无患子皂苷的抗菌活性研究

本研究检测了无患子皂苷对6种典型细菌和6种典型真菌的抗菌活性。提取无患子假种皮中总皂苷R1和R2,分离得到皂苷混合物样品R1-3、R1-4、R1-5、R1-6、R1-7、R2-5、R2-6、R2-7、R2-8、R2-9和R2-10;采用滤纸片琼脂扩散法对其抑菌活性进行检测,得出抑菌圈直径、MIC值和EC50值。抑菌活性物质主要集中在样品R1-5、R1-6、R2-7、R2-8、R2-9和R2-10中,这些样品对金黄色葡萄球菌、枯草芽孢杆菌、蜡状芽孢杆菌、大肠杆菌、巨大芽孢杆菌、白色念珠菌、黑曲霉和绿色木霉具有很强的抑菌活性。无患子总皂苷各组分中含有能够显著抑制供试细菌和真菌的活性物质,这为进一步开发利用无患子的药用价值提供了科学依据。     

2-(1-(过氧叔丁基)-3,3,3-三氟丙基)-5-甲氧基-1H-吡咯[3,2-b]吡啶的合成方法研究

以2-乙烯-5-甲氧基-1H-吡咯并[3,2-b]吡啶(化合物A)、三氟甲烷亚磺酸钠、过氧化叔丁醇(70%水溶液)、四水醋酸钴、磷酸钾、无水乙腈为原料合成了2-(1-(过氧叔丁基)-3,3,3-三氟丙基)-5-甲氧基-1H-吡咯[3,2-b]吡啶(化合物B)。设计了正交试验来确定了最佳合成工艺参数为:化合物A与四水醋酸钴摩尔比100:10,化合物A与过氧化叔丁醇摩尔比1:5,反应温度75°C,反应时间10h。该方法在最佳条件下的合成收率为92.3%,纯度99%以上。     

几种醛胺二糖的合成及其生化研究

目的合成几种醛胺二糖化合物,通过对其结构和生化性能的研究,明确了不同的醛胺二糖结构对其生物活性的作用机制。方法:采用化学合成的方法,以戊糖缩二胺(即化合物[1])为原料,合成一系列有机化合物[2-8]。结果:利用H.NMR对这些化合物进行表征,确认其结构。通过对革兰氏细菌的抗菌实验进行生物化学方面的研究。结论:实验结果表明这些醛胺二糖化合物均具有较高的抗菌活性,尤其是化合物[2-4]。     

基于体外实验和分子对接研究枫杨果抑菌活性及分子机制

目的:基于体外实验和分子对接研究枫杨抑菌活性及机制。方法:以枫杨果、树皮、叶为研究对象,分别研究其水提物和醇提物(70%乙醇)对金黄色葡萄球菌、大肠杆菌、绿脓杆菌、伤寒沙门菌、化脓性链球菌、表皮葡萄球菌的抑菌活性,确定抑菌谱和最小抑菌浓度(MIC)。利用活性追踪方法,通过硅胶吸附色谱、薄层色谱等手段,分离单体化合物,并进行抑菌活性研究,选择PBP5、FabI、FabH、Fts Z 4个抑菌关键蛋白靶点,利用Systems Dock Web Site软件进行分子对接,研究其抑菌机制。结果:实验发现枫杨果的醇提物抑菌效果最好,对伤寒沙门菌最小抑菌浓度为7.81 mg/mL,首次从枫杨果中分离得到β-谷甾醇、β-胡萝卜苷、齐敦果酸,三个化合物对于PBP5、FabH、FtsZ蛋白靶点Docking score均大于7,结果活性很好。结论:枫杨果醇提物抑菌谱广、抑菌能力强,其可能是通过抑制革兰氏阳性菌细胞壁肽聚糖的合成,以及细菌脂肪酸的生物合成,干扰其生物膜的形成从而抑制细菌的生长和繁殖,从而起到广谱的抗菌效果。     

巴戟天乙醇粗提物的体外抗菌活性初步研究

目的:对巴戟天乙醇粗提物的体外抗菌活性进行初步研究。方法:采用超声法提取,得到巴戟天浸膏,利用滤纸片法,二倍稀释法分别检测MIC和MBC,对大肠杆菌、金黄色葡萄球菌、枯草杆菌及白色念珠菌等常见细菌及真菌进行体外抗菌活性初步探讨。结果:巴戟天乙醇粗提物对枯草杆菌、金黄色葡萄球菌、大肠杆菌及白色念珠菌都有不同程度的抑菌及杀菌作用,最小抑菌浓度(MIC)分别为0.125g/m L,0.25g/m L,0.5g/m L,0.125g/m L;最小杀菌浓度(MBC)分别为0.5g/m L,1g/m L,1g/m L,0.25g/m L。结论:巴戟天乙醇粗提物对大肠杆菌、金黄色葡萄球菌、枯草杆菌及白色念珠菌均具有抑菌作用,并在一定浓度范围中具有杀菌作用。     

龙脷叶提取物体外抑菌活性初步研究

采用连续二倍梯度琼脂稀释法研究龙脷叶水提物和的50%、70%、95%乙醇提取物的抑菌活性,并对抑菌作用强的提取物以石油醚、乙酸乙酯、正丁醇依次萃取,测定不同极性部位的最低抑菌浓度(MIC)。结果表明,龙脷叶50%乙醇提取物的正丁醇部位对六种试验菌株明显抑制:对金黄色葡萄球菌(Staphylococcus aureus)、金黄色葡萄球菌耐药株(Methicillin resistant Staphylococcus aureus)和大肠杆菌(Escherichia coli)的MIC为15.60m g·mL-1;对铜绿假单胞菌(Pseudomonas aeruginosa)、伤寒沙门氏菌(Salmonella typhi.)和乙型副伤寒沙门氏菌(Bacillus paratyphosus B)的MIC为7.81m g·mL-1。可为进一步研究龙脷叶抑菌活性成分提供依据。     

过渡金属催化的2,3-联烯酸环化合成γ-丁烯酸内酯

γ-丁烯酸内酯是一类具有重要潜在活性的化合物.发展了二价钯催化的2,3-联烯酸和(ω-1)-烯基卤化物的偶联关环反应.反应经过了二价钯催化的氧钯化-碳钯化,重复的去钯氢化/钯氢化及β-脱卤钯化反应.同时还发展了两种联烯之间的二聚环化反应,两分子2,3-联烯酸的反应生成二丁烯酸内酯,2,3-联烯酸与1,2-联烯酮反应则生成呋喃基取代的γ-丁烯酸内酯.     

灯盏细辛乙醚部位化学成分研究

[目的]为进一步明确灯盏细辛药材药效作用的物质基础。[方法]本文采用硅胶、聚酰胺柱层析和重结晶等方法灯盏细辛乙醚提取物进行分离,并根据化合物的理化性质及1H-NMR、13C-NMR、HMBC、HR-MS等方法分析、鉴定化合物结构。[结果]从灯盏细辛乙醚提取部位中分离和鉴定出4个化合物,24(s)-3β-羟基豆甾-5-烯-7-酮(化合物1)、染料木素(化合物2)、3',4'-二甲氧基槲皮素(化合物3)、β-谷甾醇(化合物4)。其中化合物1、2均为首次从灯盏细辛药材中分离得到。[结论]研究结果丰富了灯盏细辛的化学成分内容,为今后的开发提供了科学依据。     

超声萃取-液质联用法测定涂料中禁用阻燃剂的方法研究

本文建立了超声萃取-液质联用法测定涂料产品中三(2-氯乙基)磷酸酯(TCEP)的方法。以丙酮为萃取溶剂,采用超声波萃取法提取样品中的TCEP化合物,液相色谱分离、质谱定性、外标法定量分析。结果显示,TCEP在40μg/L~12750μg/L范围内,线性关系良好,样品平均加标回收率为93.6%~104.1%,相对标准偏差为0.10%~1.70%,方法检出限为20μg/kg,该方法高效、准确、灵敏度高,能够适用于涂料样品快速分析要求。     

2-氧-2,4,5,6,7,7a-六氢噻吩并[3,2-c]吡啶盐酸盐的制备

探索制备普拉格雷合成重要中间体2-氧-2,4,5,6,7,7a-六氢噻吩并[3,2-c]吡啶盐酸盐的较优工艺条件,确定5-三苯甲基-4,5,6,7-四氢噻吩并[3,2-c]吡啶的制备过程中,最佳反应配比为正丁基锂:硼酸三丁酯:30%双氧水=1.00∶1.30∶1.30(物质的量比),2-氧-2,,4,,5,6,7,7a-六氢噻吩并[3,2-c]吡啶盐酸盐制备过程中,用浓盐酸调溶液pH值至2～3,同温搅拌反应3h时,可直接得到产品。     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

To serve and promote science development via innovation

CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

Tracing the origin and early radiation of birds——Paleornithologist ZHOU Zhonghe

With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants."     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

The Information Environment and Universal Service

This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.