mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-07-04 and is reviewed periodically as new material appears.
Discussion of the compound frequently appears alongside other short peptides described as fragments of larger proteins. That grouping is convenient but can be misleading, because fragment length, charge, and modification state determine how a peptide behaves in solution and in any experimental system. A seven-residue acetylated peptide and a full-length protein differ in mass by roughly an order of magnitude, and they cannot be assumed to share distribution or binding properties. Precision about which molecule is under discussion is the single most useful step when reading such material.
TB-500 is a shorthand label used in supplier catalogs and online discussion for a short synthetic peptide described as a fragment of thymosin beta-4. Most product listings present it as the N-terminally acetylated heptapeptide Ac-LKKTETQ, a sequence corresponding to the actin-binding region of the parent protein. The name is not a formal chemical designation and does not appear in standard nomenclature systems. Because labeling practices vary between vendors, two products sold under the same name may not contain the same molecule, and the stated sequence should be treated as a claim rather than a fixed definition.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
| Property | Value | Notes |
|---|---|---|
| Reported sequence | Ac-LKKTETQ | Described in most listings as the actin-binding region of thymosin beta-4 |
| Reported molecular weight | Approximately 889 Da | Value shifts with the stated sequence; compare against the certificate of analysis |
| Parent protein length | 43 amino acids | Thymosin beta-4; the fragment covers only a small part of it |
| Common synonyms | TB4 fragment; thymosin beta-4 fragment | Trade-style names rather than formal nomenclature |
| Formal monographs | Not established | Labeling conventions differ by supplier and region |
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
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.
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.
Body mass index (BMI) is a value used to get a general sense of a person's overall mass and is calculated using a person's height and weight. It is more often used than weight alone to determine if an individual is underweight, normal weight, overweight, or obese. The following two equations can used to calculate BMI depending on the units used for height (meters vs. inches) and weight (kilograms vs. pounds):
Long before the born secret issues associated with the restricted data provisions of the US Atomic Energy Act of 1946, the US Invention Secrecy Act of 1951, and the US Patent and Trademark Law Amendments Act of 1980 and/or the increasing concerns with respect to the on-going biopiracy of natural products, and in the early 20th-century atmosphere of cultural change — not only in the proliferation of vocational universities, rather than research universities, but also in the gradual move from the disciplinary concentration on "pure science" and, perhaps, aspects of "applied science", to that of fostering "industrial science" in both primary and secondary industries — the ethical question of whether or not those universities devoted to "pure science" (viz., the discovery/creation, distillation, refinement, diffusion, and the free dissemination of knowledge for the benefit of the public) should have any interest in "applied science", and further, whether they should have any commercial interest in the products of their research and, in particular, whether they should seek patents for their discoveries. In his 1926 Presidential address to the Society of American Bacteriologists (HZ.1), Hans Zinsser spoke against "the growing tendency on the part of medical scientific workers, and bacteriologists especially, to patent discoveries of practical therapeutic and public health value" (p.157).
=== tim-tin === Tim-AK Timecelles timefurone (INN) timegadine (INN) timelotem (INN) Timentin timepidium bromide (INN) timiperone (INN) timirdine (INN) timobesone (INN) timofibrate (INN) Timolide timolol (INN) timonacic (INN) timoprazole (INN) Timoptic tinabinol (INN) Tinactin Antifungal Tinaderm Tinamed tinazoline (INN) TinBen Tindal Tindamax Ting tinidazole (INN) tinisulpride (INN) tinofedrine (INN) tinoridine (INN) Tinver tinzaparin sodium (INN)
Sources: en.wikipedia.org
The membership of the PSC was reduced from nine to seven, with Xi and Li Keqiang retaining their seats; the other five members were new. In December 2012, Xi visited Guangdong in his first trip outside Beijing since taking the general secretaryship. The overarching theme of the trip was to call for further economic reform and a strengthened military. Xi was elected president on 14 March 2013, in a confirmation vote during the first session of the 12th National People's Congress in Beijing. He received 2,952 for, one vote against, and three abstentions. He replaced Hu Jintao, who retired after serving two terms. Xi was also elected as the chairman of the state CMC. He subsequently nominated Li Keqiang to be the premier, who was then appointed by the NPC.
== Notes == ^ TH: One of the few exceptions where a drug shows F of over 100% is theophylline. If administered as an oral solution F is 111%, since the drug is completely absorbed and first-pass metabolism in the lung after intravenous administration is bypassed. ^ OB: Reference listed drug products (i.e., innovator's) as well as generic drug products that have been approved based on an Abbreviated New Drug Application are given in FDA's Orange Book.
=== History === During World War I, munitions workers in France fell ill and some died from DNP exposure. Stanford University academic Maurice L. Tainter learned of DNP's effect in raising the metabolic rate and causing weight loss and pioneered its use as a weight loss drug. Although he was aware of DNP's narrow therapeutic index, Tainter tried the drugs on obese patients and published successful results in 1933; average weight loss was 20 pounds (9.1 kg) and most recipients did not report adverse effects. In 1934, Tainter estimated that at least 100,000 people had been treated with DNP in the United States during its first year on the market and there had been three reported fatalities connected to the drug. Tainter argued that DNP was highly effective in raising the metabolic rate (up to 50 percent) and avoided the negative circulatory effects of desiccated thyroid, another weight loss drug in use at the time.
== Medical training and career == Though born in Oklahoma City, Wilson grew up in Whittier, California. He completed his undergraduate degree in biology from California State University, Fullerton in 1974 and a master's degree in molecular biology and biochemistry from University of California, Irvine in 1977. He received his doctor of medicine degree from University of California, San Diego in 1984. The early part of his career saw him completing residency at the Mayo Clinic and taking professor and research roles at various universities. He served as a professor and Chair of the Department of Ophthalmology at the University of Washington in Seattle from 1998 to 2003, and was named Grace E. Hill Endowed Chair in Vision Research. Since 2003, he has been professor of ophthalmology and staff cornea and refractive surgeon at the Cleveland Clinic in Ohio, and he has served as the cornea and refractive fellowship director there 2006-2017. Wilson is the inventor of topical losartan treatment for corneal scarring/fibrosis. Wilson's laboratory studying corneal wound healing was funded by the National Eye Institute and the U.S. Department of Defense from 1993 to 2025.
Sources: en.wikipedia.org
Most listings describe it as a short acetylated peptide with the sequence Ac-LKKTETQ, presented as a region of thymosin beta-4. The label is a trade-style name rather than a standardized chemical name, so the exact content of a given vial depends on the supplier.
No. Thymosin beta-4 is a protein of 43 amino acids, while TB-500 is described as a short fragment of it. The two differ in size, structure, and the range of interactions each can support.
Naming for research peptides is not centrally coordinated, so vendors set their own labels and specifications. Differences in stated sequence, molecular weight, or purity documentation usually trace back to those independent labeling choices.
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.