In such cases, the acidity of the water, low temperature and lack of oxygen combined to tan the body's skin and soft tissues. The skeleton typically disintegrates over time. Such mummies are remarkably well preserved on emerging from the bog, with skin and internal organs intact; it is even possible to determine the decedent's last meal by examining stomach contents. The Haraldskær Woman was discovered by labourers in a bog in Jutland in 1835. She was erroneously identified as an early medieval Danish queen, and for that reason was placed in a royal sarcophagus at the Saint Nicolai Church, Vejle, where she currently remains. Another bog body, also from Denmark, known as the Tollund Man was discovered in 1950. The corpse was noted for its excellent preservation of the face and feet, which appeared as if the man had recently died. Only the head of Tollund Man remains, due to the decomposition of the rest of his body, which was not preserved along with the head.
Urine testing is the most common method of testing for ketones. Urine test strips utilize a nitroprusside reaction with acetoacetate to give a semi-quantitative measure based on color change of the strip. Although beta-hydroxybutyrate is the predominant circulating ketone, urine test strips only measure acetoacetate. Urinary ketones often correlate poorly with serum levels because of variability in excretion of ketones by the kidney, influence of hydration status, and renal function.
Sources: en.wikipedia.org
Sortase refers to a group of prokaryotic peptidases that modify surface proteins by recognizing and cleaving a carboxyl-terminal sorting signal. For most substrates of sortase enzymes, the recognition signal consists of the motif LPXTG (Leu-Pro-any-Thr-Gly), then a highly hydrophobic transmembrane sequence, followed by a cluster of basic residues such as arginine. Cleavage occurs between the Thr and Gly, with transient attachment through the Thr residue to the active site Cys residue, followed by transpeptidation that attaches the protein covalently to cell wall components. Sortases occur in almost all Gram-positive bacteria and the occasional Gram-negative bacterium (e.g. Shewanella putrefaciens) or Archaea (e.g. Methanobacterium thermoautotrophicum), where cell wall LPXTG-mediated decoration has not been reported. Although sortase A, the "housekeeping" sortase, typically acts on many protein targets, other forms of sortases recognize variant forms of the cleavage motif, or catalyze the assembly of pilins into pili.
Herophilos (335–280 BC) described the functions of the optic nerve in sight and the oculomotor nerve in eye movement. Analysis of the nerves in the cranium enabled him to differentiate between blood vessels and nerves (Ancient Greek: νεῦρον (neûron) "string, plant fiber, nerve"). Modern research has not confirmed William Cullen's 1785 hypothesis associating mental states with physical nerves, although popular or lay medicine may still invoke "nerves" in diagnosing or blaming any sort of psychological worry or hesitancy, as in the common traditional phrases "my poor nerves", "high-strung", and "nervous breakdown".
=== Seizures === Phenobarbital is used in the treatment of all types of seizures, except absence seizures. It is no less effective at seizure control than phenytoin, but phenobarbital is not as well tolerated. Phenobarbital may provide a clinical advantage over carbamazepine for treating partial seizures. Carbamazepine may provide a clinical advantage over phenobarbital for generalized tonic–clonic seizures. The first-line drugs for treatment of status epilepticus are benzodiazepines, such as lorazepam, clonazepam, midazolam, or diazepam. If these fail, then phenytoin may be used, with phenobarbital being an alternative in the US (favored in infants), but used only third-line in the UK. Failing that, the only treatment is anesthesia in intensive care. The World Health Organization (WHO) gives phenobarbital a first-line recommendation in the developing world and it is commonly used there. Phenobarbital is the first-line choice for the treatment of neonatal seizures. Concerns that neonatal seizures in themselves could be harmful make most physicians treat them aggressively. However, no reliable evidence supports this approach.
The protective effect of breastfeeding against obesity is consistent, though small, across many studies. A 2013 longitudinal study reported less obesity at ages two and four years among infants who were breastfed for at least four months.
Sources: en.wikipedia.org
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.
The name is a commercial label rather than a systematic chemical designation, so different vendors and papers attach it to different sequences. Some treat it as a fragment and others as the whole protein. Comparing two reports therefore requires checking what each one actually analyzed.
Typically it reflects the relative area of the main peak in a reversed-phase chromatogram at a given wavelength. It does not confirm the amino acid sequence, the counter-ion, or the amount of peptide by mass. Identity is normally established by a separate mass measurement.
Short transit at ambient temperature is generally tolerated, but long-term storage at room temperature is not recommended. Heat, moisture, and light all accelerate degradation. Cold, dry, dark storage is the conventional choice.