peptide synthesis comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-06-11. Numbers and descriptions here follow the published literature rather than marketing material.
该化合物于二十世纪八十年代在俄罗斯被开发，相关工作由俄罗斯科学院分子遗传学研究所的研究团队主导。开发目标并非复制 ACTH 的完整激素活性，而是寻找保留其神经作用方向、同时去除促肾上腺皮质激素释放效应的短肽片段。研究记录显示，这一方向促成了多个相关短肽的合成与筛选，而 Semax 是其中被研究最广泛的一个。当地文献常以 Семакс 这一名称指代它。
研究兴趣主要集中在神经营养因子相关的路径上，包括脑源性神经营养因子与神经生长因子的表达变化。部分实验报告称在特定条件下观察到这些因子的水平上升，但具体信号通路和剂量依赖关系仍未完全厘清。多数公开数据来自细胞模型和动物实验，人体对照研究数量有限。因此，该化合物的作用机制在文献中属于活跃讨论，而非已经确立的定论。
Semax 是一种人工合成的七肽，氨基酸序列为 Met-Glu-His-Phe-Pro-Gly-Pro，单字母缩写记作 MEHFPGP。它被归类为促肾上腺皮质激素片段 ACTH(4-10) 的结构类似物，但并不天然存在于生物体内。母体片段 ACTH(4-10) 的序列为 Met-Glu-His-Phe-Arg-Trp-Gly，Semax 替换了中间两个残基，并在羧基端延长了 Pro-Gly-Pro 三肽。这种延长被普遍认为能提升分子对肽酶的耐受性。
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.
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.
| Property | Value | Notes |
|---|---|---|
| 化学类别 | 合成七肽 | ACTH(4-10) 结构类似物 |
| 氨基酸序列 | Met-Glu-His-Phe-Pro-Gly-Pro | 单字母写作 MEHFPGP |
| 分子量 | 约 813.9 Da | 随确切形式和盐型略有变化 |
| 常见同义词 | ACTH(4-10) 类似物 | 俄语文献称 Семакс |
| 开发来源 | 俄罗斯 | 二十世纪八十年代 |
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.
=== Period 3: final narrative evolution === The final stage at Kizil is Period 3 of the Second Indo-Iranian Style. Towards the end of its florescence, Kizil saw the emergence of the domed central pillar cave, a type of "central pillar" structure, with niche and circumambulating corridor, but with a very uncharacteristic near-cubic main cella crowned by a magnificent cupola decorated with divinities. The style of painting is very refined, and can also be seen in some other caves in the region such as in Kumtura. The iconography too has evolved, with a cosmological Buddha becoming omnipresent and majestic, often surrounded by myriads of emanations of smaller Buddhas. This exceptional and very refined type of cave is exemplified by Cave 123, the "Cave with the Ring-Bearing Doves". It represents a final narrative evolution, in which the figures of the cosmological Buddha predominate, while secondary figures and stories take an ever-smaller role.
Astatine is the rarest naturally occurring element. The total amount of astatine in the Earth's crust (quoted mass 2.36 × 1025 grams) is estimated by some to be less than one gram at any given time. Other sources estimate the amount of ephemeral astatine, present on earth at any given moment, to be up to one ounce (about 28 grams). Any astatine present at the formation of the Earth has long since disappeared; the four naturally occurring isotopes (astatine-215, -217, -218 and -219) are instead continuously produced as a result of the decay of radioactive thorium and uranium ores, and trace quantities of neptunium-237. The landmass of North and South America combined, to a depth of 16 kilometers (10 miles), contains only about one trillion astatine-215 atoms at any given time (around 3.5 × 10−10 grams). Astatine-217 is produced via the radioactive decay of neptunium-237. Primordial remnants of the latter isotope—due to its relatively short half-life of 2.14 million years—are no longer present on Earth. However, trace amounts occur naturally as a product of transmutation reactions in uranium ores. Astatine-218 was the first astatine isotope discovered in nature. Astatine-219, with a half-life of 56 seconds, is the longest lived of the naturally occurring isotopes. Isotopes of astatine are sometimes not listed as naturally occurring because of misconceptions that there are no such isotopes, or discrepancies in the literature. Astatine-216 has been counted as a naturally occurring isotope but reports of its observation (which were described as doubtful) have not been confirmed.
Within the immune system, prolactin acts to promote lymphocyte differentiation, proliferation, and function through the activation of protein kinase C signaling pathway. Prolactin has immunomodulatory and anti-inflammatory effects within the immune system, contributing to immune system maintenance. Stress also acutely stimulates prolactin production, as dopamine (a prolactin inhibitor) levels are reduced under stress, the pituitary gland is in turn expressed more leading to higher prolactin levels.
Sources: en.wikipedia.org
GNC stores typically stock a wide range of weight loss, bodybuilding, nutritional supplements, vitamins, natural remedies, and health and beauty products, in both its owned brands as well as third-party brands. Its products are also sold on GNC.com and, as of January 2017, on GNC's Amazon Marketplace. The company offers consumer products and services via retail locations, like their own stores, franchises, online, digital commerce and wholesales and retail partnerships. They have over 17,500 employees working in their stores and sell lots of different things from over 325 brands, with more than 7,500 things available in their stores and on their website. GNC4U is a program for monthly subscription deliveries of personalized vitamins and supplements. On December 31, 2018, GNC had approximately 8,400 locations, of which approximately 6,200 were in the United States (including approximately 2,200 Rite Aid licensed store-within-a-store locations), as well as franchise operations in approximately 50 countries. Of GNC's approximately 4,100 U.S. locations in 2019, 61% were in strip malls and 28% were in larger malls. In July 2023, the company announced it would begin making deliveries in select markets via drone.
The earliest forms of cigarettes were similar to their predecessor, the cigar. Cigarettes appear to have had antecedents in Mexico and Central America around the 9th century in the form of reeds and smoking tubes. The Maya, and later the Aztecs, smoked tobacco and other psychoactive drugs in religious rituals and frequently depicted priests and deities smoking on pottery and temple engravings. The cigarette and the cigar were the most common methods of smoking in the Caribbean, Mexico, and Central and South America until recent times. The North American, Central American, and South American cigarette used various plant wrappers; when it was brought back to Spain, maize wrappers were introduced, and by the 17th century, fine paper. The resulting product was called papelate and is documented in Goya's paintings La Cometa, La Merienda en el Manzanares, and El juego de la pelota a pala (18th century). By 1830 the cigarette had become known in France, where it received the name cigarette, and in 1845 the French state tobacco monopoly began manufacturing them. The French word made its way into English in the 1840s. Some American reformers promoted the spelling cigaret, but this was never widespread and is now largely abandoned. The first patented cigarette-making machine was invented by Juan Nepomuceno Adorno of Mexico in 1847. In the 1850s, Turkish cigarette leaves became popular.
Hydrogen has the most frequently imaged nucleus in MRI because it is present in biological tissues in great abundance, and because its high gyromagnetic ratio gives a strong signal. However, any nucleus with a net nuclear spin could potentially be imaged with MRI. Such nuclei include deuterium, helium-3, lithium-7, carbon-13, fluorine-19, oxygen-17, sodium-23, phosphorus-31 and xenon-129. 2H, 23Na and 31P are naturally abundant in the body, so they can be imaged directly. Naturally abundant deuterium at the concentration of around 15mM can be imaged, but suffers from low gamma sensitivity and quadripolar Relaxation (NMR). Deuterium imaging however has a sparse chemical shift spectrum making it possible to develop tailored multiband selective RF pulses for metabolite selective imaging. Thus, metabolic imaging, similar to what's done with Carbon-13 is possible with Deuterium metabolic imaging (DMI) for insights into vivo metabolic processes. As well, the short T2 of deuterium allows it to be signal averaged rapidly, making up for some of its physical shortcomings. Gaseous isotopes such as 3He or 129Xe must be hyperpolarized and then inhaled as their nuclear density is too low to yield a useful signal under normal conditions. 17O and 19F can be administered in sufficient quantities in liquid form (e.g. 17O-water) that hyperpolarization is not a necessity. Using helium or xenon has the advantage of reduced background noise, and therefore increased contrast for the image itself, because these elements are not normally present in biological tissues.
Sources: en.wikipedia.org
不是。Semax 是完全人工合成的七肽，自然界中没有对应的已知肽段。它的设计灵感来自促肾上腺皮质激素片段 ACTH(4-10)，但序列经过了替换和延长。
Semax 被描述为 ACTH(4-10) 的结构类似物，两者共享部分序列特征。它保留了该片段的部分神经相关活性方向，但去除了完整片段带来的激素释放效应。二者并非同一物质，也不能互相替代。
加入的 Pro-Gly-Pro 三肽被普遍认为能提升分子对蛋白水解酶的稳定性。这种设计让短肽在体内维持时间更长。具体延长的程度以及不同组织中是否一致，文献中仍存在不同报告。
It is a short synthetic peptide built from seven amino acids: methionine, glutamic acid, histidine, phenylalanine and three prolines. The sequence derives from the 4-10 fragment of adrenocorticotropic hormone with an added proline-glycine-proline tail. No plant or animal extract is involved; the material is produced by solid-phase peptide synthesis.