1,721,054 research outputs found
Identification and Functional Study of Plastidial Starch Phosphorylase Interacting Protein Complexes in Sweet Potato Roots
No full text蛋白質的轉譯後修飾調控了許多重要的生理機制。早期研究顯示質體型澱粉磷解酶 (L-SP) 可能受到蛋白質降解性後修飾作用所調控。本實驗室在純化L-SP的過程中，發現一高分子量、且具有L-SP活性之色帶 (簡稱HX)。本論文進一步利用免疫共沉澱與免疫螢光組織定位等方法，證明HX由L-SP與20S proteasome所組成。並且在45°C熱處理下，HX會立即消失，可觀察到L-SP隨著熱處理的時間增加，發生階段性降解的現象，這個降解作用可隨著20 proteasome的活性受到proteasome專一性抑制劑 (MG132) 的抑制，而減緩L-SP之降解，顯示20S proteasome可能參與此降解作用。以酵素動力學分析降解前後L-SP之生化性質差異，發現降解後的L-SP對於Glc-1-P的親和力下降，進而降低澱粉合成方向的活性。因此我們推測20S proteasome可能會受到熱逆境的刺激，進而以降解機制修飾L-SP，來調控L-SP催化方向之活性。
另一方面，以L-SP單株抗體進行免疫共沉澱時，意外地發現一個分子量約65 kDa的蛋白質可能也與L-SP互相結合；經LC-MS/MS定序，此蛋白質為DPE1 (D-enzyme, disproportionating enzyme, 4-alpha-glucanotransferase; EC 2.4.1.25)。DPE1催化可逆性的 alpha-1,4鏈結葡聚醣之裂解與轉移反應，改變寡糖之鏈長分布。過去的研究顯示，在E coli中，malQ (DPE1同源基因) 和malP (L-SP同源基因) 位於相同的malA操作組，故推測兩者有類似的功能，可能共同作用。進一步，本論文以二維電泳 (native PAGE/SDS-PAGE)、GST pull-down assay、以及FRET-confocal microscopy為工具，證明L-SP與DPE1互相結合，形成蛋白質複合體 (SP-DPE complexes)。此外，膠體過濾法與二維電泳之結果顯示，SP-DPE complexes可能是由四個L-SP單元體與四個DPE1單元體，結合為一個分子量約為700 kDa之蛋白質複合體。以酵素動力學比較SP-DPE complexes與DPE1之間的差異，顯示SP-DPE complexes對於麥芽三糖 (maltotriose) 具有較高的親和力，而對於麥芽四糖 (maltotetraose) 則有較高的催化效率；而在SP-DPE complexes的酵素催化作用中，則觀察到基質快速轉移的現象。另外SP-DPE complexes在直徑15-20 mm大小之甘藷塊根中含量最多，顯示其與澱粉快速累積有重要的關聯性。這部份的結果顯示，在甘藷塊根的造粉體中，L-SP與DPE1可能形成蛋白質複合體，以幫助澱粉的快速累積，其生理作用可能扮演有效地回收再利用短鏈麥芽寡糖，或直接作用在短鏈分支之澱粉結構中，正確決定澱粉的結構。Post-translational regulation plays an important role in cellular metabolism. Earlier studies showed that the activity of plastidal starch phosphorylase (L-SP) may be regulated by proteolytic modification. During the purification of L-SP from sweet potato roots, an unknown high molecular weight complex (HX) showing L-SP activity was constantly observed. Its mobility was significantly slower than the typical L-SP on native PAGE. We utilized mass spectrometry, coimmunoprecipitation, Ouchterlony double immunodiffusion, two-dimensional gel electrophoresis, and confocal microscopy as tools to demonstrate that HX was composed of L-SP and the 20S proteasome. Furthermore, we found that the amount of HX decreased immediately after 45°C heat treatment, which caused stepwise degradation of L-SP in a time-dependent mode. This degradation process was strongly inhibited by MG132, suggesting that the 20S proteasome might be involved in L-SP degradation. In addition, kinetic studies indicated that the proteolytic modification of L-SP caused it to decrease the binding affinity toward Glc-1-P and subsequently reduced its starch-synthesizing activity. This work demonstrates the role of the 20S proteasome as a regulator of L-SP activity, which may be controlled by stressful condition.
On the other hand, immunoprecipitation experiments with L-SP mAbs showed that another protein might associate with L-SP. This protein was identified as DPE1 (D-enzyme, disproportionating enzyme, 4-alpha-glucanotransferase; EC 2.4.1.25) by LC/MS/MS. DPE1 catalyses the cleavage and transfer reactions involving alpha-1,4 linked glucans and alters the chain length distribution of oligosaccharides. Previous studies suggested that DPE1 might work in conjunction with L-SP. Furthermore, we utilized 2-DE (native PAGE/SDS-PAGE), GST pull-down assay, and confocal microscopy as tools to demonstrate that L-SP might interact with DPE1, suggesting that these enzymes may form protein complexes (SP-DPE complexes). The results from gel-filtration chromatography and 2-DE (native PAGE/SDS-PAGE) indicated that SP-DPE complexes might be composed of four L-SP subunits and four DPE1 subunits with molecular weight around 700 kDa. In addition, protein complex forms of DPE1 showed a higher affinity toward maltotriose and a higher catalytic activity toward maltotetraose than DPE1 monomers. The efficient passage of the product of one enzyme to the next enzyme in SP-DPE complexes was also be observed. Moreover, the protein levels of SP-DPE complexes were shown to become higher in the middle stage of sweet potato root development where starch accumulated fast. These results suggest that SP-DPE complexes may either efficiently recycle short chain malto-oligosaccharides to produce Glc-1-P for starch synthesis, or may specifically edit short-chain amylopectin, thus resulting in the formation of correct starch structure
BUSINESS MODEL & VIABILITY ANALYSIS FOR PURE-PLAY INTERNET STARTUPS?- CASE OF A TRAVEL WEBSITE
No full textTaiwan, an island of innovation and technology, is famous for its entrepreneurial spirit and high efficient small-and-middle business. Transforming from a manufacturing-oriented OEM empire to a service-oriented design center, Taiwan has begun to position itself in the software industry in recent years, and many entrepreneurs in Taiwan have chosen the Internet as their new venture field. These Internet entrepreneurs believe that the entry barrier of the Internet startup has reached its lowest level like never before.
This paper intends to develop an optimistic approach of business model pivot for the Internet startups in terms of higher viability. Based on the sources of revenue, the three major pure-play Internet business models (market maker, audience maker, and demand coordinator) will first be introduced. On top of that, the elements of viability will be analyzed through out a customer’s lifecycle (acquisition, conversion, and retention.) According to the prior studies mentioned in this paper, an Internet startup can possibly become more viable by pivoting its business model.
Therefore, conclusively, a proposition of business model pivot for higher viability is induced from the three pure-play Internet business model analysis with the correlated viability factors. This paper suggests to start with the market maker model and prepare for the demand coordinator business for the later phase. Meanwhile, grow the audience maker business steadily in parallel because the return of the audience maker business will not be realized until the user base has reached its commercial advertising value in the long run. For better understanding, the proposition will later be applied to a fledgling travel website as an example. In the end, the derived business development roadmap for the travel website case will be examined by some external consultants. For further studies, this paper suggests the topics: consumer psychology, and the scalability
Improved Design and Fabrication of Titanium Diffused Lithium Niobate Multimode Interference Power Splitters
No full text本論文之目的在探討改良式1×4鈦擴散鈮酸鋰多模干涉分光器。改良方式有採用二階式干涉區與外加電極於干涉區等兩種。
第一種多模干涉分光器係將傳統式多模干涉區適當裁剪而成。為評估元件改良效果，本文提出一改良參數作為評估標準。經適當設計二階式干涉區後，傳輸率可提升至80.5%，耦合長度可縮短至2250μm，改良參數可提高16%。
第二種多模干涉器係利用電光調變性質將干涉區前1/3段外加電壓0至60V，發現在耦合長度2250μm時，可提升傳輸率5.4%，同時內側與外側輸出波導功率比值可調變幅度為0.74至1.58，可作為可調式分光器之用。Two types of improved 1×4 titanium diffused lithium niobate multimode interference (MMI) power splitters are proposed. The first MMI has an interference region of two stages adjusted to enhance an improvement factor. The second one has an interference region with deposited electrodes.
The first type MMI power splitter is obtained by an appropriate cutting of the interference region. For performance evaluation of proposed device, an improvement factor is proposed. The two-stage MMI power splitter has a higher transmission of 80.5% and a shorter coupling length of 2250μm. The improvement factor is increased by 16%.
For the second type of MMI power splitter, a voltage varying from 0 to 60V is applied on the first one-third of the interference region for electro-optic modulation. The results show when the coupling length is 2250μm, transmission can be increased by 5.4%, and the power ratio of inner output waveguide and outer output waveguide is varying from 0.74 to 1.58, which can be used as tunable power splitter for practical application
An Empirical Analysis of Structural Models for Corporate Bond Pricing
No full textChang (2012) 指出，在Collin-Dufresne and Goldstein (2001) 公司債定價模型的基礎上，再加入Amin (1993) 之跳躍擴散樹狀模型之後，可解決現有結構式模型容易低估信用價差 (Credit Spread) 的先天缺陷，同時在採用回溯推算過程之下，此模型甚至可計算如可贖回債券 (callable bond)、信用違約交換 (Credit Default Swap) 等其他金融商品。而本研究針對其模型計算公司債之部分，與另外五個具代表性之結構式定價模型進行實證分析與比較，其包含：Merton (1974)、Geske (1977)、Longstaff and Schwartz (1995)、Leland and Toft (1996)、以及Collin-Dufresne and Goldstein (2001)。
資料方面，本研究選出數張符合模型設定標準，於2002至2007年於美國發行之純含息債券作為實證樣本，並與評價日之市價隱含信用價差進行比較。
全文內容主要以跳躍擴散樹狀模型及其他結構式模型之建構為主，其中包含前人文獻之細節回顧與模型參數之估計方式等。次之，則以實證資料之計算結果作為搭配，以驗證此跳躍擴散樹狀模型對於過去結構式模型缺陷之改良程度。This thesis conducts an empirical analysis for corporate bond prices and their credit spreads with several classical structural models. Following Eom, Helwege, and Huang (2004), I examine the models of Merton (1974), Geske (1977), Longstaff and Schwartz (1995), Leland and Toft (1996), and Collin-Dufresne and Goldstein (2001). Moreover, according to Chang (2012), the underestimation of the credit spread based on Collin-Dufresne and Goldstein’s (2001) stationary leverage structural model can be resolved by incorporating the jump process into their stationary leverage stochastic process. Therefore, this thesis also examines this new structural model based on the stationary leverage ratio with jumps. Following the criteria proposed in Eom, Helwege, and Huang (2004) to screen corporate bonds, I obtain several corporate bonds issued between 2002 and 2007 in the U.S. as the study sample to investigate the performance of the above-mentioned six structural models for evaluating the bond prices and their credit spreads.誌 謝 i
摘 要 ii
Abstract iii
目 錄 iv
圖目錄 vi
表目錄 vii
第一章 緒論 1
第一節 研究背景 1
第二節 研究架構 2
第三節 全文架構 3
第二章 文獻回顧 4
第一節 Merton (1974) M模型 5
第二節 Geske (1977) G模型 6
第三節 Longstaff and Schwartz (1995) LS模型 8
第四節 Leland and Toft (1996) LT模型 10
第五節 Collin-Dufresne and Goldstein (2001) CDG模型 12
第六節 Chang (2012) CDGtree模型 15
第七節 CDGtree模型與CDG模型之數據模擬與比較 23
第三章 參數估計與實證結果 30
第一節 資料選取及數據來源 30
第二節 模型參數估計 31
第三節 實證結果 44
第四章 結論 54
References 56
Appendix A 58
Vasicek (1977) V模型 58
Hull and White (1994) HW模型 59
Appendix B 6
Effect of natural organic matter on the formation and consumption of OH radical and removal of emerging contaminants in ozonation
No full text臭氧被廣泛應用於去除自來水和廢水中的有機污染物，近幾年來更是運用於降解地表水及地下水中之新興污染物。由於天然有機物(NOM)與臭氧及氫氧自由基的反應相當複雜，所以天然有機物在臭氧處理程序中之影響尚未被闡明。故本研究的目的為：(1)測定天然有機物於臭氧處理程序中起始反應(initiation)、促進反應(promotion)、抑制反應(inhibition)以及與臭氧直接反應之速率常數。(2) 探討pH值及溫度對起始反應、促進反應、抑制反應以及與臭氧直接反應速率常數之影響。(3) 測定及模擬天然有機物於臭氧處理程序中對新興污染物去除之影響。本研究所使用之四種自然水體為：新店溪(新北市)、宜蘭河(宜蘭市)、金沙水庫(金門縣)及台中地下水(台中縣)。結果顯示起始反應、抑制反應及與臭氧的直接反應之速率常數會隨著pH值升高而增加，但促進反應之速率常數則明顯的趨勢。在溫度影響的部分，所有的速率常數皆是隨著溫度的升高而增加。在天然有機物於臭氧處理程序下對新興污染物降解影響的部分，從結果顯示都可利用所測得之速率常數得到良好的預測結果。Ozonation has been widely used for removing organic contaminants in water treatment. The effect of natural organic matter (NOM) on this process, however, is not well understood due to the complex reactions of NOM with ozone and •OH generated from ozone decomposition. The objectives of this study are to determine the rate constants of NOM from different sources in terms of initiation, promotion, inhibition and direct ozone reactions in the ozonation process and to investigate the influences of NOM on the removal of emerging contaminants. The rate constants of NOM in four natural waters including Hsintien river (New Taipei City), Yilan river (Yilan City), Jinsha reservoir (Kinmen County) and Taichung groundwater (Taichung County) were determined using a recently developed approach that integrates the pseudo first order ozone decomposition kinetics, transient steady state •OH concentration and the Rct concept. The effects of pH value and temperature on the rate constants were also determined. With these rate constants, the influences of NOM on the degradation of three emerging contaminants including ibuprofen, acetylsulfamethoxazole and metoprolol can be fairly well predicted
The Establishment Of Rheum palmatum L. Hairy Root Culture And The Production Of Anthraquinone By The Culture Thereof
No full text利用農桿根群菌(Agrobacterium rhizogenes) A4 野生型菌株感染掌葉大黃外植體誘導毛狀根以建立掌葉大黃毛狀根的培養系統，再經由PCR方法進行確認。檢討該毛狀根之最適培養基組成，並且檢討擴大培養之最適培養條件。分別利用比色法、薄層層析法和高效能液相層析法分析毛狀根中游離蒽醌化合物的含量。
本研究以大黃酸作為標準品，在搖瓶培養中測試其最適培養基組成。由實驗結果得知，以B5培養基含2%蔗糖、20.25 mM硝酸鉀、6.75 mM硫酸銨和0.75 mM磷酸二氫鈉為最適培養基組成分。利用最適化之B5培養基進行掌葉大黃毛狀根的培養，培養42天後可得到最高大黃酸產量10.06 mg/L，與搖瓶培養所得之7.264 ± 0.06 mg/L相比較，大黃酸產量增加了1.38倍。擴大培養係利用1公升之氣泡塔式生物反應器(Bubble column reactor)，以B5培養基為基礎培養基培養49 天，可得到的大黃酸產量為17.245 mg/L，與搖瓶培養所得之7.264 ± 0.06 mg/L相比較，大黃酸產量增加了2.37倍。Culture of Rheum palmatum L. hairy roots were established after transformation with Agrobacterium rhizogenese A4, and the transformation was confirmed by PCR for the presence of a T-DNA sequence in their genomes. Quantitative determination of anthraquinones were performed by colorimetry, thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Among these anthraquinones produced by Rheum palmatum L., emodin and rhein were considered more important. In the studies, rhein is taken as the reference standard. Root growth and production of rhein were investigated in various basal media. It was found that B5 medium was superior to MS medium in terms of both root growth and rhein production. The results indicate that Rheum palmatum L. hairy root can be cultivated in the B5 medium enriched with 2 % sucrose, 20.25 mM KNO3, 6.75 mM NH4NO3 and 0.75 mM NaH2PO4. The rhein production is 10.06 mg/L in a 42 days` culture. The productivity is 1.38 folds as that in normal flask culture. A scale up culture of Rheum palmatum L. hairy root from 125 mL flask to 1 L bubble column reactor was conducted. The rhein production is 17.245 mg/L in a 49 days` culture. The productivity is 2.37 folds as that in flask culture.中文摘要………………………………………………………………Ⅰ
英文摘要………………………………………………………………Ⅱ
目錄……………………………………………………………………Ⅲ
表次……………………………………………………………………Ⅴ
圖次……………………………………………………………………Ⅵ
第一章 前言…………………………………………………………1
第一節 掌葉大黃…………………………………………………1
第二節 掌葉大黃有效成份之介紹………………………………6
第三節 植物二次代謝物…………………………………………8
第四節 毛狀根……………………………………………………13
第五節 研究目的…………………………………………………28
第二章 材料與方法…………………………………………………29
第一節 掌葉大黃無菌植株………………………………………29
第二節 掌葉大黃毛狀根系統的建立……………………………32
第三節 掌葉大黃毛狀根系統的確認……………………………34
第四節 掌葉大黃毛狀根及其培養液之分析……………………36
第五節 培養基組成之最適化探討………………………………39
第六節 生物反應器之培養………………………………………40
第七節 實驗儀器…………………………………………………41
第三章 結果與討論…………………………………………………43
第一節 掌葉大黃無菌植株………………………………………43
第二節 掌葉大黃毛狀根系統的建立……………………………44
第三節 掌葉大黃毛狀根系統的確認……………………………48
第四節 掌葉大黃毛狀根及其培養液之分析……………………50
第五節 培養基組成之最適化探討………………………………56
第六節 生物反應器之培養………………………………………78
第四章 結論………………………………………………………… 85
參考資料………………………………………………………………8
Hairy Root Cultures of Gynostemma pentaphyllum (Thunb.) Makino: A Promising Approach for the Production of Gypenosides as an Alternative of Ginseng Saponins
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Synthesis of nonuniformly spaced linear array for GSM/DCS/WCDMA base station application using genetic algorithm
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