体积排阻色谱 raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
Development began in the early 2010s with the goal of extending GLP-1 activity beyond the brief window achieved by native peptide infusion. The earliest approved formulation was a subcutaneous injection given once weekly. A later oral tablet pairs the peptide with an absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, usually shortened to SNAC. That carrier lowers local pH and helps the peptide cross gastric tissue. Both routes deliver the same active molecule.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, a gut hormone released after meals. Its backbone retains the GLP-1 sequence but incorporates two substitutions that slow enzymatic breakdown by dipeptidyl peptidase-4. A short polyethylene glycol linker and a C18 fatty diacid are attached to the peptide chain, allowing the molecule to bind serum albumin and remain in circulation far longer than the native hormone. The result is a circulating half-life measured in days rather than the minutes typical of endogenous GLP-1.
| 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 |
Clinical development of this compound followed earlier short-acting GLP-1 analogues that required frequent injection. Once-weekly subcutaneous formulations entered use after 2017, and an oral formulation using a permeation enhancer later became available. The oral version pairs the peptide with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, a carrier that improves uptake across the gastric epithelium. Interest has expanded from glycaemic control into weight management and metabolic liver disease. Regulatory status and approved indications differ between countries, and the product remains subject to ongoing safety monitoring.
Semaglutide is a synthetic peptide that acts as an agonist at the glucagon-like peptide-1 receptor. It is a structural analogue of human GLP-1(7-37), modified to resist enzymatic degradation by dipeptidyl peptidase-4. The peptide backbone contains alpha-aminoisobutyric acid at position 8, a substitution that stabilises the helix and slows cleavage. A fatty diacid side chain attached through a linker at lysine 34 promotes binding to serum albumin, which extends the circulating half-life. These two modifications together allow less frequent administration than native GLP-1 requires.
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.
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.
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.
容器与密封系统同样参与稳定性表现。硅油涂层、胶塞材质与顶空氧含量可能改变聚集速率与氧化水平。分析结果因此需要在完整包装形式下评估，而不能仅凭原料药数据推断。法规文件通常要求同时提交批次数据与代表性容器中的稳定性趋势。
关于降解产物的免疫原性风险，文献中仍有讨论空间。体外聚集水平与临床免疫反应之间的定量关系尚未确立。多数公开研究只报告理化指标，缺少长期随访的对应数据。这一问题在生物类似物比对中尤其受到关注。
Invented by Adrien Philippe in 1842 and commercialized by Patek Philippe & Co. in the 1850s, the stem-wind, stem-set movement did away with the watch key which was a necessity for the operation of any pocket watch up to that point. The first stem-wind and stem-set pocket watches were sold during the Great Exhibition in London in 1851 and the first owners of these new kinds of watches were Queen Victoria and Prince Albert. Stem-wind, stem-set movements are the most common type of watch-movement found in both vintage and modern pocket watches. The mainstream transition to the use of stem-wind, stem-set watches occurred at around the same time as the end of the manufacture and use of the fusee watch. Fusee chain-driven timing was replaced with a mainspring of better quality spring steel (commonly known as the "going barrel") allowing for a more even release of power to the escape mechanism. The balance wheel and balance spring provide a separate function: to regulate the timing (or escape) of the movement.
Besides the potential newer effects as antibiotics or anti-cancers, P.arhizus has traditionally been used for wound healing and hemorragic disorders in places such as Italy and regions of Africa. Looking beyond the composition of P.arhizus, the species has a number of confirmed uses as well as theoretical potentials. A traditional use of the fungus is as a dyeing agent (hence "dyeball") of assorted textiles, producing a range of pigments varying in description from yellow to shades of brown. P.arhizus has also has been mentioned for its use in forestry and land restoration as a mycorrhizal agent for inoculation projects, and some online gardening websites mention its positive effects on plant performance.
Radioactive decay results in a reduction of summed rest mass, once the released energy (the disintegration energy) has escaped in some way. Although decay energy is sometimes defined as associated with the difference between the mass of the parent nuclide products and the mass of the decay products, this is true only of rest mass measurements, where some energy has been removed from the product system. This is true because the decay energy must always carry mass with it, wherever it appears (see mass in special relativity) according to the formula E = mc2. The decay energy is initially released as the energy of emitted photons plus the kinetic energy of massive emitted particles (that is, particles that have rest mass). If these particles come to thermal equilibrium with their surroundings and photons are absorbed, then the decay energy is transformed to thermal energy, which retains its mass. Decay energy, therefore, remains associated with a certain measure of the mass of the decay system, called invariant mass, which does not change during the decay, even though the energy of decay is distributed among decay particles. The energy of photons, the kinetic energy of emitted particles, and, later, the thermal energy of the surrounding matter, all contribute to the invariant mass of the system. Thus, while the sum of the rest masses of the particles is not conserved in radioactive decay, the system mass and system invariant mass (and also the system total energy) is conserved throughout any decay process.
==== Intracrine ==== In intracrine signaling, the signaling chemicals are produced inside the cell and bind to cytosolic or nuclear receptors within the cell. This type of signaling sets it apart from the other cell signaling mechanisms such as autocrine signaling. In both autocrine and intracrine signaling, the signal has an effect on the cell that produced it.
=== Alternative medicine === In countries such as China, herbs used alone or with antithyroid medications are used to treat hyperthyroidism. Very low quality evidence suggests that traditional Chinese herbal medications may be beneficial when taken along with routine hyperthyroidism medications; however, there is no reliable evidence to determine the effectiveness of Chinese herbal medications for treating hyperthyroidism.
Sources: en.wikipedia.org
=== Eosin === Eosin is most often used as a counterstain to haematoxylin, imparting a pink or red colour to cytoplasmic material, cell membranes, and some extracellular structures. It also imparts a strong red colour to red blood cells. Eosin may also be used as a counterstain in some variants of Gram staining, and in many other protocols. There are actually two very closely related compounds commonly referred to as eosin. Most often used is eosin Y (also known as eosin Y ws or eosin yellowish); it has a very slightly yellowish cast. The other eosin compound is eosin B (eosin bluish or imperial red); it has a very faint bluish cast. The two dyes are interchangeable, and the use of one or the other is more a matter of preference and tradition.
== See also == List of abbreviations used in medical prescriptions List of medical roots, suffixes and prefixes Medical dictionary Medical slang Abbreviation#Style conventions in English Acronym and initialism#Orthographic styling
"The Sārnāth column may be interpreted, therefore, not only as a glorification of the Buddha's preaching symbolised by the crowning wheel, but also through the cosmological implications of the whole pillar as a symbol of the universal extension of the power of the Buddha's Law as typified by the sun that dominates all space and all time, and simultaneously an emblem of the universal extension of Mauryan imperialism through the Dharma. The whole structure is then a translation of age-old Indian and Asiatic cosmology into artistic terms of essentially foreign origin and dedicated, like all Asoka's monuments, to the glory of Buddhism and the royal house." The largest surviving group of free-standing stone dharmachakras was made much later and far to the east. Eng Jin Ooi and Peter Skilling count at least forty from the Dvaravati culture of present-day Thailand, about twelve of them inscribed, coming mainly from Lopburi, Suphan Buri, Chai Nat, Nakhon Pathom, Ratchaburi, Phetchaburi and Nakhon Sawan. Bands of pearls frame the felloe on either face; between the bands the felloe is usually flat and filled with pattern, and the outer edge carries a design Robert Brown called "foliage growth". The spokes take a form of Greek ionic capital, with three rings before the column and the middle ring banded with pearls. A wheel of this kind stood on an octagonal pillar set on a circular brick base, held by a stone bracket, with lions below it and a deer nearby.
=== Metalloproteins === Metalloproteins are conjugated proteins that are characterized by having one or more metal ions attached to the protein as a prosthetic groups. These metal ions could be iron, zinc, copper, magnesium, etc., and these are very important to the biological functions and its protein activity. Metalloproteins are involved in a wide range processes from electron transfer to catalysis. Many enzymes are metalloproteins, since metal ions can act as cofactors in chemical reactions. For example, zinc ions can be associated with enzymes that are responsible for gene expression. Moreover, metalloproteins containing iron often are involved in oxygen transport and redox reactions. In this way, the presence of metal ions allows these proteins to perform certain tasks that would not be possible with amino acids alone.
Franz Joseph I or Francis Joseph I (German: Franz Joseph Karl [fʁants ˈjoːzɛf ˈkaʁl]; Hungarian: Ferenc József Károly [ˈfɛrɛnt͡s ˈjoːʒɛf ˈkaːroj]; 18 August 1830 – 21 November 1916) was Emperor of Austria, King of Hungary, and the ruler of the other states of the Habsburg monarchy from 2 December 1848 until his death in 1916. In the early part of his reign, his realms and territories were referred to as the Austrian Empire, but in 1867 they were reconstituted as the dual monarchy of Austria-Hungary. From 1 May 1850 to 24 August 1866, he was also president of the German Confederation. In December 1848, Franz Joseph's uncle Emperor Ferdinand I abdicated the throne at Olomouc as part of Minister President Felix zu Schwarzenberg's plan to end the Hungarian Revolution of 1848. Franz Joseph then ascended to the throne at the age of eighteen. In 1854, he married his first cousin Duchess Elisabeth in Bavaria, with whom he had four children: Sophie, Gisela, Rudolf, and Marie Valerie. Largely considered a reactionary, Franz Joseph spent his early reign resisting constitutionalism in his domains. The Austrian Empire was forced to cede its influence over Tuscany and most of its claim to Lombardy–Venetia to the Kingdom of Sardinia, following the Second Italian War of Independence in 1859 and the Third Italian War of Independence in 1866.
Sources: en.wikipedia.org
==== Late onset ==== Late-onset Alzheimer's is about 70% heritable. Most cases of Alzheimer's are not familial, and so they are termed sporadic Alzheimer's disease. Of the cases of sporadic Alzheimer's disease, most are classified as late onset where they are developed after the age of 65 years. The strongest genetic risk factor for sporadic Alzheimer's disease is APOEε4. APOEε4 is one of the three major alleles of apolipoprotein E (APOE). APOE plays a major role in lipid-binding proteins in lipoprotein particles and the ε4 allele disrupts this function. Between 40% and 80% of people with Alzheimer's disease possess at least one APOEε4 allele. The APOEε4 allele increases the risk of the disease by three times in heterozygotes and by 15 times in homozygotes. Like many human diseases, environmental effects and genetic modifiers result in incomplete penetrance. For example, Nigerian Yoruba people do not show the relationship between the dose of APOEε4 and incidence or age-of-onset for Alzheimer's disease seen in other human populations.
==== Lamarckian inheritance ==== Similarly, his experiments with Wilfred Eade Agar to test William McDougall's supposed demonstration of Lamarckian inheritance of training in rats were negative and showed the inadequacy of McDougall's controls, the first results being published in 1935.
In plant anatomy, tissues are categorized broadly into three tissue systems: the epidermis, the ground tissue, and the vascular tissue. Epidermis – Cells forming the outer surface of the leaves and of the young plant body. Vascular tissue – The primary components of vascular tissue are the xylem and phloem. These transport fluids and nutrients internally. Ground tissue – Ground tissue is less differentiated than other tissues. Ground tissue manufactures nutrients by photosynthesis and stores reserve nutrients. Plant tissues can also be divided differently into two types:
== Function == The product of this gene belongs to a small family of adaptor proteins that are known to interact with a number of receptor tyrosine kinases and signaling molecules. This gene encodes a growth factor receptor-binding protein that interacts with insulin receptors and insulin-like growth-factor receptors (e.g., IGF1R and IGF2R). Overexpression of some isoforms of the encoded protein inhibits tyrosine kinase activity and results in growth suppression. This gene is imprinted in a highly isoform- and tissue-specific manner. Alternatively spliced transcript variants encoding different isoforms have been identified.
=== Eyes === Isotretinoin and other retinoids are well known to affect the eyes. Dry eyes are very common during treatment and is caused by isotretinoin's apoptotic effect on the meibomian glands. Some people develop contact lens intolerance as a result. In some people, these changes are long-lasting or irreversible and represent Meibomian Gland Dysfunction (MGD). Other common effects on the eyes include inflammation of the eyelid (blepharitis), red eye caused by conjunctivitis and irritation of the eye. More rare ocular side effects include blurred vision, decreased night vision (which may be permanent), colour blindness, development of corneal opacities, inflammation of the cornea (keratitis), swelling of the optic disk (papilloedema, associated with IIH), photophobia and other visual disturbances.
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.
Native GLP-1 is degraded within minutes by circulating enzymes. The synthetic version carries substitutions at positions that block enzymatic cleavage, plus a fatty acid side chain that promotes albumin binding. These two changes together extend circulation time from minutes to roughly a week.