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排序方式: 共有2898条查询结果,搜索用时 46 毫秒
41.
Effect of amino acid deletions in the O-glycosylated region of Aspergillus awamori glucoamylase 总被引:1,自引:0,他引:1
Libby Carol Baker; Cornett Catherine A.G.; Reilly Peter J.; Ford Clark 《Protein engineering, design & selection : PEDS》1994,7(9):1109-1114
Aspergillus awamori glucoamylase (GA) contains globular catalyticand starch-binding domains (residues 1471 and 509616,respectively). A heavily O-glycosylated sequence comprises twoparts. The first (residues 441471) in the crystal structurewraps around an /-barrel formed by residues 1440. Thesecond (residues 472508) is an extended, semi-rigid linkerbetween the two domains. To investigate the functional roleof this linker, we made internal deletions to remove residues466512 (GA1), 485512 (GA2) and 466483 (GA3).GA2 and GA3 were expressed in Saccharomyces cerevisiae culturesupernatants at 60 and 20% the wild-type level, respectively,while GA1 was almost undetectable. Western blots comparing extracellularand intracellular fractions indicated that the region deletedin GA3 was critical for secretion, while the region deletedin GA2 contributed to the production of a stable enzyme structure.The activities of purified GA2 and GA3 on soluble and insolublestarch were similar to those of wild-type GA, indicating thatfor soluble starch their deletions did not affect the catalyticdomain and for insoluble starch the linker does not coordinatethe activities of the catalytic and starch-binding domains.The deletions had a significant negative effect on GA2 and GA3thermos tabilities. 相似文献
42.
Robin A. Henderson Robert G. Jensen Carol J. Lammi-Keefe Ann M. Ferris Kenneth R. Dardick 《Lipids》1992,27(11):863-869
To examine the effect of fish oil supplementation on the fatty acid (FA) composition of human milk and maternal and infant
erythrocytes, five lactating women were supplemented with 6 g of fish oil daily for 21d. Usual maternal diets contained 1,147
mg of total n−3 FA, with 120 mg from very long-chain (>C18) n−3 FA. Supplementation increased dietary levels to 3,092 mg of total n−3 FA and 2,006 mg of very long-chain n−3 FA. Milk
samples were collected daily, prior to fish oil ingestion, and at 4-h intervals on days 1, 7, 14 and 21. Milk n−3 FA content
increased within 8 h and reached steady state levels within one week. The n−6 fatty acid content decreased. Erythrocyte eicosapentaenoic
acid content increased from 0.24% to 1.4% (P<0.01) in mothers and from 0.11% to 0.70% (P<0.05) in infants. Docosapentaenoic acid increased from 1.4% to 2.2% (P<0.05) in mothers and from 0.30% to 0.78% (P<0.01) in infants. There was no significant change in docosahexaenoic acid or n−6 fatty acid content. Maternal platelet aggregation
responses were variable. No differences in milk or plasma tocopherol levels were noted.
Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990. 相似文献
43.
The use of electrochemical noise methods (ENM) to study thick, high impedance coatings 总被引:2,自引:0,他引:2
Gordon P. Bierwagen Carol S. Jeffcoate Junping Li S va Balbyshev Dennis E. Tallman Douglas J. Mills 《Progress in Organic Coatings》1996,29(1-4):21-29
Thick, high impedance organic coatings are those class of coatings used to provide corrosion protection to naval vessels, pipelines, gasoline storage tanks, and other large structures such as bridges and plant structures. These coatings, especially the newest generations now being used in practice, can provide exceptional protection and lifetime of performance such that properly and accurately assessing and differentiating among competing coatings is a very difficult task. The standard protocol of salt fog testing (ASTM B117), immersion testing, and outdoor exposure in a corrosive environment with subjective evaluation of a coating's performance durings and after testing, does not adequatcly rank and predict coating lifetimes for new coating systems, especially for the environmentally compliant coating systems such as powder coatings (especially the thick, fusion bonded epoxy (FBE) coatings used for pipelines), two component epoxy and urethane coatings and waterborne coatings. New, objective test methods are desperately needed by users and manufacturers of coatings. A relatively new electrochemical test procedure, electrochemical noise methods (ENM), as developed by Skerry and Eden, has been shown in our laboratory to be very successful in the ranking and prediction of relative coating performance. We have used the method successfully on naval ship coatings, several pipeline coatings and other related systems, and Skerry has used them successfully on industrial maintenance coatings. We have used these methods in conjunction with electrochemical impedance spectroscopy, d.c. resistance measurements and cyclic salt fog testing of the ProhesionTM type. In our studies of pipeline coatings, we needed to investigate thermal effects because of their extended range of use temperature. In these studies, we have discovered that electrochemical methods can be used for an in situ measurement of the Tg of coatings in electrolyte immersion. Further, the ‘plasticizing’ effect of aqueous electrolyte absorption as well as its relative irreversibility has been shown. For all coatings studied, ENM provided useful, objective, numerical data which rapidly ranks coatings and provides useful information on the relative lifetime prediction of coatings which may provide up to 30 years of service. 相似文献
44.
Y.G. Xiao Q. Huang Z.W. Ouyang J.W. Lynn J.K. Liang G.H. Rao 《Journal of Alloys and Compounds》2006,420(1-2):29-33
The crystal and magnetic structures of the Laves phase compound NdCo2 in the temperature range from 9 to 300 K are determined by Rietveld refinement technique, using high-resolution neutron powder diffraction data. The compound crystallizes in space group above the magnetic ordering temperature TC (≈100 K), in space group I41/amd below TC and in space group Imma below the tetragonal–orthorhombic structural/magnetic transitions at TM ≈ 42 K. The assignment of the space groups to the crystal structures of NdCo2 in different temperature ranges complies with the reported Mössbauer studies. Detailed information of the crystal and magnetic structures of NdCo2 at different temperatures are reported. 相似文献
45.
Anshu Dubey Klaus Weide Dongwook Lee John Bachan Christopher Daley Samuel Olofin Noel Taylor Paul M. Rich Lynn B. Reid 《Software》2015,45(2):233-244
When developing a complex, multi‐authored code, daily testing on multiple platforms and under a variety of conditions is essential. It is therefore necessary to have a regression test suite that is easily administered and configured, as well as a way to easily view and interpret the test suite results. We describe the methodology for verification of FLASH, a highly capable multiphysics scientific application code with a wide user base. The methodology uses a combination of unit and regression tests and an in‐house testing software that is optimized for operation under limited resources. Although our practical implementations do not always comply with theoretical regression‐testing research, our methodology provides a comprehensive verification of a large scientific code under resource constraints.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
46.
This paper studies the adoption and diffusion of a cross-cultural Interorganizational Information System (IOS), which is used to streamline the processing of financial transactions between European investment fund companies and Taiwanese banks. Drawing from institutional and organizational legitimacy theory, we argue that the adoption and implementation of technological innovation is contingent upon its alignment with three institutional pillars in different countries and the deployment of legitimation strategies by stakeholders. Departing from classical innovation diffusion theory, our empirical investigation reveals that the implementation of a cross-cultural IOS is a dynamic process involving the recognition, understanding, and management of the regulative, normative, and cognitive challenges arising in two different institutional settings. This paper contributes to the growing body of research that highlights the significance of social and institutional influences on the adoption of IOS in a global environment. 相似文献
47.
Ella L. F. Fu Jan van Aalst Carol K. K. Chan 《International Journal of Computer-Supported Collaborative Learning》2016,11(4):441-478
The goal of this study was to develop a classification for a range of discourse patterns that occur in text-based asynchronous discussion forums, and that can aid in the distinction of three modes of discourse: knowledge sharing, knowledge construction, and knowledge building. The dataset was taken from Knowledge Forum® databases in the Knowledge Building Teacher Network in Hong Kong, and included three discussion views created for different classes: Grade 5 Science, Grade 10 Visual Arts, and Grade 10 Liberal Studies. We used a combination of qualitative coding and narrative analysis as well as teachers’ understanding of online discourse to analyze student discussions. Nine discourse patterns were identified. These patterns revealed a variety of ways in which students go about their collaborative interactions online and demonstrated how and why students succeed or fail in sustaining collaborative interactions. This study extended the three modes of online discourse and developed different discourse patterns, which are efforts to provide instructional guidance. The implications of supporting productive discourse and the enactment of CSCL innovations in classrooms are discussed. 相似文献
48.
Abstract A growing number of organizations are implementing the ITIL (IT Infrastructure Library) “best practice” framework in an attempt to improve their IT service management processes. However, not all ITIL implementations are successful and some companies have been disappointed with the outcomes. This exploratory research reports on four case studies of “successful” implementations of IT service management using the process-based ITIL V2 framework. Two companies are located in the U.S. and two in Australia. The cases demonstrate a mix of implementation justifications and strategies. Critical success factors (CSFs) suggested in the literature are compared against those attributed to these successful ITIL implementations. Some CSFs, including executive management support, interdepartmental communication and collaboration, use of consultants, training and careful software selection are confirmed. Three new CSFs are identified: creating an ITIL-friendly culture, process as a priority, and customer-focused metrics. Practitioner guidelines, to assist IT managers, who are contemplating adopting ITIL for process improvement and organisational transformation, are also provided together with some challenges encountered and their associated resolutions. 相似文献
49.
Rebecca C. Hedreen Jennifer L. Johnson Mack A. Lundy Peg Burnette Carol Perryman Guus Van Den Brekel 《国际互联网参考资料服务季刊》2013,18(2-3):167-195
ABSTRACT In April 2006, Alliance Library System and Online Programming for All Libraries partnered to start the Second Life Library 2.0 in the online world Second Life and in August 2006 purchased an island on the Teen grid of Teen Second Life. Second Life is a virtual world, a descendant of multiplayer online games. Educational institutions have recently been drawn into Second Life's robust economy and vibrant cultural life. The Second Life Library 2.0 works with librarians from around the world and with other educational partners such as TechSoup, WorldBridges, and the New Media Consortium. Second Life Library 2.0 provides “traditional” library services such as ready reference, book discussions, and search assistance, but, at heart, it explores what it means to be a virtual library in a virtual world. 相似文献
50.