二肽基肽酶-4 is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-07-16. 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 is a synthetic peptide analog of glucagon-like peptide-1, a hormone released from intestinal L cells after food intake. The molecule is a 31-amino-acid backbone modified at three positions to resist cleavage by dipeptidyl peptidase-4, the enzyme that degrades native GLP-1 within minutes. A lysine residue at position 26 carries a linker and a C18 fatty diacid, which promotes binding to serum albumin and slows renal clearance. These changes extend the circulating half-life from roughly two minutes to about one week in humans.
The sequence incorporates alpha-aminoisobutyric acid at position 8, replacing the alanine found in the natural hormone. This substitution blocks the primary DPP-4 recognition site and contributes most of the enzymatic stability. Albumin binding further protects the peptide and reduces the frequency of administration required to maintain active plasma levels. Because the fatty acid chain increases lipophilicity, the compound is formulated as a solution rather than a simple aqueous buffer. Researchers describe the design as an incremental optimization of earlier GLP-1 analogs rather than a wholly new scaffold.
Reported molecular weight is approximately 4113.6 daltons for the free base, and the peptide is supplied as a lyophilized powder or in buffered liquid form depending on the intended use. It is freely soluble in water when formulated with appropriate excipients, though the unconjugated peptide shows limited stability at neutral pH over long periods. Analytical characterization typically relies on reversed-phase high-performance liquid chromatography and mass spectrometry. Purity specifications for research-grade material commonly exceed ninety-five percent by area. Isotopic and impurity profiles differ between suppliers.
| 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 |
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.
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.
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 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.
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.
Observations in vitro and of tumours extracted from those five patients suggest that DCA might act against cancer cells by depolarising abnormal mitochondria found in glioblastoma cancer cells – allowing the mitochondria to induce apoptosis (cell death) of the malignant cells. In vitro work with DCA on neuroblastomas (which have fewer recognised mitochondrial abnormalities) showed activity against malignant, undifferentiated cells. A 2016 case report discussed and reviewed the application of DCA in central nervous system malignancies. A 2018 study found that DCA could trigger a metabolic switch from glycolysis (the Warburg effect) to mitochondrial OXPHOS and increase reactive oxygen stress affecting tumor cells. These effects were not observed in non-tumor cells. Current research has focused mainly on combining DCA with other cancer drugs to form prodrug complexes which can release both agents in a more targeted manner.
Some evidence suggests that amphetamine may be more strongly modulated by ovarian sex hormones than other psychostimulants such as methylphenidate, which may result in relatively greater variability in drug response across the menstrual cycle. Although preliminary observational evidence suggests potential benefit from adjusting amphetamine doses according to menstrual cycle phases, randomized controlled trials have not evaluated this practice.
VFFAEDVGSNKGAIIGLMVGGVVIAT In relation to the secondary structure of p3 peptide, it is thought that after the cleavage by the α- and γ- secretases and extraction from the membrane it would convert quickly from the α-helix conformation it has when it is part of APPsα sequence to a β-hairpin structure. Then, this highly hydrophobic monomer would rapidly evolve into fibrils with no soluble intermediate forms, the ones related to amyloid’s structure. The main reason why p3 does not aggregate in amyloidogenic forms while Aβ does, is that the N-terminal domain Aβ1–16, which is present in Aβ’s sequence but not in p3's one, is known to protect the hydrophobic core of the oligomers from being dissolved by the watered medium. So, p3 peptide oligomers would likely expose hydrophobic residues to water and would be less stable. As a consequence, p3 peptide structural determinants can assemble into fibrils, but no oligomeric forms have been identified. That is why p3 peptide represents the benign form of amyloid.
=== DAP pathway === The DAP pathway is found in both prokaryotes and plants and begins with the dihydrodipicolinate synthase (DHDPS) (E.C 4.3.3.7) catalysed condensation reaction between the aspartate derived, L-aspartate semialdehyde, and pyruvate to form (4S)-4-hydroxy-2,3,4,5-tetrahydro-(2S)-dipicolinic acid (HTPA). The product is then reduced by dihydrodipicolinate reductase (DHDPR) (E.C 1.3.1.26), with NAD(P)H as a proton donor, to yield 2,3,4,5-tetrahydrodipicolinate (THDP). From this point on, four pathway variations have been found, namely the acetylase, aminotransferase, dehydrogenase, and succinylase pathways. Both the acetylase and succinylase variant pathways use four enzyme catalysed steps, the aminotransferase pathway uses two enzymes, and the dehydrogenase pathway uses a single enzyme. These four variant pathways converge at the formation of the penultimate product, meso‑diaminopimelate, which is subsequently enzymatically decarboxylated in an irreversible reaction catalysed by diaminopimelate decarboxylase (DAPDC) (E.C 4.1.1.20) to produce L-lysine. The DAP pathway is regulated at multiple levels, including upstream at the enzymes involved in aspartate processing as well as at the initial DHDPS catalysed condensation step. Lysine imparts a strong negative feedback loop on these enzymes and, subsequently, regulates the entire pathway.
Sources: en.wikipedia.org
==== Energy and climate ==== The Duterte administration initially adopted a "technology neutral" policy in energy generation. Earlier in his term, Duterte stressed that coal remains the most viable source of energy if the Philippines is to accelerate industrialization, and questioned the sanctions imposed by the United States and European Union on smaller countries including the Philippines when the country's carbon footprint is not significant compared to the superpowers. The administration shifted its energy policy to prefer renewable sources of energy later in Duterte's term. At his fourth State of the Nation address in July 2019, Duterte issued an order to cut coal dependence and hasten a transition to renewable energy. In October 2020, the energy department issued a moratorium on the construction of new coal power plants and favored renewable energy sources. On February 28, 2022, Duterte issued an executive order approving the inclusion of nuclear power in the country's energy mix. To hasten the expansion of the nation's power capacity, Duterte established the inter-agency Energy Investment Coordinating Council tasked with simplifying and streamlining the approval process of big-ticket projects. On January 21, 2022, he signed a law promoting the use of microgrid systems in unserved and underserved areas to accelerate total electrification of the country. The administration made initiatives to liberalize the energy sector, allowing 100% foreign ownership in large-scale geothermal projects starting October 2020.
== Other projects == Hari is listed as a producer and writer on the 2021 film The United States vs. Billie Holiday. As of April 2018, Hari was working on a biography of American linguist and intellectual Noam Chomsky.
=== Inherited Neurodegenerative Diseases === In 2022, a new autosomal-recessive disease was discovered that is caused by mutations of the CTR1 gene. The disease is characterized by profound deficiency of copper in the central nervous system and presents with infantile seizures and neurodegeneration. hCTR1 has been implicated in neurological disorders. Copper imbalance is a hallmark of various neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, where amyloid-β peptides bind copper and generate oxidative stress. Furthermore is's associated with Huntington’s disease, prion diseases, and Amyotrophic lateral sclerosis. The hCTR1-Atox1-ATP7A/B axis is also associated with Menkes disease and Wilson’s disease, in both cases the pathology is driven primarily by mutations in proteins that regulate copper homeostasis, most notably disease-causing mutations in ATP7A or ATP7B, which lead to systemic copper deficiency or copper overload. Moreover, the human eye, and particularly the retina, is composed of highly specialized neurons, and hCTR1 plays a vital role in maintaining copper homeostasis across ocular tissues. Increased hCTR1 expression has been reported in patients with Eales disease and copper has been identified as a major driver of vision loss in ischemic and diabetic retinopathies.
Sources: en.wikipedia.org
== Storage == Absinthe that is artificially coloured or clear is aesthetically stable and can be bottled in clear glass. If naturally colored absinthe is exposed to light or air for a prolonged period, the chlorophyll gradually becomes oxidized, which has the effect of gradually changing the color from green to yellow green, and eventually to brown. The colour of absinthe that has completed this transition was historically referred to as feuille morte ("dead leaf"). In the pre-ban era, this natural phenomenon was favourably viewed, for it confirmed the product in question was coloured naturally, and not artificially with potentially toxic chemicals. Predictably, vintage absinthes often emerge from sealed bottles as distinctly amber in tint due to decades of slow oxidation. Though this colour change presents no adverse impact to the flavour of absinthe, it is generally desired to preserve the original colour, which requires that naturally coloured absinthe be bottled in dark, light-resistant bottles. Absinthe intended for decades of storage should be kept in a cool (room temperature), dry place, away from light and heat. Absinthe should not be stored in the refrigerator or freezer, as the anethole may polymerise inside the bottle, creating an irreversible precipitate, and adversely impacting the original flavour.
Since tyrosine kinase inhibitors (TKIs) are metabolized in the liver, interaction of TKIs with OATP1B1 and OATP1B3 can be considered as important molecular targets for transporter mediated drug-drug interactions. Along with the organic cation transporters and the ATP-binding cassette transporters, the OATPs play an important role in the absorption, distribution, metabolism and excretion (ADME) of many drugs.
== Neutron poisoning == A reactor can be unintentionally "shut down" by having an excess of neutron poisons in the reactor vessel. Neutron poisons are chemical byproducts of the nuclear reaction which absorb neutrons, lowering reactivity in the reactor and potentially stalling the reaction if enough poisons are allowed to build up. An example of this would be the Chernobyl disaster in 1986, when Reactor No. 4 suffered from a serious xenon-135 poisoning, which pushed the reactor into an unstable condition which later caused the accident. While neutron poisoning is not considered a shutdown in and of itself, it often requires that the reactor be shut down while the poisons are flushed from the system, as they can destabilise the reactor and cause it to behave unpredictably. Certain reactors, such as the CANDU reactor design (where it is called EPIS, or Emergency Poison Injection System), employ this phenomenon as part of their SCRAM procedure. When a SCRAM occurs, neutron poisons are injected into the reactor to immediately lower the reactivity of the reactor, at the same time or slightly prior to other shutdown mechanisms, such as control rods.
The GHRHR is a member of the secretin family of G protein-coupled receptors, and is located on chromosome 7 in humans. This protein is transmembranous with seven folds, and its molecular weight is approximately 44 kD.
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 modified version of the natural hormone, with three amino acid changes and a fatty acid side chain added. These edits extend its half-life from minutes to about one week. The core receptor activity is retained.