If you have been reading about reversed-phase HPLC 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 2026-01-15. Where a claim depends on a specific study, the study is described rather than over-claimed.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. Its design combines the ACTH(4-7) core fragment with a C-terminal Pro-Gly-Pro extension, a modification intended to improve stability and prolong activity. The molecule is hydrophilic, carries no lipid chains or glycosylation, and has a theoretical mass just over 810 daltons in its free form. All seven residues are proteinogenic amino acids, so no non-natural building blocks appear in the backbone. A free N-terminal methionine and C-terminal proline define the unmodified parent peptide.
The compound was developed during the 1980s at the Institute of Molecular Genetics in Moscow as part of research on fragments of adrenocorticotropic hormone. Early work examined short ACTH-derived sequences that retained neurotrophic effects while lacking the endocrine activity of the full hormone. Semax entered clinical use in Russia during the 1990s, where it received registration for several neurological indications. Outside that region it remained primarily a laboratory research material rather than an approved therapeutic. English-language literature on it grew more slowly and frequently cited the original Russian studies.
Terminology around the compound varies by source. It appears in catalogues and papers as Semax, as the heptapeptide ACTH(4-7)-Pro-Gly-Pro, and under various alphanumeric laboratory codes used by individual suppliers. These names refer to the same sequence but may imply different salt forms, purity grades, or counter-ions. Peptide databases usually list the free base mass, while product descriptions sometimes report acetate or trifluoroacetate salts with a different formula weight. Because naming conventions for research peptides are not standardised across vendors, checking the declared sequence and measured mass is more reliable than relying on a trade name alone.
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 |
|---|---|---|
| Chemical class | Synthetic heptapeptide | ACTH(4-7) analogue |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Free N terminus, unmodified side chains |
| Molecular weight | 813.9 Da | Free base; salt forms differ |
| Appearance | White to off-white powder | Lyophilised solid |
| Solubility | Freely soluble in water | Hydrophilic; polar solvents preferred |
Published research on this peptide originates mainly from Russian laboratories, and the wider international literature is comparatively thin. Studies have used rodent models of stroke, hypoxia, and memory tasks, with a smaller number of human trials reported. Reported outcomes include changes in attention and memory measures, along with effects on neurotrophic factor expression in some experiments. Small sample sizes, inconsistent dosing protocols, and limited independent replication are widely noted limitations, so the strength of the clinical evidence remains an open question.
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.
Purity assessment relies mainly on reversed-phase high-performance liquid chromatography, which separates the target heptapeptide from truncated sequences, deletion analogues, and oxidised forms. Mass spectrometry, usually coupled to liquid chromatography, confirms identity through the expected molecular ion and reveals modifications such as methionine sulfoxide formation. Amino acid analysis can verify composition, and tandem mass spectrometry supports sequence confirmation. Ultraviolet detection near 254 to 280 nanometres is convenient because the phenylalanine and histidine residues absorb in that region. Nuclear magnetic resonance is rarely used for routine release testing.
Common degradation pathways include oxidation of the methionine side chain, hydrolysis of the peptide backbone, and aggregation under unfavourable pH or concentration. Stability studies typically monitor the main peak by chromatography and report total related substances as a percentage. Because no official monograph exists, acceptance criteria vary between laboratories, and reported purity values are not directly comparable across suppliers. Analysts therefore document the method, column, and detection wavelength alongside each result, and open questions remain about how much biological activity the oxidised forms retain.
Laboratory descriptions of the material are consistent across suppliers. It appears as a white to off-white lyophilized powder that dissolves readily in water and in polar organic solvents such as dimethyl sulfoxide. Aqueous solutions are clear and colorless at low concentrations. Because the peptide contains methionine, oxidation at the sulfur atom is a recognized degradation pathway, and handling notes usually call for protected, desiccated storage. Reported purity for research-grade lots is generally above 95 percent as measured by reversed-phase high-performance liquid chromatography.
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.
== Further reading == Aikin, Jane (2010). "Histories of the Library of Congress". Libraries & the Cultural Record. 45 (1): 5–24. doi:10.1353/lac.0.0113. S2CID 161865550. Anderson, Gillian B. (1989), "Putting the Experience of the World at the Nation's Command: Music at the Library of Congress, 1800–1917", Journal of the American Musicological Society, 42 (1): 108–49, doi:10.2307/831419, JSTOR 831419 Bisbort, Alan, and Linda Barrett Osborne. The Nation's Library: The Library of Congress, Washington, D. C. (Library of Congress, 2000) Cole, John Young. Jefferson's legacy: a brief history of the Library of Congress (Library of Congress, 1993) Cole, John Young. "The library of congress becomes a world library, 1815–2005." Libraries & culture (2005) 40#3: 385–398. in Project MUSE Cope, R. L. "Management Review of the Library of Congress: The 1996 Booz Allen & Hamilton Report," Australian Academic & Research Libraries (1997) 28#1 online Mearns, David Chambers. The Story Up to Now: The Library of Congress, 1800–1946 (1947), detailed narrative Ostrowski, Carl. Books, Maps, and Politics: A Cultural History of the Library of Congress, 1783–1861 (2004) Rosenberg, Jane Aiken. The Nation's Great Library: Herbert Putnam and the Library of Congress, 1899–1939 (University of Illinois Press, 1993) Shevlin, Eleanor F.; Lindquist, Eric N. (2010). "The Center for the Book and the History of the Book". Libraries & the Cultural Record. 45 (1): 56–69. doi:10.1353/lac.0.0112. S2CID 161311744. Tabb, Winston; et al. (2003). "Library of Congress". Encyclopedia of Library and Information Science.
Replacing natural polyunsaturated fatty acids (PUFA) with deuterated PUFA (dPUFA), which have deuterium in place of the bis-allylic hydrogens, can prevent cell death induced by erastin or RSL3. These deuterated PUFAs effectively inhibit ferroptosis and various chronic degenerative diseases associated with ferroptosis. Live-cell imaging has been used to observe the morphological changes that cells undergo during ferroptosis. Initially the cell contracts and then begins to swell. Perinuclear lipid assembly is observed immediately before ferroptosis occurs. After the process is complete, lipid droplets are redistributed throughout the cell (see GIF on right side).
The drug must be found to be effective against the disease for which it is seeking approval (where 'effective' means only that the drug performed better than placebo or competitors in at least two trials). The drug must meet safety criteria by being subject to animal and controlled human testing. Gaining FDA approval usually takes several years. Testing done on animals must be extensive and must include several species to help in the evaluation of both the effectiveness and toxicity of the drug. The dosage of any drug approved for use is intended to fall within a range in which the drug produces a therapeutic effect or desired outcome. The safety and effectiveness of prescription drugs in the U.S. are regulated by the federal Prescription Drug Marketing Act of 1987. The Medicines and Healthcare products Regulatory Agency (MHRA) has a similar role in the UK. Medicare Part D is a prescription drug plan in the U.S. The Prescription Drug Marketing Act (PDMA) is an act related to drug policy. Prescription drugs are drugs regulated by legislation.
=== Susceptible organisms === Teicoplanin has demonstrated in vitro efficacy against Gram-positive bacteria including staphylococci (including MRSA), streptococci, enterococci, and against anaerobic Gram-positive bacteria including Clostridium spp. Teicoplanin is ineffective against Gram-negative bacteria as the large, polar molecules of the compound are unable to pass through the external membrane of these organisms. The following represents MIC susceptibility data for a few medically significant pathogens:
Sources: en.wikipedia.org
For a better understanding of the stiffness and strain of resilin, Hooke's law should be taken into consideration. For linear springs, Hooke's law states that the force required to deform the spring is directly proportional to the amount of deformation by a constant which is the characteristic of the spring. A material is viewed as elastic when it can be deformed to a large extend with a limited amount of force. Hydrated resilin has a tensile modulus of 640–2000 kPa, an unconfined compressive modulus of 600–700 kPa, and a strain to break of 300%.
== Mechanisms == Addiction develops when repeated exposure to a rewarding stimulus produces lasting changes in the brain circuits that govern reward, stress and self-control. Current accounts describe this as a recurring three-stage cycle. During binge/intoxication, dopaminergic signaling in the basal ganglia gives the drug and the cues surrounding it a powerful pull on attention and behavior. During withdrawal/negative affect, brain stress systems in the extended amygdala become overactive and ordinary pleasures become muted, so that use is increasingly driven by relief rather than reward. During preoccupation/anticipation, reduced prefrontal cortex control over these systems leaves craving poorly restrained and makes relapse more likely. Each stage is associated with persistent changes in gene expression and synaptic plasticity within the affected circuits. In laboratory animals, repeated drug exposure causes a protein called ΔFosB to accumulate in reward-related neurons, which increases drug self-administration and blunts sensitivity to adverse consequences; it is used in preclinical research as a marker of addiction.
== Drug interactions == Thiotepa can have various interactions with other medications or therapies that can impact patient safety and treatment efficacy. Aprepitant, a drug that prevents nausea and vomiting that may occur during chemotherapy, inhibits CYP-enzymes, which decrease the metabolism of thiotepa to tepa. Its importance is relatively minor because inhibition itself is small and due to the variability of thiotepa clearance in different individuals. The anti-seizure medication phenytoin induces the CYP3A4 enzyme. This leads to an increased rate of tepa formation from thiotepa, which highly influences its clearance and concentration. Higher local concentrations of the more reactive tepa can potentially induce hepatotoxicity. Additionally, cytotoxic drugs such as thiotepa can reduce the absorption of phenytoin leading to the increased risk of seizures. It is advised to avoid the use of both drugs simultaneously or decrease thiotepa doses. Myelosuppressive/myelotoxic agents such as melphalan, busulfan, treosulfan, and cyclophosphamide, as well as the concurrent use of thiotepa, may increase the risk of hematologic adverse reactions and pulmonary toxicity, as they share similar toxicity profiles. Additionally, the use of live attenuated vaccines (including yellow fever) poses a risk of systemic and potentially fatal infection, with the risk further heightened in patients who are already immunosuppressed due to their underlying disease.
=== Further manifestations of solvent hydrogen bonding === Increase in the melting point, boiling point, solubility, and viscosity of many compounds can be explained by the concept of hydrogen bonding. Negative azeotropy of mixtures of HF and water. The fact that ice is less dense than liquid water is due to a crystal structure stabilized by hydrogen bonds. Dramatically higher boiling points of NH3, H2O, and HF compared to the heavier analogues PH3, H2S, and HCl, where hydrogen-bonding is absent. Viscosity of anhydrous phosphoric acid and of glycerol. Dimer formation in carboxylic acids and hexamer formation in hydrogen fluoride, which occur even in the gas phase, resulting in gross deviations from the ideal gas law. Pentamer formation of water and alcohols in apolar solvents.
== Discovery == The technique was invented in 1955 by Grant Henry Lathe and Colin R Ruthven, working at Queen Charlotte's Hospital, London. They later received the John Scott Award for this invention. While Lathe and Ruthven used starch gels as the matrix, Jerker Porath and Per Flodin later introduced dextran gels; other gels with size fractionation properties include agarose and polyacrylamide. A short review of these developments has appeared. There were also attempts to fractionate synthetic high polymers; however, it was not until 1964, when J. C. Moore of the Dow Chemical Company published his work on the preparation of gel permeation chromatography (GPC) columns based on cross-linked polystyrene with controlled pore size, that a rapid increase of research activity in this field began. It was recognized almost immediately that with proper calibration, GPC was capable to provide molar mass and molar mass distribution information for synthetic polymers. Because the latter information was difficult to obtain by other methods, GPC came rapidly into extensive use.
Sources: en.wikipedia.org
Factors contributing to the anarchist animosity towards the USSR included the Soviet destruction of the Makhnovist movement after an initial alliance, the suppression of the anarchist Kronstadt rebellion, and the defeat of the rival anarchist factions by the Soviet-supported Communist faction during the Spanish Civil War. Maoists also have a mixed opinion on the USSR, viewing it negatively during the Sino-Soviet Split and denouncing it as revisionist and reverted to capitalism. The Chinese government in 1963 articulated its criticism of the USSR's system and promoted China's ideological line as an alternative. After the dissolution of the Soviet Union, the Japanese Communist Party (JCP) released a press statement titled "We welcome the end of a party which embodied the historical evil of great power chauvinism and hegemonism". Noam Chomsky called the collapse of the Soviet Union "a small victory for socialism, not only because of the fall of one of the most anti-socialist states in the world, where working people had fewer rights than in the West, but also because it freed the term 'socialism' from the burden of being associated in the propaganda systems of East and West with Soviet tyranny—for the East, in order to benefit from the aura of authentic socialism, for the West, in order to demonize the concept."
systemic medial calcification of the arteries, i.e. calcification of tunica media. Unlike other forms of vascular calcifications (e.g., intimal, medial, valvular), calciphylaxis is characterized also by small vessel mural calcification with or without endovascular fibrosis, extravascular calcification and vascular thrombosis, leading to tissue ischemia (including skin ischemia and, hence, skin necrosis).
In June 2021, the US Senate approved the U.S. Innovation and Competition Act providing around 250 billion US dollars public money support to the US technological and manufacturing industry. The alleged Chinese threat in the area of technology helped secure a strong bipartisan support for the new legislation, amounting to the largest industrial policy move by the US in decades. Chinese authorities reproached to the US that the bill was “full of cold war zero-sum thinking”.
Customs and Border Protection, United States Border Patrol, and the United States Coast Guard), state (e.g., Massachusetts State Police Special Investigation Unit, New Jersey State Police organized crime unit, Pennsylvania State Police organized crime unit and the New York State Police Bureau of Criminal Investigation) and city (e.g., New York City Police Department Organized Crime Unit, Philadelphia Police Department Organized crime unit, Chicago Police Organized Crime Unit and the Los Angeles Police Department Special Operations Division) law enforcement agencies.
== External links == First look at the structure of human TG Thyroglobulin – Lab Tests Online Histology at KUMC endo-endo11 Overview at colostate.edu Histology image: 14302loa – Histology Learning System at Boston University
Sources: en.wikipedia.org
It is a synthetic seven-amino-acid peptide built from the ACTH(4-7) sequence plus a Pro-Gly-Pro tail. It belongs to the family of short ACTH fragments studied for nervous-system effects. Its backbone contains only standard amino acids.
It contains the 4-7 fragment of adrenocorticotropic hormone extended at the C terminus. That truncation removes the region associated with steroidogenic activity. The design intent was to keep neurotrophic properties while avoiding full hormonal effects.
No natural source of the intact heptapeptide is known. It is produced by solid-phase peptide synthesis. Some related ACTH fragments arise as hormone processing products, but the Pro-Gly-Pro extension is a designed addition rather than a natural sequence.
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。