Everything below concerns DPP-4 resistance. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-02-20. Numbers and descriptions here follow the published literature rather than marketing material.
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 is a synthetic peptide analog of glucagon-like peptide-1, a hormone released from intestinal L cells after food intake. The molecule is a 31-amino-acid backbone modified at three positions to resist cleavage by dipeptidyl peptidase-4, the enzyme that degrades native GLP-1 within minutes. A lysine residue at position 26 carries a linker and a C18 fatty diacid, which promotes binding to serum albumin and slows renal clearance. These changes extend the circulating half-life from roughly two minutes to about one week in humans.
The sequence incorporates alpha-aminoisobutyric acid at position 8, replacing the alanine found in the natural hormone. This substitution blocks the primary DPP-4 recognition site and contributes most of the enzymatic stability. Albumin binding further protects the peptide and reduces the frequency of administration required to maintain active plasma levels. Because the fatty acid chain increases lipophilicity, the compound is formulated as a solution rather than a simple aqueous buffer. Researchers describe the design as an incremental optimization of earlier GLP-1 analogs rather than a wholly new scaffold.
Reported molecular weight is approximately 4113.6 daltons for the free base, and the peptide is supplied as a lyophilized powder or in buffered liquid form depending on the intended use. It is freely soluble in water when formulated with appropriate excipients, though the unconjugated peptide shows limited stability at neutral pH over long periods. Analytical characterization typically relies on reversed-phase high-performance liquid chromatography and mass spectrometry. Purity specifications for research-grade material commonly exceed ninety-five percent by area. Isotopic and impurity profiles differ between suppliers.
| Property | Value | Notes |
|---|---|---|
| Purity assessment | RP-HPLC, 214 nm | Wavelength affects relative peak areas |
| Identity confirmation | LC-MS/MS | Precursor and fragment ion masses compared |
| Common degradation | Deamidation, oxidation | Amide and methionine residues are main sites |
| Working solution storage | 2-8 °C, short term | Longer holding favours frozen aliquots |
| Adsorption risk | Higher below 1 mg/mL | Glass and plastic surfaces both affected |
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.
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.
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.
Receptor activation follows the canonical Gs pathway: binding increases intracellular cyclic AMP, which promotes protein kinase A activity. In pancreatic beta cells this amplifies glucose-dependent insulin release, so secretion rises when blood glucose is high and changes little when it is low. The same signalling suppresses glucagon release from alpha cells and slows gastric emptying. Receptors in the hypothalamus and brainstem are thought to contribute to reduced appetite and lower energy intake. Which of these effects dominates clinical outcomes remains an area of active study.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released by intestinal L cells after food intake. The natural hormone acts on pancreatic and central receptors but is degraded within minutes by dipeptidyl peptidase-4 and other peptidases. Semaglutide belongs to the class of long-acting GLP-1 receptor agonists, a group distinguished by structural changes that slow breakdown and extend circulation time. Its development followed earlier short-acting analogues and reflects a general strategy in peptide drug design: preserve receptor activity while blocking proteolytic clearance.
Receptor binding triggers G protein signaling that raises intracellular cyclic AMP in pancreatic beta cells. Insulin release follows in a glucose-dependent manner, so secretion increases when blood glucose is elevated and diminishes when it is not. The same signaling suppresses glucagon release from alpha cells and slows gastric emptying, which blunts the post-meal glucose rise. In the brain, receptor activation in regions such as the arcuate nucleus is associated with reduced appetite and lower energy intake. How much each of these effects contributes to overall weight change is not fully settled.
Two structural features account for the prolonged half-life of semaglutide. A modified amino acid at position 8 resists cleavage by dipeptidyl peptidase-4, the enzyme that rapidly degrades native GLP-1. A fatty diacid side chain binds serum albumin, which limits renal clearance and protects the peptide from enzymatic breakdown. These modifications yield a plasma half-life of approximately one week in humans, allowing once-weekly administration. The relationship between plasma concentration and clinical effect varies between individuals, and sources of that variability are still being characterized.
Biochemistry is the study of the chemicals, chemical reactions and interactions that occur in living organisms. Biochemistry is highly interdisciplinary, covering medicinal chemistry, neurochemistry, molecular biology, forensics, plant science and genetics. Neurochemistry is the study of neurochemicals; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system. Inorganic chemistry traditionally was the study of metals and minerals, but is mainly concerned with the structure and behavior of compounds derived from metals and main group elements. The distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub-discipline of organometallic chemistry. Materials chemistry is the preparation, characterization, and understanding of solid state components or devices with a useful current or future function. The field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry like organic chemistry, inorganic chemistry, and crystallography with a focus on fundamental issues that are unique to materials. Primary systems of study include the chemistry of condensed phases (solids, liquids, polymers) and interfaces between different phases. Organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. An organic compound is defined as any compound based on a carbon skeleton.
Xi has pursued an assertive foreign policy, including toward China–United States relations, in the South China Sea, and along the Sino-Indian border dispute. He expanded China's economic and diplomatic presence in Africa and Eurasia through the Belt and Road Initiative. His 2015 meeting with Taiwanese president Ma Ying-jeou, the first between cross-strait leaders since the Chinese Civil War, was followed by deteriorating relations under the Democratic Progressive Party. He oversaw the enactment of the 2020 Hong Kong national security law, which effectively suppressed the city's pro-democracy camp. In 2018, Xi amended the constitution to remove presidential term limits and, upon his re-election in 2023, became the first Chinese president to serve more than two terms. Xi's ideology, known as Xi Jinping Thought, has been incorporated into the party and national constitutions.
on the toxicity findings of publicly-funded academics, whose methods are very heterogeneous, but who test, and often find, toxicity at much lower doses that industry's TG studies); or, a nation may interpret the accepted study's results according to its own criteria. According to OECD Council Decision C(97)186/Final, chemical testing data generated in any OECD member country following OECD Test Guidelines and GLP principles is recognized by other OECD member countries, such as Australia, Canada, Korea, and the USA. This recognition also extends to some non-OECD countries that fully adhere to the mutual acceptance of data (MAD) under OECD Council Decision C(97)114/Final, including Brazil, India, Malaysia, Singapore, and South Africa, as well as Argentina for industrial chemicals, pesticides, and biocides only. In June 2004, the US FDA published a comparison chart of FDA and EPA Good Laboratory Practice (GLP) regulations alongside OECD Principles for GLP, aiding in understanding the key differences and similarities in GLP standards across these regulatory bodies. Note, unlike many countries, the US EPA names its mandated use of the OECD TG, ‘the EPA Test Methods’.
An intein is a "parasitic" segment of a protein that is able to excise itself from the chain of amino acids as they emerge from the ribosome and rejoin the remaining portions with a peptide bond in such a manner that the main protein "backbone" does not fall apart. This is a case of a protein changing its own primary sequence from the sequence originally encoded by the DNA of a gene. Additionally, most inteins contain a homing endonuclease or HEG domain, which is capable of finding a copy of the parent gene that does not include the intein nucleotide sequence. On contact with the intein-free copy, the HEG domain initiates the DNA double-stranded break repair mechanism. This process causes the intein sequence to be copied from the original source gene to the intein-free gene. This is an example of protein directly editing DNA sequence, as well as increasing the sequence's heritable propagation.
The layer lining the medullary cavity of both specimens likely represent endosteal bone deposition, during which new bone matrix is deposited on the inner surface of the cortical bone. The authors also described a partial dentary (FMNH PR 4920) from the Hell Creek Formation and isolated teeth from the Lance Formation as hatchling T. rex and interpret their tooth wear as evidence of consuming relatively large vertebrates. The body length and body mass of the hatchling T. rex (RSKM P2416.82) are estimated to be approximately 75 cm (2.46 ft) and 2.5 kg (5.5 lb) respectively, and those of the hatchling cf. G. libratus (TMP 1981.16.475) are estimated to be approximately 70 cm (2.3 ft) and 2.4 kg (5.3 lb) respectively. On the basis of these body size estimates, Longrich et al. (2026) suggested that the clutch of the confirmed, reproductively mature female T. rex (MOR 1125) would have weighed at least 54–60 kg (119–132 lb) which would possibly correspond to 21-32 eggs. They further stated that larger clutch sizes are also plausible, indicating that tyrannosaurids possibly employed R-selection, a reproductive strategy that maximizes the number of offsprings through large clutch size and minimal parental investment, which would have resulted in rapid maturation of the hatchlings, slower than that of modern birds. It is also likely that the reproduction strategy of tyrannosaurids was an intermediate between R-selection and K-selection, the latter of which would maximize parental investment with fewer number of offsprings and delayed maturation.
Sources: en.wikipedia.org
==== Metabolism ==== Pregabalin undergoes little or no metabolism. In experiments using nuclear medicine techniques, it was revealed that approximately 98% of the radioactivity recovered in the urine was unchanged pregabalin. The main metabolite is N-methylpregabalin. Pregabalin is generally safe in patients with liver cirrhosis.
AM-2201 (1-(5-fluoropentyl)-3-(1-naphthoyl)indole) is a recreational designer drug that acts as a potent but nonselective full agonist for the cannabinoid receptor. It is part of the AM series of cannabinoids discovered by Alexandros Makriyannis at Northeastern University.
2 December – Neville Callaghan, 77, racehorse trainer. 5 December – Rosemary Smith, 86, rally driver. 7 December – Thomas Kilroy, 89, playwright and novelist. 10 December Jonathan Irwin, 82, blood stock agent, auctioneer, stud owner, publisher and founder of the Jack and Jill Foundation. Syd Millar, 89, rugby union player (Ballymena, national team), coach (British & Irish Lions) and International Rugby Board chairman (2003–2007). Born in Northern Ireland. Bill McCarthy, 87, hurler (St Brendan's, Ardfert, Kerry junior team, Munster). 11 December – Frank Twomey, 68, children's television entertainer and comedian (Bosco, Bull Island). 16 December – Joseph Finnegan, 81, judge. 17 December – Maureen Flavin Sweeney, 100, postmistress and formerly a weather forecaster notable for advising on the D-Day landings. 20 December – Johnny Flaherty, 76, hurler (Kinnitty, Offaly senior team, Leinster). 21 December – Martin Feeley, 73, Olympic rower (1976) and surgeon. 27 December – Éamonn Draper, 83, actor and director. 28 December – Patrick Walsh, 92, Roman Catholic prelate, bishop of Down and Connor (1991–2008). 30 December – Paddy Murphy, 89, Gaelic footballer (Dromtarriffe, Duhallow, Cork senior team.
== Other uses == Relief pitcher, a baseball term Registered Paralegal, a certification program of the National Federation of Paralegal Associations Riot Points (used in League of Legends) Regimental Police or Regimental Provost, soldiers responsible for regimental discipline and unit custody in the British Army Role-playing Rating Pending, a rating used by ESRB in promotional games that has lacked a rating.
== External links == Tyrosine MS Spectrum Tyrosine metabolism Archived 2019-07-26 at the Wayback Machine Phenylalanine and tyrosine biosynthesis Phenylalanine, Tyrosine, and tryptophan biosynthesis Archived 2021-05-06 at the Wayback Machine
Sources: en.wikipedia.org
{\displaystyle {\bar {a}}=\alpha a~;~~{\bar {c}}:=\alpha c~;~~{\bar {d}}:=\alpha ^{2}Rd~;~~\alpha :=\left({\frac {4E^{*}}{3\pi \Delta \gamma R^{2}}}\right)^{\frac {1}{3}}~;~~{\bar {A}}:=\pi c^{2}~;~~{\bar {F}}={\frac {F}{\pi \Delta \gamma R}}}
The French explorer and Acadia's first historian Marc Lescarbot described Jerusalem artichokes as being "as big as turnips or truffles," suitable for eating and taste "like chards, but more pleasant." In 1629, the English herbalist and botanist John Parkinson wrote that the widely grown Jerusalem artichoke had become very common and cheap in London, so much so "that even the most vulgar begin to despise them." In contrast, when they had first arrived in England, the tubers had been "dainties for the Queen." Lewis and Clark ate the tubers, prepared by an indigenous woman, in modern-day North Dakota. They have also been called the "Canadian truffle".
== P == Paracelsus (1493–1541), alchemist Rudolph Pariser (1923–2021), theoretical and organic chemist Robert G. Parr (1921–2017), theoretical chemist Louis Pasteur (1822–1895), French biochemist, father of pasteurization Linus Pauling (1901–1994), Nobel Prizes in chemistry and peace Charles J. Pedersen (1904–1989), 1987 Nobel Prize in Chemistry Eugène-Melchior Péligot (1811–1890), French chemist who isolated the uranium metal William Henry Perkin (1838–1907), British organic chemist and inventor of mauveine (dye) William Henry Perkin, Jr. (1860–1929), British organic chemist, son of Sir William Henry Perkin Max Perutz (1914–2002), 1962 Nobel Prize in Chemistry Eva Philbin (1914–2005), Irish chemist David Andrew Phoenix (born 1966), British biochemist Georgy Pigulevsky (1888–1964), Russian chemist and biochemist James Pitts (1921–2014), American chemist known for work on photochemistry and atmospheric chemistry Roy J. Plunkett (1910–1994), discoverer of Teflon John Charles Polanyi (born 1929), Canadian chemist, Nobel Prize in Chemistry 1986 John A.
=== Systematic reviews identifying safety signals === A 2013 comprehensive systematic review by Dr. Salvatore Gentile concluded that second‑generation long‑acting injectable antipsychotics (SGA‑LAIs) "seem to also show unforeseen and worrisome safety signals," and noted that "worsening of psychotic symptoms and depression could also be associated with both risperidone‑LAI and paliperidone palmitate." The leading cause of death among patients enrolled in risperidone‑LAI studies was suicide. A 2017 systematic update by the same author concluded that SGA‑LAIs "do not offer advantages in safety compared with first‑generation antipsychotic LAIs or oral antipsychotics," and highlighted weight gain, hyperprolactinemia, and the finding that the three‑monthly paliperidone palmitate formulation still lacked exhaustive safety data.
Sources: en.wikipedia.org
Filtering removes particulate matter that can block columns or scatter light. A 0.22 micrometre membrane is typical, and the filter material should be checked for peptide adsorption.
Peptides can bind to glass and plastic, so a fraction of the material leaves the solution. The effect is proportionally larger in dilute samples and can bias quantitative results.
Reverse-phase high-performance liquid chromatography is the most widely reported approach. Purity figures should always be quoted together with the wavelength, gradient, and integration parameters used.
It is a modified version of the natural hormone, with three amino acid changes and a fatty acid side chain added. These edits extend its half-life from minutes to about one week. The core receptor activity is retained.