反相色谱 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 2025-12-26 and is reviewed periodically as new material appears.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Its chain combines the first seven residues of corticotropin with a C-terminal proline-glycine-proline extension, a modification intended to slow enzymatic breakdown. The free peptide has a molecular mass near 813.9 daltons. It belongs to the class of ACTH-derived fragments studied for central nervous system activity rather than for adrenal steroid stimulation. This structural relationship to a natural hormone fragment is the usual starting point for describing the compound in the literature.
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.
溶液状态的稳定性明显低于冻干粉。肽类在水溶液中可能经历水解、氧化与聚集，其中甲硫氨酸和天冬酰胺等残基常是敏感位点。Semax 含有甲硫氨酸，因此氧化风险相对突出。工作液一般主张现配现用，或冷藏并在数日内用尽。缓冲液种类、pH 和离子强度都会影响降解速率，而关于最佳条件的公开数据并不统一。
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。
| Property | Value | Notes |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Heptapeptide; ACTH(4-10) analog extended at C-terminus |
| Molecular mass | ~813.9 Da | Free peptide, unmodified |
| Appearance | White to off-white powder | Typical lyophilized solid |
| Solubility | Soluble in water and saline | Also soluble in common aqueous buffers |
| Storage (solid) | -20 °C, desiccated | Protect from moisture and repeated thawing |
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.
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。
=== Expression proteomics === Expression proteomics includes the analysis of protein expression at a larger scale. It helps identify main proteins in a particular sample, and those proteins differentially expressed in related samples—such as diseased vs. healthy tissue. If a protein is found only in a diseased sample then it can be a useful drug target or diagnostic marker. Proteins with the same or similar expression profiles may also be functionally related. There are technologies such as 2D-PAGE and mass spectrometry that are used in expression proteomics.
== External links == 16S rRNA, BioMineWiki Archived 2019-04-27 at the Wayback Machine Ribosomal Database Project II Archived 2020-08-19 at the Wayback Machine Ribosomal+RNA at the U.S. National Library of Medicine Medical Subject Headings (MeSH) SILVA rRNA Database Project (also includes Eukaryotes (18S) and LSU (23S/28S)) Video: rRNA: sequence, function & synthesis Halococcus morrhuae (archaebacterium) 5S rRNA
Compounds begin to break down as soon as they enter the body. The majority of small-molecule drug metabolism is carried out in the liver by redox enzymes, termed cytochrome P450 enzymes. As metabolism occurs, the initial (parent) compound is converted to new compounds called metabolites. When metabolites are pharmacologically inert, metabolism deactivates the administered dose of parent drug and this usually reduces the effects on the body. Metabolites may also be pharmacologically active, sometimes more so than the parent drug (see prodrug).
== Pharmacokinetics == Biotransformation is mainly hepatic, with approximately 30-40% metabolized to inactive metabolites. Protein Binding ranges from 60 to 80%. Cinoxacin is rapidly absorbed after oral administration. The presence of food delays absorption but does not affect total absorption. The mean serum half-life is 1.5 hours. Half-life in patients with impaired renal function may exceed 10 hours.
Sources: en.wikipedia.org
=== Harm assessment === Professor David Nutt, former chair of the Advisory Council on the Misuse of Drugs (ACMD) in the UK has said in 2009, "people are better off taking ecstasy or amphetamines than those [drugs] we know nothing about" and "Who knows what's in [mephedrone] when you buy it? We don't have a testing system. It could be very dangerous[;] we just don't know. These chemicals have never been put into animals, let alone humans." Les King, a former member of the ACMD, has stated mephedrone appears to be less potent than amphetamine and ecstasy, but that any benefit associated with this could be negated by users taking larger amounts. He also told the BBC, "all we can say is [mephedrone] is probably as harmful as ecstasy and amphetamines and wait until we have some better scientific evidence to support that."
==== Inventory in spent nuclear fuel ==== 237Np is the only neptunium isotope produced in significant quantity in the nuclear fuel cycle, both by successive neutron capture by uranium-235 (which fissions most but not all of the time) and uranium-236, or (n,2n) reactions where a fast neutron occasionally knocks a neutron loose from uranium-238 or isotopes of plutonium. Over the long term, 237Np also forms in spent nuclear fuel as the decay product of americium-241. 237Np is considered to be one of the most mobile radionuclides at the site of the Yucca Mountain nuclear waste repository (Nevada) where oxidizing conditions prevail in the unsaturated zone of the volcanic tuff above the water table.
Enterochromaffin-like cells or ECL cells are a type of neuroendocrine cell found in the gastric glands of the gastric mucosa beneath the epithelium, in particular in the vicinity of parietal cells, that aid in the production of gastric acid via the release of histamine. They are also considered a type of enteroendocrine cell.
18 February 1919: In spite of the ceasefire, there is fighting near Rynarzewo. The Poles capture the armoured train. 9 February 1919: A volunteer company of Great Polish soldiers moves to Lesser Poland to fight against the Ukrainians. 20 March 1919: The Ostmarkenzulage, a special allowance for German officials working in the eastern provinces to stimulate the German colonization of the Prussian Partition, is canceled. 23 March 1919: The Poles win a landslide in elections to the city council of Poznań. 24 March 1919: The Commission of the NRL asks the Polish government in Warsaw to create separate administration of the former Prussian Partition, as it is far more developed than the rest of the country. Ignacy Paderewski forces the government to leave all power in hands of the NRL until the final recognition of Polish-German border, with later autonomy there (only Upper Silesia would obtain it). The NRL mobilises men born in 1891, 1892, 1893, 1894 and 1901. 5 April 1919: The Sejm Ustawodawczy announces byelections in the former Province of Posen for next 42 MPs. 9 April 1919: The Commission of the NRL decrees an eight-hour workday in industry and trade. 10 April 1919: The Commission of the NRL decrees the removal of signs in German language from offices and train stations the changing of all streets names into Polish. The punishment for breaking the law is two years of prison and a fine of Mp. 10,000. 16 April 1919: The NRL decides that 3 May is the national holiday. 7 May 1919: The Wszechnica Piastowska is opened. 15 May 1919: Polish becomes the only official language.
The laboratory analysis of homocysteine itself is complicated because most homocysteine (possibly above 85%) is bound to other thiol amino acids and proteins in the form of disulphides (e.g., cysteine in cystine-homocysteine, homocysteine in homocysteine-homocysteine) via disulfide bonds. Since as an equilibrium process the proportion of free homocysteine is variable a true value of total homocysteine (free + bound) is useful for confirming diagnosis and particularly for monitoring of treatment efficacy. To this end it is prudent to perform total homocyst(e)ine analysis in which all disulphide bonds are subject to reduction prior to analysis, traditionally by HPLC after derivatisation with a fluorescent agent, thus giving a true reflection of the quantity of homocysteine in a plasma sample.
Sources: en.wikipedia.org
While nylon was marketed as the durable and indestructible material of the people, it was sold at about one-and-a-half times the price of silk stockings ($4.27 per pound of nylon versus $2.79 per pound of silk). Sales of nylon stockings were strong in part due to changes in women's fashion. As Lauren Olds explains: "by 1939 [hemlines] had inched back up to the knee, closing the decade just as it started off". The shorter skirts were accompanied by a demand for stockings that offered fuller coverage without the use of garters to hold them up. However, as of February 11, 1942, nylon production was redirected from being a consumer material to one used by the military. DuPont's production of nylon stockings and other lingerie stopped, and most manufactured nylon was used to make parachutes and tents for World War II. Although nylon stockings already made before the war could be purchased, they were generally sold on the black market for as high as $20. Once the war ended, the return of nylon was awaited with great anticipation. Although DuPont projected yearly production of 360 million pairs of stockings, there were delays in converting back to consumer rather than wartime production. In 1946, the demand for nylon stockings could not be satisfied, which led to the nylon riots. In one instance, an estimated 40,000 people lined up in Pittsburgh to buy 13,000 pairs of nylons. In the meantime, women cut up nylon tents and parachutes left from the war in order to make blouses and wedding dresses.
US Patent for PCR Archived 16 October 2011 at the Wayback Machine What is PCR plateau effect? YouTube tutorial video History of the Polymerase Chain Reaction from the Smithsonian Institution Archives Veritasium (26 December 2024). The Man Who Took LSD and Changed The World. Retrieved 29 January 2025 – via YouTube.
For their launch into space, there is today an unused superpower rocket, Energia, which is the most powerful in the world. In the late 1980s, the Soviet Union built the Mir orbital station. It was built on the construction of Salyut stations and its only role was civilian-grade research tasks. Mir was the only orbital station in operation from 1986 to 1998. Gradually, other modules were added to it, including American modules. However, the station deteriorated rapidly after a fire on board and was deorbited in 2001, burning up in the Earth's atmosphere.
==== Fenestrated ==== Fenestrated capillaries have pores known as fenestrae (Latin for "windows") in the endothelial cells that are 60–80 nanometres (nm) in diameter. They are spanned by a diaphragm of radially oriented fibrils that allows small molecules and limited amounts of protein to diffuse. In the renal glomerulus the capillaries are wrapped in podocyte foot processes or pedicels, which have slit pores with a function analogous to the diaphragm of the capillaries. Both of these types of blood vessels have continuous basal laminae and are primarily located in the endocrine glands, intestines, pancreas, and the glomeruli of the kidney.
Sources: en.wikipedia.org
Semax is a synthetic seven-amino-acid peptide derived from a fragment of corticotropin. It is used in Russia as a nasal preparation, while elsewhere it is studied as a research compound. It is not approved as a medicine in most countries.
Its sequence corresponds to the 4-10 region of corticotropin extended by three residues. This fragment lacks the region responsible for adrenal steroid release, so it is explored for neural rather than hormonal effects. The relationship explains the compound's classification among ACTH-derived peptides.
It holds approval in Russia for several neurological indications as a nasal spray or drop formulation. Regulatory agencies in the United States and the European Union have not approved it. Products sold elsewhere are generally labeled for research use only.
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。