Methionine oxidation raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-11-17 and is reviewed periodically as new material appears.
Routine characterization relies on reversed-phase high-performance liquid chromatography to establish purity and on mass spectrometry to confirm molecular identity. Electrospray ionization and matrix-assisted laser desorption ionization are both used for mass verification. Amino acid analysis and peptide mapping can detect sequence errors. Common impurities include truncated sequences, methionine sulfoxide formed by oxidation, and deamidated products. Chromatograms are usually recorded near 214 nm, where the peptide backbone absorbs, and purity is reported as the percentage area of the principal peak.
Verification of a supplied batch generally combines a certificate of analysis with independent testing, because certificates are self-reported documents. A typical package includes a chromatographic trace, a mass spectrum, and a stated water or counter-ion content. Batch-to-batch consistency matters more than a single purity figure when results are compared across experiments. No single mandatory standard governs research-grade peptide release, so laboratories are expected to define their own acceptance criteria. Residual trifluoroacetate from purification is a frequently overlooked counter-ion.
Lyophilized material is chemically stable for extended periods when kept dry, cold, and protected from light. The powder is hygroscopic, so vials should be warmed to room temperature before opening to reduce condensation on the contents. Once dissolved, the peptide is far less stable because peptide bonds are susceptible to hydrolysis and the methionine residue can oxidize. Solutions are typically aliquoted and held at 2-8 °C for short intervals or frozen for longer ones, and repeated freeze-thaw cycles should be avoided.
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.
| Property | Value | Notes |
|---|---|---|
| Typical purity | 95% or higher | By reversed-phase HPLC area |
| Identity method | Electrospray mass spectrometry | Confirms molecular mass |
| Purity method | Reversed-phase HPLC | Detection near 214 nm |
| Primary degradation | Methionine oxidation | Sulfoxide product, +16 Da |
| Solution storage | 2-8 °C, short term | Aliquot to avoid freeze-thaw |
Practical handling follows from those properties. Bulk material is best divided into single-use portions soon after receipt, because each thaw exposes the whole container to moisture and temperature cycling. Vials should be allowed to reach room temperature before opening to prevent condensation on the powder. Low-binding plasticware reduces loss of dilute solutions, and sterile filtration is used when a preparation must remain free of microbial growth. Records of batch number, reconstitution date and storage history are what allow a later analytical result to be interpreted meaningfully.
Identity and purity of Semax are established mainly by reversed-phase high-performance liquid chromatography coupled with mass spectrometry. The chromatographic trace gives a purity estimate as a percentage of total peak area, while electrospray or matrix-assisted laser desorption ionization confirms the molecular mass against the calculated value. Amino acid analysis and sequence-specific fragmentation provide further confirmation when a supplier's chain of custody is unclear. Vendors frequently quote a purity figure without stating the detection wavelength or the integration method, which limits how far one number can be compared with another.
Development is attributed to researchers at the Institute of Molecular Genetics in Moscow during the early 1980s, building on earlier Soviet work with ACTH fragments. Russian regulatory approval followed for intranasal use, and the compound has remained commercially available there for decades. Most published human data originate from Russian and, later, some Eastern European clinical reports, which are not always accessible in English translation. Outside that region the material is generally handled as a research chemical rather than a licensed medicine.
Regulatory status differs sharply between jurisdictions. In Russia the peptide is registered as a prescription nasal preparation, while agencies such as the United States Food and Drug Administration have not approved it for any indication. Products sold elsewhere are typically labeled for laboratory research only, and such labels shift responsibility for safe handling to the purchaser. Because the same name covers pharmaceutical-grade nasal drops and bulk research powder, identity and purity documentation becomes the main practical concern when comparing sources.
Semax is a synthetic seven-amino-acid peptide whose sequence extends the ACTH(4-10) fragment with a C-terminal proline-glycine-proline tripeptide. The commonly cited sequence is Met-Glu-His-Phe-Pro-Gly-Pro, giving a molecular formula near C37H51N9O10S and a molecular weight close to 813.9 g/mol. It belongs to the broader class of synthetic ACTH fragments studied for central nervous system effects rather than for adrenal steroid stimulation. In practice the material appears as a lyophilized white powder for laboratory work or as a dilute saline solution in clinical settings.
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。
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。
== External links == [1]: A MATLAB routine to solve the linear elastic contact mechanics problem entitled; "An LCP solution of the linear elastic contact mechanics problem" is provided at the file exchange at MATLAB Central. [2]: Contact mechanics calculator. [3]: detailed calculations and formulae of JKR theory for two spheres. [5]: A Matlab code for Hertz contact analysis (includes line, point and elliptical cases). [6]: JKR, MD, and DMT models of adhesion (Matlab routines).
Dill (Anethum graveolens) is an annual herb in the celery family Apiaceae. Native to North Africa and West Asia, dill is grown widely in Eurasia, where its leaves and seeds are used as a herb or spice for flavouring food.
== Products == In Germany and Austria, spelt loaves and rolls (Dinkelbrot) are widely available in bakeries. The unripe spelt grains are dried and eaten as Grünkern ("green grain"). In Australia it is grown organically for the health food market. Dutch jenever makers sometimes distil with spelt, while beer brewed from spelt exists in Bavaria and Belgium.
Arbitration by consent, s 240. Workplace determinations, s 275 50% vote to approve by staff after final offer of employer, s 182 Process to approve an agreement, ss 180–186 Agreements approved by FWC, not below NES and pass BOOT, s 55 BOOT, each employee must be better off than in an awards 193 Variation by same process as making: ss 207–224 FWC can approve termination if in public interest, s 225 - back to award unless terms incorporated - or if out of date, it limits productivity, etc.
Star anise is the major source of the chemical compound shikimic acid, a primary precursor in the pharmaceutical synthesis of the anti-influenza drug oseltamivir (Tamiflu). An industrial method for the production of shikimic acid using fermentation of E. coli bacteria was discovered in 2005, and applied in the 2009 swine flu pandemic to address Tamiflu shortages, eventually reversing price increases for star anise as a raw material of shikimic acid. As of 2018, fermentation of E. coli was the manufacturing process of choice to produce shikimic acid for synthesis of Tamiflu.
Sources: en.wikipedia.org
James Bertram Collip (November 20, 1892 – June 19, 1965) was a Canadian biochemist who was part of the Toronto group which isolated insulin. He served as the chair of the department of biochemistry at McGill University from 1928 to 1941 and dean of medicine at the University of Western Ontario from 1947 to 1961, where he was a charter member of The Kappa Alpha Society.
Akt resides in the cytosol in an inactive conformation, until the cell is stimulated and it translocates to the plasma membrane. The Akt PH domain has a high affinity for second messenger PI(3,4,5)P3, binding to it preferentially over other phosphoinositides. Thus PI3K activity is essential for translocation of Akt to the membrane. Interaction with PI(3,4,5)P3 causes conformational changes and exposure of phosphorylation sites Thr308 in the kinase domain and Ser473 in the C-terminal domain. Akt is partially activated by phosphorylation of T308 by PDK1. Full activation requires phosphorylation of S473, which can be catalysed by multiple proteins, including phosphoinositide-dependent kinase 2 (PDK2), integrin-linked kinase (ILK), mechanistic target of rapamycin complex complex 2 (mTORC2) and DNA-dependent protein kinase (DNA-PK). The regulation of Ser473 phosphorylation is not fully understood but may also be influenced by autophosphorylation after Thr308 phosphorylation. After stimulation, the levels of PIP3 decrease and Akt activity is attenuated by dephosphorylation by serine/threonine phosphatases.
Almost two-thirds of the world's supply comes from two reactors; the National Research Universal Reactor at Chalk River Laboratories in Ontario, Canada, and the High Flux Reactor at Nuclear Research and Consultancy Group in Petten, Netherlands. All major reactors that produce technetium-99m were built in the 1960s and are close to the end of life. The two new Canadian Multipurpose Applied Physics Lattice Experiment reactors planned and built to produce 200% of the demand of technetium-99m relieved all other producers from building their own reactors. With the cancellation of the already tested reactors in 2008, the future supply of technetium-99m became problematic.
== Use as chemical weapon == 3-Methylfentanyl was also reported by media as the identity of the anaesthetic "gas" Kolokol-1 delivered as an aerosol during the Moscow theater hostage crisis in 2002 in which many hostages died from accidental overdoses, 3-methylfentanyl was later ruled out as the primary agent used. The opiate antidote naloxone was on-hand to treat the victims of the crisis, but, whether due to their incarceration, lack of food, or water, or sleep, or due to the novel nature of the still-unconfirmed compound used, acute symptoms continued to develop, resulting in many fatalities despite the administration of naloxone.
== American Red Cross Blood Bank == Drew's work led to his appointment as director of the first American Red Cross Blood Bank in February 1941. He also invented what would be later known as bloodmobiles, mobile donation stations that could collect the blood and refrigerate it; this allowed for greater mobility in terms of transportation and increased prospective donations. The blood bank supplied blood to the U.S. Army and Navy, who initially rejected the blood of African-Americans and later accepted it only if it were stored separately from that of white people. Drew objected to the exclusion of African-Americans' blood from plasma-supply networks, and in 1942 he resigned in protest.
Sources: en.wikipedia.org
Organoerbium compounds are very similar to those of the other lanthanides, as they all share an inability to undergo π backbonding. They are thus mostly restricted to the mostly ionic cyclopentadienides (isostructural with those of lanthanum) and the σ-bonded simple alkyls and aryls, some of which may be polymeric.
==== Somatic and metabolic consequences ==== Like adults, OSA in children is linked to a higher risk for cardiovascular diseases, due to increased sympathetic activity and impaired cardiac autonomic control. Amongst the cardiovascular dysfunctions resulting from OSA, we can find systemic hypertension and blood pressure dysregulation (elevated blood pressure, or variability of the blood pressure for example). The variability of the blood pressure is correlated with the severity of the symptoms such as the frequency of the apnea and hypopnea. Pulmonary hypertension is also common amongst the cardiovascular problems resulting from OSA. Children with obstructive sleep-disordered breathing also show a faster heart rate during wakefulness and during sleep. In adult patients, OSA is associated with insulin resistance. In children, metabolic consequences of OSA are complicated to assess as they can also be associated to puberty and obesity (if present). However, when OSA is associated with obesity, the interaction of the two conditions can lead to metabolic disturbances such as insulin resistance and altered lipidemia, liver disease, abdominal adiposity and metabolic syndrome. Obesity interacts with those effects.
==== Drug delivery ==== Block copolymers are a well-studied and versatile class of self-assembling materials characterized by chemically distinct polymer blocks that are covalently bonded. This molecular architecture of the covalent bond enhancement is what causes block copolymers to spontaneously form nanoscale patterns. In block copolymers, covalent bonds frustrate the natural tendency of each individual polymer to remain separate (in general, different polymers, do not like to mix), so the material assembles into a nano-pattern instead. These copolymers offer the ability to self-assemble into uniform, nanosized micelles and accumulate in tumors via the enhanced permeability and retention effect. Polymer composition can be chosen to control the micelle size and compatibility with the drug of choice. The challenges of this application are the difficulty of reproducing or controlling the size of self-assembly nano micelle, preparing predictable size-distribution, and the stability of the micelle with high drug load content.
== Structure == Depending on the type of fatty acid attached to the protein, a proteolipid can often contain myristoyl, palmitoyl, or prenyl groups. These groups each serve different functions and have different preferences as to which amino acid residue they attach to. The processes are respectively named myristoylation (usually at N-terminal Gly), palmitoylation (to cysteine), and prenylation (also to cysteine). Despite the seemingly specific names, N-myristoylation and S-palmitoylation can also involve some other fatty acids, most commonly in plants and viral proteolipids. The article on lipid-anchored proteins has more information on these canonical classes. Lipidated peptides are a type of peptide amphiphile that incorporate one or more alkyl/lipid chains, attached to a peptide head group. As with peptide amphiphiles, they self-assemble depending on the hydrophilic/hydrophobic balance, as well interactions between the peptide units, which is dependent on the charge of the amino acid residues. Lipidated peptides combine the structural features of amphiphilic surfactants with the functions of bioactive peptides, and they are known to assemble into a variety of nanostructures.
Sources: en.wikipedia.org
Dry powder is normally held at -20 °C or lower, away from light and moisture. Sealed vials can also be kept at 2-8 °C for shorter intervals. Warming to room temperature before opening prevents condensation.
In solution, hydrolysis of peptide bonds and oxidation of the methionine residue are the principal concerns. Oxidation converts methionine to its sulfoxide form, shifting the mass by sixteen daltons. Both processes are slowed by cold storage and by avoiding alkaline conditions.
A certificate documents what the supplier measured on a specific lot, not how a laboratory will use the material. Independent verification of identity and purity is common practice. Acceptance criteria should be defined before a batch is ordered.
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.