If you have been reading about Aib substitution 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.
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.
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.
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.
| 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 |
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.
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.
Large randomised trials in adults with type 2 diabetes and in adults with obesity have reported reductions in body weight and improvements in several cardiovascular risk markers. One outcome trial found a lower incidence of major adverse cardiovascular events in participants with diabetes and established cardiovascular disease. Gastrointestinal effects such as nausea and vomiting are the most frequently reported adverse events and often diminish over time. Changes in lean body mass during weight loss are an area of ongoing investigation. Effects in adolescents and in pregnancy are less well characterised, and current labelling advises against use during pregnancy.
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.
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.
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.
== The TRAIL receptors as a drug target == In clinical trials only a small proportion of cancer patients responded to various drugs that targeted TRAIL death receptors. Many cancer cell lines develop resistance to TRAIL and limits the efficacy of TRAIL-based therapies.
Encroachment on wildlife habitats. The construction of new villages and housing developments in rural areas force animals to live in dense populations, creating opportunities for microbes to mutate and emerge. Changes in agriculture. The introduction of new crops attracts new crop pests and the microbes they carry to farming communities, exposing people to unfamiliar diseases. The destruction of rain forests. As countries make use of their rain forests, by building roads through forests and clearing areas for settlement or commercial ventures, people encounter insects and other animals harboring previously unknown microorganisms. Uncontrolled urbanization. The rapid growth of cities in many developing countries tends to concentrate large numbers of people into crowded areas with poor sanitation. These conditions foster transmission of contagious diseases. Modern transport. Ships and other cargo carriers often harbor unintended "passengers", that can spread diseases to faraway destinations. While with international jet-airplane travel, people infected with a disease can carry it to distant lands, or home to their families, before their first symptoms appear.
These experiments are designed to clone and express transporter genes in host cells to further analyze the three-dimensional structure of uniporters, as well as directly observe the movement of ions through proteins in real-time. The discovery of mutations in uniporters has been linked to diseases such as GLUT1 deficiency syndrome, cystic fibrosis, Hartnup disease, primary hyperoxaluria and hypokalemic periodic paralysis.
The total ion current chromatogram (TICC) represents the summed intensity across the entire range of masses being detected at every point in the analysis. The range is typically several hundred mass-to-charge units or more. In complex samples, the TICC often provides limited information as multiple analytes elute simultaneously, obscuring individual species.
Most reptiles are insectivorous or carnivorous and have simple and comparatively short digestive tracts due to meat being fairly simple to break down and digest. Digestion is slower than in mammals, reflecting their lower resting metabolism and their inability to divide and masticate their food. Their poikilotherm metabolism has very low energy requirements, allowing large reptiles like crocodiles and large constrictors to live from a single large meal for months, digesting it slowly. While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous megafauna: in the Paleozoic, the pareiasaurs; and in the Mesozoic several lines of dinosaurs. Today, turtles are the only predominantly herbivorous reptile group, but several lines of agamas and iguanas have evolved to live wholly or partly on plants. Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles (so called gastroliths) to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter. Fossil gastroliths have been found associated with both ornithopods and sauropods, though whether they actually functioned as a gastric mill in the latter is disputed. Salt water crocodiles also use gastroliths as ballast, stabilizing them in the water or helping them to dive. A dual function as both stabilizing ballast and digestion aid has been suggested for gastroliths found in plesiosaurs.
Sources: en.wikipedia.org
== Trial and imprisonment == Allitt had attacked 13 children, four fatally, over a 59-day period. It was only following the death of Becky Phillips that medical staff became suspicious of the number of cardiac arrests on the children's ward and police were called in. It was found that Allitt was the only nurse on duty for all the attacks on the children and had access to the drugs used. Four of Allitt's victims had died. She was charged with four counts of murder, eleven counts of attempted murder, and eleven counts of causing grievous bodily harm. Allitt entered pleas of not guilty to all charges. On 28 May 1993, she was found guilty on each charge and sentenced to 13 concurrent terms of life imprisonment, which she is serving at Rampton Secure Hospital in Nottinghamshire. On 6 December 2007, Mr Justice Stanley Burnton, sitting in the High Court of Justice, London, ordered Allitt to serve the original minimum sentence of 30 years. It was reported that some families of Allitt's victims had previously mistakenly believed that her minimum tariff had been set at 40 years. Her minimum tariff expired in November 2021 and she is now eligible for release on parole. Allitt's motives have never been fully explained. According to one theory, she showed symptoms of a factitious disorder also known as Munchausen syndrome by proxy. On 3 October 2023, it was reported that Allitt was appearing before a mental health tribunal to be assessed for a potential transfer to a mainstream prison. If the transfer takes place, Allitt will be eligible for parole after six months.
== Catalytic mechanism == The accepted catalytic mechanism, called the “ping-pong mechanism,” consists of four major stages. The first stage is the oxidation of the substrate by the double-redox center. After the hydroxyl group of substrate alcohol occupies the solvent coordination site, the hydroxyl group is deprotonated by Tyr495, followed by the release of Tyr495. This step makes the alcohol more prone to oxidation. The proton on the carbon to which the hydroxyl group used to be attached is then transferred to Tyr272 (serving as the hydrogen acceptor), coupled with the oxidation of the substrate. One electron goes to the radical ligand, the other electron goes to the copper(II) center, which is then reduced to copper(I) as a result. Meanwhile, Tyr272 radical is also reduced. The proton subtraction step is rate determining and stereospecific since only the pro-S hydrogen on the alcohol carbon is removed (supported by studies of its kinetic isotope effect). The overall result of stage 1 is the removal of two hydrogen atoms and the removal two electrons from the substrate, of which the order is unclear, however. The second stage is the release of oxidized substrate (aldehyde in this case) and the coordination of dioxygen at the substrate coordination site. In the third stage, dioxygen is rapidly reduced by copper(I) to form superoxide. The superoxide is a reactive species that subtracts the proton and an electron from the Tyr272 and re-forms the tyrosine radical. In the fourth stage, the hydroperoxide deprotonates Tyr496 and is released as H2O2.
The phenomenon of the tech bro, or brogrammer, sees bro culture take root in the technology industry. The term is almost always applied pejoratively, generally in reference to a workplace culture that undervalues people who do not fit into the bro lifestyle, particularly women. Brogrammer culture can be contrasted with geek culture, which is said to value ability and passion over image. In 2013, former Microsoft game designer Daniel Cook wrote that the company was responsible for developing the bro subculture within video gaming, explaining that the "Xbox put machismo, ultra-violence and chimpboys with backwards caps in the spotlight. [...] Gamers were handed a pre-packaged group identity via the propaganda machine of a mega corporation." Cook writes that Microsoft has done this in order to distance the Xbox from its console competitors, which were portrayed as "kids platform[s]".
Multipolar neurons: Have 3 or more processes coming off the soma (cell body). They are the major neuron type in the CNS and include interneurons and motor neurons. Bipolar neurons: Sensory neurons that have two processes coming off the soma, one dendrite and one axon Pseudounipolar neurons: Sensory neurons that have one process that splits into two branches, forming the axon and dendrite Unipolar brush cells: Are excitatory glutamatergic interneurons that have a single short dendrite terminating in a brush-like tuft of dendrioles. These are found in the granular layer of the cerebellum. Neuroglia encompasses the non-neural cells in nervous tissue that provide various crucial supportive functions for neurons. They are smaller than neurons, and vary in structure according to their function. Neuroglial cells are classified as follows:
=== Cannabinoids in other plants === Phytocannabinoids occur in plants like Echinacea purpurea, Echinacea angustifolia, Acmella oleracea, Helichrysum umbraculigerum, and Radula marginata. Echinacea species contain Anandamide-like alkylamides, with at least 25 identified, some showing affinity for CB2 receptors. These are concentrated in roots and flowers. Yangonin in kava has significant CB1 receptor affinity. Tea (Camellia sinensis) catechins show affinity for human cannabinoid receptors. Beta-caryophyllene, a terpene in cannabis and other plants, is a selective CB2 receptor agonist. Black truffles contain anandamide. Perrottetinene, a moderately psychoactive cannabinoid, is found in Radula varieties. Machaeriol A and related compounds occur in Machaerium plants. Most phytocannabinoids are nearly insoluble in water but soluble in lipids, alcohols, and other non-polar organic solvents.
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.
It belongs to the incretin mimetic class and acts as a long-acting glucagon-like peptide-1 receptor agonist. The class includes several peptides with different half-lives and routes of administration.