A practical reference on reversed-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-12-10 and is reviewed periodically as new material appears.
Large randomised trials in adults with type 2 diabetes and in adults with obesity have reported reductions in body weight and improvements in several cardiovascular risk markers. One outcome trial found a lower incidence of major adverse cardiovascular events in participants with diabetes and established cardiovascular disease. Gastrointestinal effects such as nausea and vomiting are the most frequently reported adverse events and often diminish over time. Changes in lean body mass during weight loss are an area of ongoing investigation. Effects in adolescents and in pregnancy are less well characterised, and current labelling advises against use during pregnancy.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released after nutrient intake. The molecule contains 31 amino acid residues and differs from the native sequence at several positions. A non-natural residue at position eight resists the enzyme that normally truncates the hormone, while a lysine-linked fatty diacid side chain promotes binding to serum albumin. These two modifications extend the circulating half-life from minutes to roughly one week. The peptide is produced by solid-phase synthesis followed by selective acylation, and its identity and purity are confirmed by spectrometric and chromatographic techniques.
The primary target is the GLP-1 receptor, a class B G protein-coupled receptor expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises intracellular cyclic AMP, which potentiates glucose-dependent insulin secretion and lowers glucagon release when blood glucose is elevated. Signalling in the hypothalamus and brainstem is associated with reduced appetite and slower gastric emptying. Because the insulinotropic effect depends on prevailing glucose levels, the hypoglycaemic risk of the peptide alone is described as low in most study settings. The relative contribution of peripheral and central actions remains an active research question.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Acylated GLP-1 receptor agonist | 31-residue synthetic peptide |
| Molecular formula | C187H291N45O59 | established for the free peptide |
| Appearance | White to off-white powder | as supplied before formulation |
| Solubility | Freely soluble in water | aqueous buffers near neutral pH |
| Typical storage | 2 to 8 degrees Celsius, protected from light | powder and solution forms differ in shelf life |
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.
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.
== Chemistry == The separation of the stereoisomers is one of the easier in organic chemistry and is described in the original patent. It involves "treatment of racemic methadone base with d-(+)-tartaric acid in an acetone/water mixture [which] precipitates almost solely the dextro-methadone levo-tartrate, and the more potent Levomethadone can easily be retrieved from the mother liquor in a high state of optical purity." There is now an asymmetric synthesis available to prepare both levomethadone (R-(−)-methadone) and dextromethadone (S-(+)-methadone).
==== Pregnancy ==== In pregnant women, ACE inhibitors taken during all the trimesters have been reported to cause congenital malformations, stillbirths, and neonatal deaths. Commonly reported fetal abnormalities include hypotension, renal dysplasia, anuria/oliguria, oligohydramnios, intrauterine growth retardation, pulmonary hypoplasia, patent ductus arteriosus, and incomplete ossification of the skull. Overall, about half of newborns exposed to ACE inhibitors are adversely affected, leading to birth defects. ACE inhibitors are ADEC pregnancy category D and should be avoided in women who are likely to become pregnant. In the U.S., ACE inhibitors must be labeled with a boxed warning concerning the risk of birth defects when taken during the second and third trimester. Their use in the first trimester is also associated with a risk of major congenital malformations, particularly affecting the cardiovascular and central nervous systems.
=== Influenza === A study of an outbreak of an (H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 69% had influenza, as compared with 47% of non-smokers. Influenza was also more severe in the smokers; 51% of them lost work days or required bed rest, or both, as compared with 30% of the non-smokers. According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a South Carolina military academy, compared with people who did not smoke, people who smoked heavily (more than 20 cigarettes per day) had 21% more illnesses and 20% more bed rest, people who smoked lightly (20 cigarettes or fewer per day) had 10% more illnesses and 7% more bed rest. The effect of cigarette smoking on epidemic influenza was studied prospectively among 1,811 male college students. Clinical influenza incidence among those who smoked 21 or more cigarettes daily was 21% higher than that of people who did not smoke. Influenza incidence among people who smoked 1 to 20 cigarettes daily was intermediate between those who did not smoke and people who smoked heavily. Surveillance of a 1979 influenza outbreak at a military base for women in Israel revealed that influenza symptoms developed in 60% of the current smokers vs. 42% of the non-smokers. Smoking seems to cause a higher relative influenza risk in older populations than in younger populations.
=== 4 April === The United States government announced a $2.6 billion (USD) aid package to Ukraine which includes ammunition for HIMARS, air defense interceptors, artillery rounds, small arms ammunition, and anti-drone systems.
Chester Fisher died in 1965 at age 84. His sons maintained leadership of the company, with Aiken becoming Chairman and Benjamin becoming president. The youngest son, James Fisher, had the title Senior Vice President. Fisher Scientific Company issued its first public stock in 1965, and that year the company had $58 million in sales and close to a million customer transactions. In 1968 Fisher shares were listed on the New York Stock Exchange. In 1965 the company introduced the Differential Thermalyzer, a differential thermal analysis instrument. It acquired Pfeiffer Glass, Inc. in 1966, a manufacturer of high accuracy volumetric pipettes. The company released the Photometric Titralyzer that year, and a Hem-alyzer in 1968. In 1968, it purchased Massachusetts-based Jarrell-Ash Company, a producer of optical instrumentation, particularly for emission and atomic absorption spectroscopy. It acquired Chicago-based Stansi Scientific Company in 1967, expanding into educational science supplies. In 1976, Fisher Scientific established an Instrument Service Division. Fisher was acquired by Morristown, New Jersey–based Allied Corporation in 1981 for $330 million. At this time Benjamin R. Fisher was Chairman of the company, having gained the position in 1975 upon Aiken's retirement. Operating as a subsidiary of Allied Corporation (and later AlliedSignal Inc., and The Henley Group), Fisher established a Biotechnology Division in 1985. In 1991, The Henley Group sold a majority interest in Fisher through a public stock offering.
Sources: en.wikipedia.org
== Preparation == Esterification is the general name for a chemical reaction in which two reactants (typically an alcohol and an acid) form an ester as the reaction product. Esters are common in organic chemistry and biological materials, and often have a pleasant characteristic, fruity odor. This leads to their extensive use in the fragrance and flavor industry. Ester bonds are also found in many polymers.
Opipramol acts as a high affinity sigma receptor agonist, primarily of the σ1 subtype, but also of the σ2 subtype with lower affinity. In one study of σ1 receptor ligands that also included haloperidol, pentazocine, (+)-3-PPP, ditolylguanidine, dextromethorphan, SKF-10,047 ((±)-alazocine), ifenprodil, progesterone, and others, opipramol showed the highest affinity (Ki = 0.2–0.3) for the guinea pig σ1 receptor of all the tested ligands except haloperidol, which it was approximately equipotent with. The sigma receptor agonism of opipramol is thought to be responsible for its therapeutic benefits against anxiety and depression. Unlike other TCAs, opipramol does not inhibit the reuptake of serotonin or norepinephrine. However, it does act as a high affinity antagonist of the histamine H1 receptor and is a low to moderate affinity antagonist of the dopamine D2, serotonin 5-HT2, and α1-adrenergic receptors. H1 receptor antagonism accounts for its antihistamine effects and associated sedative side effects. In contrast to other TCAs, opipramol has very low affinity for the muscarinic acetylcholine receptors and virtually no anticholinergic effects. Sigma receptors are a set of proteins located in the endoplasmic reticulum. σ1 receptors play key role in potentiating intracellular calcium mobilization thereby acting as sensor or modulator of calcium signaling. Occupancy of σ1 receptors by agonists causes translocation of the receptor from endoplasmic reticulum to peripheral areas (membranes) where the σ1 receptors cause neurotransmitter release.
Peukert further commented that the Federal Republic of Germany never paid reparations to those homosexuals who survived the concentration camps as Paragraph 175 was considered a "healthy law" that was worth keeping, and those homosexual survivors who suffered so much in the concentration camps remained outcasts in post-war Germany. Writing in the 1970s and 1980s at a time when Paragraph 175 was still in effect, Peukert argued that the sort of homophobia which made the Nazi persecution of homosexuals possible, was still very much present in modern West Germany. In the same way, Peukert wrote the "everyday racism" that allowed ordinary people to accept violence directed against "others" in the Third Reich had not disappeared, noting that many ordinary Germans were willing to accept neo-Nazi skinheads beating up Turkish guest workers because they were "foreigners". Crew writing in 1992 wrote that the "recent epidemic of violence against 'foreigners' in both the 'old' and 'new' Länder suggests he may have been right". Peukert wrote that though the Nazis did use an "anti-modernist" disclosure inspired by the theories of Houston Stewart Chamberlain, their solution to the problems of "classical modernity" were not "merely backward-looking". Peukert wrote the attempt to create the volksgemeinschaft was not an effort to return to the pre—industrial age, but rather a purged and cleansed "classical modernity".
The AGA does not recommend extensive pre-procedural testing, including repeated measurements of PT/INR or platelet count, before patients with stable cirrhosis undergo common gastrointestinal procedures. Nor do they suggest the routine use of blood products, such as platelets, for bleeding prevention. Cirrhosis is stable when there are no changes in baseline abnormalities of coagulation lab values. For patients with stable cirrhosis and low platelet count undergoing common low-risk procedures, the AGA does not recommend the routine use of thrombopoietin receptor agonists for bleeding prevention. In hospitalized patients who meet standard guidelines for clot prevention, the AGA suggests standard prevention. The AGA does not recommend routine screening for portal vein thrombosis. If there is a portal vein thrombosis, the AGA suggests treatment by anticoagulation. In the case of cirrhosis with atrial fibrillation, the AGA recommends using anticoagulation over no anticoagulation.
FS−SF → S=SF2 Decomposing to sulfur tetrafluoride and sulfur when heated to 180 °C: 2 S2F2 → SF4 + 3 S Hydrolysis: 2 S2F2 + 2 H2O → SO2 + 3 S + 4 HF Reacting with sulfuric acid at 80 °C: S2F2 + 3 H2SO4 → 5 SO2 + 2 HF + 2 H2O Reacting with sodium hydroxide: 2 S2F2 + 6 NaOH → Na2SO3 + 3 S + 4 NaF + 3 H2O Reacting with oxygen at high pressure, using nitrogen dioxide as a catalyst: 2 S2F2 + 5 O2 → SOF4 + 3 SO3
Sources: en.wikipedia.org
When bacterial cells run out of nutrients, they enter stationary phase and downregulate protein synthesis. Several processes mediate this transition. For instance, in E. coli, 70S ribosomes form 90S dimers upon binding with a small 6.5 kDa protein, ribosome modulation factor RMF. These intermediate ribosome dimers can subsequently bind a hibernation promotion factor (the 10.8 kDa protein, HPF) molecule to form a mature 100S ribosomal particle, in which the dimerization interface is made by the two 30S subunits of the two participating ribosomes. The ribosome dimers represent a hibernation state and are translationally inactive. A third protein that can bind to ribosomes when E. coli cells enter the stationary phase is YfiA (previously known as RaiA). HPF and YfiA are structurally similar, and both proteins can bind to the catalytic A- and P-sites of the ribosome. RMF blocks ribosome binding to mRNA by preventing interaction of the messenger with 16S rRNA. When bound to the ribosomes the C-terminal tail of E. coli YfiA interferes with the binding of RMF, thus preventing dimerization and resulting in the formation of translationally inactive monomeric 70S ribosomes.
7-Eleven has a major presence in the Republic of Korea convenience store market, where it competes with CU, GS25 (formerly LG25), and independent competitors. There are 11,067 7-Eleven stores in the Republic of Korea; with only Japan and Thailand hosting more stores. The first 7-Eleven store in the Republic of Korea opened in May 1989 in Songpa-gu in Seoul with a franchise license under the Lotte Group. In January 2010, Lotte Group acquired the Buy the Way convenience store chain and rebranded its 1,000 stores under the 7-Eleven brand. In 2021, 7-Eleven announced that it would be working with a South Korean nonprofit to create jobs and franchising opportunities for North Korean defectors in South Korea. In January 2022, Lotte acquired the entire stake of Ministop Korea Co. for 313.37 billion won ($263 million). After acquisition, all the Ministop store were gradually converted to 7-Eleven.
The left's view of the USSR is complex. While some leftists regard the USSR as an example of state capitalism or that it was an oligarchical state, other leftists admire Vladimir Lenin and the Russian Revolution. Council communists generally view the USSR as failing to create class consciousness, turning into a corrupt state in which the elite controlled society. Trotskyists believe that the ascendancy of the Stalinist bureaucracy ensured a degenerated or deformed workers' state, where the capitalist elite have been replaced by an unaccountable bureaucratic elite and there is no true democracy or workers' control of industry. In particular, American Trotskyist David North noted that the generation of bureaucrats that rose to power under Stalin's tutelage presided over the stagnation and breakdown of the Soviet Union. Many anti-Stalinist leftists such as anarchists are extremely critical of Soviet authoritarianism and repression. Much of the criticism it receives is centred around massacres in the Soviet Union, the centralized hierarchy present in the USSR and mass political repression as well as violence towards government critics and political dissidents such as other leftists. Critics also point towards its failure to implement any substantial worker cooperatives or implementing worker liberation, as well as corruption and the Soviet authoritarian nature. Anarchists are also critical of the country, labelling the Soviet system as red fascism.
The core structure of immunoliposomes is a lipid bilayer. This lipid bilayer forms a hydrophilic core, which provides stable encapsulation for a therapeutic payload. Common lipids used are phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol. The lipid bilayer is surface modified through conjugation using monoclonal antibodies for specific recognition of the target cells or tissues of interest. The core of the immunoliposome contains the therapeutic payload, which can be anything from small drugs, nucleic acids, peptides, or imaging agents. There are often stabilizers and excipients present for formulation, stability, and functionality. Some include polyethylene glycol (PEG), antioxidants to prevent degradation of lipids, and buffering agents for optimal pH.
== Early life and education == Xing received Chinese traditional private education in his childhood. In 1933, he graduated from Fu Jen Catholic University with a diploma in Chemistry. Xing did his postgraduate work at University of Illinois at Urbana–Champaign under Roger Adams's guidance and obtained a doctorate degree in 1936. Later he went to the Ludwig-Maximilians-Universität München (LMU), conducting research on bufotoxins at Wieland's laboratory.
Sources: en.wikipedia.org
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and neutral endopeptidases. Semaglutide carries a non-natural amino acid at position eight that blocks that cleavage, and a fatty diacid side chain that binds albumin. The result is a much longer duration of action than the native hormone.
The fatty diacid chain associates strongly with serum albumin, which keeps the peptide in circulation and shields it from rapid renal clearance. Bound peptide is released gradually, producing a sustained receptor signal. This mechanism also reduces the peak-to-trough variation seen with shorter-acting analogues.
The balance between peripheral receptor activation and signalling in the central nervous system is not fully resolved. The extent to which slowed gastric emptying accounts for reduced energy intake, compared with direct effects on appetite circuits, is debated. Long-term effects on lean mass and on tissues outside the gut and brain are still under study.
Purity is commonly expressed as the percentage of the main peak relative to all integrated peaks in a reversed-phase chromatogram. Related substances and counter-ions are reported separately. Values obtained with different detectors are not always directly comparable.