A practical reference on lyophilized powder: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-05-27. Anything still debated is marked as such rather than presented as settled.
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。
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。
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.
| 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 |
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。
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.
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.
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.
==== Fishkeeping ==== Hydrogen peroxide is used in aquaculture for controlling mortality caused by various microbes. In 2019, the U.S. FDA approved it for control of Saprolegniasis in all coldwater finfish and all fingerling and adult coolwater and warmwater finfish, for control of external columnaris disease in warm-water finfish, and for control of Gyrodactylus spp. in freshwater-reared salmonids. It can also be used to increase the oxygen content of water to enable fish to survive otherwise-hypoxic conditions. The hydrogen peroxide releases oxygen by decomposition when it is exposed to catalysts such as manganese dioxide. Sodium percarbonate, a complex containing hydrogen peroxide as its active agent, is sold for oxygenation in acutely oxygen-deficient water to enable fish survival.
A 2003 technical report by the World Health Organization provided evidence that high intake of sugary drinks (including fruit juice) increases the risk of obesity by adding to overall energy intake. By itself, sugar is not a factor causing obesity and metabolic syndrome, but rather its excessive consumption adds to caloric burden, which meta-analyses showed could increase the risk of developing type 2 diabetes and metabolic syndrome in adults and children.
In the salivary glands, fluid is primarily secreted into small cavities surrounded by a small clusters of 8-12 cells, called an acinus (plural: acini), and these cells are often referred to as acinar cells. In the acini of the salivary glands, the serous acinar cells secrete a watery fluid with a high concentration of proteins such as enzymes (like α-Amylase) and anti-microbial proteins (like lactoperoxidase), unlike the mucous acinar cells, which produce thicker mucus-rich fluid. After secretion, the secreted fluid passes through a series of ducts which are lined with cells that further modify its composition and eventually release the finished saliva into the mouth.
The staple commodities regularly contaminated with aflatoxins include cassava, chilies, corn, cottonseed, millet, peanuts, rice, sorghum, sunflower seeds, tree nuts, wheat, and a variety of spices intended for human or animal consumption. Aflatoxins have been isolated from all major cereal crops, and sources as diverse as peanut butter and cannabis. Aflatoxin transformation products are sometimes found in eggs, milk products, and meat when animals are fed contaminated grains. Aflatoxins are produced by both Aspergillus flavus and Aspergillus parasiticus, which are common forms of "weedy" molds widespread in nature. Aflatoxins occur also in Aspergillus pseudocaelatus, Aspergillus nomius and Aspergillus pseudonomius. The presence of these molds does not always indicate that harmful levels of aflatoxin are present, but it does indicate a significant risk. The molds can colonize and contaminate food before harvest or during storage, especially following prolonged exposure to a high-humidity environment or to stressful conditions such as drought. Aflatoxin contamination is increasing in crops such as maize as a result of climate change. The native habitat of Aspergillus is in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration, but it invades all types of organic substrates whenever conditions are favorable for its growth. Favorable conditions for production of aflatoxins include high moisture content (at least 7%) and temperatures from 55 to 104 °F (13 to 40 °C), where the optimum is 27 to 30 °C (81 to 86 °F).
Sources: en.wikipedia.org
The two premiers were brought together in person in late January 1965, when Smith travelled to London for Sir Winston Churchill's funeral. Following an episode concerning Smith's non-invitation to a luncheon at Buckingham Palace after the funeral—noticing the Rhodesian's absence, the Queen sent a royal equerry to Smith's hotel to retrieve him, reportedly causing Wilson much irritation—the two prime ministers inconclusively debated at 10 Downing Street. They differed on most matters, but agreed on a visit to Rhodesia the next month by Bottomley and the Lord Chancellor, Lord Gardiner, to gauge public opinion and meet political and commercial figures. Bottomley and Gardiner visited Rhodesia from 22 February to 3 March, collected a wide cross-section of opinions, including some from black Rhodesians, and on returning to Britain reported to the House of Commons that they were "not without hope of finding a way towards a solution that will win the support of all communities and lead to independence and prosperity for all Rhodesians". Bottomley also condemned black-on-black political violence, and dismissed the idea of introducing majority rule through military force. The RF called a new general election for May 1965 and, campaigning on an election promise of independence, won all 50 "A"-roll seats (the voters for which were mostly white). Josiah Gondo, leader of the United People's Party, became Rhodesia's first black Leader of the Opposition.
== Pollution tolerance == Xanthoria parietina is highly resistant to air pollution, including heavy metals, nitrogen compounds, and ozone. Laboratory experiments have shown that it tolerates exposure to air contaminants and bisulfite ions with little or no damage. It is also resistant to heavy metal contamination and nitrogen pollution. The mechanisms underlying this tolerance involve multiple protective systems. The parietin layer in the upper cortex acts as a hydrophobic barrier, reducing the penetration of toxic metal ions into the photobiont cells. Experimental studies have shown that parietin-deficient thalli experience greater physiological stress when exposed to heavy metals. Parietin also contributes to ozone tolerance; fumigation experiments revealed that samples containing parietin recovered photosynthetic efficiency and chlorophyll integrity more quickly than those without it, suggesting an antioxidant function in addition to its role as a light-screening pigment. Furthermore, reactive oxygen species (ROS) levels induced by ozone exposure were significantly higher in parietin-deficient samples, reinforcing its role in oxidative stress mitigation. The hydration state of X. parietina influences its ozone sensitivity. Dry thalli suffer less damage and recover more quickly than hydrated ones, likely because reduced gas exchange limits ozone penetration. This factor helps explain the lichen's resilience in Mediterranean climates, where it often remains desiccated during periods of high ozone pollution.
Gregory L. Verdine (born June 10, 1959) is an American chemical biologist, biotech entrepreneur, venture capitalist and university professor. He is a founder of the field of chemical biology, which deals with the application of chemical techniques to biological systems. His work has focused on mechanisms of DNA repair and cell penetrability. Verdine is the co-inventor with Christian Schafmeister of stapled peptides, a new class of drugs that combines the versatile binding properties of monoclonal antibodies with the cell-penetrating ability of small molecules. Verdine coined the term "drugging the undruggable" to describe the unique capabilities of stapled peptides. A close analog of a stapled peptide drug invented in the Verdine Lab, sulanemadlin (ALRN-6924), is a first-in-class dual MDM2/MDMX inhibitor currently in Phase II clinical development by Aileron Therapeutics, which he co-founded in 2005. FogPharma, founded in 2016, aims to further develop stapled peptide technology for therapeutic use. He has founded numerous other drug discovery companies, including six that are listed on the NASDAQ. His companies have succeeded in developing two FDA-approved drugs, romidepsin and paritaprevir, which are, respectively, an anticancer agent used in cutaneous T-cell lymphoma (CTCL) and other peripheral T-cell lymphomas (PTCLs), and an acylsulfonamide inhibitor that is used to treat chronic hepatitis C.
Sources: en.wikipedia.org
=== Development from research tools === The industrialisation of molecular biology assay tools has made it practical to use them in clinics. Miniaturisation into a single handheld device can bring medical diagnostics into the clinic and into the office or home. The clinical laboratory requires high standards of reliability; diagnostics may require accreditation or fall under medical device regulations. As of 2011, some US clinical laboratories nevertheless used assays sold for "research use only". Laboratory processes need to adhere to regulations, such as the Clinical Laboratory Improvement Amendments, Health Insurance Portability and Accountability Act, Good Laboratory Practice, and Food and Drug Administration specifications in the United States. Laboratory Information Management Systems help by tracking these processes. Regulation applies to both staff and supplies. As of 2012, twelve US states require molecular pathologists to be licensed; several boards such as the American Board of Medical Genetics and the American Board of Pathology certify technologists, supervisors, and laboratory directors. Automation and sample barcoding maximise throughput and reduce the possibility of error or contamination during manual handling and results reporting. Single devices to do the assay from beginning to end are now available.
Di-tert-butyl dicarbonate is a reagent widely used in organic synthesis. Since this compound can be regarded formally as the acid anhydride derived from a tert-butoxycarbonyl (Boc) group, it is commonly referred to as Boc anhydride. This pyrocarbonate reacts with amines to give N-tert-butoxycarbonyl or so-called Boc derivatives. These carbamate derivatives do not behave as amines, which allows certain subsequent transformations to occur that would be incompatible with the amine functional group. The Boc group can later be removed from the amine using moderately strong acids (e.g., trifluoroacetic acid). Thus, Boc serves as a protective group, for instance in solid phase peptide synthesis. Boc-protected amines are unreactive to most bases and nucleophiles, allowing for the use of the fluorenylmethyloxycarbonyl group (Fmoc) as an orthogonal protecting group.
== Signs and symptoms == Atherosclerosis is typically asymptomatic for decades because the arteries enlarge at all plaque locations; thus, there is no effect on blood flow. Even most plaque ruptures do not produce symptoms until enough narrowing or closure of an artery, due to clots, occurs. Signs and symptoms only happen after severe narrowing or closure impedes blood flow to different organs enough to induce symptoms. Most of the time, patients realize that they have the disease only when they experience other cardiovascular disorders such as stroke or heart attack. These symptoms, however, still vary depending on which artery or organ is affected. Early atherosclerotic processes likely begin in childhood. Fibrous and gelatinous lesions have been observed in the coronary arteries of children. Fatty streaks have been observed in the coronary arteries of juveniles. While coronary artery disease is more prevalent in men than women, atherosclerosis of the cerebral arteries and strokes equally affect both sexes. Marked narrowing in the coronary arteries, which are responsible for bringing oxygenated blood to the heart, can produce symptoms such as chest pain of angina and shortness of breath, sweating, nausea, dizziness or lightheadedness, breathlessness or palpitations. Abnormal heart rhythms called arrhythmias—the heart beating either too slowly or too quickly—are another consequence of ischemia. Carotid arteries supply blood to the brain and neck.
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。
It is registered as a pharmaceutical product in Russia, where it is typically supplied as a nasal solution. In most other countries it is not an approved drug and is traded as a research chemical instead. Approval status depends entirely on the jurisdiction involved.