This is a working overview of size-exclusion HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-09-08 and is reviewed periodically as new material appears.
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.
Receptor binding triggers G protein signaling that raises intracellular cyclic AMP in pancreatic beta cells. Insulin release follows in a glucose-dependent manner, so secretion increases when blood glucose is elevated and diminishes when it is not. The same signaling suppresses glucagon release from alpha cells and slows gastric emptying, which blunts the post-meal glucose rise. In the brain, receptor activation in regions such as the arcuate nucleus is associated with reduced appetite and lower energy intake. How much each of these effects contributes to overall weight change is not fully settled.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | GLP-1 receptor agonist peptide | Mimics endogenous incretin signaling |
| Molecular mass | Approximately 4114 Da | Modified 31-amino-acid backbone |
| Appearance | White to off-white powder | Typical of lyophilized peptide material |
| Solubility | Soluble in water | Behavior depends on salt form and buffer |
| Elimination half-life | About one week | Supported by albumin binding and protease resistance |
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。
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.
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 topology of a β-sheet describes the order of hydrogen-bonded β-strands along the backbone. For example, the flavodoxin fold has a five-stranded, parallel β-sheet with topology 21345; thus, the edge strands are β-strand 2 and β-strand 5 along the backbone. Spelled out explicitly, β-strand 2 is H-bonded to β-strand 1, which is H-bonded to β-strand 3, which is H-bonded to β-strand 4, which is H-bonded to β-strand 5, the other edge strand. In the same system, the Greek key motif described above has a 4123 topology. The secondary structure of a β-sheet can be described roughly by giving the number of strands, their topology, and whether their hydrogen bonds are parallel or antiparallel. β-sheets can be open, meaning that they have two edge strands (as in the flavodoxin fold or the immunoglobulin fold) or they can be closed β-barrels (such as the TIM barrel). β-Barrels are often described by their stagger or shear. Some open β-sheets are very curved and fold over on themselves (as in the SH3 domain) or form horseshoe shapes (as in the ribonuclease inhibitor). Open β-sheets can assemble face-to-face (such as the β-propeller domain or immunoglobulin fold) or edge-to-edge, forming one big β-sheet.
Depending on the column size, CIM monolithic columns are primarily used for the purification or analysis of large biomolecules which are being used for cancer gene therapy, treatment of viral infectious diseases and treatment of genetic diseases. Some types of molecules that can be successfully purified using CIM columns are pDNA, IgM, inter-alpha inhibitors, virus like particles, and diverse viruses; adenoviruses, bacteriophages, feline calicivirus, hepatitis A, lentivirus, influenza A and B, rabies virus, rotavirus, tomato and pepino mosaic virus. Since 2004, BIA Separations has organized and hosted the Monolith Summer School and Symposium (MSS) which takes place every 2 years. MSS was established as there were no dedicated conferences to this technology and to bring together the top international scientists and researchers in the area of monolith chromatography to share their experiences and innovative applications. BIA Separations home page Monolith Events
Caspase recruitment domain-containing protein 11 also known as CARD-containing MAGUK protein 1 (Carma 1) is a protein in the CARD-CC protein family that in humans is encoded by the CARD11 gene. CARD 11 is a membrane associated protein that is found in various human tissues, including the thymus, spleen, liver, and peripheral blood leukocytes. Similarly, CARD 11 is also found in abundance in various lines of cancer cells.
Reactive nitrogen ("Nr"), also known as fixed nitrogen, refers to all forms of nitrogen present in the environment except for molecular nitrogen (N2). While nitrogen is an essential element for life on Earth, molecular nitrogen is comparatively unreactive, and must be converted to other chemical forms via nitrogen fixation before it can be used for growth. Common Nr species include nitrogen oxides (NOx), ammonia (NH3), nitrous oxide (N2O), as well as the anion nitrate (NO−3). Biologically, nitrogen is "fixed" mainly by the microbes (eg., Bacteria and Archaea) of the soil that fix N2 into mainly NH3 but also other species. Legumes, a type of plant in the Fabacae family, are symbionts to some of these microbes that fix N2. NH3 is a building block to Amino acids and proteins amongst other things essential for life. However, just over half of all reactive nitrogen entering the biosphere is attributable to anthropogenic activity such as industrial fertilizer production. While reactive nitrogen is eventually converted back into molecular nitrogen via denitrification, an excess of reactive nitrogen can lead to problems such as eutrophication in marine ecosystems.
Angiogenesis, the formation of new blood vessels, is often critical for tumour cells to survive and grow in nutrient-depleted conditions. Akt is activated downstream of vascular endothelial growth factor (VEGF) in endothelial cells in the lining of blood vessels, promoting survival and growth. Akt also contributes to angiogenesis by activating endothelial nitric oxide synthase (eNOS), which increases production of nitric oxide (NO). This stimulates vasodilation and vascular remodelling. Signaling through the PI3K-Akt pathway increases translation of hypoxia-inducible factor α (HIF1α and HIF2α) transcription factors via mTOR. HIF promotes gene expression of VEGF and glycolytic enzymes, allowing metabolism in oxygen-depleted environments.
Sources: en.wikipedia.org
Epigenetics refers to the study of heritable changes in genetic activities that are distinct from changes in DNA sequences. Epigenetic analysis involves studying DNA-protein interactions, histone modifications, and DNA methylation. Linked-read sequencing has been used for studying DNA methylation patterns by many studies. For example, in 2021, a study investigated the DNA methylation differences in peripheral blood cells between twins, in which one twin had Alzheimer's Disease and the other was cognitively normal. Linked-read sequencing technology allowed researchers to identify more than 3000 differentially methylated regions between these twins discordant for Alzheimer's Disease, and investigation of these differentially methylated regions eventually led to identification of genes enriched in neurodevelopmental processes, neuronal signalling, and immune system functions
SSEP can be used to locate lesions such as peripheral nerve or spinal cord. VEP and BAEP can supplement neuroimaging as part of workups to diagnose diseases such as multiple sclerosis. Short latency EPs such as SSEP, VEP, and BAEP can be used to indicate prognosis for traumatic and anoxic brain injury. Early after anoxic brain injury, no response indicates mortality accurately. In traumatic brain injury, abnormal responses indicates failure to recover from coma. In both types of injury, normal responses may indicate good outcome. Moreover, recovery in responses often indicates clinical recovery. Long and Allen were the first investigators to report the abnormal brainstem auditory evoked potentials (BAEPs) in an alcoholic woman who recovered from acquired central hypoventilation syndrome. These investigators hypothesized that their patient's brainstem was poisoned, but not destroyed, by her chronic alcoholism.
Chemistry... Key to Better Living. Diamond Jubilee Volume: A Record of Chemical Progress During the First 75 Years of the American Chemical Society. American Chemical Society. 1951. Skolnik, Herman; Reese, Kenneth M., eds. (1976). A Century of chemistry: the role of chemists and the American Chemical Society. Washington, D.C.: American Chemical Society. ISBN 978-0841203075. J. J. Bohning 2001. American Chemical Society Founded 1876. ACS, Washington, D.C. Reese, Kenneth M., ed. (2002). The American Chemical Society at 125: A recent history 1976–2001. American Chemical Society. ISBN 978-0-8412-3851-0. ACS website ACS Publications website ACS Chemical & Engineering News ACS Chemical Abstracts Service (CAS) International Year of Chemistry 2011(archived) A Cauldron Bubbles: PubChem and the American Chemical Society — Information Today, June 2005 ACS Chemical Biology WIKI(archived) ACS Chemical Biology Community(archived) ACS Green Chemistry Institute ACS Organic Division Leete Award Gassman Award
Industrial breeding of plants has unintentionally altered how agricultural cultivars associate with their microbiome. In maize, for example, breeding has altered the nitrogen cycling taxa required to the rhizosphere, with more modern lines recruiting less nitrogen fixing taxa and more nitrifiers and denitrifiers. Microbiomes of breeding lines showed that hybrid plants share much of their bacterial community with their parents, such as Cucurbita seeds and apple shoot endophytes. In addition, the proportional contribution of the microbiome from parents to offspring corresponds to the amount of genetic material contributed by each parent during breeding and domestication.
Beauvericin is a depsipeptide with antibiotic and insecticidal effects belonging to the enniatin family. It was isolated from the fungus Beauveria bassiana, but is also produced by several other fungi, including several Fusarium species; it may therefore occur in grain (such as corn, wheat and barley) contaminated with these fungi. Beauvericin is active against Gram-positive bacteria and mycobacteria, and is also capable of inducing programmed cell death in mammals. Chemically, beauvericin is a cyclic hexadepsipeptide with alternating N-methyl-phenylalanyl and D-hydroxy-iso-valeryl residues. Its ion-complexing capability allows beauvericin to transport alkaline earth metal and alkali metal ions across cell membranes. Beauvericin has in vitro fungicidal effects on Candida parapsilosis when used in combination with the antifungal drug ketoconazole at dosages of 0.1 μg/ml. Increased survivability rates and low cytotoxicity were also observed in mouse models.
Sources: en.wikipedia.org
Starch is made of about 70–80% amylopectin by weight, though it varies depending on the source. For example, it ranges from lower percent content in long-grain rice, amylomaize, and russet potatoes to 100% in glutinous rice, waxy potato starch, and waxy corn. Amylopectin is highly branched, being formed of 2,000 to 200,000 glucose units. Its inner chains are formed of 20–24 glucose subunits. Dissolved amylopectin starch has a lower tendency of retrogradation (a partial recrystallization after cooking—a part of the staling process) during storage and cooling. For this main reason, the waxy starches are used in different applications mainly as a thickening agent or stabilizer.
In Ethiopia, the Civil Aviation Accident Prevention and Investigation Bureau of the Ethiopian Civil Aviation Authority (ECAA), which is an agency of the Ministry of Transport and Communications, conducts aircraft accident investigations in Ethiopia or involving Ethiopian aircraft. In France, the agency responsible for investigation of civilian air crashes is the Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA). Its purpose is to establish the circumstances and causes of the accident and to make recommendations for their future avoidance. In Germany, the agency for investigating air crashes is the Federal Bureau of Aircraft Accidents Investigation (BFU). It is an agency of the Federal Ministry of Transport and Digital Infrastructure. The focus of the BFU is to improve safety by determining the causes of accidents and serious incidents and making safety recommendations to prevent recurrence.
In addition to cell signaling, the mTOR pathway also plays a role in beta cell growth leading to insulin secretion. High glucose in the blood begins the process of the mTOR signaling pathway, in which leucine plays an indirect role. The combination of glucose, leucine, and other activators cause mTOR to start signaling for the proliferation of beta cells and the secretion of insulin. Higher concentrations of leucine cause hyperactivity in the mTOR pathway, and S6 kinase is activated leading to inhibition of insulin receptor substrate through serine phosphorylation. In the cell the increased activity of mTOR complex causes eventual inability of beta cells to release insulin and the inhibitory effect of S6 kinase leads to insulin resistance in the cells, contributing to development of type 2 diabetes. Metformin is able to activate AMP kinase which phosphorylates proteins involved in the mTOR pathway, as well as leads to the progression of mTOR complex from its inactive state to its active state. It is suggested that metformin acts as a competitive inhibitor to the amino acid leucine in the mTOR pathway.
Arabinogalactan-proteins (AGPs) are highly glycosylated proteins (glycoproteins) found in the cell walls of plants. Each one consists of a protein with sugar molecules attached (which can account for more than 90% of the total mass). They are members of the wider class of hydroxyproline (Hyp)-rich cell wall glycoproteins, a large and diverse group of glycosylated wall proteins. AGPs have been reported in a wide range of higher plants in seeds, roots, stems, leaves and inflorescences. AGPs account for only a small portion of the cell wall, usually no more than 1% of dry mass of the primary wall. They have also been reported in secretions of cell culture medium of root, leaf, endosperm and embryo tissues, and some exudate producing cell types such as stylar canal cells are capable of producing lavish amounts of AGPs. They are implicated in various aspects of plant growth and development, including root elongation, somatic embryogenesis, hormone responses, xylem differentiation, pollen tube growth and guidance, programmed cell death, cell expansion, salt tolerance, host-pathogen interactions, and cellular signaling. AGPs have attracted considerable attention due to their highly complex structures and potential roles in signalling. In addition, they have industrial and health applications due to their chemical/physical properties (water-holding, adhesion and emulsification).
Sources: en.wikipedia.org
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and cleared quickly. Semaglutide carries a position 8 substitution that blocks that cleavage and a fatty diacid chain that binds albumin. Together these changes extend its circulating half-life to about one week.
Yes. Stimulation of insulin secretion is glucose-dependent, meaning the effect is larger when blood glucose is high and minimal when it is normal. This property separates GLP-1 receptor agonists from agents that drive insulin release regardless of glucose level.
Receptor expression in hypothalamic and brainstem regions is well documented, and reduced energy intake is consistently observed. The relative contribution of central versus peripheral signaling to total weight change is still an open question addressed by ongoing research.
Lower temperatures slow hydrolysis, oxidation and aggregation reactions that degrade the molecule over time. Lyophilised powder is more tolerant than solution, but both benefit from controlled conditions.