peptidase cleavage 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 2025-12-15 and is reviewed periodically as new material appears.
常规纯度与身份确认依赖反相高效液相色谱，并辅以质谱测定分子量。氨基酸组成分析可用于验证序列构成，肽图分析则能进一步定位修饰或降解产物。杂质谱通常关注缺失序列肽、截短片段和氧化产物。不同方法的检出限并不相同，因此各实验室报告的纯度数值不宜直接横向比较。
多数实验室与市售的 Semax 以冻干粉形式提供。冻干粉通常建议保存在 -20 °C 或更低温度下，同时避免光照与反复升温。短期运输有时采用冷藏条件，但长期保存仍以冷冻为主。分包操作应尽量减少开盖次数，以降低吸湿和微生物污染的风险。开封后若未一次用完，建议在干燥环境中密封并尽快放回低温储存。
Clinical reports describe use in ischaemic stroke, transient ischaemic attack, optic nerve conditions, and cognitive complaints, but most of these studies are small and were conducted in a single region. Systematic reviews have generally described the evidence base as limited in size and variable in methodological quality. Randomised controlled data suitable for international regulatory assessment are scarce. As a result, major treatment guidelines outside Russia do not include the peptide, and interest in it remains largely research-driven rather than routine clinical.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It is described in the literature as an analogue of the ACTH(4–10) fragment, a short N-terminal portion of adrenocorticotropic hormone that retains some neurotropic activity without the full hormonal effects of the parent peptide. The molecule carries a methionine residue at the N-terminus and two proline residues near the C-terminus, features that shape both its interactions with receptor systems and its chemical stability. The free peptide corresponds to the formula C37H51N9O10S and a molecular mass near 813.9 Da.
The compound was developed in the 1980s at the Institute of Molecular Genetics in Moscow, where it emerged from research on short ACTH fragments and their effects on the central nervous system. Russian pharmaceutical listings describe it as a nootropic and neuroprotective agent, most often formulated as nasal drops. It is not a marketed medicine in the United States or the European Union, and no pharmacopoeial monograph covers it. Consequently, most published clinical experience with the substance originates from a small number of research centres, mainly in Russia and neighbouring countries.
| Property | Value | Notes |
|---|---|---|
| 外观 | 白色至类白色粉末 | 常见于冻干制剂 |
| 溶解度 | 易溶于水 | 在极性溶剂中一般也可溶 |
| 建议储存温度 | -20 °C | 冻干粉，避光密封 |
| 常见分析手段 | 反相高效液相色谱 | 常与质谱联用 |
| 主要降解路径 | 水解与氧化 | 溶液状态更显著 |
Lyophilized material is chemically stable for extended periods when kept dry, cold, and protected from light. The powder is hygroscopic, so vials should be warmed to room temperature before opening to reduce condensation on the contents. Once dissolved, the peptide is far less stable because peptide bonds are susceptible to hydrolysis and the methionine residue can oxidize. Solutions are typically aliquoted and held at 2-8 °C for short intervals or frozen for longer ones, and repeated freeze-thaw cycles should be avoided.
Routine characterization relies on reversed-phase high-performance liquid chromatography to establish purity and on mass spectrometry to confirm molecular identity. Electrospray ionization and matrix-assisted laser desorption ionization are both used for mass verification. Amino acid analysis and peptide mapping can detect sequence errors. Common impurities include truncated sequences, methionine sulfoxide formed by oxidation, and deamidated products. Chromatograms are usually recorded near 214 nm, where the peptide backbone absorbs, and purity is reported as the percentage area of the principal peak.
Laboratory descriptions of the material are consistent across suppliers. It appears as a white to off-white lyophilized powder that dissolves readily in water and in polar organic solvents such as dimethyl sulfoxide. Aqueous solutions are clear and colorless at low concentrations. Because the peptide contains methionine, oxidation at the sulfur atom is a recognized degradation pathway, and handling notes usually call for protected, desiccated storage. Reported purity for research-grade lots is generally above 95 percent as measured by reversed-phase high-performance liquid chromatography.
The compound is registered in Russia as a pharmaceutical product, most commonly formulated as a nasal solution, and has been used in that setting since the 1990s. Outside that jurisdiction it is generally handled as a research chemical rather than an approved medicine. Regulatory status therefore differs sharply between countries, and material sold internationally may not correspond to the Russian pharmaceutical formulation. Documentation with commercial samples is typically limited to a certificate of analysis covering purity and identity, not clinical status or local legal classification.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It corresponds to the ACTH(4-7) fragment extended at the C-terminus by a Pro-Gly-Pro tripeptide, an addition intended to slow enzymatic breakdown. The molecular formula is C37H51N9O10S and the molecular mass is approximately 814 daltons. In the literature it is often described as an ACTH(4-10) analog, although that label reflects a naming convention as much as a precise structural relationship. The compound was developed in Russia and remains most closely associated with that research tradition.
Circulation time for the peptide is short because peptidases cleave it readily. The Pro-Gly-Pro tail is thought to slow breakdown compared with the bare ACTH fragment, but the gain appears modest. Absorption after intranasal dosing is limited, and only a fraction of a dose is expected to reach the central nervous system. Laboratory concentrations therefore sit well above levels achieved systemically, a gap that complicates translation from bench findings to clinical claims.
The mechanisms attributed to semax are inferred from animal and cell studies rather than traced to one confirmed target. The most frequently cited pathway involves increased expression of brain-derived neurotrophic factor and nerve growth factor in hippocampal and cortical tissue. Some work points to engagement of melanocortin receptors, particularly MC4, which the parent ACTH fragment can activate. Effects on dopaminergic and serotonergic signalling have also been reported. No single account explains all observed results, and the relative weight of each pathway remains unsettled.
Published studies examine a fairly narrow set of endpoints. Rodent experiments commonly measure maze learning, infarct volume after induced ischemia, and tissue levels of neurotrophic factors. Clinical reports from Russian centres describe attention, memory and recovery scores in patients after stroke or transient ischemic attack. Most of those human studies are small and few have been repeated by independent groups. Outcome measures differ between studies, which limits direct comparison.
==== Alloys ==== Due to the presence of valence 5f electrons, neptunium and its alloys exhibit a very interesting magnetic behavior, like many other actinides. These can range from the itinerant band-like character characteristic of the transition metals to the local moment behavior typical of scandium, yttrium, and the lanthanides. This stems from 5f-orbital hybridization with the orbitals of the metal ligands, and the fact that the 5f orbital is relativistically destabilized and extends outwards. For example, pure neptunium is paramagnetic, NpAl3 is ferromagnetic, NpGe3 has no magnetic ordering, and NpSn3 may be a heavy fermion material. Investigations are underway regarding alloys of neptunium with uranium, americium, plutonium, zirconium, and iron, so as to recycle long-lived waste isotopes such as neptunium-237 into shorter-lived isotopes more useful as nuclear fuel. One neptunium-based superconductor alloy has been discovered with formula NpPd5Al2. This occurrence in neptunium compounds is somewhat surprising because they often exhibit strong magnetism, which usually destroys superconductivity. The alloy has a tetragonal structure with a superconductivity transition temperature of −268.3 °C (4.9 K).
=== Recalls === In 2006, approximately 10 million Sony batteries used in laptops were recalled, including those in laptops from Dell, Sony, Apple, Lenovo, Panasonic, Toshiba, Hitachi, Fujitsu and Sharp. The batteries were found to be susceptible to internal contamination by metal particles during manufacture. Under some circumstances, these particles could pierce the separator, causing a dangerous short circuit.
Over a 10-year period starting in 2008, Burger King predicted 80 percent of its market share would be driven by foreign expansion, particularly in the Asia-Pacific and Indian subcontinent regional markets. While the TPG-led group continued BK's international expansion by announcing plans to open new franchise locations in Eastern Europe, Africa and the Middle East, and Brazil, the company plan is focusing on the three largest markets – India, China, and Japan. The company plans to add over 250 stores in these Asian territories, as well as other places such as Macau, by the end of 2012. Its expansion into the Indian market has the company at a competitive disadvantage with other fast food restaurants such as KFC because of the aversion of the country's large Hindu majority to beef. BK hopes to use their non-beef products, such as their TenderCrisp and TenderGrill chicken sandwiches, as well as other products like mutton sandwiches and veggie sandwiches, to help them overcome this hurdle to expand in that country. 3G has reported that it will continue with the plans to grow globally, even ramping up the planned expansion to help increase their return on investment. It is expected that 3G Brazilian-based management connections in the region may help Burger King expand in Brazil and Latin America, where it has been having problems finding acceptable franchisees. In December 2020, Burger King India went in for an initial public offering (IPO) on the BSE and NSE in India. The IPO was subscribed over 150 times.
== Epidemiology == About 1 in 4,000 children in the United States will develop mitochondrial disease by the age of 10 years. Up to 4,000 children per year in the US are born with a type of mitochondrial disease. Because mitochondrial disorders contain many variations and subsets, some particular mitochondrial disorders are very rare. The average number of births per year among women at risk for transmitting mtDNA disease is estimated to approximately 150 in the United Kingdom and 800 in the United States.
Sources: en.wikipedia.org
As such, it is far more suitable for men for whom long-term medication is being chosen. Mineralcortocoid receptor antagonists (MRA) as a class (including spironolactone, canerenone, eplerenone and finerenone) are cornerstones of heart failure with reduced ejection fraction (HFrEF EF≤40%) management, however, the comparative magnitude of effect on mortality between agents remains uncertain. Primarily, evidence explores spironolactone and eplerenone, with limited comparative data available for canerenone. Furthermore, there is limited evidence for benefit of finerenone in a HFrEF patient cohort, a newer agent recently licensed for the treatment of chronic kidney disease (CKD) in type 2 diabetes mellitus.
=== Groupings and organizations === Lucha Libre AAA Worldwide, a Mexican wrestling promotion Asian Athletics Association, the continental athletics authority in Asia Amateur Athletic Association of England, the Athletic Association in England Arkansas Activities Association, for high school sports Montreal AAA, an amateur athletic association Triple-A (baseball), a North American Minor League Baseball classification level Senior ice hockey § Senior AAA hockey leagues
== Measurement == The most widely used method to determine absolute molar mass is size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering (MALS). SEC can separate macromolecules based on their size by passing an analyte containing molecules of different sizes through a column containing porous substrate. Larger components of the analyte spend less time traveling through these pores and therefore elute faster, while smaller components can access more of these pores and are therefore retained longer. However, molar masses determined through SEC require calibration curves constructed from standards, and calculating absolute molar masses require absolute detection systems. The two primary detection systems used to determine absolute molar mass are light scattering photometers and viscometers. Static light scattering (SLS) experiments measure the difference between the light scattered by a dilute solution and the light scattered through pure solvent. Given a dilute enough solution and at an angle of θ = 0° between the incident light and the scattering direction, this difference, known as the excess Rayleigh ratio ΔR(θ), can be approximately related to the weight-average molar mass Mw through the equation:
Sources: en.wikipedia.org
一般不建议常温长期保存。多数说明指向 -20 °C 冷冻避光。常温运输通常被视为短期可接受，但会加快降解风险。
公开资料对此没有统一答案。普遍建议现配现用，或冷藏并在数日内用完。含甲硫氨酸的序列更易氧化，放置时间越长风险越高。
反相高效液相色谱是最常用的手段，配合质谱确认分子量。氨基酸组成分析和肽图分析可补充序列层面的验证。
It is described as a synthetic analogue of the ACTH(4–10) fragment, a short segment of adrenocorticotropic hormone. Its sequence differs from that fragment and includes two proline residues, which influence stability and behaviour in solution.