This is a working overview of half-life, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-09-14 and is reviewed periodically as new material appears.
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。
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.
Semaglutide is a synthetic peptide analog of glucagon-like peptide-1 (GLP-1), a hormone released from intestinal L-cells after food intake. The compound belongs to the incretin mimetic class and acts at GLP-1 receptors distributed across pancreatic, gastrointestinal, cardiovascular, and central nervous system tissues. Compared with native GLP-1, the molecule carries structural changes that extend its activity from minutes to roughly one week. It is studied for glycemic control in type 2 diabetes and for weight management, and its effects on cardiovascular and other outcomes remain active research areas.
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.
| Property | Value | Notes |
|---|---|---|
| 保存温度 | 2 至 8 摄氏度 | 避免冻结，部分制剂允许短期室温 |
| 粉末外观 | 白色至类白色固体 | 吸湿后易结块 |
| 纯度检测方法 | 反相高效液相色谱 | 紫外检测，常用 214 纳米 |
| 分子量确认方法 | 液相色谱串联质谱 | 偏差通常以 ppm 表示 |
| 常见降解产物 | 氧化与脱酰胺变体 | 源自甲硫氨酸与天冬酰胺残基 |
Stability studies focus on deamidation of asparagine and glutamine residues, oxidation of methionine, and aggregation into higher-order species. The fatty acid side chain adds susceptibility to oxidative change and can promote self-association at high concentration. Lyophilised material is comparatively robust when kept cold and dry, while aqueous solutions require refrigeration and protection from light. Forced degradation experiments under heat, acid, base, and peroxide conditions establish the specificity of each analytical method. Which degradation route dominates under real storage conditions depends on the formulation and stays formulation-specific.
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.
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.
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.
The Selous Scouts also sought to increase the divisions between the ZANLA and ZIPRA by posing as members of one group and then attacking members of the other group. These tactics became publicly known and embarrassed the government. The Selous Scouts were probably responsible for killing black business owners in rural areas who provided support for the insurgents. These killings were conducted secretly. Special Branch provided the Selous Scouts with poisoned clothing, food, beverages and medicines that the unit inserted into the guerrilla supply chains. The use of contaminated supplies resulted in the reported deaths of over 800 guerrillas, and the likely death toll probably reached well over 1,000. The Rhodesian Directorate of Military Intelligence estimated in 1978 that the Selous Scouts were responsible for 68% of insurgent fatalities within Rhodesia. These casualties largely resulted from attacks by Rhodesian Army units on insurgents located by the Selous Scouts. However, the unit's ruthless tactics were counter-productive as they contributed to further alienating Rhodesia's black population from the government. This formed part of broader flaws in the Rhodesian counter-insurgency strategy, and the historian Jakkie Cilliers has written that "the Selous Scouts were merely the instruments of an overly aggressive and punitive strategy, simply directed at killing as many insurgents as possible and punishing the rural black population to force them to desist from support for the insurgent forces. The apparent success of the Selous Scouts led to the unit being glamorised.
Glutathione S-transferase theta-2 is an enzyme that in humans is encoded by the GSTT2 gene. Glutathione S-transferase (GSTs) theta 2 (GSTT2) is a member of a superfamily of proteins that catalyze the conjugation of reduced glutathione to a variety of electrophilic and hydrophobic compounds. Human GSTs can be divided into five main classes: Alpha, Mu, Pi, Theta, and Zeta. The theta class members GSTT1 and GSTT2 share 55% amino acid sequence identity and both are thought to have an important role in human carcinogenesis. The theta genes have a similar structure, being composed of five exons with identical exon/intron boundaries.
Many pharmaceutical products are sensitive to heat or cold. Controlled distribution systems and sometimes cold chains are required. A mail order or online pharmacy usually ships orders by mail services or by small parcel carrier. The shipment is not temperature-controlled and it may sit in a mail box upon delivery. Conditions can include high or low temperatures outside of the recommended storage conditions for certain products. For example, the USFDA found that the temperature in a steel mailbox painted black could reach 136 °F (58 °C) in full sun while the ambient air temperature was 101 °F (38 °C). Insulated mailing envelopes are sometimes used. Larger shipments are sent in insulated shipping containers with dry ice or gel packs. A digital temperature data logger or a time temperature indicator is often enclosed to monitor the temperature inside the container for its entire shipment.
=== Additional references === Salzer, A. (1999). "Nomenclature of Organometallic Compounds of the Transition Elements". Pure Appl. Chem. 71 (8): 1557–1585. doi:10.1351/pac199971081557. S2CID 14367196. Crabtree, Robert H. (2005). The Organometallic Chemistry of the Transition Metals (4th ed.). Wiley-Interscience.ISBN 0470257628 Miessler, Gary L.; Tarr, Donald A. (2004). Inorganic Chemistry. Upper Saddle River, NJ: Pearson Education. ISBN 978-0-13-035471-6. Cotton, F. A.; Wilkinson, G. (1988). Inorganic Chemistry (5th ed.). Wiley. pp. 626–7. Togni, A.; Halterman, R. L. (1998). Metallocenes. Wiley-VCH.
== History == The therapeutic efficacy of subcutaneous pegcetacoplan in treating paroxysmal nocturnal hemoglobinuria has been established through several clinical trials. Initial phase I and II trials, such as PADDOCK, PALOMINO, and PHAROAH, evaluated pegcetacoplan in participants with paroxysmal nocturnal hemoglobinuria who had not received a complement inhibitor or had previously received eculizumab. These trials demonstrated that 1–2 years of pegcetacoplan treatment effectively controlled hemolysis and improved quality of life in participants with paroxysmal nocturnal hemoglobinuria. Building upon these findings, the efficacy of pegcetacoplan was further assessed in phase III trials. The PRINCE trial, a 26-week study, focused on complement inhibitor-naïve participants with paroxysmal nocturnal hemoglobinuria, while the PEGASUS trial, a 48-week multinational study, included complement inhibitor-treated participants with paroxysmal nocturnal hemoglobinuria. In these trials, subcutaneous pegcetacoplan was administered at a dosage of 1080 mg twice weekly, delivered as a 20-mL subcutaneous infusion. Participants had the option to self-administer the medication or have it administered by qualified research personnel.
Sources: en.wikipedia.org
== Books == Skeletal Muscle Research: Cellular Physiology & Biochemistry (ed. with M. J. Kankaanpää) (1993) Skeletal Muscle Research: Metabolism & Pathophysiology (ed. with L. Packer and O. Hänninen) (1994) Exercise and Oxygen Toxicity (ed. with M. Atalay) (1994) Oxidative Stress In Skeletal Muscles (ed. with Reznick, A et al.) (1998) Antioxidant and Redox Regulation of Genes. 2000. doi:10.1016/B978-0-12-636670-9.X5000-4. ISBN 978-0-12-636670-9. Handbook of Oxidants & Antioxidants in Exercise (ed. with L. Packer and O. Hänninen) (2000) Methods in Enzymology: Redox Cell Biology & Genetics - Parts A and B (ed. with L. Packer) (2002) Methods in Enzymology: Oxygen Sensing (ed. with G. L. Semenza) (2004) Advances in Wound Care - Volume 1 (2010) Advances in Wound Care - Volume 2 (2011) Nutrition and Enhanced Sports Performances (ed. with Bagchi D. and Nair S.) (2013) MicroRNA in Regenerative Medicine. 2015. doi:10.1016/C2012-0-02839-6. ISBN 978-0-12-405544-5.
Another group displayed, with a series of controls, that mixed droplet composition involving potassium iodide was detected accurately on the time scale of seconds with optimal voltage, velocity, and pH ranges. In addition to this, a more unique approach is developing within chronoamperometric readings, where magneto-fluidic systems have been created and the potential readings are measured in otherwise electro-inactive fluids by the dissolution of magnetic microparticles into the reagent. This method is enhanced into a digital microfluidic (DMF) setting, where gold and silver electrodes in junction with dissolved magnetic microparticles in the fluids replaced the typical fluorescence-based detection of droplets in the immunoassay of biomarker analytes. The above experiment by Shamsi et al, alludes to the main use for electrochemical detection in microfluidics; biosensing for various measurements such as enzyme kinetics and biological assays of many other types of cells. Increased control on the system is needed for these processes as with increasing flow rate, enzyme detection decreases. Though as an enzymatic reaction progresses, the amperometric reading will evolve as well, allowing for rapid monitoring of the kinetics. Also, specific surfactants can lack biocompatibility with the system, affecting the enzyme and skewing detection. The reaches of this application have even had effects in aquaculture and economics, as electrochemical sensing has been used to test the freshness of fish rapidly.
In December 2016, it was announced that Monster would replace Sprint Corporation as title sponsor of NASCAR's premier series. NASCAR's chief marketing officer cited Monster's "youthful and edgy" brands a driving force behind the deal. In April 2019, it was reported that NASCAR rejected Monster Energy's offer to extend its sponsorship through 2020 in favor of a new tiered sponsorship model. Monster is endorsed by NASCAR driver Ty Gibbs and sponsors his No. 54 Joe Gibbs Racing car, as well as his Toyota Racing teammate Riley Herbst and his No. 35 23XI Racing car through Terrible Herbst. They are also endorsed by Kurt Busch, who retired due to injuries after the 2022 season. They have also had sponsored Tyler Reddick, Robby Gordon, Ricky Carmichael, and the No. 54 Xfinity Series car of Joe Gibbs Racing/Kyle Busch Motorsports. Monster sponsored Formula 1 team Mercedes-AMG Petronas Motorsport between 2010 and 2023 and was endorsed by the team's drivers, George Russell and seven-time World Champion Lewis Hamilton. Hamilton also has a signature drink with the brand, "LH44". Monster Energy partnered with McLaren from the 2024 season onwards, including introducing a Lando Norris-inspired flavour featuring his helmet design on the can. The company will continue to sponsor Hamilton on a personal level. In September 2026, Monster became a sponsor of LN4 Fusion, a junior-level racing team co-founded by Norris.
=== Films === Kung-Fu Master (1988) – directed by Agnès Varda Trop (peu) d'amour (1998) – directed by Jacques Doillon Mauvaises fréquentations (1999) – directed by Jean-Pierre Améris Mamirolle (2000) – directed by Brigitte Coscas Carrément à l'ouest (2001) – directed by Jacques Doillon Embrassez qui vous voudrez (2002) – directed by Michel Blanc Blanche (2002) – directed by Bernie Bonvoisin Saint Ange (2004) – directed by Pascal Laugier La Vida perra de Juanita Narboni (2005) – of Farida Benlyazid Sisters (2006) – directed by Douglas Buck Go Go Tales (2007) – directed by Abel Ferrara Boxes (2007) – directed by Jane Birkin and starring Birkin, Geraldine Chaplin, Michel Piccoli and Natacha Régnier Bazar (2009) – directed by Patricia Plattner and starring Bernadette Lafont Gigola (2010) – directed by Laure Charpentier Naked in London (2011) – directed by Mark Tierney Polisse (2011) – directed by Maïwenn Un enfant de toi (2012) – directed by Jacques Doillon Quasi a Casa (2024) - directed by Carolina Pavone
Sources: en.wikipedia.org
Richard A. Houghten is a heterocyclic organic chemist and founder of the journal Peptide Research, which was later merged with the International Journal of Peptide and Protein Research, to become the Journal of Peptide Research. His work mainly concerns peptide activity and pharmacology. He is the founder and president of the Torrey Pines Institute for Molecular Studies (TPIMS), a biomedical research institute. Houghten pioneered the "tea-bag" approach of producing peptides for pharmacological work. He is author of over five hundred scientific papers, 38 of which have been cited at least one hundred times. His h-index is over 60.
The publication of medical abbreviations for use in the journals published by the American Medical Association is dictated by the AMA Manual of Style is the style guide of the American Medical Association. Periods are generally not used. Plurals for medical acronyms are represented by affixes a lowercase s with no apostrophe. Arrows may also be used to indicate elevation (↑), diminution (↓), and causation (→, ←).
EAS Sports Nutrition (formerly Experimental & Applied Sciences) was a distributor of creatine nutritional supplements with approximately 300 staff, annual sales exceeding $300 million, and offices/distributors in 54 countries.
=== 18th century === The technical knowledge for making hydraulic cement was formalized by French and British engineers in the 18th century. John Smeaton made an important contribution to the development of cements while planning the construction of the third Eddystone Lighthouse (1755–59) in the English Channel now known as Smeaton's Tower. He needed a hydraulic mortar that would set and develop some strength in the twelve-hour period between successive high tides. He performed experiments with combinations of different limestones and additives including trass and pozzolanas and did exhaustive market research on the available hydraulic limes, visiting their production sites, and noted that the "hydraulicity" of the lime was directly related to the clay content of the limestone used to make it. Smeaton was a civil engineer by profession, and took the idea no further. In the South Atlantic seaboard of the United States, tabby relying on the oyster-shell middens of earlier Native American populations was used in house construction from the 1730s to the 1860s. In Britain particularly, good quality building stone became ever more expensive during a period of rapid growth, and it became a common practice to construct prestige buildings from the new industrial bricks, and to finish them with a stucco to imitate stone. Hydraulic limes were favored for this, but the need for a fast set time encouraged the development of new cements. Most famous was Parker's "Roman cement". This was developed by James Parker in the 1780s, and finally patented in 1796.
Pain: Sacral, coccygeal (tailbone), gluteal, groin, rectum, and perineal regions Sciatica and leg pain Foot and toe pain Persistent genital arousal disorder (PGAD) or pudendal neuralgia Neuropathic pain characterized by burning (dysesthesia), aching, or stabbing sensations Sensory Disturbances: Paresthesias such as tingling, electric shocks, buzzing or internal vibrations Fasciculations (muscle twitching) Numbness or other sensory deficits Motor Dysfunction: Muscle weakness (Paresis) in the legs and feet Toe cramping and muscle spasms Foot Drop (Rarely) Bladder, Bowel, Sexual Dysfunction: Neurogenic bladder: urinary retention, hesitation, Valsalva voiding, increased frequency and urgency, painful bladder, urge incontinence, and stress incontinence. Neurogenic bowel: constipation, diarrhea, cramping, urgency, changes in defecation frequency, false urge to defecate, fecal incontinence, anal sphincter pain or pressure. Erectile dysfunction; retrograde ejaculation Positional Aggravation: Symptoms are typically worsened by standing, walking, sitting, or bending Lying down (recumbency) may provide partial or temporary symptom relief
Sources: en.wikipedia.org
冻融过程中冰晶形成与局部浓度升高会促使肽链发生界面吸附和聚集。聚集不仅降低有效含量，还会改变可见异物与不溶性微粒的计数结果。将溶液分装为单次使用的小体积等份可减少循环次数。
该方法依据疏水性差异分离主峰与相关杂质，对缺失序列、氧化产物和脱酰胺变体具有较好分辨能力。流动相中加入离子对试剂可改善峰形。紫外检测在肽键吸收区工作，灵敏度足以支持常规放行检验。
加速条件可以放大多数化学降解，但聚集与界面诱导的变化对容器、摇动和温度历史更敏感。某些固态转变在短时高温下不一定出现。因此实时稳定性数据仍不可替代，加速结果一般只作为趋势参考。
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and cleared quickly. Semaglutide carries a position 8 substitution that blocks that cleavage and a fatty diacid chain that binds albumin. Together these changes extend its circulating half-life to about one week.