The short version of Aib substitution fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-08-09 and is reviewed periodically as new material appears.
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.
肽类的主要降解路径包括天冬酰胺脱酰胺、甲硫氨酸氧化、天冬氨酸异构化以及由 β-折叠驱动的聚集，这些反应对 pH 与缓冲液种类较为敏感。磷酸盐、丙二醇与苯酚等辅料会影响局部微环境与界面行为。强制降解研究借助高温、强光、氧化剂与极端 pH 暴露来预测产物谱。关于长期室温存放的数据相对有限，超出标签条件的稳定性仍属开放问题，需要在具体制剂中通过实时与加速试验加以确认。
容器与密封系统同样参与稳定性表现。硅油涂层、胶塞材质与顶空氧含量可能改变聚集速率与氧化水平。分析结果因此需要在完整包装形式下评估，而不能仅凭原料药数据推断。法规文件通常要求同时提交批次数据与代表性容器中的稳定性趋势。
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C187H291N45O59 | free base, without counter-ion |
| Molecular weight | About 4114 Da | peptide backbone plus attached lipid chain |
| Plasma half-life | About 165 hours | supports once-weekly dosing in humans |
| Plasma protein binding | Greater than 99 percent | attributed mainly to serum albumin |
| Receptor target | GLP-1 receptor | Gs-coupled, raises intracellular cyclic AMP |
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 or 280 nanometres is widely used to assess purity and to resolve related impurities. Liquid chromatography coupled to mass spectrometry confirms identity through the protonated molecular ion and fragment ions formed in tandem experiments. Capillary electrophoresis and peptide mapping after enzymatic digestion supply complementary information on charge variants and modification sites. Circular dichroism and nuclear magnetic resonance can report on secondary structure in solution. Absolute quantification usually depends on an external standard, and reported purity depends on the detection wavelength and integration parameters chosen.
Lyophilised material appears as a white to off-white cake or powder that is hygroscopic, and containers are usually equilibrated to room temperature before opening to limit condensation. Dissolution is performed in water, phosphate-buffered saline, or a mildly alkaline buffer, since solubility rises above neutral pH. Gentle inversion or low-speed mixing is preferred, because vigorous vortexing can promote surface denaturation and aggregation. Complete dissolution may require several minutes, and brief sonication is sometimes applied. Passing the solution through a 0.22 micrometre membrane removes particulates but does not by itself sterilise the liquid.
Storage at minus 20 degrees Celsius or lower in a desiccated container preserves the peptide for extended periods, while working solutions are commonly held at two to eight degrees Celsius for short intervals. Light exposure and repeated freeze-thaw cycles accelerate degradation, so dividing material into single-use aliquots is generally recommended. Adsorption to glass and plastic surfaces can lower the measured concentration of dilute solutions, particularly below one milligram per millilitre. The degradation routes most often reported for GLP-1 analogues are deamidation, methionine oxidation, and backbone hydrolysis. Relative rates under specific conditions are frequently described only for individual formulations.
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.
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.
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.
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.
Diverse perspectives on well-being are found in religious and other traditional belief systems, where well-being often serves as a goal of spiritual practice. In various traditional forms of Hinduism, the highest kind of well-being is not determined by objective external conditions. Instead, it depends primarily on experiential knowledge of the self, brought about through practices like self-inquiry and meditation. Buddhism identifies suffering as a central aspect of all existence. It aims to produce well-being by eliminating the causes of suffering, such as desire and ignorance, achieved through the practice of Buddhist virtues, like compassion, loving-kindness, and equanimity. From the perspective of Confucianism, well-being consists in virtuous activity as a process leading to sagehood and is associated with harmonious relationships and social responsibility. According to Taoism, a life high in well-being is characterized by effortless action that is in harmony with the Tao—the natural way of the universe—and guided by spontaneous dispositions. The Christian tradition holds that the personal connection to God is a central factor of well-being, which may manifest in virtuous activity or contemplation of God. According to the teachings of Islam, well-being is achieved by dedicating one's life as much as possible to worshiping Allah and fulfilling His will, as expressed in the Quran. Well-being is also a topic in various biological sciences with a focus on physiological factors. Research from twin studies suggests that genetic composition is an impactful determinant.
However, recent medical literature has proposed reclassifying insulin specifically as a reponic hormone (from the Latin repono, meaning "to store") to better distinguish its metabolic role from that of classic anabolic hormones like testosterone or growth hormone. While classic anabolic hormones drive energy-intensive processes to build metabolically active lean tissue, the primary physiological function of a reponic hormone is to conserve and store systemic energy. Insulin achieves this by driving the cellular uptake of glucose and lipids for storage (lipogenesis and glycogenesis) while simultaneously inhibiting the breakdown of stored energy (lipolysis and glycogenolysis). Researchers argue this distinction provides a clearer framework for understanding why hyperinsulinemia is uniquely characterized by central adiposity and metabolic syndrome rather than lean tissue growth.
=== Global activism === He was one of the signatories of the agreement to convene a convention for drafting a world constitution. As a result, for the first time in human history, a World Constituent Assembly convened to draft and adopt a Constitution for the Federation of Earth.
=== Bibliography === Aerei da combattimento della Seconda Guerra Mondiale (in Italian). Novara, Italy: De Agostini Editore, 2005. Anderson, Peter N. Mustangs of the RAAF and RNZAF. Sydney, Australia: A.H. & A.W. Reed Pty Ltd, 1975. ISBN 0-589-07130-0. Angelucci, Enzo and Peter Bowers. The American Fighter: The Definitive Guide to American Fighter Aircraft from 1917 to the Present. New York: Orion Books, 1985. ISBN 0-517-56588-9. Aro, Chuck and Colin Aro. "World's Fastest Mustangs". Air Enthusiast. No. 13, August–November 1980. pp. 56–62. ISSN 0143-5450 Birch, David. Rolls-Royce and the Mustang. Derby, UK: Rolls-Royce Heritage Trust, 1987. ISBN 0-9511710-0-3. Bowen, Ezra. Knights of the Air (Epic of Flight). New York: Time-Life Books, 1980. ISBN 0-8094-3252-8. Borth, Christy. Masters of Mass Production. Indianapolis, Indiana: Bobbs-Merrill Co., 1945. Bowman, Martin W. P-51 Mustang vs Fw 190: Europe 1943–45. Oxford, UK: Osprey Publishing, 2007. ISBN 1-84603-189-3. Boylan, Bernard. Development of the Long Range Escort Fighter. Washington, D.C.: USAF Historical Division, Research Studies Institute, Air University, 1955. Retrieved: 15 July 2014. Boyne, Walter J. Clash of Wings. New York: Simon & Schuster, 1994. ISBN 0-684-83915-6. Breffort, Dominique with André Jouineau. Le North-American P-51 Mustang – de 1940 à 1980 (Avions et Pilotes 5)(in French). Paris: Histoire et Collections, 2003. ISBN 2-913903-80-0. Bridgman, Leonard, ed. "The North American Mustang." Jane's Fighting Aircraft of World War II. London: Studio, 1946. ISBN 1-85170-493-0.
== Phase 2 == The second phase of the Protein Structure Initiative (PSI-2) lasted from July 2005 to June 2010. Its goal was to use methods introduced in PSI-1 to determine a large number of proteins and continue development in streamlining the structural genomics pipeline. PSI-2 had a five-year budget of $325 million provided by NIGMS with support from the National Center for Research Resources. By the end of this phase, the Protein Structure Initiative had solved over 4,800 protein structures; over 4,100 of these were unique.
Sources: en.wikipedia.org
These are generally substituted anthraquinones; many have medicinal applications, being used as purgatives, while one, ruberythric acid, yields the valuable dyestuff madder, the base of which is alizarin. Chrysophanic acid, a dioxymethylanthraquinone, occurs in rhubarb, which also contains emodin, a trioxymethylanthraquinone; this substance occurs in combination with rhamnose in Frangula bark. A recent study suggests, that purified anthraquinone glycosides from rhubarb could be a potential therapeutic avenue to treat type 2 diabetes mellitus by modulating the gut microbiota and reducing systematic inflammation. Arguably the most important cyanogenic glucoside is amygdalin, which occurs in bitter almonds. The enzyme maltase decomposes it into glucose and mandelic nitrile glucoside; the latter is broken down by emulsin into glucose, benzaldehyde and prussic acid. Emulsin also decomposes amygdalin directly into these compounds without the intermediate formation of mandelic nitrile glucoside. Several other glucosides of this nature have been isolated. The saponins are a group of substances characterized by forming a lather with water; they occur in soap-bark. Mention may also be made of indican, the glucoside of the indigo plant; this is hydrolysed by the indigo ferment, indimulsiri, to indoxyl and indiglucin.
=== Biden administration (2021–2025) === In March 2021, the National Security Commission on Artificial Intelligence released their final report. In the report, they stated, "Advances in AI, including the mastery of more general AI capabilities along one or more dimensions, will likely provide new capabilities and applications. Some of these advances could lead to inflection points or leaps in capabilities. Such advances may also introduce new concerns and risks and the need for new policies, recommendations, and technical advances to assure that systems are aligned with goals and values, including safety, robustness and trustworthiness." In June 2022, Senators Rob Portman and Gary Peters introduced the Global Catastrophic Risk Management Act. The bipartisan bill "would also help counter the risk of artificial intelligence... from being abused in ways that may pose a catastrophic risk". On October 4, 2022, President Joe Biden unveiled a new AI Bill of Rights, which outlines five protections Americans should have in the AI age: 1. Safe and Effective Systems, 2. Algorithmic Discrimination Protection, 3.Data Privacy, 4. Notice and Explanation, and 5. Human Alternatives, Consideration, and Fallback. The bill was formally published in October 2022 by the Office of Science and Technology Policy (OSTP), a U.S. government office that advises the President on science and technology policy matters.
The short length of pompilidotoxins implies that the crucial amino acid for receptor binding would be easier to detect in studies based on pompilidotoxins. Additionally, the binding of the α-scorpion or sea anemone toxin to the sodium receptor also includes a complex system of forming three to four additional disulfide bonds. Pompilidotoxins cannot form such bonds. Pompilidotoxins thus provide a special advantage to research, classify, and characterise different isoforms of sodium channels due to their concise and simple structure. They have already been used for neuronal research into the action mechanisms of sodium channels, and the characterisation of receptor functions. Knowing more about the working of sodium channels could greatly contribute to healthcare as sodium channel alterations are associated with a large range of neurological disorders. Persistent sodium currents are especially participating in some variants of epilepsy and MS. Moreover, β-PMTX itself has been associated with being an epilepsy-inducing agent due to its drastic working in increasing neuronal excitability and has been recognized as being especially important for providing insights into the role of sodium currents in epileptogenesis. Thus, even though pompilidotoxins are not used as drugs and therefore have no efficacious nor adverse effects, they are medically valuable as a research model to indirectly improve patient well-being.
== Excavation and preparation == Usually the first evidence of fossil dinosaur eggs to be discovered are shell fragments that have eroded away from the original eggs and been transported downhill by the elements. If the source eggs can be found the area must be examined for more unexposed eggs. If the paleontologists are fortunate enough to have found a nest, the number and arrangement of the eggs must be estimated. Excavation must proceed to significant depth since many dinosaur nests include multiple layers of eggs. As the underside of the nest is excavated, it would be covered by material like newspaper, tin foil, or tissue. Afterwards, the entire block is covered in multiple layers of plaster-soaked strips of burlap. When the plaster is dried, the block is undercut the rest of the way and turned over. The fine work of cleaning the egg fossils is performed in a laboratory. Preparation usually begins from the underside of the block, which tends to be the best preserved. Because of their fragility, cleaning fossil eggs requires patience and skill. Scientists use delicate instruments like dental picks, needles, small pneumatic engraving tools, and X-Acto knives. Scientists must determine at what point to stop cleaning based on their own criteria. If eggs are fully extracted they can be more fully studied individually at the cost of information regarding the spatial relationships between eggs or if the eggs had hatched.
==== Cytosolic ions ==== Early evidence was against the NAADP receptor being regulated by either cytosolic Ca2+ or pH. Since then, Ca2+ has been shown to stimulate human TPC1 on both its cytosolic and luminal faces.
Sources: en.wikipedia.org
== Applications == Ammonium sulfate precipitation is a useful technique as an initial step in protein purification because it enables quick, bulk precipitation of cellular proteins. It is also often employed during the later stages of purification to concentrate protein from dilute solution following procedures such as gel filtration. The drawback of this method is that oftentimes different substances can precipitate along with the protein, and other purification techniques must be performed, such as ion chromatography or size-exclusion chromatography.
Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is either gaseous (as interstellar clouds) or plasma (as stars).
Example of comparing and determining the % difference between two nucleotide sequences AATCCGCTAG AAACCCTTAG Given the two 10-nucleotide sequences, line them up and compare the differences between them. Calculate the percent difference by taking the number of differences between the DNA bases divided by the total number of nucleotides. In this case there are three differences in the 10 nucleotide sequence. Thus there is a 30% difference.
=== Tolerance === A very rapid and strong tolerance, known as tachyphylaxis, develops to the effects of psychedelics with repeated administration. It develops with a single dose and is present within hours to days. Already by the second day, with LSD, there was a 50% decrease in psychoactive effects in one study. Following a few days of repeated administration, or 3 to 4 days in the case of LSD, there is an almost complete absence of effects. The tolerance remains stable thereafter. In one study that gave LSD continuously for up to 84 days, doubling, tripling, and quadrupling the dose was unable to fully overcome the tolerance and restore effects. An abstinence period of 3 to 6 days is required for sensitivity to return and tolerance to fully reset. LSD, psilocybin, and mescaline all show cross-tolerance with each other. Tolerance has been shown to develop to numerous psychedelics in animals and/or humans. Tolerance with psychedelics develops to both their psychoactive effects and their physical effects, such as pupil dilation and tachycardia. As a result of the tolerance, recreational psychedelic users do not use the drugs daily but often show a once-per-week use pattern. Some possible exceptions among psychedelics which may not build tolerance or may develop it much less rapidly include dimethyltryptamine (DMT), ayahuasca (which contains DMT), and 5-MeO-DMT. Similarly, the structurally related dipropyltryptamine (DPT) and diisopropyltryptamine (DiPT) did not show behavioral tolerance in rodents, in contrast to DOI and 2C-T-7.
Watson then made a successful return to football with a dominant game against Hawthorn in a 25-point win. On 9 August 2017, with three rounds left in the home-and-away season, Watson announced that he would retire at the end of the season. Watson then played in three of Essendon's last four matches, with his final game coming in the 65-point elimination final loss to Sydney at the Sydney Cricket Ground. Watson played 20 games in his final season, which is the most he had played in a season since 2012, to finish on 220 games for Essendon.
Sources: en.wikipedia.org
Native GLP-1 is a short-lived peptide cleared within one to two minutes by dipeptidyl peptidase-4 and related enzymes. Semaglutide keeps the receptor-binding backbone but adds substitutions and a lipid chain. These changes block the main cleavage site and allow reversible albumin binding, extending the half-life to roughly 165 hours.
Albumin is the most abundant protein in plasma and carries molecules that bear fatty-acid chains. Binding shields the peptide from renal filtration and from peptidases, keeping a circulating reservoir. Slow release from this reservoir produces sustained receptor occupancy and supports infrequent dosing.
The insulinotropic effect is glucose-dependent, meaning secretion increases mainly when glucose is elevated. This property is often described as lowering the chance of hypoglycaemia when the compound is used alone. Other glucose-lowering agents used at the same time can still cause low blood glucose.
冻融过程中冰晶形成与局部浓度升高会促使肽链发生界面吸附和聚集。聚集不仅降低有效含量，还会改变可见异物与不溶性微粒的计数结果。将溶液分装为单次使用的小体积等份可减少循环次数。