Everything below concerns deamidation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-16. Numbers and descriptions here follow the published literature rather than marketing material.
Native GLP-1 is degraded rapidly by dipeptidyl peptidase-4. Semaglutide resists this cleavage because alanine at position 8 is replaced by alpha-aminoisobutyric acid. A second substitution at position 34 introduces arginine, which further stabilizes the peptide. The most distinctive modification is a spacer and C18 fatty diacid attached at lysine 26, enabling strong albumin affinity. These three changes together produce a half-life measured in days rather than minutes, and the same structural logic underlies other long-acting analogs in this class.
Semaglutide is a synthetic peptide analog of glucagon-like peptide-1, a hormone released from intestinal L-cells after food intake. It contains 31 amino acids and differs from native GLP-1 through modifications that slow enzymatic breakdown. The peptide was developed to extend the short circulating half-life of endogenous GLP-1, which is measured in minutes. Researchers introduced the compound in the early 2010s. Two backbone changes and a fatty acid side chain define its structure, distinguishing it from earlier GLP-1 receptor agonists.
Quality control for peptide material focuses on identity, purity, content and the profile of impurities. Common degradants include deamidated and oxidised forms, plus aggregates formed during storage or handling. Forced degradation studies under heat, light, acid and peroxide help define which conditions accelerate change and which analytical methods detect it. Limits for individual impurities are set by pharmacopoeial monographs or manufacturer specifications. How much a given impurity affects biological activity is often uncertain, and conclusions may depend on the assay used.
Solid peptide material is generally kept at reduced temperature to limit degradation. Short-term storage at 2 to 8 degrees Celsius is common, while longer archival storage at minus 20 degrees Celsius or below is typical for lyophilised powder. Vials should remain sealed and protected from light, because ultraviolet exposure can oxidise susceptible residues. Repeated freeze-thaw cycles are avoided, as they promote aggregation and loss of soluble material. Solutions are less stable than solids and are usually prepared close to the time of use.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | 31 amino acids |
| Backbone modification | Aib at position 8 | Blocks DPP-4 cleavage |
| Fatty acid chain | C18 diacid | Supports albumin binding |
| Native half-life | 1 to 2 minutes | Endogenous GLP-1 |
| Analog half-life | Approximately one week | Extended by albumin binding |
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.
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.
Quality control for research material typically involves reversed-phase HPLC for purity and identity, mass spectrometry for molecular weight confirmation, and Karl Fischer titration for residual water content. Peptide content is often reported as the mass of actual peptide rather than total powder mass, since counterions and water contribute to the latter. A certificate of analysis should list the method used for each specification. Limits and acceptance criteria vary by supplier and by intended application.
Handling practices center on minimizing contamination and adsorption. Lyophilized peptide tends to accumulate static charge, so weighing is done with antistatic measures and calibrated balances. Reconstitution with appropriate solvent should be gentle, avoiding vigorous vortexing that generates foam and shear. Solutions are typically aliquoted before freezing to reduce repeated temperature cycling. Personal protective equipment and a fume hood are standard for powder handling.
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.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, developed by Novo Nordisk and first approved in 2017 for type 2 diabetes. It belongs to the incretin mimetic class, a group of agents that reproduce the glucose-dependent actions of endogenous GLP-1. The molecule was engineered to resist degradation by dipeptidyl peptidase-4 and to bind serum albumin, extending its half-life from minutes to roughly one week. Approval for chronic weight management followed in 2021, based on large cardiovascular and obesity outcome trials.
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.
Quality control relies on pharmacopoeial monographs where they exist, combined with in-house specifications for identity, purity, water content, and counter-ion composition. Reference standards allow calibration across laboratories, although certified materials for every analogue are not universally obtainable. Batch records, chromatograms, and mass spectra form the documentation trail. Regulatory classification varies by jurisdiction and intended use, and research-grade material differs from pharmaceutical-grade material in testing scope. Analytical uncertainty is often expressed as relative standard deviation across replicate injections.
Lyophilised semaglutide is generally held at -20 °C or below, protected from light and moisture. Reconstituted solutions are typically kept at 2-8 °C and used within a defined window because degradation accumulates over time. Repeated freeze-thaw cycles are discouraged, since each cycle can promote aggregation and reduce monomeric content. Room-temperature stability of the solid has been examined in some studies but remains incompletely characterised for long durations, so cold storage is the conservative default for research material.
Vaginal estradiol is available in the forms of tablets, creams, inserts or suppositories, and rings. Vaginal estradiol tablets, creams, and inserts are usually administered once daily to twice weekly, whereas vaginal estradiol rings have a sustained action and are replaced once every 90 days. Vaginal estradiol can be used both as a systemic form of estradiol therapy, and at very low doses to selectively achieve a local vaginal effect without systemic effects, for instance in the treatment of menopausal symptoms such as vaginal atrophy and dryness. Vaginal estradiol is rapidly and almost completely absorbed. The absorption of vaginal estradiol is slightly greater in women with vaginal atrophy. Vaginal estradiol has high bioavailability and greatly increased potency compared to oral estradiol, with about 10- to 20-fold the comparative potency of oral estradiol. The greater potency of vaginal estradiol relative to oral estradiol is due to the lack of the first pass associated with oral estradiol and due to low local metabolism of estradiol in the vagina. Because of the high estradiol levels achieved, LH and FSH are more strongly suppressed with vaginal estradiol than with other routes. A daily dosage of 0.5 mg vaginal micronized estradiol has been found to result in estradiol and estrone levels of 250 pg/mL and 130 pg/mL, respectively. Vaginal estradiol has a much higher estradiol-to-estrone ratio in comparison to oral estradiol. The average ratio of estradiol to estrone with vaginal estradiol is 5:1, compared to 1:5 in the case of oral estradiol, a 10-fold difference.
Dayhoff was born an only child in Philadelphia, but moved to New York City when she was ten. Her academic promise was evident from the outset – she was valedictorian (class of 1942) at Bayside High School, Bayside, New York, and from there received a scholarship to Washington Square College of New York University, graduating magna cum laude in mathematics in 1945 and getting elected to Phi Beta Kappa.
After the internationalization of the war, several among them stepped off the fence and entered the political contest. The French strategy of inducing the Viet Minh to attack well-defended bases in remote areas at the end of their logistical trails succeeded at the Battle of Nà Sản. French efforts were hampered by the limited usefulness of tanks in forest terrain, the lack of a strong air force, and reliance on soldiers from French colonies. The Viet Minh used novel and efficient tactics, including direct artillery fire, convoy ambushes, and anti-aircraft weaponry to impede land and air resupplies, while recruiting a sizable regular army facilitated by large popular support. They used guerrilla warfare doctrine and instruction from China, and used war materiel provided by the Soviet Union. This combination proved fatal for the French bases, culminating in a decisive French defeat at the Battle of Dien Bien Phu. An estimated 400,000 to 842,707 soldiers died during the war as well as between 125,000 and 400,000 civilians. Both sides committed war crimes, including killings of civilians (such as the Mỹ Trạch massacre by French troops), rape and torture. The State of Vietnam gained full independence legally in June 1954, although the transfer of power was not yet complete. Despite gaining a great military advantage and controlling most of the country's territory, the Viet Minh had to accept a separation at the 17th parallel due to diplomatic pressure from the Chinese.
==== Asbestos fibers ==== Many common building materials (especially those manufactured in the United States before 1976) contain asbestos, such as some floor tiles, ceiling tiles, shingles, fireproofing, heating systems, pipe wrap, taping muds, mastics, and other insulation materials. Normally, significant releases of asbestos fiber do not occur unless the building materials are disturbed, such as by cutting, sanding, drilling, or building remodeling. Removal of asbestos-containing materials is not always optimal because the fibers can be spread into the air during the removal process. A management program for intact asbestos-containing materials is often recommended instead. When asbestos-containing material is damaged or disintegrates, microscopic fibers are dispersed into the air. Inhalation of asbestos fibers over long exposure times is associated with increased incidence of lung cancer, mesothelioma, and asbestosis. The risk of lung cancer from inhaling asbestos fibers is significantly greater for smokers. The symptoms of disease do not usually appear until about 20 to 30 years after the first exposure to asbestos. Although all asbestos is hazardous, products that are friable, e.g. sprayed coatings and insulation, pose a significantly higher hazard as they are more likely to release fibers to the air.
Following weeks of discussions, and in the absence of a compensation plan, a group of 15 lawyers filed a class-action lawsuit on behalf of 100 families against Sanlu, seeking medical and other expenses as well as compensation for trauma and for death of an offspring.
Sources: en.wikipedia.org
A steroid is an organic compound with four fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and as signaling molecules. Examples include the lipid cholesterol, sex hormones estradiol and testosterone, anabolic steroids, and the anti-inflammatory corticosteroid drug dexamethasone. Hundreds of steroids are found in fungi, plants, and animals. All steroids are manufactured in cells from sterol precursors: cholesterol and lanosterol (in opisthokonts), or cycloartenol (in plants). All three of these molecules are produced via cyclization of the triterpene squalene.
==== Energy- and fragment-based methods ==== Ab initio- or de novo- protein modelling methods seek to build three-dimensional protein models "from scratch", i.e., based on physical principles rather than (directly) on previously solved structures. There are many possible procedures that either attempt to mimic protein folding or apply some stochastic method to search possible solutions (i.e., global optimization of a suitable energy function). These procedures tend to require vast computational resources, and have thus only been carried out for tiny proteins. To predict protein structure de novo for larger proteins will require better algorithms and larger computational resources like those afforded by either powerful supercomputers (such as Blue Gene or MDGRAPE-3) or distributed computing (such as Folding@home, the Human Proteome Folding Project and Rosetta@Home). Although these computational barriers are vast, the potential benefits of structural genomics (by predicted or experimental methods) make ab initio structure prediction an active research field. As of 2009, a 50-residue protein could be simulated atom-by-atom on a supercomputer for 1 millisecond. As of 2012, comparable stable-state sampling could be done on a standard desktop with a new graphics card and more sophisticated algorithms. A much larger simulation timescales can be achieved using coarse-grained modeling.
=== Boers retreat === The set-piece period of the war now largely gave way to a guerrilla war, but one final operation remained. President Kruger and what remained of the Transvaal government had retreated to eastern Transvaal. Roberts, joined by troops from Natal under Buller, advanced against them, and broke their last defensive position at Bergendal on 26 August. As Roberts and Buller followed up along the railway line to Komatipoort, Kruger sought asylum in Portuguese East Africa (modern Mozambique). Some dispirited Boers did likewise, and the British gathered up much war material. However, the core of the Boer fighters under Botha easily broke back through the Drakensberg Mountains into the Transvaal highveld after riding north through the bushveld. As Roberts's army occupied Pretoria, the Boer fighters in the Orange Free State retreated into the Brandwater Basin, a fertile area in the south-east of the Republic. This offered only temporary sanctuary, as the mountain passes leading to it could be occupied by the British, trapping the Boers. A force under General Archibald Hunter set out from Bloemfontein to achieve this in July 1900. The hard core of the Free State Boers under De Wet, accompanied by President Steyn, left the basin early. Those remaining fell into confusion and most failed to break out before Hunter trapped them.
Alkylglycerone phosphate synthase (EC 2.5.1.26, alkyldihydroxyacetonephosphate synthase, alkyldihydroxyacetone phosphate synthetase, alkyl DHAP synthetase, alkyl-DHAP, dihydroxyacetone-phosphate acyltransferase, DHAP-AT) is an enzyme associated with Type 3 Rhizomelic chondrodysplasia punctata. This enzyme catalyses the following chemical reaction
Sources: en.wikipedia.org
==== Civil Protection ==== The Civil Protection is the Combine's primary law enforcement agency on Earth, whose ranks are drawn from unmodified, volunteering humans. Commonly referred to as "metrocops" or "CPs", Civil Protection personnel wear light body armor and face masks which resemble a modified PMK gas mask. They also have voice modifiers, masking their normal voices. They typically carry electroshock batons (named stun-sticks in the game) and pistols, and are occasionally equipped with submachine guns. The Civil Protection are frequently brutal in their methods, keeping the local populace in line via intimidation and violence. Interrogations, inspections, raids, random beatings, summary executions and acts of police brutality are all used as a means of policing their jurisdictions; the Civil Protection's methods are justified by their role as "protectors of the civilians' well-being". On the outskirts of City 17, the Civil Protection carry out constant patrols for escapees from the city. Civil Protection personnel are in constant contact with the Combine's Overwatch headquarters, which issues them objectives and situation updates. Upon the death of Civil Protection personnel, their armor detects that its wearer is no longer alive and automatically informs the Overwatch of the fatality.
In such low-temperature environments, there is potential for preserving the original hydrogen isotope signal over hundreds of millions of years. However, many rocks in geologic time have reached significant thermal maturity. Even by the onset of the oil window it appears that much of the hydrogen has exchanged. Recently, scientists have explored a silver lining: hydrogen exchange is a zero order kinetic reaction (for carbon bound hydrogen at 80–100°C, the half-times are likely 104–105 years). Applying the mathematics of rate constants would allow extrapolation to original isotopic compositions. While this solution holds promise, there is too much disagreement in the literature for robust calibrations.
=== BLOSUM === BLOSUM80: more related proteins BLOSUM62: midrange BLOSUM45: distantly related proteins The BLOSUM62 matrix with the amino acids in the table grouped according to the chemistry of the side chain, as in (a). Each value in the matrix is calculated by dividing the frequency of occurrence of the amino acid pair in the BLOCKS database, clustered at the 62% level, divided by the probability that the same two amino acids might align by chance. The ratio is then converted to a logarithm and expressed as a log odds score, as for PAM. BLOSUM matrices are usually scaled in half-bit units. A score of zero indicates that the frequency with which a given two amino acids were found aligned in the database was as expected by chance, while a positive score indicates that the alignment was found more often than by chance, and negative score indicates that the alignment was found less often than by chance.
== History == The earliest recorded use of the internal standard method dates back to Gouy's flame spectroscopy work in 1877, where he used an internal standard to determine if the excitation in his flame was consistent. His experimental procedure was later reintroduced in the 1940s, when recording flame photometers became readily available. The use of internal standards continued to grow, being applied to a wide range of analytical techniques including nuclear magnetic resonance (NMR) spectroscopy, chromatography, and inductively coupled plasma spectroscopy.
== History == At the initiative of Sudameris, a French-Italian bank that served markets in South America, which had accumulated a large coffee surplus in its warehouses, Nestlé began developing a new instant coffee product in 1932 to use the surplus of beans. The large supply of surplus came from the lowered coffee prices in Brazil which resulted from the Wall Street Crash of 1929. Max Morgenthaler led the development project of the instant coffee product, which initially used spray drying to create the product from liquid coffee. Nestlé introduced the new product under the brand name "Nescafé" on April 1, 1938. It became an American staple during World War II.
Sources: en.wikipedia.org
It is a synthetic analog of GLP-1 produced through medicinal chemistry to resist enzymatic degradation. The design goal was longer circulation than the native hormone.
A fatty acid side chain attaches the peptide to serum albumin, which shields it from kidney filtration and protease activity. This interaction is the main reason its circulation time is extended.
No. The native hormone is GLP-1, and semaglutide is an engineered variant with three deliberate structural alterations. It does not appear in unmodified biological sources.
Lower temperatures slow hydrolysis, oxidation and aggregation reactions that degrade the molecule over time. Lyophilised powder is more tolerant than solution, but both benefit from controlled conditions.