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 2026-01-09. 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.
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.
Three structural changes define the molecule. At position 8 an alpha-aminoisobutyric acid residue replaces alanine, which blocks dipeptidyl peptidase-4 cleavage. At position 34 arginine replaces lysine, and at position 26 a lysine carries a C18 fatty diacid attached through a short linker. The fatty chain binds serum albumin, and this albumin association reduces renal filtration and enzymatic attack. The unchanged backbone retains the receptor contacts that produce signalling. The free base has the formula C187H291N45O59 and a molecular weight near 4114 daltons.
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.
| 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 |
Degradation proceeds along several parallel routes. Deamidation of asparagine and glutamine residues generates charged variants that shift retention time in chromatographic analysis. Oxidation targets methionine and can be accelerated by trace metals or dissolved oxygen. Non-covalent aggregation produces dimers, oligomers, and larger species that are difficult to reverse. Isomerisation at aspartate residues is slower but measurable under thermal stress. The distribution among these pathways depends on pH, buffer composition, ionic strength, and the presence of excipients such as sugars or surfactants.
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.
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.
GLP-1 receptors are expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises cyclic AMP, enhances glucose-dependent insulin secretion, and suppresses glucagon release when blood glucose is high. Effects on gastric emptying and on hypothalamic appetite circuits reduce energy intake. Because insulin release remains glucose-dependent, the risk of hypoglycemia is low when the drug is used alone. The precise contribution of each pathway to body weight change in humans remains an area of active investigation.
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.
Lyophilized semaglutide powder is typically held at minus twenty degrees Celsius for long-term storage. At that temperature, solid-state degradation reactions proceed slowly and the peptide remains intact for extended periods. Repeated freeze-thaw cycles are best avoided because they promote aggregation and can shift the proportion of monomeric peptide present. Working aliquots are often prepared so that each portion is thawed only once, and desiccant is placed inside the vial to limit moisture uptake.
Identity and purity are usually assessed by reverse-phase high-performance liquid chromatography coupled to mass spectrometry. Retention time and observed mass are compared against a reference standard run under identical conditions. Impurity profiles reveal deamidation products, oxidized methionine variants, and truncated fragments that arise during synthesis or storage. Peptide mapping through enzymatic digestion confirms the primary sequence, while amino acid analysis offers an independent check on overall composition.
It may also be possible to generate isotopes in the island of stability such as 298Fl in multi-nucleon transfer reactions in low-energy collisions of actinide nuclei (such as 238U and 248Cm). This inverse quasifission (partial fusion followed by fission, with a shift away from mass equilibrium that results in more asymmetric products) mechanism may provide a path to the island of stability if shell effects around Z = 114 are sufficiently strong, though lighter elements such as nobelium and seaborgium (Z = 102–106) are predicted to have higher yields. Preliminary studies of the 238U + 238U and 238U + 248Cm transfer reactions have failed to produce elements heavier than mendelevium (Z = 101), though the increased yield in the latter reaction suggests that the use of even heavier targets such as 254Es (if available) may enable production of superheavy elements. This result is supported by a later calculation suggesting that the yield of superheavy nuclides (with Z ≤ 109) will likely be higher in transfer reactions using heavier targets. A 2018 study of the 238U + 232Th reaction at the Texas A&M Cyclotron Institute by Sara Wuenschel et al. found several unknown alpha decays that may possibly be attributed to new, neutron-rich isotopes of superheavy elements with 104 < Z < 116, though further research is required to unambiguously determine the atomic number of the products. This result strongly suggests that shell effects have a significant influence on cross sections, and that the island of stability could possibly be reached in future experiments with transfer reactions.
Amirim, Israel. Founded in 1958 on vegetarian principles, the town features vegetarian guest houses and had a population of 865 in 2022. Cheremshanka, Altai Republic in Russia Community of the Ark, La Borie Noble, France. Founded in 1948 by Lanza del Vasto as a vegetarian, spiritual commune. Haridwar in Uttarakhand, India. In 2002 meat sales were banned in Haridwar. The ban was upheld by the Supreme Court in 2004. New Vrindaban in West Virginia, United States. Founded in 1968 by Kirtanananda Swami, New Virndaban is a vegetarian, intentional community. Palitana in Gujarat, India. In 2014, Palitana banned meat sales. Pushkar in Rajasthan, India. Pushkar is one of the world's oldest cities and a religious center. Because of its holy status and number of temples, Pushkar is a vegetarian city where the sale of meat, fish, eggs, and alcohol are all banned. Rishikesh in Uttarakhand, India. In 1956, Rishikesh banned the sale of meat, fish, and eggs. Tirumala in Andhra Pradesh, India The Farm in Tennessee, United States. Founded in 1971 by Stephen Gaskin and 300 spiritual seekers as a vegan, intentional community.
==== 2020s ==== On October 28, 2020, Panera announced they would add pizza to their menu to increase dinner options for customers. Panera announced on August 25, 2021, that it had merged with Caribou Coffee and Einstein Bros. Bagels to form Panera Brands. In August 2022, the company announced that it was testing the use of artificial intelligence in its drive-thru lanes via two locations in upstate New York. It used OpenCity's voice ordering technology, Tori. At the time of the announcement, roughly 45% of the chain's locations had drive-thru lanes. In making this move, the firm was joining other firms in the restaurant industry, like McDonald's, Burger King, and Taco Bell, and it came on top of other uses of artificial intelligence at the chain. In September 2022, Panera announced that legacy St. Louis Bread Co. locations outside St. Louis City and St. Louis County would be rebranded as Panera when remodeled, with locations in the inner core of the metro retaining the Bread Co. name. One location in St. Louis County is named Panera as it is a prototype of the "Next Gen" restaurant design. In mid-2023, Panera moved its headquarters from Sunset Hills to Fenton, Missouri, downsizing the square footage by more than half. The move preceded two rounds of corporate layoffs in late 2023 and 2024. In December 2023, it was learned that Panera Bread confidentially filed to go public again. The company was last publicly traded in 2017 before being acquired by JAB Holding for $7.5 billion.
The MOSFET invented at Bell Labs between 1955 and 1960, Two years later, L.C. Clark and C. Lyons invented the biosensor in 1962. Biosensor MOSFETs (BioFETs) were later developed, and they have since been widely used to measure physical, chemical, biological and environmental parameters. The first BioFET was the ion-sensitive field-effect transistor (ISFET), invented by Piet Bergveld for electrochemical and biological applications in 1970. the adsorption FET (ADFET) was patented by P.F. Cox in 1974, and a hydrogen-sensitive MOSFET was demonstrated by I. Lundstrom, M.S. Shivaraman, C.S. Svenson and L. Lundkvist in 1975. The ISFET is a special type of MOSFET with a gate at a certain distance, and where the metal gate is replaced by an ion-sensitive membrane, electrolyte solution and reference electrode. The ISFET is widely used in biomedical applications, such as the detection of DNA hybridization, biomarker detection from blood, antibody detection, glucose measurement, pH sensing, and genetic technology. By the mid-1980s, other BioFETs had been developed, including the gas sensor FET (GASFET), pressure sensor FET (PRESSFET), chemical field-effect transistor (ChemFET), reference ISFET (REFET), enzyme-modified FET (ENFET) and immunologically modified FET (IMFET). By the early 2000s, BioFETs such as the DNA field-effect transistor (DNAFET), gene-modified FET (GenFET) and cell-potential BioFET (CPFET) had been developed.
Sources: en.wikipedia.org
Relugolix is a selective antagonist of the gonadotropin-releasing hormone receptor (GnRHR), with a half-maximal inhibitory concentration (IC50) of 0.12 nM. A dosage of relugolix of 40 mg once per day has been found to suppress estradiol levels to postmenopausal levels (<20 pg/mL) within 24 hours in premenopausal women. In the control group of women, estradiol levels fluctuated between 50 and 250 pg/mL. Estradiol levels have been found to return to normal concentrations within 4 weeks of discontinuation of relugolix in premenopausal women. The medication additionally suppresses levels of progesterone, luteinizing hormone, and follicle-stimulating hormone in premenopausal women. Relugolix at a dosage of 40 mg or more once per day has been found to reduce testosterone levels to sustained castrate levels (<20 ng/dL) in men. It additionally suppresses luteinizing hormone and follicle-stimulating hormone levels in men. Lower doses of relugolix (<40 mg/day) are under investigation for achieving partial sex hormone suppression in the treatment of endometriosis and uterine fibroids. This is intended to reduce the incidence and severity of menopausal symptoms such as hot flushes and decreased bone mineral density that are secondary to estrogen deficiency.
Over the years National Semiconductor acquired several companies like Fairchild Semiconductor (1987), and Cyrix (1997). However, over time National Semiconductor spun off these acquisitions. Fairchild Semiconductor became a separate company again in 1997, and the Cyrix microprocessors division was sold to VIA Technologies of Taiwan in 1999. From 1997 to 2002, National enjoyed a large amount of publicity and awards with the development of the Cyrix Media Center, Cyrix WebPad, WebPad Metro and National Origami PDA concept devices created by National's Conceptual Products Group. Based largely on the success of the WebPad, National formed the Information Appliance Division (highly integrated processors & "internet gadgets") in 1998. The Information Appliance Division was sold to AMD in 2003. Other businesses dealing in such products as digital wireless chipsets, image sensors, and PC I/O chipsets have also been recently closed down or sold off as National has reincarnated itself as a high-performance analog semiconductor company.
Oral use of the antifungal ketoconazole has been associated with hepatic toxicity, including some fatalities; however, such effects appear to be limited to doses taken over a period longer than 7 days.
== Structure and properties == Because of slow rotation about the N-C(O) bond, NMF exists as two rotamers that can be distinguished by NMR spectroscopy. The two principal resonance structures for one of these rotamers is shown:
These reductions in metabolic rate and heart rate do not appear to decrease the bear's ability to heal injuries during hibernation. Their circadian rhythm stays intact during hibernation. This allows the bear to sense the changes in the day based on the ambient temperature caused by the sun's position in the sky. It has also been shown that ambient light exposure and low disturbance levels (that is to say, wild bears in ambient light conditions) directly correlate with their activity levels. The bear keeping track of the changing days allows it to awaken from hibernation at the appropriate time of year to conserve as much energy as possible. The hibernating bear does not display the same rate of muscle and bone atrophy relative to other nonhibernatory animals that are subject to long periods of inactivity due to ailment or old age. A hibernating bear only loses approximately half the muscular strength compared to that of a well-nourished, inactive human. The bear's bone mass does not change in geometry or mineral composition during hibernation, which implies that the bear's conservation of bone mass during hibernation is caused by a biological mechanism. During hibernation American black bears retain all excretory waste, leading to the development of a hardened mass of fecal material in the colon known as a fecal plug. Leptin is released into the bear's systems to suppress appetite. The retention of waste during hibernation (specifically in minerals such as calcium) may play a role in the bear's resistance to atrophy.
Sources: en.wikipedia.org
=== Other drugs === Alosetron — used in the management of severe chronic diarrhea-predominant irritable bowel syndrome (IBS-D) in females not responsive to conventional therapy; its use is restricted due to serious gastrointestinal adverse reactions, such ischemic colitis and complications of constipation. Cisapride — used for severe gastroesophageal reflux disease (GERD); carries risk of heart arrhythmias. Clomethiazole — a sedative/hypnotic agent used in the treatment of alcohol withdrawal when benzodiazepines are not effective; its use is limited due to its high toxicity and potential for addiction. Clozapine — used in treatment-resistant schizophrenia not responsive to at least two different antipsychotics; its use is limited due to the risk of severe side effects including agranulocytosis, seizures and myocarditis. Felbamate — an anticonvulsant used in refractory epilepsy; associated with an increased risk of aplastic anemia and liver failure. Isotretinoin — used when all topical treatments or antibiotics against acne have failed, it permanently dries out the sebum production of the skin and is often a permanent solution against acne; can cause severe side effects including severe nosebleeds, birth defects when taken while pregnant, depression, hair loss and can permanently dry out the skin all over the body. Levosimendan — used in acutely decompensated severe chronic heart failure in situations where conventional therapy is not sufficient; not yet approved in the US.
=== Urine collection === Furthermore, when the semen volume is low, less than 1 ml, a urine specimen should be collected immediately after masturbation to search for sperm in the urine. Two days before the urine sample is collected, one is required to drink an alkalinized water to allow the sperm cells to survive. After this preliminary preparation step, urine collection is done in a fractional way: the first milliliters of urine are collected and analyzed in isolation through centrifugation and examination under a microscope. The presence of substantial sperm in the post-ejaculatory urine specimen confirms the diagnosis of partial retrograde ejaculation, a dysfunction of the ejaculatory reflex and a known cause of hypospermia. Unfortunately, even after thorough etiological assessments, an assessor many come to the conclusion of no known etiological cause to explain one's diagnosis of hypospermia. The significance of these idiopathic hypospermia cases are currently unknown and requires more research in the future.
=== Cost and generics === Bicalutamide is off-patent and available as a generic. Unlike bicalutamide, the newer NSAA enzalutamide is still on-patent, and for this reason, is considerably more expensive in comparison. The patent protection of all three of the first-generation NSAAs has expired and flutamide and bicalutamide are both available as low-cost generics. Nilutamide, on the other hand, has always been a poor third competitor to flutamide and bicalutamide and, in relation to this fact, has not been developed as a generic and is only available as brand name Nilandron, at least in the U.S. Bicalutamide is considerably less costly than GnRH analogues, which, in spite of some having been off-patent many years, have been reported (in 2013) to typically cost US$10,000–$15,000 per year (or about US$1,000 per month) of treatment.
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.
==== Mayhew's leaked letter ==== By now the political row was being discussed in the media, partly because of the lack of other news in December. Cuckney wrote to Thatcher, at her behest, asking for reassurance that the Sikorsky deal would not damage Westland's business prospects in Europe. Heseltine was not satisfied with Thatcher's draft reply when he saw it and consulted Sir Patrick Mayhew (Solicitor-General and acting attorney-general as Sir Michael Havers was ill) on the grounds that the government might be legally liable for any incorrect advice. Heseltine supplied extra material about the risk of losing European business, which Thatcher did not include in her reply to Cuckney. Heseltine then wrote to David Horne of Lloyds Merchant Bank, who was advising the European consortium (in reply to planted questions from Horne which had been dictated to him over the phone by one of Heseltine's staff), giving him the advice which Thatcher had declined to include in her letter to Cuckney (that the Sikorsky deal would be "incompatible with participation" in European helicopter projects). Heseltine's letter was also leaked to the press. This was a blatant challenge to Thatcher's authority as Heseltine had not consulted Downing Street, the Department of Trade and Industry or Mayhew before writing to Horne. Thatcher discussed sacking Heseltine with close colleagues over Christmas; but, as she later admitted in her memoir, refrained from doing so as he was too popular and important as a political figure.
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.
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.