Everything below concerns 二肽基肽酶-4. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-09-19. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide, GLP-1 receptor agonist | 31 amino acid residues |
| Molecular formula | C187H291N45O59 | free peptide, no counter-ion |
| Approximate mass | 4114 Da | matches theoretical value |
| Receptor target | Glucagon-like peptide-1 receptor | Gs-coupled, cyclic AMP pathway |
| Circulation half-life | About one week in humans | extended by albumin association |
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 or 280 nanometres is widely used to assess purity and to resolve related impurities. Liquid chromatography coupled to mass spectrometry confirms identity through the protonated molecular ion and fragment ions formed in tandem experiments. Capillary electrophoresis and peptide mapping after enzymatic digestion supply complementary information on charge variants and modification sites. Circular dichroism and nuclear magnetic resonance can report on secondary structure in solution. Absolute quantification usually depends on an external standard, and reported purity depends on the detection wavelength and integration parameters chosen.
Lyophilised material appears as a white to off-white cake or powder that is hygroscopic, and containers are usually equilibrated to room temperature before opening to limit condensation. Dissolution is performed in water, phosphate-buffered saline, or a mildly alkaline buffer, since solubility rises above neutral pH. Gentle inversion or low-speed mixing is preferred, because vigorous vortexing can promote surface denaturation and aggregation. Complete dissolution may require several minutes, and brief sonication is sometimes applied. Passing the solution through a 0.22 micrometre membrane removes particulates but does not by itself sterilise the liquid.
Storage at minus 20 degrees Celsius or lower in a desiccated container preserves the peptide for extended periods, while working solutions are commonly held at two to eight degrees Celsius for short intervals. Light exposure and repeated freeze-thaw cycles accelerate degradation, so dividing material into single-use aliquots is generally recommended. Adsorption to glass and plastic surfaces can lower the measured concentration of dilute solutions, particularly below one milligram per millilitre. The degradation routes most often reported for GLP-1 analogues are deamidation, methionine oxidation, and backbone hydrolysis. Relative rates under specific conditions are frequently described only for individual formulations.
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。
该分子作为 GLP-1 受体的选择性激动剂发挥作用，受体属于 B 类 G 蛋白偶联受体家族，激活后经 Gs 通路提升细胞内环腺苷酸水平。在胰腺 β 细胞，信号促进葡萄糖依赖性的胰岛素释放，血糖偏低时该作用明显减弱。在胰岛 α 细胞，胰高血糖素分泌受到抑制。中枢神经系统与胃肠道同样存在受体表达，相应信号参与食欲调节以及胃排空速率的降低。
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。
=== pH and bile tolerance === Testing of L. fermentum against different pH concentration solutions revealed that it has a strong pH tolerance by its ability to grow and survive a few hours after being incubated in a 3-pH level solution. Strains of L. fermentum have also been tested in different bile concentrations and demonstrated to have good bile tolerance when incubated with 3 g L-1 of bile salt. L. fermentum has been found to survive in these conditions further supporting the idea that it can act as a probiotic.
== Notable isotopes == Plutonium-238 has a half-life of 87.74 years and emits alpha particles. Pure 238Pu for radioisotope thermoelectric generators that power some spacecraft is produced by neutron capture on neptunium-237 but plutonium from spent nuclear fuel can contain as much as a few percent 238Pu, originating from 237Np, alpha decay of 242Cm, or (n,2n) reactions. Plutonium-239 has half-life 24,100 years. 239Pu and 241Pu are fissile; meaning their nuclei can split by being bombarded by slow thermal neutrons, releasing energy, gamma radiation and more neutrons. It can therefore sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. 239Pu is synthesized by irradiating uranium-238 with neutrons in a nuclear reactor, then recovered via nuclear reprocessing of the fuel. Further neutron capture produces successively heavier isotopes. Plutonium-240 has a high rate of spontaneous fission, raising the background neutron radiation of plutonium. Plutonium is graded by proportion of 240Pu: weapons grade (<7%), fuel grade (7–19%) and reactor grade (>19%). Lower grades are less suited for bombs and thermal reactors but can fuel fast reactors. Plutonium-241 is fissile, but beta decays with a half-life of 14 years to americium-241. Plutonium-242 is not fissile, nor very fertile (requiring 3 more neutron captures to become fissile); and has a low neutron capture cross section, and a longer half-life than any of the lighter isotopes. Plutonium-244 is the most stable isotope of plutonium, with a half-life of about 80 million years.
In this process, the signal, by interacting with the receptor, starts a series of molecular events within the cell leading to the final effect of the signaling process. Typically the final effect consists in the activation of an ion channel (ligand-gated ion channel) or the initiation of a second messenger system cascade that propagates the signal through the cell. Second messenger systems can amplify or modulate a signal, in which activation of a few receptors results in multiple secondary messengers being activated, thereby amplifying the initial signal (the first messenger). The downstream effects of these signaling pathways may include additional enzymatic activities such as proteolytic cleavage, phosphorylation, methylation, and ubiquitinylation. Signaling molecules can be synthesized from various biosynthetic pathways and released through passive or active transports, or even from cell damage. Each cell is programmed to respond to specific extracellular signal molecules, and is the basis of development, tissue repair, immunity, and homeostasis. Errors in signaling interactions may cause diseases such as cancer, autoimmunity, and diabetes.
== History == Dino Martin, Desi Arnaz Jr. and Billy Hinsche first met in grammar school. Due to the family connections of Dino and Desi, the band's first audition was for Frank Sinatra, who founded and still had an interest in Reprise Records, the recording label for Dean Martin. Though Arnaz, whose father was a famous drummer and who had learned to play drums from close family friend Richard Keith (who played Little Ricky on I Love Lucy) was a skilled drummer in his own right, the group did not play their own instruments on most of their records, instead using top session players, producers and songwriters. Producers included Lee Hazlewood, Billy Strange and Jimmy Bowen. Songwriters whose compositions were recorded by the group included Hazlewood, Red West, David Gates, Boyce and Hart, Clint Ballard Jr. and Bonner & Gordon. Dino, Desi & Billy's best known songs were "I'm a Fool" (1965; U.S. Billboard Hot 100 No. 17; later covered by Alvin and the Chipmunks for their 1965 album Chipmunks à Go-Go) and "Not the Lovin' Kind" (1965; U.S. No. 25). Both were hits for the group before any group member had reached the age of 15. Following this success, in 1965, they toured as an opening act for the Beach Boys. The group also opened for Paul Revere & the Raiders, Tommy Roe, Sam the Sham, the Lovin' Spoonful and the Mamas & the Papas. The band did not have a top 40 hit after 1965, despite releasing records for five years thereafter.
Pyrite usually forms cuboid crystals, sometimes forming in close association to form raspberry-shaped masses called framboids. However, under certain circumstances, it can form anastomosing filaments or T-shaped crystals. Pyrite can also form shapes almost the same as a regular dodecahedron, known as pyritohedra, and this suggests an explanation for the artificial geometrical models found in Europe as early as the 5th century BC.
Sources: en.wikipedia.org
In the evening in Beijing, Trump arrived at Beijing Capital International Airport, where he was greeted by Chinese vice president Han Zheng, Chinese Ambassador to the US Xie Feng, Executive Vice Foreign Minister Ma Zhaoxu, and US Ambassador to China David Perdue, as well as a military honor guard, a military band and around 300 Chinese students waving Chinese and American flags. Trump and his entourage then boarded a motorcade, which later arrived at the Four Seasons Beijing Hotel, while other members of the delegation would stay at the Kempinski Hotel Beijing Yansha Center.
== See also == List of biochemists for people associated with biochemistry. List of biomolecules List of basic biochemistry topics most basic biochemistry topics that should be covered in an encyclopedia, organized by topic. List of chemistry topics, Chemistry basic topics List of biology topics, Biology basic topics List of molecular biology topics List of biochemistry topics
=== Inhalants === Similar to an e-cigarette, a caffeine inhaler may be used to deliver caffeine or a stimulant like guarana by vaping. In 2012, the FDA sent a warning letter to one of the companies marketing an inhaler, expressing concerns for the lack of safety information available about inhaled caffeine.
Dentin ( DEN-tin) (American English) or dentine ( DEN-teen or DEN-TEEN) (British English) (Latin: substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By volume, 45% of dentin consists of the mineral hydroxyapatite, 33% is organic material, and 22% is water. Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel. Dentin rates approximately 3 on the Mohs scale of mineral hardness. There are two main characteristics which distinguish dentin from enamel: firstly, dentin forms throughout life; secondly, dentin is sensitive and can become hypersensitive to changes in temperature due to the sensory function of odontoblasts, especially when enamel recedes and dentin channels become exposed.
7.3.2.1 ABC-type phosphate transporter The expected taxonomic range for this enzyme is: Eukaryota, Bacteria. A bacterial enzyme that interacts with an extracytoplasmic substrate binding protein and mediates the high affinity uptake of phosphate anions. Unlike P-type ATPases, it does not undergo phosphorylation during the transport process. ATP + H2O + phosphate [phosphate - binding protein][side 1] = ADP + phosphate + phosphate [side 2] + [phosphate - binding protein][side 1] 7.3.2.2 ABC-type phosphonate transporter The enzyme, found in bacteria, interacts with an extracytoplasmic substrate binding protein and mediates the import of phosphonate and organophosphate anions. ATP + H2O + phosphonate [phosphonate-binding protein][side 1] = ADP + phosphate + phosphonate [side 2] + [phosphonate- binding protein][side 1] 7.3.2.3 ABC-type sulfate transporter The expected taxonomic range for this enzyme is: Eukaryota, Bacteria. The enzyme from Escherichia coli can interact with either of two periplasmic binding proteins and mediates the high affinity uptake of sulfate and thiosulfate. May also be involved in the uptake of selenite, selenate and possibly molybdate. Does not undergo phosphorylation during the transport. ATP + H2O + sulfate [sulfate - binding protein] [side 1] = ADP + phosphate + sulfate [side 2] + [sulfate - binding protein][side 1] 7.3.2.4 ABC-type nitrate transporter The expected taxonomic range for this enzyme is: Eukaryota, Bacteria.
Sources: en.wikipedia.org
It is a synthetic peptide of 31 amino acids, built to resemble the natural incretin hormone GLP-1. Because of its size and composition it is handled analytically like other therapeutic peptides, using chromatographic and mass spectrometric methods rather than the techniques typical of small organic drugs.
The substitution at position 8 removes the site recognised by dipeptidyl peptidase-4, the enzyme that destroys the native hormone within minutes. The linked lipophilic chain then binds circulating albumin, which further limits access by degradative enzymes and reduces renal loss. Together these features lengthen the effective circulation time considerably.
It acts at the glucagon-like peptide-1 receptor, a G protein-coupled receptor that signals mainly through cyclic AMP. Activation is glucose dependent, meaning insulin release is stimulated more strongly when blood glucose is already elevated. Other tissues carrying the same receptor respond as well, which explains effects beyond glucose control.
It is a glucagon-like peptide-1 receptor agonist, often grouped with the incretin mimetics. Its backbone is modified from the human hormone to resist enzymatic degradation and to bind albumin. These two features distinguish it from the native peptide.