This is a working overview of mass spectrometry, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-09-22. Anything still debated is marked as such rather than presented as settled.
Large randomised trials in adults with type 2 diabetes and in adults with obesity have reported reductions in body weight and improvements in several cardiovascular risk markers. One outcome trial found a lower incidence of major adverse cardiovascular events in participants with diabetes and established cardiovascular disease. Gastrointestinal effects such as nausea and vomiting are the most frequently reported adverse events and often diminish over time. Changes in lean body mass during weight loss are an area of ongoing investigation. Effects in adolescents and in pregnancy are less well characterised, and current labelling advises against use during pregnancy.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released after nutrient intake. The molecule contains 31 amino acid residues and differs from the native sequence at several positions. A non-natural residue at position eight resists the enzyme that normally truncates the hormone, while a lysine-linked fatty diacid side chain promotes binding to serum albumin. These two modifications extend the circulating half-life from minutes to roughly one week. The peptide is produced by solid-phase synthesis followed by selective acylation, and its identity and purity are confirmed by spectrometric and chromatographic techniques.
The primary target is the GLP-1 receptor, a class B G protein-coupled receptor expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises intracellular cyclic AMP, which potentiates glucose-dependent insulin secretion and lowers glucagon release when blood glucose is elevated. Signalling in the hypothalamus and brainstem is associated with reduced appetite and slower gastric emptying. Because the insulinotropic effect depends on prevailing glucose levels, the hypoglycaemic risk of the peptide alone is described as low in most study settings. The relative contribution of peripheral and central actions remains an active research question.
Stability studies examine how temperature, pH, and moisture influence degradation rates over time. In aqueous solution, hydrolysis and deamidation accelerate as pH moves away from mildly acidic conditions. Light exposure and residual metal ions can also trigger oxidation of susceptible residues. Accelerated aging at elevated temperature is used to estimate shelf life, though extrapolation to room temperature carries uncertainty because individual degradation pathways do not always scale predictably.
Lyophilized semaglutide powder is typically held at minus twenty degrees Celsius for long-term storage. At that temperature, solid-state degradation reactions proceed slowly and the peptide remains intact for extended periods. Repeated freeze-thaw cycles are best avoided because they promote aggregation and can shift the proportion of monomeric peptide present. Working aliquots are often prepared so that each portion is thawed only once, and desiccant is placed inside the vial to limit moisture uptake.
Identity and purity are usually assessed by reverse-phase high-performance liquid chromatography coupled to mass spectrometry. Retention time and observed mass are compared against a reference standard run under identical conditions. Impurity profiles reveal deamidation products, oxidized methionine variants, and truncated fragments that arise during synthesis or storage. Peptide mapping through enzymatic digestion confirms the primary sequence, while amino acid analysis offers an independent check on overall composition.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Acylated GLP-1 receptor agonist | 31-residue synthetic peptide |
| Molecular formula | C187H291N45O59 | established for the free peptide |
| Appearance | White to off-white powder | as supplied before formulation |
| Solubility | Freely soluble in water | aqueous buffers near neutral pH |
| Typical storage | 2 to 8 degrees Celsius, protected from light | powder and solution forms differ in shelf life |
Clinical development of this compound followed earlier short-acting GLP-1 analogues that required frequent injection. Once-weekly subcutaneous formulations entered use after 2017, and an oral formulation using a permeation enhancer later became available. The oral version pairs the peptide with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, a carrier that improves uptake across the gastric epithelium. Interest has expanded from glycaemic control into weight management and metabolic liver disease. Regulatory status and approved indications differ between countries, and the product remains subject to ongoing safety monitoring.
Semaglutide is a synthetic peptide that acts as an agonist at the glucagon-like peptide-1 receptor. It is a structural analogue of human GLP-1(7-37), modified to resist enzymatic degradation by dipeptidyl peptidase-4. The peptide backbone contains alpha-aminoisobutyric acid at position 8, a substitution that stabilises the helix and slows cleavage. A fatty diacid side chain attached through a linker at lysine 34 promotes binding to serum albumin, which extends the circulating half-life. These two modifications together allow less frequent administration than native GLP-1 requires.
Activation of the GLP-1 receptor couples to Gs signalling and raises intracellular cyclic AMP in pancreatic beta cells. The resulting insulin release depends on prevailing glucose concentrations, so the effect is greater when glucose is elevated. Receptor engagement also suppresses glucagon secretion and slows gastric emptying, which flattens post-meal glucose excursions. In the central nervous system, signalling in hypothalamic and brainstem regions is associated with reduced appetite and lower energy intake. Studies continue to examine effects on cardiac, renal and hepatic endpoints; whether those benefits are independent of weight change remains an open question.
Three structural changes define the molecule. At position 8 an alpha-aminoisobutyric acid residue replaces alanine, which blocks dipeptidyl peptidase-4 cleavage. At position 34 arginine replaces lysine, and at position 26 a lysine carries a C18 fatty diacid attached through a short linker. The fatty chain binds serum albumin, and this albumin association reduces renal filtration and enzymatic attack. The unchanged backbone retains the receptor contacts that produce signalling. The free base has the formula C187H291N45O59 and a molecular weight near 4114 daltons.
Receptor activation follows the canonical Gs pathway: binding increases intracellular cyclic AMP, which promotes protein kinase A activity. In pancreatic beta cells this amplifies glucose-dependent insulin release, so secretion rises when blood glucose is high and changes little when it is low. The same signalling suppresses glucagon release from alpha cells and slows gastric emptying. Receptors in the hypothalamus and brainstem are thought to contribute to reduced appetite and lower energy intake. Which of these effects dominates clinical outcomes remains an area of active study.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released by intestinal L cells after food intake. The natural hormone acts on pancreatic and central receptors but is degraded within minutes by dipeptidyl peptidase-4 and other peptidases. Semaglutide belongs to the class of long-acting GLP-1 receptor agonists, a group distinguished by structural changes that slow breakdown and extend circulation time. Its development followed earlier short-acting analogues and reflects a general strategy in peptide drug design: preserve receptor activity while blocking proteolytic clearance.
Reported molecular weight is approximately 4113.6 daltons for the free base, and the peptide is supplied as a lyophilized powder or in buffered liquid form depending on the intended use. It is freely soluble in water when formulated with appropriate excipients, though the unconjugated peptide shows limited stability at neutral pH over long periods. Analytical characterization typically relies on reversed-phase high-performance liquid chromatography and mass spectrometry. Purity specifications for research-grade material commonly exceed ninety-five percent by area. Isotopic and impurity profiles differ between suppliers.
Two principal therapeutic variants exist under separate regulatory filings, one indicated for glycemic control in type 2 diabetes and one for chronic weight management. Both use the same active molecule; differences lie in formulation strength, titration schedule, and labeling. Regulatory agencies in the United States and European Union approved injectable forms in 2017 and 2018 respectively. An oral tablet formulation received approval later, using a carrier molecule to enhance absorption across the gastric epithelium. Labeling differs by jurisdiction and by indication.
Reverse-phase high-performance liquid chromatography is the standard method for purity assessment, separating the peptide from truncated or oxidized variants. Mass spectrometry confirms molecular mass and detects modifications, while ultraviolet absorbance near 280 nanometers supports concentration measurement through tryptophan and tyrosine residues. Circular dichroism can indicate secondary structure, though the peptide is largely helical in solution, and ion-exchange chromatography resolves charge variants. Purity values above 95 percent are typical for research-grade material. Stability studies track degradation over time under defined conditions.
Lyophilized semaglutide is typically stored at temperatures between minus 20 and minus 80 degrees Celsius for long-term preservation. Short-term storage at 2 to 8 degrees Celsius is common for working aliquots. Repeated freeze-thaw cycles can degrade the peptide and are usually avoided. The molecule is hygroscopic in its solid form, so containers should remain sealed with desiccant. Solutions are less stable than powders and are generally prepared fresh. Light exposure is limited because aromatic residues can undergo photo-oxidation.
an aromatic oxo acid + L-glutamate The two substrates of this enzyme are an aromatic amino acid and α-ketoglutaric acid. Its products are the corresponding α-keto acid and L-glutamic acid. For example, the enzyme characterised from Escherichia coli interconverts phenylalanine and phenylpyruvic acid:
== Garden history == Clematis patens C.Morren et Decne. (Kazaguruma), native to Japan, was introduced to Europe in 1836 by Philipp Franz Balthasar von Siebold. Today, it is the most frequently used species for developing large-flowered cultivars. The wild Clematis species, such as Clematis florida, native to China had also made their way into Japanese gardens by the 17th century. These species were also brought to Europe through Japan. Japanese garden selections, mostly cultivated in Edo Period using species that are native to Japan or China, were the first exotic clematises to reach European gardens, in the 18th century, long before the Chinese species were identified in their native habitat at the end of the 19th century. After it arrived in Europe, it acquired several meanings during the Victorian era, famous for its nuanced flower symbolism. It came to symbolize both mental beauty and art as well as poverty.
During another call to her husband, Mays complained of soreness in her arms from having to do compressions on a patient who, she felt, had "no quality of life", adding that if the staff "would have just said DNR (Do Not Resuscitate), he would have went [sic] to sleep when his sugar dropped down to 30." The investigation involved more than 300 interviews; the review of phone, social media, and computer records; the review of thousands of pages of medical records and charts; hours of consulting with forensic experts and endocrinologists; the exhumation of some of the bodies of those who were deemed to have died suspiciously; and the review of thousands of hospital staff and visitor records to assess their potential interactions with the deceased. A "person of interest" was officially identified in the autumn of 2019; the person's name was not disclosed, but authorities later stated that Mays had been a person of interest from the beginning.
An analytical ultracentrifuge has a light source and optical detectors. To allow the light to pass through the analyte during the ultracentrifuge run, specialized cells are required which have to meet high optical standards as well as to resist the centrifugal forces. Each cell consists of a housing, two windows made from optically pure quartz glass, and a centrepiece with one or two sectors and filling holes for the sector(s), closed with a screw plug in the housing. These cell are placed into a rotor cavity with a continuous bore, with a collar at the bottom to retain the cell. By applying specific equipment and adapting measurement parameters several types of experiments can be performed. Most common AUC experiments are sedimentation velocity and sedimentation equilibrium experiments.
Early measurements of coaxial stacking were performed using biochemical assays that studies the relative migration of different nucleic acid molecules based on their conformation and the kind of interactions present. Short DNA molecules containing nicks that could still stack coaxially migrated faster than DNA molecules containing gaps and thus had no coaxial stacking. This could be explained by polymeric properties of DNA where are more rigid rod like molecule will migrate faster along an electrical gradient in a matrix compared to a more flexible molecule. Development of newer techniques such as optical tweezers and the ability to fold DNA nanostructures led to measurement so of DNA bundles and their ability to stack with each other. The force needed to pull these bundles apart using optical tweezers could then be analyzed to measure the base-pair stacking energies. These measurements were performed mainly under non-equilibrium conditions and various extrapolations were made to arrive at the exact values of coaxial stacking between bases. Recent single-molecule studies using DNA nanostructures and DNA-PAINT super-resolution microscopy has allowed for measurement of these interaction between dinucleotides using in-depth kinetic analysis of binding times of short DNA molecules to their complimentary sequences in the presence or absence of DNA-stacking interactions.
Sources: en.wikipedia.org
One more very convincing experiment from Dubna was published in 1966 (though it was submitted in 1965), again using the same two reactions, which concluded that 254No indeed had a half-life much longer than the 3 seconds claimed by Berkeley. Later work in 1967 at Berkeley and 1971 at the Oak Ridge National Laboratory fully confirmed the discovery of element 102 and clarified earlier observations. In December 1966, the Berkeley group repeated the Dubna experiments and fully confirmed them, and used this data to finally assign correctly the isotopes they had previously synthesized but could not yet identify at the time. Thus they claimed to have discovered nobelium in 1958 to 1961.
The study used a combination of existing, cheap drugs ahead of usual radiotherapy treatment. 24 October California-based startup Atom Computing announces a 1,225-qubit quantum computer, the first to break the 1,000+ barrier, which it plans to release in 2024. NASA provides updated details of its Nancy Grace Roman Space Telescope, planned for launch by 2027. JT-60SA, the world's largest fusion reactor, located in Japan, achieves first plasma. A study reviewing the 'planetary vital signs' reports deeply concerning patterns and records, minimal progress of mitigation by humanity, and a set of broad policy recommendations. It represents an annual update to a 2019 study that has been signed by now 15,000 researchers to track the state of climate change and its mitigation. 25 October – Scientists, helped by information derived from the Mars InSight lander, report that the planet Mars has a radioactive magma ocean under its crust. 26 October – Astronomers report studies that suggest for the first time that the planet Venus may have had plate tectonics during ancient times, and, as a result, may have had a cooler more habitable environment, and possibly one capable of generating life forms. 28 October – Positive results are reported in a study with rats of the experimental vaccine calixcoca meant for treating cocaine addiction. Clinical trials in humans are the next step of the study.
==== Microbiomes ==== Lactobacillus fermentation and accompanying production of acid provides a protective vaginal microbiome that protects against the proliferation of pathogenic organisms. The vaginal environment is heavily influenced by lactic acid producing bacteria. Lactobacilli spp. that live in the vaginal canal assist in pH control. If the pH in the vagina becomes too basic, more lactic acid will be produced to lower the pH back to a more acidic level. Lactic acid producing bacteria also act as a protective barrier against possible pathogens such as bacterial vaginosis and vaginitis species, different fungi, and protozoa through the production of hydrogen peroxide, and antibacterial compounds. It is unclear if further use of lactic acid, through fermentation, in the vaginal canal is present.
Built in the Interwar period, it is now the largest in Seine-Maritime with about 1,300 moorings additional moorings were installed in the Vauban basin in 2011–2012. The Havraise Rowing Society has trained many rowers to a high level as Thierry Renault. The Club Nautique Le Havrais (CNH) is the centre of mixed swimming, synchronized swimming, and men's water polo. The Centre Nautique Paul Vatine is the fifth largest club in the country for the number of sports licenses it holds; it ranks second in the Division 1 of the Championship France for Catamaran Clubs. Several major local sportsmen began their career at Le Havre: the swimmer Hugues Duboscq was an Olympic medallist several times. In judo the French team has two members from Le Havre: Dimitri Dragin and Baptiste Leroy. Jerome Le Banner is a professional kick-boxer at world level who participates in the K-1 championship. Finally the navigator Paul Vatine, who was lost at sea in 1999, won the Transat Jacques Vabre several times.
==== Particulates ==== Atmospheric particulate matter, also known as particulates, can be found indoors and can affect the health of occupants. Indoor particulate matter can come from different indoor sources or be created as secondary aerosols through indoor gas-to-particle reactions. They can also be outdoor particles that enter indoors. These indoor particles vary widely in size, ranging from nanomet (nanoparticles/ultrafine particles emitted from combustion sources) to micromet (resuspensed dust). Particulate matter can also be produced through cooking activities. Frying produces higher concentrations than boiling or grilling and cooking meat produces higher concentrations than cooking vegetables. Preparing a Thanksgiving dinner can produce high concentrations of particulate matter, exceeding 300 μg/m3. Particulates can penetrate deep into the lungs and brain from blood streams, causing health problems such as heart disease, lung disease, cancer and preterm birth.
Sources: en.wikipedia.org
==== European Union ==== On 25 September 2008, the EU announced a ban on imports of baby food containing Chinese milk. The European Commission also called for tighter checks on other Chinese food imports; isolated contaminated products were found in the Netherlands, and the French authorities ordered all Chinese dairy products off the shelves; Tesco removed White Rabbit sweets as a precaution from its stores in the United Kingdom.
1927 (Chemistry) Heinrich Otto Wieland — Constitution of bile acids and sterols and their connection to vitamins 1928 (Chemistry) Adolf Otto Reinhold Windaus — Constitution of sterols and their connection to vitamins 1939 (Chemistry) Adolf Butenandt and Leopold Ružička — Isolation and structural studies of steroid sex hormones, and related studies on higher terpenes 1950 (Physiology or Medicine) Edward Calvin Kendall, Tadeus Reichstein, and Philip Hench — Structure and biological effects of adrenal hormones 1965 (Chemistry) Robert Burns Woodward — In part, for the synthesis of cholesterol, cortisone, and lanosterol 1969 (Chemistry) Derek Barton and Odd Hassel — Development of the concept of conformation in chemistry, emphasizing the steroid nucleus 1975 (Chemistry) Vladimir Prelog — In part, for developing methods to determine the stereochemical course of cholesterol biosynthesis from mevalonic acid via squalene
East Tennesseans felt the state had squandered the proceeds from the sale of land in the Hiwassee District (1819) on a failed state bank, rather than on badly needed internal improvements. It wasn't until 1828 that a steamboat, the Atlas, managed to navigate Muscle Shoals and make it upriver to Knoxville. River improvements in the 1830s allowed Knoxville semi-annual access to the Mississippi, though by this time the city's merchants had shifted their focus to railroad construction.
Basic sciences of medicine; this is what every physician is educated in, and some return to in biomedical research. Interdisciplinary fields, where different medical specialties are mixed to function in certain occasions. Medical specialties
Sources: en.wikipedia.org
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and neutral endopeptidases. Semaglutide carries a non-natural amino acid at position eight that blocks that cleavage, and a fatty diacid side chain that binds albumin. The result is a much longer duration of action than the native hormone.
The fatty diacid chain associates strongly with serum albumin, which keeps the peptide in circulation and shields it from rapid renal clearance. Bound peptide is released gradually, producing a sustained receptor signal. This mechanism also reduces the peak-to-trough variation seen with shorter-acting analogues.
The balance between peripheral receptor activation and signalling in the central nervous system is not fully resolved. The extent to which slowed gastric emptying accounts for reduced energy intake, compared with direct effects on appetite circuits, is debated. Long-term effects on lean mass and on tissues outside the gut and brain are still under study.
Manufacturers commonly state multi-year stability when the powder is kept dry and frozen. Actual shelf life depends on residual moisture, vial sealing, and storage temperature. A re-test by chromatography is the only way to confirm remaining purity.