This is a working overview of fatty diacid chain, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-10-07. Anything still debated is marked as such rather than presented as settled.
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。
Clinical development of this compound followed earlier short-acting GLP-1 analogues that required frequent injection. Once-weekly subcutaneous formulations entered use after 2017, and an oral formulation using a permeation enhancer later became available. The oral version pairs the peptide with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, a carrier that improves uptake across the gastric epithelium. Interest has expanded from glycaemic control into weight management and metabolic liver disease. Regulatory status and approved indications differ between countries, and the product remains subject to ongoing safety monitoring.
Semaglutide is a synthetic peptide that acts as an agonist at the glucagon-like peptide-1 receptor. It is a structural analogue of human GLP-1(7-37), modified to resist enzymatic degradation by dipeptidyl peptidase-4. The peptide backbone contains alpha-aminoisobutyric acid at position 8, a substitution that stabilises the helix and slows cleavage. A fatty diacid side chain attached through a linker at lysine 34 promotes binding to serum albumin, which extends the circulating half-life. These two modifications together allow less frequent administration than native GLP-1 requires.
Activation of the GLP-1 receptor couples to Gs signalling and raises intracellular cyclic AMP in pancreatic beta cells. The resulting insulin release depends on prevailing glucose concentrations, so the effect is greater when glucose is elevated. Receptor engagement also suppresses glucagon secretion and slows gastric emptying, which flattens post-meal glucose excursions. In the central nervous system, signalling in hypothalamic and brainstem regions is associated with reduced appetite and lower energy intake. Studies continue to examine effects on cardiac, renal and hepatic endpoints; whether those benefits are independent of weight change 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 |
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 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.
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 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.
Immunoglobulin G (IgG) antibodies are large heterodimeric molecules, approximately 150 kDa and are composed of two kinds of polypeptide chain, called the heavy (~50kDa) and the light chain (~25kDa). The two types of light chains are kappa (κ) and lambda (λ). By cleavage with enzyme papain, the Fab (fragment-antigen binding) part can be separated from the Fc (fragment crystallizable region) part of the molecule. The Fab fragments contain the variable domains, which consist of three antibody hypervariable amino acid domains responsible for the antibody specificity embedded into constant regions. The four known IgG subclasses are involved in antibody-dependent cellular cytotoxicity. Antibodies are a key component of the adaptive immune response, playing a central role in both in the recognition of foreign antigens and the stimulation of an immune response to them. The advent of monoclonal antibody technology has made it possible to raise antibodies against specific antigens presented on the surfaces of tumors. Monoclonal antibodies can be acquired in the immune system via passive immunity or active immunity. The advantage of active monoclonal antibody therapy is the fact that the immune system will produce antibodies long-term, with only a short-term drug administration to induce this response. However, the immune response to certain antigens may be inadequate, especially in the elderly. Additionally, adverse reactions from these antibodies may occur because of long-lasting response to antigens.
Nitriles are susceptible to hydrogenation over diverse metal catalysts. The reaction can afford either the primary amine (RCH2NH2) or the tertiary amine ((RCH2)3N), depending on conditions. In conventional organic reductions, nitrile is reduced by treatment with lithium aluminium hydride to the amine. Reduction to the imine followed by hydrolysis to the aldehyde takes place in the Stephen aldehyde synthesis, which uses stannous chloride in acid.
== Repeat-induced point mutation == In molecular biology, repeat-induced point mutation or RIP is a process by which DNA accumulates G:C to A:T transition mutations. Genomic evidence indicates that RIP occurs or has occurred in a variety of fungi while experimental evidence indicates that RIP is active in Neurospora crassa, Podospora anserina, Magnaporthe grisea, Leptosphaeria maculans, Gibberella zeae, Nectria haematococca and Paecilomyces variotii. In Neurospora crassa, sequences mutated by RIP are often methylated de novo. RIP occurs during the sexual stage in haploid nuclei after fertilization but prior to meiotic DNA replication. In Neurospora crassa, repeat sequences of at least 400 base pairs in length are vulnerable to RIP. Repeats with as low as 80% nucleotide identity may also be subject to RIP. Though the exact mechanism of repeat recognition and mutagenesis are poorly understood, RIP results in repeated sequences undergoing multiple transition mutations. The RIP mutations do not seem to be limited to repeated sequences. Indeed, for example, in the phytopathogenic fungus L. maculans, RIP mutations are found in single copy regions, adjacent to the repeated elements. These regions are either non-coding regions or genes encoding small secreted proteins including avirulence genes. The degree of RIP within these single copy regions was proportional to their proximity to repetitive elements. Rep and Kistler have speculated that the presence of highly repetitive regions containing transposons, may promote mutation of resident effector genes.
The seventh generation Familia (BG) included three-door hatchback, five-door liftback, and four-door saloon variants, none of which share any body panels. The new five-door liftback version was called the Familia Astina in Japan and was sold as the 323F or 323 Astina elsewhere. The BF wagon (originally introduced in 1985) was carried over in facelifted form, although Ford marketed a wagon on the new platform as part of the North American Escort line. The BG Familia was available with front- or all-wheel drive and 1.3–1.8 L petrol engines or a 1.7 L diesel engine. Later, a turbocharged engine was added, especially developed for homologation purposes for the World Rally Championship (WRC), Group A category. The all-wheel drive models (including the turbocharged GT-X) were introduced in August 1989. In Japan, the 1.6 L SOHC was only available coupled to all-wheel drive. With a carburettor, it offered 91 PS (67 kW; 90 hp), the same as the lower-spec 1.5 L SOHC, but with a somewhat larger torque curve. In Europe, only the 1.8 L SOHC (in naturally aspirated, 106 PS (78 kW; 105 hp) form or either of the turbocharged variants) was offered with four-wheel-drive. Trim lines in Japan included "Clair", "Pepper", "Interplay", "Supreme", "GT", "GT-X" and "GT-R". The Supreme model was only available in saloon form and features the larger bumpers and bootlid-mounted number plate recess of the American market Protegé. Carburetted models were mostly dropped in the 1991 facelift, replaced by single-point fuel injection.
== Use in cancer therapy == KLH is being tested in a variety of cancer vaccines, including non-Hodgkin's lymphoma, cutaneous melanoma, breast and bladder cancer. These vaccines contain specific tumor-associated antigens conjugated to KLH to stimulate anti-tumor immune responses which can destroy tumor cells. The rapidly growing interest in therapeutic vaccines (i.e. active immunotherapies) for cancer and the documented efficacy of KLH as a superior carrier protein for cancer vaccines are creating a significant biopharmaceutical market for KLH formulations. Assays to monitor humoral immune responses against KLH in human serum have been developed to facilitate optimal use of biomedical KLH applications.
Sources: en.wikipedia.org
=== Tolerance === Unlike with other classical psychedelics, tolerance does not seem to develop to the subjective effects of DMT. Studies report that DMT did not exhibit tolerance upon repeated administration of twice a day sessions, separated by 5 hours, for 5 consecutive days; field reports suggests a refractory period of only 15 to 30 minutes, while the plasma levels of DMT was nearly undetectable 30 minutes after intravenous administration. Another study of four closely spaced DMT infusion sessions with 30 minute intervals also suggests no tolerance buildup to the psychological effects of the compound, while heart rate responses and neuroendocrine effects were diminished with repeated administration. Similarly to DMT by itself, tolerance does not appear to develop to ayahuasca. A fully hallucinogenic dose of DMT did not demonstrate cross-tolerance to human subjects who are highly tolerant to LSD; hence, research suggests that DMT exhibits unique pharmacological properties compared to other classical psychedelics. Contrary to earlier findings however, subsequent clinical studies employing DMT by continuous intravenous infusion (also known as DMTx) have found rapid and moderate acute tolerance development with DMT.
Russell has proposed that "the purpose of life is to hydrogenate carbon dioxide" (as part of a "metabolism-first", rather than a "genetics-first", scenario). The physicist Jeremy England has argued from general thermodynamic considerations that life was inevitable. An early version of this idea was Oparin's 1924 proposal for self-replicating vesicles. In the 1980s and 1990s came Wächtershäuser's iron–sulfur world theory and Christian de Duve's thioester models. More abstract and theoretical arguments for metabolism without genes include Freeman Dyson's mathematical model and Stuart Kauffman's collectively autocatalytic sets in the 1980s. Kauffman's work has been criticized for ignoring the role of energy in driving biochemical reactions in cells.
==== AIDS Relief ==== In the State of the Union address in January 2003, Bush outlined a five-year strategy for global emergency AIDS relief, the President's Emergency Plan for AIDS Relief (PEPFAR). Bush announced $15 billion for this effort, which directly supported life-saving antiretroviral treatment for more than 3.2 million men, women and children worldwide. The U.S. government had spent some $44 billion on the project since 2003 (a figure which includes $7 billion contributed to the Global Fund to Fight AIDS, Tuberculosis, and Malaria, a multilateral organization), which saved an estimated five million lives by 2013. The New York Times correspondent Peter Baker wrote in 2013 that "Bush did more to stop AIDS and more to help Africa than any president before or since." By 2023, PEPFAR was estimated to have saved over 25 million lives, alleviating the severity of the HIV/AIDS epidemic especially in Sub-Saharan Africa, and was called "George W. Bush's greatest accomplishment" by Vox.
Komagataella is a methylotrophic yeast within the order Pichiales. It was found in the 1960s as Pichia pastoris, with its feature of using methanol as a source of carbon and energy. In 1995, P. pastoris was reassigned into the sole representative of genus Komagataella, becoming Komagataella pastoris. In 2005, it was found that almost all strains used industrially and in labs are a separate species, K. phaffii. Later studies have further distinguished new species in this genus, resulting in a total of 7 recognized species. It is not uncommon to see the old name still in use in the context of protein production, as of 2023; in less formal use, the yeast may confusingly be referred to as pichia. After years of study, Komagataella is widely used in biochemical research and biotech industries. With strong potential for being an expression system for protein production, as well as being a model organism for genetic study, Komagataella phaffii has become important for biological research and biotech applications.
When testing urine for ketones, the sample needs to be as fresh as possible. Ketones evaporate quickly, so there is a chance of getting a false negative test result if testing older urine. The urine testing strip bottle has instructions and color charts to illustrate how the color on the strip will change given the level of ketones or glucose in the urine over 15 (ketones–Ketostix) or 30 (glucose–Ketodiastix) seconds. Reading the colors at those time intervals is important because the colors will continue to darken and a later reading will be an incorrect result. Timing with a clock or watch second hand instead of counting is more accurate. At present, there is only one glucometer available for home use that tests blood for ketones using special strips for that purpose–Abbott's Precision Xtra. This meter is known as Precision, Optium, or Xceed outside of the US. The blood ketone test strips are very expensive; prices start at about US$50 for ten strips. It is most likely urine test strips–either ones that test only for ketones or ones that test for both glucose and ketones in urine would be used. The table above is a guide to when ketones may be present.
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 belongs to the incretin mimetic class and acts as a long-acting glucagon-like peptide-1 receptor agonist. The class includes several peptides with different half-lives and routes of administration.