RP-HPLC is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-04-16. Where a claim depends on a specific study, the study is described rather than over-claimed.
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。
Lyophilised powder is normally kept at -20 °C in a desiccated container, with some suppliers recommending -80 °C for long-term archival storage. Repeated freeze-thaw cycles are the most common cause of avoidable loss, so aliquoting before freezing reduces variability between working sessions. Dissolved peptide is far less stable than the dry solid and is usually prepared fresh or held briefly at 4 °C. Aqueous solutions support both hydrolysis of the backbone and oxidation of the N-terminal methionine, and these two routes dominate degradation under ordinary laboratory conditions.
Identity and purity are confirmed with reversed-phase high-performance liquid chromatography, typically monitored at 214 nanometres where the peptide bond absorbs. Mass spectrometry, either electrospray or MALDI-TOF, verifies molecular mass against the theoretical value and detects truncation or adduct formation. Amino acid analysis and peptide mapping provide additional confirmation when required. The most frequently reported impurities are deletion sequences from incomplete coupling, methionine sulfoxide from oxidation, and dimeric species formed through non-covalent aggregation. Impurity profiles depend strongly on the synthesis and purification route chosen by the producer.
Published research has focused mainly on neurological and cognitive endpoints in animal models, with proposed mechanisms involving brain-derived neurotrophic factor and related signalling pathways. A substantial share of the human data originates from a limited number of research groups, and independent replication in other countries remains sparse. Regulatory status reflects that distribution: the peptide is registered as a medicine in Russia and appears in some neighbouring markets, while elsewhere it is handled as a research chemical without approved therapeutic labelling. Questions about dose-response relationships, long-term effects, and comparability across studies are still open.
| 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 |
Semax is a synthetic heptapeptide whose sequence is Met-Glu-His-Phe-Pro-Gly-Pro. The first four residues correspond to the ACTH(4-10) fragment, while the terminal Pro-Gly-Pro extension was added to improve metabolic stability. Its molecular formula is C37H51N9O10S and its monoisotopic mass is approximately 813.9 Da. The compound is classified as a peptide research chemical and as a registered pharmaceutical product in Russia, but it does not hold marketing approval in the European Union or the United States. Naming conventions vary across supplier catalogs.
Development of the compound took place in the Soviet Union during the 1980s, largely through peptide research groups affiliated with the Shemyakin-Ovchinnikov Institute and Moscow State University. Investigators screened fragments of adrenocorticotropic hormone for activity on the central nervous system while attempting to separate cognitive effects from hormonal ones. The shortened sequence was selected because it retained behavioral activity in animal models without stimulating corticosteroid release. Early publications described the molecule as an ACTH(4-10) analog.
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.
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.
Published studies are dominated by animal models of stroke, ischemia, and cognitive impairment, with a smaller number of human trials conducted in Russia. Many of the human reports are small, single-center, and published in Russian-language journals, which limits independent scrutiny. Outcome measures vary between studies and often rely on clinician-rated scales rather than objective biomarkers. Systematic reviews have noted the methodological weaknesses and called for larger, preregistered trials before firm conclusions can be drawn.
Claims about enhanced focus, memory, or mood in healthy people rest mostly on anecdotal reports and community discussion rather than on controlled data. It remains unclear whether any cognitive benefit observed in patients recovering from brain injury would extend to uninjured users. Dose-response relationships, long-term safety, and interactions with other drugs are not well characterized in the peer-reviewed literature. Questions about optimal route of administration and treatment duration likewise remain open.
In the absence of a gut compartment, input can be made directly in the liver. However, in that case local metabolism in the gut may not be correctly described. The case of approximately continuous absorption (e.g. via drinking water) can be modeled by a zero-order absorption rate (here Ring in units of mass over time):
=== June === 2 June – China successfully lands Chang'e 6 on the lunar far side. The robotic probe is set to begin sample collection before returning its 2 kg (4.4 lb) cargo on 4 June. 4 June – The China National Space Administration's Chang'e 6 spacecraft lifts off from the surface of the far side of the Moon carrying samples of lunar soil and rocks back to Earth. 5 June – Astronomers identify ASKAP J1935+2148, the slowest-spinning neutron star ever recorded, which completes a rotation just once every 54 minutes. 8 June – A paper challenges the public perception and media depictions of large language models like especially ChatGPT, arguing that "bullshitting" in the sense of the book On Bullshit and a fundamentally flawed design are a better approach or terminology for understanding the flaws of these AI architectures or the behavior of the systems based on these as opposed to occasional or frequent "hallucinations". In agreement with many other experts, they find these models are in an "important way indifferent to the truth of their outputs". This notion has also been applied to Perplexity AI that is typically used for generating outputs that are less inaccurate than ChatGPT's – or contain fewer "hallucinations" – and which was scaled up substantially during 2024. An investigation by WIRED reportedly showed the chatbot at times closely paraphrased WIRED stories, and at times summarized stories inaccurately and with minimal attribution.
== Controversial terminology == A toxic heavy metal is a common but misleading term for a metal-like element noted for its potential toxicity. Not all heavy metals are toxic and some toxic metals are not heavy. The International Union of Pure and Applied Chemistry (IUPAC), which standardizes nomenclature, says the term "'heavy metals' is both meaningless and misleading". The IUPAC report focuses on the legal and toxicological implications of describing "heavy metals" as toxins when there is no scientific evidence to support a connection. The density implied by the adjective "heavy" has almost no biological consequences, and pure metals are rarely the biologically active substance. This characterization has been echoed by numerous reviews. The most widely used toxicology textbook, Casarett and Doull's Toxicology, uses "toxic metal", not "heavy metals". Nevertheless many scientific and science-related articles, including medical texts, continue to use "heavy metal" as a term for toxic substances.
Sources: en.wikipedia.org
Historical preservation methods focused on morphology and often used heat or chemicals that were detrimental to molecular integrity. Molecular work on historical specimens can also be constrained by limited specimen material and by institutional policies on destructive sampling, especially for type specimens. Institutional challenges include dwindling financial support, which has led some facilities to downsize or close; for instance, Duke University announced the dissolution of its herbarium in 2024. As funding shifts away from traditional natural history, many collections are being relocated to large, centralised repositories. Beyond financial instability, neglected collections face physical threats from pests such as the herbarium beetle (Trogoderma angustum), which can destroy centuries of accumulated biological data if not strictly managed.
Although protons were originally considered to be elementary particles, in the modern Standard Model of particle physics, protons are known to be composite particles, containing three valence quarks, and together with neutrons are now classified as hadrons. Protons are composed of two up quarks of charge +2/3e each, and one down quark of charge −1/3e. The rest masses of quarks contribute only about 1% of a proton's mass. The remainder of a proton's mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together. The proton charge radius is around 0.841 fm but two different kinds of measurements give slightly different values. At sufficiently low temperatures and kinetic energies, free protons will bind electrons in any matter they traverse. Free protons are routinely used for accelerators for proton therapy or various particle physics experiments, with the most powerful example being the Large Hadron Collider.
In the 2026 QS World University Rankings by Subject, Hong Kong's higher education sector demonstrated significant global competitiveness, with five academic programs placing within the world's top 10. The University of Hong Kong (HKU) maintained its status as the city's most decorated institution, securing global 2nd and 5th positions for Dentistry and Education, respectively. Other top-tier performances included the Chinese University of Hong Kong (CUHK) ranking 6th globally for Nursing, the Education University of Hong Kong (EdUHK) placing 7th in Education, and the Hong Kong Academy for Performing Arts (HKAPA) breaking into the top 10 for Performing Arts—the highest-ranked performing arts institution in Asia.
Sources: en.wikipedia.org
=== Pharmacokinetics === Within 4–12 hours of the oral administration of a 10-mg dose to fasting adults, the attained mean ezetimibe peak plasma concentration (Cmax) was 3.4–5.5 ng/ml. Following oral administration, ezetimibe is absorbed and extensively conjugated to a phenolic glucuronide (active metabolite). Mean Cmax (45–71 ng/ml) of ezetimibe-glucuronide is attained within 1–2 hours. The concomitant administration of food (high-fat vs. nonfat meals) does not affect the extent of absorption of ezetimibe. However, coadministration with a high-fat meal increases its Cmax by 38%. The absolute bioavailability cannot be determined, since ezetimibe is insoluble in aqueous media suitable for injection. Ezetimibe and its active metabolites are highly bound to human plasma proteins (90%). Ezetimibe is primarily metabolized in the liver and the small intestine via glucuronide conjugation with subsequent renal and biliary excretion. Both the parent compound and its active metabolite are eliminated from plasma with a half-life of around 22 hours, allowing for once-daily dosing. Ezetimibe lacks significant inhibitor or inducer effects on cytochrome P450 isoenzymes, which explains its limited number of drug interactions. No dose adjustment is needed in patients with chronic kidney disease or mild hepatic dysfunction (Child-Pugh score 5–6). Due to insufficient data, the manufacturer does not recommend ezetimibe for patients with moderate to severe hepatic impairment (Child-Pugh score 7–15).
A benign tumor is a mass of cells (tumor) that does not invade neighboring tissue or metastasize (spread throughout the body). Compared to malignant (cancerous) tumors, benign tumors generally have a slower growth rate. Benign tumors have relatively well differentiated cells. They are often surrounded by an outer surface (fibrous sheath of connective tissue) or stay contained within the epithelium. Common examples of benign tumors include moles and uterine fibroids. Some forms of benign tumors may be harmful to health. Benign tumor growth causes a mass effect that can compress neighboring tissues. This can lead to nerve damage, blood flow reduction (ischemia), tissue death (necrosis), or organ damage. The health effects of benign tumor growth may be more prominent if the tumor is contained within an enclosed space such as the cranium, respiratory tract, sinus, or bones. For example, unlike most benign tumors elsewhere in the body, benign brain tumors can be life-threatening. Tumors may exhibit behaviors characteristic of their cell type of origin; as an example, endocrine tumors such as thyroid adenomas and adrenocortical adenomas may overproduce certain hormones. The word benign means 'favourable, kind, fortunate, salutary, propitious'. However, a benign tumor is not benign in the usual sense; the name merely specifies that it is not "malignant", i.e. cancerous. While benign tumors usually do not pose a serious health risk, they can be harmful or fatal.
PAHs, subjected to interstellar medium (ISM) conditions, are transformed, through hydrogenation, oxygenation, and hydroxylation, to more complex organic compounds—"a step along the path toward amino acids and nucleotides, the raw materials of proteins and DNA, respectively". Further, as a result of these transformations, the PAHs lose their spectroscopic signature which could be one of the reasons "for the lack of PAH detection in interstellar ice grains, particularly the outer regions of cold, dense clouds or the upper molecular layers of protoplanetary disks." Low-temperature chemical pathways from simple organic compounds to complex PAHs are of interest. Such chemical pathways may help explain the presence of PAHs in the low-temperature atmosphere of Saturn's moon Titan, and may be significant pathways, in terms of the PAH world hypothesis, in producing precursors to biochemicals related to life as we know it.
Stave (1959), historian specializing in oral history and urban history Alvin Goldman (1960), professor of philosophy at Rutgers University and leading figure in epistemology William Landes (1960), economist and professor at University of Chicago Law School Rudolf Makkreel (1960), professor of philosophy at Emory University Thomas Vargish (1960), professor of English at Dartmouth College Eugene Bardach (1961), public policy scholar, professor at University of California, Berkeley Marshall Berman (1961), urbanologist Martin Eidelberg (1961), art historian at Rutgers University David Konstan (1961), professor of classics at New York University Victor Hao Li (1961), professor at Stanford Law School, president of East–West Center 1981–1989 Donald F. Roberts (1961), professor of communications at Stanford University David Syrett (1961), professor of military history at Queens College, City University of New York; former president of the New York Military Affairs Symposium Zvi Gitelman (1962), Jewish scholar at the University of Michigan Ken Jowitt (1962), political scientist and professor at University of California, Berkeley and senior fellow of the Hoover Institution Stephen Koss (1962), historian on British history Joel Moses (1962), mathematician, Institute Professor at and provost of the Massachusetts Institute of Technology Lawrence S.
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。
Reversed-phase HPLC gives the main purity figure, most often with UV detection near 214 nanometres. Mass spectrometry then confirms the molecular mass. Together the two methods distinguish a correct sequence from a closely related impurity.