The short version of RP-HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-08-29. Anything still debated is marked as such rather than presented as settled.
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.
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.
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。
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C or below | Desiccated and protected from light |
| Solution storage temperature | -80 °C as single-use aliquots | Avoid repeated freeze-thaw cycles |
| Purity assessment method | RP-HPLC, around 214 nm | Reported as main-peak area percent |
| Identity confirmation method | ESI-MS or MALDI-TOF | Measured mass compared with calculated mass |
| Common synonyms | ACTH(4-10) analog; Met-Glu-His-Phe-Pro-Gly-Pro | Also written as Semaxum in some sources |
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.
Later generations of the molecule include an N-acetylated form and an amidated form, both marketed online alongside the parent peptide. These variants differ in terminal chemistry and stability, and they are frequently discussed in the same breath even though they have not been compared in controlled trials. Supply outside formal healthcare systems comes largely from laboratories that synthesize peptides to order. Purity and identity of these materials vary widely, and no single body oversees the international trade.
Semax is a synthetic heptapeptide developed in the Soviet Union during the 1980s by researchers at the Institute of Molecular Genetics in Moscow. It was designed as a truncated analog of adrenocorticotropic hormone, retaining only the fragment spanning residues four through ten. Investigators sought a peptide that would preserve the cognitive effects associated with ACTH while eliminating the hormonal stimulation of the adrenal cortex. The compound entered clinical use in Russia during the following decade.
Russian regulatory authorities approved the peptide for nasal administration, and it remains listed in the national pharmacopoeia under several trade names. Documented indications include acute ischemic stroke, transient ischemic attacks, traumatic brain injury, and certain ophthalmological and neurological conditions. Physicians also prescribe it for cognitive complaints in older patients, although the evidence base for that use is thinner. Outside Russia and a few neighboring states, the substance is not an approved medicine and is sold instead as a research chemical.
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.
Pharmacological accounts link semax to melanocortin signalling and to modulation of neurotrophic factor expression, particularly brain-derived neurotrophic factor and nerve growth factor. Much of this evidence comes from rodent studies using intranasal delivery, a route chosen because it allows peptides to reach the central nervous system with limited systemic exposure. Whether the same mechanisms operate in humans at comparable magnitude remains an open question. The precise receptor or receptors responsible for the reported behavioural and neuroprotective effects have not been conclusively identified.
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.
=== Characters and setting === Decay is set in the same location and timeframe as Half-Life. Half-Life takes place at a laboratory called the Black Mesa Research Facility, situated in a remote desert in New Mexico. In Half-Life, the player takes on the role of Gordon Freeman, a scientist involved in an accident that opens an inter-dimensional portal to the borderworld of Xen, allowing the alien creatures of Xen to attack the facility. The player guides Freeman in an attempt to escape the facility and close the portal, ultimately traveling to Xen to do so. Like the previous expansions, Decay shows the story of Half-Life from the perspective of a different set of protagonists. In Decay, players assume the roles of Colette Green and Gina Cross, two doctors who work in the same labs as Freeman, analyzing anomalous materials and specimens retrieved from Xen in prior teleportation experiments. After the experiment that causes the alien invasion takes place, Green and Cross must work with two ranking members of the science team, Dr. Richard Keller and Dr. Rosenberg, to contain and stabilize the deteriorating situation in Black Mesa.
=== Hydrogen isotope formation === 1H, with one proton and no neutrons, is the most abundant nuclide in the Solar System, formed in the earliest rounds of stellar explosions after the Big Bang. After the universe exploded into life, the hot and dense cloud of particles began to cool, first forming subatomic particles like quarks and electrons, which then condensed to form protons and neutrons. Elements larger than hydrogen and helium were produced with successive stars, forming from the energy released during supernovae. Deuterium, 2H, with one proton and one neutron, is also known to have cosmic origin. Like protium, deuterium was produced very early in the universe's history, during Big Bang nucleosynthesis (BBN). As protons and neutrons combined, helium-4 was produced with a deuterium intermediate. Alpha reactions with 4He produce many of the larger elements that dominate today's Solar System. However, before the universe cooled, high-energy photons destroyed any deuterium, preventing larger element formation. This is called the deuterium bottleneck, a restriction on the timeline for nucleosynthesis. All of today's deuterium originated from this proton-proton fusion after enough cooling. Tritium, 3H, with one proton and two neutrons, was produced by proton and neutron collisions in the early universe as well, but it has since radioactively decayed to helium-3. Today's tritium cannot be from BBN, due to tritium's short half-life, 12.3 years. Today's 3H concentration is instead governed by nuclear reactions and cosmic rays.
Other theories of inheritance preceded Mendel's work. A popular theory during the 19th century, and implied by Charles Darwin's 1859 On the Origin of Species, was blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents. Mendel's work provided examples where traits were definitely not blended after hybridization, showing that traits are produced by combinations of distinct genes rather than a continuous blend. Blending of traits in the progeny is now explained by the action of multiple genes with quantitative effects. Another theory that had some support at that time was the inheritance of acquired characteristics: the belief that individuals inherit traits strengthened by their parents. This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrong—the experiences of individuals do not affect the genes they pass to their children. Other theories included Darwin's pangenesis (which had both acquired and inherited aspects) and Francis Galton's reformulation of pangenesis as both particulate and inherited.
Sources: en.wikipedia.org
It is indeed simultaneously realized that the TLC methods used thus far in almost all published studies on INMT and DMT biosynthesis are incapable to resolve DMT from those tetrahydro-β-carbolines. These findings are a blow for all previous claims of evidence of INMT activity and DMT biosynthesis in avian and mammalian brain, including in vivo, as they all relied upon use of the problematic TLC methods: their validity is doubted in replication studies that make use of improved TLC methods, and fail to evidence DMT-producing INMT activity in rat and human brain tissues. Published in 1978, the last study attempting to evidence in vivo INMT activity and DMT production in brain (rat) with TLC methods finds biotransformation of radiolabeled tryptamine into DMT to be real but "insignificant". Capability of the method used in this latter study to resolve DMT from tetrahydro-β-carbolines is questioned later. To localize INMT, a qualitative leap is accomplished with use of modern techniques of molecular biology, and of immunohistochemistry. In humans, a gene encoding INMT is determined to be located on chromosome 7. Northern blot analyses reveal INMT messenger RNA (mRNA) to be highly expressed in rabbit lung, and in human thyroid, adrenal gland, and lung. Intermediate levels of expression are found in human heart, skeletal muscle, trachea, stomach, small intestine, pancreas, testis, prostate, placenta, lymph node, and spinal cord. Low to very low levels of expression are noted in rabbit brain, and human thymus, liver, spleen, kidney, colon, ovary, and bone marrow.
Narrated by Piers Gibbon, produced by Will Aslett, directed by Peter Webber, made with Discovery Channel 12 April Living Dangerously, about people who take risks, if that involves low monoamine oxidase, with John Henry (toxicologist); two base jumpers, John and Elliott, climb a 500 ft television transmitter in December 1998; men have lower levels of MAO than women, and MAO increases with age, so men in their 20s have the least aversion to risk; possible dangers of the Minulet contraceptive (ethinylestradiol/gestodene); health scares may be out of proportion to the risk involved, and is overegging the pudding. Directed by Chris Wells, produced by Hilary Lawson, made by TVF Media with the Discovery Channel 19 April Riddle of the Leaning Tower, about the Leaning Tower of Pisa; in 1995, the tower was moving at 1mm a year; civil engineer John Burland; construction began in 1172, and construction stopped for 100 years; Piero Pierotti of the University of Pisa; the 1997 Umbria and Marche earthquake took place on 26 September 1997; haste was required, so in 1998 soil extraction was approved to attempt to moderate the lean of the tower; soil extraction began in February 1999, and the tower began to move.
The most important source of alkanes is natural gas and crude oil. Alkanes are separated in an oil refinery by fractional distillation. Unsaturated hydrocarbons are converted to alkanes by hydrogenation:
As an AAS, ethylestrenol is an agonist of the androgen receptor (AR), similarly to androgens like testosterone and dihydrotestosterone (DHT). It has low estrogenic activity (via aromatization into ethylestradiol following transformation into norethandrolone), strong progestogenic activity, and a high ratio of anabolic to androgenic activity, similarly to other nandrolone derivatives. Like other 17α-alkylated AAS, ethylestrenol has a risk of hepatotoxicity.
Sources: en.wikipedia.org
Fluorescent labeling is known for its non-destructive nature and high sensitivity. This has made it one of the most widely used methods for labeling and tracking biomolecules. Several techniques of fluorescent labeling can be utilized depending on the nature of the target.
Federalism has a long tradition in German history. Until the early 19th century, the majority of the territory that later became Germany was part of the Holy Roman Empire, which in 1796 was made up of more than 300 individual political entities subject to the Holy Roman Emperor in Vienna. The number of states was greatly reduced during the Napoleonic Wars (1796–1814), and the Empire itself was abolished in 1806. The Congress of Vienna, which restructured Europe after the wars, created the highly federalized 39-state German Confederation in 1815. The Confederation was dissolved after the Austro-Prussian War (1866) in which Prussia defeated the Austrian Empire and effectively excluded it from taking part in the eventual unification of Germany. Following the war, the states of northern and central Germany united under the leadership of the Kingdom of Prussia to form the federal North German Confederation. During the Franco-Prussian War (1870–1871), the four southern German states of Bavaria, Württemberg, Baden and Hesse-Darmstadt joined the North German Confederation, which was rechristened the German Empire with Prussia's victory. The Reichstag and Federal Council (Bundesrat) gave the Prussian king the title of German Emperor (as of 1 January 1871). With only relatively minor changes that did not affect its federalized nature, the North German Constitution became the imperial constitution. The new German Empire included 25 states (three of them free cities) plus the imperial territory of Alsace–Lorraine, which had been won from France in the war.
Alcapurrias are a traditional snack with masa dough made from grated green banana, yautía, seasoned with lard, annatto and stuffed with picadillo. Alcaparrado de plátano have additional grated plantain added to the masa. Mofongo is a beloved dish on the island celebrating a blend of cultures making it one of Puerto Ricos most important dishes. Plantains are fried once and mashed with garlic, fat (butter, lard or olive oil), chicharrón or bacon, and broth it is then formed into a ball and eaten with other meats, soup, vegetables or alone. Puerto Rican piononos are sweet and savory treats made with a combination of fried yellow plantains, cheese, picadillo, and beaten eggs. The result is sweet plantain cups stuffed with a cheese, ground beef and fluffy egg filling. Ralleno de plátano are the sweet plantain verson of papa rellena very popular street food and in cuchifritos.
== Detection in biological specimens == The presence of melamine in urine specimens from children who consumed adulterated milk products has been determined by liquid chromatography-mass spectrometry.
Some of these have also been reported as inhibitors of certain OATPs: pazopanib and nilotinib against OATP-1B1 and vandetanib against OATP-1B3. They also transport the dye bromsulfthalein, availing it as a liver-testing substance.
Sources: en.wikipedia.org
Each freeze-thaw cycle can degrade a fraction of the peptide and promote aggregation. Dividing a stock solution into single-use volumes removes repeated cycling as a variable. It also limits the time a thawed solution spends at room temperature.
A high main-peak percentage says little about identity, counter-ion content, or residual solvents. It also does not distinguish an isomer or a closely eluting analog. Mass confirmation and the accompanying documentation cover those gaps.
Salt form changes mass, solubility, and hygroscopicity, and acetate and trifluoroacetate salts behave differently in solution. Storage guidance still centers on -20 °C for powder and lower temperatures for solutions. The certificate should state which salt is present.
不存在。它是依据 ACTH 的一段序列人工设计的分子，天然蛋白质中找不到与之完全相同的七肽。名称属于研究代号，而非天然物质名。