Everything below concerns acylated peptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-10-22. Numbers and descriptions here follow the published literature rather than marketing material.
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。
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。
Solid peptide material is generally kept at reduced temperature to limit degradation. Short-term storage at 2 to 8 degrees Celsius is common, while longer archival storage at minus 20 degrees Celsius or below is typical for lyophilised powder. Vials should remain sealed and protected from light, because ultraviolet exposure can oxidise susceptible residues. Repeated freeze-thaw cycles are avoided, as they promote aggregation and loss of soluble material. Solutions are less stable than solids and are usually prepared close to the time of use.
Reversed-phase high-performance liquid chromatography is widely used to assess purity and to separate the parent peptide from related substances. Mass spectrometry confirms identity and can resolve modifications that differ by a few daltons. Size-exclusion chromatography detects dimers and higher aggregates, which are relevant to both stability and immunogenicity questions. Peptide mapping with enzymatic digestion locates specific modifications along the sequence. Circular dichroism provides a secondary-structure profile, although it gives limited information about local conformational changes.
| 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 |
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.
As a peptide, semaglutide is sensitive to conditions that break amide bonds or modify side chains. Deamidation of asparagine and glutamine residues, oxidation of methionine and tryptophan, and non-covalent aggregation are the main degradation routes described in published stability work. Rate depends strongly on pH, buffer species, ionic strength, temperature and exposure to light. Formulators therefore choose a defined solution pH and often add excipients such as phosphate buffer, propylene glycol and phenol, each of which plays a separate role in pH control, tonicity or preservation.
Storage guidance for the finished injectable product distinguishes the unused state from the in-use state. Before first use, pens are kept refrigerated between 2 and 8 degrees Celsius, protected from light, and never frozen, since freezing can disrupt the peptide or the device. After first use, label instructions in several markets permit storage at room temperature up to about 30 degrees Celsius for a limited number of days. Solid research-grade material is normally held at or below minus 20 degrees Celsius, often with desiccant, and allowed to equilibrate before opening.
Quantification and purity assessment rely on separation methods coupled to optical or mass detection. Reversed-phase high-performance liquid chromatography resolves the intact peptide from related impurities and is the standard assay technique. Size-exclusion chromatography measures aggregates, while ion-exchange chromatography separates charge variants produced by deamidation. Mass spectrometry confirms identity and detects mass shifts of a few daltons. In biological matrices, liquid chromatography with tandem mass spectrometry is often used because immunoassays can cross-react with endogenous GLP-1 or with circulating fragments.
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.
In early April, Sykes and Picot were appointed to act as the chief negotiators once more, this time on a month-long mission to the Middle East for further discussions with the Sherif of Mecca and other Arab leaders. On 3 April 1917, Sykes met with Lloyd George, Lord Curzon and Maurice Hankey to receive his instructions in this regard, namely to keep the French onside while "not prejudicing the Zionist movement and the possibility of its development under British auspices, [and not] enter into any political pledges to the Arabs, and particularly none in regard to Palestine". Before travelling to the Middle East, Picot, via Sykes, invited Nahum Sokolow to Paris to educate the French government on Zionism. Sykes, who had prepared the way in correspondence with Picot, arrived a few days after Sokolow; in the meantime, Sokolow had met Picot and other French officials, and convinced the French Foreign Office to accept for study a statement of Zionist aims "in regard to facilities of colonization, communal autonomy, rights of language and establishment of a Jewish chartered company." Sykes went on ahead to Italy and had meetings with the British ambassador and British Vatican representative to prepare the way for Sokolow once again. Sokolow was granted an audience with Pope Benedict XV on 6 May 1917. Sokolow's notes of the meeting – the only meeting records known to historians – stated that the Pope expressed general sympathy and support for the Zionist project.
In Taiwan, TCM practitioners are physicians and are regulated by the Physicians Act. They possess the authority to independently diagnose medical conditions, issue prescriptions, dispense Traditional Chinese Medicine, and prescribe a variety of diagnostic tests including X-rays, ECG, and blood and urine test. Under current law, those who wish to qualify for the Chinese medicine exam must have obtained a 7-year university degree in TCM. The National Research Institute of Chinese Medicine, established in 1963, is the largest Chinese herbal medicine research center in Taiwan.
Latin and Greek were the primary languages of the late Roman Empire, with the former prevalent in the west and the latter in the east. Although Latin was historically important in the military, legal system, and government, its use declined in Byzantine territories from 400 AD. Greek had begun to replace it even in those functions by the time of Justinian I (r. 527–565), who may have tried to arrest Latin's decline. Its extinction in the east was thereafter inevitable. A similar process of linguistic Hellenization occurred in Asia Minor, whose inhabitants had mostly abandoned their indigenous languages for Greek by early Byzantine times. Still, much of the population of the early empire would have known neither Latin nor Greek, especially in rural areas—their languages included Armenian in Byzantine Armenia, Aramaic dialects such as Syriac in Mesopotamia and the Levant, Coptic in Egypt, Phoenician on the Levant coast and in Carthage, and Berber in rural North Africa. By the mid-6th century, Geoffrey Horrocks estimates that Greek was the native language of about one-third of the population, while it was spoken by 80% of the aristocracy. The empire lost its linguistic diversity in the wars of the 7th and 8th centuries, becoming overwhelmingly Greek-speaking. During this troubled period, classical Attic Greek—one of the linguistic registers the Byzantine Greeks inherited—fell out of use, while the everyday vernacular registers were still used.
Sources: en.wikipedia.org
Adrenodoxin reductase that is involved in steroid hormone synthesis in vertebrate species, and has a ubiquitous distribution in metazoa and prokaryotes Cytochrome P450 reductase that is a redox partner of cytochrome P450 proteins located in endoplasmic reticulum Epidermin biosynthesis protein, EpiD, which has been shown to be a flavoprotein that binds FMN. This enzyme catalyses the removal of two reducing equivalents from the cysteine residue of the C-terminal meso-lanthionine of epidermin to form a --C==C-- double bond The B chain of dipicolinate synthase, an enzyme which catalyses the formation of dipicolinic acid from dihydroxydipicolinic acid Phenylacrylic acid decarboxylase (EC 4.1.1.102), an enzyme which confers resistance to cinnamic acid in yeast Phototropin and cryptochrome, light-sensing proteins Flavodiirion Proteins, enzymes which also possess an diiron site and catalyze redox reactions in oxidative stress defence
side chain A chemical substituent group that is attached to the core part or "backbone" of a larger molecule, especially an oligomeric or polymeric hydrocarbon chain that branches off of the longer primary chain of a macromolecule. The term is most commonly encountered in biochemistry and organic chemistry.
== Function == TIG1's specific functions are still being elucidated. Latexin is a structurally similar protein to TIG1. Latexin is the only mammalian carboxypeptidase inhibitor, although TIG1's proteolytic activity remains unexplored. Using a selective subtractive differential gene display, Jing and colleagues discovered that TIG1 expression was absent from malignant prostate carcinoma cell lines but present in benign tumor lines. When highly malignant prostate cancer cells were transfected with TIG1, decreased in vitro invasiveness was measured using an extracellular matrix migration assay over a period of 48 hours. This same group of scientists performed another experiment in which TIG1 expression was restored in mice that were homozygous for the deletion of the TIG1 gene. Although the restoration of TIG1 did not prevent tumor growth in these mice, the average size of the tumors showed a 2.4-fold decrease (Jing et al., 2006).
== History == The first benchtop detector was introduced in 2014 with detection capabilities between 120 and 240 nm. This portion of the ultraviolet spectrum had historically been restricted to bright source synchrotron facilities due to significant background absorption challenges inherent to working within the wavelength range. Further detector platform development has extended the wavelength detection range out from 120 to 430 nm.
Sources: en.wikipedia.org
Blood sugar levels are regulated by negative feedback in order to keep the body in balance. The levels of glucose in the blood are monitored by many tissues, but the cells in the pancreatic islets are among the most well understood and important. Granule docking is an important glucose-dependent step in human insulin secretion that does not work properly in type 2 diabetes.
Human placental lactogen (hPL), also called human chorionic somatomammotropin (hCS) or human chorionic somatotropin, is a polypeptide placental hormone, the human form of placental lactogen (chorionic somatomammotropin). Its structure and function are similar to those of human growth hormone. It modifies the metabolic state of the mother during pregnancy to facilitate energy supply to the fetus. hPL has anti-insulin properties. hPL is a hormone secreted by the syncytiotrophoblast during pregnancy. Like human growth hormone, hPL is encoded by genes on chromosome 17q22-24. It was identified in 1963. Its two forms are encoded by the genes CSH1 and CSH2 and differ only by a single amino acid.
=== ThermoFluor of membrane proteins === Membrane proteins are often isolated in the presence of hydrophobic solubilizing agents that can partition hydrophobic-binding dyes like 1,8-ANS and SYPRO orange and generate a fluorescence background that obscures observation of a Thermofluor protein melting signal. Nevertheless, careful optimization of conditions (e.g., to avoid micelle formation of the solubilizing agent) can often produce satisfactory assay conditions
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。
Lower temperatures slow hydrolysis, oxidation and aggregation reactions that degrade the molecule over time. Lyophilised powder is more tolerant than solution, but both benefit from controlled conditions.