The short version of methionine sulfoxide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-05-26 and is reviewed periodically as new material appears.
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.
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。
从分子层面看，Semax 是线性七肽，没有二硫键、糖基或脂链修饰，N 端为游离氨基，C 端为游离羧基。分子含组氨酸与谷氨酸侧链，因此在水和甲醇等极性溶剂中溶解良好，在非极性溶剂中溶解有限。计算分子量约为 814 Da，与其质子化离子的质荷比吻合，可用于质谱确认。
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C37H51N9O10S | Seven-residue peptide |
| Molecular mass | 813.9 Da | Monoisotopic value |
| Appearance | White to off-white powder | Lyophilized form |
| Solubility | Freely soluble in water | Also soluble in saline and polar solvents |
| Storage (dry) | -20 °C or lower | Desiccated, protected from light |
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.
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。
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.
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.
Dissolution is normally performed in water, phosphate-buffered saline, or normal saline, since the peptide is freely soluble in aqueous media and is rarely handled with strong organic solvents. Solution pH should be kept near neutral, because extreme acidity or alkalinity accelerates backbone hydrolysis and encourages oxidation of the methionine side chain. Once dissolved, the material is less stable than the dry powder and is commonly divided into single-use portions and frozen. Buffers containing primary amines, such as Tris, are often avoided because of possible side reactions.
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.
=== Antimalarial === Doxycycline is active against the erythrocytic stages of Plasmodium falciparum, a protozoan parasite that causes malaria, but it is not active against the gametocytes of P. falciparum. As such, doxycycline is used to prevent malaria, but not recommended alone for initial treatment of malaria, even when the parasite is doxycycline-sensitive, because the antimalarial effect of doxycycline is delayed by 48 to 96 hours owing to a "delayed death" mechanism in which parasites complete their current replication cycle before dying in the next cycle. For this reason, doxycycline prophylaxis must be continued for four weeks after leaving a malarious area, compared with only seven days for atovaquone/proguanil. Doxycycline blocks protein production in the apicoplast (an organelle) of P. falciparum. This disrupts the parasite's ability to produce fatty acids, which are essential for its growth, and impairs the production of heme, a cofactor. These effects occur late in the parasite's life cycle during the blood stage (the erythrocytic cycle, when the parasite replicates inside human red blood cells). By blocking important processes in the parasite, doxycycline both inhibits the growth and prevents the replication of P. falciparum. Doxycycline does not directly kill living P. falciparum, but creates conditions that prevent their growth and replication. The World Health Organization (WHO) guidelines state that the combination of doxycycline with either artesunate or quinine may be used for the treatment of uncomplicated malaria due to P.
=== Physical pressures === Elite athletes have financial competitive motivations that cause them to dope and these motivations differ from that of recreational athletes. The common theme among these motivations is the pressure to physically perform. In a study of 101 individuals, 86% responded that their use of performance enhancement drugs were influenced by the potential athletic success, 74% by the economic aspect, and 30% by self-confidence and social recognition related reasons. In another study of 40 people, it was concluded that athletes used performance enhancement drugs for healing purposes so that they were an able competitor for the economic rewards involved with elite sports. Physical pressures often overlap with social pressures to have a certain body build. This is the case with muscle dysmorphia, where an athlete wants a more muscular physique for functionality and self- image purposes. The most popular motive for athletes to take supplements is to prevent any nutrient deficiencies and to strengthen the immune system. These factors all focus on improving the body for performance.
== Limitations == Because the Edman degradation proceeds from the N-terminus of the protein, it will not work if the N-terminus has been chemically modified (e.g. by acetylation or formation of pyroglutamic acid). Sequencing will stop if a non-α-amino acid is encountered (e.g. isoaspartic acid), since the favored five-membered ring intermediate is unable to be formed. Edman degradation is generally not useful to determine the positions of disulfide bridges. Protein sequencing of attomole level of Edman degraded sequences are obtainable but require accelerator mass spectrometery which requires large, complex, and expensive equipment as well as 30 hours of bench time to analyze a single run.
Oil money funded social welfare programs, leading to housebuilding projects and improved healthcare and education. House building became a major social priority to eliminate homelessness and replace the shanty towns created by Libya's growing urbanization. The health sector was also expanded; by 1978, Libya had 50 per cent more hospitals than it had in 1968, while the number of doctors had increased from 700 to over 3,000 in that decade. Malaria was eradicated, and trachoma and tuberculosis greatly curtailed. Compulsory education was expanded from 6 to 9 years, while adult literacy programs and free university education were introduced. Beida University was founded, while Tripoli University and Benghazi University were expanded. In doing so, the government helped integrate the poor into the education system. Through these measures, the RCC greatly expanded the public sector, providing employment for thousands. These early social programs proved popular within Libya, partly due to Gaddafi's personal charisma, youth, underdog status as a Bedouin, and his rhetoric emphasizing himself as a successor to the anti-Italian fighter Omar al-Mukhtar. To combat the country's strong regional and tribal divisions, the RCC promoted the idea of a unified pan-Libyan identity. They discredited tribal leaders as agents of the old regime, and in August 1971 a Sabha military court tried many of them for counter-revolutionary activity.
Sources: en.wikipedia.org
In September 2020, an in vitro and in vivo study found that DMT present in the ayahuasca infusion promotes neurogenesis. DMT has been found to be a psychoplastogen, a compound capable of promoting rapid and sustained neuroplasticity that may have wide-ranging therapeutic benefit. The cryo-EM structures of the serotonin 5-HT2A receptor with DMT, as well as with various other psychedelics and serotonin 5-HT2A receptor agonists, have been solved and published by Bryan L. Roth and colleagues.
==== Clay ==== The clay hypothesis was proposed by Graham Cairns-Smith in 1985. It postulates that complex organic molecules arose gradually on pre-existing, non-organic replication surfaces of silicate crystals in contact with an aqueous solution. The clay mineral montmorillonite has been shown to catalyze the polymerization of RNA in aqueous solution from nucleotide monomers, and the formation of membranes from lipids. In 1998, Hyman Hartman proposed that "the first organisms were self-replicating iron-rich clays which fixed carbon dioxide into oxalic acid and other dicarboxylic acids. This system of replicating clays and their metabolic phenotype then evolved into the sulfide rich region of the hot spring acquiring the ability to fix nitrogen. Finally phosphate was incorporated into the evolving system which allowed the synthesis of nucleotides and phospholipids."
Once the columns are filled with stationary phase, the mobile phase is pumped through, not continuously but, in pulses. The solvent motion created by a pulsed pumping action creates the mixing and settling that is common to most all forms of countercurrent chromatography.
==== Site shaving ==== Before branding, the site of the brand must be shaved very closely to the skin. The site should also be shaved with at least the bottom edge as square as possible. This assists the worker when placing the brand and helps prevent it from dislodging on animals with thick coats. The excellent insulating properties of hair make a close shave critically important for achieving an even brand. Shaving permits a close interface between brand and flesh. Specialized clipper blades and heads have been designed for cryogenic branding and are made to provide as close a shave as possible. Once shaved, the area to be branded is soaked with alcohol to disinfect the animal's skin.
== Incidence == Insulinomas are rare neuroendocrine tumours with an incidence estimated at one to four new cases per million persons per year. Insulinoma is one of the most common types of tumours arising from the islets of Langerhans cells (pancreatic endocrine tumours). Estimates of malignancy (metastases) range from 5 to 30%. Over 99% of insulinomas originate in the pancreas, with rare cases from ectopic pancreatic tissue. About 5% of cases are associated with tumours of the parathyroid glands and the pituitary (multiple endocrine neoplasia type 1) and are more likely to be multiple and malignant. Most insulinomas are small, less than 2 cm.
Sources: en.wikipedia.org
Progesterone is the most important progestogen in the body. As a potent agonist of the nuclear progesterone receptor (nPR) (with an affinity of KD = 1 nM), the resulting effects on ribosomal transcription play a major role in regulation of female reproduction. In addition, progesterone is an agonist of the more recently discovered membrane progesterone receptors (mPRs), of which the expression has regulation effects in reproduction function (oocyte maturation, labor, and sperm motility) and cancer, although the roles are not yet well defined. Progesterone is also a ligand of the PGRMC1 (progesterone receptor membrane component 1) which impacts tumor progression, metabolic regulation, and viability control of nerve cells. Moreover, progesterone is also known to be an antagonist of the sigma σ1 receptor, a negative allosteric modulator of nicotinic acetylcholine receptors, and a potent antagonist of the mineralocorticoid receptor (MR). Progesterone prevents MR activation by binding to this receptor with an affinity exceeding even those of aldosterone, and glucocorticoids such as cortisol and corticosterone, and it produces antimineralocorticoid effects, such as natriuresis, at physiological concentrations. Progesterone also binds to, and behaves as a partial agonist of, the glucocorticoid receptor (GR), albeit with very low potency (EC50 >100-fold less relative to cortisol). Through its neurosteroid active metabolites, such as 5α-dihydroprogesterone and allopregnanolone, progesterone acts indirectly as a positive allosteric modulator of the GABAA receptor.
== History == The word comes from the Greek ἀφροδισιακόν, aphrodisiakon 'sexual, aphrodisiac', from aphrodisios 'pertaining to Aphrodite', the Greek goddess of love. Throughout human history, food, drinks, and behaviors have had a reputation for making sex more attainable and/or pleasurable. However, from a historical and scientific standpoint, the alleged results may have been mainly due to mere belief on the part of their users that they would be effective (a placebo effect). Likewise, many medicines are reported to affect libido in inconsistent or idiopathic ways: enhancing or diminishing overall sexual desire, depending on the circumstances. For example, bupropion (Wellbutrin) is known as an antidepressant that can counteract other co-prescribed antidepressants with libido-diminishing effects. However, because bupropion increases libido only when it is already impaired by related medications, it is not generally classed as an aphrodisiac. Ancient civilizations like Chinese, Indian, Egyptian, Roman, and Greek cultures believed that certain substances could provide the key to improving sexual desire, sexual pleasure, and/or sexual behavior. This was important because some men suffered from erectile dysfunction and could not reproduce. Men who could not impregnate their wives and father large families were seen as failures, whereas those who could were respected. Hence, a stimulant was needed. Others who did not suffer from this also desired performance enhancers.
=== Vitamins === Many observational and clinical studies have been conducted to investigate the role of vitamins on diabetic complications, In the First National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study, vitamin supplementations were associated with 24% reduction on the risk of diabetes, observed during 20 years of follow-up. Many observational studies and clinical trials have linked several vitamins with the pathological process of diabetes; these vitamins include folate, thiamine, β-carotene, and vitamin E, C, B12, and D.
== Applications == Alanine scanning was used to determine simultaneously the functional contributions of 19 side chains buried at the interface between human growth hormone and the extracellular domain of its receptor. Each amino acid in the side chains was substituted by alanine. Then shotgun scanning method which combines the concepts of alanine scanning mutagenesis and binomial mutagenesis with phage display technology was used. Another critical application of alanine scanning is to determine the influence of individual residues on structure and activity in the prototypic cyclotide kalata B1. Cyclotides display a wide range of pharmaceutically important bioactivities, but their natural function is in plant defense as insecticidal agents. On the structure of cyclotides kalata B1, all 23 non-cysteine residues were successively substituted with alanine. The data were tested by NMR Spectroscopy. In addition, alanine scanning is also used to determine which functional motif of Cry4Aa has the mosquitocidal activity. Cry4Aa was produced by Bacillus thuringiensis. It is a dipteran-specific toxin and it plays an important role in how to produce a bioinsecticide to control mosquitoes. So, it is very essential to determine which functional motif of Cry4Aa contributes to this activity. In this study, several Cry4Aa mutants were made by replacing the residues of potential receptor binding site, loops 1, 2, and 3 in domain II with alanine. A bioassay Culex pipiens was followed to test the activities.
Sources: en.wikipedia.org
It is a synthetic peptide of seven amino acids. Its backbone corresponds to a fragment of adrenocorticotropic hormone extended at the carboxyl end. The material is distributed as a lyophilized solid for laboratory use.
The extension was introduced to slow enzymatic breakdown of the peptide in biological systems. Natural ACTH fragments are degraded rapidly by peptidases. Adding the tripeptide was intended to extend the window during which the molecule remains intact.
Most published work consists of animal experiments conducted in a small number of laboratories. Human data are limited in number and size. Whether the observed effects translate into reliable clinical benefit is still unresolved.
电喷雾或基质辅助激光解吸电离质谱是常用手段，测得的质子化离子质荷比可换算为分子量。结果与理论值落在合理误差内，才支持结构一致的判断。