The short version of lyophilized powder fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-11-28 and is reviewed periodically as new material appears.
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。
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.
Identity and purity of semax are established with reversed-phase high-performance liquid chromatography coupled to ultraviolet detection, usually at 214 nanometres. Mass spectrometry, most often electrospray ionisation in positive mode, confirms the molecular mass and reveals truncated sequences. Amino acid analysis and peptide mapping after enzymatic digestion provide additional structural confirmation. Laboratories typically report purity as the percentage area of the main peak, a figure that does not capture isomeric or oxidised variants unless the method resolves them.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C37H51N9O10S | 游离碱形式 |
| 等电点 | 约 6.5 | 估算值，随缓冲体系变化 |
| 主要降解途径 | 水解与氧化 | 侧链氧化最为常见 |
| 溶液储存 | 2 至 8 摄氏度避光 | 避免反复冻融 |
| 常规分析手段 | 反相色谱与质谱联用 | 氨基酸分析辅助核对 |
Semax is supplied as a lyophilized powder that appears white to off-white. It dissolves readily in water, phosphate-buffered saline, and other aqueous media, which simplifies preparation of working solutions for laboratory use. The nasal products registered in Russia are dilute aqueous solutions, typically around 0.1 percent peptide by weight. Organic solvents are rarely necessary and can complicate handling. Because the peptide is hygroscopic, weighing should be performed quickly and with minimal exposure to ambient humidity.
Solid material is normally kept at minus 20 degrees Celsius in a sealed, desiccated container. Reconstituted solutions are less stable and are usually divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and loss of activity. Light exposure is minimized by using amber glassware or foil wrapping. Published stability data for this peptide are sparse, so recommended storage conditions rest mainly on general practice for short synthetic peptides rather than on dedicated study.
Identity and purity are commonly assessed by reversed-phase high-performance liquid chromatography, with ultraviolet detection near 214 nanometers for the peptide backbone. Mass spectrometry, either electrospray or matrix-assisted laser desorption, confirms molecular mass and detects truncation or modification products. Amino acid analysis can verify composition. Because the sequence contains no strongly absorbing aromatic residue apart from phenylalanine, detection wavelengths are chosen carefully. Purity values above 95 percent are typical for research-grade material.
Solid semax is typically supplied as a lyophilised powder that is hygroscopic and sensitive to moisture, light, and repeated temperature cycling. Long-term storage of the dry peptide is generally recommended at approximately -20 degrees Celsius, while shorter working periods may use refrigeration at 2 to 8 degrees Celsius. Vials should remain tightly closed and desiccated when brought to room temperature, because condensation can damage the material before it is weighed. Dividing a batch into aliquots is preferable to thawing one container repeatedly.
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.
Semax is normally supplied as a lyophilized powder, and that form is the most stable. Suppliers commonly recommend storage at -20 °C in a desiccated container protected from light, with short-term handling at room temperature limited to weighing and transfer. Powder that has absorbed moisture degrades faster, so vials should be warmed to ambient temperature before opening to prevent condensation on the contents. Hygroscopic behavior is typical of short hydrophilic peptides, and humidity control matters more than temperature alone for long-term retention.
Once dissolved, the peptide is considerably less stable than the solid. Aqueous solutions are usually prepared at neutral to slightly acidic pH, filtered, and divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are a common cause of avoidable loss and are best prevented by never refreezing a thawed aliquot. Adsorption to plastic and glass surfaces can lower the measured concentration of dilute solutions, particularly below roughly 0.1 mg/mL. Buffer choice, salt content, and container material all influence how much peptide remains detectable after storage.
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.
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.
Temperatures in the tank were off the scale beyond 25 °C (77 °F), and the pressure in the tank was indicated at 280 kilopascals (40 psi). One employee witnessed a concrete slab above tank E610 crack as the emergency relief valve burst open, and pressure in the tank continued to increase to 380 kilopascals (55 psi), despite atmospheric venting of toxic MIC gas having begun. Direct atmospheric venting should have been prevented or at least partially mitigated by at least three safety devices which were malfunctioning, not in use, insufficiently sized, or otherwise rendered inoperable:
Drug development is the process of bringing a new pharmaceutical drug to the market once a lead compound has been identified through the process of drug discovery. It includes preclinical research on microorganisms and animals, filing for regulatory status, such as via the United States Food and Drug Administration for an investigational new drug to initiate clinical trials on humans, and may include the step of obtaining regulatory approval with a new drug application to market the drug. The entire process—from concept through preclinical testing in the laboratory to clinical trial development, including Phase I–III trials—to approved vaccine or drug typically takes more than a decade.
A vast array of pharmaceuticals and agrochemicals are based on pyrimidines, such as Vitamin B1 (thiamine), the sulfonamide antibiotics, e.g. Madribon (sulfadimethoxime) and – half a century later – the sulfonyl urea herbicides, e.g. Eagle (amidosulfuron) and Londax (bensulfuron-methyl). Benzodiazepine derivatives are the pivotal structural elements of breakthrough CNS drugs, such as Librium (chlordiazepoxide) and Valium (diazepam). Pyridine derivatives are found in both well-known Diquat and Chlorpyrifos herbicides, and in modern nicotinoid insecticides, such as Imidacloprid. Even modern pigments, such as diphenylpyrazolopyrazoles and quinacridones, and engineering plastics, such as polybenzimidazoles, polyimides, and triazine resins, exhibit an N-heterocyclic structure.
Dihydrocodeine, sold under the brand name Dicodin among others, is a semi-synthetic opioid analgesic prescribed for pain or severe dyspnea, or as an antitussive, either alone or compounded with paracetamol (acetaminophen) (as in co-dydramol) or aspirin. It was developed in Germany in 1908 and first marketed in 1911. Commonly available as tablets, solutions, elixirs, and other oral forms, dihydrocodeine is also available in some countries as an injectable solution for deep subcutaneous and intra-muscular administration. As with codeine, intravenous administration should be avoided, as it could result in anaphylaxis and life-threatening pulmonary edema. In the past, dihydrocodeine suppositories were used. Dihydrocodeine is available in suppository form on prescription. Dihydrocodeine is used as an alternative to codeine and similarly belongs to step 2 of the WHO analgesic ladder. It was first described in 1911 and approved for medical use in 1948. Dihydrocodeine was developed during the search for more effective cough medication, especially to help reduce the spread of tuberculosis, pertussis, and pneumonia in the years from c.a. 1895 to 1915. It is similar in chemical structure to codeine.
Sources: en.wikipedia.org
langsonensis from the Eocene strata from the Na Duong coal mine (Vietnam), and emend the diagnoses of the studied species. Scribano et al. (2026) compare the postcranial anatomy of Libycosaurus bahri and Hexaprotodon garyam from the Miocene strata from Toros-Menalla (Chad), and establish an anatomical framework for the identification of postcranial remains of anthracotheres and hippopotamids. A study on tooth anomalies in specimens of Hippopotamus cf. gorgops from the Olduvai Gorge (Tanzania), interpreted as consistent with traumatic displacement likely linked to aggressive interactions and with reactions to seasonal environmental fluctuations, is published by Fidalgo et al. (2026). Martino et al. (2026) study the cranial phenotypic diversity of hippopotamid material from Ortona (Italy) and related specimens from the Pleistocene of Central and Western Europe, identifying two morphotypes of Hippopotamus antiquus and reporting evidence of significant sexual dimorphism in mandibles of specimens from Maglianella (Italy). Marra (2026) studies morphological variation of Pleistocene hippopotamids from Sicily and Malta, and finds no evidence of presence of additional hippopotamid taxa besides Hippopotamus pentlandi in Sicily. Radović et al. (2026) identify fossil material of a hippopotamus or a related taxon from the Grebci karst area (Bosnia and Herzegovina), representing the first confirmed finding of a member of the genus Hippopotamus in southeastern Europe outside Greece.
Headgear called a "scrum cap" in rugby, or simply "headgear" or ear guard in wrestling and other martial arts, that protects the ears is worn to help prevent this condition. A specialty ear splint can also be made to keep the ear compressed, so that the damaged ear is unable to fill thus preventing cauliflower ear. For some athletes, however, a cauliflower ear is considered a badge of courage or experience.
=== Biological antifreezes === Antifreeze proteins refer to chemical compounds produced by certain animals, plants, and other organisms that prevent the formation of ice. In this way, these compounds allow their host organism to operate at temperatures well below the freezing point of water. Antifreeze proteins bind to small ice crystals to inhibit growth and recrystallization of ice that would otherwise be fatal. Cryoprotectants are commonly used in cryobiology to prevent or inhibit freezing in sperm, blood, stem cells, plant seeds, etc. Ethylene glycol, propylene glycol, and glycerol (all used in automotive antifreeze) are commonly used as biological cryoprotectants.
Sources: en.wikipedia.org
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。
甲硫氨酸侧链含硫醚，在氧气、光照或金属离子存在时容易被氧化。氧化产物极性略增，常在色谱图上表现为主峰之前的肩峰或前伸峰。
通常建议冷藏避光，并在较短时间内使用。不存在适用于所有配方的统一期限，具体取决于浓度、缓冲体系与容器材质。
Reversed-phase high-performance liquid chromatography is the standard method, with detection in the ultraviolet range. Peak area percentage yields a purity figure for the main component. Mass spectrometry is normally run alongside to confirm molecular identity.