If you have been reading about deamidation and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-03-30. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical purity assay | reversed-phase HPLC, 220 nm | Amide-bond detection for the peptide backbone |
| Identity confirmation | electrospray mass spectrometry | Peptide mapping used for sequence coverage |
| Related substances | deamidated and oxidised forms | Truncated sequences also monitored |
| Powder storage | -20 degrees Celsius | Keep sealed, dry, and protected from light |
| Solution storage | 2 to 8 degrees Celsius | Avoid repeated freeze-thaw cycling |
Receptor activation occurs at GLP-1 receptors distributed across pancreatic islets, the hypothalamus, and the gastrointestinal tract. Binding triggers G protein signaling that raises cyclic AMP and enhances glucose-dependent insulin release. Because the effect depends on prevailing glucose levels, insulin secretion does not rise when blood sugar is already low. Signaling in the brain and gut also influences appetite and gastric emptying, which is why the compound appears in both metabolic and weight-related research literature.
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.
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.
市售注射用制剂通常要求在二至八摄氏度冷藏保存，并避免光照与冻结。部分多剂量笔在首次使用后允许在不超过三十摄氏度的环境中存放有限周数，具体期限由辅料与防腐剂体系决定。反复冻融会促进肽链聚集并改变可见颗粒计数，因此应予避免。冻干粉末在干燥、避光、低温条件下更为稳定。溶液配制后宜使用低吸附容器，以减少肽类在塑料或玻璃表面的损失。
纯度评价多采用反相高效液相色谱，流动相常加入三氟乙酸或甲酸作为离子对改性剂，检测波长设在二百一十四纳米或二百二十纳米。分子量确认依靠电喷雾电离质谱或基质辅助激光解吸电离质谱，实测值应与理论值在数 ppm 内吻合。肽图分析通过酶切后液相色谱串联质谱完成，用于核查序列与修饰位点。体积排阻色谱用于定量共价与非共价聚集体。生物基质浓度测定则采用免疫分析或液相色谱串联质谱。
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。
=== Genotoxicity and mutagenicity === Mutation studies in prokaryotes and eukaryotes show that ractopamine is not mutagenic. However, the results of several in vitro studies, including chromosome aberration tests in human lymphocytes, are positive. The positive genotoxic results are explained with limited evidence to be due to a secondary auto-oxidative mechanism from ractopamine-catechol-producing reactive intermediates.
=== 17 May === The Security Service of Ukraine identified and charged six individuals with "illegally disseminating" information about Ukrainian air defences in Kyiv. These individuals took videos of Ukrainian air defences in action then posted them on social media sites such as YouTube. Such information, the SBU alleged, could be used to make Russian strikes more accurate. The penalty for such a charge was five to eight years imprisonment. Russia's defence ministry claimed its forces had destroyed a British-made L-119 howitzer in Ukraine according to a report by state news agency TASS. It also claimed to have struck an ammunition depot in Mykolaiv. The DSM Capella, the last ship to sail under the Black Sea Grain Initiative before its expected expiration on 18 May, left the Ukrainian port of Chornomorsk carrying 30,000 tonnes of corn bound for Turkey. Shortly afterwards, Turkish President Recep Tayyip Erdoğan said that the grain exportation deal between Ukraine and Russia had been extended for two more months. Both Russia and Ukraine welcomed the extension. A child and two others were reported to have been killed and three people were injured after a Russian shell struck outside a shop in Zelenivka, Kherson Oblast. In Donetsk, the city's Russian-backed mayor claimed Ukrainian shelling left five dead and 15 injured.
== Challenges and criticisms == Critics of translational medical research (to the exclusion of more basic research) point to examples of important drugs that arose from fortuitous discoveries in the course of basic research such as penicillin and benzodiazepines, and the importance of basic research in improving our understanding of basic biological facts (e.g. the function and structure of DNA) that go on to transform applied medical research. Examples of failed translational research in the pharmaceutical industry include the failure of anti-aβ therapeutics in Alzheimer's disease. Other problems have stemmed from the widespread irreproducibility thought to exist in translational research literature.
== Appetite and circadian rhythms == Dynorphins are important in maintaining homeostasis through appetite control and circadian rhythms. Przewlocki et al. found that, during the day, dynorphins are naturally elevated in the neurointermediate lobe of the pituitary (NI pituitary) and depressed in the hypothalamus. This pattern is reversed at night. In addition, mice deprived of food and water, or of water alone, had increased levels of dynorphin in the hypothalamus during the day. Deprivation of water alone also decreased the dynorphin levels in the NI pituitary. These findings led Przewlocki et al. to conclude that dynorphins are essential in maintaining homeostasis. Dynorphin has been implicated as an appetite stimulant. A number of studies in rats have shown that increasing the dynorphin levels stimulates eating. Opioid antagonists, such as naloxone, can reverse the effects of elevated dynorphin. This inhibition is especially strong in obese animals or animals that have access to particularly appealing food. Inui et al. found that administering dynorphin to dogs increased both their food and water intake. Dynorphin plays a role in the eating behavior of hibernating animals. Nizeilski et al. examined dynorphin levels in the ground squirrel, which undergoes periods of excessive eating and periods of starvation before winter. They found that dynorphin levels increased during the starvation periods. Berman et al. studied the levels of dynorphin during periods of food restriction.
In May 2016, the company opened a $150 million temperature-controlled warehouse in North Charleston, South Carolina, near the Port of Charleston, then acquired Consolidated Distribution Corporation of Lombard, Illinois that August, making Lineage the largest customized redistribution network in the United States. Two months later, it was reported that Lineage was considering locating a large facility at New Century AirCenter in Gardner, Kansas, but the proposed location resulted in lawsuits from local residents, and Lineage scrapped the project in November 2017 "due to a change in customer needs", though the project had received unanimous approval from county commissioners in July. Lineage entered European markets in 2017, acquiring Partner Logistics, a large cold-chain storage supplier. The company purchased facilities from American Cold Storage, in the Midwest, and eight Los Angeles, California area warehouses from U.S. Growers Cold Storage, raising its employee roster to 7,200, with Lineage operating 120 temperature-controlled storage facilities. The company then expanded into the temperature-controlled logistics markets in Australia, New Zealand, and Sri Lanka, in November 2019, with the acquisition of Emergent Cold, then into Canada, in July 2020, acquiring Ontario Refrigerated Services Inc. During 2018, the company acquired 24 companies, including The Yearsley Group, the UK's largest Cold Storage and Haulage supplier, maintaining its second-largest status. The company also sold minority stakes worth $700 million.
Sources: en.wikipedia.org
== The "no waste" culture == Sake kasu can be considered as a part of the "no waste" culture in Japan. Sake kasu is the waste produced by sake production, and the Japanese decided to use it because they do not want to waste any of the ingredients. A lot of sake kasu is produced during sake production and a lot of sake kasu is considered as industrial waste and being discarded. In order to reduce the waste produced by the sake kasu in Japan, it is recycled for use in other products. Some breweries sell their sake kasu directly to restaurants or put it into packages sold in convenient stores and supermarkets.
2007 The book Ending Aging written by Aubrey de Grey and his research assistant Michael Rae. 2007 First evidence that a pharmacological agent (namely, metformin) at a certain dosage is capable to increase the lifespan of mice. 2008 Foundation of the Max Planck Institute for Biology of Ageing. 2008 (approximately) It was observed that different variants of FOXO3 gene are associated with human longevity. Since then, research has been conducted to better understand its functions and the mechanism of action. 2009 Association of genetic variants in insulin/IGF1 signaling with human longevity. 2009 A second pharmacological agent (namely, rapamycin) was shown to be capable to increase the lifespan of mice. For this discovery Dave Sharp receive a special prize from the Methuselah Foundation. 2009 The SENS Research Foundation, a research institute dedicated to studying the aging process and ways to reverse it based on the strategies for engineered negligible senescence approach, was established by Aubrey de Grey. 2010s first half The appearance of small political parties in different countries that make the promotion of anti-aging technologies part of their political platforms (for example, Science Party of Australia, U.S. Transhumanist Party, Party for Rejuvenation Research). 2010 Harvard University scientists at the Dana–Farber Cancer Institute partially reversed age-related degeneration in mice by engineering an improved telomerase gene. 2012 It was discovered that protein Sirtuin 6 (SIRT6) regulates the lifespan of male mice (but not female mice).
A childhood friend of Charmaine's named Tracey Giles, who had lived in the upper flat at 25 Midland Road, would later recollect an incident in which she had entered the Wests' flat unannounced only to see Charmaine, naked and standing on a chair, gagged and with her hands bound behind her back with a belt, as Rose stood alongside the child with a large wooden spoon in her hand. According to Giles, Charmaine had been "calm and unconcerned", while Anne Marie had been standing by the door with a blank expression on her face. Hospital records later revealed that Charmaine had received treatment for a severe puncture wound to her left ankle in the casualty unit of Gloucestershire Royal Hospital on 28 March 1971. This incident was explained by Rose as having resulted from a household accident.
=== Side effects and contraindications === Research has shown a limited side effect profile for honokiol, and it appears to be well tolerated. However, its antithrombotic effects could cause hemorrhage especially in patients with conditions that would put them at a higher risk like hemophilia or Von Willebrand disease. Additionally, patients already taking anticoagulants should talk to their doctor before taking honokiol supplements. In a 2002 study, researchers induced cell death in fetal rat cortical neurons by directly applying 100μM in vitro.
Sources: en.wikipedia.org
Moreover, the absolute uranium concentrations indicate that there was no contamination of the earthworm species studied." Though a more comprehensive assessment is possible, a 2011 update on a cancer scare regarding Italian soldiers who had served in the Balkans found lower than expected incidence rates for all cancers, a finding "consistent with lacking evidence of an increased cancer incidence among troops of other countries deployed in the areas of Iraq, Bosnia, and Kosovo, where armour-penetrating depleted uranium shells have been used." In 2018, Serbia set up a commission of inquiry into the consequences of the use of depleted uranium during the 1999 NATO bombing of Yugoslavia in southern Serbia and its link to the rise of diseases and tumors among citizens, particularly in young children born after 1999. Zoran Radovanovic, an epidemiologist and the chairman of the Serbian Medical Association's ethics committee, denied that there had been a rise in cancer cases in areas where bombings had taken place. He continued by saying that Serbians frequently worry about a cancer epidemic that does not exist. NATO has repeatedly claimed that depleted uranium found in the ammunition used in the 1999 bombardments cannot be linked to adverse health effects.
=== Other mechanisms === Bimagrumab, an experimental drug, works by inhibiting the action of myostatin, which limits the size of skeletal muscle. The drug has shown the ability to increase lean mass simultaneously to decreasing fat mass in obese humans, which is beneficial because it preserves or increases energy expenditure while reducing risks associated with excess fat. Orlistat (Xenical) and cetilistat are lipase inhibitors that reduce intestinal fat absorption by inhibiting pancreatic lipase, an enzyme that breaks down triglycerides in the intestine. Without this enzyme, triglycerides from the diet are prevented from being hydrolyzed into absorbable free fatty acids and are excreted undigested. Frequent oily bowel movements steatorrhea is a possible side effect of using orlistat. Originally available only by prescription, it was approved by the FDA for over-the-counter sale in February 2007. SGLT2 inhibitors cause the loss of 60–100 grams (2.1–3.5 oz) glucose in the urine each day and are associated with a modest, sustained weight loss of 1.5–2 kilograms (3.3–4.4 lb) in people with type 2 diabetes. The weight loss is less than expected due to compensatory increases in energy intake, but is additive when combined with GLP-1 receptor agonists.
==== Codon models ==== Codon models describe the evolution of protein-coding nucleic acid sequences. The simplest codon model, MG, estimates one parameter: nonsynonymous/synonymous mutation ratio. The more complex GY also estimates transition/transversion rate ratios. Both of these are mechanistic models. They can be expanded by the addition of rate parameters. Empirical codon models directly describe the odds of one non-stop codon (61 in the standard code) being replaced by another, making them similar to amino acid exchangability matrices. By their construction, they are tied to the genetic code found in the data used to construct them. They can also be combined with a mechanistic model by multiplying the two estimated rates, adding back the ability to adapt to the data being processed.
Sources: en.wikipedia.org
Purity is commonly expressed as the percentage of the main peak relative to all integrated peaks in a reversed-phase chromatogram. Related substances and counter-ions are reported separately. Values obtained with different detectors are not always directly comparable.
Aggregation is driven by hydrophobic contacts, especially those involving the fatty acid side chain, and is accelerated by heat, agitation, and repeated freezing and thawing. Low pH and suitable excipients can reduce the rate. The tendency differs between formulations.
Dry powder has low molecular mobility and tolerates colder storage for longer periods. Water enables hydrolysis and conformational change, so dissolved material is kept refrigerated and used within a shorter window.
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.