reversed-phase HPLC comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-03-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
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。
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.
Quality documentation for research-grade peptide usually includes a certificate of analysis stating purity, identity, and residual counterion content. Batch-to-batch variation in purity and salt form is a recognized issue, and comparisons across suppliers require attention to the exact counterion, for example acetate versus trifluoroacetate. Sequence verification by tandem mass spectrometry provides stronger evidence than a single mass measurement. For any study reporting biological results, the analytical method and the measured purity should be stated explicitly. Independent verification of supplier claims is considered good practice.
| Property | Value | Notes |
|---|---|---|
| 化学类别 | 合成七肽 | ACTH(4-10) 结构类似物 |
| 氨基酸序列 | Met-Glu-His-Phe-Pro-Gly-Pro | 单字母写作 MEHFPGP |
| 分子量 | 约 813.9 Da | 随确切形式和盐型略有变化 |
| 常见同义词 | ACTH(4-10) 类似物 | 俄语文献称 Семакс |
| 开发来源 | 俄罗斯 | 二十世纪八十年代 |
Development took place during the 1980s at institutes of the Russian Academy of Sciences, where peptide fragments of ACTH were screened for cognitive and neuroprotective effects. The compound received regulatory approval in Russia as a nasal preparation, marketed for conditions such as ischemic stroke, transient ischemic attacks, and optic nerve disorders. Registration in other countries has not followed. Most published clinical reports originate from a small number of Russian research groups, and independent replication outside that setting remains limited. The regulatory status therefore differs sharply between Russia and the rest of the world.
Laboratory work points toward modulation of neurotrophic signaling, particularly expression of brain-derived neurotrophic factor and nerve growth factor in hippocampal tissue. Studies also describe effects on monoamine turnover, inflammatory mediators, and oxidative markers. These observations come mainly from animal models and cultured cells, so the causal chain in humans is not firmly established. Whether the reported molecular changes translate into measurable clinical benefit is an open question. Reviews generally present the mechanism as plausible rather than demonstrated.
Clinical evidence consists largely of small trials with modest sample sizes, often without independent replication. Reported endpoints include cognitive scores, recovery after stroke, and visual function, but study designs vary widely and few trials meet contemporary reporting standards. Systematic reviewers have noted a high risk of bias in several of these reports. No large multicenter trial conducted outside Russia has been published. The compound is therefore best described as investigational in most jurisdictions, with its clinical role still unresolved.
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.
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.
Regulatory status varies sharply by country. Semax is registered for medical use in Russia, where it appears in formularies as a nasal solution, and it also holds registration in a small number of neighbouring states. It has no approval from the United States Food and Drug Administration or the European Medicines Agency, and it is not a scheduled controlled substance in most jurisdictions. Elsewhere it circulates mainly as laboratory material, so purity documentation comes from suppliers rather than from a national pharmacopoeia.
Semax is a synthetic peptide created in the Soviet Union during the early 1980s by researchers working in Moscow. It was built from the short adrenocorticotropic hormone fragment known as ACTH(4-10), and the chain was then extended with three additional amino acids. The resulting molecule was named semax and entered clinical use in Russia in 1994. It is generally described as a nootropic and neuroprotective agent rather than as a hormone analogue.
The parent fragment ACTH(4-10) carries the sequence Met-Glu-His-Phe-Arg-Trp-Gly. Semax replaces the arginine and tryptophan positions with a proline-glycine-proline tail, giving Met-Glu-His-Phe-Pro-Gly-Pro. That change removes residues associated with adrenal stimulation, so the peptide does not drive cortisol release the way full ACTH does. This distinction shapes how the compound is grouped in the literature, where it sits with neuropeptides and peptide neuromodulators rather than with corticosteroids.
Contrary to popular belief, nicotine itself does not cause cancer in humans, although it is unclear whether it functions as a tumor promoter as of 2012. A 2018 report by the US National Academies of Sciences, Engineering, and Medicine concludes, "[w]hile it is biologically plausible that nicotine can act as a tumor promoter, the existing body of evidence indicates this is unlikely to translate into increased risk of human cancer." Although nicotine is classified as a non-carcinogenic substance, it can still theoretically promote tumor growth and metastasis as evidenced from alterations. Nicotine induces several processes, some of them via nicotine's effects on immune function, that contribute to cancer progression in both smoking-related and non-smoking-related cancers, including cell cycle progression, epithelial-to-mesenchymal transition, migration, invasion, angiogenesis, and evasion of apoptosis. These effects are primarily mediated through nicotinic acetylcholine receptors (nAChRs), particularly the α7 subtype, and to a lesser extent, β-adrenergic receptors (β-ARs). Activation of these receptors triggers several signaling cascades crucial in cancer biology, notably the MAPK/ERK pathway, PI3K/AKT pathway, and JAK-STAT signaling. Nicotine potentially promotes lung cancer development by enhancing proliferation, angiogenesis, migration, invasion, and epithelial–mesenchymal transition (EMT) via nAChRs, which are present in lung cancer cells. Additionally, nicotine-induced EMT contributes to drug resistance in cancer cells.
Dermatobia hominis (human botfly) Cordylobia anthropophaga (tumbu fly) Cordylobia rodhaini (Lund's fly) Oestrus ovis (sheep botfly) Hypoderma spp. (cattle botflies or ox warbles) Gasterophilus spp. (horse botfly) Cochliomyia hominivorax (new world screwworm fly) Chrysomya bezziana (old world screwworm fly) Auchmeromyia senegalensis (Congo floor maggot) Cuterebra spp. (rodent and rabbit botfly)
==== Extrusion-based printing ==== Although there are different approaches to extrusion based printing, these approaches follow the same basic procedures. The platform on which food is printed consists of a standard 3-axis stage with a computer controlled extrusion head. This extrusion head pushes food materials through a nozzle typically by way of compressed air or squeezing. The nozzles can vary with respect to what type of food is being extruded or the desired printing speed (typically the smaller the nozzle the longer the food printing will take). As the food is printed, the extrusion head moves along the 3-axis stage printing the desired food. Some printed food requires additional processing such as baking or frying before consumption. Extrusion based food printers can be purchased for household use, are typically compact in size, and have a low maintenance cost. Comparatively, extrusion based printing provides the user with more material choices. However, these food materials are usually soft, and as a result, makes printing complex food structures difficult. In addition, long fabrication times and deformations due to temperature fluctuations with additional baking or frying require further research and development to overcome.
Sources: en.wikipedia.org
=== Banana equivalent dose === The origin of the concept of using a banana equivalent dose (BED) as a benchmark is unknown. In 1995, Gary Mansfield of the Lawrence Livermore National Laboratory found the Banana Equivalent Dose (BED) to be very useful in explaining radiation risks to the public. It is not a formally used dose. The banana equivalent dose is the dose of ionizing radiation to which a person is exposed by eating one banana. Bananas contain potassium. Natural potassium consists of 0.0117% of the radioactive isotope 40K (potassium-40) and has a specific activity of 30,346 becquerels per kilogram, or about 30 becquerels per gram. The radiation dose from eating a banana is about 0.1 μSv. The value of this reference dose is given as "1" and thus becomes the "unit of measurement" banana equivalent dose. Consequently, other radiation exposures can be compared to the consumption of one banana. For example, the average daily total radiation exposure of a person is 100 banana equivalent doses. At 0.17 mSv per year, almost 10 percent of natural radioactive exposure in Germany (an average of 2.1 mSv per year) is caused by the body's own (vital) potassium. The banana equivalent dose does not take into account the fact that no radioactive nuclide is accumulated in the body through the consumption of potassium-containing foods. The potassium content of the body is in homeostasis and is kept constant.
=== Biosphere === Methanogenesis is a form of anaerobic respiration used by microbes, and microbial methanogenesis can occur in deep subsurface, marine sediments, freshwater bodies, etc. It appears that methane from deep subsurface and marine sediment is generally in internal isotopic equilibrium., while freshwater microbial methanogenesis expresses large kinetic isotope effect on methane clumped isotope composition. There are two possible explanations for this variance: firstly, substrate limitation may enhance the reversibility of methanogenesis, thus allowing methane to achieve internal isotopic equilibrium via rapid hydrogen exchange with water; secondly, activation of C-H bonds during anaerobic oxidation precedes reversibly such that C-H bonds are broken and reformed faster than the net rate of methane consumption and methane can be reequilibrated.
=== MSEIRS model === An MSEIRS model is similar to the MSEIR, but the immunity in the R class would be temporary, so that individuals would regain their susceptibility when the temporary immunity ended.
Sources: en.wikipedia.org
After Harrison Stanford Martland (1883-1954), chief medical examiner in Essex County, detected the radioactive noble gas radon (a decay product of radium) in the breath of the Radium Girls, he turned to Charles Norris (1867-1935) and Alexander Oscar Gettler (1883-1968). In 1928, Gettler was able to detect a high concentration of radium in the bones of Amelia Maggia, one of the young women, even five years after her death. In 1931, a method was developed for determining radium dosage using a film dosimeter. A standard preparation is irradiated through a hardwood cube onto an X-ray film, which is then blackened. For a long time, the cube minute was an important unit of radium dosage. It was calibrated by ionometric measurements. The radiologists Hermann Georg Holthusen (1886-1971) and Anna Hamann (1894-1969) found a calibration value of 0.045 r/min in 1932/1935. The calibration film receives the y-ray dose of 0.045 r per minute through the wooden cube from the preparation of 13.33 mg. In 1933, the physicist Robley D. Evans (1907-1995) made the first measurements of radon and radium in the excretions of female workers. On this basis, the National Bureau of Standards, the predecessor to the National Institute of Standards and Technology (NIST), set the limit for radium at 0.1 microcuries (about 3.7 kilobecquerels) in 1941. A Radium Action Plan 2015-2019 aims to solve the problem of radiological contamination in Switzerland, mainly in the Jura Mountains, due to the use of radium luminous paint in the watch industry until the 1960s.
Corticotropic cells, (corticotropes or corticotrophs) are basophilic cells in the anterior pituitary that produce pro-opiomelanocortin (POMC) which undergoes cleavage to adrenocorticotropin (ACTH), β-lipotropin (β-LPH), and melanocyte-stimulating hormone (MSH). These cells are stimulated by corticotropin releasing hormone (CRH) and make up 15–20% of the cells in the anterior pituitary. The release of ACTH from the corticotropic cells is controlled by CRH, which is formed in the cell bodies of parvocellular neurosecretory cells within the paraventricular nucleus of the hypothalamus and passes to the corticotropes in the anterior pituitary via the hypophyseal portal system. Adrenocorticotropin hormone stimulates the adrenal cortex to release glucocorticoids and plays an important role in the stress response.
== DNA analysis == The bone fragment, identified by the code DC1227 (GenBank Accession = KU131206) or as Denisova 11, may have originated from a human arm or leg. Prior to the extraction of material for genetic analysis, DC1227 weighed 1.68 g (0.059 oz), and had maximum dimensions of 24.7 mm (0.97 in) by 8.39 mm (0.330 in). In 2016, a team from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, led by paleogeneticists Viviane Slon and Svante Pääbo, extracted six DNA samples and produced ten libraries of complete genome sequences to an average coverage of 2.6-fold. Isolated mitochondrial DNA and nuclear DNA indicated the archaic human was of nearly equal proportion Neanderthal and Denisovan. A comparison of the specimen's X chromosomes and autosomes showed it belonged to a female. The estimated heterozygosity of Denisova 11, found to be comparable to present day Africans suggests that the girl was a first-generation Neanderthal-Denisovan hybrid. Subsequent analyses showed a high likelihood that her Denisovan father also had some Neanderthal ancestry introduced into his genome hundreds of generations before his lifetime. Denisova 11's genome thus constitutes the first direct evidence for at least two instances of interbreeding between Neanderthals and Denisovans.
== Interactions == Since amitriptyline and its active metabolite nortriptyline are primarily metabolized by cytochromes CYP2D6 and CYP2C19 (see its pharmacology), the inhibitors of these enzymes are expected to exhibit pharmacokinetic interactions with amitriptyline. According to the prescribing information, the interaction with CYP2D6 inhibitors may increase the plasma level of amitriptyline. However, the results in the other literature are inconsistent: the co-administration of amitriptyline with a potent CYP2D6 inhibitor paroxetine does increase the plasma levels of amitriptyline two-fold and of the main active metabolite nortriptyline 1.5-fold, but combination with less potent CYP2D6 inhibitors thioridazine or levomepromazine does not affect the levels of amitriptyline and increases nortriptyline by about 1.5-fold; A case of clinically significant interaction with potent CYP2D6 inhibitor terbinafine has been reported. A potent inhibitor of CYP2C19 and other cytochromes fluvoxamine increases the level of amitriptyline two-fold while slightly decreasing the level of nortriptyline. Similar changes occur with a moderate inhibitor of CYP2C19 and other cytochromes cimetidine: amitriptyline level increases by about 70%, while nortriptyline decreases by 50%. CYP3A4 inhibitor ketoconazole elevates amitriptyline level by about a quarter. On the other hand, cytochrome P450 inducers such as carbamazepine and St. John's Wort decrease the levels of both amitriptyline and nortriptyline Oral contraceptives may increase the blood level of amitriptyline by as high as 90%.
Sources: en.wikipedia.org
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。
Semax 被描述为 ACTH(4-10) 的结构类似物，两者共享部分序列特征。它保留了该片段的部分神经相关活性方向，但去除了完整片段带来的激素释放效应。二者并非同一物质，也不能互相替代。
加入的 Pro-Gly-Pro 三肽被普遍认为能提升分子对蛋白水解酶的稳定性。这种设计让短肽在体内维持时间更长。具体延长的程度以及不同组织中是否一致，文献中仍存在不同报告。
Solid peptide is best kept frozen at about minus 20 degrees Celsius in a sealed container with desiccant. It should be allowed to reach room temperature before opening to prevent condensation. Repeated warming and cooling of the same vial is discouraged.