Everything below concerns RP-HPLC. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-11. Numbers and descriptions here follow the published literature rather than marketing material.
皮下注射后吸收相对缓慢，绝对生物利用度约为百分之八十九，血药浓度峰值通常出现在给药后一到三天。与白蛋白结合使清除减慢，终末半衰期约为一百六十五小时，接近一周。连续给药约四到五周后达到稳态暴露水平。表观分布容积约为每千克零点二五升，血浆蛋白结合率超过百分之九十九。代谢以蛋白水解切割和脂肪二酸侧链的 β-氧化为主，相关产物主要经尿液与粪便排出。
序列层面的改动同时解决了两个问题，即酶解稳定性与肾脏清除速度。天然 GLP-1 在循环中的半衰期仅约两分钟，主要被二肽基肽酶-4 迅速灭活。酰化侧链与白蛋白的可逆结合形成循环储库，使分子缓慢释放并持续激活受体。这种设计思路后来被广泛用于同类长效肽的开发，属于该类药物化学改造的典型范式。
Semaglutide 是一种经结构修饰的胰高血糖素样肽-1 类似物，其主链与内源性 GLP-1(7-36) 约有百分之九十四的序列一致性。第 8 位丙氨酸被 α-氨基异丁酸取代，使二肽基肽酶-4 无法识别原有切割位点。第 34 位赖氨酸换为精氨酸，进一步降低酶解速率。第 26 位赖氨酸经间隔基连接一条含十八个碳的二酸脂肪链，该侧链赋予分子与血浆白蛋白结合的能力。
Reverse-phase high-performance liquid chromatography is the standard method for purity assessment, separating the peptide from truncated or oxidized variants. Mass spectrometry confirms molecular mass and detects modifications, while ultraviolet absorbance near 280 nanometers supports concentration measurement through tryptophan and tyrosine residues. Circular dichroism can indicate secondary structure, though the peptide is largely helical in solution, and ion-exchange chromatography resolves charge variants. Purity values above 95 percent are typical for research-grade material. Stability studies track degradation over time under defined conditions.
Lyophilized semaglutide is typically stored at temperatures between minus 20 and minus 80 degrees Celsius for long-term preservation. Short-term storage at 2 to 8 degrees Celsius is common for working aliquots. Repeated freeze-thaw cycles can degrade the peptide and are usually avoided. The molecule is hygroscopic in its solid form, so containers should remain sealed with desiccant. Solutions are less stable than powders and are generally prepared fresh. Light exposure is limited because aromatic residues can undergo photo-oxidation.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C187H291N45O59 | 按主链与 C18 二酸侧链计算 |
| 分子量 | 约 4113.6 道尔顿 | 游离碱形式，随反离子略有差异 |
| 外观 | 白色至类白色冻干粉末 | 具吸湿性，需干燥保存 |
| 溶解性 | 微溶于水，易溶于碱性缓冲液 | 溶解性随 pH 升高而改善 |
| 等电点 | 约 5.4 | 影响缓冲液选择与聚集倾向 |
Stability studies examine how temperature, pH, and moisture influence degradation rates over time. In aqueous solution, hydrolysis and deamidation accelerate as pH moves away from mildly acidic conditions. Light exposure and residual metal ions can also trigger oxidation of susceptible residues. Accelerated aging at elevated temperature is used to estimate shelf life, though extrapolation to room temperature carries uncertainty because individual degradation pathways do not always scale predictably.
Lyophilized semaglutide powder is typically held at minus twenty degrees Celsius for long-term storage. At that temperature, solid-state degradation reactions proceed slowly and the peptide remains intact for extended periods. Repeated freeze-thaw cycles are best avoided because they promote aggregation and can shift the proportion of monomeric peptide present. Working aliquots are often prepared so that each portion is thawed only once, and desiccant is placed inside the vial to limit moisture uptake.
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.
Two principal therapeutic variants exist under separate regulatory filings, one indicated for glycemic control in type 2 diabetes and one for chronic weight management. Both use the same active molecule; differences lie in formulation strength, titration schedule, and labeling. Regulatory agencies in the United States and European Union approved injectable forms in 2017 and 2018 respectively. An oral tablet formulation received approval later, using a carrier molecule to enhance absorption across the gastric epithelium. Labeling differs by jurisdiction and by indication.
The distinction between established facts and open questions matters here. That the peptide binds the GLP-1 receptor and stimulates insulin release in a glucose-dependent manner is well documented. How individual variability in receptor density, gastric emptying rate, and gut microbiome composition shapes response remains an active research area. Long-term outcomes beyond five years of continuous use are not yet fully characterized in published trials, and several extension studies are ongoing.
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 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.
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.
== Isotope vs. nuclide == A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. Thus the terms are roughly the same, but the nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number greatly affects nuclear properties, but its effect on chemical properties is negligible for most elements. Even for the lightest elements, whose ratio of neutron number to atomic number varies the most between isotopes, it usually has only a small effect although it matters in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to affect biology strongly). The term isotopes (originally also isotopic elements, now sometimes isotopic nuclides) is intended to imply comparison (like synonyms or isomers). For example, the nuclides 126C, 136C, 146C are isotopes (nuclides with the same atomic number but different mass numbers), but 4018Ar, 4019K, 4020Ca are isobars (nuclides with the same mass number). As the older and better-known term, isotope is however still used in some contexts where nuclide might be more appropriate, such as in nuclear technology and nuclear medicine.
== Business == Keep-it Technologies has developed a time and temperature indicator (TTI) that shows the actual remaining shelf life of products, which is significantly better than the traditional static date stamp. It is based on temperature over time, and each indicator is tailored to the products shelf life profile. The technology behind the indicator has been developed and verified at the University, before a working prototype was finally developed. Keep-it Technologies has patented the indicator in a number of countries, including the USA. Keep-it Technologies’ shelf-life indicator comprises two small chambers with different ingredients that react and change colour depending on time and temperature. A blue bar moves gradually from left to right and eventually disappears. The blue bar moves slow at low temperatures and faster as the temperature increases. The indicator is attached as a self-adhesive label to the packaging by the food producer. It monitors the time and temperature the packages is exposed to from production, during transport, at the retailer, and in the consumer's own fridge. In this way the device gives more correct indication of remaining shelf life (days left) than traditional date-stamping, because it takes into account the actual temperature to which the individual food package has been exposed. Benefits by using the indicator: Reduce food waste for both retailer & consumer, increase food safety & quality, and gain control over the whole cold chain, and reduce customer complaints.
== Interpretation == One interpretation of the art is that humans have the power to destroy nature anywhere; not only in art galleries, but putting this choice in an art gallery makes that power more visible.
Harmine is a naturally occurring harmala alkaloid with monoamine oxidase-inhibiting under preliminary research for potential anti-HIV properties. It is found in various plants such as Peganum harmala and B. caapi, historically studied for Parkinson's disease and currently in early-phase clinical trials. Harmine is the primary β-carboline alkaloid in ayahuasca and has been studied for potential therapeutic effects including modulation of astrocytic function, anti-inflammatory properties, influence on neural progenitor proliferation, and possible roles in addiction and depression treatment through mechanisms involving glutamate regulation and BDNF signaling.
=== Effects in females === LH supports theca cells in the ovaries that provide androgens and hormonal precursors for estradiol production. At the time of menstruation, FSH initiates follicular growth, specifically affecting granulosa cells. With the rise in estrogens, LH receptors are also expressed on the maturing follicle, which causes it to produce more estradiol. Eventually, when the follicle has fully matured, a spike in 17α-hydroxyprogesterone production by the follicle inhibits the production of estrogens. Previously, the preovulatory LH surge was attributed to a decrease in estrogen-mediated negative feedback of GnRH in the hypothalamus, subsequently stimulating the release of LH from the anterior pituitary. Some studies, however, attribute the LH surge to positive feedback from estradiol after production by the dominant follicle exceeds a certain threshold. Exceptionally high levels of estradiol induce hypothalamic production of progesterone, which stimulates elevated GnRH secretion, triggering a surge in LH. The increase in LH production only lasts for 24 to 48 hours. This "LH surge" triggers ovulation, thereby not only releasing the egg from the follicle, but also initiating the conversion of the residual follicle into a corpus luteum that, in turn, produces progesterone to prepare the endometrium for a possible implantation. LH is necessary to maintain luteal function for the second two weeks of the menstrual cycle.
Sources: en.wikipedia.org
=== Pain management === The circumcision procedure causes pain, and for neonates this pain may interfere with mother-infant interaction or cause other behavioral changes, so the use of analgesia is advocated and required by law in some countries. Ordinary procedural pain may be managed in pharmacological and non-pharmacological ways. Pharmacological methods, such as localized or regional pain-blocking injections and topical analgesic creams, are safe and effective. The ring block and dorsal penile nerve block (DPNB) are the most effective at reducing pain, and the ring block may be more effective than the DPNB. They are more effective than EMLA (eutectic mixture of local anesthetics) cream, which is more effective than a placebo. Topical creams have been found to irritate the skin of low birth weight infants, so penile nerve block techniques are recommended in this group. Circumcision is contraindicated for premature babies partially because of complications with anesthesia.
Top-icing is the practice of placing a 2-inch (51 mm) to 4-inch (100 mm) layer of crushed ice on top of agricultural products that have high respiration rates, need high relative humidity, and benefit from having the cooling agent sit directly atop the load (or within individual boxes). Cars with pre-cooled fresh produce were top-iced just before shipment. Top-icing added considerable dead weight to the load. Top-icing a 40-foot (12 m) reefer required in excess of 10,000 pounds (4,500 kg) of ice. It had been postulated that as the ice melted, the resulting chilled water would trickle down through the load, continuing the cooling process. It was found, however, that top-icing benefited only the uppermost layers of the cargo, and that the water from melting ice often passed through spaces between the cartons and pallets, with little or no cooling effect. It was ultimately determined that top-icing is useful only in preventing an increase in temperature and was eventually discontinued.
=== Caffé Bene === Caffe Bene is a coffeehouse chain based in Seoul. It was founded in May 2008 by Sun-Kwon Kim, its chief executive officer. Caffè Bene is the largest coffeehouse in South Korea measured by number of stores. As of April 24, 2012, it had 760 outlets. Initially Caffe Bene struggled to gain any traction in an oversaturated American market. Failing to gain brand recognition, Sun-Kwon Kim agreed a deal with a number of entertainment shows to use his coffee locations in a selection of TV shows for a 3% share in the companies profit.
a bolus dose that is pumped to cover food eaten or to correct a high blood glucose level. a basal dose that is pumped continuously at an adjustable basal rate to deliver insulin needed between meals and at night.
=== Levels === Total levels of testosterone in the body have been reported as 264 to 916 ng/dL (nanograms per deciliter) in non-obese European and American men age 19 to 39 years, while mean testosterone levels in adult men have been reported as 630 ng/dL. Although commonly used as a reference range, some physicians have disputed the use of this range to determine hypogonadism. Several professional medical groups have recommended that 350 ng/dL generally be considered the minimum normal level, which is consistent with previous findings. Levels of testosterone in men decline with age. In women, mean levels of total testosterone have been reported to be 32.6 ng/dL. In women with hyperandrogenism, mean levels of total testosterone have been reported to be 62.1 ng/dL.
Sources: en.wikipedia.org
差别集中在三处：第 8 位残基被非天然氨基酸取代，第 34 位换成精氨酸，第 26 位增加一条脂肪酸侧链。前两处改动降低酶解速率，侧链则通过白蛋白结合延长循环时间。综合结果是半衰期从约两分钟延长到约一周。
胰岛素释放需要细胞内环腺苷酸与钙信号升高，同时依赖葡萄糖代谢产生的协同信号。血糖水平较低时协同信号不足，分泌增强有限。这一机制在降糖效果与低血糖风险之间提供了缓冲。
白蛋白结合是主要原因，它减少肾小球滤过并保护分子免受蛋白酶降解。序列修饰带来的酶解抵抗同样不可忽略，二者共同作用。脂肪链的疏水性还会影响组织分布，但其对总半衰期的贡献程度仍在研究之中。
Long-term storage is usually at minus 20 to minus 80 degrees Celsius in a sealed, desiccated container. Working aliquots can be held briefly at 2 to 8 degrees Celsius.