臺灣博碩士論文加值系統

在醫療診斷，化學以及材料科學領域，核磁共振成像(Magnetic Resonance Imaging, MRI)已經是一項十分重要的工具。為了進一步提升影像的選擇性以及解析度，各種適用於MRI的順磁性造影劑已陸續被開發。造影劑的基本原理是利用順磁離子與水上的質子之間的磁偶極作用增加位於順磁性離子附近的水分子之鬆弛，使得特定部位的影像對比度增加。造影劑的效能不僅與其分子結構和動力學有關，同時也取決於造影劑分子所位處的環境。在典型的生物系統裡面，所注射的造影劑是位處於一個擁擠環境裡，然而，一直以來皆無擁擠效應對於造影劑鬆弛的影響之相關研究。在本工作中，我們使用最常用的醫用MRI造影劑Dotarem以及幾種不同的高分子當作擁擠分子，首次對造影劑鬆弛中的擁擠效應進行探討。我們選用polyethylene glycol(PEG)和bovine serum albumin (BSA)作為擁擠分子模擬生物系統內的擁擠環境。Dotarem濃度範圍在0─40 mM,高分子溶液濃度範圍在0％─40％w/w。實驗方法包括NMR縱向鬆弛速率R1測量（200 MHz），T1和T2加權微影像(500 MHz)以及快速場循環鬆弛測量（0─100 MHz）。恆定場及變場1H NMR鬆弛及加權影像實驗結果都證明，PEG和BSA均表現出明顯的擁擠效應。R1值和造影劑濃度呈預期的線性關係，但也發現在固定造影劑濃度下，R1值和PEG/BSA濃度呈現非線性關係，推測是由於水溶液結構改變(高濃度PEG/BSA水溶液中水分子傾向趨近PEG/BSA表面)、水溶液黏滯性變化與體積排除效應三者共同造成。另外，R1與PEG的大小基本上無關，我們認為這是由於PEG沒有固定的二級結構所致。這些結果也表明PEG，BSA水溶液的複雜性。PEG與BSA水溶液對造影劑鬆弛的影響之差異表明擁擠分子的結構是影響擁擠效應的一個重要參數。

摘要 .Ⅰ
目錄 Ⅱ
圖目錄 Ⅳ
表目錄 VI
第一章 核磁共振簡介 1
1.1 基礎NMR原理 1
1.2 磁通量(The nuclear magnetic moment) 2
1.3 鬆弛常數T1和T2的介紹 4
1.3.1縱向鬆弛( longitudinal relaxation ) 4
1.3.2橫向鬆弛( transverse relaxation ) 5
1.4 MRI作用原理 7
第二章 造影劑簡介 10
2.1 MRI之對比與MRI造影劑的關係 10
2.2造影劑在MRI的實際應用 11
2.2.1造影劑的鬆弛作用機制 11
2.2.2有關內層鬆弛( Inner-Sphere Relaxation)的作用機制 13
2.2.3有關外層鬆弛(Outer-Sphere Relaxation)的作用機制 14
2.2.4有關內外層之水分子交換鬆弛( Exchange Relaxation)的作用機制 14
第三章 擁擠效應簡介 15
3.1 何謂擁擠效應(Crowding effect)和侷限效應(Confinement effect) 15
3.2 擁擠試劑與人體的關係 16
3.3 擁擠效應對於細胞內環境所造成的影響 17
3.4 擁擠效應影響酶的催化活性的例子 18
3.5 擁擠效應對於蛋白質摺疊 (Crowding effect on protein folding/ unfolding) 的預測 18
3.6 關於擁擠效應的基本文獻之回顧 19
3.7 NMR研究擁擠效應的工作回顧 19
3.8 體積排除作用的種類型式 21
3.9 針對擁擠效應和侷限效應所發展的熱力學分析模型架構 21
3.9.1擁擠效應和侷限效應主要影響下列三種典型的生理反應 21
3.9.2擁擠(Crowding) 23
3.9.2.1 的估計值 23
3.9.2.2締合作用的平衡常數(Association equilibria ) 24
3.9.2.3締合作用速率(Association rates) 24
3.9.2.4位置-鍵結反應之平衡(Site-binding equilibria) 25
3.9.2.5蛋白質兩態折疊的平衡(Two-state protein folding equilibria) 25
3.10研究動機 26
第四章 實驗部分 28
4.1實驗儀器設備 28
4.2實驗樣品 28
4.2.1有關所使用的造影劑之資訊 28
4.2.2關於PEG(聚乙烯甘醇) 29
4.2.3 BSA (Bovine serum albumin) 之基本性質與胺基酸序列 29
4.3樣品製備(含有對比劑以及高分子的液態混合溶液) 30
4.3.1所使用的造影劑種類與濃度 30
4.3.2擁擠試劑的種類與濃度 30
4.3.3配製步驟 30
4.4實驗參數 32
第五章 結果與討論 34
5.1不同對比劑濃度之PEG水溶液1H-T1研究 34
5.2固定相同造影劑濃度下高分子濃度與縱向鬆弛速率的關係之物理模型 38
5.3固定相同造影劑濃度下高分子濃度與縱向鬆弛速率的關係 41
5.4 PEG與BSA在固定造影劑濃度下的鬆弛速率比較 42
5.5不同尺寸的高分子在固定造影劑濃度下的鬆弛速率比較 43
5.6不同尺寸的PEG水溶液中擁擠效應對造影劑鬆弛的影響 44
5.7 利用PEG水溶液之氫核NMR研究，研究擁擠效應對於造影劑鬆弛所帶來的影響之3D圖. 45
5.8 影像實驗結果 48
5.9鬆弛分散(NMRD)結果 50
第六章 結論部分 53
參考文獻 54

圖目錄
圖1.1.1 一個旋轉的核自旋視為一個微型磁鐵之示意圖 1
圖1.1.2 在外加磁場B0下磁通量為μ的核自旋之進動與陀螺儀示意圖 2
圖1.2.1 I=1/2的核自旋在Zeeman分裂前後的關係圖 4
圖1.3.1.1 測量T1的過程示意圖 5
圖1.3.2.1 測量T2的過程示意圖. 6
圖1.4.1各個切片方位的微影像切面圖 8
圖2.2.2.1 MRI造影劑的鬆弛機制示意圖 11
圖3.1.1 擁擠效應和侷限效應示意圖 15
圖3.9.1.1 稀釋溶液和擁擠溶液的自由能變化示意圖 23
圖5.1.1不同濃度之PEG 200水峰鬆弛速率與對比劑濃度關係圖 35
圖5.1.2不同濃度之PEG 2000水峰鬆弛速率與對比劑濃度關係圖 35
圖5.1.3不同濃度之PEG 6000水峰鬆弛速率與對比劑濃度關係圖 36
圖5.1.4不同濃度之PEG 10000水峰鬆弛速率與對比劑濃度關係圖 36
圖5.1.5不同濃度之PEG 20000水峰鬆弛速率與對比劑濃度關係圖 37
圖5.1.6不同濃度之BSA水峰鬆弛速率與對比劑濃度關係圖 37
圖5.2.1固定對比劑濃度下PEG200水溶液之水峰R1與PEG濃度的關係圖 38
圖5.2.2固定對比劑濃度下PEG2000水溶液之水峰R1與PEG濃度的關係圖 39
圖5.2.3固定對比劑濃度下PEG6000水溶液之水峰R1與PEG濃度的關係圖 39
圖5.2.4固定對比劑濃度下PEG10000水溶液之水峰R1與PEG濃度的關係圖 40
圖5.2.5固定對比劑濃度下PEG20000水溶液之水峰R1與PEG濃度的關係圖 40
圖5.2.6固定對比劑濃度下BSA水溶液之水峰R1與BSA濃度的關係圖 41
圖5.3.1固定相同造影劑濃度下，低濃度及高濃度之相同種類高分子溶液之物理
模型圖 41
圖5.4.1 PEG6000與BSA在固定造影劑濃度下，隨著高分子濃度不同，其鬆弛速
率變化情形之比較圖 43
圖5.5.1不同尺寸PEG與BSA在固定造影劑濃度下，隨著高分子濃度不同，其
鬆弛速率變化情形之比較圖 44
圖5.6.1不同尺寸下的PEG水溶液之物理模型圖 44
圖5.7.1 PEG 200-水峰-3D圖 45
圖5.7.2 PEG 2000-水峰-3D圖 45
圖5.7.3 PEG 6000-水峰-3D圖 46
圖5.7.4 PEG 10000-水峰-3D圖 46
圖5.7.5 PEG 20000-水峰-3D圖 47
圖5.7.6 BSA-水峰-3D圖 47
圖5.8.1不同造影劑濃度下之5% PEG6000水溶液之MRI圖 49
圖5.8.2 5%PEG水溶液之毛細管內所含造影劑濃度示意圖 49
圖5.8.3不同造影劑濃度下之20% PEG6000水溶液之MRI圖 49
圖5.8.4 20%PEG水溶液之毛細管內所含造影劑濃度示意圖 49
圖5.8.5不同造影劑濃度下之30% PEG6000水溶液之MRI圖 50
圖5.8.6 30%PEG水溶液之毛細管內所含造影劑濃度示意圖 50
圖5.8.7不同造影劑濃度下之40% PEG6000水溶液之MRI圖 50
圖5.8.8 40%PEG水溶液之毛細管內所含造影劑濃度示意圖 50
圖5.9.1 5%BSA與四個濃度Gd-DOTA水溶液的1H的NMRD (0-100 MHz)在兩個不同溫度下的結果 51
表目錄
表4.2.1有關所使用的造影劑之資訊 28
表5.1.1 PEG 6000水溶液水峰之R1實驗結果 34

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