If you have been reading about single-use aliquot and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-09-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
Stability depends heavily on physical state. Lyophilized powder held dry, cold and dark retains its content over long periods, whereas dissolved peptide begins to change within days at room temperature. The most cited degradation route is oxidation of the methionine residue, which converts the peptide to a sulfoxide form that elutes differently on chromatography. Hydrolysis of amide bonds and adsorption onto container walls contribute smaller losses. Buffers that exclude oxygen from the headspace slow the oxidation pathway, but no single condition prevents all change indefinitely.
Practical handling follows from those properties. Bulk material is best divided into single-use portions soon after receipt, because each thaw exposes the whole container to moisture and temperature cycling. Vials should be allowed to reach room temperature before opening to prevent condensation on the powder. Low-binding plasticware reduces loss of dilute solutions, and sterile filtration is used when a preparation must remain free of microbial growth. Records of batch number, reconstitution date and storage history are what allow a later analytical result to be interpreted meaningfully.
Semax 是一种人工合成的七肽，氨基酸序列为 Met-Glu-His-Phe-Pro-Gly-Pro，单字母缩写记作 MEHFPGP。它被归类为促肾上腺皮质激素片段 ACTH(4-10) 的结构类似物，但并不天然存在于生物体内。母体片段 ACTH(4-10) 的序列为 Met-Glu-His-Phe-Arg-Trp-Gly，Semax 替换了中间两个残基，并在羧基端延长了 Pro-Gly-Pro 三肽。这种延长被普遍认为能提升分子对肽酶的耐受性。
该化合物于二十世纪八十年代在俄罗斯被开发，相关工作由俄罗斯科学院分子遗传学研究所的研究团队主导。开发目标并非复制 ACTH 的完整激素活性，而是寻找保留其神经作用方向、同时去除促肾上腺皮质激素释放效应的短肽片段。研究记录显示，这一方向促成了多个相关短肽的合成与筛选，而 Semax 是其中被研究最广泛的一个。当地文献常以 Семакс 这一名称指代它。
研究兴趣主要集中在神经营养因子相关的路径上，包括脑源性神经营养因子与神经生长因子的表达变化。部分实验报告称在特定条件下观察到这些因子的水平上升，但具体信号通路和剂量依赖关系仍未完全厘清。多数公开数据来自细胞模型和动物实验，人体对照研究数量有限。因此，该化合物的作用机制在文献中属于活跃讨论，而非已经确立的定论。
| Property | Value | Notes |
|---|---|---|
| Typical purity specification | ≥ 95 % of peak area by HPLC | Some suppliers quote 98 % or higher |
| Identity confirmation | Mass spectrometry (electrospray or MALDI) | Observed mass is compared with the calculated mass |
| Common analytical method | Reversed-phase HPLC on a C18 column | Acetonitrile and water gradients with trifluoroacetic acid |
| Primary degradation route | Oxidation of the methionine residue | Yields a sulfoxide that separates cleanly on chromatography |
| Storage of dissolved material | Aliquoted and frozen at −20 °C or below | Single-use aliquots avoid repeated temperature cycling |
Once dissolved, the peptide is considerably less stable than the solid. Aqueous solutions are usually prepared at neutral to slightly acidic pH, filtered, and divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are a common cause of avoidable loss and are best prevented by never refreezing a thawed aliquot. Adsorption to plastic and glass surfaces can lower the measured concentration of dilute solutions, particularly below roughly 0.1 mg/mL. Buffer choice, salt content, and container material all influence how much peptide remains detectable after storage.
Identity and purity are established with standard peptide methods. Reversed-phase HPLC with ultraviolet detection near 214 nm resolves the parent peak from deletion and truncation byproducts, and reports typically quote a main-peak percentage. Mass spectrometry by electrospray or MALDI-TOF confirms the expected molecular mass, while amino acid analysis or peptide mapping can verify composition when the sequence itself is in question. A certificate of analysis that pairs a chromatogram with a mass spectrum is more informative than a purity figure alone. Counter-ion content and residual solvents are separate specifications and are frequently omitted.
Semax is normally supplied as a lyophilized powder, and that form is the most stable. Suppliers commonly recommend storage at -20 °C in a desiccated container protected from light, with short-term handling at room temperature limited to weighing and transfer. Powder that has absorbed moisture degrades faster, so vials should be warmed to ambient temperature before opening to prevent condensation on the contents. Hygroscopic behavior is typical of short hydrophilic peptides, and humidity control matters more than temperature alone for long-term retention.
Semax 是人工设计的七肽，序列为 Met-Glu-His-Phe-Pro-Gly-Pro，骨架取自促肾上腺皮质激素片段 ACTH(4-10)。它于二十世纪八十年代在苏联的分子遗传学研究机构内合成。设计目标是保留该片段与注意力和记忆相关的活性，同时剔除促皮质激素释放等内分泌作用。此后俄罗斯将其登记为药品并进入临床使用。
当时的短肽研究普遍关注能否穿越血脑屏障、在低剂量下产生中枢效应，Semax 属于这一路线。鼻内给药是其主要使用方式，俄语文献报道的适应症涵盖缺血性卒中、短暂性脑缺血发作、认知功能减退以及视神经病变。这些研究大多发表在当地期刊上，样本规模与终点设置同西方试验惯例存在差异，国际同行对其临床证据的强度看法不一。
各国监管态度分化明显。俄罗斯按处方药管理，部分东欧国家留有使用记录；欧盟与美国未批准其作为药物上市，市面流通品通常标注为研究用化学品。身份差异意味着标示含量、纯度与无菌性缺少统一核查。体育领域还牵涉反兴奋剂名录，跨境携带则受目的地药品法规约束。
According to the Salvadoran government, the country's homicide rate was 38 per 100,000 people in 2019; 19.7 per 100,000 in 2020; 17.6 per 100,000 in 2021; 7.8 per 100,000 in 2022; 2.4 per 100,000 in 2023; and 1.9 per 100,000 in 2024. Bukele has attributed the decline to his security policies. According to Celia Medrano, a human-rights lawyer and former general coordinator of the Commission for the Defense of Human Rights of Central America, it is "impossible" ("imposible") to verify the Salvadoran government's homicide figures because there is "no public access" ("no hay acceso público") to a daily homicide registry. Medrano stated that deaths in custody are not registered as homicides. Bodies found in mass graves, missing persons, and people killed in police encounters are not included in the government's homicide statistics. In July 2024, then former United States president Donald Trump falsely accused Bukele's government of "exporting" criminals to the United States to lower El Salvador's crime rate.
=== Gina Cross === Dr. Gina Cross (voiced by Kathy Levin) is a Black Mesa scientist who first appears as the Holographic Assistant for Gordon Freeman in the Black Mesa's Hazard Course and then later as one half of the protagonists in Half-Life: Decay. In Decay, Cross is the one who delivers the GG-3883 crystal sample to the delivery system and then heads to an area below the test chamber, where Dr. Colette Green is stationed, to fix a jam in the lift that allows the specimen to be delivered up to Gordon. After the Resonance Cascade occurs, Cross teams up with Dr. Green to battle their way through the now alien-infested facility. They first escort Rosenberg to the surface to contact the military, and then under the guidance of Dr. Richard Keller, they succeed in starting a resonance reversal to help lessen the effects of the dimensional rift. In Half-Life: Blue Shift, Cross can briefly be seen on a security camera in the surveillance room, delivering the GG-3883 crystal. In Half-Life: Opposing Force, Adrian Shephard finds Cross's corpse in Xen after being teleported there by the Displacer Cannon, which implies that she died sometime after the events of Decay. Randy Pitchford, the president and CEO of Gearbox Software, had since confirmed this fate. However, Valve themselves never confirmed anything about Cross's fate after the events of Decay. Cross was originally planned to be Gordon Freeman's spouse as well as another playable character in the original Half-Life, but this idea was cut from the final game.
Because the formation of PTH regulates the calcium level in the blood, it can affect all areas of the body. The overactivity of a parathyroid gland is known as hyperparathyroidism. It is unknown what directly causes hyperparathyroidism. However there are many factors that can cause over-secretion of PTH. The further consequence of this disorder can be osteopenia, or even osteoporosis, which is the loss of bone density. This leaves bones more porous, fragile, and likely to experience fracture. This can be detected by usage of dual-energy X-ray absorptiometry (DEXA). Interesting enough, a derivative of synthetic PTH is often given to patients with osteoporosis to combat the disease.
Sources: en.wikipedia.org
== Function == CART is a neuropeptide that produces similar behavior in animals as cocaine and amphetamine, but conversely blocks the effects of cocaine when they are co-administered. The peptide is found in several areas, among them the ventral tegmental area (VTA) of the brain. When CART was injected into rat VTA, increased locomotor activity was seen, which is one of the signs of "central stimulation" caused by psychostimulants, such as cocaine and amphetamine. The same rats also tended to return to the place where they were injected. This is called conditioned place preference and is also seen after injection of cocaine. CART peptides, in particular, CART(55–102), seem to have an important function in the regulation of energy homeostasis and interact with several hypothalamic appetite circuits. CART expression is regulated by several peripheral peptide hormones involved in appetite regulation, including leptin, cholecystokinin and ghrelin, with CART and cholecystokinin having synergistic effects on appetite regulation. CART is released in response to repeated dopamine release in the nucleus accumbens, and may regulate the activity of neurons in this area. CART production is upregulated by CREB, a protein thought to be involved with the development of drug addiction, and CART may be an important therapeutic target in the treatment of stimulant abuse.
Seasonings such as fresh ginger root, garlic, scallion, cilantro and sesame are widely used in many regional cuisines. Sichuan peppercorns, star anise, cinnamon, fennel, cloves and white peppers and smart weed are also used in different regions. To add extra flavor to the dishes, many Chinese cuisines also contain dried Chinese mushrooms, dried baby shrimp, dried tangerine peel, and dried Sichuan chillies. When it comes to sauces, China is home to soy sauce, which is made from fermented soybeans and wheat. A number of sauces are also based on fermented soybeans, including hoisin sauce, ground bean sauce and yellow bean sauce. There are also different sauces preferred by regional cuisines, oyster sauce, fish sauce and furu (fermented tofu) are also widely used. Vinegar also has a variety with different flavors: clear rice vinegar, Chinkiang black rice vinegar, Shanxi vinegar, Henghe vinegar etc.
The Kingdom of Hanover (German: Königreich Hannover) was established in October 1814 by the Congress of Vienna, with the restoration of George III to his Hanoverian territories after the Napoleonic era. Its capital was Hanover and it also ruled Gottingen and Osnabruck. It had access to the North Sea, and bordered on the Netherlands and the free German cities of Hamburg and Bremen. It succeeded the former Electorate of Hanover, and joined 38 other sovereign states in the German Confederation in June 1815. The kingdom was ruled by the House of Hanover, a cadet branch of the House of Welf, in personal union with Great Britain between 1714 and 1837. Since its monarch resided in London, a viceroy, usually a younger member of the British royal family, handled the administration of the Kingdom of Hanover. The personal union with the United Kingdom ended in 1837 upon the accession of Queen Victoria because semi-Salic law prevented females from inheriting the Hanoverian throne while a dynastic male was still alive. Her uncle Ernest Augustus thus became the ruler of Hanover. His only son succeeded him to the throne as George V. As he backed the losing side in the Austro-Prussian War, his kingdom was conquered by Prussia in 1866 and ceased to exist as an independent kingdom, becoming the Prussian Province of Hanover. In January 1871, along with the rest of Prussia, Hanover became part of the German Empire upon the unification of Germany.
SOCl2 + H2O → 2 HCl + SO2 By a similar process it also reacts with alcohols to form alkyl chlorides. If the alcohol is chiral the reaction generally proceeds via an SNi mechanism with retention of stereochemistry; however, depending on the exact conditions employed, stereo-inversion can also be achieved. Historically the use of SOCl2 with pyridine was called the Darzens halogenation, but this name is rarely used by modern chemists.
Sources: en.wikipedia.org
Plate tectonics over the period dating back at least 1 billion years led to geological creation of the land that is now the Appalachian Mountain range. The continental movement led to collisions that built mountains and they later pulled apart creating oceans over parts of the continent that are now exposed.
== Social == Social Progress Index 2017: Thailand ranked 62 of 128 nations (1=best; 128=worst). Other ASEAN nations ranked were: Malaysia, 50; Philippines, 68; Indonesia, 79; Myanmar, 96; Cambodia, 98; and Laos, 99. Social Progress Index 2015: Social progress is the capacity of a society to meet the basic human needs of its citizens. Thailand ranked 57 of 113 nations (1=best; 133=worst). Other ASEAN states were ranked: Philippines, 64; Indonesia, 86; Cambodia, 99; Laos, 102; and Myanmar, 119. Social Progress Index 2014: Thailand ranked 59 of 132 countries State of the World's Mothers 2014: Ranked 72 of 178 countries.
=== International === There are regular regional and international educational medical physics activities. The oldest of these is the International College on Medical Physics at the International Centre for Theoretical Physics (ICTP), Trieste, Italy. This College has educated more than 1000 medical physicists from developing countries.
Sources: en.wikipedia.org
Suppliers normally quote a percentage of total chromatographic peak area, most often from reversed-phase HPLC. That figure says nothing about what the remaining percentage contains, and it depends on the detection wavelength used. A mass spectrometry result is a separate and stronger check on identity.
The methionine residue at the start of the chain is vulnerable to oxidation, producing a sulfoxide variant. Amide bonds can also hydrolyze, though more slowly under neutral conditions. Cold storage, oxygen exclusion and minimization of freeze-thaw cycles slow both processes but do not stop them.
A purity number on a certificate does not establish that a powder is the same product as a registered nasal medicine. Counter-ion content, residual solvents and peptide-related impurities may differ between the two. Independent verification is the only way to narrow that gap.
不是。Semax 是完全人工合成的七肽，自然界中没有对应的已知肽段。它的设计灵感来自促肾上腺皮质激素片段 ACTH(4-10)，但序列经过了替换和延长。