reversed-phase HPLC comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-08-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
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。
市售注射用制剂通常要求在二至八摄氏度冷藏保存，并避免光照与冻结。部分多剂量笔在首次使用后允许在不超过三十摄氏度的环境中存放有限周数，具体期限由辅料与防腐剂体系决定。反复冻融会促进肽链聚集并改变可见颗粒计数，因此应予避免。冻干粉末在干燥、避光、低温条件下更为稳定。溶液配制后宜使用低吸附容器，以减少肽类在塑料或玻璃表面的损失。
Receptor activation occurs at GLP-1 receptors distributed across pancreatic islets, the hypothalamus, and the gastrointestinal tract. Binding triggers G protein signaling that raises cyclic AMP and enhances glucose-dependent insulin release. Because the effect depends on prevailing glucose levels, insulin secretion does not rise when blood sugar is already low. Signaling in the brain and gut also influences appetite and gastric emptying, which is why the compound appears in both metabolic and weight-related research literature.
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.
| Property | Value | Notes |
|---|---|---|
| 保存温度 | 2 至 8 摄氏度 | 避免冻结，部分制剂允许短期室温 |
| 粉末外观 | 白色至类白色固体 | 吸湿后易结块 |
| 纯度检测方法 | 反相高效液相色谱 | 紫外检测，常用 214 纳米 |
| 分子量确认方法 | 液相色谱串联质谱 | 偏差通常以 ppm 表示 |
| 常见降解产物 | 氧化与脱酰胺变体 | 源自甲硫氨酸与天冬酰胺残基 |
Handling guidance for research quantities calls for single-use aliquots, an inert atmosphere where practical, and avoidance of repeated freeze-thaw cycles that accelerate aggregation. Certificates of analysis typically report purity by peak area, water content, counter-ion identity, and residual solvent levels. In the scientific literature the compound is usually described by its full amino acid sequence, its registry number, or its structural class rather than by any proprietary label. Reporting standards vary between journals, and reviewers increasingly request raw chromatograms alongside tabulated purity figures. Whether current purity thresholds are adequate for every experimental context is debated.
Reversed-phase high-performance liquid chromatography with ultraviolet detection is the dominant approach for peptide purity assessment, usually paired with mass spectrometry to confirm molecular mass and sequence. Peptide mapping by enzymatic digestion and tandem mass spectrometry locates modifications such as deamidation and oxidation. Quantitation in plasma matrices can be performed by LC-MS/MS after solid-phase extraction. Method validation follows general guidance on accuracy, precision, linearity, and limits of detection. Comparability of results between laboratories, when no shared reference standard is available, remains an open question.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nm is the standard purity method, reported as area percent. Mass spectrometry, usually with electrospray ionisation, confirms identity and reveals covalent modifications. Size-exclusion chromatography quantifies aggregates and fragments. Peptide mapping after enzymatic digestion localises changes to specific sequence regions. Circular dichroism and infrared spectroscopy report on secondary structure, while light scattering tracks particle formation in liquid formulations. No single technique captures every quality attribute.
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.
GLP-1 receptors are expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises cyclic AMP, enhances glucose-dependent insulin secretion, and suppresses glucagon release when blood glucose is high. Effects on gastric emptying and on hypothalamic appetite circuits reduce energy intake. Because insulin release remains glucose-dependent, the risk of hypoglycemia is low when the drug is used alone. The precise contribution of each pathway to body weight change in humans remains an area of active investigation.
Clinical studies of semaglutide generally measure glycated hemoglobin, fasting plasma glucose, body weight, and composite cardiovascular endpoints. The SUSTAIN program enrolled adults with type 2 diabetes, while the STEP program focused on obesity without diabetes. Administration follows a stepwise escalation schedule designed to limit gastrointestinal effects during the first weeks. Reported outcomes include mean percentage weight change, the proportion of participants reaching defined weight-loss thresholds, and rates of nausea, vomiting, and diarrhea. Long-term data on durability after treatment stops are still limited and remain a topic of ongoing research.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, developed by Novo Nordisk and first approved in 2017 for type 2 diabetes. It belongs to the incretin mimetic class, a group of agents that reproduce the glucose-dependent actions of endogenous GLP-1. The molecule was engineered to resist degradation by dipeptidyl peptidase-4 and to bind serum albumin, extending its half-life from minutes to roughly one week. Approval for chronic weight management followed in 2021, based on large cardiovascular and obesity outcome trials.
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.
=== The 12 nidānas as an early list === Against the view that the 12 link chain is later, Alex Wayman writes "I am convinced that the full twelve members have been in Buddhism since earliest times, just as it is certain that a natural division into the first seven and last five was also known." Bhikkhu Bodhi writes that the suggestions of some scholars the twelvefold formula is a later expansion of a shorter list "remain purely conjectural, misleading, and objectionable on doctrinal and textual grounds." Choong, in his comparative study of SN and SA also writes that the different accounts of dependent origination existed at an early stage and that they are simply different ways of presenting the same teaching which would have been used for different times and with audiences. Choong writes that the various versions of dependent arising "are unlikely to represent a progressive development, with some being earlier and others later" and that "the comparative data revealed here do not provide evidence to support the speculative suggestion that there was just one original (or relatively early) account of the series, from which the other attested accounts developed later."
Feeling that Singer's efforts in Apocalypse to establish a larger world, similar to the MCU, did not meet the standards established by Marvel, St. James noted that unlike Feige's ability to serve as "pseudo-showrunner", Singer is instead "steeped in film and the way movie stories have always been told", so "when it comes time to have Apocalypse dovetail with story threads from the earlier X-Men: First Class", which was directed by Matthew Vaughn, "both Singer's direction and Simon Kinberg's script rely on hackneyed devices and clumsy storytelling", indicating a lack of "the kind of big-picture thinking this sort of mega franchise requires". In his review of Dark Phoenix, Joe Morgenstern of The Wall Street Journal characterized the entire X-Men film series as being a "notoriously erratic franchise". In March 2019, the film rights to Deadpool, the X-Men characters, and the Fantastic Four characters were returned to Marvel Studios following the acquisition of 21st Century Fox by Disney.
== Oxygen-17 == Oxygen-17 (17O) is the rarest of the three stable isotopes of oxygen with a low isotopic abundance of about 0.038% = 380 ppm in terrestrial water and air. Naturally 17O is primarily made by burning hydrogen into helium in the CNO cycle, making it a common isotope in the hydrogen burning zones of stars. As the only stable isotope of oxygen possessing a nuclear spin (+5⁄2) and a favorable characteristic of field-independent relaxation in liquid water, through extreme motional narrowing.17O enables NMR studies tracing oxidative metabolic pathways (i.e. conversion of 17O2 gas to metabolically produced H217O water by oxidative phosphorylation in mitochondria) at high magnetic fields. This is a necessary requirement to overcome the low SNR from low abundance, low gyromagnetic ratio and fast quadrupolar transversal relaxation in contrast to proton/hydrogen, which is the most commonly used nucleus in magnetic resonance. Water used as nuclear reactor coolant is subjected to intense neutron flux. Natural water starts out with 0.038% of 17O; heavy water starts out incidentally enriched to about 0.055% in that isotopes. Further, the neutron flux slowly converts 16O in the cooling water to 17O by neutron capture, increasing its concentration. The neutron flux slowly converts 17O (with much greater cross section) in the cooling water to carbon-14, an undesirable product that can escape to the environment:
The brief existence of an mRNA molecule begins with transcription, and ultimately ends in degradation. During its life, an mRNA molecule may also be processed, edited, and transported prior to translation. Eukaryotic mRNA molecules often require extensive processing and transport, while prokaryotic mRNA molecules do not. A molecule of eukaryotic mRNA and the proteins surrounding it are together called a messenger RNP.
Sources: en.wikipedia.org
=== On Mars === Thiophene derivatives have been detected at nanomole levels in 3.5 billions year old Martian soil sediments (Murray Formation, Pahrump Hills) by the rover Curiosity at Gale crater (Mars) between 2012 and 2017.
The TOPS System (Total Posterior Spine System) is a spinal implant designed to stabilize the lower spine and maintain range of motion following lumbar decompression surgery for spinal stenosis and related conditions. Unlike spinal fusion, which eliminates motion at the treated level, TOPS aims to preserve mobility while providing stability. The device is manufactured by Premia Spine and has received approval for clinical use in the United States by the Food and Drug Administration (FDA) and in the European Union under the CE (Conformité Européenne) marking.
When placed in a nonchiral solvent like water, D-peptides, as well as the larger polypeptide D-proteins, have similar but mirrored properties to the L-peptides and L-proteins with identical sequences. If an L-protein does not require a chaperone or a structural cofactor to fold, its D-enantiomer protein should have a mirror image conformation with respect to the L-protein (Figure 2). A D-enzyme should act on substrates of reverse chirality compared to the L-enzyme with the same sequence. Similarly, if an L-peptide binds to an L-protein, their D-peptide and D-protein counterparts should bind together in a mirrored way. D-peptides also have properties that make them attractive as drugs. D-peptides are less susceptible to be degraded in the stomach or inside cells by proteolysis. D-peptide drugs can, therefore, be taken orally and are effective for a longer period of time. D-peptides are easy to synthesize when compared to many other drugs. In some cases, D-peptides can have a low immunogenic response.
== E == EA – Electron affinity EAD – Electron-activated dissociation ECD – Electron-capture dissociation ECI – Electron capture ionization EDD – Electron-detachment dissociation EI – Electron ionization (or electron impact) EJMS – European Journal of Mass Spectrometry ESA – Electrostatic energy analyzer ES/ESI – Electrospray ionisation ETD – Electron-transfer dissociation eV – Electronvolt
=== Fuels === Another use of cryogenics is cryogenic fuels for rockets with liquid hydrogen as the most widely used example, with liquid methane starting to become more prevalent in recent years. Liquid oxygen (LOX) is even more widely used but as an oxidizer, not a fuel. NASA's workhorse Space Shuttle used cryogenic hydrogen/oxygen propellant as its primary means of getting into orbit. LOX is also widely used with RP-1 kerosene, a non-cryogenic hydrocarbon, such as in the rockets built for the Soviet space program by Sergei Korolev. Russian aircraft manufacturer Tupolev developed a version of its popular design Tu-154 with a cryogenic fuel system, known as the Tu-155. The plane uses a fuel referred to as liquefied natural gas or LNG, and made its first flight in 1989.
Sources: en.wikipedia.org
== Background == Many ancient cultures, including those in Australia, China, Egypt, Greece and India, independently discovered the useful properties of fungi and plants in treating infection. These treatments often worked because many organisms, including many species of mould, naturally produce antibiotic substances. However, ancient practitioners could not precisely identify or isolate the active components in these organisms.
=== Associated conditions === Women with PMOS have an increased risk of a range of metabolic, cardiovascular, reproductive and mental health conditions. The likelihood of developing metabolic disorders is about three to seven times higher than in women without PMOS. Insulin resistance is common, even in lean women with PMOS. Overweight or obese women with PMOS are at higher risk of type 2 diabetes than women without PMOS at the same BMI. Lean women with PMOS do not appear to be at higher risk of developing diabetes. Other metabolic and cardiovascular complications commonly associated with PMOS include:
Palominos have a chestnut base coat color that is genetically modified to a golden shade by a single copy of the incomplete dominant cream gene. Palominos can be distinguished from chestnuts by the lack of true red tones in the coat; even the palest chestnuts have slight red tints to their hair rather than gold. The eyes of chestnuts are usually dark brown, while those of a palomino are sometimes a slightly lighter amber. Some color breed registries that promote palomino coloring have accepted flaxen chestnuts because registration is based on a physical description rather than a genetic identity. Cremellos have a chestnut base coat and homozygous (two copies) for the cream gene. They have a cream-colored coat, blue eyes and lightly pigmented pink skin. Red duns have a chestnut base coat with the dun gene (one or two copies). Their body color is pale, dusty tan shade that resembles the light undercoat color of a body-clipped chestnut but with a bold, dark dorsal stripe in dark red, a red mane, tail and legs. They may have additional primitive markings, which distinguish a red dun from a light or body-clipped chestnut. Gold champagnes have a chestnut base coat with the champagne gene (one or two copies). They resemble a palomino, or they may be an all-over apricot shade, but can be distinguished from other colors by amber or green eyes and lightened skin color with freckling. Red or "strawberry" roans have a chestnut base coat with the classic roan gene (one or two copies). A skewbald, "chestnut pinto" or "sorrel Paint" is a pinto horse with chestnut and white patches.
Differences in ritual and theology, such as the use of unleavened bread and the Filioque clause, as well as divergences in ecclesiology—plenitudo potestatis versus the authority of Ecumenical Councils—and issues of mutual respect, contributed to the separation of Western Christianity from Eastern Christianity. This separation began by 597 and culminated in 1054 during the East–West Schism.
Retinoic acids tretinoin (all-trans-retinoic acid) and isotretinoin (13-cis-retinoic acid) are prescription medications used to treat moderate to severe cystic acne and acne not responsive to other treatments. Tretinoin is usually applied as a skin cream to the face after cleansing to remove make-up and skin oils, while isotretinoin is taken orally. Tretinoin and isotretinoin act by binding to two nuclear receptor families within keratinocytes: the retinoic acid receptors (RAR) and the retinoid X receptors (RXR). These events contribute to the normalization of follicular keratinization and decreased cohesiveness of keratinocytes, resulting in reduced follicular occlusion and microcomedone formation. The retinoid-receptor complex competes for coactivator proteins of AP-1, a key transcription factor involved in inflammation. Retinoic acid products also reduce sebum secretion, a nutrient source for bacteria, from facial pores. These drugs, when applied topically, are US-designated Pregnancy Category C (animal reproduction studies have shown an adverse effect on the fetus), and should not be used by pregnant women or women who are anticipating becoming pregnant. Many countries established a physician- and patient- education pregnancy prevention policy. Trifarotene is a prescription retinoid for the topical treatment acne vulgaris. It functions as a retinoic acid receptor (RAR)-γ agonist.
Sources: en.wikipedia.org
冻融过程中冰晶形成与局部浓度升高会促使肽链发生界面吸附和聚集。聚集不仅降低有效含量，还会改变可见异物与不溶性微粒的计数结果。将溶液分装为单次使用的小体积等份可减少循环次数。
该方法依据疏水性差异分离主峰与相关杂质，对缺失序列、氧化产物和脱酰胺变体具有较好分辨能力。流动相中加入离子对试剂可改善峰形。紫外检测在肽键吸收区工作，灵敏度足以支持常规放行检验。
加速条件可以放大多数化学降解，但聚集与界面诱导的变化对容器、摇动和温度历史更敏感。某些固态转变在短时高温下不一定出现。因此实时稳定性数据仍不可替代，加速结果一般只作为趋势参考。
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.