The short version of peptidase cleavage fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-20. Anything still debated is marked as such rather than presented as settled.
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。
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。
The mechanisms attributed to semax are inferred from animal and cell studies rather than traced to one confirmed target. The most frequently cited pathway involves increased expression of brain-derived neurotrophic factor and nerve growth factor in hippocampal and cortical tissue. Some work points to engagement of melanocortin receptors, particularly MC4, which the parent ACTH fragment can activate. Effects on dopaminergic and serotonergic signalling have also been reported. No single account explains all observed results, and the relative weight of each pathway remains unsettled.
Published studies examine a fairly narrow set of endpoints. Rodent experiments commonly measure maze learning, infarct volume after induced ischemia, and tissue levels of neurotrophic factors. Clinical reports from Russian centres describe attention, memory and recovery scores in patients after stroke or transient ischemic attack. Most of those human studies are small and few have been repeated by independent groups. Outcome measures differ between studies, which limits direct comparison.
Circulation time for the peptide is short because peptidases cleave it readily. The Pro-Gly-Pro tail is thought to slow breakdown compared with the bare ACTH fragment, but the gain appears modest. Absorption after intranasal dosing is limited, and only a fraction of a dose is expected to reach the central nervous system. Laboratory concentrations therefore sit well above levels achieved systemically, a gap that complicates translation from bench findings to clinical claims.
| 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 |
The compound was developed in the 1980s at the Institute of Molecular Genetics in Moscow, where it emerged from research on short ACTH fragments and their effects on the central nervous system. Russian pharmaceutical listings describe it as a nootropic and neuroprotective agent, most often formulated as nasal drops. It is not a marketed medicine in the United States or the European Union, and no pharmacopoeial monograph covers it. Consequently, most published clinical experience with the substance originates from a small number of research centres, mainly in Russia and neighbouring countries.
Pharmacological accounts link semax to melanocortin signalling and to modulation of neurotrophic factor expression, particularly brain-derived neurotrophic factor and nerve growth factor. Much of this evidence comes from rodent studies using intranasal delivery, a route chosen because it allows peptides to reach the central nervous system with limited systemic exposure. Whether the same mechanisms operate in humans at comparable magnitude remains an open question. The precise receptor or receptors responsible for the reported behavioural and neuroprotective effects have not been conclusively identified.
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.
Identity and purity are established with standard peptide methods. Reversed-phase HPLC with ultraviolet detection near 214 nm resolves the parent peak from deletion and truncation byproducts, and reports typically quote a main-peak percentage. Mass spectrometry by electrospray or MALDI-TOF confirms the expected molecular mass, while amino acid analysis or peptide mapping can verify composition when the sequence itself is in question. A certificate of analysis that pairs a chromatogram with a mass spectrum is more informative than a purity figure alone. Counter-ion content and residual solvents are separate specifications and are frequently omitted.
On April 21, 2009, Newsom announced his candidacy for governor of California in the 2010 election. He named state senator (and future U.S. senator) Alex Padilla to chair his campaign. He received former president Bill Clinton's endorsement in September. Throughout the campaign, he had low poll numbers, trailing Democratic frontrunner Jerry Brown by more than 20 points in most polls. Newsom dropped out of the race in October and ran for lieutenant governor instead.
== External links == PDB: 1RIE - X-ray structure of Rieske protein (water-soluble fragment) of the bovine mitochondrial cytochrome bc1 complex PDB: 1RFS - X-ray structure of Rieske protein (water-soluble fragment) of the spinach chloroplast cytochrome b6 fcomplex PDB: 1FQT - X-ray structure of Rieske-type ferredoxin associated with biphenyl dioxygenase from Burkholderia cepacia PDB: 1G8J - X-ray structure of Rieske subunit of arsenite oxidase from Alcaligenes faecalis PDB: 2I7F - X-ray structure of the Sphingomonas yanoikuyae B1 Rieske ferredoxin PDB: 2QPZ - X-ray structure of the Pseudomonas Naphthalene 1,2-dioxygenase Rieske ferredoxin InterPro: IPR005806 - InterPro entry for Rieske [2Fe-2S] region
== Recent studies == Recently thermospray was also utilized for the production of semiconductor nanocrystals, analysis of bile acids, identification of dyes, and molecular weight determinations of proteins from multiply charged ions.
Sources: en.wikipedia.org
SPPS is limited by reaction yields due to the exponential accumulation of by-products, and typically peptides and proteins in the range of 40 or 50 amino acid residues are pushing the limits of synthetic accessibility of SPPS products as homogeneous molecules of defined chemical structure. Synthetic difficulty also is sequence dependent; typically aggregation-prone sequences such as amyloids are difficult to make. Longer peptides can be accessed by using approaches such as native chemical ligation, where two unprotected synthetic peptides can be covalently condensed in aqueous solution.
episclera stroma lamina fusca endothelium The sclera is opaque due to the irregularity of the Type I collagen fibers, as opposed to the near-uniform thickness and parallel arrangement of the corneal collagen. Moreover, the cornea bears more mucopolysaccharide (a carbohydrate that has among its repeating units a nitrogenous sugar, hexosamine) to embed the fibrils. The cornea, unlike the sclera, has six layers. The middle (third in number; provided the first layer being the anterior and outermost and the sixth layer being the posterior and the inner most), thickest layer is also called the stroma. The sclera, like the cornea, contains a basal endothelium, above which there is the lamina fusca, containing a high count of pigment cells. Sometimes, very small gray-blue spots can appear on the sclera, a harmless condition called scleral melanocytosis.
Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or converted to fatty acids through a reaction via acetyl-CoA. It can also be used to construct the amino acid alanine and can be converted into ethanol or lactic acid via fermentation. Pyruvic acid supplies energy to cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactate when oxygen is lacking.
Sources: en.wikipedia.org
== Prognosis == Venous ulcers are costly to treat, and there is a significant chance that they will recur after healing; one study found that up to 48% of venous ulcers had recurred by the fifth year after healing. However, treatment with local anaesthetic endovenous techniques suggests a reduction of this high recurrence rate is possible. Without proper care, the ulcer may get infected, leading to cellulitis or gangrene and eventually may need amputation of the part of the limb in the future. Some topical drugs used to treat venous ulcer may cause venous eczema.
The Bureau ruled that the deal was "unlikely to result in a substantial lessening or prevention of competition." Former CEO Marc Caira reassured the integrity of Tim Hortons following the purchase, stating that the acquisition would "enable us to move more quickly and efficiently to bring Tim Hortons iconic Canadian brand to a new global customer base." On October 30, 2014, various media covered a Canadian Centre for Policy Alternatives study which suggested that Burger King's proposed takeover of Tim Hortons is "likely to have overwhelmingly negative consequences for Canadians." This study analyzed Burger King's private equity owner, 3G Capital, and past takeovers of Burger King, Heinz, and Anheuser-Busch, and declared that "it has a 30-year history of aggressive cost cutting, which could hurt Tim Hortons employees, small-businesspeople, Canadian taxpayers, and consumers." The deal was approved by Minister of Industry James Moore (of the governing Conservative Party of Canada) on December 4, 2014: The two companies agreed to Moore's conditions, requiring that the Burger King and Tim Hortons chains retain separate operations and not combine locations, maintain "significant employment levels" at the Oakville headquarters, and ensure that Canadians make up at least 50% of Tim Hortons' board of directors. Tim Hortons shareholders approved the merger on December 9, 2014; the two chains merged under the new parent company Restaurant Brands International (RBI), which began trading on December 15, 2014.
== Physical characteristics == When first extracted from the pine cone, they are covered with a hard shell (seed coat), thin in some species and thick in others. The nutrition is stored in the embryo (sporophyte) in the center. Although a nut in the culinary sense, in the botanical sense, pine nuts are seeds; being a gymnosperm, they lack a carpel (fruit) outside. The shell must be removed before the pine nut can be eaten. Unshelled pine nuts have a long shelf life if kept dry and refrigerated (−5 to 2 °C or 23 to 36 °F); shelled nuts (and unshelled nuts in warm conditions) deteriorate rapidly, becoming rancid within a few weeks or even days in warm, humid conditions. Pine nuts are commercially available in the shelled form, but due to poor storage, they can have poor flavor and may already be rancid at the time of purchase. Consequently, pine nuts are often frozen to preserve their flavor. European pine nuts may be distinguished from Asian ones by their greater length than girth; Asian pine nuts are stubbier, shaped somewhat like long kernels of corn. The American piñon nuts are known for their large size and ease of shelling. In the United States, Pinus edulis, the hard shell of New Mexico and Colorado, became a sought-after species due to the trading post system and the Navajo people who used the nuts as a means of commerce. The Italian pine nut (P. pinea) was brought to the United States by immigrants and became a favored treat along the East Coast in the early 1930s, when bumper crops of American pine nuts were readily available at low prices.
The two substrates of this enzyme are (S)-dihydroorotic acid and oxidised nicotinamide adenine dinucleotide (NAD+). Its products are orotic acid, reduced NADH, and a proton. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (S)-dihydroorotate:NAD+ oxidoreductase. This enzyme is also called orotate reductase (NADH). This enzyme participates in pyrimidine metabolism. It has 2 cofactors: flavin adenine dinucleotide, and flavin mononucleotide.
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 consists mainly of animal experiments and small clinical reports, with much of the clinical material published in Russian-language journals. Large independent trials are scarce. Separating reliable effects from chance findings is consequently difficult.