deamidation raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-10-21. Anything still debated is marked as such rather than presented as settled.
Degradation proceeds along several parallel routes. Deamidation of asparagine and glutamine residues generates charged variants that shift retention time in chromatographic analysis. Oxidation targets methionine and can be accelerated by trace metals or dissolved oxygen. Non-covalent aggregation produces dimers, oligomers, and larger species that are difficult to reverse. Isomerisation at aspartate residues is slower but measurable under thermal stress. The distribution among these pathways depends on pH, buffer composition, ionic strength, and the presence of excipients such as sugars or surfactants.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nm is the standard purity method, reported as area percent. Mass spectrometry, usually with electrospray ionisation, confirms identity and reveals covalent modifications. Size-exclusion chromatography quantifies aggregates and fragments. Peptide mapping after enzymatic digestion localises changes to specific sequence regions. Circular dichroism and infrared spectroscopy report on secondary structure, while light scattering tracks particle formation in liquid formulations. No single technique captures every quality attribute.
Quantification and purity assessment rely on separation methods coupled to optical or mass detection. Reversed-phase high-performance liquid chromatography resolves the intact peptide from related impurities and is the standard assay technique. Size-exclusion chromatography measures aggregates, while ion-exchange chromatography separates charge variants produced by deamidation. Mass spectrometry confirms identity and detects mass shifts of a few daltons. In biological matrices, liquid chromatography with tandem mass spectrometry is often used because immunoassays can cross-react with endogenous GLP-1 or with circulating fragments.
As a peptide, semaglutide is sensitive to conditions that break amide bonds or modify side chains. Deamidation of asparagine and glutamine residues, oxidation of methionine and tryptophan, and non-covalent aggregation are the main degradation routes described in published stability work. Rate depends strongly on pH, buffer species, ionic strength, temperature and exposure to light. Formulators therefore choose a defined solution pH and often add excipients such as phosphate buffer, propylene glycol and phenol, each of which plays a separate role in pH control, tonicity or preservation.
Storage guidance for the finished injectable product distinguishes the unused state from the in-use state. Before first use, pens are kept refrigerated between 2 and 8 degrees Celsius, protected from light, and never frozen, since freezing can disrupt the peptide or the device. After first use, label instructions in several markets permit storage at room temperature up to about 30 degrees Celsius for a limited number of days. Solid research-grade material is normally held at or below minus 20 degrees Celsius, often with desiccant, and allowed to equilibrate before opening.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilised powder | visual inspection of solid |
| Solubility | Freely soluble in water, pH dependent | buffer choice affects clarity |
| Typical storage | -20 °C, desiccated, protected from light | solution form kept at 2-8 °C |
| Primary purity method | RP-HPLC with UV detection, 214-220 nm | reported as area percent |
| Identity confirmation | LC-ESI-MS, approximately 4114 Da | compared with theoretical mass |
Routine characterisation of the peptide relies on reversed-phase high-performance liquid chromatography, often paired with ultraviolet detection near 214 nanometres. Related substances such as deamidated, oxidised, and truncated sequences elute at characteristic positions and are quantified by area percentage. Electrospray ionisation mass spectrometry confirms the molecular mass and can resolve some closely related variants. Peptide mapping after enzymatic digestion provides sequence-level verification and is useful when a full identity profile is required. Method parameters such as column chemistry, gradient, and mobile-phase pH influence the separation and must be reported alongside results.
Material described as research-grade is not necessarily manufactured to pharmaceutical standards, and purity figures depend on the method used to obtain them. A certificate of analysis states the measured purity, the analytical technique, and the batch identifier, but the underlying data are not always included. Independent testing by a second laboratory is a common way to confirm identity and purity. Uncertainties remain about how storage history affects long-term stability, and about how well results from one laboratory transfer to another. Documentation of handling conditions supports comparison between batches.
Peptides are sensitive to temperature, light, oxygen, and repeated freeze-thaw cycles. Semaglutide in dry form is generally held at refrigerated temperatures, while reconstituted solutions require a defined short-term storage window. Vials should be kept in secondary packaging to limit photodegradation, and exposure to alkaline conditions is avoided because it accelerates chemical degradation. Adsorption to glass and some plastics can reduce the measured concentration of dilute solutions, so low-binding polypropylene containers are preferred for analytical work. Each transfer step introduces a small risk of contamination, and closed handling practices reduce that risk.
Development began in the early 2010s with the goal of extending GLP-1 activity beyond the brief window achieved by native peptide infusion. The earliest approved formulation was a subcutaneous injection given once weekly. A later oral tablet pairs the peptide with an absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, usually shortened to SNAC. That carrier lowers local pH and helps the peptide cross gastric tissue. Both routes deliver the same active molecule.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, a gut hormone released after meals. Its backbone retains the GLP-1 sequence but incorporates two substitutions that slow enzymatic breakdown by dipeptidyl peptidase-4. A short polyethylene glycol linker and a C18 fatty diacid are attached to the peptide chain, allowing the molecule to bind serum albumin and remain in circulation far longer than the native hormone. The result is a circulating half-life measured in days rather than the minutes typical of endogenous GLP-1.
GLP-1 receptors are expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises cyclic AMP, enhances glucose-dependent insulin secretion, and suppresses glucagon release when blood glucose is high. Effects on gastric emptying and on hypothalamic appetite circuits reduce energy intake. Because insulin release remains glucose-dependent, the risk of hypoglycemia is low when the drug is used alone. The precise contribution of each pathway to body weight change in humans remains an area of active investigation.
Clinical studies of semaglutide generally measure glycated hemoglobin, fasting plasma glucose, body weight, and composite cardiovascular endpoints. The SUSTAIN program enrolled adults with type 2 diabetes, while the STEP program focused on obesity without diabetes. Administration follows a stepwise escalation schedule designed to limit gastrointestinal effects during the first weeks. Reported outcomes include mean percentage weight change, the proportion of participants reaching defined weight-loss thresholds, and rates of nausea, vomiting, and diarrhea. Long-term data on durability after treatment stops are still limited and remain a topic of ongoing research.
Activity-based proteomics – a branch of proteomics that uses covalent enzyme inhibitors as reporters to monitor enzyme activity. Antimetabolite – an enzyme inhibitor that is used to interfere with cell growth and division Transition state analogue – a type of enzyme inhibitor that mimics the transition state of the chemical reaction catalysed by the enzyme
Tramadol and tapentadol carry additional risks associated with their dual effects as SNRIs and can cause serotonin syndrome and seizures. Despite these risks, there is evidence to suggest that these drugs have a lower risk of respiratory depression compared to morphine.
=== 15 March === Ukroboronprom, with the help of a "NATO country", started manufacturing 125 mm smoothbore ammunition for Ukraine's Soviet-era tanks. Also being manufactured were 120 mm mortar rounds, 122 mm and 152 mm artillery shells. The production of projectiles is completely dispersed over a large number of cities. This is part of a larger effort by Ukraine to manufacture ammunition as Western donors have reached into their own stockpiles. Sébastien Lecornu, Minister of Armed Forces for France, announced that AMX-10 RC armored fighting vehicles have arrived in Ukraine.
=== Wound healing macrophages === Interleukin 4, secreted by granulocytes after tissue damage or by adaptive immune cells within a Th2 response, causes macrophages to secrete minimal amounts of pro-inflammatory cytokines and to have lower activity against intracellular pathogens. They also promote extracellular matrix synthesis via production of ornithine, via arginase; this is used as a precursor for extracellular matrix components. The overall result is a macrophage population that promotes wound healing. The specific roles macrophages play in the Th2 response are still under investigation.
Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic meter. Stars, planets, and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object. The Earth's atmospheric pressure drops to about 32 millipascals (4.6×10−6 psi) at 100 kilometres (62 mi) of altitude, the Kármán line, which is a common definition of the boundary with outer space. Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the Sun and the dynamic pressure of the solar winds, so the definition of pressure becomes difficult to interpret. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre. But although it meets the definition of outer space, the atmospheric density within the first few hundred kilometers above the Kármán line is still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region, called low Earth orbit, and must fire their engines every couple of weeks or a few times a year (depending on solar activity).
Sources: en.wikipedia.org
Following his conviction on 12 May, David Boyd is sentenced to a minimum term of 29 years in prison for Nikki Allan's murder. The Cabinet Office refers former prime minister Boris Johnson to the police following fresh allegations of rule breaches during the COVID-19 pandemic. 24 May Inflation is reported to have fallen from 10.1% in March to 8.7% in April. Food price growth remains close to record highs, at 19.1%. Prime Minister Rishi Sunak confirms that Home Secretary Suella Braverman's handling of a speeding offence did not breach ministerial rules and that she will not face an investigation. 25 May Net migration into the UK during 2022 is reported to have reached a record high of 606,000, with immigration estimated at 1.2m and emigration at 557,000. Around 114,000 people came from Ukraine and 52,000 from Hong Kong. Three activists from climate change protest group Just Stop Oil are arrested for criminal damage after disrupting the Chelsea Flower Show. Armed officers arrest a man after he crashes a car into the gates of Downing Street. The incident is not terrorism related. 26 May British Cycling announces that transgender women are to be banned from the female category of its competitions, following a nine-month review and consultation. This follows the March ban by UK Athletics. Phillip Schofield announces he is leaving ITV, following his recent departure from This Morning amid controversy over the relationship he had with a "much younger" male colleague. Passengers arriving into the UK face delays at several airports after passport e-gates stop working.
The wombat is a marsupial that is often considered to be the marsupial equivalent of the North American groundhog. The fossa of Madagascar looks like a small cat. Fossa have semi-retractable claws. Fossa also has flexible ankles that allow it to climb up and down trees head-first, and also support jumping from tree to tree. Its classification has been controversial because its physical traits resemble those of cats, but is more closely related to the mongoose family, (Herpestidae) or most likely the family Malagasy carnivores family, (Eupleridae). The raccoon dog of Asia looks like the raccoon of North America (hence its scientific name Procyonoides) due to its black face mask, stocky build, bushy appearance, and ability to climb trees. Despite their similarities, it is actually classified as part of the dog family (Canidae). Gliders or passive flight has developed independently in flying squirrels, Australian marsupial, lizards, paradise tree snake, frogs, gliding ants and flying fish and the ancient volaticotherium that lived in the Jurassic Period looked like a flying squirrel, but is not an ancestor of squirrels. Amynodontidae, a family of extinct rhinoceroses that are thought to have looked and behaved like squat, aquatic, hippopotamuses. Trichromatic color vision, separate blue, green and red vision, is found only in a few mammals and came about independently in humans, Old World monkeys and the howler monkeys of the New World, and a few Australian marsupials.
In 2025, Medtronic was included in Forbes lists of America's Best Large Employers. In March 2026, Medtronic separated its diabetes business into MiniMed Group, Inc., which completed an initial public offering on March 9. Medtronic retained approximately 89.86% of MiniMed following the offering, while MiniMed became a separately publicly traded company on the Nasdaq. In September 2026, Medtronic launched an exchange offer as part of its planned separation of MiniMed. The offer covers up to 225,361,295 newly issued MiniMed common shares in exchange for Medtronic ordinary shares, representing approximately 80.1% of MiniMed's outstanding shares. If the exchange offer is oversubscribed, Medtronic intends to exchange additional shares of MiniMed representing its remaining interest, which would result in MiniMed becoming independent of Medtronic.The exchange offer is scheduled to expire on October 9, 2026, unless extended or terminated.
If the individual has refractory hypertension (persistent hypertension on the maximum doses of three different classes of antihypertensive agents), involvement of the renal arteries in the aortic dissection plane should be considered.
Sources: en.wikipedia.org
=== Controlled atmospheres === Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography, because it is inert. Because of its inertness, thermally and calorically perfect nature, high speed of sound, and high value of the heat capacity ratio, it is also useful in supersonic wind tunnels and impulse facilities.
=== Pharmacodynamics === 2C-T-36 has a Ki of 0.35 nM at the serotonin 5-HT2A receptor, and an EC50Tooltip half-maximal effective concentration of 4.1 nM at the serotonin 5-HT2A receptor and 7.3 nM at the serotonin 5-HT2C receptor, compared to 88 nM at the serotonin 5-HT2B receptor. It is a potent, selective, long acting, and orally active agonist for the serotonin 5-HT2A and 5-HT2C receptors and produces psychedelic-like responding in several different animal species. The interactions of 2C-T-36 with numerous other receptors and targets have also been described.
=== Pharmacokinetics === Buserelin is ineffective via oral administration due to first-pass metabolism in the gastrointestinal tract. Its bioavailability is 2.5 to 3.3% by intranasal administration and 70% by subcutaneous injection. The plasma protein binding of buserelin is approximately 15%. The metabolism of buserelin occurs in the liver, kidneys, and gastrointestinal tract and is mediated by peptidases, specifically pyroglutamyl peptidase and chymotrypsin-like endopeptidase. The elimination half-life of buserelin regardless of route of administration is about 72 to 80 minutes. Buserelin and its metabolites are eliminated in urine and bile, with approximately 50% of buserelin excreted in urine unchanged.
Adenylyl-sulfate reductase (glutathione) (EC 1.8.4.9) is an enzyme that catalyzes the chemical reaction AMP + sulfite + glutathione disulfide ⇌ {\displaystyle \rightleftharpoons } adenylyl sulfate + 2 glutathione The 3 substrates of this enzyme are adenosine monophosphate, sulfite, and glutathione disulfide, whereas its two products are adenylyl sulfate and glutathione. This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with a disulfide as acceptor. The systematic name of this enzyme class is AMP,sulfite:glutathione-disulfide oxidoreductase (adenosine-5'-phosphosulfate-forming). Other names in common use include 5'-adenylylsulfate reductase (also used for, internal_xref(ec_num(1,8,99,2))), AMP,sulfite:oxidized-glutathione oxidoreductase, (adenosine-5'-phosphosulfate-forming), and plant-type 5'-adenylylsulfate reductase. In plants, APS is reduced by the plastidic enzyme APS reductase (APR; EC 1.8.4.9) in the presence of physiological concentrations of reduced glutathione (GSH), which acts as an electron donor.
Equine chorionic gonadotropin Gonadotropin preparations Human placental lactogen Pregnancy hormones Triple test, a screening test in pregnancy The Weight-Loss Cure "They" Don't Want You to Know About, a book written by Kevin Trudeau Chorionic+Gonadotropin at the U.S. National Library of Medicine Medical Subject Headings (MeSH) "History of pregnancy test". U.S. National Institutes of Health. Archived from the original on 2011-01-13. Retrieved 2011-01-10.
Sources: en.wikipedia.org
Reverse-phase high-performance liquid chromatography with ultraviolet detection is the usual choice, with results reported as area percent. Complementary methods such as size-exclusion chromatography and mass spectrometry are needed because a single separation cannot resolve every impurity class. Purity figures are therefore method dependent and should always be read alongside the technique used.
Oxidation mainly affects methionine residues and is promoted by dissolved oxygen, trace transition metals, and prolonged exposure to light. Buffer choice and the presence of antioxidants in a formulation can alter the rate appreciably. Because the products differ in mass by only a few units, mass spectrometry is often required to detect them.
Published data on long-term ambient stability are limited, so the question remains open rather than settled. Short excursions during transport are common in practice, and many suppliers use insulated packaging with cold packs. Where stability data are absent, cold-chain handling with temperature logging is the safer approach.
Ice formation concentrates solutes and can mechanically stress the peptide or damage the delivery device. Thawing afterwards may leave aggregates that are not visible to the eye. Refrigeration keeps the solution above its freezing point while slowing chemical degradation.