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題 名 | Capillary Wetting Effect of DMPC Bilayers in Gel Phase=DMPC雙層磷脂膜在膠體態的毛細增濕效應 |
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作 者 | 洪偉清; | 書刊名 | 黃埔學報 |
卷 期 | 51 民95.10 |
頁 次 | 頁57-73 |
分類號 | 467.13 |
關鍵詞 | 雙層磷脂膜; 膠體態; 毛細增濕效應; DMPC; X-ray diffraction; Membrane tension; Hydrophobic interface; Capillary wetting; |
語 文 | 英文(English) |
中文摘要 | 利用水蒸氣滲透壓/小角度X 光繞射實驗,測量Lβ'相態的DMPC 脂膜在不同的溫度、濕度的結構。本實驗可測得12 階的Bragg 繞射峰,經分析可得到約具有2Å 高解析度的電子密度空間分佈圖,使我們能測得磷脂質分子的極性頭群區、厭水區的厚度及兩膜層間相隔的距離,並由這些基本參數得以計算出碳氫鏈的傾斜角度、磷脂質分子的截面積、含水量及膜層間作用力與距離的關係。本文首先證實脂膜頭群區的結構不因水合程度及溫度改變而異;當脂膜含水量在接近飽和時,其結構卻幾乎已經完成架構,此時包括截面積、傾斜角度及厭水區的厚度都幾乎不再隨水合程度增加而改變,但水分子仍然會進入脂膜系統,而此時進入的水分子則大部份都充填在兩膜層間,以使膜層間的距離增大,我們將此現象稱為"毛細增溼"。在毛細增溼發生前, 除了頭群區結構不變外,其餘的基本參數都會隨水合程度不同而異。此時脂膜間完全展現水合排斥力,此作用力隨膜層間的距離增大而呈現指數衰減,這性質不隨溫度不同而異。當毛細增溼開始發生時,則所有結構卻都幾乎停止改變,僅有兩膜層間因水分子進入而使得距離變大,兩膜層並藉由水分子的氫鍵作用力來聯繫。在高溫時,水分水子熱運動程度大,使脂膜軟化,而增加膜層間的排斥力。所以在較高溫時,要在更大的膜層間距離,其排斥力才會開始變弱。 |
英文摘要 | Hydration dependence of DMPC bilayers at Lβ’ phase is measured by vapor osmosis/small-angle x-ray diffraction. The 12 Bragg’s orders diffraction results in a trans-bilayer electron density profile (edp) of 2Å resolution. Such high resolution edp turns out to be able to resolve out the polar head-group region, the hydrophobic core and the bilayer’s separation for bilayers in lamellar phase. The chain tilt angle, the lipid in-plane area, the water content and the bilayer force-distance relation are all easily determined. The hydration dependence of these quantities is evaluated in a wide range of temperature. We first found that head-group region is invariant with the change of hydration and temperature. We next discovered in a range near full hydration that the bilayer is already built-up in its final structure where the lipid area, chain tilt angle, and hydrophobic thickness are nearly unchanged with hydration. We call the hydration in this region as the capillary wetting between two well established bilayer surfaces. Before the onset of capillary wetting, all quantities except the invariant head region are changed with hydration, and the inter-bilayer force is straightly the hydration repulsion, decaying exponentially with bilayer separation. And all changes have nothing to do with the temperature. In the regime of capillary wetting, although the bilayer structure almost stop changing with hydration, the water molecules were still brought into and reside between bilayers. These next coming water for capillary wetting are supposed to connect bilayers via hydrogen bonds thus have certain degrees of thermal motion to get bilayers wet and thus soften. The consequence is that the hydration force is weakened by a significant van der Walls attraction and such weakening begins at larger separation for high temperature due to thermal fluctuation of the wet, soften bilayers. |
本系統中英文摘要資訊取自各篇刊載內容。