利用3-羥基色原酮的衍生物螢光偵測磷脂及界面活性劑自組裝結構的微環境

The Study Of Microenvironments Of Self-assembled Lipids And Surfactants By The Fluorescent Dye, FA.

黃英豪(Huang, YingHao)

指導教授 ： 楊子萱

國立中正大學/理學院/化學暨生物化學系/碩士(2012年)

摘要

生物細胞膜上有許多非均相的環境，稱作為微區塊(microdomain)。這些區塊具有特殊的物化性質，在生物反應上扮演著重要的角色。
2-(6-diethylaminobenzo[b]furan-2-yl)-3-hydroxychromone(FA)是一種對於低溶劑極性非常靈敏的螢光分子。FA受光激發後，會在激發態進行分子內質子轉移得到其互變異構物而有兩個不同放光波帶N*(normal)與T*(tautomer)波帶。兩波帶的相對放光強度會因溶劑的極性不同而改變且波帶位置也會產生位移。另外FA可能會和提供氫鍵的溶劑分子形成複合物進行另一種放光機制，放出H-N*(hydrated normal)波帶。因此，我們希望藉由FA螢光對環境極性的靈敏性來探測不同成分磷脂及界面活性劑的自組裝結構(如微胞(micelles)及囊泡(vesicles))、加入不同膽固醇量、不同大小囊泡的微環境極性及水合情形的差異性。我們將FA酒精溶液加入不同囊泡及微胞溶液，使用波長442 nm的He-Cd雷射激發，測量其螢光放光光譜及螢光激發光譜。透過log-normal方程分析N*、T*與H-N*的波帶貢獻。
首先，在不同的微胞系統中，我們透過螢光放光光譜與螢光激發光譜得知FA在微胞系統中處於至少兩個不同的微環境，且具有H-N*波帶的存在。接著，在不同單磷脂分子組成中，中性磷脂環境極性：SM >POPC >DPPC，而水合程度則是SM=POPC>DPPC。不同比例磷脂分子成分中，隨著不同磷脂分子的含量環境極性與水合程度影響的情形並無規律。在加入不同含量膽固醇囊泡實驗，膽固醇除了降低環境的水合情形，也改變了囊泡的環境極性。隨著膽固醇加入的量增加，環境極性會逐漸增加。在SM(鞘磷脂)/Chol.(膽固醇)莫耳比為1：0.15時水合程度最低。在巨單層囊泡(GUV)的系統中，我們推測環境極性與水合程度與囊泡大小並沒有太大的關係，而是囊泡的磷脂組成成分影響環境極性與水合程度較大。從我們的實驗結果得知，FA可同時偵測環境極性與磷脂的水合程度。

關鍵字

自組裝結構 ； 激發態分子內質子轉移 ； 微環境

並列摘要

On the cell membrane, there are many heterogeneous phases, called microdomains. In these domains, properties of lipids are very different from those in the homogenous phases. These microdomains play important roles in biochemical reactions.
2-(6-diethylaminobenzo[b]furan-2-yl)-3-hydroxychromone(FA) is a fluorescent dye extremely sensitive to the polarity of solvent. After the charge-transfer electronic excitation, FA will undergo the excited-state intramolecular proton transfer(ESIPT), and emit N*(normal) and T*(tautomer) fluorescence bands. The relative intensity and shifts of two bands change with the polarity of solvent. Besides, FA may form hydrogen bond with protic solvents and will undergo another route of emission to release H-N*(hydration-N*) band. In this study, we investigated the use of FA to distinguish the polarity and hydration of microenvironments formed in the different self-assemblies of lipids, surfactants, and the mixtures of phospholipids with cholesterol. The excitation wavelength for FA is 442 nm. We used the log-normal function to analyze the spectra.
From experimental results, firstly, we found the differences in polarity and hydration for the micelles and vesicles of different compositions. Secondly, when increasing the amount of cholesterol, the degree of hydration decreases, but polarity increases. We knew that cholesterol could affect the hydration of vesicles. Thirdly, in the case of giant unilammelar vesicles, the polarity and hydration of vesicles are independent of the size of the vesicle. They depend only on the compositions of vesicles. Based on our results, FA could simultaneously detect the polarity and hydration of self-assemblies of lipids and surfactants.

並列關鍵字

self-assembled ； Excited state intramolecular proton transfer ； microenvironment

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