The short version of methionine sulfoxide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-11. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical analytical method | Reversed-phase HPLC with UV detection | Separates target peptide from truncated and oxidised forms |
| Identity confirmation | LC-MS or ESI-MS | Compares observed and calculated molecular ion |
| Primary degradation route | Methionine oxidation | Forms the sulfoxide; monitored as an early-eluting peak |
| Short-term storage | 2 to 8 degrees Celsius | Applies to working vials and reconstituted portions |
| Common synonyms | ACTH(4–10) analogue, MEHFPGP | Descriptive names used in laboratory catalogues |
多数实验室与市售的 Semax 以冻干粉形式提供。冻干粉通常建议保存在 -20 °C 或更低温度下，同时避免光照与反复升温。短期运输有时采用冷藏条件，但长期保存仍以冷冻为主。分包操作应尽量减少开盖次数，以降低吸湿和微生物污染的风险。开封后若未一次用完，建议在干燥环境中密封并尽快放回低温储存。
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。
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.
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。
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.
=== Linkage isomerization === Linkage isomerism occurs with ligands with more than one donor atom, known as ambidentate ligands. For example, nitrite can coordinate through O or N. One pair of nitrite linkage isomers have structures (NH3)5CoNO2+2 (nitro isomer) and (NH3)5CoONO2+ (nitrito isomer).
Kyle K. Biggar (born 1986) is a Canadian biochemist and molecular biologist. He has been a professor of biochemistry, chemistry, and biology at Carleton University in Ottawa, Canada since 2017. Biggar was the 2016 recipient of the John Charles Polanyi Prize for his outstanding work in early career research.
==== Elimination ==== Muscimol is excreted by the kidneys into urine. It is excreted partially unmetabolized. This has been taken advantage of by Siberian practitioners of the traditional entheogenic use of Amanita muscaria via recycling of muscimol in urine. The elimination half-life of muscimol in humans is unknown. The closely related drug gaboxadol (THIP), which is a cyclized derivative of muscimol, has an elimination half-life in humans of 1.5 to 2 hours. In rodents, the half-life of gaboxadol was about twice as long as that of muscimol. Gaboxadol is said to be more resistant to metabolism than muscimol, for instance not being a substrate for GABA-T. Despite the preceding findings however, gaboxadol is shorter-lasting in its effects than muscimol in rats, with durations of up to 3 hours and more than 5 hours, respectively.
=== 5 March === Two Ukrainian pilots were in the United States to see how long it would take them to learn how to fly attack aircraft including the F-16. Another 10 pilots had been approved for similar testing in the United States but were yet to arrive.
Sources: en.wikipedia.org
=== Solution === Many growers resorted to their own methods in attempt to resolve the issue. Chemicals and pesticides were used to no avail. In desperation, some growers positioned toads under each vine, and others allowed their poultry to roam free in the hope they would eat the insects. None of these methods were successful. After Charles Valentine Riley, Missouri's state entomologist, confirmed Planchon's theory, Leo Laliman and Gaston Bazille, two French wine growers, both suggested the possibility that if vinifera vines could be combined, by means of grafting, with the aphid-resistant American vines, then the problem might be solved. Thomas Volney Munson was consulted and provided native Texan rootstocks for grafting. Because of Munson's role, the French government in 1888 sent a delegation to Denison, Texas, to confer on him the French Legion of Honor Chevalier du Mérite Agricole. Another viticulturist, Hermann Jaeger of Neosho, Missouri, was pivotal in the rescue of the French vineyards, as well. Jaeger working with the Missouri state entomologist George Hussman, had already raised vines with resistance to the pest. Indeed, several of the rootstalk varietals T.V. Munson had developed in Texas (Mrs Munson, Muench, and Neva Munson) were grafts with the hardy Neosho hybrids Jaeger had developed in Missouri. Jaeger exported 17 boxcars of his resistant rootstock to France.
A small number of cities, towns, and intentional communities around the world are exclusively vegetarian where no meat is sold or consumed due to religious and cultural influences. In all-vegetarian locations, meat and sometimes other animal products are sometimes officially outlawed. In other exclusively vegetarian cities, meat is not sold or served due to cultural influences but is not officially outlawed. Some religious centers in India have banned all meat sales within municipal boundaries. For example, in 1956, Rishikesh banned the sale of meat, fish, and eggs. Locations where residents are vegetarian and only vegetarian food is consumed within city limits include:
Resistance has in fact appeared and may be growing. But it is remarkable that despite the sharp shifts in the distribution of power, the other great powers have not yet responded in a way anticipated by balance-of-power theory.
Sources: en.wikipedia.org
Cl−indicators can be designed on the basis of endogenously expressed fluorescent proteins such as Yellow fluorescent protein (YFP). An advantage of endogenously expressed probes over dye-based probes is their ability to achieve cell-type-specificity by the choice of Promoter (genetics) promotor. YFP based indicators are mutated forms of Green fluorescent protein (GFP). YFP contains four point mutations and has a red-shifted excitation and emission spectrum compared with GFP. YFP fluorescence is sensitive to various small anions with relative potencies iodine > nitrate > chloride > bromide > formate > acetate. YFP sensitivity to these small anions results from ground-state binding near the chromophore, which apparently alters the chromophore ionization constant and hence the fluorescence emission. The fluorescence of YFP is sensitive to [Cl− ] and pH. The effect is fully reversible. YFP is excited at visible range and is a genetically encoded probe. YFP based Cl− sensors have rather low kinetics of Cl− association / dissociation. The half time association/dissociation constants for YFP mutant range from 50 ms (YFP-H148Q I152L) to 2 sec (YFP-H148Q V163S). If a fluorescent indicators is based on one fluorescent protein only, it doesn't allow for ratiometric measurements. Hence, a rationale for ratiometric fluorescent indicators results.
Another form of bioprinting involves an inkjet printer, which is primarily used in biomedical settings. This method prints detailed proteins and nucleic acids. Hydrogels are commonly selected as the bioink. Cells can be printed on to a selected surface media to proliferate and ultimately differentiate. A drawback of this printing method is the ability of the bioinks such as hydrogels to clog the printing nozzle, due to their high viscosity. Ideal inkjet bioprinting involves using a low polymer viscosity (ideally below 10 centipoise), low cell density (<10 million cells/mL), and low structural heights (<10 million cells/mL).
Romanowsky was the first to realise the differences in the staining abilities of eosin and methylene blue. The individual stains (monochromatic staining) were good only for general colouring of tissue or cell, but not for contrasting the different components. By mixing specific amount of eosin and methylene blue, Romanowsky found that the mixture gave images of contrasting clarity that helped to visualise different parts and components of cells. This mixture method, polychromatic staining or polychromy, with various modifications became the most efficient way of staining cells for identifying cellular components. The chemical phenomenon by which a mixture of stains produces vibrant cell images is known as "Romanowsky effect". In December 1890, Romanowsky published his invention as a preliminary report of his major work for his doctoral thesis in the journal Vrach as "On the question of the structure of malaria parasites" (as translated in English). Incorrectly, it is more often recorded in books and journals that Romanowsky published his findings in 1891, which led to a controversy on priority that Ernst Malachowsky independently developed the technique as the latter published his research in August 1891.
Sources: en.wikipedia.org
Dry powder is usually kept at about -20 degrees Celsius for long-term storage and at 2 to 8 degrees Celsius for short working periods. Containers should stay sealed and protected from light and moisture to limit degradation.
Oxidation of the methionine residue to the sulfoxide is a frequently reported change, and it usually appears as an earlier-eluting peak in reversed-phase chromatography. Backbone hydrolysis products can also accumulate in aqueous solution.
Liquid chromatography coupled with mass spectrometry is the usual approach, because the observed molecular ion can be compared with a calculated mass of about 813.9 Da. Retention time alone does not establish identity.
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.