1,720,966 research outputs found
Study of Min Protein-Induced Membrane Species Waves in vitro
No full text在大腸桿菌中，Min蛋白藉由在細胞兩極來回的動態振盪，能調控細胞分裂的位置。目前也已發現Min蛋白之自發性構成之動態波現象，可以藉由將Min蛋白中的MinD，MinE和腺苷三磷酸 (Adenosine triphosphate)(ATP)加入以大腸桿菌的細胞膜所形成之支撐式脂雙層膜平台，而在體外重現。然而，Min蛋白如何與大腸桿菌中的脂質雙層膜作用，以及如何影響到其它膜中生物分子之機制依舊不甚清楚。在本論文中，我們假設Min蛋白嵌入膜和離開膜之動態情況會影響脂質雙層膜外層脂質膜中頭基區域的空間密度，進而間接促使頭基較一般脂質分子為大之膜中生物分子，會較喜好填補頭基部分較為寬鬆的區域，因而在密度寬鬆的區域造成累積，而在密度較為緊緻的區域則有減少的現象，進而能產生其隨時間空間變化的濃度分佈。在本系統中，我們利用大腸桿菌的細胞膜所形成之支撐式脂質雙層膜來在體外重建生物體內的系統，並從大腸桿菌內純化出Min蛋白，來系統性地討論Min蛋白對脂質雙層膜之影響。我們觀察到脂質雙層膜在加入MinD，MinE和腺苷三磷酸後，會形成動態的螺旋濃度分佈波形。螢光漂白回復測試法和影像處理分析進一步指出脂質雙層膜上的濃度分佈動態波形與Min蛋白形成的表面波形有不同的特性，顯示膜中物質之濃度分佈並非源自於與Min蛋白有直接之鍵結。我們以帶有螢光分子的數種膜中物質作為生物分子模型，並將之鑲嵌進脂質雙層膜的系統，在加入Min蛋白後，的確發現Min蛋白的動態震盪現象只會影響頭基部分較大之膜中生物分子。此實驗觀察符合我們的假設: Min蛋白的動態現象會影響到脂質雙層膜上的生物分子，並可能具有選擇性的影響特定生物分子。此結果也提供了一個 Min蛋白如何與其他膜中分子作用的可能機制。In the bacterium Escherichia coli, the proper placement of the division site selection is regulated in part by the pole-to-pole oscillations of Min proteins. The oscillation dynamics emerges from the self-organization of MinD, MinE and ATP in vivo, which also forms planar surface waves on supported lipid bilayer in vitro. However, it is still unclear how the Min proteins affect the E. coli lipid membrane and interact with the other E. coli membrane proteins, even though how Min proteins interact with the membrane surface to generate the in vivo oscillations is a subject of intense study. We hypothesized that the spatial oscillations of Min protein systems could play a crucial role in changing lipid membrane dynamics and therefore indirectly influence the dynamics of other membrane associated species. We reconstituted the system on supported E. coli lipid bilayer platforms in order to systematically explore the underlying mechanism between lipid membranes and Min proteins. We observed fluorescently labeled lipids in the E. coli membranes moving in spiral waves after the addition of unlabeled MinD, MinE and ATP to the membranes. Fluorescence recovery after photobleaching (FRAP) and kymograph analyses showed that dynamics of the labeled lipid membrane waves had different characteristics from those of the Min protein waves. In the future, some E. coli signaling membrane proteins could be incorporated into the membrane to examine whether their movement or clustering can be influenced by the Min proteins-induced membrane waves. The result could provide us insights into the long-standing question about other possible function of the E. coli Min protein oscillation phenomenon
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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