臺灣博碩士論文加值系統

摘要
我們利用原子力顯微鏡(AFM)觀察脂質單層膜在雲母片上的熱行為。磷脂質是構成生物膜的主要成份，它主要是由極性端-親水性和非極性端-疏水性(碳氫鍵)構成。由於這個同時具有親水和疏水性質，使得脂質分子在一個親水的基板(如：實驗中所使用的雲母片)上可以自動排列成一個很均勻平整的薄膜。因此若利用微影技術在膜表面做一些結構或者在膜表面鍍上奈米金屬粒子，脂質膜應該是一個好的材料，故脂質膜熱行為對未來的應用上更顯得重要。我們的研究主要利用加溫脂質膜來觀察脂質膜在加溫過程的各種不同情況，以了解脂質分子的熱行為。
我們利用AFM的加熱裝置以每秒2℃~4℃的速率加熱與冷卻脂質單層膜，藉此觀察脂質膜在不同溫度的各種情況。最後，我們發現脂質單層膜在45℃~50℃時開始從二維(2D)凝聚態轉變成二維氣態(液態)與凝聚態共存態，在60℃~68℃轉變成二維氣態(液態)。此外，這個相變過程是可逆性的。最後，我們得到一個結論就是了解到脂質膜的熱行為是一個從二維凝聚態轉變成二維氣態(液態)的相變過程。

Abstract
We observed the thermal behaviour of single phospholipid layers on mica by using atomic force microscopy (AFM). It has been known that lipids are integral components of all biological membranes and phospholipids have polar head groups and long fatty acid chains which give rise to amphipathic properties --- that is, they have a hydrophilic（” water-loving ”）or polar end and a hydrophobic（” water-fearing ”） or non polar end. The property of phospholipids allows themselves to assemble into extremely uniform thin films spontaneously. Therefore, the lipid thin films are great materials for lithography, nano-materials supports as well as applications requiring quality thin films. That implies that thermal properties of the lipid thin films would be very crucial for future applications. Our research is thus devoted to investigating thermal behaviour of supported lipid molecules. We observed by using AFM single phospholipid layers on mica annealed to a selection of temperatures through steps of 2℃~4℃min-1 and then cooled them the same. The single phospholipid layers transit to two-dimensional 2D gas-condensed phase in a temperature range of 49℃ and 52℃ and transit to two-dimensional 2D gas (liquid) phase in a temperature range of 60℃ and 68℃. In addition, the transition process is reversible. The process can be understood in terms of a phase transition from 2D condensed phase to 2D gas (liquid) phase.

Contents
Chapter 1 Introduction ………………………………………………….. 1
Reference ………………………………………………….... 3
Chapter 2 Literature Review ……………………………………………..5
2.1 Introduction of Lipid molecules ………………………….. 5
2.1.1 Liposomes …………………………………………...5
2.1.2 Chemical Composition of DPPC ……………………6
2.2 Lipid Membranes and Planar Bilayer ……………………..7
2.2.1 Lipid Membranes ……………………………………7
2.2.2 Planar Bilayer …………………………………….....9
2.3 Surface Interactions of Supported adsorbable molecules ..12
2.3.1 Self-assembly Layers on Surface …………………..12
2.3.2 Two-dimensional Surface Phase Transformation …..13
2.3.3 Lipid Molecules Phase Transition ………………….17
Reference …………………………………………………20
Chapter 3 Experimental Apparatus and Methods ……………………….22
3.1 AFM Principle ………………............................................22
3.2 AFM Modes ……………………………………………....23
3.3 Experimental System framework ………………………....25
3.3.1 AFM Apparatus ……………………………………...25
3.3.2 Heater ……………………………………………….29
3.4 Experimental Steps ……………………………………….30
3.4.1 Preparation of Liposomes and Lipid Layers ………..30
3.4.2 Heating Procedures ……………………………….. .31
Reference …………………………………………………31
Chapter 4 Result ……………………………………………………….32
4.1 Topographies of Phospholipid Single-Layers ...................32
4.1.1 New Phospholipid Single-Layers Systems ………..32
4.1.2 Annealed and cooled the reappeared Phospholipid Single-Layers ……………………………………..35
4.1.3 Complete Series of AFM topographies of Phospholipid Single-Layers …………………………………......40
4.2 Other Phenomena …………………………………..........44
Chapter 5 Discussion …………………………………………………...50
5.1 Theoretical 2D Phase Transition Model …………………50
5.2 Quantitative Description …………………………………51
5.2.1 The relation of Gas Lipid Molecules Density and Temperature ……………………………………….51
5.2.2 The Behavior of Lipid Tails in Cooling Process ......53
5.3 The Thermal Motion Phenomenological Model of Supported Lipid Single-Layers ……………………………….55
Reference …………………………………………………….58
Chapter 6 Conclusion ..............................................................................59

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