purity raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-03-15. Anything still debated is marked as such rather than presented as settled.
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.
Routine characterisation of the peptide relies on reversed-phase high-performance liquid chromatography, often paired with ultraviolet detection near 214 nanometres. Related substances such as deamidated, oxidised, and truncated sequences elute at characteristic positions and are quantified by area percentage. Electrospray ionisation mass spectrometry confirms the molecular mass and can resolve some closely related variants. Peptide mapping after enzymatic digestion provides sequence-level verification and is useful when a full identity profile is required. Method parameters such as column chemistry, gradient, and mobile-phase pH influence the separation and must be reported alongside results.
Material described as research-grade is not necessarily manufactured to pharmaceutical standards, and purity figures depend on the method used to obtain them. A certificate of analysis states the measured purity, the analytical technique, and the batch identifier, but the underlying data are not always included. Independent testing by a second laboratory is a common way to confirm identity and purity. Uncertainties remain about how storage history affects long-term stability, and about how well results from one laboratory transfer to another. Documentation of handling conditions supports comparison between batches.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | typical of a lyophilised peptide preparation |
| Solubility behaviour | pH dependent | lowest near the isoelectric point |
| Storage of bulk material | Minus 20 degrees Celsius or below | protect from light and moisture |
| Storage of unused pen | 2 to 8 degrees Celsius | do not freeze |
| Common assay method | Reversed-phase HPLC | identity, purity and content |
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.
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.
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.
Lyophilized peptide material is typically stored at or below -20 °C, with -80 °C used for longer-term archives. Vials should remain sealed and desiccated because moisture promotes aggregation and hydrolysis. Repeated freeze-thaw cycles are avoided since they can alter peptide conformation and reduce recovery. Once reconstituted, solutions are generally kept at 2-8 °C and used within a defined window. Stability beyond those windows depends on buffer composition and concentration, and exact limits are product-specific rather than universal.
Identity and purity are assessed with reversed-phase high-performance liquid chromatography, which separates the peptide from related impurities by hydrophobicity. Mass spectrometry confirms molecular weight and detects truncation or modification products. Peptide mapping after enzymatic digestion verifies the amino acid sequence. Quantitation is often performed by LC-MS/MS or by immunoassay, and the two approaches can give different values because they measure different things. Method validation parameters such as accuracy, precision, and limit of quantitation are reported alongside results.
Inflammatory abnormalities are a large group of disorders that underlie a vast variety of human diseases. The immune system is often involved with inflammatory disorders, as demonstrated in both allergic reactions and some myopathies, with many immune system disorders resulting in abnormal inflammation. Non-immune diseases with causal origins in inflammatory processes include cancer, atherosclerosis, and ischemic heart disease. Examples of disorders associated with inflammation include:
Charles Brenner (born October 30, 1961) holds the position of Professor of Metabolic Regulation at University of Helsinki, having been recruited with support of the Research Council of Finland. Prior to this, he held the inaugural Alfred E Mann Family Foundation Chair of the Department of Diabetes & Cancer Metabolism at the Beckman Research Institute of the City of Hope National Medical Center and served as the Roy J. Carver Chair and head of biochemistry at the University of Iowa. Brenner is a major contributor in the field of nicotinamide adenine dinucleotide (NAD) metabolism and has developed targeted, quantitative methods for NAD metabolomics. Brenner discovered eukaryotic nicotinamide riboside (NR) kinase and nucleosidase pathways to NAD.
Protein tags are peptide sequences genetically grafted onto a recombinant protein. Tags are attached to proteins for various purposes. They can be added to either end of the target protein, so they are either C-terminus or N-terminus specific or are both C-terminus and N-terminus specific. Some tags are also inserted at sites within the protein of interest; they are known as internal tags. Affinity tags are appended to proteins so that they can be purified from their crude biological source using an affinity technique. Affinity tags include chitin binding protein (CBP), maltose binding protein (MBP), Strep-tag and glutathione-S-transferase (GST). The poly(His) tag is a widely used protein tag, which binds to matrices bearing immobilized metal ions. Solubilization tags are used, especially for recombinant proteins expressed in species such as E. coli, to assist in the proper folding in proteins and keep them from aggregating in inclusion bodies. These tags include thioredoxin (TRX) and poly(NANP). Some affinity tags have a dual role as a solubilization agent, such as MBP and GST. Chromatography tags are used to alter chromatographic properties of the protein to afford different resolution across a particular separation technique. Often, these consist of polyanionic amino acids, such as FLAG-tag or polyglutamate tag. Epitope tags are short peptide sequences which are chosen because high-affinity antibodies can be reliably produced in many different species. These are usually derived from viral genes, which explain their high immunoreactivity.
JINR did not propose a name after their first report claiming synthesis of element 105, which would have been the usual practice. This led LBL to believe that JINR did not have enough experimental data to back their claim. After collecting more data, JINR proposed the name bohrium (Bo) in honor of the Danish nuclear physicist Niels Bohr, a founder of the theories of atomic structure and quantum theory; they soon changed their proposal to nielsbohrium (Ns) to avoid confusion with boron. Another proposed name was dubnium. When LBL first announced their synthesis of element 105, they proposed that the new element be named hahnium (Ha) after the German chemist Otto Hahn, the "father of nuclear chemistry", thus creating an element naming controversy. In the early 1970s, both teams reported synthesis of the next element, element 106, but did not suggest names. JINR suggested establishing an international committee to clarify the discovery criteria. This proposal was accepted in 1974 and a neutral joint group formed. Neither team showed interest in resolving the conflict through a third party, so the leading scientists of LBL—Albert Ghiorso and Glenn Seaborg—traveled to Dubna in 1975 and met with the leading scientists of JINR—Georgy Flerov, Yuri Oganessian, and others—to try to resolve the conflict internally and render the neutral joint group unnecessary; after two hours of discussions, this failed. The joint neutral group never assembled to assess the claims, and the conflict remained unresolved.
Sources: en.wikipedia.org
=== Migraine prophylaxis === Candesartan may be helpful in migraine prevention as it has better tolerability and fewer side effects compared to other first line medications. It has been recommended by multiple guidelines for migraine prophylaxis in adults with different levels of recommendations, however further studies on larger populations are needed.
== Interactions == Products containing multivalent cations, such as aluminium- or magnesium-containing antacids, and products containing calcium, iron, or zinc invariably result in marked reduction of oral absorption of fluoroquinolones. Other drugs that interact with fluoroquinolones include sucralfate, probenecid, cimetidine, theophylline, warfarin, antiviral agents, phenytoin, cyclosporine, rifampin, pyrazinamide, and cycloserine. Administration of quinolone antibiotics to a benzodiazepine-dependent individual can precipitate acute benzodiazepine withdrawal symptoms due to quinolones displacing benzodiazepines from their binding sites. Fluoroquinolones have varying specificity for cytochrome P450, so may have interactions with drugs cleared by those enzymes; the order from most P450-inhibitory to least, is enoxacin > ciprofloxacin > norfloxacin > ofloxacin, levofloxacin, trovafloxacin, gatifloxacin, moxifloxacin.
Enantiopure compounds consist of only one of the two enantiomers. Enantiopurity is of practical importance since such compositions have improved therapeutic efficacy. The switch from a racemic drug to an enantiopure drug is called a chiral switch. In many cases, the enantiomers have distinct effects. One case is that of Propoxyphene. The enantiomeric pair of propoxyphene is separately sold by Eli Lilly and company. One of the partners is dextropropoxyphene, an analgesic agent (Darvon) and the other is called levopropoxyphene, an effective antitussive (Novrad). It is interesting to note that the trade names of the drugs, DARVON and NOVRAD, also reflect the chemical mirror-image relationship. In other cases, there may be no clinical benefit to the patient. In some jurisdictions, single-enantiomer drugs are separately patentable from the racemic mixture. It is possible that only one of the enantiomers is active. Or, it may be that both are active, in which case separating the mixture has no objective benefits, but extends the drug's patentability.
The results of the work at Duke were impressive with one treated bird recovering to the point of being able to fly again. This was followed by the production of clinical-grade alpha-glucosidase in Chinese hamster ovary (CHO) cells and in the milk of transgenic rabbits. This work eventually culminated in the start of clinical trials with the first clinical trial including four babies receiving enzyme from rabbit milk at Erasmus MC Sophia Children's Hospital and three babies receiving enzyme grown in CHO cells at Duke University in 1999. The currently approved Myozyme is manufactured by Genzyme Corp. in Cambridge, Massachusetts. Its development was a complex process. Genzyme first partnered with Pharming Group NV which had managed to produce acid alpha-glucosidase from the milk of transgenic rabbits. They also partnered with a second group based at Duke University using Chinese hamster ovary cells. In 2001, Genzyme acquired Novazyme which was also working on this enzyme. Genzyme also had its product (Myozyme) grown in CHO cells under development. In November 2001, Genzyme chief executive Henri Termeer organised a systematic comparison of the various potential drugs in a mouse model of Pompe disease. It was found that the Duke enzyme was the most efficacious, followed by Myozyme. However, due to easier manufacture of Myozyme, work on the other products was discontinued.
==== 1965 - 1992 ==== Following the assassination of Kennedy in 1963, India-US relations deteriorated gradually. While Kennedy's successor Lyndon B. Johnson sought to maintain relations with India to counter Communist China, he also sought to strengthen ties with Pakistan with the hopes of easing tensions with China and weakening India's growing military buildup as well. Relations then hit an all-time low under the Nixon administration in the early 1970s. Nixon shifted away from the neutral stance which his predecessors had taken towards India-Pakistan hostilities. He established a very close relationship with Pakistan, aiding it militarily and economically, as India, now under the leadership of Indira Gandhi, was leaning towards Soviet Union. He considered Pakistan as a very important ally to counter Soviet influence in the Indian subcontinent and establish ties with China, with whom Pakistan was very close. The frosty personal relationship between Nixon and Indira further contributed to the poor relationship between the two nations. Nixon also harbored sexist and racist sentiments against Indians, describing the empathetic attitude of the American public toward India as a "psychological disorder". During the 1971 Indo-Pakistani War, the US openly supported Pakistan and deployed its aircraft carrier USS Enterprise towards the Bay of Bengal, which was seen as a show of force by the US in support of the West Pakistani forces.
Sources: en.wikipedia.org
Arsenic trioxide, even at low concentrations, causes the degradation of PML/RARα, thereby partially restoring the differentiation of cancerous promyelocytes. Arsenic trioxide activates JNK (c-Jun N-terminal kinase), also known as stress-activated protein kinase, which belongs to the MAPK (mitogen-activated protein kinase) family. These enzymes play a crucial role in signal transduction within the cell. Under normal conditions, JNK is activated by the phosphorylation of threonine and tyrosine residues. However, studies on specific cell lines derived from patients with acute promyelocytic leukemia have demonstrated that this activation also occurs in response to arsenic trioxide. It seems that the activation of JNK leads to the phosphorylation of both anti-apoptotic proteins (Bcl-2, Bcl-Xl) and pro-apoptotic proteins – Bax (Bcl-2-associated X protein), Bak (Bcl-2 homologous killer), and Bid (BH3 interacting domain death agonist) – effectively activating them. Pro-apoptotic proteins contain the BH3 domain, which is responsible for their "death-inducing" activity. They cause the formation of ion channels in the mitochondrial membrane, resulting in the release of the aforementioned apoptotic factors into the cytoplasm. Anti-apoptotic proteins owe their function to a hydrophobic cleft in their spatial structure that binds to the BH3 domain, thereby neutralizing the effects of the "death" proteins. Under normal conditions, the decision for a cell to undergo apoptosis depends on the ratio of pro-apoptotic to anti-apoptotic proteins.
A technique called osteo-odonto-keratoprosthesis (OOKP) uses a staged operation on those who have developed corneal blindness in which a laminated tooth is transplanted to serve as a support for an artificial optical cylinder.
The PAH world hypothesis is a speculative hypothesis that proposes that polycyclic aromatic hydrocarbons (PAHs), known to be abundant in the universe, including in comets, and assumed to be abundant in the primordial soup of the early Earth, played a major role in the origin of life by mediating the synthesis of RNA molecules, leading into the RNA world. However, as yet, the hypothesis is untested.
All other European Union nations voted in favour or abstained: the Netherlands, which voted against a resolution in 2007, voted in favour, as did Finland and Norway, both of which had abstained in 2007, while the Czech Republic, which voted against the resolution in 2007, abstained. The two other states that voted against the resolution were Israel and the United States (both of which voted against in 2007), while as before China was absent for the vote, and Russia abstained. In June 2009, Belgium became the first country in the world to ban: "inert ammunition and armour that contains depleted uranium or any other industrially manufactured uranium." The move followed a unanimous parliamentary vote on the issue on 22 March 2007. The text of the 2007 law allowed for two years to pass until it came into force. In April 2009, the Belgian Senate voted unanimously to restrict investments by Belgian banks into the manufacturers of depleted uranium weapons. In September 2009, the Latin American Parliament passed a resolution calling for a regional moratorium on the use, production and procurement of uranium weapons. It also called on the Parlatino's members to work towards an international uranium weapons treaty. In November 2010 the Irish Senate passed a bill seeking to outlaw depleted uranium weapons, but it lapsed before approval by the Dáil.
Menin is a protein that in humans is encoded by the MEN1 gene. Menin is a putative tumor suppressor associated with multiple endocrine neoplasia type 1 (MEN-1 syndrome) and has autosomal dominant inheritance. Variations in the MEN1 gene can cause pituitary adenomas, hyperparathyroidism, pancreatic neuroendocrine tumors, gastrinoma, and adrenocortical cancers. In vitro studies have shown that menin is localized to the nucleus, possesses two functional nuclear localization signals, and inhibits transcriptional activation by JunD. However, the function of this protein is not known. Two messages have been detected on northern blots but the larger message has not been characterized. Two variants of the shorter transcript have been identified where alternative splicing affects the coding sequence. Five variants where alternative splicing takes place in the 5' UTR have also been identified.
Sources: en.wikipedia.org
Ice formation concentrates solutes and can mechanically stress the peptide or damage the delivery device. Thawing afterwards may leave aggregates that are not visible to the eye. Refrigeration keeps the solution above its freezing point while slowing chemical degradation.
Size-exclusion chromatography is the most common technique, separating monomer from dimer and higher-order species by hydrodynamic volume. It is usually paired with ultraviolet detection and, for trace work, with multi-angle light scattering. Results depend on mobile-phase conditions, so method details matter when comparing datasets.
The detailed degradation profile under real-world temperature excursions and repeated handling is not fully described in the open literature. Relative contributions of photo-degradation versus thermal pathways are also incompletely mapped. Whether specific impurity species carry different biological activity is an open question rather than an established finding.
Different techniques detect different classes of impurities, so a single number does not describe a sample completely. Reversed-phase chromatography resolves related peptides well but can miss inorganic salts, while mass spectrometry confirms mass without quantifying everything present. Comparing results requires knowing which method was used and how it was validated.