If you have been reading about reversed-phase chromatography and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-01-12. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Identity and purity are checked with chromatographic and mass spectrometric methods. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities, while mass spectrometry confirms the expected molecular mass. A certificate of analysis may report a purity percentage, but the laboratory should still verify the material independently. Common quality concerns include truncated sequences, deamidation, oxidation, and residual solvents from synthesis. Because TB-500 is short, some impurities can differ from the target by only a few mass units.
Reconstitution practices affect downstream measurements. The dry powder is typically dissolved in sterile water or a suitable aqueous buffer, then mixed gently rather than vortexed at high speed. Visible particles or cloudiness suggest incomplete dissolution or contamination and should be investigated. For long-term storage, aliquots should be labeled with concentration, solvent, and date. Open questions include how different buffers alter peptide conformation and whether specific container materials adsorb the peptide. Those variables can change apparent concentration in assays even when the chemical identity is correct.
| 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 |
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
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.
=== "Inflammaging" === "Inflammaging" refers a chronic, sterile, low-grade inflammation that develops with advanced age. It affects the start and progression of diseases that occur due to aging, e.g. type 2 diabetes. It occurs in the skin because when exposed to UV radiation, it damages the epidermal cells, which in turn causes inflammation to occur.
=== Pharmacodynamics === Lemborexant is a dual antagonist of the orexin OX1 and OX2 receptors. It associates and dissociates from the orexin receptors more rapidly than certain other orexin receptor antagonists, such as suvorexant, and this may cause it to have a shorter duration of action.
=== Eye damage === Both rosiglitazone and pioglitazone have been suspected of causing macular edema, which damages the retina of the eye and causes partial blindness. Blindness is also a possible effect of diabetes, which rosiglitazone is intended to treat. One report documented several occurrences and recommended discontinuation at the first sign of vision problems. A retrospective cohort study showed an association between the use of thiazolidinediones and the incidence of diabetic macular edema (DME). Both use was associated with a 2,3 higher risk at 1 year and at 10 year follow-up, rising to 3 if associated with insulin.
== Non-classical examples of PLP == PLP is also found on glycogen phosphorylase in the liver, where it is used to break down glycogen in glycogenolysis when glucagon or epinephrine signals it to do so. However, this enzyme does not exploit the reactive aldehyde group, but instead utilizes the phosphate group on PLP to perform its reaction. Although the vast majority of PLP-dependent enzymes form an internal aldimine with PLP via an active site lysine residue, some PLP-dependent enzymes do not have this lysine residue, but instead have a histidine in the active site. In such a case, the histidine cannot form the internal aldimine, and, therefore, the co-factor does not become covalently tethered to the enzyme. GDP-4-keto-6-deoxymannose-3-dehydratase (ColD) is an example of such an enzyme. Human Serine hydroxymethyltransferase 2 regulates one-carbon transfer reactions required for amino acid and nucleotide metabolism, and exists in dimeric and tetrameric forms. The dimeric SHMT2 variant is a potent inhibitor of the BRISC deubiquitylase enzyme complex, which regulates immune-based cell signaling. Recent studies show that SJMT2 tetramerization is induced by PLP. This prevents interaction with the BRISC deubiqutylase complex, potentially linking vitamin B6 levels and metabolism to inflammation.
Sources: en.wikipedia.org
=== Enzyme cyclization === Cyclization of enzymes by fusing the N- and C-termini of the protein helps elevate the stability of the enzyme against heat. By having SpyTag and SpyCatcher together in the enzyme at the termini, the enzyme will undergo spontaneous cyclization by forming the isopeptide bond. Cyclized beta-lactamase, phytase, firefly luciferase, and xylanase have shown retained enzyme activity following cooling, even after being subjected to heat at 100 °C.
== Academic career == Shulman began his academic career at Harvard Medical School, serving as an instructor and then as an assistant professor of medicine from 1984 to 1987. In 1987, he joined the faculty at Yale University as an assistant professor of medicine. He was promoted to associate professor in 1989 and became a full professor in both internal medicine and cellular and molecular physiology in 1996. From 1987 to 1993, he concurrently served as a lecturer in Yale's Department of Molecular Biophysics and Biochemistry. In 2009, he was appointed the inaugural George R. Cowgill Professor of Physiological Chemistry at Yale University, a position he continues to hold. Shulman served as Associate Director of both the Yale Diabetes Endocrinology Research Center and the Yale Medical Scientist Training Program from 1992 to 2012. In 2012, he became Co-Director of the Yale Diabetes Research Center. He has served on the editorial boards of journals including the Journal of Clinical Investigation, Cell Metabolism, Science Translational Medicine, and Proceedings of the National Academy of Sciences. He was also an Investigator of the Howard Hughes Medical Institute for 21 years and is now an Investigator Emeritus.
== Signs and symptoms == Signs and symptoms of Huntington's disease most commonly become noticeable between the ages of 30 and 50 years, but they can begin at any age and present as a triad of motor, cognitive, and psychiatric symptoms. When developed in an early stage, it is known as juvenile Huntington's disease. In 50% of cases, the psychiatric symptoms appear first. These can precede the motor symptoms by many years. Disease progression is often described in early stages, middle stages and late stages with an earlier prodromal phase. In the early stages, subtle personality changes, problems in cognition and physical skills, irritability and mood swings occur, all of which may go unnoticed. Almost everyone with HD eventually exhibits similar physical symptoms, but the onset, progression, and extent of cognitive and behavioral symptoms vary significantly between individuals. The most characteristic initial physical symptoms are jerky, random and uncontrollable movements called chorea. Many people are not aware of their involuntary movements, or impeded by them. Chorea may be initially exhibited as general restlessness, small unintentionally initiated or uncompleted motions, lack of coordination, or slowed saccadic eye movements. These minor motor abnormalities usually precede more obvious signs of motor dysfunction by at least three years. The clear appearance of symptoms such as rigidity, writhing motions, or abnormal posturing appear as the disorder progresses. These are signs that the system in the brain that is responsible for movement has been affected.
Patients with CSF leaks have been noted to have very low or even negative opening pressures during lumbar puncture. However, patients with confirmed CSF leaks may also demonstrate completely normal opening pressures. In 18–46% of cases, the CSF pressure is measured within the normal range. Analysis of spinal fluid may demonstrate lymphocytic pleocytosis and elevated protein content or xanthochromia. This is hypothesized to be due to increased permeability of dilated meningeal blood vessels and a decrease of CSF flow in the lumbar subarachnoid space.
Resveratrol and related polyphenols (usually as "grape seed extract") are often included. Yohimbine has also been used as an ingredient (often as Pausinystalia johimbe extract), as a supposed testosterone booster and fat-loss agent, but it has been associated with dangerous side effects, and is also a prescription medicine in many countries. Phenylpiracetam is also sometimes used as an ingredient for its nootropic and stimulant effects. Capsaicin is sometimes used as an ingredient in gelcap pre-workout formulations, both as a supoosed weight loss aid and for improvement of endurance. Plant extracts, such as Ginkgo biloba, Panax ginseng, Rhodiola rosea and Huperzine A (from Huperzia serrata), are sometimes included for their supposed ability to improve endurance and mental clarity, despite limited evidence for efficacy. Ecdysteroids, such as ecdysterone and turkesterone, and other plant derived steroid like compounds such as 5α-Hydroxylaxogenin are sometimes used as ingredients, despite inconclusive results as to their supposed anabolic effects. Prohormones such as DHEA, CDMA, 1-androstenediol and 7α-methyl-19-norandrostenedione were widely used in pre-workout formulations prior to 2014 when they were formally banned. These compounds are not anabolic agents in their own right, but are metabolised into anabolic steroids of a type which at the time were not restricted.
Sources: en.wikipedia.org
21,000, 5 November 2010 - The SENSEX closed at 21,004.96, for its first close above the 21,000 mark. It would take nearly three years for the index to make its next close above this level. 22,000, 24 March 2014 - The SENSEX closed at 22,055.48, for its first close above the 22,000 mark. For the first time, the SENSEX zoomed ahead of the Hang Seng Index. 23,000, 12 May 2014 - The SENSEX closed at 23,551.00, for its first close above the 23,000 mark, 24,000, 16 May 2014 - The SENSEX closed at 24,121.74, for its first close above the 24,000 mark, Breaking all previous records and above all other indexes in the world. 25,000, 5 June 2014 - The SENSEX closed at 25,019.51, for its first close above the 25,000 mark, 26,000, 7 July 2014 - The SENSEX closed at 26,123.55, for its first close above the 26,000 mark, 27,000, 2 September 2014 - The SENSEX closed at 27019.39, for its first close above the 27,000 mark, 28,000, 5 November 2014 - The SENSEX crossed 28,000 mark, on 5 November 2014. This is the seventh 1000-point milestone the index has crossed in 2014, breaking the six 1000-point record set in 2007.
== Clinical use == European Association of Urology (EAU) guidelines recognise that PSMA can provide accurate staging, however there is a lack of outcome data to inform further management. The American Society of Clinical Oncology (ASCO) guidelines for imaging of advanced prostate cancer also recommend PSMA imaging (among other PET radiopharmaceuticals), while acknowledging that these are not FDA approved and therefore limited to a clinical trial or other controlled research setting. Although PSMA PET imaging has shown clear superiority over conventional CT and bone scans for detecting prostate cancer, comparative studies assessing different PSMA ligands, such as 68Ga-PSMA-11 and 18F-DCFPyL, remain limited. A 2024 overview of reviews published in Seminars of Nuclear Medicine concluded that while evidence gaps remain for some outcomes and most systematic reviews are at high or unclear risk of bias, the evidence base is broadly supportive of 18F PSMA PET/CT in patients with high-risk prostate cancer or biochemical recurrence
Peptide computing is a form of computing which uses peptides, instead of traditional electronic components. The basis of this computational model is the affinity of antibodies towards peptide sequences. Similar to DNA computing, the parallel interactions of peptide sequences and antibodies have been used by this model to solve a few NP-complete problems. Specifically, the hamiltonian path problem (HPP) and some versions of the set cover problem are a few NP-complete problems which have been solved using this computational model so far. This model of computation has also been shown to be computationally universal (or Turing complete). This model of computation has some critical advantages over DNA computing. For instance, while DNA is made of four building blocks, peptides are made of twenty building blocks. The peptide-antibody interactions are also more flexible with respect to recognition and affinity than an interaction between a DNA strand and its reverse complement. However, unlike DNA computing, this model is yet to be practically realized. The main limitation is the availability of specific monoclonal antibodies required by the model.
Actinic granuloma (O'Brien granuloma) Annular elastolytic giant cell granuloma (giant cell elastophagocytosis, Meischer's granuloma, Miescher's granuloma of the face) Annular sarcoidosis Benign cephalic histiocytosis (histiocytosis with intracytoplasmic worm-like bodies) Congenital self-healing reticulohistiocytosis (Hashimoto–Pritzker disease, Hashimoto–Pritzker syndrome) Erythrodermic sarcoidosis Generalized eruptive histiocytoma (eruptive histiocytoma, generalized eruptive histiocytosis) Generalized granuloma annulare Giant cell reticulohistiocytoma (solitary reticulohistiocytoma, solitary reticulohistiocytosis) Granuloma annulare in HIV disease Granuloma multiforme (Mkar disease, granuloma multiforme (Leiker)) Hand–Schüller–Christian disease Heerfordt's syndrome Hereditary progressive mucinous histiocytosis Hypopigmented sarcoidosis Ichthyosiform sarcoidosis Indeterminate cell histiocytosis Interstitial granulomatous drug reaction Langerhans cell histiocytosis (histiocytosis X) Letterer–Siwe disease Localized granuloma annulare Löfgren syndrome Lupus pernio Morpheaform sarcoidosis Mucosal sarcoidosis Multicentric reticulohistiocytosis Necrobiotic xanthogranuloma (necrobiotic xanthogranuloma with paraproteinemia) Non-X histiocytosis Papular sarcoid Papular xanthoma Patch-type granuloma annulare (macular granuloma annulare) Perforating granuloma annulare Progressive nodular histiocytosis Reticulohistiocytoma Scar sarcoid (sarcoidosis in scars) Sea-blue histiocytosis Subcutaneous granuloma annulare (deep granuloma annulare, pseudorheumatoid nodule) Subcutaneous sarcoidosis (Darier–Roussy disease, Darier–Roussy sarcoid) Systemic sarcoidosis Ulcerative sarcoidosis Xanthoma disseminatum (disseminated xanthosiderohistiocytosis, Montgomery syndrome)
MDMA was first synthesized and patented in 1912 by Merck chemist Anton Köllisch. At the time, Merck was interested in developing substances that stopped abnormal bleeding. Merck wanted to avoid an existing patent held by Bayer for one such compound: hydrastinine. Köllisch developed a preparation of a hydrastinine analogue, methylhydrastinine, at the request of fellow lab members, Walther Beckh and Otto Wolfes. MDMA (called methylsafrylamin, safrylmethylamin or N-Methyl-a-Methylhomopiperonylamin in Merck laboratory reports) was an intermediate compound in the synthesis of methylhydrastinine. Merck was not interested in MDMA itself at the time. On 24 December 1912, Merck filed two patent applications that described the synthesis and some chemical properties of MDMA and its subsequent conversion to methylhydrastinine. Merck records indicate its researchers returned to the compound sporadically. A 1920 Merck patent describes a chemical modification to MDMA. MDMA's analogue 3,4-methylenedioxyamphetamine (MDA) was first synthesized in 1910 as a derivative of adrenaline. Gordon A. Alles, the discoverer of the psychoactive effects of amphetamine, also discovered the psychoactive effects of MDA in 1930 in a self-experiment in which he administered a high dose (126 mg) to himself. However, he did not subsequently describe these effects until 1959. MDA was later tested as an appetite suppressant by Smith, Kline & French and for other uses by other groups in the 1950s. In relation to the preceding, the psychoactive effects of MDA were discovered well before those of MDMA.
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 dry powder is normally kept at -20 °C, protected from light and moisture. Reconstituted solutions are often divided into aliquots and stored at -80 °C to reduce freeze-thaw damage.