The short version of Aib substitution fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-07-18. Anything still debated is marked as such rather than presented as settled.
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.
Receptor binding triggers G protein signaling that raises intracellular cyclic AMP in pancreatic beta cells. Insulin release follows in a glucose-dependent manner, so secretion increases when blood glucose is elevated and diminishes when it is not. The same signaling suppresses glucagon release from alpha cells and slows gastric emptying, which blunts the post-meal glucose rise. In the brain, receptor activation in regions such as the arcuate nucleus is associated with reduced appetite and lower energy intake. How much each of these effects contributes to overall weight change is not fully settled.
Two structural features account for the prolonged half-life of semaglutide. A modified amino acid at position 8 resists cleavage by dipeptidyl peptidase-4, the enzyme that rapidly degrades native GLP-1. A fatty diacid side chain binds serum albumin, which limits renal clearance and protects the peptide from enzymatic breakdown. These modifications yield a plasma half-life of approximately one week in humans, allowing once-weekly administration. The relationship between plasma concentration and clinical effect varies between individuals, and sources of that variability are still being characterized.
Semaglutide is a synthetic peptide analog of glucagon-like peptide-1 (GLP-1), a hormone released from intestinal L-cells after food intake. The compound belongs to the incretin mimetic class and acts at GLP-1 receptors distributed across pancreatic, gastrointestinal, cardiovascular, and central nervous system tissues. Compared with native GLP-1, the molecule carries structural changes that extend its activity from minutes to roughly one week. It is studied for glycemic control in type 2 diabetes and for weight management, and its effects on cardiovascular and other outcomes remain active research areas.
| 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 |
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 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.
Handling guidance for research quantities calls for single-use aliquots, an inert atmosphere where practical, and avoidance of repeated freeze-thaw cycles that accelerate aggregation. Certificates of analysis typically report purity by peak area, water content, counter-ion identity, and residual solvent levels. In the scientific literature the compound is usually described by its full amino acid sequence, its registry number, or its structural class rather than by any proprietary label. Reporting standards vary between journals, and reviewers increasingly request raw chromatograms alongside tabulated purity figures. Whether current purity thresholds are adequate for every experimental context is debated.
Reversed-phase high-performance liquid chromatography with ultraviolet detection is the dominant approach for peptide purity assessment, usually paired with mass spectrometry to confirm molecular mass and sequence. Peptide mapping by enzymatic digestion and tandem mass spectrometry locates modifications such as deamidation and oxidation. Quantitation in plasma matrices can be performed by LC-MS/MS after solid-phase extraction. Method validation follows general guidance on accuracy, precision, linearity, and limits of detection. Comparability of results between laboratories, when no shared reference standard is available, remains an open question.
Stability studies focus on deamidation of asparagine and glutamine residues, oxidation of methionine, and aggregation into higher-order species. The fatty acid side chain adds susceptibility to oxidative change and can promote self-association at high concentration. Lyophilised material is comparatively robust when kept cold and dry, while aqueous solutions require refrigeration and protection from light. Forced degradation experiments under heat, acid, base, and peroxide conditions establish the specificity of each analytical method. Which degradation route dominates under real storage conditions depends on the formulation and stays formulation-specific.
=== Hemolytic transfusion reaction === There are many different varieties of abnormal reactions to blood transfusion. Among these, a potentially life-threatening reaction is known as a hemolytic transfusion reaction. This is an immune mediated reaction where recipient antibodies attack donor red blood cell antigen(s), causing hemolysis of donor cells. The reaction may occur during, immediately after, or up to 28 days later. An acute reaction is observed within the first 24 hours, whereas a delayed reaction will be observed between 24 hours and 28 days after transfusion.
== Symptoms of poisoning == α-Amanitin has an unusually strong and specific attraction to the enzyme RNA polymerase II. Upon ingestion and uptake by liver cells, it binds to the RNA polymerase II enzyme, effectively causing cytolysis of hepatocytes (liver cells). Few effects are reported within 10 hours; it is not unusual for significant effects to take as long as 24 hours after ingestion to appear, with this delay in symptoms making α-amanitin poisoning even more difficult to diagnose and all the more dangerous. By then, it is far past the time in which stomach pumping would yield an efficient result. Diarrhea and cramps are the first symptoms, but those pass, giving a false sign of remission. Typically, on the 4th to 5th day, the toxin starts to have severe effects on the liver and kidneys, leading to total system failure in both. Death usually takes place around a week from ingestion. Around 15% of those poisoned will die within 10 days, progressing through a comatose stage to kidney failure, liver failure, hepatic coma, respiratory failure and death. Those who recover are at risk of permanent liver damage. Diagnosis is difficult, and is established by observation of the clinical symptoms as well as the presence of α-amanitin in the urine. Urine screening is generally most useful within 48 hours of ingestion.
==== Cultivation in the UK ==== In late 2006, the British government permitted the pharmaceutical company MacFarlan Smith (a Johnson Matthey company) to cultivate opium poppies in England for medicinal reasons, after Macfarlan Smith's primary source, India, decided to increase the price of export opium latex. This move is well received by British farmers, with a major opium poppy field located in Didcot, England. The British government has contradicted the Home Office's suggestion that opium cultivation can be legalized in Afghanistan for exports to the United Kingdom, helping lower poverty and internal fighting while helping the NHS to meet the high demand for morphine and heroin. Opium poppy cultivation in the United Kingdom does not need a licence, but a licence is required for those wishing to extract opium for medicinal products.
== Approval history == The US FDA New Drug Application (NDA) was granted approval in May 2012, for use in adults. The US FDA Supplemental New Drug Application (sNDA) for pediatric use was granted approved in August 2014. In Israel, the Israeli Ministry of Health granted approval in September 2012. In Brazil, the Brazilian Health Surveillance Agency (ANVISA) granted approval in March 2013. In Canada, Health Canada issued a Notice of Compliance in May 2014, for both adults and pediatric patients. Taliglucerase alfa is made by the Israeli biotherapeutics company Protalix and sold by the American pharmaceutical company Pfizer.
Sources: en.wikipedia.org
There are some 5,000 potato varieties worldwide, 3,000 of them in the Andes alone — mainly in Peru, Bolivia, Ecuador, Chile, and Colombia. Over 100 cultivars might be found in a single valley, and a dozen or more might be maintained by a single agricultural household. The European Cultivated Potato Database is an online collaborative database of potato variety descriptions updated and maintained by the Scottish Agricultural Science Agency within the framework of the European Cooperative Programme for Crop Genetic Resources Networks—which is run by the International Plant Genetic Resources Institute. Around 80 varieties are commercially available in the UK. For culinary purposes, varieties are often differentiated by their waxiness: floury or mealy baking potatoes have more starch (20–22%) than waxy boiling potatoes (16–18%). The distinction may also arise from variation in the comparative ratio of two different potato starch compounds: amylose and amylopectin. Amylose, a long-chain molecule, diffuses from the starch granule when cooked in water, and lends itself to dishes where the potato is mashed. Varieties that contain a slightly higher amylopectin content, which is a highly branched molecule, help the potato retain its shape after being boiled in water. Potatoes that are good for making potato chips or potato crisps are sometimes called "chipping potatoes", which means they meet the basic requirements of similar varietal characteristics, being firm, fairly clean, and fairly well-shaped.
The stores, which made less than half the average company per-store sales, were concentrated heavily in the areas around Providence, Rhode Island, and Hartford, Connecticut, the former of which also has a concentration of stores from the locally competing Honey Dew Donuts chain, with some 150 outlets in Rhode Island and Southeastern Massachusetts. In the announcement, the chain stated that it will concentrate its efforts on its core markets such as western Canada. In the same statement, the company announced the sale of its portion of distribution company Maidstone Bakeries to Tim Hortons' European partners. It will use the CA$400 million generated by the sale for a stock buyback.
==== Industrial applications ==== Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using water to dissolve and extract substances, or to wash products or process equipment. Processes such as mining, chemical pulping, pulp bleaching, paper manufacturing, textile production, dyeing, printing, and cooling of power plants use large amounts of water, requiring a dedicated water source, and often cause significant water pollution. Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the motion of water. Typically a dam is constructed on a river, creating an artificial lake behind it. Water flowing out of the lake is forced through turbines that turn generators.
== Biological function == Flavin reductases exist in a variety of organisms, including animals and bacteria. In luminous organisms, flavin reductase is important in the luciferase process. In an experiment with P. fischeri and B. harveyi cells, bioluminescence was increased as the in vivo concentration of flavin reductase was increased. This suggests a connection between either a flavin reductase-luciferase complex or reduced flavin and the luminescence process in bacteria. The bacteria oxidize the reduced flavin mononucleotide to oxidized FMN and transfer it through free fusion to generate light. In humans, flavin reductase often catalyzes an NADPH dependent reduction of flavin mononucleotide which occurs in methemoglobin in erythrocytes and the liver. It has also been suggested that flavin reductases play a role in the production of hydrogen peroxide. This would be biologically helpful as H2O2 assists the body in maintaining homeostatic microbiota. A study showed that women with lactobacillus that produced hydrogen peroxide were less likely to develop bacterial vaginosis prebirth. It was also seen in Trichomonas vaginalis that decreased levels of flavin reductase increased the cycling of metronidazole because flavin reductase has an antioxidative effect, which decreases oxygen levels, maintaining the metronidazole population.
zygonema Also zygotene stage. In meiosis, the second of five substages of prophase I, following leptonema and preceding pachynema. During zygonema, synapsis occurs, physically binding homologous chromosomes to each other, and the cell's centrosome divides into two daughter centrosomes, each containing a single centriole.
Sources: en.wikipedia.org
Official website Alexander Zverev at the Association of Tennis Professionals Alexander Zverev at World Tennis Alexander Zverev at the Davis Cup (archived former page) Alexander Zverev at Olympics.com Alexander Zverev at Team Deutschland (in German) Alexander Zverev on Instagram
=== Disorders of amino-acid transport and metabolism === 270 Disorders of amino-acid transport and metabolism 270.0 Disturbances of amino-acid transport Cystinosis Cystinuria Hartnup disease 270.1 Phenylketonuria (PKU) 270.1 Tetrahydrobiopterin deficiency 270.2 Other disturbances of aromatic amino-acid metabolism Albinism Alkaptonuria Hypertyrosinemia Ochronosis Waardenburg syndrome 270.3 Disturbances of branched-chain amino-acid metabolism Isobutyryl-coenzyme A dehydrogenase deficiency Isovaleric acidemia Maple syrup urine disease Methylmalonic acidemia Propionic acidemia 270.4 Disturbances of sulphur-bearing amino-acid metabolism Homocystinuria 270.5 Disorders of histidine metabolism Carnosinemia Histidinemia Hyperhistidinemia Imidazole aminoaciduria Urocanic aciduria 270.6 Disorders of urea cycle metabolism Citrullinemia Hyperammonemia 270.7 Disorders of straight-chain amino-acid metabolism Hyperlysinemia Pipecolic acidemia Saccharopinuria 270.8 Other specified disorders of amino-acid metabolism Trimethylaminuria
=== Phlebitis === Phlebitis is the inflammation of a vein. It is usually accompanied by a blood clot when it is known as thrombophlebitis. When the affected vein is a superficial vein in the leg, it is known as superficial thrombophlebitis, and unlike deep vein thrombosis there is little risk of the clot breaking off as an embolus.
This is a methylation reaction in which glycocyamine is converted to creatine. The methyl group comes from the cofactor, S-adenosyl methionine (SAM), which loses its methyl group and becomes S-adenosyl-L-homocysteine (SAH). This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:N-guanidinoacetate methyltransferase. Other names in common use include GA methylpherase, guanidinoacetate methyltransferase, guanidinoacetate transmethylase, methionine-guanidinoacetic transmethylase, and guanidoacetate methyltransferase. It participates in the metabolism of amino acids. Defects in the gene which encodes this protein have been implicated in neurologic syndromes and muscular hypotonia, probably due to creatine deficiency and accumulation of guanidinoacetate in the brain of affected individuals. Two transcript variants encoding different isoforms have been described for this gene.
are the concentrations of aroma compounds in the interface and emulsion, respectively. With respect to stripping, Agc has the greatest effect on the mass transfer rate. Maximizing the surface area for mass transfer is done by using the smallest bubbles possible when stripping. Assuming spherical structure of the bubbles, the surface area is given by
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.
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and cleared quickly. Semaglutide carries a position 8 substitution that blocks that cleavage and a fatty diacid chain that binds albumin. Together these changes extend its circulating half-life to about one week.