This is a working overview of deamidation, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-06 and is reviewed periodically as new material appears.
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.
The compound binds the GLP-1 receptor on pancreatic beta cells and other tissues, activating a G-protein signaling cascade that raises intracellular cyclic AMP. This action increases glucose-dependent insulin secretion when blood glucose is elevated, while binding also slows gastric emptying and reduces glucagon release. In the central nervous system, receptor activation in the hypothalamus and brainstem contributes to reduced appetite. The fatty acid chain binds albumin, which protects the peptide from renal filtration and enzymatic degradation. This albumin binding is central to its extended circulation time.
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.
| Property | Value | Notes |
|---|---|---|
| Purity assessment | RP-HPLC, 214 nm | Wavelength affects relative peak areas |
| Identity confirmation | LC-MS/MS | Precursor and fragment ion masses compared |
| Common degradation | Deamidation, oxidation | Amide and methionine residues are main sites |
| Working solution storage | 2-8 °C, short term | Longer holding favours frozen aliquots |
| Adsorption risk | Higher below 1 mg/mL | Glass and plastic surfaces both affected |
该分子作为 GLP-1 受体的选择性激动剂发挥作用，受体属于 B 类 G 蛋白偶联受体家族，激活后经 Gs 通路提升细胞内环腺苷酸水平。在胰腺 β 细胞，信号促进葡萄糖依赖性的胰岛素释放，血糖偏低时该作用明显减弱。在胰岛 α 细胞，胰高血糖素分泌受到抑制。中枢神经系统与胃肠道同样存在受体表达，相应信号参与食欲调节以及胃排空速率的降低。
皮下注射后吸收相对缓慢，绝对生物利用度约为百分之八十九，血药浓度峰值通常出现在给药后一到三天。与白蛋白结合使清除减慢，终末半衰期约为一百六十五小时，接近一周。连续给药约四到五周后达到稳态暴露水平。表观分布容积约为每千克零点二五升，血浆蛋白结合率超过百分之九十九。代谢以蛋白水解切割和脂肪二酸侧链的 β-氧化为主，相关产物主要经尿液与粪便排出。
序列层面的改动同时解决了两个问题，即酶解稳定性与肾脏清除速度。天然 GLP-1 在循环中的半衰期仅约两分钟，主要被二肽基肽酶-4 迅速灭活。酰化侧链与白蛋白的可逆结合形成循环储库，使分子缓慢释放并持续激活受体。这种设计思路后来被广泛用于同类长效肽的开发，属于该类药物化学改造的典型范式。
Reversed-phase high-performance liquid chromatography is widely used to assess purity and to separate the parent peptide from related substances. Mass spectrometry confirms identity and can resolve modifications that differ by a few daltons. Size-exclusion chromatography detects dimers and higher aggregates, which are relevant to both stability and immunogenicity questions. Peptide mapping with enzymatic digestion locates specific modifications along the sequence. Circular dichroism provides a secondary-structure profile, although it gives limited information about local conformational changes.
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.
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.
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.
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.
elegans, as Argonaute proteins are upregulated in response to viruses and worms that overexpress components of the RNAi pathway are resistant to viral infection. The role of RNAi in mammalian innate immunity is poorly understood, and relatively little data is available. However, the existence of viruses that encode genes able to suppress the RNAi response in mammalian cells may be evidence in favour of an RNAi-dependent mammalian immune response, although this hypothesis has been challenged as poorly substantiated. Evidence for the existence of a functional antiviral RNAi pathway in mammalian cells has been presented. Other functions for RNAi in mammalian viruses also exist, such as miRNAs expressed by the herpes virus that may act as heterochromatin organization triggers to mediate viral latency.
=== Non-canonical phosphorylation on His, Asp, Cys, Glu, Arg and Lys in human cells === Widespread human protein phosphorylation occurs on multiple non-canonical amino acids, including motifs containing phosphorylated histidine (1 and 3 positions), aspartate, cysteine, glutamate, arginine, and lysine in HeLa cell extracts. Due to the chemical and thermal lability of these phosphorylated residues, special procedures and separation techniques are required for preservation alongside the heat stable 'classical' Ser, Thr and Tyr phosphorylation.
Doug Ford is the 26th and current premier of Ontario (French: Premier ministre de l'Ontario), Canada. He won a majority in the 2018 Ontario general election, as leader of the Ontario Conservative Party caucus in the Legislative Assembly of Ontario and was sworn in as premier on June 29, 2018. He was re-elected with an increased majority in 2022, and again after calling a snap election for February 27, 2025.
== Biography == Partha Mitra received his PhD in theoretical physics from Harvard University under the guidance of Bertrand Halperin in 1993. He was a member of the Theoretical Physics Department at Bell Laboratories from 1993 to 2003, and an assistant professor in Theoretical Physics at Caltech from 1996 before moving to Cold Spring Harbor Laboratory in 2003 where he is a Crick-Clay professor of biomathematics. Professor Mitra also holds adjunct positions in the NYU School of Medicine and Weill Cornell Medical College.
Sources: en.wikipedia.org
== Temperature monitoring == Temperature plays a crucial part in maintaining the potency of vaccines. Although the risk of storage cooler malfunction is low, it is better to check than the need to replace vaccines wasted due to the loss of potency. Temperature monitoring needs to take place in both storage units and transport units. The refrigerator should maintain a temperature between 2° and 8 °C (36° and 46 °F). Freezers should maintain a temperature between -50° and -15 °C (-58° and +5 °F). Thermometers are useful to monitor the temperature by placing at the storage unit's central location, adjacent to the vaccines. Every vaccine storage unit must have a temperature monitoring device. There are many different thermometers, including standard fluid-filled, min-max, and continuous temperature monitoring devices. Each type of thermometer has its advantages and disadvantage.
Within Contact and Special Circumstances, there are also inner circles that can take control in crises, somewhat contradictory to the ideal notions of democratic and open process the Culture espouses. Contact and Special Circumstances may suppress or delay the release of information, for example to avoid creating public pressure for actions they consider imprudent or to prevent other civilisations from exploiting certain situations. In dealing with less powerful regressive civilisations, the Culture usually intervenes discreetly, for example by protecting and discreetly supporting the more liberal elements, or subverting illiberal institutions. For instance, in Use of Weapons, the Culture operates within a less advanced illiberal society through control of a business cartel which is known for its humanitarian and social development investments, as well as generic good Samaritanism. In Excession, a sub-group of Minds conspires to provoke a war with the extremely sadistic Affront, although the conspiracy is foiled by a GSV that is a deep cover Special Circumstances agent. Only one story, Consider Phlebas, pits the Culture against a highly illiberal society of approximately equal power: the aggressive, theocratic Idirans. Though they posed no immediate, direct threat to the Culture, the Culture declared war because it would have felt useless if it allowed the Idirans' ruthless expansion to continue. The Culture's decision was a value-judgement rather than a utilitarian calculation, and the "Peace Faction" within the Culture seceded.
Unusually large bile duct obstruction, e.g., gallstone in common bile duct (which is the most common post-hepatic cause) Biliary stricture (benign or malignant) Cholangitis Severe liver failure with cirrhosis (e.g. primary biliary cirrhosis) Pancreatitis Cirrhosis may cause normal, moderately high or high levels of bilirubin, depending on exact features of the cirrhosis. To further elucidate the causes of jaundice or increased bilirubin, it is usually simpler to look at other liver function tests (especially the enzymes alanine transaminase, aspartate transaminase, gamma-glutamyl transpeptidase, alkaline phosphatase), blood film examination (hemolysis, etc.) or evidence of infective hepatitis (e.g., hepatitis A, B, C, delta, E, etc.).
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and Afghan National Army soldiers led by SSG Robert James Miller was conducting a combat reconnaissance patrol through the Gowardesh Valley, Kunar Province, when they engaged a force of 15–20 insurgents occupying prepared fighting positions. After calling in close air support, Staff Sergeant Miller led a small squad forward to conduct battle damage assessment when over 100 insurgents ambushed the squad, Miller displayed extraordinary valor by drawing fire away from his squad, killing 10 insurgents in the process. His actions cost him his life, but he saved the lives of 7 members of his team and 15 Afghan National Army soldiers, he was awarded the Medal of Honor. In September 2008, a Green Beret ODA conducted a joint operation with 1 Troop 3 Squadron SASR in northwest Uruzgan Province, the operation was designed to lure insurgents into a trap using a ground convoy of five special forces GMV trucks as bait. SASR sniper teams, who inserted on foot the night before as part of two cut-off groups to overwatch the patrol. The plan worked, a small group of insurgents approached the vehicles, intent on ambushing the convoy, they were engaged by the SASR snipers. Minutes later a Toyota Hilux appeared carrying a number of armed insurgents, they were engaged and killed and a second vehicle, a van, arrived carrying 3 insurgents were engaged by the sniper teams until they spotted a female non-combatant who was used as a human shield by the surviving insurgent, the insurgent was eventually killed with no harm to the woman, a total of 13 insurgents were killed.
==== NIH Toolbox ==== In September 2006, the NIH Blueprint for Neuroscience Research started a contract for the NIH Toolbox for the Assessment of Neurological and Behavioral Function to develop a set of state-of-the-art measurement tools to enhance collection of data in large cohort studies. More than 250 scientists from almost 100 academic institutions contributed to its development. In September 2012, the NIH Toolbox was rolled out to the research community. NIH Toolbox assessments are based, where possible, on Item Response Theory and adapted for testing by computer.
=== President and Past Presidents (since 1953) === 2022–2024 Julia Laskin 2020–2022 Susan Richardson 2016–2018 Vicki Wysocki 2014–2016 Jennifer Brodbelt 2012–2014 Susan Weintraub 2006–2008 Barbara S. Larsen 2002–2004 Catherine E. Costello 1996–1998 Veronica M. Bierbaum 1982–1984 Catherine Fenselau
== See also == Hermetic seal – Airtight seal James Webb Space Telescope sunshield – Main cooling system for the infrared observatory Tervis Tumbler – American drinkware manufacturer Thermal cooking – Cooking method Yeti Holdings – American manufacturing company Cooler – Insulated box used to keep food or drink cool
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Filtering removes particulate matter that can block columns or scatter light. A 0.22 micrometre membrane is typical, and the filter material should be checked for peptide adsorption.
Peptides can bind to glass and plastic, so a fraction of the material leaves the solution. The effect is proportionally larger in dilute samples and can bias quantitative results.
Reverse-phase high-performance liquid chromatography is the most widely reported approach. Purity figures should always be quoted together with the wavelength, gradient, and integration parameters used.
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.