If you have been reading about size-exclusion HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-12-22. Numbers and descriptions here follow the published literature rather than marketing material.
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 relies on pharmacopoeial monographs where they exist, combined with in-house specifications for identity, purity, water content, and counter-ion composition. Reference standards allow calibration across laboratories, although certified materials for every analogue are not universally obtainable. Batch records, chromatograms, and mass spectra form the documentation trail. Regulatory classification varies by jurisdiction and intended use, and research-grade material differs from pharmaceutical-grade material in testing scope. Analytical uncertainty is often expressed as relative standard deviation across replicate injections.
Lyophilised semaglutide is generally held at -20 °C or below, protected from light and moisture. Reconstituted solutions are typically kept at 2-8 °C and used within a defined window because degradation accumulates over time. Repeated freeze-thaw cycles are discouraged, since each cycle can promote aggregation and reduce monomeric content. Room-temperature stability of the solid has been examined in some studies but remains incompletely characterised for long durations, so cold storage is the conservative default for research material.
Degradation proceeds along several parallel routes. Deamidation of asparagine and glutamine residues generates charged variants that shift retention time in chromatographic analysis. Oxidation targets methionine and can be accelerated by trace metals or dissolved oxygen. Non-covalent aggregation produces dimers, oligomers, and larger species that are difficult to reverse. Isomerisation at aspartate residues is slower but measurable under thermal stress. The distribution among these pathways depends on pH, buffer composition, ionic strength, and the presence of excipients such as sugars or surfactants.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C187H291N45O59 | 按主链与 C18 二酸侧链计算 |
| 分子量 | 约 4113.6 道尔顿 | 游离碱形式，随反离子略有差异 |
| 外观 | 白色至类白色冻干粉末 | 具吸湿性，需干燥保存 |
| 溶解性 | 微溶于水，易溶于碱性缓冲液 | 溶解性随 pH 升高而改善 |
| 等电点 | 约 5.4 | 影响缓冲液选择与聚集倾向 |
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.
Quality control for research material typically involves reversed-phase HPLC for purity and identity, mass spectrometry for molecular weight confirmation, and Karl Fischer titration for residual water content. Peptide content is often reported as the mass of actual peptide rather than total powder mass, since counterions and water contribute to the latter. A certificate of analysis should list the method used for each specification. Limits and acceptance criteria vary by supplier and by intended application.
Handling practices center on minimizing contamination and adsorption. Lyophilized peptide tends to accumulate static charge, so weighing is done with antistatic measures and calibrated balances. Reconstitution with appropriate solvent should be gentle, avoiding vigorous vortexing that generates foam and shear. Solutions are typically aliquoted before freezing to reduce repeated temperature cycling. Personal protective equipment and a fume hood are standard for powder handling.
Reconstituted solutions are less stable than the dry powder, and stability depends on concentration, pH, buffer composition, and container material. Low-protein-binding tubes reduce loss of peptide to plastic surfaces. Some researchers add a carrier protein to limit adsorption at low concentrations. The exact shelf life of a given solution is best determined empirically through a stability study rather than assumed from general guidance, because published data cover only a limited set of conditions.
Reverse-phase high-performance liquid chromatography is the standard method for purity assessment, separating the peptide from truncated or oxidized variants. Mass spectrometry confirms molecular mass and detects modifications, while ultraviolet absorbance near 280 nanometers supports concentration measurement through tryptophan and tyrosine residues. Circular dichroism can indicate secondary structure, though the peptide is largely helical in solution, and ion-exchange chromatography resolves charge variants. Purity values above 95 percent are typical for research-grade material. Stability studies track degradation over time under defined conditions.
Lyophilized semaglutide is typically stored at temperatures between minus 20 and minus 80 degrees Celsius for long-term preservation. Short-term storage at 2 to 8 degrees Celsius is common for working aliquots. Repeated freeze-thaw cycles can degrade the peptide and are usually avoided. The molecule is hygroscopic in its solid form, so containers should remain sealed with desiccant. Solutions are less stable than powders and are generally prepared fresh. Light exposure is limited because aromatic residues can undergo photo-oxidation.
Semaglutide dissolves readily in water and in aqueous buffers near neutral pH. Solubility decreases near the isoelectric point, where net charge is minimal. Common laboratory solvents include phosphate-buffered saline and dilute ammonium bicarbonate. Strongly acidic or basic conditions may accelerate hydrolysis. Working concentrations are usually prepared by diluting a concentrated stock. Vial surfaces can adsorb small amounts of peptide at low concentrations, so carrier proteins or low-binding tubes are sometimes used.
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.
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.
=== Social issues === In 2023, Celia Medrano described Bukele's positions on social issues as "flexible" ("flexibles") and a "liquid ideology" ("ideología líquida"). She explained that Bukele changes his positions to appease as many voters as possible and to gauge public opinion on issues such as same-sex marriage and abortion. Bukele stated in 2014 that he was an ally of the LGBT community, supported their civil rights, and opposed discrimination against LGBT individuals. In August 2021, Bukele proposed constitutional reform to legalize same-sex marriage in El Salvador. The proposal would have changed text in the constitution that defined marriage as being between "a man and a woman" ("hombre y mujer") to defining marriage as between "spouses" ("cónyuges"), and would have prohibited discrimination based on sexual orientation. The earliest Bukele's proposal could have gone into effect would have been 2027, since it would have to be approved by two consecutive sessions of the Legislative Assembly. Bukele stated the following month that the proposed constitutional reform would not legalize same-sex marriage, posting on Facebook that the original text would remain intact. In March 2024, Bukele stated that his government would remove "all traces" of "gender ideologies in schools and colleges". In June 2024, Bukele fired 300 bureaucrats from the ministry of culture for promoting policies that were "incompatible" with his emphasis on "patriotic and family values". El Salvador has one of the world's strictest abortion laws, banning it in all circumstances with no exceptions.
OpenAI announces that it will cancel the release of GPT-6.1, the next version of ChatGPT amid ongoing safety concerns. The company also issues an update on recent incidents during which its AI model hacked into other websites. Secretary of State Marco Rubio orders that the Iranian delegation to the UN General Assembly immediately leave the country after overstaying amid stalled negotiations to end the war between both nations. September 29 The US sanctions ten people and entities in various jurisdictions that have acquired weapons and their parts for Iran's Ministry of Defense and Armed Forces Logistics. The X2 roller coaster at Six Flags Magic Mountain closes permanently following a series of lawsuits alleging brain injuries. September 30 The Trump administration concludes the withdrawal of US soldiers from their final bases in Iraq, marking the end of the US-led coalition's war against ISIL. A US defense contract for counter-drone systems is awarded to the Israeli company SMARTSHOOTER. Syria is removed from the US munitions export prohibition list. Defense Secretary Pete Hegseth confirms that the American military will reduce 20% of its generals and admirals. The Office of Religious Affairs is established. The United States Court of Appeals for the Sixth Circuit temporarily halts the execution of Christa Gail Pike, but the U.S. Supreme Court later allows it to proceed. Pike survives two doses of pentobarbital and is hospitalized, prompting Tennessee governor Bill Lee to suspend the state's remaining 2026 execution and order an independent review.
== Details == The Japanese version included the song "Lost On The Moon" as a bonus track, while a special tour version was released in 2004 with a bonus disc, which included live versions of "Barely Breathing" and "Half-Life", alternate versions of "Bite Your Tongue" and "On a High", and a remix of "Reasons For Living". "Half-Life" was also featured in the 2003 film What a Girl Wants.
Taylor was not keen on Thomas taking another trip to the United States, and thought that if he had a permanent address in London he would be able to gain steady work there. She bought a property, 54 Delancey Street, in Camden Town, and in late 1951 Thomas and Caitlin lived in the basement flat. Thomas would describe the flat as his "London house of horror" and did not return there after his 1952 tour of America.
== Administration == The Parliament of India can pass a law to amend the constitution and provide a Legislature with elected Members and a Chief Minister for a union territory, as it has done for Delhi, Jammu and Kashmir and Puducherry. Generally, the President of India appoints an administrator or lieutenant governor for each UT. Delhi, Puducherry, Jammu and Kashmir operate differently from the other five. They were given partial statehood and Delhi was redefined as the National Capital Territory (NCT) and incorporated into a larger area known as the National Capital Region (NCR). Delhi, Puducherry, Jammu and Kashmir have an elected legislative assembly and an executive council of ministers with a partially state-like function. Due to the existence of union territories, many critics have resolved India into a semi-federal nation, as the central and state governments each have their domains and territories of legislation. Union territories of India have special rights and status due to their constitutional formation and development. The status of "union territory" may be assigned to an Indian sub-jurisdiction for reasons such as safeguarding the rights of indigenous cultures, averting political turmoil related to matters of governance, and so on. These union territories could be changed to states in the future for more efficient administrative control. The Constitution does not stipulate how tax revenue is to be devolved to the union territories, unlike for the states.
Sources: en.wikipedia.org
==== Granuloma ==== Drug-induced hepatic granulomas are usually associated with granulomas in other tissues and patients typically have features of systemic vasculitis and hypersensitivity. More than 50 drugs have been implicated.
=== Voting === Voting for the host was open to 203 FIFA member associations. The United bid won with 134 votes, while the Morocco bid received 65 votes. Iran voted for neither of the two bids, while Cuba, Slovenia, and Spain abstained from voting. Ghana had been suspended by FIFA for corruption and was therefore ineligible to vote. Morocco was later selected as a co-host of the 2030 FIFA World Cup, alongside Portugal, Spain, Argentina, Paraguay, and Uruguay.
3-Fluoroalanine, 3,3-difluoroalanine, and 3,3,3-trifluoroalanine can also be synthesised by treating alanine directly with UV-irradiated trifluoromethyl hypofluorite. Optically pure 3-fluoroalanines can be produced through an oxazolidinone intermediate that can be obtained from L- or D-serine. Enzymatic synthesis of alanine with varying degrees of fluorination has been reported, using substrates such as 3-fluoropyruvate and a serine-derivatised sulfamidate.
Degenerative disc disease (DDD) is a medical condition typically brought on by the aging process in which there are anatomic changes to and/or loss of function of one or more intervertebral discs of the spine. DDD can take place with or without symptoms, but is typically identified once symptoms arise. The root cause is thought to be loss of soluble proteins within the fluid contained in the disc, with resultant reduction of the oncotic pressure, which in turn causes loss of fluid volume. Normal downward forces cause the affected disc to lose height, and the distance between vertebrae is reduced. The anulus fibrosus, the tough outer layer of a disc, also weakens. This loss of height causes laxity of the longitudinal ligaments, which may allow anterior, posterior, or lateral shifting of the vertebral bodies, causing facet joint malalignment and arthritis; scoliosis; cervical hyperlordosis; thoracic hyperkyphosis; lumbar hyperlordosis; narrowing of the space available for the spinal tract within the vertebra (spinal stenosis); or narrowing of the space through which a spinal nerve exits (vertebral foramen stenosis), with resultant inflammation and impingement of a spinal nerve, causing a radiculopathy. DDD can cause mild to severe pain, either acute or chronic, near the involved disc, as well as neuropathic pain if an adjacent spinal nerve root is involved. Diagnosis is suspected when typical symptoms and physical findings are present and confirmed by X-rays of the vertebral column.
Benzodiazepines have a unique history in that they were responsible for the largest-ever class-action lawsuit against drug manufacturers in the United Kingdom, involving 14,000 patients and 1,800 law firms that alleged the manufacturers knew of the dependence potential but intentionally withheld this information from doctors. At the same time, 117 general practitioners and 50 health authorities were sued by patients to recover damages for the harmful effects of dependence and withdrawal. This led some doctors to require a signed consent form from their patients and to recommend that all patients be adequately warned of the risks of dependence and withdrawal before starting treatment with benzodiazepines. The court case against the drug manufacturers never reached a verdict; legal aid had been withdrawn and there were allegations that the consultant psychiatrists, the expert witnesses, had a conflict of interest. The court case fell through, at a cost of £30 million, and led to more cautious funding through legal aid for future cases. This made future class action lawsuits less likely to succeed, due to the high cost from financing a smaller number of cases, and increasing charges for losing the case for each person involved. Although antidepressants with anxiolytic properties have been introduced, and there is increasing awareness of the adverse effects of benzodiazepines, prescriptions for short-term anxiety relief have not significantly dropped.
Sources: en.wikipedia.org
Henderson would be executed in the electric chair in the Florida State Prison on April 21, 1993, fourteen months after his arrest. Serial killer David Bullock, suspected in having killed six people with a .38 caliber revolver in one month, from December 5 to January 4, was arrested by the New York Police Department. He would plead guilty to all charges on October 26, commenting "I was in the Christmas spirit. It made me happy." Bullock would be sentenced to 150 years imprisonment. The popular Tamil language film Pokkiri Raja (King of Rogues), an action comedy produced by AVM Saravanan, directed by S. P. Muthuraman and starring Rajinikanth (Shivaji Rao Gaikwad) in two roles, was released in India by Ananda Films. Born: Ireti Osayemi, Nigerian film actress and 2017 Best of Nollywood Award winner for best supporting actress in Ojo Meta (Three Days); in Lagos State Joe Dunthorne, Welsh novelist known for Submarine; in Swansea
Companies linked to the government control much of the domestic media in Singapore. MediaCorp operates most free-to-air television channels and free-to-air radio stations in Singapore. There are a total of six free-to-air TV channels offered by MediaCorp. StarHub TV and Singtel TV also offer IPTV with channels from all around the world. SPH Media Trust, a body with close links to the government, controls most of the newspaper industry in Singapore. Singapore's media industry has sometimes been criticised for being overly regulated and lacking in freedom by human rights groups such as Freedom House. Self-censorship among journalists is said to be common. In 2023, Singapore was ranked 129 on the Press Freedom Index published by Reporters Without Borders, up from 139 the previous year. The Media Development Authority regulates Singaporean media, claiming to balance the demand for choice and protection against offensive and harmful material. Private ownership of TV satellite dishes is banned. Internet in Singapore is provided by state-owned Singtel, partially state-owned Starhub and M1 Limited as well as some other business internet service providers (ISPs) that offer residential service plans of speeds up to 2 Gbit/s as of spring 2015. Equinix (332 participants) and the Singapore Internet Exchange (70 participants) are Internet exchange points where Internet service providers and Content delivery networks exchange Internet traffic between their networks (autonomous systems) in various locations in Singapore.
The balance would, at least theoretically, actually decrease in size with heating to compensate for the lengthening of the hairspring. Through careful adjustment of the placement of the balance screws (brass or gold screws placed in the rim of the balance), a watch could be adjusted to keep time the same at both hot (100 °F (38 °C)) and cold (32 °F (0 °C)) temperatures. Unfortunately, a watch so adjusted would run slow at temperatures between these two. The problem was completely solved through the use of special alloys for the balance and hairspring which were essentially immune to thermal expansion. Such an alloy is used in Hamilton's 992E and 992B. Isochronism was occasionally improved through the use of a stopworks, a system designed to only allow the mainspring to operate within its center (most consistent) range. The most common method of achieving isochronism is through the use of the Breguet overcoil, which places part of the outermost turn of the hairspring in a different plane from the rest of the spring. This allows the hairspring to "breathe" more evenly and symmetrically. Two types of overcoils are found - the gradual overcoil and the Z-Bend. The gradual overcoil is obtained by imposing two gradual twists to the hairspring, forming the rise to the second plane over half the circumference; and the Z-bend does this by imposing two kinks of complementary 45 degree angles, accomplishing a rise to the second plane in about three spring section heights. The second method is done for esthetic reasons and is much more difficult to perform.
=== Cancer === HSP expression plays a pivotal role in cancer identification. Recent discoveries have shown that high concentrations of eHSP can indicate the presence of contentious tumors. Additionally, HSPs have been shown to benefit oncologists in oral cancer diagnosis. Using techniques such as dot immunoassay and ELISA test researchers have been able to determine that HSP-specific phage antibodies could be beneficial in-vitro cancer diagnosis markers. HSPs have also been shown to interact with cancer adaptations such as drug resistance, tumor cell production and lifespan, and the up-regulation and down-regulation of oncomirs.
In adults, wasting (or cachexia) caused by AIDS. Turner syndrome epitomizes the response of non-deficient shortness. At doses 20% higher than those used in GH deficiency, growth accelerates. With several years of treatment the median gain in adult height is about 5-8 cm on this dose. The gains appear to be dose-dependent. It has been used successfully in toddlers with Turner syndrome, as well as in older girls. Short-stature homeobox gene deficiency Chronic kidney failure results in many problems, including growth failure. GH treatment for several years both before and after transplantation may prevent further deceleration of growth and may narrow the height deficit, though even with treatment net adult height loss may be about 10 cm Prader–Willi syndrome, a generally non-hereditary genetic condition, is a case where GH is prescribed for benefits in addition to height. GH is one of the treatment options an experienced endocrinologist may use when treating a child with PWS. GH can help children with PWS in height, weight, body mass, strength, and agility. . Reports have indicated increase of growth rate (especially in the first year of treatment) and a variety of other positive effects, including improved body composition (higher muscle mass, lower fat mass); improved weight management; increased energy and physical activity; improved strength, agility, and endurance; and improved respiratory function. The Prader–Willi Syndrome Association (US) recommends that a sleep study be conducted before initiating GH treatment in a child with PWS.
Sources: en.wikipedia.org
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。
胰岛素释放需要细胞内环腺苷酸与钙信号升高，同时依赖葡萄糖代谢产生的协同信号。血糖水平较低时协同信号不足，分泌增强有限。这一机制在降糖效果与低血糖风险之间提供了缓冲。
白蛋白结合是主要原因，它减少肾小球滤过并保护分子免受蛋白酶降解。序列修饰带来的酶解抵抗同样不可忽略，二者共同作用。脂肪链的疏水性还会影响组织分布，但其对总半衰期的贡献程度仍在研究之中。
Reverse-phase high-performance liquid chromatography with ultraviolet detection is the usual choice, with results reported as area percent. Complementary methods such as size-exclusion chromatography and mass spectrometry are needed because a single separation cannot resolve every impurity class. Purity figures are therefore method dependent and should always be read alongside the technique used.