The short version of counter-ion fits in a sentence. The long version — which is the one that helps — is below.
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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。
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.
Verification of a supplied batch generally combines a certificate of analysis with independent testing, because certificates are self-reported documents. A typical package includes a chromatographic trace, a mass spectrum, and a stated water or counter-ion content. Batch-to-batch consistency matters more than a single purity figure when results are compared across experiments. No single mandatory standard governs research-grade peptide release, so laboratories are expected to define their own acceptance criteria. Residual trifluoroacetate from purification is a frequently overlooked counter-ion.
| Property | Value | Notes |
|---|---|---|
| 结构类别 | 线性合成七肽 | 无环化结构，不含二硫键 |
| 氨基酸序列 | Met-Glu-His-Phe-Pro-Gly-Pro | N 端为甲硫氨酸 |
| 分子量 | 约 814 Da | 游离碱形式的计算值 |
| 外观 | 白色至类白色粉末 | 具吸湿性 |
| 溶解性 | 易溶于水 | 亦可溶于甲醇等极性溶剂 |
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.
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.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It was derived from the ACTH(4-10) fragment, a short segment of adrenocorticotropic hormone that lacks the hormonal activity associated with the full-length peptide. Researchers at the Institute of Molecular Genetics in Moscow developed the compound during the 1980s. It has been registered as a pharmaceutical product in Russia and several neighbouring countries, where it is supplied as a nasal solution, and it is also sold internationally as a research chemical.
The proposed mechanism centres on neurotrophic signalling rather than direct receptor activation. Semax is reported to increase expression of brain-derived neurotrophic factor and nerve growth factor in several brain regions, and to shift the balance between excitatory and inhibitory neurotransmitter systems. Interaction with melanocortin receptors has been suggested because of the parent ACTH fragment. Many of these findings come from rodent studies, and the extent to which they translate to human physiology remains an open question.
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。
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。
Fifteen minutes later Faith 7 landed just four miles (6 km) from the prime recovery ship, the carrier USS Kearsarge. This was the most accurate landing to date, despite the lack of automatic controls. Faith 7 landed 70 nautical miles (130 km) southeast of Midway Island, in the Pacific Ocean. This would be near 27°30′N 176°15′W. Splashdown was at 34 hours 19 minutes 49 seconds after liftoff. The spacecraft tipped over in the water momentarily, then righted itself. Helicopters dropped rescue swimmers and relayed Cooper's request of an Air Force officer for permission to be hoisted aboard the Navy's carrier. Permission was granted. Forty minutes later the explosive hatch blew open on the deck of Kearsarge. Cooper stepped out of Faith 7 to a warm greeting.
==== Benzoctamine and sodium amylobarbitone ==== In a study used to compare benzoctamine to sodium amylobarbitone as a sleep promoter, it was found that during administration of both drugs, patients reported that their sleep was less restless, and drowsiness was diminished. The study further showed that while sodium amylobarbitone caused withdrawal rebound symptoms, benzoctamine did not. It was also found that benzoctamine reduced plasma corticosteroid hormone levels. There is a relationship between anxiety and adreno-corticosteroid activity, with raised levels commonly being reported as an indication of stress. The study showed that benzoctamine, a drug reported to reduce anxiety, was also able to reduce the hormones that potentially cause it. This points to a phenomenon often seen within pharmacology where drugs intended for other uses often have far-reaching and rarely considered effects.
The journey across the United States began on 15 July 1988. On the journey he slept in bushes beneath the World Trade Center, camped outside Kennedy Airport in a tent, then headed west. On Staten Island he collapsed from heat exhaustion at 105 degrees Fahrenheit. In Utah the temperatures went down to minus 30 Fahrenheit. Carrying a tent and a backpack, with no backup, he walked alone to Niagara Falls, through Ontario in Canada, to Detroit, between the Great Lakes, across the Great Plains, through the Rockies in winter, to Yellowstone National Park, then south to the Grand Canyon, on to Las Vegas, through Death Valley and then snowshoed over the Sierras to reach San Francisco. In Death Valley, down to his last $13, Skinner found $200 in the desert, and he had $1 left when he crossed the Sierras to reach Yosemite Valley. The total distance he walked from New York City to San Francisco, was 4,952 miles (7,969 km). On the journey he visited 70 hospices and appeared on television, radio and in newspapers to encourage support for hospices across the U.S. and Canada. The mayor of San Francisco, Art Agnos, proclaimed 21 March 1989, "Colin Skinner Day," in recognition of the attention he brought to the work of hospices with AIDS patients in the city. Returning to Britain after this walk, he obtained a job as a research assistant in Chemical Pathology at the Middlesex Hospital and went on to obtain a PhD in Molecular Biology at University College London.
Sources: en.wikipedia.org
The cephalopod radula consists of multiple symmetrical rows of up to nine teeth – thirteen in fossil classes. The organ is reduced or even vestigial in certain octopus species and is absent in Spirula. The teeth may be homodont (i.e. similar in form across a row), heterodont (otherwise), or ctenodont (comb-like). Their height, width and number of cusps is variable between species. The pattern of teeth repeats, but each row may not be identical to the last; in the octopus, for instance, the sequence repeats every five rows. Cephalopod radulae are known from fossil deposits dating back to the Ordovician. They are usually preserved within the cephalopod's body chamber, commonly in conjunction with the mandibles; but this need not always be the case; many radulae are preserved in a range of settings in the Mason Creek. Radulae are usually difficult to detect, even when they are preserved in fossils, as the rock must weather and crack in exactly the right fashion to expose them; for instance, radulae have only been found in nine of the 43 ammonite genera, and they are rarer still in non-ammonoid forms: only three pre-Mesozoic species possess one.
== References == Papernow, Patricia L. (1993). Becoming a Stepfamily: Patterns of Development in Remarried Families. San Francisco: Jossey-Bass. Warner, Marina (1995). From the Beast to the Blonde: On Fairy Tales and Their Tellers. New York: Farrar, Straus and Giroux. ISBN 978-0-374-15901-6. Tatar, Maria (1987). The Hard facts of the Grimm's fairy tales. Princeton, NJ: Princeton University Press. ISBN 978-0-691-06722-3. Tatar, Maria (2002). The annotated classic fairy tales. New York London: W. W. Norton & Company. ISBN 978-0-393-05163-6.
== The Protein == The 25-kDa core protein (excluding the heavy glycosylation) of rodent Thy-1 is 111 or 112 amino acids in length, and is N-glycosylated at three sites (In contrast to only two glycosylation sites for human Thy-1). The 162aa (murine, 161 for human) Thy1 precursor has 19 amino acid (aa 1–19) signal sequence and 31 amino acid (aa 132–162) C-terminal transmembrane domain that is present in pro form but removed when transferring the 112 amino acid (aa 20–131) mature peptide to GPI anchor which would attach through the aa 131. Some of the common monoclonal antibodies used to detect this protein are clones OX7, 5E10, K117 and L127. There have been some reports of Thy1 monoclonal antibodies cross reacting with some cytoskeletal elements: anti Thy-1.2 with actin in marsupial, murine, and human cells and anti Thy-1.1 with vimentin, and were suggested to be due to sequence homology by studies done more than 20 years back. Thy-1, like many other GPI anchored proteins can be shed by special types of Phospholipase C e.g. PI-PLC (phosphatidyl-Inositol Phospholipase C, or PLC β). it can also be involved in cell to cell transfer of GPI anchored proteins like CD55 and CD59.
Sources: en.wikipedia.org
=== Climate change === Dyson agreed that technically humans and additional CO2 emissions contribute to warming. However, he felt that the benefits of additional CO2 outweighed any associated negative effects. He said that in many ways increased atmospheric carbon dioxide is beneficial, and that it is increasing biological growth, agricultural yields and forests. He believed that existing simulation models of climate change fail to account for some important factors, and that the results thus contain too great a margin of error to reliably predict trends. He argued that political efforts to reduce the causes of climate change distract from other global problems that should take priority, and viewed the acceptance of climate change as comparable to religion. In 2009, Dyson criticised James Hansen's climate-change activism. "The person who is really responsible for this overestimate of global warming is Jim Hansen. He consistently exaggerates all the dangers... Hansen has turned his science into ideology." Hansen responded that Dyson "doesn't know what he's talking about... If he's going to wander into something with major consequences for humanity and other life on the planet, then he should first do his homework- which he obviously has not done on global warming".
=== Matrix application === The matrix must absorb at the laser wavelength and ionize the analyte. Matrix selection and solvent system relies heavily upon the analyte class desired in imaging. The analyte must be soluble in the solvent in order to mix and recrystallize the matrix. The matrix must have a homogeneous coating in order to increase sensitivity, intensity, and shot-to-shot reproducibility. Minimal solvent is used when applying the matrix in order to avoid delocalization. One technique is spraying. The matrix is sprayed, as very small droplets, onto the surface of the sample, allowed to dry, and re-coated until there is enough matrix to analyze the sample. The size of the crystals depend on the solvent system used. Sublimation can also be used to make uniform matrix coatings with very small crystals. The matrix is placed in a sublimation chamber with the mounted tissue sample inverted above it. Heat is applied to the matrix, causing it to sublime and condense onto the surface of the sample. Controlling the heating time controls the thickness of the matrix on the sample and the size of the crystals formed. Automated spotters are also used by regularly spacing droplets throughout the tissue sample. The image resolution relies on the spacing of the droplets.
Hong Kong has the world's largest number of skyscrapers, with 554 towers taller than 150 metres (490 ft), and the third-largest number of high-rise buildings in the world. The lack of available space restricted development to high-density residential tenements and commercial complexes packed closely together on buildable land. Single-family detached homes are uncommon and generally only found in outlying areas. The International Commerce Centre and Two International Finance Centre are the tallest buildings in Hong Kong and are among the tallest in the Asia-Pacific region. Other distinctive buildings lining the Hong Kong Island skyline include the HSBC Main Building, the anemometer-topped triangular Central Plaza, the circular Hopewell Centre, and the sharp-edged Bank of China Tower.
Sources: en.wikipedia.org
不存在。它是依据 ACTH 的一段序列人工设计的分子，天然蛋白质中找不到与之完全相同的七肽。名称属于研究代号，而非天然物质名。
Semax 对应 ACTH 第 4 至第 10 位的片段，并在两端做了替换与延长，使其不再具备促肾上腺皮质激素的典型内分泌活性。这一改动同时改变了它在体内的稳定性与分布特征。
俄罗斯将其列为处方药物，需要医生开具处方。多数其他国家把它当作研究化合物，不能作为药品销售或宣称疗效。具体合法性取决于当地法规。
Dry powder is normally held at -20 °C or lower, away from light and moisture. Sealed vials can also be kept at 2-8 °C for shorter intervals. Warming to room temperature before opening prevents condensation.