If you have been reading about Reverse-phase 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.
Last reviewed on 2025-09-11. Where a claim depends on a specific study, the study is described rather than over-claimed.
Serum protein binding dominates the pharmacokinetic profile. The attached chain associates strongly with albumin, shielding the peptide from enzymatic attack and slowing filtration by the kidney. This interaction extends the circulation half-life to roughly one week in humans, which supports weekly administration intervals. An oral version pairs the peptide with an absorption enhancer that transiently alters gastric epithelium, permitting limited uptake; bioavailability by that route is substantially lower than by injection.
Semaglutide belongs to the glucagon-like peptide-1 receptor agonist class, a group of synthetic peptides that imitate an incretin hormone released by intestinal L cells after food intake. Native GLP-1 circulates for only a few minutes because dipeptidyl peptidase-4 cleaves it rapidly. The hormone acts on pancreatic islets, the gastrointestinal tract, and several brain regions. Because the natural peptide is short-lived, development work concentrated on analogues that keep receptor activity while resisting enzymatic breakdown and renal clearance.
The semaglutide sequence is a 31-residue analogue of human GLP-1, altered at three positions relative to the parent hormone. Aminoisobutyric acid replaces alanine at position 8, arginine replaces lysine at position 34, and a lipophilic diacid is attached to lysine 26 through a short linker. These features are reported consistently in the structural literature. The position 8 substitution blocks recognition by dipeptidyl peptidase-4, while the attached chain drives strong, reversible association with a carrier protein in blood.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide, GLP-1 receptor agonist | 31 amino acid residues |
| Molecular formula | C187H291N45O59 | free peptide, no counter-ion |
| Approximate mass | 4114 Da | matches theoretical value |
| Receptor target | Glucagon-like peptide-1 receptor | Gs-coupled, cyclic AMP pathway |
| Circulation half-life | About one week in humans | extended by albumin association |
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.
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。
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。
== External links == Current and future therapeutic strategies for metastatic ACC (AdrenoCortical Carcinomas) (Video with Univ.-Prof. Dr. med. Martin Fassnacht, University Clinic, Wuerzburg) Application of mitotane therapy in ACC, AdrenoCortical Carcinomas (Video with Prof. Massimo Terzolo, University of Turin) European Society of Endocrinology clinical practice guidelines on the management of adrenal incidentalomas, in collaboration with the European Network for the Study of Adrenal Tumors (European Journal of Endocrinology, Volume 189, Issue 1, July 2023, Pages G1–G42) European Society of Endocrinology Clinical Practice Guidelines on the management of adrenocortical carcinoma in adults, in collaboration with the European Network for the Study of Adrenal Tumors (European Journal of Endocrinology. 2018 Oct 1;179(4):G1-G46.
== Mechanism == The interfacing mechanism is contained inside a common EI source, like that found in any GC-MS system. The liquid phase from a nano HPLC column is admitted from the capillary column port, where the connection tubing and the nebulizer are first introduced and sealed to prevent vacuum loss. The mechanism is based on the formation of an aerosol in high-vacuum conditions, followed by a quick droplet desolvation and final vaporization of the solute prior to the ionization. The completion of the process is quick and complete and reduces chances of thermal decomposition as reported in the Figure, where a scheme of the interface is shown. The core of the interface is represented by the micro-nebulizer. The nebulizer tip protrudes into the ion source so that the spray expansion is completely contained inside the ion volume. The eluate emerges as liquid phase at a flow rate of 300-500 nL/min, and any premature in-tube solvent evaporation is prevented by a convenient thermal insulation of the nebulizer and the connecting tubing from the surrounding source heat. The high temperature of the ion source, between 300 and 400°C, has a double function: to compensate for the latent heat of vaporization during the droplet desolvation, and to convert the solute into the gas phase. If all components of this simple interface are correctly placed and sized, then each substance separated by the nano-column is smoothly converted into the gas phase, the peak profile is nicely reproduced, and high quality mass spectra are generated.
=== Esophageal dysmotility === Presents as a sensation of food getting stuck (dysphagia) in the mid- or lower esophagus, atypical chest pain, or cough. People often state they must drink liquids to swallow solid food. This motility problem results from atrophy of the gastrointestinal tract wall smooth muscle. This change may occur with or without pathologic evidence of significant tissue fibrosis.
Pre-workout is a generic term for a range of bodybuilding supplement products used by athletes and weightlifters to enhance athletic performance. Supplements are taken to increase endurance, energy, and focus during a workout. Pre-workout supplements contain a variety of ingredients such as caffeine and creatine, differing by capsule or powder products. The first pre-workout product entered the market in 1982, and since then the category has grown in use. Some pre-workout products contain ingredients linked to adverse effects. Although these products are not regulated, the Food and Drug Administration (FDA) warns consumers to be cautious when consuming them.
=== May 2009 === On 18 May 2009, the SENSEX surged up 2,110.79 points to close at 14,285.21, from its previous closing of 12,174.42, for its largest single day rally. Less than a month later, on 4 June 2009, the SENSEX would cross the 15,000 mark. However, the SENSEX remained volatile during the summer of 2009. The SENSEX plunged by 869.65 points on 6 July 2009, the day of Union Budget presentation in Parliament on concerns over high fiscal deficit. This was the biggest Budget-day loss for the index. On 17 August 2009, the SENSEX lost 626.71 points. Once again, the SENSEX would recover from the volatility. On 7 September 2009, the SENSEX crossed the 16,000 mark, closing at 16,016.32 points. The index would gain 3,000 points over the next 12 months, as the SENSEX crossed the 19,000 mark on 13 September 2010, closing at 19,208.33 points.
Sources: en.wikipedia.org
Kampo or Kanpō medicine (漢方医学, Kanpō igaku), often known simply as Kanpō (漢方; Japanese medicine) literally means "method from the Han period of Chinese history, but took on specific Japanese characteristics during the Edo period of Japanese history after 1600. One authority writes that Kampo medicine is not the same as modern traditional Chinese medicine (TCM). Japanese Kampo favors diagnostic methods that directly relate the symptoms to the therapy, rather than speculative concepts of traditional philosophy, such as Yin and Yang and the theory of the five elements. Under modern Japanese medical law, it is possible for doctors to perform acupuncture and massage, but because there is a separate law regarding acupuncture and massage, these treatments are mainly performed by massage therapists, acupuncturists, and moxibustion practitioners.
Byzantine music is eclectically descended from early Christian plainsong, Jewish music, and a variety of ancient music; its exact connections to ancient Greek music remain uncertain. It included both sacred and secular traditions, but the latter is little known, whereas the former remains the central music of Eastern Orthodox liturgy into the 21st century. The empire's church music, known as Byzantine chant, was exclusively unaccompanied monodic vocal music, sung in Greek. From the 8th century, chant melodies were governed by the Oktōēchos framework, a set of eight modes—echos (ἦχος; lit. 'sound')—which each provide predetermined motivic formulae for composition. These formulae were chosen for proper text stress and occasionally for text painting, then collated through centonisation into hymns or psalms. Byzantine chant was central to the Byzantine Rite; the earliest music was not notated, including early monostrophic short hymns like the troparion. Proto-Ekphonetic notation (9th century onwards) marked simple recitation patterns. The neumatic Palaeo-Byzantine notation system emerged in the 10th century, and the Middle Byzantine "Round Notation" from the mid-12th century onwards is the first fully diastematic scheme. Several major forms developed alongside well-known composers: the long kontakion (5th century onwards), popularised by Romanos the Melodist; the also-extensive kanōn (late 7th century onwards), developed by Andrew of Crete; and the shorter sticheron (at least 8th century onwards), championed by Kassia.
=== Toxins === The leaves, stem, and green unripe fruit of the tomato plant contain small amounts of the alkaloid tomatine. They contain small amounts of solanine, a toxic alkaloid found in larger amounts in potato leaves and other members of the nightshade family. Tomato plants can be toxic to dogs if they eat large amounts of the fruit, or chew plant material. Small amounts of tomato foliage are sometimes used for flavoring, and the green fruit of unripe red tomato varieties is sometimes used for cooking, particularly as fried green tomatoes.
=== Plasma or whole blood === In this article, all values (except the ones listed below) denote blood plasma concentration, which is approximately 60–100% larger than the actual blood concentration if the amount inside red blood cells (RBCs) is negligible. The precise factor depends on hematocrit as well as amount inside RBCs. Exceptions are mainly those values that denote total blood concentration, and in this article they are:
== Applications == The aldehyde tag is a technique which recently found increased application because of the introduction of bioorthogonal chemical reporters. Bioorthogonal agents contain functional groups such as azides or cyclooctynes for coupling which are not naturally found in the cell. Due to their foreignness, they seem inert and do not disrupt the native metabolism, Fig. 3 gives an overview of possible labeling methods for formylglycine. For example, it can be coupled to probes such as biotin or a protein tag like Flag that are useful for purification and detection. Furthermore, fluorophores can be directly conjugated for live cell imaging. The conjugation of polyethylene glycol (PEG) chains to potential drug candidates extends the stability against proteases in body fluids and at the same time reduces renal clearance and immunogenicity. The first application described here, deals with the formation of protein-protein conjugates through bioorthogonal probes. Since, the aldehyde tag is strictly speaking not a true bioorthogonal agent as it can be found in various metabolites, it can cause cross reactions during protein labeling. However, coupling bioorthogonal probes such as azides or cyclooctynes can be applied to overcome this obstacle. As a second application, the coupling of glycan moieties to proteins is presented here. It can be utilised in the strategy of chemically introduced glycosylation patterns.
Sources: en.wikipedia.org
=== Ferromagnetic and ferroelectric effects === The small size of nanoparticles affects their magnetic and electric properties. The ferromagnetic materials in the micrometer range is a good example: widely used in magnetic recording media, for the stability of their magnetization state, those particles smaller than 10 nm are unstable and can change their state (flip) as the result of thermal energy at ordinary temperatures, thus making them unsuitable for that application.
To begin industrial action for an "employee claim" it must be against a single-business enterprise, rather than multiple employers, it cannot even be part of so-called "pattern bargaining" seeking the same agreements across different enterprises, and it must not be taken before an enterprise agreement has expired. The union must get permission from the FWC to do a protected action ballot, and the FWC must grant an order where the union has a majority support determination and is "genuinely trying to reach an agreement" by negotiation. The ballot must state what kinds of action are proposed, and be overseen by the Australian Electoral Commission or an independent agent, and over 50% must turn out to vote, with over 50% being in favour of action. A union then must then give notice of three days to the employer, and start action within 30 days, or get an extension for another 30 days from the FWC, though action may continue indefinitely until there is agreement or the bargaining period is terminated. Protected industrial action is immune from liability in tort, so long as there is no personal injury, property damage or defamation. However, if industrial action is taken that is unprotected, the FWC must issue a "stop order", which may be backed by an injunction of the Federal Court, and ultimately sanctions for contempt of court including prison. There is a four-hour pay penalty for unprotected action, and by law workers may not be paid during industrial action.
=== Ornithine decarboxylase === Ornithine decarboxylase (ODC), is a labile protein that is the first rate-limiting enzyme in polyamine biosynthesis. Its degradation is regulated by antizyme that is induced by polyamine production. NQO1 has been shown to stabilize the degradation of ODC by binding to it and protecting it from 20S proteasomal degradation.
On 25 August, Israel began strikes in southern Lebanon against Hezbollah targets. Israel framed its strikes as "preemptive". Hezbollah said that it fired over 320 Katyusha rockets to IDF sites in northern Israel and the Golan Heights as the first phase of response to the assassination of Fuad Shukr. A woman was slightly injured due to sharpnel from the attack in Acre. Some homes were also damaged in Northern Israel. Israel sent a hundred fighter jets during its operations. Israeli Defense Minister Yoav Gallant described the strikes as "very successful", stating that "over fifty percent, maybe two-thirds" of Hezbollah's strikes were prevented. An Israeli drone strike in Qasimia in southern Lebanon wounded two people including one Hezbollah militant.
== Experimental chemistry == Meitnerium is the first element on whose chemistry has not yet been investigated. Unambiguous determination of its chemical properties is yet to have been established due to the short half-lives of meitnerium isotopes and a limited number of likely volatile compounds that could be studied on a tiny scale. One of the few meitnerium compounds that are likely to be volatile enough is meitnerium hexafluoride MtF6, as its lighter homolog iridium hexafluoride (IrF6) is volatile above 60°C, so the analogous compound of meitnerium might also be volatile enough; a volatile octafluoride MtF8 might also be possible. For chemical studies on a transactinide, at least four atoms must be produced, the half-life of the isotope used must be ≥1 second, and the rate of production must be at least one atom per week. Even though the half-life of 278Mt, the most stable confirmed isotope, is 4.5 seconds, long enough for chemical studies, another obstacle is the need to increase the rate of production of meitnerium and allow experiments to carry on for weeks or months so that statistically significant results can be obtained. Separation and detection must be carried out continuously to separate out the meitnerium isotopes and have automated systems experiment on the gas-phase and solution chemistry of meitnerium, as the yields for heavier elements are predicted to be smaller than those for lighter elements; some of the separation techniques used for bohrium and hassium could be reused.
Sources: en.wikipedia.org
It is a synthetic peptide of 31 amino acids, built to resemble the natural incretin hormone GLP-1. Because of its size and composition it is handled analytically like other therapeutic peptides, using chromatographic and mass spectrometric methods rather than the techniques typical of small organic drugs.
The substitution at position 8 removes the site recognised by dipeptidyl peptidase-4, the enzyme that destroys the native hormone within minutes. The linked lipophilic chain then binds circulating albumin, which further limits access by degradative enzymes and reduces renal loss. Together these features lengthen the effective circulation time considerably.
It acts at the glucagon-like peptide-1 receptor, a G protein-coupled receptor that signals mainly through cyclic AMP. Activation is glucose dependent, meaning insulin release is stimulated more strongly when blood glucose is already elevated. Other tissues carrying the same receptor respond as well, which explains effects beyond glucose control.
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.