This is a working overview of methionine sulfoxide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-17. Anything still debated is marked as such rather than presented as settled.
从分子层面看，Semax 是线性七肽，没有二硫键、糖基或脂链修饰，N 端为游离氨基，C 端为游离羧基。分子含组氨酸与谷氨酸侧链，因此在水和甲醇等极性溶剂中溶解良好，在非极性溶剂中溶解有限。计算分子量约为 814 Da，与其质子化离子的质荷比吻合，可用于质谱确认。
稳定性主要由水解与氧化两条路径支配。肽键在中性或弱酸性条件下相对稳定，遇到强碱或长时间高温则明显断裂；甲硫氨酸侧链容易被氧化成亚砜，使主峰前移并拉低实际含量。金属离子、光照和反复冻融会进一步促进降解或聚集。冻干粉在低温避光条件下可存放较长时间，配制后的水溶液通常需要冷藏并尽快用完。
纯度评估以反相高效液相色谱为主，通过主峰面积百分比给出粗略结果，再配合电喷雾质谱核对分子量。氨基酸分析可验证组成比例，手性色谱或毛细管电泳用于检查残基构型。常见杂质包括缺失序列的短肽、氧化产物与二聚体。由于多数市售品不附带完整检验报告，独立第三方检测常被用来核实标称值。
The peptide is prone to several degradation pathways. Oxidation of the methionine residue produces a sulfoxide that elutes close to the parent peak in many chromatographic systems. Hydrolysis of peptide bonds and deamidation of susceptible residues in related sequences also reduce purity over time. Lyophilised material kept dry at minus twenty degrees Celsius and shielded from light is the most stable form commonly described in laboratory practice.
Material sold for laboratory use varies widely in stated purity and documentation. A certificate of analysis should list the analytical method, the column and detector used, and the observed purity value. Independent verification by an outside laboratory is the practical way to confirm identity when documentation is absent or internally inconsistent. Regulatory status differs by country, and a product legal in one jurisdiction may be unapproved or controlled in another.
Identity and purity of semax are established with reversed-phase high-performance liquid chromatography coupled to ultraviolet detection, usually at 214 nanometres. Mass spectrometry, most often electrospray ionisation in positive mode, confirms the molecular mass and reveals truncated sequences. Amino acid analysis and peptide mapping after enzymatic digestion provide additional structural confirmation. Laboratories typically report purity as the percentage area of the main peak, a figure that does not capture isomeric or oxidised variants unless the method resolves them.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C37H51N9O10S | 游离碱形式 |
| 等电点 | 约 6.5 | 估算值，随缓冲体系变化 |
| 主要降解途径 | 水解与氧化 | 侧链氧化最为常见 |
| 溶液储存 | 2 至 8 摄氏度避光 | 避免反复冻融 |
| 常规分析手段 | 反相色谱与质谱联用 | 氨基酸分析辅助核对 |
Semax is supplied as a lyophilized powder that appears white to off-white. It dissolves readily in water, phosphate-buffered saline, and other aqueous media, which simplifies preparation of working solutions for laboratory use. The nasal products registered in Russia are dilute aqueous solutions, typically around 0.1 percent peptide by weight. Organic solvents are rarely necessary and can complicate handling. Because the peptide is hygroscopic, weighing should be performed quickly and with minimal exposure to ambient humidity.
Solid material is normally kept at minus 20 degrees Celsius in a sealed, desiccated container. Reconstituted solutions are less stable and are usually divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and loss of activity. Light exposure is minimized by using amber glassware or foil wrapping. Published stability data for this peptide are sparse, so recommended storage conditions rest mainly on general practice for short synthetic peptides rather than on dedicated study.
Identity and purity are commonly assessed by reversed-phase high-performance liquid chromatography, with ultraviolet detection near 214 nanometers for the peptide backbone. Mass spectrometry, either electrospray or matrix-assisted laser desorption, confirms molecular mass and detects truncation or modification products. Amino acid analysis can verify composition. Because the sequence contains no strongly absorbing aromatic residue apart from phenylalanine, detection wavelengths are chosen carefully. Purity values above 95 percent are typical for research-grade material.
Solid semax is typically supplied as a lyophilised powder that is hygroscopic and sensitive to moisture, light, and repeated temperature cycling. Long-term storage of the dry peptide is generally recommended at approximately -20 degrees Celsius, while shorter working periods may use refrigeration at 2 to 8 degrees Celsius. Vials should remain tightly closed and desiccated when brought to room temperature, because condensation can damage the material before it is weighed. Dividing a batch into aliquots is preferable to thawing one container repeatedly.
Dissolution is normally performed in water, phosphate-buffered saline, or normal saline, since the peptide is freely soluble in aqueous media and is rarely handled with strong organic solvents. Solution pH should be kept near neutral, because extreme acidity or alkalinity accelerates backbone hydrolysis and encourages oxidation of the methionine side chain. Once dissolved, the material is less stable than the dry powder and is commonly divided into single-use portions and frozen. Buffers containing primary amines, such as Tris, are often avoided because of possible side reactions.
Purity assessment relies mainly on reversed-phase high-performance liquid chromatography, which separates the target heptapeptide from truncated sequences, deletion analogues, and oxidised forms. Mass spectrometry, usually coupled to liquid chromatography, confirms identity through the expected molecular ion and reveals modifications such as methionine sulfoxide formation. Amino acid analysis can verify composition, and tandem mass spectrometry supports sequence confirmation. Ultraviolet detection near 254 to 280 nanometres is convenient because the phenylalanine and histidine residues absorb in that region. Nuclear magnetic resonance is rarely used for routine release testing.
=== Applications for oceanography === Tracers are also used extensively in oceanography to study a wide array of processes. The isotopes used are typically naturally occurring with well-established sources and rates of formation and decay. However, anthropogenic isotopes may also be used with great success. The researchers measure the isotopic ratios at different locations and times to infer information about the physical processes of the ocean.
== Further reading == Bowen, W. Richard; Mohammad, A. Wahab (Aug 1998). "Diafiltration by nanofiltration: Prediction and optimization". AIChE Journal. 44 (8): 1799–1812. Bibcode:1998AIChE..44.1799R. doi:10.1002/aic.690440811. Limayem, Imène; Charcosset, Catherine; Fessi, Hatem (2004). "Purification of nanoparticle suspensions by a concentration/diafiltration process". Separation and Purification Technology. 38 (1): 1–9. doi:10.1016/j.seppur.2003.10.002. Sheth, Jignesh P.; et al. (2003). "Nanofiltration-based diafiltration process for solvent exchange in pharmaceutical manufacturing". Journal of Membrane Science. 211 (2): 251–261. doi:10.1016/s0376-7388(02)00423-4.
After failing to secure a major label contract, Danniels founded the independent Moon Records and negotiated a distribution deal with London Records for a single and one full-length album. For their debut release, the band selected a cover of Buddy Holly's "Not Fade Away" as it had become a crowd favourite, with "You Can't Fight It", an original song, on the B-side. Released in September 1973, the single peaked at No. 88 on the national RPM Top Singles chart. The launch coincided with the band's first major high-profile engagement, opening for the New York Dolls in Toronto.
A remnant of a Green Mountain Boys flag, believed to have belonged to John Stark, is owned by the Bennington Museum. It still exists as one of the few regimental flags from the time of the American Revolution. Although Stark was at the Battle of Bennington and likely flew this flag, the battle has become more commonly associated with the Bennington flag, which is believed to be a 19th-century banner.
Sources: en.wikipedia.org
Michael desired to restore the empire's glory through a rebuilding programme in Constantinople, clever diplomatic alliances, and expansionist wars in Europe. He staved off the threatening Charles I of Anjou first by recognising papal primacy and certain Catholic doctrines at the 1274 Second Council of Lyon, and then by aiding the Sicilian Vespers against Charles in 1282. However, his religious concessions were despised by most of the populace, and were repudiated by his successor Andronikos II (r. 1282–1328). He and his grandson Andronikos III (r. 1328–1341) led several campaigns to restore imperial influence, succeeding in Epirus and Thessaly. Their policies also weakened the state, including the dismissal of the fleet in 1285, the hiring of the mercenary Catalan Company, which turned on the Byzantines in the 1300s, and their civil war between 1320 and 1328. A disastrous civil war between 1341 and 1354 caused long-term economic difficulties, while the Ottoman Turks gradually expanded.
== Other roles == Thy-1 knock out mice also show impaired cutaneous immune responses and abnormal retinal development: thinning of the inner nuclear, inner plexiform, ganglion cell, and outer segment layers of the retina.
=== Worm infections === For river blindness (onchocerciasis) and lymphatic filariasis, ivermectin is typically given as part of mass drug administration campaigns that distribute the drug to all members of a community affected by the disease. Adult worms survive in the skin and eventually recover to produce larval worms again; to keep the worms at bay, ivermectin is given at least once per year for the 10–15-year lifespan of the adult worms. The World Health Organization (WHO) considers ivermectin the drug of choice for strongyloidiasis. Ivermectin is also the primary treatment for Mansonella ozzardi and cutaneous larva migrans. The US Centers for Disease Control and Prevention (CDC) recommends ivermectin, albendazole, or mebendazole as treatments for ascariasis. Ivermectin is sometimes added to albendazole or mebendazole for whipworm treatment, and is considered a second-line treatment for gnathostomiasis. When co-administered, ivermectin and albendazole act in synergy. Ivermectin targets the parasite's nervous and muscular systems, causing paralysis, while albendazole disrupts the parasite's metabolism and energy production. This dual approach immobilizes and kills the parasite and improves the treatment's effectiveness. In January 2025, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive scientific opinion for ivermectin/albendazole for the treatment of infections caused by several types of worm parasites including lymphatic filariasis, a neglected tropical disease.
Sources: en.wikipedia.org
Although the general abstraction can be this simple one must remember that the detalis of this type of processes are highly complex and only recently better understood. Another general pattern observed is that, although remodeling is an inherently microscopical phenomena, there are emergent function and order that arises from the interaction single remodeling agents. The most common way in which this happen is due to single cells trying to reach a local homeostasis, and by doing so actually give rise to a macroscopic function (optimization, healing etc.) and more generally functional structural changes. One very good example of this is the case of fibroblasts in collagen matrix. The remodeling in this case, as explained in the reference, is due to the alignment of the collagen fibers with the principal directions of stress actuated by the fibroblasts. The interesting part is that they do so in such a way as to reach a "stress homeostasis": although the tissue is forced in tension they perceive none, but only after they have remodeled the neighboring as to create an effective stress shield by reinforcing the material where needed. When the tissue is relaxed again, they find themselves in an unnaturally stressed position and change their surroundings trying to reach again a zero stress state (the original one). In reaching such dynamic equilibrium fibroblasts further cooperate by disposing themselves in lines. In this way it's easier to "shield" themselves (as it is more efficient to build houses one right next to the other).
=== Europe === El Niño's effects on Europe are controversial, complex and difficult to analyze, as it is only one of several factors that influence the weather on the continent; these other factors can overwhelm the signal.
In pharmacokinetics, bioavailability generally refers to the fraction of a drug that is absorbed systemically and is thus available to produce a biological effect. This is often measured by quantifying the "AUC". In order to determine the respective AUCs, the serum concentration vs. time plots are typically gathered using C-14 labelled drugs and AMS (accelerated mass spectrometry). Bioavailability can be measured in terms of "absolute bioavailability" or "relative bioavailability". Absolute bioavailability refers to the bioavailability of a drug when administered via an extravascular dosage form (i.e. oral tablet, suppository, subcutaneous, etc.) compared with the bioavailability of the same drug administered intravenously (IV). This is done by comparing the AUC of the non-intravenous dosage form with the AUC for the drug administered intravenously. This fraction is normalized by multiplying by each dosage form's respective dose. F abs = ( AUC non-IV AUC IV ) × ( Dose IV Dose non-IV )
Sources: en.wikipedia.org
电喷雾或基质辅助激光解吸电离质谱是常用手段，测得的质子化离子质荷比可换算为分子量。结果与理论值落在合理误差内，才支持结构一致的判断。
甲硫氨酸侧链含硫醚，在氧气、光照或金属离子存在时容易被氧化。氧化产物极性略增，常在色谱图上表现为主峰之前的肩峰或前伸峰。
通常建议冷藏避光，并在较短时间内使用。不存在适用于所有配方的统一期限，具体取决于浓度、缓冲体系与容器材质。
Reversed-phase high-performance liquid chromatography is the standard method, with detection in the ultraviolet range. Peak area percentage yields a purity figure for the main component. Mass spectrometry is normally run alongside to confirm molecular identity.