deamidation raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-03-26 and is reviewed periodically as new material appears.
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.
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.
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 |
|---|---|---|
| Appearance | White to off-white lyophilised powder | Visual inspection under suitable light |
| Aqueous solubility | Soluble, pH dependent | Dissolves readily in neutral buffer |
| Storage temperature | 2-8 °C short term; -20 °C or below long term | Protect from light and moisture |
| Primary purity method | Reversed-phase HPLC | UV detection near 214 nm |
| Identity confirmation | LC-MS with peptide mapping | Mass accuracy within a few ppm |
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.
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.
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。
纯度评价多采用反相高效液相色谱，流动相常加入三氟乙酸或甲酸作为离子对改性剂，检测波长设在二百一十四纳米或二百二十纳米。分子量确认依靠电喷雾电离质谱或基质辅助激光解吸电离质谱，实测值应与理论值在数 ppm 内吻合。肽图分析通过酶切后液相色谱串联质谱完成，用于核查序列与修饰位点。体积排阻色谱用于定量共价与非共价聚集体。生物基质浓度测定则采用免疫分析或液相色谱串联质谱。
Storage conditions for semaglutide depend heavily on the presentation. Lyophilized research powder is generally kept at two to eight degrees Celsius in a sealed container, protected from light and moisture. Manufacturer labeling for finished injectable products specifies refrigeration before first use, with defined in-use periods at room temperature afterward. The oral tablet form is stored at controlled room temperature and is more tolerant of short excursions. Temperature excursions should be documented rather than inferred.
Peptide degradation follows several routes. Hydrolysis cleaves the backbone at susceptible residues, oxidation targets methionine and tryptophan side chains, and aggregation produces higher-molecular-weight species that are difficult to reverse. Light exposure accelerates oxidation, which is why amber glass or opaque secondary packaging is common. Repeated freeze-thaw cycles promote aggregation and are best avoided. Stability-indicating methods detect these changes before they become visible.
Whereas testosterone is the major circulating androgen, DHT is the major androgen in the prostate gland. DHT levels in circulation are relatively low and only approximately 10% of those of circulating testosterone levels. Conversely, local concentrations of DHT in the prostate gland are 8- to 10-fold higher than circulating levels of DHT. This is due to high expression of 5α-reductase in the prostate gland, which very efficiently catalyzes the formation of DHT from testosterone such that over 90% of intraprostatic testosterone is converted into DHT. Relative to testosterone, DHT is 2.5- to 10-fold as potent as an AR agonist in bioassays, and hence, is a much stronger androgen in comparison. As such, AR signaling is exceptionally high in the prostate gland, and the effectiveness of bicalutamide monotherapy in the treatment of prostate cancer, which is roughly equivalent to that of gonadotropin-releasing hormone analogues (GnRH analogues), demonstrates a capacity of bicalutamide to strongly antagonize the AR. On the other hand, GnRH analogue monotherapy achieves only a 50 to 60% reduction in levels of DHT in the prostate gland, and combined androgen blockade (CAB), the combination of surgical castration or a GnRH analogue and bicalutamide, is significantly more effective than either modality alone in the treatment of prostate cancer.
For some polyprotic acids, dissociation (or association) occurs at more than one nonequivalent site, and the observed macroscopic equilibrium constant, or macro-constant, is a combination of micro-constants involving distinct species. When one reactant forms two products in parallel, the macro-constant is a sum of two micro-constants,
== Plants and bacteria == Although they lack neurons, systems responding to stimuli (analogous to the sensory system in animals with a nervous system, which includes the proprioception) have also been described in some plants (angiosperms). Terrestrial plants control the orientation of their primary growth through the sensing of several vectorial stimuli such as the light gradient or the gravitational acceleration. This control has been called tropism. A quantitative study of shoot gravitropism demonstrated that, when a plant is tilted, it cannot recover a steady erected posture under the sole driving of the sensing of its angular deflection versus gravity. An additional control through the continuous sensing of its curvature by the organ and the subsequent driving an active straightening process are required. Being a sensing by the plant of the relative configuration of its parts, it has been called proprioception. This dual sensing and control by gravisensing and proprioception has been formalized into a unifying mathematical model simulating the complete driving of the gravitropic movement. This model has been validated on 11 species sampling the phylogeny of land angiosperms, and on organs of very contrasted sizes, ranging from the small germination of wheat (coleoptile) to the trunk of poplar trees. Further studies have shown that the cellular mechanism of proprioception in plants involves myosin and actin, and seems to occur in specialized cells. Proprioception was then found to be involved in other tropisms and to be central also to the control of nutation.
Sources: en.wikipedia.org
== Mechanism == The current believed mechanism for synthetase activity is that first glutathione and Mg2+-ATP bind to the enzyme in a ternary complex where glutathione becomes activated by ATP and forms glutathionyl phosphate. ADP then leaves the active site and the activated phosphate still bound to the enzyme in what is equivalent to a substituted enzyme reacts with glutathionylspermidine to form trypanothione.
In January 2024, a preliminary review conducted by the US Food and Drug Administration (FDA) confirmed no evidence had been found to suggest that the medicine causes suicidal thoughts or actions. In June 2025, the European Medicines Agency recommended that the product information for semaglutide medicines be updated to include non-arteritic anterior ischemic optic neuropathy (NAION) as a very rare side effect, while the World Health Organization concluded that the risk management plan for semaglutide should be revised to include NAION as a potential risk. A 2025 observational study reported a modest increased risk of a serious eye condition in people with diabetes taking glucagon-like peptide-1 (GLP-1) receptor agonists. The analysis found that individuals using the medications had a slightly higher incidence of neovascular age-related macular degeneration compared to similar individuals not on the medications. In the STEP-HFpEF trial including people with obesity and heart failure with preserved ejection fraction, weight loss was associated with improvements in heart failure symptoms and functional capacity. An observational study on people with obesity and type 2 diabetes and heart failure with preserved ejection fraction, semaglutide had about a 42% lower risk of hospitalization for heart failure and all-cause death combined compared with sitagliptin.
===== Extraterrestrial origin of homochirality ===== Some analyses of organic molecules in extraterrestrial materials, such as carbonaceous chondrite meteorites and asteroids, identified small enantiomeric enrichments in a few L-amino acids and D-sugars, leading to the proposition that initial enantiomeric bias could have been seeded on Earth from space. That the enantiomeric biases measured in meteorites and astroids were consistent with that found in biology added credence to this idea, and experimental work showed plausible mechanisms for creating this enantiomeric bias in extraterrestrial materials. It was hypothesized that circularly polarized light originating from Mie scattering on aligned interstellar dust particles may trigger the formation of an enantiomeric excess within chiral material in space. Interstellar and near-stellar magnetic fields can align dust particles in this fashion. Another speculation (the Vester-Ulbricht hypothesis) suggests that fundamental chirality of physical processes such as that of the beta decay (see Parity violation) leads to slightly different half-lives of biologically relevant molecules. The amino acids in asteroids Bennu and Ryugu show no chiral bias. The Murchinson meteorite contained only racemic amino acids.
Sources: en.wikipedia.org
== Management == MASLD warrants treatment regardless of whether the affected person is overweight. MASLD is a preventable cause of death. Guidelines are available from the American Association for the Study of Liver Diseases (AASLD), American Association of Clinical Endocrinologists (AACE) National Institute for Health and Care Excellence (NICE), the European Association for the Study of the Liver (EASL), and the Asia-Pacific Working Party on MASFLD.
=== Brand names === Trazodone has been marketed under a large number of brand names throughout the world. Major brand names include Desyrel (worldwide), Donaren (Brazil), Molipaxin (Ireland, United Kingdom), Oleptro (United States), Trazorel (Canada), and Trittico (worldwide).
Dermatological/integumental: oily skin, acne vulgaris, acne conglobata, seborrhea, stretch marks (due to rapid muscle enlargement), hypertrichosis (excessive body hair growth), androgenic alopecia (pattern hair loss; scalp baldness), fluid retention/edema. Reproductive/endocrine: libido changes, reversible infertility, hypogonadotropic hypogonadism. Male-specific: spontaneous erections, nocturnal emissions, priapism, erectile dysfunction, gynecomastia (mostly only with aromatizable and hence estrogenic AAS), oligospermia/azoospermia, testicular atrophy, intratesticular leiomyosarcoma, prostate hypertrophy, prostate cancer. Female-specific: masculinization, irreversible voice deepening, hirsutism (excessive facial/body hair growth), menstrual disturbances (e.g., anovulation, oligomenorrhea, amenorrhea, dysmenorrhea), clitoral enlargement, breast atrophy, uterine atrophy, teratogenicity (in female fetuses). Child-specific: premature epiphyseal closure and associated short stature, precocious puberty in boys, delayed puberty and contrasexual precocity in girls. Psychiatric/neurological: mood swings, irritability, aggression, violent behavior, impulsivity/recklessness, hypomania/mania, euphoria, depression, anxiety, dysphoria, suicidality, delusions, psychosis, withdrawal, dependence, neurotoxicity, cognitive impairment. Musculoskeletal: muscle hypertrophy, muscle strains, tendon ruptures, rhabdomyolysis.
Sources: en.wikipedia.org
Lower temperatures slow hydrolysis, oxidation and aggregation reactions that degrade the molecule over time. Lyophilised powder is more tolerant than solution, but both benefit from controlled conditions.
Mass spectrometry and peptide mapping are commonly used, often alongside chromatographic retention time comparison. No single technique covers both sequence and higher-order structure.
Aggregation is monitored because it can alter activity and may influence immune responses. Size-exclusion chromatography and related techniques are used to quantify it.
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.