The short version of reverse-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-11-16. Anything still debated is marked as such rather than presented as settled.
Purity is normally assessed by reversed-phase HPLC, with the main peak reported as a percentage of total peak area, while identity is confirmed by mass spectrometry. Electrospray and MALDI-TOF instruments are both used, and the observed mass is compared with the value calculated from the stated sequence. Ion-exchange or size-exclusion methods appear where aggregation or charge variants are of interest. Water content, counter-ion content and residual trifluoroacetate from purification are separate variables that can shift the measured mass and should be weighed when reading a certificate of analysis.
Research peptides are typically supplied as a white to off-white lyophilised powder in a sealed vial. The dry solid is more stable than a solution and is normally kept refrigerated or frozen until use. Dissolution is usually done in water, phosphate-buffered saline or a similar aqueous medium, depending on the assay. Because the material is hygroscopic and easily contaminated, opening vials in a low-humidity environment and recording the lot number before use are standard laboratory practices.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
Thymosin beta-4 contains 43 amino acids and has a reported molecular mass near 4963 Da. The short fragment most often associated with the TB-500 label, an acetylated chain beginning LKKTETQ, has a reported mass near 889 Da, so the two are easily separated in analytical work. Mass spectrometry and amino acid analysis can confirm which material is present in a given sample. Statements treating TB-500 and thymosin beta-4 as interchangeable are therefore imprecise, even though the two appear together in much of the same literature.
| Property | Value | Notes |
|---|---|---|
| Typical form | Lyophilised powder | Reconstituted before use |
| Storage temperature, dry | -20 °C or below | Desiccated, protected from light |
| Purity determination | Reversed-phase HPLC | Reported as percentage of total peak area |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF versus calculated mass |
| Common synonyms | Tβ4 fragment; thymosin beta-4 fragment | Naming varies between suppliers |
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.
TB-500 is a synthetic seven-residue peptide whose sequence, LKKTETQ, matches the N-terminal actin-binding region of thymosin beta-4. It is usually supplied in an N-terminally acetylated form, a modification that blocks the free amino terminus and can influence behavior in solution. In the research literature the same sequence appears under several names, including thymosin beta-4 fragment and shortened thymosin beta-4. Because it is a short peptide rather than the full 43-residue parent protein, its measured properties differ from those reported for thymosin beta-4 as a whole, and the two are not interchangeable in experimental design.
Thymosin beta-4 itself is a small, widely expressed protein that sequesters monomeric actin and participates in cell migration, angiogenesis, and tissue repair. Researchers have examined the shortened fragment as a possible mimic of some of these activities, reasoning that the actin-binding motif lies within the first few residues. Binding to monomeric actin has been observed in cell-free systems. Whether the fragment reproduces the broader effects of the full protein in living tissue remains an open question, and findings from animal models are frequently cited without a clear bridge to human physiology.
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.
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.
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.
== Personal life == Pansino currently resides in Los Angeles, where she films all her YouTube videos. In 2018, Pansino announced her already years-long relationship with e-sports commentator Mike Lamond, better known as Husky. On December 17, 2019, Pansino announced throughout her social media outlets that her father, who appeared in several of her videos, had died as a result of leukemia, which he had been fighting for six years. On August 13, 2026, Pansino announced via Instagram stories that she is single. She made allegations against her ex-boyfriend, claiming that she experienced "abusive and coercive control" from him and that a domestic violence restraining order had been partially granted.
A woman sentenced to 28 months imprisonment for illegally obtaining abortion pills in 2020 has her sentence reduced to a 14-month suspended sentence by the Court of Appeal, and will be released from prison. The Home Office confirms the release of the first passports issued in King Charles III's name. 19 July The UK rate of inflation falls from 8.7% in May to 7.9% in June. Rishi Sunak issues an apology for the UK's historical treatment of LGBT people who were dismissed from the military because of their sexuality. 20 July Senior doctors begin a two-day walkout, their first strike in a decade, amid an ongoing dispute over pay. The Competition and Markets Authority tells supermarkets they must make their food pricing clearer in order to help shoppers make informed decisions about the best deals. A University of Oxford study suggests that if heavy meat eaters were to cut some of it out of their diet it would be like removing eight million cars from the road. The first phase of the COVID-19 Inquiry comes to an end, with an interim report expected to be published in 2024. 21 July July 2023 by-elections: Uxbridge and South Ruislip: The former seat of ex-PM Boris Johnson is held by the Conservatives, but with a significantly reduced majority of 495 votes. The proposed ULEZ expansion by Labour's Sadiq Khan, Mayor of London, is a factor in the result. Selby and Ainsty: Labour takes the formerly safe Conservative seat of Selby and Ainsty. The swing of 23.7% is the largest since 1945.
=== Post-translational modifications === Whilst detailed comparison of the MS data with predictions based on the known protein sequence may be used to define post-translational modifications, targeted approaches to data acquisition may also be used. For instance, specific enrichment of phosphopeptides may assist in identifying phosphorylation sites in a protein. Alternative methods of peptide fragmentation in the mass spectrometer, such as ETD or ECD, may give complementary sequence information.
=== Dose reconstruction with ESR spectroscopy of deciduous teeth === As a result of accidents or improper use and disposal of radiation sources, a significant number of people are exposed to varying degrees of radiation. Radioactivity and local dose measurements are not sufficient to fully assess the effects of radiation. To retrospectively determine the individual radiation dose, measurements are made on teeth, i.e. on biological, endogenous materials. Tooth enamel is particularly suitable for the detection of ionizing radiation due to its high mineral content (hydroxyapatite), which has been known since 1968 thanks to the research of John M. Brady, Norman O. Aarestad and Harold M. Swartz. The measurements are performed on milk teeth, preferably molars, using electron paramagnetic resonance spectroscopy (ESR, EPR). The concentration of radicals generated by ionizing radiation is measured in the mineral part of the tooth. Due to the high stability of the radicals, this method can be used for dosimetry of long past exposures.
=== Inhibition of ACTH production === Corticotropes contain glucocorticoid receptors (GRs) and corticosteroid-binding globulin (CBG, or transcortin). GR is a nuclear receptor that inhibits transcription of ACTH via a negative glucocorticoid recognition element (GRE) that binds cortisol on POMC DNA, but generally transcortin binds glucocorticoids (including cortisol, cortisone, deoxycortisone, and aldosterone) with high affinity and prevents this inhibition. Tonic inhibition of corticotropes requires high concentrations of glucocorticoids, exceeding CBG capacity. This causes ACTH secretion to be vulnerable to inhibition in patients taking glucocorticoids for medical purposes such as treatment of autoimmune disease or as an anti-transplant-rejection medication.
Sources: en.wikipedia.org
== External links == Fibronectin, an Extracellular Adhesion Molecule The Fibronectin Protein Fibronectin at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Fibronectin molecular interactions Overview of all the structural information available in the PDB for UniProt: P02751 (Human Fibronectin) at the PDBe-KB. Overview of all the structural information available in the PDB for UniProt: P11276 (Mouse Fibronectin) at the PDBe-KB.
A fleet of opium clippers on the River Ganges Confessions of a Poppy Tea addict DEA drug information: Opium, morphine, and heroin From Flowers to Heroin, CIA publication Erowid: Opium Opium in India Opium Made Easy by Michael Pollan (originally appeared in Harper's.) House of Opium museum BLTC Research: Speculations on the future of opioids Thailex photo: Traditional method of using opium in Thailand Tsur Shezaf, Writer, The Opium Growers of Sinai Archived November 20, 2009, at the Wayback Machine UNODC – United Nations Office on Drugs and Crime – Afghan Opium Survey 2009 "The Alkaloids of Opium", Scientific American, 20 July 1878, p. 36, historical account on the physiological effects of the first 16 known alkaloids
== Medical uses == Trastuzumab deruxtecan is indicated for the treatment of adults with unresectable (unable to be removed with surgery) or metastatic (when cancer cells spread to other parts of the body) HER2-positive breast cancer who have received two or more prior anti-HER2-based regimens in the metastatic setting and for adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma who have received a prior trastuzumab-based regimen. In May 2022, the US Food and Drug Administration (FDA) expanded the indication to include the treatment of adults with unresectable or metastatic HER2-positive breast cancer who have received a prior anti-HER2-based regimen either in the metastatic setting, or in the neoadjuvant or adjuvant setting and have developed disease recurrence during or within six months of completing therapy. In August 2022, the FDA expanded the indication to include the treatment of unresectable or metastatic HER2-low breast cancer. In April 2024, the FDA expanded the indication to include the treatment of unresectable or metastatic HER2-positive (IHC3+) solid tumors for adults who have received prior systemic treatment and have no satisfactory alternative treatment options.
==== Adipose tissue ==== Serotonin also regulates white and brown adipose tissue function, and adipocytes are capable of producing 5-HT separately from the gut. Serotonin increases lipogenesis through HTR2A in white adipose tissue, and suppressed thermogenesis in brown adipose tissue via Htr3.
Sources: en.wikipedia.org
Using only the egg yolk. Using specialized devices to whip the egg, particularly the egg white into a meringue-like foam before pouring over the rice. A cooking toy called the Kyūkyoku no TKG (Ultimate TKG) was marketed by Takara Tomy Arts in 2017 specifically for this purpose.
===== Virus-mediated fusion of cancer cells ===== The host organism fights viral infection using various strategies. One such strategy is the production of neutralizing antibodies. In response to this production, viruses have developed their own strategies for spreading the infection and avoiding the inactivation by the host produced neutralizing antibodies. Some viruses, and in particular paramyxoviruses, can produce new virus particles by fusing infected and healthy host cells. This fusion leads to the formation of a large multi-nuclear structure (syncytium). Sendai virus, as a representative of Paramyxoviridae, uses this strategy to spread its infection (see the section "Directed cell fusion" below). The virus can fuse up to 50–100 cells adjacent to one primary infected cell. This multi-nuclear formation, derived from several dozens of cells, survives for several days and subsequently releases functional viral particles. It has been demonstrated that the ability of a virus to destroy tumor cells increases along with an increase in the ability of the virus to form large multi-nuclear structures. The transfer of genes that are responsible for the formation of syncytium from the representative of Paramyxoviridae to the representatives of Rhabdoviridae or Herpesviridae makes the recipient viruses more oncolytic. Moreover, the oncolytic potential of paramyxovirus can be enhanced by mutations in the fusion (F) gene protease-cleavage site, which allows the F-protein to be more efficiently processed by cellular proteases.
== Clinical significance == A chyle fistula occurs when defect(s) of lymphatic vessel(s) result in leakage of lymphatic fluid, typically accumulating in the thoracic (pleural) or abdominal (peritoneal) cavities, leading to a chylous pleural effusion (chylothorax) or chylous ascites, respectively. Leakage of lymphatic fluid and decreased chyle volume result in the loss of fluid, electrolytes, proteins, and lymphocytes, leading to complications with nutrition, wound healing, and immunity. Diagnosis of a chyle fistula may be accomplished by analysis of pleural/peritoneal fluid. Identifying the source (localizing the lymphatic defect) is often challenging, but may be accomplished with lymphangiography, which is occasionally associated with a serendipitous therapeutic effect (resolution of the leak), thought to be secondary to a sclerosant effect of the lymphangiography contrast. Because of the extreme friability of the lymphatic vessels, direct repair of defects is impractical. Therefore, treatment of chyle fistulae relies upon either decreased production of lymphatic fluid to allow for healing of lymphatic defect(s) or permanent diversion of lymphatic fluid away from lymphatic defect(s). Decreased production of lymphatic fluid may be accomplished by dietary restriction (or complete replacement of oral intake with total parenteral nutrition), as well as by the medications octreotide (a synthetic analogue of the hormone somatostatin) and orlistat (a lipase inhibitor that decreases absorption of dietary fats).
Sources: en.wikipedia.org
Sealed, desiccated and protected from light, at -20 °C or lower for long-term storage. Short-term storage at refrigerator temperature is common in working laboratories.
Synthesis routes, purification steps and the analytical method used all affect the reported figure. A purity number is only comparable when the chromatographic conditions and detection wavelength are stated.
It reports what the supplier measured on a sample, which is useful but not absolute. Independent mass confirmation on the received lot is the more reliable check.
No. TB-500 is a trade-style label used for a synthetic peptide described as a fragment of thymosin beta-4, while thymosin beta-4 is the full 43-residue protein. The two differ in size and are not interchangeable terms in analytical work.