A practical reference on receptor agonist: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-07-16. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Acylated GLP-1 receptor agonist | 31-residue synthetic peptide |
| Molecular formula | C187H291N45O59 | established for the free peptide |
| Appearance | White to off-white powder | as supplied before formulation |
| Solubility | Freely soluble in water | aqueous buffers near neutral pH |
| Typical storage | 2 to 8 degrees Celsius, protected from light | powder and solution forms differ in shelf life |
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。
Semaglutide 是一种经结构修饰的胰高血糖素样肽-1 类似物，其主链与内源性 GLP-1(7-36) 约有百分之九十四的序列一致性。第 8 位丙氨酸被 α-氨基异丁酸取代，使二肽基肽酶-4 无法识别原有切割位点。第 34 位赖氨酸换为精氨酸，进一步降低酶解速率。第 26 位赖氨酸经间隔基连接一条含十八个碳的二酸脂肪链，该侧链赋予分子与血浆白蛋白结合的能力。
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.
Quality control relies on pharmacopoeial monographs where they exist, combined with in-house specifications for identity, purity, water content, and counter-ion composition. Reference standards allow calibration across laboratories, although certified materials for every analogue are not universally obtainable. Batch records, chromatograms, and mass spectra form the documentation trail. Regulatory classification varies by jurisdiction and intended use, and research-grade material differs from pharmaceutical-grade material in testing scope. Analytical uncertainty is often expressed as relative standard deviation across replicate injections.
The company that developed the compound filed it as a long-acting analogue, and it gained first approval in 2017 for type 2 diabetes. Later authorisations from several regulators extended the indication to chronic weight management, and the World Health Organization added the glucagon-like peptide-1 receptor agonist drug class to its model list of essential medicines in 2023. Production uses solid-phase peptide synthesis followed by side-chain conjugation and chromatographic purification. Supply constraints and cost differences across regions are well documented. Literature on long-term outcomes continues to grow, with many trials reporting surrogate endpoints rather than hard clinical endpoints.
Semaglutide is a synthetic peptide of thirty-one amino acids that shares roughly ninety-four percent sequence identity with human glucagon-like peptide-1. Two substitutions resist enzymatic cleavage by dipeptidyl peptidase-4, and a fatty diacid side chain attached through a linker promotes binding to serum albumin. That albumin binding slows renal clearance and extends the circulating half-life from minutes to approximately one week. The structural changes are well established in the published literature. Whether the same modifications affect receptor signalling bias in ways that matter clinically remains an open question.
Pharmacological activity arises from agonism at the glucagon-like peptide-1 receptor, a G protein-coupled receptor expressed in the pancreas, the gastrointestinal tract, and the brainstem. Receptor activation raises intracellular cyclic adenosine monophosphate and enhances insulin release in a glucose-dependent manner, an effect that diminishes when blood glucose concentration is low. Other effects include slowed gastric emptying and hypothalamic satiety signalling. These pathways are described well. Receptor desensitisation rates across tissues, relative to the endogenous hormone, are still under investigation, and reported findings differ between laboratories.
== Heparan sulfate analogues == Several Heparan sulfate analogues (also known as ReGeneraTing Agents, RGTA) have been developed from a poly glucose backbone. One named OTR4120 is a 85KD biopolymer and used for topical or ophthalmological application and marketed under the name CACIPLIQ20 or CACICOL20, respectively. Heparan sulfate analogues will occupy the free heparan sulfate binding sites on ECM macromolecules like collagen, fibronectin and laminin that become available following heparan sulfate degradation. In many characteristics heparan sulfate analogues are similar to the natural heparan sulfate. The most important difference is their resistance to enzymatic degradation. The resistance of RGTA is caused by the coupling of the subunits internal bond of the molecules. The β1-4 oxygen-linked binding of the subunits of heparan sulfate is prone to enzymatic cleavage whereas the α1-6 carbon-carbon binding of the subunits of RGTA are resistant to cleavage by all known mammalian glycanases and heparanases. This way RGTA can recreate a scaffold with the ECM proteins and will reposition GFs back into the matrix where they can re-unfold their natural action in wound repair. This way heparan sulfate analogues may contribute to chronic wound healing as will be discussed later on.
Anti-nuclear protests first emerged in the late 1950s and early 1960s. In the United Kingdom, the first Aldermaston March, organised by the Campaign for Nuclear Disarmament, took place in 1958. In 1961, at the height of the Cold War, about 50,000 women brought together by Women Strike for Peace marched in 60 cities in the United States to demonstrate against nuclear weapons. In 1964, Peace Marches in several Australian capital cities featured "Ban the bomb" placards. In the early 1980s, the revival of the nuclear arms race triggered large protests about nuclear weapons. In October 1981 half a million people took to the streets in several cities in Italy, more than 250,000 people protested in Bonn, 250,000 demonstrated in London, and 100,000 marched in Brussels. The largest anti-nuclear protest was held on June 12, 1982, when one million people demonstrated in New York City against nuclear weapons. In October 1983, nearly 3 million people across western Europe protested nuclear missile deployments and demanded an end to the arms race; the largest crowd of almost one million people assembled in the Hague in the Netherlands. In Britain, 400,000 people participated in what was probably the largest demonstration in British history.
The Straw Hats' Jolly Roger was first used by protesters in Indonesia as early as October 2023 in Yogyakarta, during protests against the Gaza genocide. Student protesters in Indonesia begun flying the flag again in February 2025. Truck drivers began flying the Straw Hat Pirates' flag in late July 2025 to protest the prohibition of ODOL (over dimension, overload) trucks throughout several cities in Java, ongoing since 19 June 2025. The flag came into prominence during the 2025 Indonesian anti-government protests which started in the weeks leading up to Independence Day on 17 August. In July, President Prabowo Subianto had called on Indonesians to fly the red and white national flag to celebrate the 80th anniversary of the country's independence. Following the president's speech an apparel store received "thousands of orders" for the Jolly Roger flag, because "The anime reflects the injustice and inequality that Indonesians experience".
=== Autoimmune causes of acquired coagulation disorders === There are autoimmune causes of coagulation disorders. They include acquired antibodies to coagulation factors, termed inhibitors of coagulation. The main inhibitor is directed against clotting factor VIII. Another example is antiphospholipid syndrome, an autoimmune, hypercoagulable state.
== Lysosomal Ca2+-signalling modalities == The ER and acidic Ca2+ stores have similarities as well as key differences. Both transport Ca2+ into their lumina where it is stored, and is subsequently released in response to stimuli by opening resident Ca2+ channels. Indeed, the free [Ca2+] of each is broadly similar (~0.5-1.0 mM). However, they differ in the cohort of transporters, their luminal pH and their total volume per cell. The total amount of Ca2+ that is stored in each is a product of the volume and concentration; since the [Ca2+] is the same for each, the total amount of releasable Ca2+ is directly proportional to the organellar volume and therefore lysosomes can release only a small amount Ca2+ of when compared to the ER. This is important because the maximal Ca2+ release from lysosomes is so small that it is frequently 'invisible' in global Ca2+ recordings e.g. using cytosolic fluorescent reporters. In contrast, ER-derived Ca2+ is globally substantial and the predominant intracellular signal visible in global recordings. If lysosomal Ca2+ release is so small, how then can it affect cellular physiology? The answer is that it can exert its effects in two different signalling modalities: local and global, as shall be described. In bacterial infection, however, NAADP induction of lysosomal Ca2+ efflux and TFEB activation leads to enhanced expression of inflammatory cytokines.
Sources: en.wikipedia.org
== Properties == Agarose is available as a white powder which dissolves in near-boiling water, and forms a gel when it cools. Agarose exhibits the phenomenon of thermal hysteresis in its liquid-to-gel transition, i.e. it gels and melts at different temperatures. The gelling and melting temperatures vary depending on the type of agarose. Standard agaroses derived from Gelidium has a gelling temperature of 34–38 °C (93–100 °F) and a melting temperature of 90–95 °C (194–203 °F), while those derived from Gracilaria, due to its higher methoxy substituents, has a gelling temperature of 40–52 °C (104–126 °F) and melting temperature of 85–90 °C (185–194 °F). The melting and gelling temperatures may be dependent on the concentration of the gel, particularly at low gel concentration of less than 1%. The gelling and melting temperatures are therefore given at a specified agarose concentration. Natural agarose contains uncharged methyl groups and the extent of methylation is directly proportional to the gelling temperature. Synthetic methylation however have the reverse effect, whereby increased methylation lowers the gelling temperature. A variety of chemically modified agaroses with different melting and gelling temperatures are available through chemical modifications. The agarose in the gel forms a meshwork that contains pores, and the size of the pores depends on the concentration of agarose added. On standing, the agarose gels are prone to syneresis (extrusion of water through the gel surface), but the process is slow enough to not interfere with the use of the gel.
Double-knot toxin (DkTx), also known as Tau-theraphotoxin-Hs1a or Tau-TRTX-Hs1a, is a toxin found in the venom of the Chinese Bird spider (Ornithoctonus huwena or Cyriopagopus schmidti), a tarantula species primarily living in the Guangxi province of China. This toxin, characterized by its bivalent structure of two Inhibitor Cysteine Knots (ICK), is thought to induce excruciating and long-lasting pain by activating the transient receptor potential vanilloid 1 (TRPV1) channel.
== Biosynthesis == Pancreatic elastase is formed by activation of proelastase from mammalian pancreas by trypsin. After processing to proelastase, it is stored in the zymogen granules and then activated to elastase in the duodenum by the tryptic cleavage of a peptide bond in the inactive form of the precursor molecule. This process results in the removal of an activation peptide from the N-terminal, that enables the enzyme to adopt its native conformation.
== See also == Substituted methylenedioxyphenethylamine List of investigational hallucinogens and entactogens List of investigational autism and pervasive developmental disorder drugs List of investigational social anxiety disorder drugs
== Expression/Production systems == Different organisms may be used to express a gene's target protein, and the expression vector used will therefore have elements specific for use in the particular organism. The most commonly used organism for protein production is the bacterium Escherichia coli. However, not all proteins can be successfully expressed in E. coli, or be expressed with the correct form of post-translational modifications such as glycosylations, and other systems may therefore be used.
Sources: en.wikipedia.org
== Change of properties with temperature == All materials change with temperature, but superheated water exhibits greater changes than would be expected from temperature considerations alone. Viscosity and surface tension of water drop and diffusivity increases with increasing temperature.
== Targeted protein degradation == In 2001, work from the labs of Craig Crews and Raymond Deshaies described the development of proteolysis-targeting chimeras (PROTACs). Using a small molecule to recruit an E3 ubiquitin ligase to a target protein, this work demonstrated that induced proximity could be used to effect the ubiquitination and proteasomal degradation of a target protein. PROTACs have been frequently applied using the E3 ubiquitin ligases CRBN and VHL to degrade various targets of biological and therapeutic relevance. Multiple groups have sought out additional E3 ligases to co-opt for targeted protein degradation such as FBXO22 and KLHDC2. While PROTACs generally are heterobifunctional compounds linking an E3 ligase binder to a target protein binder, molecular glues also exist that induce protein-protein interactions with E3 ligases, leading to degradation of various substrate proteins. Molecular glues often have been discovered through serendipity, though various methodologies have been explored to expedite the discovery of molecular glues. Biologic modalities for targeted protein degradation have also been explored by fusing E3 ligases to target recognition domains such as nanobodies. These modalities are sometimes referred to as bioPROTACs. While bioPROTACs are advantageous for targeting proteins lacking small molecule ligands, challenges in delivery, pharmacokinetics, and immunogenicity have so far precluded clinical development. Studies exploring different delivery mechanisms have sought to address these shortcomings.
=== Convection === A type of natural convection that can be described by the Navier–Stokes equation is the Rayleigh–Bénard convection. It is one of the most commonly studied convection phenomena because of its analytical and experimental accessibility.
=== Malaysia === Secretary General of the Malaysian United Indigenous Party, Azmin Ali said that the operation "amounted to a unilateral and unlawful use of armed force under international law, in violation of Article 2(4) of the Charter of the United Nations" and called for the Malaysian government to "strengthen the Global South through the Non-Aligned Movement and enhance cross-regional cooperation, while lending support to international accountability mechanisms addressing violations of international law." The chairman of the People's Justice Party's International Affairs Bureau, Maszlee Malik, urged the US to halt all military actions against Venezuela, respect Venezuela's sovereignty and political freedom fully aligned with the Charter of the United Nations and demanded the international community to "preserve peace and prioritize diplomatic solutions through dialogue and multilateral forums".
Physicians began to think of "the pill" as an excellent means of birth control for young women. Stimulants such as Ritalin (methylphenidate) came to be pervasive tools for behavior management and modification in young children. Ritalin was first marketed in 1955 for narcolepsy; its potential users were middle-aged and the elderly. It was not until some time in the 1980s along with hyperactivity in children that Ritalin came onto the market. Medical use of methylphenidate is predominantly for symptoms of attention deficit hyperactivity disorder (ADHD). Consumption of methylphenidate in the U.S. out-paced all other countries between 1991 and 1999. Significant growth in consumption was also evident in Canada, New Zealand, Australia, and Norway. Currently, 85% of the world's methylphenidate is consumed in America. The first minor tranquilizer was meprobamate. Only fourteen months after it was made available, meprobamate had become the country's largest-selling prescription drug. By 1957, meprobamate had become the fastest-growing drug in history. The popularity of meprobamate paved the way for Librium and Valium, two minor tranquilizers that belonged to a new chemical class of drugs called the benzodiazepines. These were drugs that worked chiefly as anti-anxiety agents and muscle relaxants. The first benzodiazepine was Librium. Three months after it was approved, Librium had become the most prescribed tranquilizer in the nation. Three years later, Valium hit the shelves and was ten times more effective as a muscle relaxant and anti-convulsant.
Sources: en.wikipedia.org
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and neutral endopeptidases. Semaglutide carries a non-natural amino acid at position eight that blocks that cleavage, and a fatty diacid side chain that binds albumin. The result is a much longer duration of action than the native hormone.
The fatty diacid chain associates strongly with serum albumin, which keeps the peptide in circulation and shields it from rapid renal clearance. Bound peptide is released gradually, producing a sustained receptor signal. This mechanism also reduces the peak-to-trough variation seen with shorter-acting analogues.
The balance between peripheral receptor activation and signalling in the central nervous system is not fully resolved. The extent to which slowed gastric emptying accounts for reduced energy intake, compared with direct effects on appetite circuits, is debated. Long-term effects on lean mass and on tissues outside the gut and brain are still under study.
Native GLP-1 is degraded within minutes by circulating enzymes. The synthetic version carries substitutions at positions that block enzymatic cleavage, plus a fatty acid side chain that promotes albumin binding. These two changes together extend circulation time from minutes to roughly a week.