Everything below concerns receptor agonist. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-01-04. 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。
Peptides are sensitive to temperature, light, oxygen, and repeated freeze-thaw cycles. Semaglutide in dry form is generally held at refrigerated temperatures, while reconstituted solutions require a defined short-term storage window. Vials should be kept in secondary packaging to limit photodegradation, and exposure to alkaline conditions is avoided because it accelerates chemical degradation. Adsorption to glass and some plastics can reduce the measured concentration of dilute solutions, so low-binding polypropylene containers are preferred for analytical work. Each transfer step introduces a small risk of contamination, and closed handling practices reduce that risk.
Routine characterisation of the peptide relies on reversed-phase high-performance liquid chromatography, often paired with ultraviolet detection near 214 nanometres. Related substances such as deamidated, oxidised, and truncated sequences elute at characteristic positions and are quantified by area percentage. Electrospray ionisation mass spectrometry confirms the molecular mass and can resolve some closely related variants. Peptide mapping after enzymatic digestion provides sequence-level verification and is useful when a full identity profile is required. Method parameters such as column chemistry, gradient, and mobile-phase pH influence the separation and must be reported alongside results.
Material described as research-grade is not necessarily manufactured to pharmaceutical standards, and purity figures depend on the method used to obtain them. A certificate of analysis states the measured purity, the analytical technique, and the batch identifier, but the underlying data are not always included. Independent testing by a second laboratory is a common way to confirm identity and purity. Uncertainties remain about how storage history affects long-term stability, and about how well results from one laboratory transfer to another. Documentation of handling conditions supports comparison between batches.
| 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 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.
Development began in the early 2010s with the goal of extending GLP-1 activity beyond the brief window achieved by native peptide infusion. The earliest approved formulation was a subcutaneous injection given once weekly. A later oral tablet pairs the peptide with an absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, usually shortened to SNAC. That carrier lowers local pH and helps the peptide cross gastric tissue. Both routes deliver the same active molecule.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, a gut hormone released after meals. Its backbone retains the GLP-1 sequence but incorporates two substitutions that slow enzymatic breakdown by dipeptidyl peptidase-4. A short polyethylene glycol linker and a C18 fatty diacid are attached to the peptide chain, allowing the molecule to bind serum albumin and remain in circulation far longer than the native hormone. The result is a circulating half-life measured in days rather than the minutes typical of endogenous GLP-1.
Receptor activation occurs at GLP-1 receptors distributed across pancreatic islets, the hypothalamus, and the gastrointestinal tract. Binding triggers G protein signaling that raises cyclic AMP and enhances glucose-dependent insulin release. Because the effect depends on prevailing glucose levels, insulin secretion does not rise when blood sugar is already low. Signaling in the brain and gut also influences appetite and gastric emptying, which is why the compound appears in both metabolic and weight-related research literature.
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.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, developed by Novo Nordisk and first approved in 2017 for type 2 diabetes. It belongs to the incretin mimetic class, a group of agents that reproduce the glucose-dependent actions of endogenous GLP-1. The molecule was engineered to resist degradation by dipeptidyl peptidase-4 and to bind serum albumin, extending its half-life from minutes to roughly one week. Approval for chronic weight management followed in 2021, based on large cardiovascular and obesity outcome trials.
GLP-1 receptors are expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises cyclic AMP, enhances glucose-dependent insulin secretion, and suppresses glucagon release when blood glucose is high. Effects on gastric emptying and on hypothalamic appetite circuits reduce energy intake. Because insulin release remains glucose-dependent, the risk of hypoglycemia is low when the drug is used alone. The precise contribution of each pathway to body weight change in humans remains an area of active investigation.
== Adverse effects == During the trials there were 5 deaths from acute liver failure and 2 other patients were saved from death by receiving a liver transplant. The toxicity of FIAU was notably delayed as the severe effects became apparent after 13 weeks of treatment. The specific toxic symptoms include: fatigue, skin rash, nausea, bone marrow suppression, seizures, pain in the arms and legs, hepatic (liver) failure (with mild jaundice), lactic acidosis (severe accumulation of lactic acid in the blood), pancreatitis, micro versicular steatosis (marked accumulation of the fat within the cells of the liver), myopathy and peripheral neuropathy. The FIAU is a clear example of direct drug-induced mitochondrial toxicity. Besides being incorporated into the viral DNA, FIAU is also incorporated into mitochondrial DNA. As FIAU is inserted into the growing chain of mitochondrial DNA replication. This leads to an inability of mitochondrial DNA polymerase γ to (further) replicate the DNA. There is a lack of DNA to provide ‘instructions’ to the mitochondria, resulting in reduction of mitochondrial respiration and the activity of mitochondrial respiratory complexes. The mitochondria no longer produce sufficient energy, causing lactic acid to form rapidly. The acute liver failure is a direct result of this cascade. The liver is an energy-intensive organ and thus the failure of its cellular power plants will quickly lead to physical decay. But this damage is not limited to only the liver, as mitochondria are found all throughout the body.
Algae has shown selectivity for strontium in studies, where most plants used in bioremediation have not shown selectivity between calcium and strontium, often becoming saturated with calcium, which is present in greater quantities in nuclear waste. Strontium-90 with a half-life around 30 years, is classified as high-level waste. Researchers have looked at the bioaccumulation of strontium by Scenedesmus spinosus (algae) in simulated wastewater. The study claims a highly selective biosorption capacity for strontium of S. spinosus, suggesting that it may be appropriate for use of nuclear wastewater. A study of the pond alga Closterium moniliferum using non-radioactive strontium found that varying the ratio of barium to strontium in water improved strontium selectivity.
Taylor was not keen on Thomas taking another trip to the United States, and thought that if he had a permanent address in London he would be able to gain steady work there. She bought a property, 54 Delancey Street, in Camden Town, and in late 1951 Thomas and Caitlin lived in the basement flat. Thomas would describe the flat as his "London house of horror" and did not return there after his 1952 tour of America.
Sources: en.wikipedia.org
== Awards == Vincent du Vigneaud Award for Excellence in Peptide Science (2000) American Chemical Society's Ralph F. Hirschmann Award in Peptide Chemistry (2004) Bruce Merrifield Award (2005) Fellow of the American Association of Pharmaceutical Scientists (2006) Dan K. Richardson Entrepreneurship Program's 2011 Entrepreneur of the Year
leukocytes with specific granules), which include the neutrophils, innate lymphoid cells, mast cells, eosinophils, and basophils. Innate lymphoid cells (ILCs) derived from common lymphoid progenitor and belong to the lymphoid lineage. Mast cells reside in connective tissues and mucous membranes and regulate the inflammatory response. They are most often associated with allergy and anaphylaxis. Basophils and eosinophils are related to neutrophils. They secrete chemical mediators that are involved in defending against parasites and play a role in allergic reactions, such as asthma. Natural killer cells (NK cells) do not directly attack invading microbes but destroy compromised host cells, such as tumor cells or virus-infected cells. NK cells recognise such cells by a condition known as "missing self", which involves low levels of a cell-surface marker called MHC I (major histocompatibility complex)—a situation that can arise in viral infection. Normal body cells are not recognized and attacked by NK cells because they express intact self MHC antigens, which inhibit NK cell activity. Monocytes, upon moving to injured tissue, turn into dendritic cells and macrophages while promoting tissue healing. The major humoral component of the innate immune response is the complement system, a biochemical cascade that attacks the surfaces of foreign cells.
The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – is an assay for evaluating the extrinsic pathway and common pathway of coagulation. This blood test is also called protime INR and PT/INR. They are used to determine the clotting tendency of blood, in conditions such as the measure of warfarin dosage, liver damage (cirrhosis), and vitamin K status. PT measures the following coagulation factors: I (fibrinogen), II (prothrombin), V (proaccelerin), VII (proconvertin), and X (Stuart–Prower factor). PT is often used in conjunction with the activated partial thromboplastin time (aPTT) which measures the intrinsic pathway and common pathway of coagulation.
In Early June, German Forces (estimated at 9 divisions with tanks and artillery) began concentrating in the Lepel-Chashniki area. By June 10, the Germans had fortified the Lepel-Borisov Highway with Trenches and pillboxes every 100 meters, trapping the partisans. The Brigade was forced to retreat into the marshy terrains of Lake Palik. Under constant artillery fire and aerial bombardment, the partisans were pushed back into the forests, where they faced severe supply issues. Records indicate that during the height of the encirclement, the encircled partisans were suffering from extreme famine and were surviving on grass and animal hides.
Sources: en.wikipedia.org
Bin Laden selected these men because they were educated, could speak English, and had experience living in the West. New recruits were routinely screened for special skills and al-Qaeda leaders consequently discovered that Hani Hanjour already had a commercial pilot's license. Hanjour arrived in San Diego on December 8, 2000, joining al-Hazmi. They soon left for Arizona, where Hanjour took refresher training. Marwan al-Shehhi arrived at the end of May 2000, while Atta arrived on June 3, 2000, and Jarrah arrived on June 27, 2000. Bin al-Shibh applied several times for a visa to the United States, but as a Yemeni, he was rejected out of concerns he would overstay his visa. Bin al-Shibh stayed in Hamburg, providing coordination between Atta and Mohammed. The three Hamburg cell members all took pilot training in South Florida at Huffman Aviation. In the spring of 2001, the secondary hijackers began arriving in the United States. In July 2001, Atta met with bin al-Shibh in Spain, where they coordinated details of the plot, including final target selection. Bin al-Shibh passed along bin Laden's wish for the attacks to be carried out as soon as possible. Some of the hijackers received passports from corrupt Saudi officials who were family members or used fraudulent passports to gain entry.
=== Proton backscattering === Protons can also interact with the nucleus of the atoms in the sample through elastic collisions, Rutherford backscattering, often repelling the proton at angles close to 180 degrees. The backscatter give information on the sample thickness and composition. The bulk sample properties allow for the correction of X-ray photon loss within the sample.
Air service through UPS was first used in 1929 through private airlines. However, the Great Depression and a lack of volume ended the service. In 1953, UPS resumed air service called UPS Blue Label Air with two-day service to major cities along the East Coast and West Coast.
== Enthalpy change == The enthalpy of sublimation has commonly been predicted using the equipartition theorem. If the lattice energy is assumed to be approximately half the packing energy, then the following thermodynamic corrections can be applied to predict the enthalpy of sublimation. Assuming a 1 molar ideal gas gives a correction for the thermodynamic environment (pressure and volume) in which pV = RT, hence a correction of 1RT. Additional corrections for the vibrations, rotations and translation then need to be applied. From the equipartition theorem gaseous rotation and translation contribute 1.5RT each to the final state, therefore a +3RT correction. Crystalline vibrations and rotations contribute 3RT each to the initial state, hence −6RT. Summing the RT corrections; −6RT + 3RT + RT = −2RT. This leads to the following approximate sublimation enthalpy. A similar approximation can be found for the entropy term if rigid bodies are assumed.
N-Desalkylflurazepam (also known as norflurazepam) is a benzodiazepine analog and an active metabolite of several other benzodiazepine drugs including flurazepam, flutoprazepam, fludiazepam, midazolam, flutazolam, quazepam, and ethyl loflazepate. It is long-acting, prone to accumulation, and binds unselectively to the various benzodiazepine receptor subtypes. It has been sold as a designer drug from 2016 onward.
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。
Different techniques detect different classes of impurities, so a single number does not describe a sample completely. Reversed-phase chromatography resolves related peptides well but can miss inorganic salts, while mass spectrometry confirms mass without quantifying everything present. Comparing results requires knowing which method was used and how it was validated.