1,720,985 research outputs found
Purification of Carica papaya Seed Lectin by Affinity Chromatography
No full text凝集素(Lectin)為一類具有選擇性辨識特定醣類分子的蛋白質或醣蛋白，具有多種生理功能，如調控細胞分化、細胞附著、免疫反應等。近年來，廣泛作為研究醣生物學的分析工具，且發現凝集素有抗癌與免疫調節等生理機能。本實驗室先前的研究結果顯示，由番木瓜(Carica papaya LINN.)種籽中具有對於N-acetyl-D-galactosamine (GalNAc) 有良好親和性的凝集素蛋白─ C. papaya lectin (CPL)，並進行部分生化特性分析，顯示CPL 可以刺激Jurkat 細胞分泌IL-2，具有調節免疫細胞活性的潛力。但是，CPL分離純化步驟繁多且回收量率低，故本研究使用自行衍生製備的膠體lactose-Sepharose 6B (LS6B)及 GalNAc-Sepharose 6B (GS6B)，經由改變管柱順序與流洗條件，並搭配凝血活性追蹤，建立一套高效率的純化方法。研究顯示，此兩階段的親和性管柱層析：先通入LS6B，再通入GS6B管柱，接續分別以0.5 M 乳糖溶液、0.1 M GalNAc溶液流洗。其中，GalNAc溶液可流洗出滯留於GS6B管柱上的具凝血活性之蛋白，膠體過濾管柱分析結果顯示該蛋白即為CPL。與先前本研究室文獻報告的數據比較，以兩階段親和性管柱層析確實能有效純化CPL的比活性及提高其回收率。另一方面，以乳糖溶液洗出的區分液蛋白(簡稱LpGLac)，無論在血球凝集試驗或ELISA的結果都不具有醣類結合能力，可見其並非一類新的凝集素，目前推測LpGLac是藉由蛋白上所鍵結的醣基片段能為CPL所辨識、結合，而被滯留於親和性管柱上。此外，本研究亦將純化所得之具凝血活性的區分液及LpGLac處理小鼠巨噬細胞，結果顯示兩者皆能夠誘發巨噬細胞分泌促發炎細胞激素(pro-inflammatory cytokines)，具有免疫調節活性。Lectins are defined as sugar-binding and cell-agglutinating proteins of non-immune origin. They are ubiquitous in nature, being found in all kinds of organisms, from viruses to humans. Recently, our group isolated an N-Acetyl-D-galactosamine (GalNAc)-specific lectin from the seeds of papaya (Carica papaya), named CPL. In this study, an effective affinity chromatographic method for CPL isolation and purification was established, based on the specificity of CPL. By using two steps affinity chromatography through lactose-Sepharose 6B and GalNAc-Sepharose 6B resins, with sequential elution by lactose and GalNAc solution. The hemagglutination activity of GalNAc-elution fractions (LpGLac-GalNAc) was 1461 fold higher than original papaya seed crude extracts. Through the gel filtration chromatography, the results showed that the purified CPL was appeared in LpGLac-GalNAc; also, this purification protocol obtained higher purity and higher protein yield of CPL than previous research (Wang et al., 2011). At the same time, we discovered a lactose desorbed protein, designed as LpGLac, in the process of affinity purification. The results of SDS-PAGE, hemagglutination assay and ELISA assay indicated that LpGLac was recognized by CPL and might compete with lactose for carbohydrate binding domain on CPL, which resulted in desorbing from affinity column by lactose solution. In addition, we investigated the immunomodulatory effects of purified protein on murine macrophages RAW 264.7 cell line in vitro. Incubation of LpGLac and LpGLac-GalNAc with RAW cells showed significant induction of pro-inflammatory cytokines, IL-6 and TNF-α, as well as nitric oxide, which suggests that both of purified proteins have potent immunomodulatory effects on immune cells
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
Time-domain compensation for closed-loop systems by a delay line method
Get PDF"January 17, 1955." "This report is based on a thesis submitted to the Department of Electrical Engineering, M.I.T., ... for the degree of Master of Science."Bibliography: p. 33.Army Signal Corps Contract DA36-039 sc-42607 Project 132B Dept. of the Army Project 3-99-12-022Yu-Chi Ho
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
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