A practical reference on fatty diacid: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-07-17 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。
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。
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.
| 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 |
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.
Certificate of analysis documents from suppliers typically report purity by chromatographic area, water content, and counter-ion identity. Independent verification is advisable because reported values can be generated under differing conditions. Impurity profiles matter for research use, where aggregates, deamidation products, and residual solvents may influence experimental results. Container, lot, and chain-of-custody records support traceability. Analytical results are method-dependent, so comparisons between laboratories require the same procedure and reference standards.
Lyophilized peptide material is typically stored at or below -20 °C, with -80 °C used for longer-term archives. Vials should remain sealed and desiccated because moisture promotes aggregation and hydrolysis. Repeated freeze-thaw cycles are avoided since they can alter peptide conformation and reduce recovery. Once reconstituted, solutions are generally kept at 2-8 °C and used within a defined window. Stability beyond those windows depends on buffer composition and concentration, and exact limits are product-specific rather than universal.
Identity and purity are assessed with reversed-phase high-performance liquid chromatography, which separates the peptide from related impurities by hydrophobicity. Mass spectrometry confirms molecular weight and detects truncation or modification products. Peptide mapping after enzymatic digestion verifies the amino acid sequence. Quantitation is often performed by LC-MS/MS or by immunoassay, and the two approaches can give different values because they measure different things. Method validation parameters such as accuracy, precision, and limit of quantitation are reported alongside results.
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.
The compound binds the GLP-1 receptor on pancreatic beta cells and other tissues, activating a G-protein signaling cascade that raises intracellular cyclic AMP. This action increases glucose-dependent insulin secretion when blood glucose is elevated, while binding also slows gastric emptying and reduces glucagon release. In the central nervous system, receptor activation in the hypothalamus and brainstem contributes to reduced appetite. The fatty acid chain binds albumin, which protects the peptide from renal filtration and enzymatic degradation. This albumin binding is central to its extended circulation time.
Native GLP-1 is degraded rapidly by dipeptidyl peptidase-4. Semaglutide resists this cleavage because alanine at position 8 is replaced by alpha-aminoisobutyric acid. A second substitution at position 34 introduces arginine, which further stabilizes the peptide. The most distinctive modification is a spacer and C18 fatty diacid attached at lysine 26, enabling strong albumin affinity. These three changes together produce a half-life measured in days rather than minutes, and the same structural logic underlies other long-acting analogs in this class.
Semaglutide is a synthetic peptide analog of glucagon-like peptide-1, a hormone released from intestinal L-cells after food intake. It contains 31 amino acids and differs from native GLP-1 through modifications that slow enzymatic breakdown. The peptide was developed to extend the short circulating half-life of endogenous GLP-1, which is measured in minutes. Researchers introduced the compound in the early 2010s. Two backbone changes and a fatty acid side chain define its structure, distinguishing it from earlier GLP-1 receptor agonists.
=== Electrical === In electrical FFF a transverse electrical current (DC) is applied which creates an electric field. Depending on the charge of sample components, an electrophoretic drift velocity is induced, counteracted by the diffusion from Brownian motion, so the separation depends on the ratio of electrophoretic mobility and size. Application of electrical FFF has been limited and is currently rarely used. Other modifications have been developed, namely cyclical electrical FFF where a special alternating current is applied. It allows to separate according to electrophoretic mobility. Another variation is electrical asymmetrical flow FFF (EAF4), where an electrical field is applied in addition to a cross flow field. EAF4 overcomes the limitation of pure electrical FFF which has poor resolution and suffers from electrolysis products and bubbles contaminating the channel outflow and compromising the detector signals.
== Names == The term "sand dollar" derives from the appearance of the tests (skeletons) of dead individuals after being washed ashore. The test lacks its velvet-like skin of spines and has often been bleached white by sunlight. To beachcombers of the past, this suggested a large, silver coin, such as the old Spanish dollar, which had a diameter of 38–40 mm. Other names for the sand dollar include sand cakes, pansy shells, snapper biscuits, cake urchins, and sea cookies. In South Africa, they are known as pansy shells from their suggestion of a five-petaled garden flower. The inflated sea biscuit or Caribbean sand dollar, Clypeaster rosaceus, is thicker in height than most. In Spanish-speaking areas of the Americas, the sand dollar is most often known as galleta de mar ("sea cookie"); the translated term is often encountered in English.
==== Structure ==== The myophosphorylase structure consists of 842 amino acids. The molecular weight of the unprocessed precursor is 97 kDa. The three-dimensional structure has been determined for this protein. The interactions of several amino acids in myophosphorylase's structure are known. Ser-14 is modified by phosphorylase kinase during activation of the enzyme. Lys-680 is involved in binding the pyridoxal phosphate, which is the active form of vitamin B6, a cofactor required by myophosphorylase. By similarity, other sites have been estimated: Tyr-76 binds AMP, Cys-109 and Cys-143 are involved in subunit association, and Tyr-156 may be involved in allosteric control.
Since October 1, 2007, it has been illegal for retailers to sell tobacco in all forms to people under the age of 18 in three of the UK's four constituent countries (England, Wales, Northern Ireland, and Scotland), increased from 16. It is also illegal to sell lighters, rolling papers, and all other tobacco-associated items to people under 18. It is not illegal for people under 18 to buy or smoke tobacco, it is only illegal for a retailer to sell a tobacco-associated item to them. The age increase from 16 to 18 came into force in Northern Ireland on September 1, 2008. In the Republic of Ireland, bans on the sale of smaller 10-packs and confectionery that resembles tobacco products (candy cigarettes) came into force on May 31, 2007, in a bid to cut underaged smoking. In October 2023, Prime Minister Rishi Sunak proposed a ban on sales of cigarettes to anyone born after 2008. Most countries in the world have a legal vending age of 18. In North Macedonia, Italy, Malta, Austria, Luxembourg, and Belgium, the age for legal vending is 16. Since January 1, 2007, all cigarette machines in public places in Germany must attempt to verify a customer's age by requiring the insertion of a debit card. Turkey, which has one of the highest percentages of smokers by population, has a legal age of 18. Japan is one of the highest tobacco-consuming nations, and requires purchasers to be 20 years of age. Since July 2008, Japan has enforced this age limit at cigarette vending machines through use of the Taspo smart card.
Perlite is a volcanic rock that has been superheated into very lightweight expanded glass pebbles. It is used loose or in plastic sleeves immersed in the water. It is also used in potting soil mixes to decrease soil density. It does contain a high amount of fluorine which could be harmful to some plants. Perlite has similar properties and uses to vermiculite but, in general, holds more air and less water and is buoyant.
Sources: en.wikipedia.org
Mast cell degranulating (MCD) peptide is a cationic 22-amino acid residue peptide, which is a component of the venom of the bumblebee (Megabombus pennsylvanicus). At low concentrations, MCD peptide can stimulate mast cell degranulation. At higher concentrations, it has anti-inflammatory properties. In addition, it is a potent blocker of voltage-sensitive potassium channels.
Annular lichen planus Atrophic lichen planus Bullous lichen planus (vesiculobullous lichen planus) Erosive lichen planus Erythema dyschromicum perstans (ashy dermatosis, dermatosis cinecienta) Giant cell lichenoid dermatitis Hepatitis-associated lichen planus Hypertrophic lichen planus (lichen planus verrucosus) Idiopathic eruptive macular pigmentation Inverse lichen planus Keratosis lichenoides chronica (Nékam's disease) Kraurosis vulvae Lichen nitidus Lichen planus actinicus (actinic lichen nitidus, actinic lichen planus, lichen planus atrophicus annularis, lichen planus subtropicus, lichen planus tropicus, lichenoid melanodermatitis, lichenoid melanodermatosis, summertime actinic lichenoid eruption) Lichen planus pemphigoides Lichen planus pigmentosus Lichen planus–lichen sclerosus overlap syndrome Lichen ruber moniliformis Lichen sclerosus (lichen sclerosus et atrophicus) Lichen striatus (Blaschko linear acquired inflammatory skin eruption, linear lichenoid dermatosis) Lichen verrucosus et reticularis Lichenoid trikeratosis Lichenoid dermatitis Lichenoid reaction of graft-versus-host disease Linear lichen planus Mucosal lichen planus Peno-gingival syndrome Ulcerative lichen planus Vulvovaginal gingival syndrome Vulvovaginal lichen planus
== Further reading == Carson C, Faria G, Hellstrom WJ, Krishnamurti S, Minhas S, Moncada I, et al. (1 January 2010). "Implants, Mechanical Devices, and Vascular Surgery for Erectile Dysfunction". Journal of Sexual Medicine. 7 (1). Wiley: 501–523. doi:10.1111/j.1743-6109.2009.01626.x. PMID 20092450.
== Controversy == In 2009, the German state of Hesse decided to award its 45,000 euro Hessian Cultural Prize in July 2009 jointly to a Jew, a Muslim, a Catholic and a Lutheran to honour those involved in interfaith dialogue. There was controversy over Kermani's nomination as one of the three winners because of an essay in which Kermani wrote about his feelings about seeing a painting of the crucifixion by the seventeenth-century Italian painter Guido Reni. The issue was ultimately resolved, and Cardinal Karl Lehmann, Peter Steinacker, Kermani and Salomon Korn jointly received the prize on 26 November 2009. Kermani donated his share of the award to a Christian priest.
The Aston Medal is awarded by the British Mass Spectrometry Society to individuals who have worked in the United Kingdom and have made outstanding contributions to our understanding of the biological, chemical, engineering, mathematical, medical, or physical sciences relating directly to mass spectrometry. The medal is named after one of Britain's founders of mass spectrometry and 1922 Nobel prize winner Francis William Aston. The award is made sporadically, with no more than one medal being awarded each year. Recipients of this honour receive a gold-plated medal with a portrait of Francis Aston as well as an award certificate.
Sources: en.wikipedia.org
The House Foreign Affairs Committee has investigated the origins of the pandemic, and heard classified briefings. The Republican minority issued a report in August 2021 that they believed the origin of the pandemic was an accidental lab escape. The resurgence of the theory of a laboratory accident was fueled in part by the publication, in May 2021, of early emails between Anthony Fauci and scientists discussing the issue, before deliberate manipulation was ruled out as of March 2020. On 14 July 2021, the House Committee on Science, Space and Technology held the first congressional hearing on the origins of the virus. Bill Foster, an Illinois Democrat who chaired the hearing, said the Chinese government's lack of transparency is not in itself evidence of a lab leak and cautioned that answers may not be known even after the administration produces its intelligence report. Expert witnesses Stanley Perlman and David Relman presented to the congressman different proposed explanations for the origins of the virus and how to conduct further investigations. On 16 July 2021, CNN reported that Biden administration officials considered the lab leak theory "as credible" as the natural origins theory. In October 2022, an interim report of a Republican member of a US Senate committee concluded that a lab origin was most likely, but offered "little new evidence", according to The New York Times. In February 2023, the United States Energy Department updated its assessment on the origins of the virus, shifting from "undecided" to "low confidence" in favor of a laboratory leak.
The American chocolate maker Hershey's purchased the Aero patent the following May, later altering the flavour and texture for the American palate. During 1937, Rowntree's produced machinery for production in Ireland, Canada and South Africa, as well as for the companies Lindt and Van Houten.
Georgia Governor John M. Slaton and his wife Sarah Frances Grant left the state under security of the United States National Guard after a mob of people angered by his decision to commute Leo Frank's sentence to life imprisonment threatened them at their home in Atlanta. Armenian genocide — Rafael de Nogales Méndez, a Venezuelan serving with the Ottoman Empire, met with Mehmed Reshid, Governor of the Diyarbekir province, and learned the governor had received telegraphs directly from Interior Minister Talaat Pasha with orders to "Burn-Destroy-Kill" all Armenians in the area. Willis Carrier, who patented the modern air conditioner in 1914, formed Carrier Engineering Corporation with six other engineers to manufacturer and market the technology. They opened their first factory in Newark, New Jersey in 1920. By drawing 4.8 (32) each with Port Adelaide, South Adelaide ended the Magpies' run of 29 consecutive victories, including one against Carlton and one against a combined team from the other six SAFL clubs. The Saturday Evening Post began publishing P. G. Wodehouse's serialized novel Something Fresh, introducing the character Lord Emsworth of Blandings Castle. The village of Beachwood, Ohio was established. It became a city in 1960. Born: Paul Castellano, American gangster, head of the Gambino crime family from 1976 to 1984; as Constantino Paul Castellano, in New York City, United States (d. 1985) Willard Brown, American baseball player, outfielder for the Kansas City Monarchs and the St. Louis Browns from 1936 to 1950; in Shreveport, Louisiana, United States (d.
By the mid-2000s, Liebling had nearly disappeared from public life. He spent his days isolated in his parents' basement, trapped in a relentless cycle of addiction and self-destructive behavior. The toll of decades of substance abuse was evident in his skeletal frame, which was covered in sores and barely functioning, leading many to believe he was beyond redemption. This chapter of his life, which took an unexpected turn, became the subject of the documentary Last Days Here (2011), directed by Don Argott and Demian Fenton. Filmed over four years, the documentary follows Liebling, who is in his 50s and living in the basement of his parents' house in Alexandria, Virginia, as he battles severe drug addiction. His friend, manager, and longtime Pentagram fan Sean "Pellet" Pelletier took it upon himself to pull Liebling out of the abyss and get him back to music and a healthier life. Alongside Pelletier, the film features interviews with former Pentagram members, friends, Liebling's parents, and his then-girlfriend, Hallie. The documentary ends on a hopeful note; by 2010, Pentagram had returned to the stage, and Liebling was sober, married to Hallie, and expecting their first child. When Argott and Fenton first met Liebling, they had little hope that his story would lead anywhere. "Bobby was in such bad shape when Pellet introduced us to him that we didn't think his story would go anywhere. It really seemed like he was going to smoke himself to death in his parents' basement, something we weren't interested in documenting," Fenton recalled.
=== Teat flow rate === Teat characteristics can also have important implications for infant's sucking pattern and milk intake. Milk flow rate is defined as "the rate at which milk moves from the bottle nipple into the infant's mouth during bottle-feeding." Characteristics such as the shape of the nipple and the way it is perforated may impact flow rate and the coordination of sucking, swallowing and breathing during feeding. Unfortunately, categorization and labeling of teats to indicate flow rate is neither standardized nor consistent. There is significant variability between and within brands and models. In one study, nipples labeled "Slow" or "Newborn" (0–3 months) had flow rates ranging from 1.68 mL/min to 15.12 mL/min."The name assigned to the nipple type does not provide clear information to parents attempting to choose a nipple". This may be of extra concern in the case of fragile infants. Specialized teats are available for infants with cleft palate.
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。
Native GLP-1 is degraded within minutes by circulating enzymes. The synthetic version carries substitutions at positions that block enzymatic cleavage, plus a fatty acid side chain that promotes albumin binding. These two changes together extend circulation time from minutes to roughly a week.