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The solution-phase synthesis of organic compounds as mixtures rather than in individual pure form offers efficiency advantages that are negated by the difficulty in separating and identifying the components of the final mixture. Here, a strategy for mixture synthesis that addresses these separation and identification problems is presented. A series of organic substrates was tagged with a series of fluorous tags of increasing fluorine content. The compounds were then mixed, and multistep reactions were conducted to make enantiomers or analogs of the natural product mappicine. The resulting tagged products were then demixed by fluorous chromatography (eluting in order of increasing fluorine content) to provide the individual pure components of the mixture, which were detagged to release the final products. 相似文献
3.
Seidell A 《Science (New York, N.Y.)》1924,60(1559):439-447
There has been a notable revival of interest in the chemistry of vitamins within the past few years. The recent work has led to the isolation of more or less completely crystalline compounds having the properties ascribed to vitamins A, B and D. The evidence now available appears to definitely establish the conclusion that vitamins are not to be classed with enzymes. The physiologically active crystalline products which now for the first time have been isolated make possible intensive studies of the constitution and chemical properties of the several vitamins. Although many years have been required to obtain these elusive compounds in the state of purity now reported, it is probable that their identification will be accomplished in a much shorter time. With the completion of this latter phase of the problem we may confidently look forward to the eventual synthesis of the vitamins and their extensive application to the nutritive needs of man. 相似文献
4.
The remarkable specificity of an antibody molecule has been used to accomplish highly selective functional group transformations not attainable by current chemical methods. An antibody raised against an amine-oxide hapten catalyzes the reduction of a diketone to a hydroxyketone with greater than 75:1 regioselectivity for one of two nearly equivalent ketone moieties. The antibody-catalyzed reaction is highly stereoselective, affording the hydroxyketone in high enantiomeric excess. Similarly, the reduction of ketones containing branched and aryl substituents, including the highly symmetrical 1-nitrophenyl-3-phenyl-2-propanone, was enantioselective. The simple strategy presented herein may find general applicability to the regio- and stereoselective reduction of a broad range of compounds. 相似文献
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The distinct properties of fluorous phases are practically useful for separation, purification, and reaction control in organic synthesis. Here, we report the formation of a liquid-like fluorous droplet, composed of 24 perfluoroalkyl chains confined in the interior of a 5-nanometer-sized, roughly spherical shell that spontaneously assembled in solution from 12 palladium ions and 24 bridging ligands. Crystallographic analysis confirmed the rigid shell framework and amorphous interior. Perfluoroalkanes can dissolve in this well-defined fluorous phase, whereas they can hardly dissolve in a surrounding polar organic solution, and their solubility (up to approximately eight perfluoroalkane molecules per spherical complex) can be finely controlled by tuning the length of perfluoroalkyl chains tethered to the shell. 相似文献
6.
“胰岛素-转铁蛋白-硒钠”对山羊卵母细胞体外成熟及胚胎发育的影响 总被引：1，自引：0，他引：1
[目的]为提高山羊卵母细胞及胚胎体外培养的效率,探索无血清体外培养体系。[方法]在目前卵母细胞体外成熟及胚胎培养所用的常规培养液中添加1%ITS(胰岛素-转铁蛋白-硒钠)或以1%ITS分别替代2种培养液中FBS,对山羊卵母细胞及孤雌激活胚胎进行体外培养,检测ITS对其发育率的影响。[结果]添加ITS到卵母细胞成熟液中,对卵母细胞成熟率没有明显提高,但显著提高了其激活后孤雌胚胎的囊胚率(58.06%vs.48.19%);以ITS替代成熟液中FBS,取得了与FBS组相似的成熟率、卵裂率和囊胚率。添加ITS到胚胎培养液中,显著提高了山羊孤雌胚胎的囊胚率(68.30%vs.56.82%);以ITS替代胚胎培养液中FBS,卵裂率与FBS组无显著差异,囊胚率显著低于FBS组(42.33%vs.56.82%)。[结论]ITS对山羊卵母细胞体外成熟及胚胎早期发育均有促进作用;另外,ITS可以替代卵母细胞成熟培养液中的血清,作为无血清培养体系用于相关研究。 相似文献
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“胰岛素-转铁蛋白-硒钠”对山羊卵母细胞体外成熟及胚胎发育的影响(英文) 总被引：8，自引：2，他引：6
[Objective] The research aimed to enhance culture efficiencies of oocyte and embryo of goat in vitro and to explore serum-free culture system in vitro.[Method] At present,the conventional solutions of oocyte maturation and embryo development in vitro were always added into 1% ITS(Insulin-transferrin-selenium) or using 1% ITS to replace FBS in 2 kinds culture solutions for conducting in vitro cultures of goat oocyte and parthenogenetic embryo.The influences of ITS on their developments were detected.[Result] ITS in maturation liquid of oocytes could not increase oocytes maturation rate but significantly increased blastocyst rate (58.06% vs. 48.19%)of parthenogenetic embryo.If FBS in maturation liquid of oocytes was replaced by ITS, the maturation rate, cleavage rate and blastocyst rate were basically unchanged.Adding ITS into embryo medium could increase blastocyst rate (68.30% vs. 56.82%)of parthenogenetic embryo of goat.If FBS in embryo medium was replaced by ITS,the cleavage rate didn’t change basically,while the blastocyst rate in ITS was obviously lower than that in FBS group(42.33% vs.56.82%).[Conclusion] ITS could promote maturation of oocyte in vitro and early embryonic development, in addition,ITS could replace serum in maturation medium of oocyte as serum-free culture system for conducting relevant researches. 相似文献
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Transannular chemical reactions are unparalleled in their ability to generate high degrees of stereochemical and architectural complexity in a single transformation. However, the successful application of this approach in synthesis depends on the ability to predict and control the outcome of the transannular reaction. Use of a chiral catalyst in this context represents an attractive, yet unused, strategy. This report describes a catalytic, asymmetric transannnular Diels-Alder (TADA) reaction that affords polycyclic products in high enantiomeric excess. This catalyst system can also alter the inherent diastereoselectivity of cyclizations with substrates containing chiral centers. Additionally, the catalytic enantioselective TADA has been used as the key step in a total synthesis of the sesquiterpene 11,12-diacetoxydrimane; this route may provide a general approach to the polycyclic carbon framework shared by many terpene natural products. 相似文献
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[目的]为分离和鉴定莲藕中的多酚奠定基础。[方法]利用薄层层析色谱法,以硅胶G60为固定相,以甲苯-乙酸乙酯-冰醋酸为流动相,以儿茶素为对照品,用FeCl3-K3Fe(CN)6为显色剂,对莲藕多酚酯相组分中酚类物质进行分离和鉴定,并分析不同的展开剂对组分分离的影响。[结果]莲藕多酚酯相展开的第2个斑点与标准品儿茶素所对应的斑点Rf值相同,初步确定莲藕多酚酯相中有儿茶素成分。薄层层析利用所选的6种展开剂均得到很好的分离效果,其Rf值在0.49~0.61范围内,符合薄层层析中Rf值定性的要求。[结论]薄层色谱高效、灵敏、快速,为初步鉴定莲藕中的儿茶素化合物提供了较好的检测方法。 相似文献
10.
COHEN SS 《Science (New York, N.Y.)》1963,139(3559):1017-1026
Examples of variability and apparent innovation presented in this paper are but a portion of the many examples in the literature. Thus, the notion of the "unity of biochemistry" has been advanced in an overly simplified form and reflects a primitive stage in the development of the discipline. Cells contain many more compounds and biosynthetic mechanisms than we had suspected or list in our texts. Accordingly, either early chemical evolution was far more extensive than we have postulated or an evolution of biochemical synthesis and function took place which was more extensive than has been postulated; perhaps both have occurred. The chemical choices available from the environment have been considerable rather than limited and the cells have chosen, adapted, improved upon a limited number of these, and in turn have themselves been selected. In the case of the naturally occurring antibiotic substances, biosynthetic mechanisms for compounds which do not fit within the cells' own nucleic acids and proteins to advantage have nevertheless been preserved since they contribute to survival. On the other hand, some of these compounds such as alpha-ribazole, are fitted to other metabolic uses. The existence of the large number of uncommon relatives of the common components of the nucleic acids and proteins in turn implies an enormous untapped area of potential knowledge concerning their paths of biosyntheses and the genetic and physiological controls for these same paths. That these compounds exist perhaps also indicates an expanded material basis for a continuing biochemical evolution. 相似文献
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[目的]延长化工用鲜海带使用周期,实现海带的规模化存贮。[方法]将不同尺寸的海带样品保存在浓度2%的甲醛溶液中,考察海带碎块大小以及化学物质的添加对海带中褐藻胶含量和黏度的影响。[结果]在浓度2%的甲醛溶液中,大块海带样品的褐藻胶得率和黏度要明显高于小块海带;化学物质的加入会加速海带中褐藻糖胶、褐藻淀粉等可溶性物质的溶出,化学试剂CaCl2的添加有助于提高保存海带中褐藻胶得率。[结论]建议在规模化海带保存过程中采用大块海带浸醛法（浓度2%甲醛溶液）,以保证海带中褐藻胶的黏度和收率,达到理想的保存效果。 相似文献
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Woodall JM 《Science (New York, N.Y.)》1980,208(4446):908-915
The III-V compounds and alloys have been studied for three decades. Until recently, these materials have been commercialized for only a few specialized optoelectronic devices and microwave devices. Advances in thin-film epitaxy techniques, such as liquid phase epitaxy and chemical vapor deposition, are now providing the ability to form good quality lattice-matched heterojunctions with III-V materials. New optoelectronic devices, such as room-temperature continuous-wave injection lasers, have already resulted. This newfound ability may also affect the field of highspeed integrated circuits. 相似文献
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[目的]使用多种培养成分组合,筛选出一个适合山羊诱导性多能干细胞(induced pluripotent stem cells,i PSCs)的培养体系。[方法]采用慢病毒作为载体,携带多能因子,采用多种培养成分(培养基、血清和细胞因子)的组合培养山羊i PSCs,优化其培养体系。[结果]用FBS代替KSR可以提高克隆的形成效率以及克隆的质量,而用DMEM/F12代替KNOCKOUT-DMEM,i PSCs克隆的形成效率和克隆质量没有明显的改善。带有β-FGF的培养体系可以保持i PSCs未分化的状态,而培养体系中只加LIF不能维持i PSCs未分化的状态。[结论]该研究成功诱导出山羊i PSCs,且能在体外传代培养。 相似文献
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Chiu DT Wilson CF Ryttsén F Strömberg A Farre C Karlsson A Nordholm S Gaggar A Modi BP Moscho A Garza-López RA Orwar O Zare RN 《Science (New York, N.Y.)》1999,283(5409):1892-1895
Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes. 相似文献
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Agricultural sprayers are utilized in applying pesticides to control pests and diseases in crops. The increase in machine size and a better control system have been associated with increased productivity, improved efficiency and minimized the impact of the chemical on the environment. However, wider booms may contribute to application error due to the difference in speed between the inner and outer boom section when applying in curvilinear passes. Field tests were conducted in three irregular shaped fields with varying terrain using a 36.6-m self-propelled sprayer with a turn compensation technology. The results showed that turning occurred near the grassed waterways, boundaries and end of headlands. The product was applied during turning to 19.0% of Field 1, 17.8% of Field 2 and 22.5% of Field 3. These could have been the percentage of field areas that may receive more or less product if the sprayer was not equipped with turn compensation technology. As expected, the speed difference between the inner and outer boom increases as the radius of turn decreases. The speed difference could translate to an under-application on the outer boom section where the speed is much faster and over-application on the inner boom section where the speed is slower. The application errors from such speed differential could vary from ??48.2 to +?1058.0%, depending on the turning radius. However, the pulse width modulation system implemented duty cycles based on turning speeds, which resulted to a 90.0% application rate uniformity across the field regardless of the travel path during operation.
相似文献16.
有机锡化合物的合成与应用 总被引：3，自引：0，他引：3
有机锡化合物的合成经历了传统的格氏试剂间接合成法、利用金属锡和卤代烃的直接合成法两个时期。研究工作由早期的主要侧重于合成、推测结构,到20十世纪80年代的侧重于结构的表征及生物活性的有效利用。有机锡化合物研究工作的长足发展是近几年的工作,被用于醇醛缩合及醇酸酯化反应的催化剂。有机锡化合物与酸催化剂相比,具有用量少、无污染、不腐蚀仪器设备等优点。 相似文献
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根据雌激素类化合物在机体内的作用机理，以增强型绿色荧光蛋白（EGFP）基因为报告基因构建了4个启动子不同的表达载体(pERE-SV-EGFP, pERE-TA-EGFP, pERE-CMV-EGFP, pERE-TK-EGFP)。以这些表达载体瞬时转染MCF-7细胞，报告基因的基础表达与启动子的强度相关。以17β-雌二醇(E2 ,10-9 mol·L-1)诱导表达载体瞬时转染的MCF-7细胞，发现在表达载体pERE-TA-EGFP、pERE-TK-EGFP、pERE-SV-EGFP转染的MCF-7细胞中，E2能诱导2倍以上的报告基因的表达。这表明在这些瞬时表达系统中报告基因的表达是雌激素依赖性的，因此这些表达载体可用于稳定转染以建立稳定表达分析系统。 相似文献
18.
Theoretical and experimental support is presented for the hypothesis that many organic compounds may form under conditions of thermodynamic equilibrium. This possibility must be considered along with special effects of selective catalysts, radiation, and degradation from biological matter, in explaining the origin of organic compounds in carbonaceous chondrites. Similar considerations may apply to solar nebulas and planetary atmospheres. The equilibrium distribution of organic compounds at temperatures between 300 degrees K and 1000 degrees K and pressures of 10-(6) to 50 atm for the C-H-O system have been computed. At moderate temperatures and low pressures, conditions where graphite production is inhibited, aromatic compounds may form even in the presence of large excesses of hydrogen. Such conditions exist in the solar nebula and in the atmospheres of some of the major planets. Equilibrium concentrations of a large number of compounds at 1000 degrees K with nitrogen, sulfur, and chlorine added to the system have also been determined. In some cases, a limited equilibrium method is employed in which those few compounds which form with the most difficulty are excluded from the computations, while representatives of all other families of compounds are included. This approach is shown to be useful in the interpretation of certain experimental data in which complete equilibrium has not been attained. We have also found that gases, activated to the plasma state by a high-energy radio frequency field, recombine on cooling to yield product mixtures which are in qualitative agreement with those predicted by the equilibrium computations. We believe that such products can be profitably studied as if at a metastable limited equilibrium. 相似文献
19.
为探讨细胞培养基中血清浓度对鸡盲肠上皮细胞体外培养的影响,分别用含0%、2.5%、5%和10%胎牛血清(FBS)的细胞培养液培养鸡胚盲肠上皮细胞,检测细胞活性;选择适宜的FBS浓度,并测定了该浓度条件下鸡盲肠上皮细胞的生长特性。结果表明:用含2.5%和5%FBS的培养基培养鸡胚盲肠上皮细胞,第4天细胞贴壁率达最高,分别为84%和80.33%,显著地高于无血清和10%FBS组(P<0.01/0.05),第7天仍均维持在76%以上,两者间除了第2天外,其余差异均不显著;用含2.5%FBS的细胞培养基进行鸡胚盲肠上皮细胞原代培养,第2~3天为适应阶段,第3~5天处于对数生长期,第5~9天细胞进入减速期,第10~11天再次进入对数生长期,第11天以后细胞进入衰退期,整个过程持续14 d左右。鸡胚盲肠上皮细胞培养的血清浓度以2.5%FBS为宜。 相似文献
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Acute toxicity in a water solution of tetrahydrate manganese succinate has been studied in the course of intraperitoneal administration to mice. The results of investigations proved it to be a low-toxicity preparation which enables the application of manganese succinate in pharmacology, medicine, veterinary science, the food and chemical industries as a medical drug and a biologically active additive and reagent in various kinds of synthesis. 相似文献