RP-HPLC 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.
Last reviewed on 2026-01-12. Where a claim depends on a specific study, the study is described rather than over-claimed.
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。
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.
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.
| 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 是人工设计的七肽，序列为 Met-Glu-His-Phe-Pro-Gly-Pro，骨架取自促肾上腺皮质激素片段 ACTH(4-10)。它于二十世纪八十年代在苏联的分子遗传学研究机构内合成。设计目标是保留该片段与注意力和记忆相关的活性，同时剔除促皮质激素释放等内分泌作用。此后俄罗斯将其登记为药品并进入临床使用。
当时的短肽研究普遍关注能否穿越血脑屏障、在低剂量下产生中枢效应，Semax 属于这一路线。鼻内给药是其主要使用方式，俄语文献报道的适应症涵盖缺血性卒中、短暂性脑缺血发作、认知功能减退以及视神经病变。这些研究大多发表在当地期刊上，样本规模与终点设置同西方试验惯例存在差异，国际同行对其临床证据的强度看法不一。
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.
== Transport mechanisms == The transport of norepinephrine back into presynaptic cell is made possible by the cotransport with Na+ and Cl−. The sequential binding of the ions results in the eventual reuptake of norepinephrine. The ion gradients of Na+ and Cl− make this reuptake energetically favorable. The gradient is generated by the Na+/K+-ATPase which transports three sodium ions out and two potassium ions into the cell. NETs have conductances similar to those of ligand-gated ion channels. The expression of NET results in a leak-channel activity.
This test can't determine the precise distance of gun to target, however, it is often used around holes to determine if it is consistent with the passage of a bullet. The Harrison and Gilroy method was introduced in 1959. It is a colorimetric test used to verify the presence of antimony, lead and/or barium. The test involves dampening a cloth with 0.1M hydrochloric acid (HCl), swabbing the item being analysed and allowing that to dry before subjecting it to various reagents. The sensitivities of the reagents used makes this test very unreliable and unrealistic for crime scene analysis.
fluorescence in situ hybridization (FISH) A type of in situ hybridization assay where the oligonucleotide probes are labelled with a chemical compound that is naturally fluorescent when exposed to light at particular wavelengths, making it possible to detect the in situ locations of complementary sequences with fluorescence microscopy. FISH is commonly used to visualize the physical locations of specific genes on chromosomes.
Sources: en.wikipedia.org
== Synthesis == The traditional route to dithiothreitol (and its isomer dithioerythritol) is sulfidation of the extremely lachrymatory 1,4-Dibromobut-2-ene. Modern industrial syntheses instead use related epoxides and hydrogen sulfide.
The implementation of Trump's plans would add around 4 billion tons of carbon dioxide to the atmosphere by 2030, also having effects on the international level. If the policies do not change further, it would add 15 billion tons by 2040 and 27 billion by 2050. Although the exact calculation is difficult, researchers stated: "Regardless of the precise impact, a second Trump term that successfully dismantles Biden's climate legacy would likely end any global hopes of keeping global warming below 1.5C."
=== EC 1.8.1 With NAD+ or NADP+ as acceptor === EC 1.8.1.1: deleted EC 1.8.1.2: sulfite reductase (NADPH) EC 1.8.1.3: deleted; reaction shown to be due to EC 1.14.13.8, flavin-containing monooxygenase EC 1.8.1.4: dihydrolipoyl dehydrogenase EC 1.8.1.5: 2-oxopropyl-CoM reductase (carboxylating) EC 1.8.1.6: cystine reductase EC 1.8.1.7: glutathione-disulfide reductase EC 1.8.1.8: protein-disulfide reductase EC 1.8.1.9: thioredoxin-disulfide reductase EC 1.8.1.10: CoA-glutathione reductase EC 1.8.1.11: asparagusate reductase EC 1.8.1.12: trypanothione-disulfide reductase EC 1.8.1.13: bis-γ-glutamylcystine reductase EC 1.8.1.14: CoA-disulfide reductase EC 1.8.1.15: mycothione reductase EC 1.8.1.16: glutathione amide reductase EC 1.8.1.17: dimethylsulfone reductase EC 1.8.1.18: NAD(P)H sulfur oxidoreductase (CoA-dependent) EC 1.8.1.19: sulfide dehydrogenase EC 1.8.1.20: 4,4′-dithiodibutanoate disulfide reductase EC 1.8.1.21: dissimilatory dimethyldisulfide reductase EC 1.8.1.22: dissimilatory sulfite reductase
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。
Each freeze-thaw cycle can degrade a fraction of the peptide and promote aggregation. Dividing a stock solution into single-use volumes removes repeated cycling as a variable. It also limits the time a thawed solution spends at room temperature.