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 2025-12-29 and is reviewed periodically as new material appears.
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.
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.
Material described as research-grade is not necessarily manufactured to pharmaceutical standards, and purity figures depend on the method used to obtain them. A certificate of analysis states the measured purity, the analytical technique, and the batch identifier, but the underlying data are not always included. Independent testing by a second laboratory is a common way to confirm identity and purity. Uncertainties remain about how storage history affects long-term stability, and about how well results from one laboratory transfer to another. Documentation of handling conditions supports comparison between batches.
Peptides are sensitive to temperature, light, oxygen, and repeated freeze-thaw cycles. Semaglutide in dry form is generally held at refrigerated temperatures, while reconstituted solutions require a defined short-term storage window. Vials should be kept in secondary packaging to limit photodegradation, and exposure to alkaline conditions is avoided because it accelerates chemical degradation. Adsorption to glass and some plastics can reduce the measured concentration of dilute solutions, so low-binding polypropylene containers are preferred for analytical work. Each transfer step introduces a small risk of contamination, and closed handling practices reduce that risk.
Routine characterisation of the peptide relies on reversed-phase high-performance liquid chromatography, often paired with ultraviolet detection near 214 nanometres. Related substances such as deamidated, oxidised, and truncated sequences elute at characteristic positions and are quantified by area percentage. Electrospray ionisation mass spectrometry confirms the molecular mass and can resolve some closely related variants. Peptide mapping after enzymatic digestion provides sequence-level verification and is useful when a full identity profile is required. Method parameters such as column chemistry, gradient, and mobile-phase pH influence the separation and must be reported alongside results.
| Property | Value | Notes |
|---|---|---|
| Molecular class | 31-amino-acid peptide | Modified glucagon-like peptide-1 analogue |
| Molecular mass | approximately 4114 Da | Calculated for the free peptide backbone |
| Appearance | white to off-white powder | Typical of purified lyophilised peptide batches |
| Solubility class | freely soluble in water | Aqueous solubility improves at slightly alkaline pH |
| Typical storage | -20 degrees Celsius, dry, dark | Protect from repeated freeze-thaw cycles |
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.
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.
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。
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。
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.
Reversed-phase high-performance liquid chromatography is widely used to assess purity and to separate the parent peptide from related substances. Mass spectrometry confirms identity and can resolve modifications that differ by a few daltons. Size-exclusion chromatography detects dimers and higher aggregates, which are relevant to both stability and immunogenicity questions. Peptide mapping with enzymatic digestion locates specific modifications along the sequence. Circular dichroism provides a secondary-structure profile, although it gives limited information about local conformational changes.
According to the American Association of Sleep Medicine, daytime sleepiness is determined as mild, moderate and severe depending on its impact on social life. Daytime sleepiness can be assessed with the Epworth Sleepiness Scale (ESS), a self-reported questionnaire on the propensity to fall asleep or doze off during daytime. Screening tools for OSA comprise the STOP questionnaire, the Berlin questionnaire and the STOP-BANG questionnaire which has been reported as being a powerful tool to detect OSA.
== Structure == The lamina propria is a loose connective tissue, hence it is not as fibrous as the underlying connective tissue of the submucosa. The connective tissue and architecture of the lamina propria is very compressible and elastic, this can be seen in organs that require expansion such as the bladder. The collagen in the lamina propria of elastic organs has been shown to play a major role in mechanical function. In the bladder the collagen composition of its lamina propria allows for structure, tensile strength, and compliance, through complex coiling. It has been suggested that myofibroblasts also reside in the lamina propria of several organs. These cells have characteristics of both smooth muscle and fibroblasts. The lamina propria may also be rich in vascular networks, lymphatic vessels, elastic fibers, and smooth muscle fascicles from the muscularis mucosae. Afferent and efferent nerve endings can be found in the lamina propria as well. Immune cells as well as lymphoid tissue, including lymphoid nodules and capillaries, may be present. Smooth muscle fibers may be in the lamina propria, such as in the intestinal villi. It is practically void of fat cells. Lymphatics penetrate the mucosa and lie below the basement membrane of the epithelium, from there they drain the lamina propria. The fast rate of cell death and regeneration of the epithelium leaves behind many apoptotic cell bodies. These have been found to go into the lamina propria, most of which are inside its macrophages.
Creatine-alpha-ketoglutarate is a salt formed from alpha-ketoglutaric acid (AKG) and creatine. Creatine is a mass-produced fitness supplement that is supposed to increase the user's muscle mass, strength and power. Creatine requires a delivery system for cell uptake. An example is arginine alpha-ketoglutarate. Arginine alpha-ketoglutarate itself is a chemical compound that is supposed to increase the blood flow to muscles and therefore, increase nutrient delivery to muscle cells. Alpha-ketoglutarate (α-KG or AKG) itself is a central molecule in the Krebs cycle that controls the organism's overall citric acid cycle rate. It can improve bone tissue development in the skeletal muscles by decreasing protein catabolism and increasing protein synthesis. The supplement industry has theorized that binding creatine to alpha-ketoglutarate could show significant improvements in creatine delivery and uptake which would ultimately lead to greater improvements in muscle mass and performance. Still relatively new in the fitness industry, more research is needed to test the validity of its effects.
==== Scientific uses ==== The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes due to its extremely low index of refraction. This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy. Helium is a commonly used carrier gas for gas chromatography. The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating. Helium at low temperatures is used in cryogenics and in certain cryogenic applications. As examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain the temperature at 1.9 K (−271.25 °C; −456.25 °F).
== Research == In 2015, the NIH and the Food and Drug Administration (FDA) organized a workshop entitled "Research Directions in Genetically-Mediated Stevens–Johnson Syndrome/Toxic Epidermal Necrolysis".
Sources: en.wikipedia.org
== Medical use == Cyclofenil is used to treat menstrual disturbances and anovulatory infertility caused by insufficiency of the hypothalamic–pituitary–gonadal axis in women. It has also been used to treat menopausal symptoms. The medication is generally used at a dosage of 400 to 600 mg per day.
==== Effects of pH ==== The uranium fraction diagrams in the presence of carbonate illustrate this further: when the pH of a uranium(VI) solution increases, the uranium is converted to a hydrated uranium oxide hydroxide; At high pH, it becomes an anionic hydroxide complex. When carbonate is added, uranium is converted to a series of carbonate complexes if the pH is increased. One effect of these reactions is increased solubility of uranium in the pH range 6 to 8, a fact that has a direct bearing on the long term stability of spent uranium dioxide nuclear fuels.
=== Parathyroid hormone-related protein === Parathyroid hormone-related protein (PTHrP) is a multifunctional peptide that plays a crucial role in calcium homeostasis, vascular regulation, and cellular proliferation. While it is traditionally recognized as a secreted factor that binds to surface receptors, PTHrP also functions as an intracrine regulator within cardiac cells. Its intracrine actions influence myocardial growth, vascular remodeling, and responses to stress, making it a key factor in cardiovascular physiology and pathology.
Through most of the European winter months it was based in Antwerp. In late March 1945 the Rhodesian fighters formed part of the force tasked with protecting the descending Allied paratroopers during Field-Marshal Montgomery's crossing of the Rhine. During April the squadron operated over Hanover and the northern Netherlands. No. 44 Squadron, meanwhile, embarked on bombing raids on targets as far away as Gdynia and Königsberg in East Prussia, as well as towns and cities closer to Berlin such as Dresden, Emden and Leipzig. Its last bombing operation was a raid on the Berghof, Hitler's residence, near Berchtesgaden in Bavaria on 25 April 1945. After Germany surrendered on 7 May, ending the war in Europe, No. 44 Squadron was one of many units selected to evacuate British prisoners of war home from the continent.
=== Internet shutdown === Several human rights organisations including Human Rights Watch (HRW) condemned the al-Burhan-led TMC for shutting down the internet in June 2019. A spokesperson, Shamseldin Kabbashi, stated that the internet would be shut down for a long time because it represented a threat to national security. The move was described by HRW as a "gross violation of human rights". International media saw this as a sign of dictatorship and condemned the act. Many see it as an attempt to hide what al-Burhan's allied militia, known as the Janjaweed, were doing in Khartoum to delay uploading evidence of the violations that took place on 3 June 2019 and in the days that followed.
Sources: en.wikipedia.org
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.
No. It shares high sequence identity but carries non-natural modifications that alter its stability and clearance. The naturally occurring hormone is broken down within minutes, while the synthetic analogue circulates far longer.
Attachment to serum albumin reduces renal filtration of the peptide and shields it from enzymatic breakdown. The consequence is a much longer interval between administrations than unmodified peptides allow. The precise contribution of binding affinity to overall duration is still being quantified.
Different techniques detect different classes of impurities, so a single number does not describe a sample completely. Reversed-phase chromatography resolves related peptides well but can miss inorganic salts, while mass spectrometry confirms mass without quantifying everything present. Comparing results requires knowing which method was used and how it was validated.