A practical reference on deamidation: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-04-03 and is reviewed periodically as new material appears.
Semaglutide is a synthetic peptide analog of glucagon-like peptide-1, a hormone released from intestinal L cells after food intake. The molecule is a 31-amino-acid backbone modified at three positions to resist cleavage by dipeptidyl peptidase-4, the enzyme that degrades native GLP-1 within minutes. A lysine residue at position 26 carries a linker and a C18 fatty diacid, which promotes binding to serum albumin and slows renal clearance. These changes extend the circulating half-life from roughly two minutes to about one week in humans.
The sequence incorporates alpha-aminoisobutyric acid at position 8, replacing the alanine found in the natural hormone. This substitution blocks the primary DPP-4 recognition site and contributes most of the enzymatic stability. Albumin binding further protects the peptide and reduces the frequency of administration required to maintain active plasma levels. Because the fatty acid chain increases lipophilicity, the compound is formulated as a solution rather than a simple aqueous buffer. Researchers describe the design as an incremental optimization of earlier GLP-1 analogs rather than a wholly new scaffold.
Reported molecular weight is approximately 4113.6 daltons for the free base, and the peptide is supplied as a lyophilized powder or in buffered liquid form depending on the intended use. It is freely soluble in water when formulated with appropriate excipients, though the unconjugated peptide shows limited stability at neutral pH over long periods. Analytical characterization typically relies on reversed-phase high-performance liquid chromatography and mass spectrometry. Purity specifications for research-grade material commonly exceed ninety-five percent by area. Isotopic and impurity profiles differ between suppliers.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula (free base) | C187H291N45O59 | Approximate; salt and hydrate forms differ |
| Molecular weight | ~4113.6 Da | Varies with counterion and hydration |
| Appearance | White to off-white powder | Lyophilized research material |
| Solubility class | Freely soluble in water | As formulated; native peptide less stable near neutral pH |
| Typical storage | 2 to 8 degrees Celsius | Protect from light; avoid repeated freeze-thaw |
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.
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.
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.
Stability studies examine how temperature, pH, and moisture influence degradation rates over time. In aqueous solution, hydrolysis and deamidation accelerate as pH moves away from mildly acidic conditions. Light exposure and residual metal ions can also trigger oxidation of susceptible residues. Accelerated aging at elevated temperature is used to estimate shelf life, though extrapolation to room temperature carries uncertainty because individual degradation pathways do not always scale predictably.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released after nutrient intake. The molecule contains 31 amino acid residues and differs from the native sequence at several positions. A non-natural residue at position eight resists the enzyme that normally truncates the hormone, while a lysine-linked fatty diacid side chain promotes binding to serum albumin. These two modifications extend the circulating half-life from minutes to roughly one week. The peptide is produced by solid-phase synthesis followed by selective acylation, and its identity and purity are confirmed by spectrometric and chromatographic techniques.
The primary target is the GLP-1 receptor, a class B G protein-coupled receptor expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises intracellular cyclic AMP, which potentiates glucose-dependent insulin secretion and lowers glucagon release when blood glucose is elevated. Signalling in the hypothalamus and brainstem is associated with reduced appetite and slower gastric emptying. Because the insulinotropic effect depends on prevailing glucose levels, the hypoglycaemic risk of the peptide alone is described as low in most study settings. The relative contribution of peripheral and central actions remains an active research question.
== Pathophysiology == Dupuytren’s contracture is a fibroproliferative disorder of the palmar fascia in which abnormal activation of fibroblasts and myofibroblasts, driven by mediators such as transforming growth factor-beta, platelet-derived growth factor, epidermal growth factor, interleukin-1 beta, and connective tissue growth factor, leads to excess deposition of type III collagen and progressive remodeling of fascial tissue. Studies have suggested that intracellular signaling, as opposed to paracrine or endocrine signaling, may be the strongest driver of abnormal fibroblast activity in most cases of Dupuytren's contracture. The disease typically evolves through a proliferative stage marked by cellular nodules rich in immature fibroblasts and myofibroblasts, an involution stage in which these cells align along longitudinal stress lines in the hand, and a residual stage in which dense, relatively hypocellular collagenous cords persist and mechanically flex the digits. As normal fascial structures are converted into pathologic cords, characteristic deformities emerge: central cords commonly produce skin puckering and metacarpophalangeal contracture, natatory cords (developed from the natatory ligament) narrow the web spaces, and spiral cords can cause proximal interphalangeal contracture while displacing the digital neurovascular bundle.
==== Metabolism ==== Propranolol undergoes metabolism via aromatic hydroxylation (mainly 4-hydroxylation), N-dealkylation, side-chain oxidation, and glucuronidation. The metabolism of propranolol involves cytochrome P450 enzymes including CYP2D6, CYP1A2, and CYP2C19. CYP1A2 and CYP2D6 have a major role, while CYP2C19 and CYP3A4 have a minor role. The main metabolite 4-hydroxypropranolol, which has a longer elimination half-life than propranolol, is also pharmacologically active.
A Loner addresses the themes of depression and the need for isolation, as Chanut was affected by these issues during the lockdown period, which coincided with the writing of the album. "A Thousand Miles Away", the last song on the album, marked the onset of Chanut's depression; the lyrics he wrote were about his father's death. David stated that A Loner's musical approach and themes addressed are "purely personal" and that the lyrics "evoke despair without making it an end in itself." "Dark, brooding and unapologetically downbeat on record", wrote Kerrang!'s Sam Law. In 2025, Toufouti stated that he found it interesting to elaborate on a sad individual or subject, as he felt there was material to develop. Saddiction continued in the vein of A Loner by being "more personal, more introspective", said Chanut. Before entering the studio, Toufouti slightly reworked the lyrics of "Neglect" to evoke his relationship with his father, who had just passed away. Lemaire wrote that the song's title, "Kowloon Lights", as well as the large block of buildings on the front cover of Sadditcion, point to a city theme. Chanut responded by elaborating on the feeling of loneliness in crowds, particularly in large cities like Paris, as well as on the mobile phone culture where everyone is focused on their own things. "Kowloon Lights" refers to the former densely populated enclave within the Hong Kong colony. Chanut commented on the grey buildings that made up the city and its colourful neon lights, often depicted in many Hong Kong films of the 1980s.
The Jewish Federations of North America expressed support for TikTok to be banned, while Israel's critics denounced the "criminalisation of pro-Palestinian voices", including on TikTok, which has been used to condemn "Israel's atrocities", according to The New Arab. TikTok was also accused by Malaysia's minister of communications, Fahmi Fadzil of suppressing pro-Palestinian content. The company stated it banned praising Hamas and removed more than 775,000 videos and 14,000 livestreams. There has also been reporting on the trend of Israeli soldiers using TikTok to mock Palestinians and boast about their actions in the Gaza Strip. According to Huda Abudagga, a legal advisor for the British nonprofit Law for Palestine, many of the videos show soldiers partaking in actions, such as the destruction of Palestinian homes as well as the theft of private and public property, that are considered war crimes under international law. Similarly, four legal experts consulted by the New York Times said that the videos "could be used to show unlawful destruction, a violation of the Geneva Conventions." One such video, which showed Israeli soldiers dancing and singing "There are no uninvolved civilians", was included as evidence of genocidal intent in South Africa's case against Israel before the International Court of Justice. In November 2023, Osama bin Laden's 2002 "Letter to the American people" went viral on TikTok and other social media. In the letter, he denounced the US and its support for Israel, and supported al-Qaeda's war against the US as a defensive struggle.
Sources: en.wikipedia.org
==== Controversy over Juan Silva ==== On 3 November 2021, Transportation Minister Juan Silva announced an agreement with transport unions. Prior to the agreement, the transport unions of Lima and Callao had announced plans to strike. The agreement involved the replacement of the president of the Urban Transportation Authority, and the head of the Superintendence of Land Transport of People, Cargo and Goods (Sutran). The new head of the Sutran resigned 6 days later, following the revelation that 3 police complaints had been filed against her for alleged robberies at shopping centers. On 11 November 2021, Congress voted against interpelling Silva, in part due to Popular Force abstaining. Since Popular Force and its Fujmorist ideology are seen as being staunchly opposed to Castillo, their decision to abstain drew much criticism from anti-Castillo hardliners. Popular Force's spokesperson, Hernando Guerra García, responded to the criticism by saying that the "spotlight" shouldn't be on two things at once, referring to the pressure campaign against the then Defense Minister Walter Ayala and this case. Guerra García said that interpellation would go "minister by minister." On 18 November 2021, Congress accepted a new motion to interpellate Juan Silva. The motion was proposed by Popular Force.
== Synthesis == SRTXs are abundant in venoms, whereas ETs are present in a low concentration in mammals. Both ETs and SRTXs are generated in vivo by proteolytic cleavage from larger precursors. They also can be produced by solid phase peptide synthesis and fold spontaneously in vitro in high yield into native tertiary structures, with the correct disulfide bond pairing of cysteines. SRTXs complete cDNA sequence comprises 1948 base pairs (bp) coding for a pre-pro-polypeptide of 543 amino acids, which starts with a methionine that initiates translation followed by a hydrophobic peptide characteristic of a signal sequence. The amino acid sequence comprises one sequence of 39 amino acidic residues followed by 11 sequences of 40 residues, each of it contains one SRTX sequence preceded by 19 spacer amino acids. The SRTX-c isoform is the most abundant in the venom and is also the isoform with the greatest number of copies (five in all) in the precursor.
The Environmental Investigation Agency in 2016 estimated that 34 species of fish were being traded on the wider Chinese fish maw market. Sciaenidae (croakers/drums) are typically the most valued, due to their similarity to the historically prized and critically endangered Chinese bahaba. Other targeted fishes include eels, stonefishes, lates perch, groupers, threadfins and sturgeon.
Sources: en.wikipedia.org
In the eastern United States in the early 2000s, sulfate particles were estimated to account for 25% or more of all air pollution. Exposure to sulfur dioxide emissions by coal power plants (coal PM2.5) in the US was associated with 2.1 times greater mortality risk than exposure to PM2.5 from all sources. Meanwhile, the Southern Hemisphere had much lower concentrations due to being much less densely populated, with an estimated 90% of the human population in the north. In the early 1990s, anthropogenic sulfur dominated in the Northern Hemisphere, where only 16% of annual sulfur emissions were natural, yet amounted for less than half of the emissions in the Southern Hemisphere.
In most of Asia, several Sub-Saharan Africa and Pacific markets, rice based side dishes are often sold. In Greece and Bulgaria, potato wedges are sold instead of French fries. In a number of Eastern European locations and Portugal, beer is offered in addition to soft drinks. In 2023 KFC branches in UK and Ireland introduced new 'signature fries' (fries coated in herbs and spice) in an attempt to improve the taste of the fries.
This results in rhinorrhea, itchiness, dyspnea, and anaphylaxis. Depending on the individual, allergen, and mode of introduction, the symptoms can be system-wide (classical anaphylaxis) or localized to specific body systems. Asthma is localized to the respiratory system, and eczema is localized to the dermis.
Sources: en.wikipedia.org
It is a modified version of the natural hormone, with three amino acid changes and a fatty acid side chain added. These edits extend its half-life from minutes to about one week. The core receptor activity is retained.
Both deliver the same active peptide and act on the same receptor. The tablet includes an absorption enhancer because peptides are poorly taken up intact from the gut. Bioavailability of the oral route is substantially lower, so the two are not dose-equivalent.
No, it is entirely synthetic and does not occur in nature. Native GLP-1 is produced in the gut and pancreas, but the analog is manufactured by chemical synthesis or recombinant methods. Traces of the analog are not expected in people who never received it.
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.