Everything below concerns receptor agonist. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-01-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
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。
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.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C187H291N45O59 | 按主链与 C18 二酸侧链计算 |
| 分子量 | 约 4113.6 道尔顿 | 游离碱形式，随反离子略有差异 |
| 外观 | 白色至类白色冻干粉末 | 具吸湿性，需干燥保存 |
| 溶解性 | 微溶于水，易溶于碱性缓冲液 | 溶解性随 pH 升高而改善 |
| 等电点 | 约 5.4 | 影响缓冲液选择与聚集倾向 |
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.
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.
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 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.
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.
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.
=== Physiological === The peripheral actions of oxytocin mainly reflect secretion from the pituitary gland. The behavioral effects of oxytocin are thought to reflect release from centrally projecting oxytocin neurons, different from those that project to the pituitary gland, or that are collaterals from them. Neurons express oxytocin receptors in many parts of the brain and spinal cord, including the amygdala, ventromedial hypothalamus, septum, nucleus accumbens, and brainstem. The distribution differs markedly between species. Furthermore, the distribution of these receptors changes during development and has been observed to change after parturition in the montane vole.
== Limitations == A potential challenge of aquasome-based drug delivery could be toxicity due to burst release of drugs if poorly absorbed on the carbohydrate coat. Aquasomes can also be expensive to formulate, particularly due to their step-by-step synthesis. Careful attention is needed during aquasome production to tune the thickness of each layer, and leaching and aggregation may occur during prolonged storage of aquasomes. A physiological challenge aquasomes present is that upon their entry into the bloodstream, they may be taken up nonspecifically, leading to opsonization and phagocytic clearance by the immune system. To prevent this, aquasome surfaces can be coated with polyethylene glycol (PEG) to block opsonin binding through steric hindrance; however, the effect of PEGylation on aquasome drug release has not been sufficiently explored to enable clinical applications. Polymer degradation in different physiological environments can change the stability and drug loading of aquasomes over time, as their surface properties directly impact drug release. Aquasomes may also be challenging to scale up and prepare as it is difficult to ensure consistent formulation quality. More research is needed to demonstrate both the efficiency and safety of aquasomes in clinical use.
==== Monazite identification and mapping ==== Monazite grains are identified by a backscattered electron imaging survey or/and electron microprobe analysis (EMPA) by mapping the concentration of distinctive Ce in monazite. The two images are usually superimposed to reflect sample texture and monazite locations at the same time.
In 1979, the toppling of US-allied governments in Iran and Nicaragua and the outbreak of the Soviet–Afghan War again raised tensions. In 1985, Mikhail Gorbachev became leader of the USSR and expanded political freedoms, which contributed to the revolutions of 1989 in the Eastern Bloc and the collapse of the USSR in 1991, ending the Cold War.
Sources: en.wikipedia.org
Gilbert's syndrome (GS) is a syndrome in which the liver of affected individuals processes bilirubin more slowly than the majority, resulting in higher levels in the blood. Many people never have symptoms. Occasionally jaundice (a yellowing of the skin or whites of the eyes) may occur. Gilbert syndrome is due to a genetic variant in the UGT1A1 gene, which results in decreased activity of the bilirubin uridine diphosphate glucuronosyltransferase (UGT1A1) enzyme. It is typically inherited in an autosomal recessive pattern and occasionally in an autosomal dominant pattern depending on the type of variant. Episodes of jaundice may be triggered by stress such as exercise, menstruation, or not eating. Diagnosis is based on elevated levels of unconjugated bilirubin in the blood without signs of liver problems or red blood cell breakdown. Typically, no treatment is needed. Phenobarbital aids in the conjugation of bilirubin and can be prescribed if jaundice becomes significant. Gilbert syndrome is associated with decreased cardiovascular health risks but increased risks of some cancers and gallstones. Gilbert syndrome affects about 5% of people in the United States. Males are more often diagnosed than females. It is often not noticed until late childhood to early adulthood. The condition was first described in 1901 by Augustin Nicolas Gilbert.
=== Toffee === Toffee is a free lossless file format for data-independent acquisition mass spectrometry that leverages HDF5 and aims to achieve file sizes similar to those seen in proprietary/vendor-bound formats.
Metribolone, also known as 17α-methyltrenbolone, as well as 17α-methyl-δ9,11-19-nortestosterone or 17α-methylestra-4,9,11-trien-17β-ol-3-one, is a synthetic estrane steroid and a 17α-alkylated derivative of nandrolone (19-nortestosterone). It is the C17α methylated derivative of trenbolone (δ9,11-19-nortestosterone) and the C9- and C11-dehydrogenated (δ9,11) analogue of normethandrone (17α-methyl-19-nortestosterone). Other close relatives and derivatives of metribolone include mibolerone (7α,17α-dimethyl-19-nortestosterone) and dimethyltrienolone (RU-2420; 7α,17α-dimethyl-δ9,11-19-nortestosterone). In addition to AAS, trimethyltrienolone (R2956; 2α,2β,17α-trimethyl-δ9,11-19-nortestosterone), a highly potent antiandrogen, has been derived from metribolone.
Sources: en.wikipedia.org
Questions in computational neuroscience can span a wide range of levels of traditional analysis, such as development, structure, and cognitive functions of the brain. Research in this field utilizes mathematical models, theoretical analysis, and computer simulation to describe and verify biologically plausible neurons and nervous systems. For example, biological neuron models are mathematical descriptions of spiking neurons which can be used to describe both the behavior of single neurons as well as the dynamics of neural networks. Computational neuroscience is often referred to as theoretical neuroscience.
The mechanism of transport for importers supports the alternating-access model. The resting state of importers is inward-facing, where the nucleotide binding domain (NBD) dimer interface is held open by the TMDs and facing outward but occluded from the cytoplasm. Upon docking of the closed, substrate-loaded binding protein towards the periplasmic side of the transmembrane domains, ATP binds and the NBD dimer closes. This switches the resting state of transporter into an outward-facing conformation, in which the TMDs have reoriented to receive substrate from the binding protein. After hydrolysis of ATP, the NBD dimer opens and substrate is released into the cytoplasm. Release of ADP and Pi reverts the transporter into its resting state. The only inconsistency of this mechanism to the ATP-switch model is that the conformation in its resting, nucleotide-free state is different from the expected outward-facing conformation. Although that is the case, the key point is that the NBD does not dimerize unless ATP and binding protein is bound to the transporter.
Upregulation of receptors is the increase in receptor number or sensitivity of receptors. The receptors involved in functional antagonism are regulated in sensitivity, number and location. Therefore, changes in receptors are common. Using a long-term antagonist drug or continuous exposure to an antagonist may cause the upregulation and hypersensitivity of receptors, which means an increase in the number and sensitivity of receptors. The increase in the number of receptors is due to the increased expression of receptors after prolonged inhibition. The upregulation of receptors is important in the clinical aspect. One example of upregulation of receptors is the upregulation of β-receptors caused by β receptor antagonists (also called β-blocker). The prolonged use of β-blockers results in the blockade of β-receptors, causing cells (mainly myocardial cells) to increase their expression of β-receptor. After removing the blockage, more receptors available for stimulation, resulting in higher sensitivity of β-receptors called the hypersensitivity of β-receptors. Abrupt discontinuation of β-blocker may potentially aggravate coronary artery disease, tachycardia, or even sudden cardiac death. Therefore, to prevent the adverse effects, doses of β-blocker must be reduced gradually over 10–14 days.
Sources: en.wikipedia.org
差别集中在三处：第 8 位残基被非天然氨基酸取代，第 34 位换成精氨酸，第 26 位增加一条脂肪酸侧链。前两处改动降低酶解速率，侧链则通过白蛋白结合延长循环时间。综合结果是半衰期从约两分钟延长到约一周。
胰岛素释放需要细胞内环腺苷酸与钙信号升高，同时依赖葡萄糖代谢产生的协同信号。血糖水平较低时协同信号不足，分泌增强有限。这一机制在降糖效果与低血糖风险之间提供了缓冲。
白蛋白结合是主要原因，它减少肾小球滤过并保护分子免受蛋白酶降解。序列修饰带来的酶解抵抗同样不可忽略，二者共同作用。脂肪链的疏水性还会影响组织分布，但其对总半衰期的贡献程度仍在研究之中。
It is a glucagon-like peptide-1 receptor agonist, often grouped with the incretin mimetics. Its backbone is modified from the human hormone to resist enzymatic degradation and to bind albumin. These two features distinguish it from the native peptide.