以原子力顯微鏡(AFM)於氣相及液相環境觀察環圈形並已知鹼基對數目的質體DNA(pQE70)，在緩衝溶液中控制離子鹽濃度輔以加熱或適當鬆弛試劑可消除DNA的聚集和摺疊，而在平坦的雲母基板掃描到環圈狀的DNA影像，由高度及寬度的分析，確認為單一的DNA分子。氣相AFM所測量到的pQE70長度(contour length)與B型DNA一致，但在異丙醇掃描介質中測量長度增長為B型的2.4倍之多。探討化學修飾對於雲母表面固定DNA能力的改善情形，比較利用醋酸鎂、氯化鋇和3-aminopropyl-triethoxysilane(APTES)改變表面電性後對DNA吸附及成像之效果。針對單股及雙股噬菌體DNA(M13mp18)作影像比對，發現兩者在AFM解析度限制下具有可茲辨識的特徵。

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摘要 i
目錄 ii
圖表目錄 v

第壹章、緒論 1
1-1研究背景 1
1-2核酸 1
1-3 DNA的拓樸結構 6
1-4原子力顯微鏡 7
原子力顯微鏡之探針 8
原子力顯微鏡在生物學上的應用 10
原子力顯微鏡在生物學應用上的優缺點 11
研究動機 12
第貳章、實驗 14
2-1實驗儀器 14
2-2原子力顯微鏡原理 14
2-2-1 Contact mode(接觸模式) 16
2-2-2 Tapping mode(輕敲模式) 17
2-2-3液相掃描 18
液相AFM的操作步驟 18
調整探針共振頻率與振幅 20
2-2-4原子力顯微鏡偵測模式與探針選擇 22
2-3材料 24
2-3-1<a>基板 24
<b>樣品 24
<c>樣品配製的生物緩衝液及濃度 24
<d>AFM的Liquid Cell中液相環境中所使用的溶液 24
2-4實驗操作方法 29
2-4-1方法簡介 29
2-4-2實驗流程 30
2-4-3樣品配製 31
滅菌水 31
醋酸鎂將Mica表面修飾成帶正電的Mica-Mg(II) 31
以BaCl2將Mica表面修飾成帶正電的Mica-Ba(II) 32
AP-mica的製備 32
2-4-4 Q & A 34
第參章、結果與討論 36
3-1雲母基板(Mica substrate) 36
3-2氣相AFM觀察雲母基板上的DNA分子 37
3-3環圈狀DNA的長度測量 43
3-4液相AFM觀察雲母基板上的DNA分子 45
3-5利用化學試劑使纏繞的DNA鬆弛 49
3-5-1 以formamide 作為DNA鬆弛試劑 49
3-5-2 以ammonium acetate作為鬆弛試劑 52
3-6液相AFM所觀察到環圈狀DNA長度 53
3-7將雲母修飾成帶正電的表面 59
3-8 DNA超螺旋 64
3-9單股及雙股噬菌體DNA 65
3-9-1單股M13mp18 DNA 66
3-9-2雙股M13mp18 DNA 67
第肆章、結論 71
參考文獻 74

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