长效肽设计 raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-11-13 and is reviewed periodically as new material appears.
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.
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 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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C187H291N45O59 | free base, without counter-ion |
| Molecular weight | About 4114 Da | peptide backbone plus attached lipid chain |
| Plasma half-life | About 165 hours | supports once-weekly dosing in humans |
| Plasma protein binding | Greater than 99 percent | attributed mainly to serum albumin |
| Receptor target | GLP-1 receptor | Gs-coupled, raises intracellular cyclic AMP |
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.
Pharmacological activity arises from agonism at the glucagon-like peptide-1 receptor, a G protein-coupled receptor expressed in the pancreas, the gastrointestinal tract, and the brainstem. Receptor activation raises intracellular cyclic adenosine monophosphate and enhances insulin release in a glucose-dependent manner, an effect that diminishes when blood glucose concentration is low. Other effects include slowed gastric emptying and hypothalamic satiety signalling. These pathways are described well. Receptor desensitisation rates across tissues, relative to the endogenous hormone, are still under investigation, and reported findings differ between laboratories.
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.
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。
== Early life == Nayib Armando Bukele Ortez was born on 24 July 1981 in San Salvador, El Salvador. His father was Armando Bukele Kattán, a businessman and industrial chemist, and his mother is Olga Marina Ortez. Bukele's father died in 2015. Bukele was the couple's first child. He has three younger brothers, Karim, Yusef, and Ibrajim, and has four paternal half-sisters and two paternal half-brothers. Bukele's father converted from Christianity to Islam in the 1980s, became an imam, and founded four mosques in El Salvador. Bukele's mother is Catholic. Bukele's paternal grandparents were Palestinian Christians who emigrated to El Salvador from Jerusalem and Bethlehem in 1921. His maternal grandfather was Greek Orthodox, and his maternal grandmother was Catholic. Bukele completed his secondary education at the Escuela Panamericana in 1999 at age 18. Bukele enrolled at Central American University in San Salvador to study legal sciences, aspiring to become a lawyer, but dropped out to work for the Nölck advertising agency, one of his father's businesses. Nölck campaigned for the Farabundo Martí National Liberation Front (FMLN), a left-wing Salvadoran political party. In 1999, Bukele founded the marketing company Obermet, also known as 4am Saatchi & Saatchi El Salvador, and was its president from 1999 to 2006 and from 2010 to 2012. The company ran political advertising for the FMLN presidential campaigns of Schafik Hándal in 2004 and Mauricio Funes in 2009.
June 15 Iran War: US Vice President JD Vance announces that the Islamabad Memorandum was digitally signed by the US and Iran the previous day. Eight people are killed in a B-52 bomber crash in California. June 16 – SpaceX announces a US$60 billion all-stock deal to acquire Cursor, the developer of the AI coding assistant Cursor, with the transaction expected to close in the third quarter of 2026. June 17 Iran war: The Pentagon reveals that xAI's Grok model was utilized by the US during the war. Trump states that if he does not like the agreement with Iran, the United States will "go right back to dropping bombs". Trump and Iranian President Masoud Pezeshkian sign a memorandum of understanding to end the war. Trump signs the document at the Palace of Versailles, during a dinner with French President Emmanuel Macron following the G7 summit. 2027–2028 United States redistricting: Republicans in the Georgia General Assembly reject an attempt by Governor Brian Kemp to redistrict Georgia’s congressional districts for the 2028 U.S. House of Representatives elections in the state after State House Speaker Jon G. Burns announced that he will not hold a vote to do so.
This name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 1949, becoming the second element after gallium to be named after France. It was assigned the symbol Fa, but it was revised to the current Fr shortly thereafter. Francium was the last element discovered in nature, rather than synthesized, following hafnium and rhenium. Further research into francium's structure was carried out by, among others, Sylvain Lieberman and his team at CERN in the 1970s and 1980s.
In November 2013, the FDA lifted its earlier restrictions on rosiglitazone after reviewing the results of the 2009 RECORD clinical trial (a six-year, open-label randomized control trial), which failed to show elevated risk of heart attack or death associated with the medication.
Sources: en.wikipedia.org
a physician advises against the discontinuation of medications that can interfere with test results or cause medical complications; a patient has severe skin conditions such as widespread eczema or a patient has such a high sensitivity level to suspected allergens that any administration of those allergens might result in potentially serious side effects.
An organic compound is a chemical whose molecules contain carbon. Carbon is abundant in the Sun, stars, comets, and in the atmospheres of most planets of the Solar System. Organic compounds are relatively common in space, formed by "factories of complex molecular synthesis" which occur in molecular clouds and circumstellar envelopes, and chemically evolve after reactions are initiated mostly by ionizing radiation. Purine and pyrimidine nucleobases including guanine, adenine, cytosine, uracil, and thymine, as well as sugars, have been found in meteorites. These could have provided the materials for DNA and RNA to form on the early Earth. The amino acid glycine was found in material ejected from comet Wild 2; it had earlier been detected in meteorites. Comets are encrusted with dark material, thought to be a tar-like organic substance formed from simple carbon compounds under ionizing radiation. A rain of material from comets could have brought such complex organic molecules to Earth. During the Late Heavy Bombardment, meteorites may have delivered up to five million tons of organic prebiotic elements to Earth per year. Currently 40,000 tons of cosmic dust falls to Earth each year.
=== Misinformation === Naloxone has been subject to much inaccurate media reporting and many urban legends about it have become prevalent. One such myth is that naloxone makes the recipient violent. Another is that events called "Lazarus parties" have taken place, in which people reportedly took fatal overdoses in anticipation of being treated with naloxone; in reality this was a fiction spread by the police. Yet another is the claim that people have indulged in "yo-yoing", whereby they would take naloxone and opioids simultaneously to enjoy an extreme "high" and subsequent revival; the idea is scientifically nonsensical.
Sources: en.wikipedia.org
The Vaal uprising was a period of popular revolt in black townships in apartheid-era South Africa, beginning in the Vaal Triangle on 3 September 1984. Sometimes known as the township revolt and driven both by local grievances and by opposition to apartheid, the uprising lasted two years and affected most regions of the country. The National Party-led government under P. W. Botha failed to curb the violence until after it imposed a national state of emergency in June 1986. The uprising began on 3 September in the Vaal Triangle, an industrial region south of Johannesburg, where the local Vaal Civic Association had organised a stay-away to protest rent increases. In the deadliest day of protesting since the 1976 Soweto uprising, there were an estimated 300 injuries and 29 fatalities, some of whom were black local councillors executed by protestors. Over the next year, civic associations and student organisations carried the riots to other areas of the country. From late 1984, in what marked a new phase of united mass action in opposition politics, protestors received support from the emerging trade union movement, including from the Federation of South African Trade Unions. A primary target of the violence in townships were black local councillors, newly empowered by the Black Local Authorities Act. Also targeted were others viewed as collaborators of the apartheid system, such as black policemen, informants, and even school principals.
Some vaccines contain microorganisms that have been killed or inactivated by physical or chemical means. Examples include IPV (polio vaccine), hepatitis A vaccine, rabies vaccine and most influenza vaccines.
Nestlé's factory in Heilongjiang was also implicated: the Taiwanese Department of Health forced the delisting of six Neslac and KLIM products on 2 October for containing minute traces of melamine, although the minister said they did not pose a significant health risk. Since the milk crisis broke, Nestlé says it has sent 20 specialists from Switzerland to five of its Chinese plants to strengthen chemical testing. On 31 October, it announced the opening of a $10.2 million Beijing research and development centre, to "serve as the base and the reference in food safety for Nestlé in Greater China". Nestlé Chief Technology Officer said the centre was equipped with "highly sophisticated analytical tools for detecting trace amounts of residues and undesirable compounds like melamine or veterinary drugs or natural toxins".
=== Discovery of DNA structure and function === Deoxyribonucleic acid (DNA) was first discovered and isolated by Friedrich Miescher in 1869, but it remained under-studied for many decades because proteins, rather than DNA, were thought to hold the genetic blueprint to life. This situation changed after 1944 as a result of some experiments by Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrating that purified DNA could change one strain of bacteria into another. This was the first time that DNA was shown capable of transforming the properties of cells. In 1953, James Watson and Francis Crick put forward their double-helix model of DNA, based on crystallized X-ray structures being studied by Rosalind Franklin. According to the model, DNA is composed of two strands of nucleotides coiled around each other, linked together by hydrogen bonds and running in opposite directions. Each strand is composed of four complementary nucleotides – adenine (A), cytosine (C), guanine (G) and thymine (T) – with an A on one strand always paired with T on the other, and C always paired with G. They proposed that such a structure allowed each strand to be used to reconstruct the other, an idea central to the passing on of hereditary information between generations.
Sources: en.wikipedia.org
Native GLP-1 is a short-lived peptide cleared within one to two minutes by dipeptidyl peptidase-4 and related enzymes. Semaglutide keeps the receptor-binding backbone but adds substitutions and a lipid chain. These changes block the main cleavage site and allow reversible albumin binding, extending the half-life to roughly 165 hours.
Albumin is the most abundant protein in plasma and carries molecules that bear fatty-acid chains. Binding shields the peptide from renal filtration and from peptidases, keeping a circulating reservoir. Slow release from this reservoir produces sustained receptor occupancy and supports infrequent dosing.
The insulinotropic effect is glucose-dependent, meaning secretion increases mainly when glucose is elevated. This property is often described as lowering the chance of hypoglycaemia when the compound is used alone. Other glucose-lowering agents used at the same time can still cause low blood glucose.
Long-term storage is usually at minus 20 to minus 80 degrees Celsius in a sealed, desiccated container. Working aliquots can be held briefly at 2 to 8 degrees Celsius.