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.
Reviewed 2026-03-26. Anything still debated is marked as such rather than presented as settled.
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.
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 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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Acylated GLP-1 receptor agonist | 31-residue synthetic peptide |
| Molecular formula | C187H291N45O59 | established for the free peptide |
| Appearance | White to off-white powder | as supplied before formulation |
| Solubility | Freely soluble in water | aqueous buffers near neutral pH |
| Typical storage | 2 to 8 degrees Celsius, protected from light | powder and solution forms differ in shelf life |
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 activation raises intracellular cyclic AMP through Gs coupling, which promotes glucose-dependent insulin release and suppresses glucagon secretion when blood glucose is elevated. Effects outside the pancreas include slower gastric emptying and altered appetite signalling in the hypothalamus and hindbrain. The relative contribution of each tissue to overall metabolic outcomes remains an area of active investigation. Central mechanisms in particular are inferred mainly from animal models and indirect human measures rather than direct observation.
Serum protein binding dominates the pharmacokinetic profile. The attached chain associates strongly with albumin, shielding the peptide from enzymatic attack and slowing filtration by the kidney. This interaction extends the circulation half-life to roughly one week in humans, which supports weekly administration intervals. An oral version pairs the peptide with an absorption enhancer that transiently alters gastric epithelium, permitting limited uptake; bioavailability by that route is substantially lower than by injection.
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。
Cannabidiol (CBD) is a phytocannabinoid, one of 113 identified cannabinoids in Cannabis, along with tetrahydrocannabinol (THC), and accounts for up to 40% of the plant's extract. Medically, it is an anticonvulsant used to treat two rare forms of childhood epilepsy. It was discovered in 1940. Clinical research on CBD has included studies related to the treatment of anxiety, addiction, psychosis, movement disorders, and pain, but there is insufficient high-quality evidence that CBD is effective for these conditions. CBD is sold as a herbal dietary supplement and promoted with unproven claims of particular therapeutic effects. Cannabidiol can be taken internally in multiple ways, including by inhaling cannabis smoke or vapor, swallowing it by mouth, and through use of an aerosol spray inside the cheek. It may be supplied as CBD oil containing only CBD as the active ingredient (excluding THC or terpenes), CBD-dominant hemp extract oil, capsules, dried cannabis, or prescription liquid solution. CBD does not have the same psychoactivity as THC, and can modulate the psychoactive effects of THC on the body if both are present. Conversion of CBD to THC can occur when CBD is heated to temperatures between 250–300 °C, potentially leading to its partial transformation into THC. In the United States, the cannabidiol drug Epidiolex was approved by the Food and Drug Administration (FDA) in 2018, for the treatment of two seizure disorders.
South Africa Act 1909 Constitution of the Republic of South Africa 1961 Constitution of the Republic of South Africa 1983 Constitution of the Republic of South Africa 1993 Constitution of the Republic of South Africa 1996 Kahn, E. (1961). The New Constitution. Kruger, D.W. (1969). The Making of a Nation. May, H.J. (1949). The South African Constitution.
Quinteiro, Javier; Baibai, Tarik; Oukhattar, Laila; Soukri, Abdelaziz; Seixas, Pablo; Rey-Méndez, Manuel (2011). "Multiple paternity in the common octopus Octopus vulgaris (Cuvier, 1797), as revealed by microsatellite DNA analysis" (PDF). Molluscan Research. 31 (1): 15–20. Bibcode:2011MollR..311.1.2Q. CiteSeerX 10.1.1.363.8342. doi:10.11646/mr.31.1.2. {{cite journal}}: Cite uses deprecated parameter |citeseerx= (help) "CephBase: Common octopus". Archived from the original on 17 August 2005. Photos of Common octopus in the Sealife Collection
Recent changes in Moscow's regional climate are often cited by climate scientists as evidence of global warming, since the city is in the middle latitudes of the Northern Hemisphere; however, by definition, climate change is global, not regional. During the summer, very high temperatures are often recorded in the city (in 2001, 2002, 2003, 2010, 2011, and 2021). Along with the southern part of Central Russia, after recent years of hot summer seasons, Moscow's climate shows hot-summer classification trends. Winter has also become significantly milder: for example, the average January temperature in the early 1900s was −12.0 °C (10.4 °F), while it is currently about −7.0 °C (19.4 °F). The end of January–February is often colder, with frosts reaching −30.0 °C (−22.0 °F) a few nights per year (in 2006, 2010, 2011, 2012, and 2013). As of 2024, the most recent decade was the warmest in the history of meteorological observations of Moscow. Temperature changes in the city are shown in the table below:
Sources: en.wikipedia.org
Such a molecule might be extracted from a natural product or even be a drug on the market which could be improved upon (so-called "me too" drugs). Other methods, such as virtual high throughput screening, where screening is done using computer-generated models and attempting to "dock" virtual libraries to a target, are also often used. Another method for drug discovery is de novo drug design, in which a prediction is made of the sorts of chemicals that might (e.g.) fit into an active site of the target enzyme. For example, virtual screening and computer-aided drug design are often used to identify new chemical moieties that may interact with a target protein. Molecular modelling and molecular dynamics simulations can be used as a guide to improve the potency and properties of new drug leads. There is also a paradigm shift in the drug discovery community to shift away from HTS, which is expensive and may only cover limited chemical space, to the screening of smaller libraries (maximum a few thousand compounds). These include fragment-based lead discovery (FBDD) and protein-directed dynamic combinatorial chemistry. The ligands in these approaches are usually much smaller, and they bind to the target protein with weaker binding affinity than hits that are identified from HTS. Further modifications through organic synthesis into lead compounds are often required. Such modifications are often guided by protein X-ray crystallography of the protein-fragment complex.
where De is the effective dose, B bioavailability and Da the administered dose. Therefore, if a drug has a bioavailability of 0.8 (or 80%) and it is administered in a dose of 100 mg, the equation will demonstrate the following:
=== General References === ASTM F1416 Standard Guide for Selection of Time-Temperature Indicators Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6 Taoukis, P. and T.P. Labuza. 2003. Time temperature indicators. In: Novel Food Packaging Techniques. R. Ahvenainen (ed.). Woodhead Publ., Cambridge, UK.
Sources: en.wikipedia.org
Rho factor A protein cofactor involved in signaling the termination of transcription in bacteria. Rho factor recognizes and binds a C-rich/G-poor terminator sequence in the nascent RNA transcript, which promotes dissociation of the transcriptional complex and release of the transcript from the DNA template. Other mechanisms of termination which do not require Rho factor also exist.
=== Davis Cup === Zverev made his Davis Cup debut for Germany against the Czech Republic in 2016. He faced No. 7 Tomáš Berdych in his debut match and took a two sets to one lead before ultimately losing in five sets. After the Czech Republic won the doubles rubber while Kohlschreiber won both singles matches, Zverev faced Lukáš Rosol in a decisive fifth rubber. Rosol won the match easily to send the Czech Republic into the next round. In the 2017 against Belgium, Zverev recorded his first career match win in the competition against Arthur De Greef, but lost the doubles rubber with his brother as well as his second singles match to Steve Darcis. Belgium won the tie 4–1. Zverev won his first Davis Cup tie in 2018, winning both of his singles matches against Alex de Minaur and Kyrgios to lead Germany to a 3–1 victory over Australia. In the quarterfinals, Germany took a 2–1 lead against Spain behind Zverev's win over David Ferrer and a victory in doubles. However, Spain ultimately won the tie on the final day after Zverev was unable to defeat Nadal and Kohlschreiber lost a tight five-set match to Ferrer. In 2019, the format of the Davis Cup was changed to have eighteen countries competing in the finals over a single week in November, all but six of which were decided through a qualifying round in February. Germany was placed in the qualifying round and drawn against Hungary. Zverev participated and won both of his singles matches as Germany won the tie 5–0. He did not participate in the finals in November, in which Germany lost in the quarterfinals.
Still, during the Soviet era, Jews were encouraged to admire Cossacks as the antitheses of the "parasitic" and "feeble dwellers of the shtetl." A number of Yiddish writers, including Khaim Melamud, Shmuel Gordon, Viktor Fink, and Shmuel Godiner, presented fictionalized accounts of peaceful Jewish-Cossack coexistence, while efforts were made by the pro-Soviet press to present Khmelnytsky as a heroic figure and Cossacks as liberators from the Nazis. Historiography interprets Cossackdom in imperial and colonial terms. In Ukraine, where Cossackdom represents historical and cultural heritage, some people have begun attempting to recreate the images of Ukrainian Cossacks. Traditional Ukrainian culture is often tied in with the Cossacks, and the Ukrainian government actively supports these attempts. The traditional Cossack bulava serves as a symbol of the Ukrainian presidency, and the island of Khortytsia, the origin and center of the Zaporozhian Sich, has been restored. The video game Cossacks: European Wars is a Ukrainian-made game series influenced by Cossack culture. Cossacks are also mentioned outside Europe. The Japanese anime The Doraemons, part of the larger Doraemon anime series, has a Cossack character, Dora-nichov, who is from Russia.
These data exclude two major producers: the United States and China. A previous sharp increase was observed in 2004 from $4–$5 to $27/lb. The price was relatively stable during 2004–2010 at about US$30 per pound (in 100 pound lots) but increased to $65/lb in 2011. The consumption in 2010 was divided as follows: metallurgy – 30%, glass manufacturing – 30%, agriculture – 10%, chemicals and pigments – 10%, and electronics – 10%. China is the dominant consumer of selenium at 1,500–2,000 tonnes/year.
Sources: en.wikipedia.org
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and neutral endopeptidases. Semaglutide carries a non-natural amino acid at position eight that blocks that cleavage, and a fatty diacid side chain that binds albumin. The result is a much longer duration of action than the native hormone.
The fatty diacid chain associates strongly with serum albumin, which keeps the peptide in circulation and shields it from rapid renal clearance. Bound peptide is released gradually, producing a sustained receptor signal. This mechanism also reduces the peak-to-trough variation seen with shorter-acting analogues.
The balance between peripheral receptor activation and signalling in the central nervous system is not fully resolved. The extent to which slowed gastric emptying accounts for reduced energy intake, compared with direct effects on appetite circuits, is debated. Long-term effects on lean mass and on tissues outside the gut and brain are still under study.
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.