The short version of size-exclusion HPLC fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-02-10 and is reviewed periodically as new material appears.
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.
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.
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。
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | 31 amino acids |
| Backbone modification | Aib at position 8 | Blocks DPP-4 cleavage |
| Fatty acid chain | C18 diacid | Supports albumin binding |
| Native half-life | 1 to 2 minutes | Endogenous GLP-1 |
| Analog half-life | Approximately one week | Extended by albumin binding |
Quality control for peptide material focuses on identity, purity, content and the profile of impurities. Common degradants include deamidated and oxidised forms, plus aggregates formed during storage or handling. Forced degradation studies under heat, light, acid and peroxide help define which conditions accelerate change and which analytical methods detect it. Limits for individual impurities are set by pharmacopoeial monographs or manufacturer specifications. How much a given impurity affects biological activity is often uncertain, and conclusions may depend on the assay used.
Solid peptide material is generally kept at reduced temperature to limit degradation. Short-term storage at 2 to 8 degrees Celsius is common, while longer archival storage at minus 20 degrees Celsius or below is typical for lyophilised powder. Vials should remain sealed and protected from light, because ultraviolet exposure can oxidise susceptible residues. Repeated freeze-thaw cycles are avoided, as they promote aggregation and loss of soluble material. Solutions are less stable than solids and are usually prepared close to the time of use.
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.
Quantification and purity assessment rely on separation methods coupled to optical or mass detection. Reversed-phase high-performance liquid chromatography resolves the intact peptide from related impurities and is the standard assay technique. Size-exclusion chromatography measures aggregates, while ion-exchange chromatography separates charge variants produced by deamidation. Mass spectrometry confirms identity and detects mass shifts of a few daltons. In biological matrices, liquid chromatography with tandem mass spectrometry is often used because immunoassays can cross-react with endogenous GLP-1 or with circulating fragments.
As a peptide, semaglutide is sensitive to conditions that break amide bonds or modify side chains. Deamidation of asparagine and glutamine residues, oxidation of methionine and tryptophan, and non-covalent aggregation are the main degradation routes described in published stability work. Rate depends strongly on pH, buffer species, ionic strength, temperature and exposure to light. Formulators therefore choose a defined solution pH and often add excipients such as phosphate buffer, propylene glycol and phenol, each of which plays a separate role in pH control, tonicity or preservation.
Storage guidance for the finished injectable product distinguishes the unused state from the in-use state. Before first use, pens are kept refrigerated between 2 and 8 degrees Celsius, protected from light, and never frozen, since freezing can disrupt the peptide or the device. After first use, label instructions in several markets permit storage at room temperature up to about 30 degrees Celsius for a limited number of days. Solid research-grade material is normally held at or below minus 20 degrees Celsius, often with desiccant, and allowed to equilibrate before opening.
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.
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.
== References == Nordin G, Dybkaer R. Recommendation for term and measurement unit for "HbA1c". Clin Chem Lab Med 2007; 45(8):1081-2. Summary of NPU definition publications René Dybkær: "An Ontology on Property for Physical, Chemical and Biological Systems" Berzell M., "Electronic Healthcare Ontologies: Philosophy, the real world and IT structures"
Glycopeptides are peptides that contain carbohydrate moieties (glycans) covalently attached to the side chains of the amino acid residues that constitute the peptide. Over the past few decades it has been recognised that glycans on cell surface (attached to membrane proteins or lipids) and those bound to proteins (glycoproteins) play a critical role in biology. For example, these constructs have been shown to play important roles in fertilization, the immune system, brain development, the endocrine system, and inflammation. The synthesis of glycopeptides provides biological probes for researchers to elucidate glycan function in nature and products that have useful therapeutic and biotechnological applications.
In 2024, Dalman and colleagues described the remains of a tyrannosaur discovered in 1983 in the Campanian-early Maastrichtian Hall Lake Formation in New Mexico. Reposited at the New Mexico Museum of Natural History and Science, the fossil material (NMMNH P-3698) consists of the right postorbital, right squamosal, left palatine, and an incomplete maxilla from the skull, the left dentary, right splenial, right prearticular, right angular and right articular from the lower jaws, isolated teeth, and chevrons. Some of the bones were briefly mentioned in 1984 as belonging to T. rex, and described in 1986. Lehman and Carpenter (1990) suggested that NMMNH P-3698 belonged to a new tyrannosaurid genus, while Carr and Williamson (2000) disagreed with their claim. Sullivan and Lucas (2015) argued that there is little evidence to support NMMNH P-3698 as a specimen of Tyrannosaurus rex, so they tentatively classified it as cf. Tyrannosaurus sp.; they also considered that the McRae tyrannosaur lived before the Lancian (before 67 million years ago) based on its probable association with the Alamosaurus fossil.
The concentration of naturally produced HMB has been measured in several human body fluids using nuclear magnetic resonance spectroscopy, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry methods. In the blood plasma and cerebrospinal fluid (CSF) of healthy adults, the average molar concentration of HMB has been measured at 4.0 micromolar (μM). The average concentration of HMB in the intramuscular fluid of healthy men of ages 21–23 has been measured at 7.0 μM. In the urine of healthy individuals of any age, the excreted urinary concentration of HMB has been measured in a range of 0–68 micromoles per millimole (μmol/mmol) of creatinine. In the breast milk of healthy lactating women, HMB and L-leucine have been measured in ranges of 42–164 μg/L and 2.1–88.5 mg/L. In comparison, HMB has been detected and measured in the milk of healthy cows at a concentration of <20–29 μg/L. This concentration is far too low to be an adequate dietary source of HMB for obtaining pharmacologically active concentrations of the compound in blood plasma. In a study where participants consumed 2.42 grams of pure HMB-FA while fasting, the average plasma HMB concentration increased from a basal level of 5.1 μM to 408 μM after 30 minutes. At 150 minutes post-ingestion, the average plasma HMB concentration among participants was 275 μM. Abnormal HMB concentrations in urine and blood plasma have been noted in several disease states where it may serve as a diagnostic biomarker, particularly in the case of metabolic disorders.
Sources: en.wikipedia.org
The EU, the United Kingdom, Norway, and Canada have united behind Denmark, and condemned the US threats. The European Commission president Ursula von der Leyen said that the EU stands in "full solidarity with Denmark and the people of Greenland" against US threats. EU Defence Commissioner Andrius Kubilius warned that it would be the end of NATO if the US invaded Greenland and said that EU members would be under obligation to come to Denmark's assistance. European countries have united behind Denmark, emphasising that Greenland belongs to its people, not to the United States. European Council president António Costa said the EU would support Greenland and Denmark when needed and that the EU would not accept violations of international law. European allies said they are working on a plan to support Denmark. EU lawmakers have called for freezing a proposed trade deal with the US. A joint statement, dated 6 January 2026, by President Emmanuel Macron of France, Chancellor Friedrich Merz of Germany, Prime Minister Giorgia Meloni of Italy, Prime Minister Donald Tusk of Poland, Prime Minister Pedro Sánchez of Spain, Prime Minister Keir Starmer of the United Kingdom and Prime Minister Mette Frederiksen of Denmark emphasised "sovereignty, territorial integrity and the inviolability of borders" and said that "Greenland belongs to its people. It is for Denmark and Greenland, and them only, to decide on matters concerning Denmark and Greenland." A joint statement by foreign ministers of the Nordic countries have echoed the same message.
== Sources == Do6a is a venom peptide synthesized by D. occidentalis species of velvet ant, also known as red velvet ant, cow killer, cow ant, and eastern velvet ant. It is postulated to be the most abundant venom peptide in D. occidentalis venom, being 1-3 orders of magnitude more abundant than other Drosophila targeting components; Do10a, Do12a, and Do13a. Despite the title of "ant", the Dasymutilla genus belongs to the Mutillidae wasp family. D. occidentalis do not kill cows, this misleading title comes from their painful sting, which ranks on level 2-3 of 4 on the Schmidt pain index. While the coloration across the genus Dasymutilla varies from white to bright red, an adult D. occidentalis specifically exhibits a distinctive red-and-black aposematic pattern associated with Müllerian mimicry. Males do not possess a stinger but have black wings. Velvet ants are both parasites and prey. Females lay their eggs in nests of other solitary wasp species. Due to their parasitic reproduction cycle, velvet ants require strong defensive strategies. As such, their painful sting is a vital defense.
Furthermore, synthetic platelet-based drug carriers can be loaded with radiosensitizers, which also improve the effectiveness of radiation therapy by increasing tumor susceptibility to radiation-induced damage. Another advantage of platelet-based treatments is their potential to overcome drug resistance—a danger of current cancer treatment options. By acting as sentinels in the bloodstream, platelets naturally take up proteins and genetic material. New treatments can leverage this for real-time biomarker detection and therapeutic monitoring. This application provides the basis for the development of liquid biopsies based on platelets to track disease progression and treatment efficacy. One of the largest constraints is the challenge of mimicking natural platelet interactions with cancer cells without accidentally stimulating cancer growth or metastasis. Natural platelets play a dual role in cancer progression in that they can help the immune system fight tumors but also facilitate cancer cell survival and metastasis by shielding circulating tumor cells from immune attack. Synthetic platelets must be carefully engineered to retain their therapeutic benefits while avoiding unintended interactions that could enhance tumor growth. Additionally, the stability, circulation time, and biodegradability of the synthetic platelets must be optimized for long-term therapeutic action without triggering unwanted immune responses.
== In popular culture == Stuntman and comedian Steve-O has publicly spoken of his involvement as a test subject in an early ractopamine study whose aim was to determine the stress limits of ractopamine saturation in humans. Glover says "Based on how dangerous the study was, the more money you get."
So the presence of effector genes within such regions is suggested to promote their adaptation and diversification when exposed to strong selection pressure. As RIP mutation is traditionally observed to be restricted to repetitive regions and not single copy regions, Fudal et al. suggested that leakage of RIP mutation might occur within a relatively short distance of a RIP-affected repeat. Indeed, this has been reported in N. crassa whereby leakage of RIP was detected in single copy sequences at least 930 bp from the boundary of neighbouring duplicated sequences. To elucidate the mechanism of detection of repeated sequences leading to RIP may allow to understand how the flanking sequences may also be affected.
Sources: en.wikipedia.org
It is a synthetic analog of GLP-1 produced through medicinal chemistry to resist enzymatic degradation. The design goal was longer circulation than the native hormone.
A fatty acid side chain attaches the peptide to serum albumin, which shields it from kidney filtration and protease activity. This interaction is the main reason its circulation time is extended.
No. The native hormone is GLP-1, and semaglutide is an engineered variant with three deliberate structural alterations. It does not appear in unmodified biological sources.
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。