Everything below concerns albumin binding. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-07-25. Numbers and descriptions here follow the published literature rather than marketing material.
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。
Lyophilised material appears as a white to off-white cake or powder that is hygroscopic, and containers are usually equilibrated to room temperature before opening to limit condensation. Dissolution is performed in water, phosphate-buffered saline, or a mildly alkaline buffer, since solubility rises above neutral pH. Gentle inversion or low-speed mixing is preferred, because vigorous vortexing can promote surface denaturation and aggregation. Complete dissolution may require several minutes, and brief sonication is sometimes applied. Passing the solution through a 0.22 micrometre membrane removes particulates but does not by itself sterilise the liquid.
Storage at minus 20 degrees Celsius or lower in a desiccated container preserves the peptide for extended periods, while working solutions are commonly held at two to eight degrees Celsius for short intervals. Light exposure and repeated freeze-thaw cycles accelerate degradation, so dividing material into single-use aliquots is generally recommended. Adsorption to glass and plastic surfaces can lower the measured concentration of dilute solutions, particularly below one milligram per millilitre. The degradation routes most often reported for GLP-1 analogues are deamidation, methionine oxidation, and backbone hydrolysis. Relative rates under specific conditions are frequently described only for individual formulations.
| 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 |
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.
Semaglutide belongs to the glucagon-like peptide-1 receptor agonist class, a group of synthetic peptides that imitate an incretin hormone released by intestinal L cells after food intake. Native GLP-1 circulates for only a few minutes because dipeptidyl peptidase-4 cleaves it rapidly. The hormone acts on pancreatic islets, the gastrointestinal tract, and several brain regions. Because the natural peptide is short-lived, development work concentrated on analogues that keep receptor activity while resisting enzymatic breakdown and renal clearance.
The semaglutide sequence is a 31-residue analogue of human GLP-1, altered at three positions relative to the parent hormone. Aminoisobutyric acid replaces alanine at position 8, arginine replaces lysine at position 34, and a lipophilic diacid is attached to lysine 26 through a short linker. These features are reported consistently in the structural literature. The position 8 substitution blocks recognition by dipeptidyl peptidase-4, while the attached chain drives strong, reversible association with a carrier protein in blood.
Receptor activation raises intracellular cyclic AMP through Gs coupling, which promotes glucose-dependent insulin release and suppresses glucagon secretion when blood glucose is elevated. Effects outside the pancreas include slower gastric emptying and altered appetite signalling in the hypothalamus and hindbrain. The relative contribution of each tissue to overall metabolic outcomes remains an area of active investigation. Central mechanisms in particular are inferred mainly from animal models and indirect human measures rather than direct observation.
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.
Reverse-phase high-performance liquid chromatography is the standard method for purity assessment, separating the peptide from truncated or oxidized variants. Mass spectrometry confirms molecular mass and detects modifications, while ultraviolet absorbance near 280 nanometers supports concentration measurement through tryptophan and tyrosine residues. Circular dichroism can indicate secondary structure, though the peptide is largely helical in solution, and ion-exchange chromatography resolves charge variants. Purity values above 95 percent are typical for research-grade material. Stability studies track degradation over time under defined conditions.
Jal, Auguste (1867). Dictionnaire critique de biographie et d'histoire [Critical Dictionary of Biography and History] (in French). Éditions Plon. Piot, Eugène (1873). État civil de quelques artistes français [Marital status of some French artists] (in French). Paris: Librairie Pagnerre. de Brossard, Yolande (1965). Musiciens de Paris 1535-1792 [Musicians of Paris 1535-1792] (in French). Paris: Picard.
methylglyoxalase, aldoketomutase, ketone-aldehyde mutase, and (R)-S-lactoylglutathione methylglyoxal-lyase (isomerizing). In some instances, the glutathionyl moiety may be supplied by trypanothione, the analog of glutathione in parasitic protozoa such as the trypanosomes. The human gene for this enzyme is called GLO1.
Maintenance chemotherapy is a repeated low-dose treatment to prolong remission. Salvage chemotherapy or palliative chemotherapy is given without curative intent, but simply to decrease tumor load and increase life expectancy. For these regimens, in general, a better toxicity profile is expected. All chemotherapy regimens require that the recipient be capable of undergoing the treatment. Performance status is often used as a measure to determine whether a person can receive chemotherapy, or whether dose reduction is required. Because only a fraction of the cells in a tumor die with each treatment (fractional kill), repeated doses must be administered to continue to reduce the size of the tumor. Current chemotherapy regimens apply drug treatment in cycles, with the frequency and duration of treatments limited by toxicity.
Sources: en.wikipedia.org
=== Paleomagnetic dating === A sequence of paleomagnetic poles (usually called virtual geomagnetic poles), which are already well defined in age, constitutes an apparent polar wander path (APWP). Such a path is constructed for a large continental block. APWPs for different continents can be used as a reference for newly obtained poles for the rocks with unknown age. For paleomagnetic dating, it is suggested to use the APWP in order to date a pole obtained from rocks or sediments of unknown age by linking the paleopole to the nearest point on the APWP. Two methods of paleomagnetic dating have been suggested: (1) the angular method and (2) the rotation method. The first method is used for paleomagnetic dating of rocks inside of the same continental block. The second method is used for the folded areas where tectonic rotations are possible.
=== Insects as a novel protein source for pet food === A challenge that is presented when feeding companion animals with food intolerance or sensitivities is finding protein sources that will not irritate their gastrointestinal tracts. Animal protein is a major cause of gastrointestinal problems, and insect protein may be an alternative source for these pets. Insects have the potential to be used as a novel protein in diets for sensitive animals. A novel protein is a protein source to which the animal has not previously been exposed. There are some risks to using novel protein sources, such as contaminants, antinutritional factors (ANFs), and allergens which are not well known. When referring specifically to dog and cat nutrition, the use of alternative protein sources must be able to deliver the ten essential amino acids (EAA) that are not synthesized from the body (including Arg, His, Ile, Leu, Lys, Met, Phe, Thr, Trp and Val). One additional amino acid which is specific to cats who are obligate carnivores by nature is taurine. This requirement is based on the low enzymatic action of cysteine dioxygenase and cysteine sulphinic acid decarboxylase within feline metabolism, where the competing pathway of pyruvate for an energy source overrides taurine synthesis. McCuster et al. created a study to identify amino acid composition of different insects, specifically addressing the presence of taurine in comparison to the National Research Council's (NRC) minimal requirements (MR) for the dog and cat.
The previous life: the first two nidanas, namely ignorance and mental fabrications. They are basis for the events in the present. Nyanatiloka, writing from a traditional Theravada perspective, calls these "karma process" (kamma-bhava). The present life: The third to the tenth nidanas (consciousness, nama-rupa, the sense bases, contact, feeling, craving, clinging, becoming) relate to the present life. This begins with the descent of vijnana (consciousness, perception) into the womb. Nyanatiloka notes that nidanas 3-7 are part of the "rebirth process" (uppatti-bhava) and nidanas are 8-10 are "karma process". The future life: The last two nidanas (birth, old age and death) represent the future lives conditioned by the present causes. Nyanatiloka states these last two nidanas are a "rebirth process". Bhikkhu Bodhi notes that this distribution of the 12 nidanas into three lives "is an expository device employed for the purpose of exhibiting the inner dynamics of the round. It should not be read as implying hard and fast divisions, for in lived experience the factors are always intertwined." Furthermore, Bodhi argues that these twelve causes are not something hidden, but are "the fundamental pattern of experience" which "always present, always potentially accessible to our awareness." Nagarjuna's Pratityasamutpada-hrdaya-karika also outlines the 12 nidanas as a rebirth process.
=== Pharmacodynamics === Clonidine produces most of its pharmacodynamic effects by acting as a non-selective partial agonist at α2 adrenoceptors (α2A, α2B, and α2C), where it can mimic the actions of endogenous norepinephrine at these receptors in the central nervous system and the sympathetic nervous system. Clonidine can also bind imidazoline I1 receptors in brainstem regions involved in cardiovascular responses. Through these actions clonidine lowers arterial blood pressure, heart rate, and total peripheral resistance. α2 adrenoceptor activation decreases noradrenergic arousal signaling in the ascending reticular activating system, can modify prefrontal cortical network activity relevant to attention, and suppresses nociceptive signaling in the dorsal horn of the spinal cord. α2 adrenoceptors are Gi/Go-coupled G protein-coupled receptors that signal through heterotrimeric G proteins made up of a Gαi/o subunit protein and a paired Gβγ subunit complex (i.e., the β and γ subunits). After receptor activation, Gαi/o and Gβγ can separate, and both components contribute to inhibition of neuronal activity and neurotransmitter release. Gαi/o inhibits adenylyl cyclase, which decreases the expression of cyclic adenosine monophosphate (cAMP) and ceases protein kinase A (PKA)-dependent phosphorylation of amino acid residues involved in neuronal excitability and synaptic signaling. In parallel, Gβγ can increase K+ conductance through G protein-coupled inwardly rectifying potassium channels (GIRKs), an effect that reduces neuronal firing through membrane hyperpolarization.
Sources: en.wikipedia.org
Alkyl amines characteristically feature tetrahedral nitrogen centers. C-N-C and C-N-H angles are near 109°. C-N distances are slightly shorter than C-C distances. The energy barrier for the nitrogen inversion of the stereocenter is about 7 kcal/mol for a trialkylamine. The interconversion has been compared to the inversion of an open umbrella into a strong wind. Amines of the type NHRR' and NRR′R″ are chiral: the nitrogen center bears four substituents counting the lone pair. Because of the low barrier to inversion, amines of the type NHRR' cannot be obtained in optical purity. For chiral tertiary amines, NRR′R″ can only be resolved when the R, R', and R″ groups are constrained in cyclic structures such as N-substituted aziridines (quaternary ammonium salts are resolvable).
While acknowledging the Marxist influence on Gaddafi's thought, Bearman stated that the Libyan leader rejected Marxism's core tenet, that of class struggle as the main engine of social development. Instead of embracing the Marxist idea that a socialist society emerged from class struggle between the proletariat and bourgeoisie, Gaddafi believed that socialism would be achieved through overturning "unnatural" capitalism and returning society to its "natural equilibrium". In this, he sought to replace a capitalist economy with one based on his own romanticized ideas of a traditional, pre-capitalist past. This owed much to the Islamic belief in God's natural law providing order to the universe.
Multi/minicore myopathy is a congenital myopathy usually caused by mutations in either the SELENON and RYR1 genes. It is characterised the presence of multifocal, well-circumscribed areas with reduction of oxidative staining and low myofibrillar ATPase on muscle biopsy. It is also known as Minicore myopathy, Multicore myopathy, Multiminicore myopathy, Minicore myopathy with external ophthalmoplegia, Multicore myopathy with external ophthalmoplegia and Multiminicore disease with external ophthalmoplegia.
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。
Filtering removes particulate matter that can block columns or scatter light. A 0.22 micrometre membrane is typical, and the filter material should be checked for peptide adsorption.