fatty diacid chain raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-12-03 and is reviewed periodically as new material appears.
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.
Lyophilized semaglutide is typically stored at temperatures between minus 20 and minus 80 degrees Celsius for long-term preservation. Short-term storage at 2 to 8 degrees Celsius is common for working aliquots. Repeated freeze-thaw cycles can degrade the peptide and are usually avoided. The molecule is hygroscopic in its solid form, so containers should remain sealed with desiccant. Solutions are less stable than powders and are generally prepared fresh. Light exposure is limited because aromatic residues can undergo photo-oxidation.
Semaglutide dissolves readily in water and in aqueous buffers near neutral pH. Solubility decreases near the isoelectric point, where net charge is minimal. Common laboratory solvents include phosphate-buffered saline and dilute ammonium bicarbonate. Strongly acidic or basic conditions may accelerate hydrolysis. Working concentrations are usually prepared by diluting a concentrated stock. Vial surfaces can adsorb small amounts of peptide at low concentrations, so carrier proteins or low-binding tubes are sometimes used.
| 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 |
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.
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.
该分子作为 GLP-1 受体的选择性激动剂发挥作用，受体属于 B 类 G 蛋白偶联受体家族，激活后经 Gs 通路提升细胞内环腺苷酸水平。在胰腺 β 细胞，信号促进葡萄糖依赖性的胰岛素释放，血糖偏低时该作用明显减弱。在胰岛 α 细胞，胰高血糖素分泌受到抑制。中枢神经系统与胃肠道同样存在受体表达，相应信号参与食欲调节以及胃排空速率的降低。
皮下注射后吸收相对缓慢，绝对生物利用度约为百分之八十九，血药浓度峰值通常出现在给药后一到三天。与白蛋白结合使清除减慢，终末半衰期约为一百六十五小时，接近一周。连续给药约四到五周后达到稳态暴露水平。表观分布容积约为每千克零点二五升，血浆蛋白结合率超过百分之九十九。代谢以蛋白水解切割和脂肪二酸侧链的 β-氧化为主，相关产物主要经尿液与粪便排出。
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。
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.
Grapefruit-juice–mediated inhibition of an enzyme that metabolizes the drug to an inactive metabolite leads to excessive levels of the drug in the body. Grapefruit-juice–mediated inhibition either of a membrane transport protein that helps move substances from the intestine to the blood or of an enzyme that converts a prodrug to an active metabolite leads to insufficient levels of the drug in the body resulting in loss of theurapeutic effect. Grapefruit or grapefruit juice can reduce the absorption of many drugs by inhibiting transport across cell membranes by the transporters P-glycoprotein (a member of the superfamily of ATP-binding cassette (ABC) transporters) and members of the organo anion transporter family. These transporters appear to have a minimal effect on systemic exposure of the drugs they affect, however. Many drugs are affected by consumption of citrus juice. When the metabolizing enzyme is inhibited, less of the drug will be metabolized by it in the epithelial cells. This interaction is particularly dangerous when the drug in question has a low therapeutic index, so that a small increase in blood concentration can be the difference between therapeutic effect and toxicity. Citrus juice inhibits the enzyme only within the intestines if consumed in small amounts. When larger amounts are consumed they may in addition inhibit the enzyme in the liver. The hepatic enzyme inhibition may cause an additional increase in potency and a prolonged metabolic half-life (prolonged metabolic half-life for all ways of drug administration).
Because the use of broad-spectrum antibiotics encourages the spread of multidrug-resistant strains and the development of Clostridioides difficile infections, treatment guidelines often recommend minimizing the use of fluoroquinolones and other broad-spectrum antibiotics in less severe infections and in those in which risk factors for multidrug resistance are not present. It has been recommended that fluoroquinolones not be used as a first-line agent for community-acquired pneumonia, instead recommending macrolide or doxycycline as first-line agents. The Drug-Resistant Streptococcus pneumoniae Working Group recommends fluoroquinolones be used for the ambulatory treatment of community-acquired pneumonia only after other antibiotic classes have been tried and failed, or in cases with demonstrated drug-resistant Streptococcus pneumoniae. Resistance to quinolones can evolve rapidly, even during a course of treatment. Numerous pathogens, including Escherichia coli, commonly exhibit resistance. Widespread veterinary usage of quinolones, in particular in Europe, has been implicated. Fluoroquinolones had become the class of antibiotics most commonly prescribed to adults in 2002. Nearly half (42%) of these prescriptions were for conditions not approved by the U.S. FDA, such as acute bronchitis, otitis media, and acute upper respiratory tract infection, according to a study supported in part by the Agency for Healthcare Research and Quality.
=== Alcohol use === Lifestyle factors, such as substance use or adiposity, can play a detrimental role in the quality of the semen. One study examining the consequences of alcohol consumption and its effect on semen quality concluded that alcohol intake can lead to a negative effect on semen volume in daily alcohol consumers. However, occasional or moderate use of alcohol was observed to not have an adverse effect on the semen.
Sources: en.wikipedia.org
Many animals can learn behaviours by imitation, but ants may be the only group apart from mammals where interactive teaching has been observed. A knowledgeable forager of Temnothorax albipennis can lead a naïve nest-mate to newly discovered food by the process of tandem running. The follower obtains knowledge through its leading tutor. The leader is acutely sensitive to the progress of the follower and slows down when the follower lags and speeds up when the follower gets too close. Controlled experiments with colonies of Cerapachys biroi suggest that an individual may choose nest roles based on her previous experience. An entire generation of identical workers was divided into two groups whose outcome in food foraging was controlled. One group was continually rewarded with prey, while it was made certain that the other failed. As a result, members of the successful group intensified their foraging attempts while the unsuccessful group ventured out fewer and fewer times. A month later, the successful foragers continued in their role while the others had moved to specialise in brood care.
Due to the legal and military tensions, the Hungarian parliament did not grant Franz Joseph that favour. Francis Joseph was, in the strict constitutional sense, a textbook usurper in Hungary: under the Pragmatic Sanction of 1723 (Arts. I–III) and the established Hungarian constitutional law governing succession and coronation, the throne was not vacant while the crowned King Ferdinand V was still alive, and Ferdinand’s unilateral abdication could not by itself make Francis Joseph King of Hungary; without the consent of the Hungarian Diet, the constitutional oath, and coronation with the Holy Crown, Francis Joseph had no lawful authority to exercise the Hungarian royal power—his seizure of that power thus constituting a clear case of usurpation. In short: Francis Joseph was regarded by Hungarians as a usurper and a rebel against the ancient constitution and the established order.
=== Foundations of modern chemistry === In 1774, Antoine Lavoisier used the reaction of water steam with metallic iron inside an incandescent iron tube to produce hydrogen in his experiments leading to the demonstration of the conservation of mass, which was instrumental in changing chemistry from a qualitative science to a quantitative one.
Beta-adrenergic receptors (β1, β2, β3) stimulate lipolysis through Gs-protein-coupled activation of adenylyl cyclase and subsequent cAMP production, while alpha-2 adrenergic receptors (α2A) inhibit lipolysis through Gi-protein-mediated suppression of adenylyl cyclase. Subcutaneous abdominal adipose tissue exhibits a higher α2:β ratio compared to visceral adipose tissue, which is predominantly β3-receptor-expressing and more lipolytically responsive to catecholamine stimulation.
Sources: en.wikipedia.org
=== Television === Phang has guest-directed on episodic series television, including for The Boys, Cloak & Dagger, Quantico, The Expanse, Riverdale, Major Crimes, The Exorcist, Proven Innocent, Stargirl and Resident Alien. She remarks that it is interesting to work in an established universe with characters already defined, and to direct a wide variety of actors who are already familiar with their characters. In her opinion, TV directing work, in addition to the extra income, improves her versatility and adaptability in her film projects.
The olive trade in southern Lebanon, which is the main source of income for many, was halted as farmers stopped their harvests in fear of the active shelling. According to Agriculture Minister Abbas Hajj Hassan, 40,000 olive trees have been burned down by fires caused by IDF shelling. The ministry has also said that 790 hectares of agricultural land have been damaged and 340 thousand farm animals have been lost. In total, the IDF has caused US$3 billion of agriculture losses. The Institute of International Finance predicted that Lebanon's GDP could decline by one percent by the end of 2023 and by 30 percent in 2024 in the event of further spillover of the war. According to the Council for the South, Israeli strikes have destroyed 1,700 buildings and damaged 14,000 others and caused US$500 million worth of damage on water, electricity, telecoms and other infrastructure.
Meitnerium has no stable or naturally occurring isotopes. Several radioisotopes have been synthesized in the laboratory, either by fusing two atoms or from the decay of heavier elements. Eight isotopes of meitnerium have been reported with mass numbers 266, 268, 270, and 274–278, two of which, 268Mt and 270Mt, have unconfirmed metastable states. A ninth isotope, 282Mt, is unconfirmed. Most of these decay by alpha emission, though some undergo spontaneous fission.
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.
Long-term storage is usually at minus 20 to minus 80 degrees Celsius in a sealed, desiccated container. Working aliquots can be held briefly at 2 to 8 degrees Celsius.