A practical reference on 二肽基肽酶-4: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-02-12 and is reviewed periodically as new material appears.
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 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.
| 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 |
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.
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.
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.
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.
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.
Stability studies examine how temperature, pH, and moisture influence degradation rates over time. In aqueous solution, hydrolysis and deamidation accelerate as pH moves away from mildly acidic conditions. Light exposure and residual metal ions can also trigger oxidation of susceptible residues. Accelerated aging at elevated temperature is used to estimate shelf life, though extrapolation to room temperature carries uncertainty because individual degradation pathways do not always scale predictably.
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.
The UPMC Hillman Cancer Center, formerly titled the University of Pittsburgh Cancer Institute, is a National Cancer Institute designated cancer center and the flagship of the UPMC Cancer Centers network. Founded in 1985 at the University of Pittsburgh, the center is located in the Shadyside neighborhood of Pittsburgh and is connected to UPMC Shadyside via a pedestrian bridge.
Livestock are not usually given opioids due to a stand down period where an animal cannot be used for milking or slaughter following administration and strict regulations that require precise record keeping on administration of opioids.
where Fi is blood flow (noted Q in the Figure above), Cart incoming arterial blood concentration, Pi the tissue over blood partition coefficient and Vi the volume of compartment i. A complete set of differential equations for the 7-compartment model shown above could therefore be given by the following table:
Mathematicians believe that it may lead to advances in science and technology. Astronomers confirm that Jupiter's Great Red Spot is wobbling and fluctuating in size after observing its time-lapse video made from the images captured by the Hubble Space Telescope between December 2023 to March 2024. An experimental study introduces a new cognitive fallacy, the "illusion of information adequacy". It suggests many "assume that the cross-section of relevant information to which they are privy is sufficient to adequately understand the situation" to be able to form a reasonable conclusion, opinion, or decision. The Nobel Prize in Chemistry 2024 was divided, one half awarded to David Baker "for computational protein design", the other half jointly to Demis Hassabis and John M. Jumper "for protein structure prediction" 10 October – Scientists use a high-level machine learning model "SHBoost", to process data and estimate precise stellar properties for 217 million stars observed by the Gaia mission. 11 October – Astronomers observe the "inside-out" growth of NGC 1549 by using the James Webb Space Telescope. Researchers assume that it could solve the mystery of how these complex structures are being formed from gas clouds. 12 October – The long-period comet C/2023 A3 (Tsuchinshan–ATLAS) makes its closest approach to Earth. 13 October – SpaceX achieves the first successful return and capture of a Super Heavy booster from Starship, the biggest and most powerful rocket ever to fly.
== Function == The C-terminal region of the product of the MMACHC gene is similar to TonB, a bacterial protein involved in energy transduction for cobalamin uptake. The MMACHC gene product catalyzes the decyanation of cyanocobalamin as well as the dealkylation of alkylcobalamins including methylcobalamin and adenosylcobalamin. The MMACHC gene product is characterised as a cyanocobalamin reductase (cyanide-eliminating) and a alkylcobalamin reductase. It enables the interconversion of cyano- and alkylcobalamins.
Sources: en.wikipedia.org
== Mechanism of action == After binding to lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria, polymyxins disrupt both the outer and inner membranes. The hydrophobic tail is important in causing membrane damage, suggesting a detergent-like mode of action. Removal of the hydrophobic tail of polymyxin B yields polymyxin nonapeptide, which still binds to LPS, but no longer kills the bacterial cell. However, it still detectably increases the permeability of the bacterial cell wall to other antibiotics, indicating that it still causes some degree of membrane disorganization. Gram-negative bacteria can develop resistance to polymyxins through various modifications of the LPS structure that inhibit the binding of polymyxins to LPS. Antibiotic resistance to this drug has been increasing, especially in southern China. Recently the gene mcr-1, which confers the antibiotic resistance, has been isolated from bacterial plasmids in Enterobacteriaceae.
Bromine oxides are not as well-characterised as chlorine oxides or iodine oxides, as they are all fairly unstable: it was once thought that they could not exist at all. Dibromine monoxide is a dark-brown solid which, while reasonably stable at −60 °C, decomposes at its melting point of −17.5 °C; it is useful in bromination reactions and may be made from the low-temperature decomposition of bromine dioxide in a vacuum. It oxidises iodine to iodine pentoxide and benzene to 1,4-benzoquinone; in alkaline solutions, it gives the hypobromite anion. So-called "bromine dioxide", a pale yellow crystalline solid, may be better formulated as bromine perbromate, BrOBrO3. It is thermally unstable above −40 °C, violently decomposing to its elements at 0 °C. Dibromine trioxide, syn-BrOBrO2, is also known; it is the anhydride of hypobromous acid and bromic acid. It is an orange crystalline solid which decomposes above −40 °C; if heated too rapidly, it explodes around 0 °C. A few other unstable radical oxides are also known, as are some poorly characterised oxides, such as dibromine pentoxide, tribromine octoxide, and bromine trioxide. The four oxoacids, hypobromous acid (HOBr), bromous acid (HOBrO), bromic acid (HOBrO2), and perbromic acid (HOBrO3), are better studied due to their greater stability, though they are only so in aqueous solution. When bromine dissolves in aqueous solution, the following reactions occur:
Lercanidipine (INN) is an antihypertensive (blood pressure lowering) drug. It belongs to the dihydropyridine class of calcium channel blockers, which work by relaxing and opening the blood vessels allowing the blood to circulate more freely around the body. This lowers the blood pressure and allows the heart to work more efficiently. This drug (trade name Zanidip, among others) acts more slowly than older dihydropyridines. It probably has fewer adverse effects, but a comparatively high potential for drug interactions. It was patented in 1984 and first approved for medical use in 1997. The FDA refused to approve the drug, and lercanidipine is not marketed in the United States.
The spleen is the organ which removes damaged or misshapen red blood cells from the circulation. In thalassemia, this can lead to the spleen becoming enlarged, a condition known as splenomegaly. Slight enlargement of the spleen is not a problem, however if it becomes extreme then surgical removal of the spleen (splenectomy) may be recommended.
They finished second behind Manchester United however, losing their slender advantage once they lost their penultimate match. United also eliminated Arsenal in a FA Cup semi-final replay after extra time; Wenger afterwards said: "it was a smashing game, and in the end, the luckiest won." In August 1999, Anelka joined Real Madrid, having threatened to strike if Arsenal did not grant him a move abroad. Wenger used a portion of the proceeds generated through the Anelka sale to fund the build of the Arsenal Training Centre, expressing his desire to establish a "home away from Arsenal". He renewed his forward line by signing Davor Šuker from Real Madrid, and Thierry Henry, who joined after seven "injury-interrupted" months at Juventus for £11.5 million. It was Wenger's intention to partner Anelka with Henry, but the former's departure meant the plan was scrapped. The following seasons were comparatively barren. Arsenal again exited the Champions League at the group stage, but dropped down to the UEFA Cup. Wenger guided his team to the final, where they lost to Galatasaray on penalties. In the league, Arsenal finished 18 points behind Manchester United as runners-up, and though they closed the gap to eight points in 2000–01, they never posed a serious title challenge. The trophy drought continued past 2001, when Michael Owen scored two late goals for Liverpool to beat Arsenal in the FA Cup Final. Wenger rued his team's inability to make possession count, but refused to blame individuals, namely Henry, for missing chances.
Sources: en.wikipedia.org
== See also == List of Yugoslavia international footballers List of Yugoslavia national football team goalscorers Yugoslavia national football team results (1920–41) Yugoslavia national football team results (1946–69) Yugoslavia national football team results (1970–92) Yugoslavia national under-21 football team Yugoslavia national under-20 football team
Some quantum dots pose risks to human health and the environment under certain conditions. Notably, the studies on quantum dot toxicity have focused on particles containing cadmium and have yet to be demonstrated in animal models after physiologically relevant dosing. In vitro studies, based on cell cultures, on quantum dots (QD) toxicity suggest that their toxicity may derive from multiple factors including their physicochemical characteristics (size, shape, composition, surface functional groups, and surface charges) and their environment. Assessing their potential toxicity is complex as these factors include properties such as QD size, charge, concentration, chemical composition, capping ligands, and also on their oxidative, mechanical, and photolytic stability. Many studies have focused on the mechanism of QD cytotoxicity using model cell cultures. It has been demonstrated that after exposure to ultraviolet radiation or oxidation by air, CdSe QDs release free cadmium ions causing cell death. Group II–VI QDs also have been reported to induce the formation of reactive oxygen species after exposure to light, which in turn can damage cellular components such as proteins, lipids, and DNA. Some studies have also demonstrated that addition of a ZnS shell inhibits the process of reactive oxygen species in CdSe QDs.
== Applications == The Bergmann degradation is intended for and has been used as a method for peptide sequencing. It was also proposed for use in cleaving the 3,4-bond of the penicillin nucleus. The compound 2,2-dimethyl-6-phthalimido-3-penamyl isocyanate was arrived at through various means, including the Curtius rearrangement, and it was envisioned that it could undergo the Bergmann degradation to form the desired aldehyde as well as the urea by-product. Though the Bergmann degradation was indeed possible, it was discovered that simple dilute acid hydrolysis would suffice in forming the desired product.
The United States was the biggest foreign investment source and one of Malaysia's closest allies during Mahathir's rule. A 2003 house hearing by the Subcommittee on East Asia and the Pacific of the U.S. House International Relations Committee (now called the House Committee on Foreign Affairs) summarises the relationship between the United States and Malaysia as follows: "Despite sometimes blunt and intemperate public remarks by Prime Minister Mahathir, U.S.-Malaysian cooperation has a solid record in areas as diverse as education, trade, military relations, and counter-terrorism." Mahathir was publicly critical of the foreign policy of the United States, particularly during George W. Bush's presidency. He has also condemned the US-led war on Iraq and Afghanistan. In 1984, during his first visit to the United States, Mahathir received a warm welcome. He met President Ronald Reagan in the Oval Office, followed by discussions, lunch, and a press conference. He also made a private visit to Tulsa, Oklahoma. Reagan said he and Mahathir "had a valuable exchange of views on international and bilateral issues and found ourselves in agreement to a remarkable degree", but acknowledged differences in Middle East policy. In the years that followed, Mahathir held informal meetings with US presidents George H. W. Bush, Bill Clinton, and George W. Bush at various locations to discuss issues related to palm oil and the United States' attitude towards Muslim countries. In January 1997, Mahathir visited the United States to promote Malaysia's Multimedia Super Corridor.
McQuillan, Discharge residues from cartridge-operated industrial tools, J. Forens. Sci. Soc. 24 (1984) 495–508. J.S. Wallace, Chemical Analysis of Firearms, Ammunition, and Gunshot Residue, (2008) CRC Press LLC. G.M. Wolten, R.S. Nesbitt, A.R. Calloway, G.L. Loper, P.F. Jones, Particle analysis for the detection of gunshot residue. I: Scanning electron microscopy/energy dispersive X-ray characterisation of hand deposits from firing, J. Forens. Sci. 24 (1979) 409–422. G.M. Wolten, R.S. Nesbitt, A.R. Calloway, G.L. Loper, Particle analysis for the detection of gunshot residue. II: occupational and environmental particles, J. Forens. Sci. 24 (1979) 423–430. G.M. Wolten, R.S. Nesbitt, A.R. Calloway, Particle analysis for the detection of gunshot residue. III: the case record, J. Forens. Sci. 24 (1979) 864–869.
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.