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題 名 | Dehydration Induces the Complexity Phases in Phospholipid Bilayers=磷脂膜去水導致的複雜相態之研究 |
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作 者 | 洪偉清; | 書刊名 | 黃埔學報 |
卷 期 | 52(工程科學類) 2007.03[民96.03] |
頁 次 | 頁47-61 |
分類號 | 361.191 |
關鍵詞 | 磷脂膜去水; X光繞射; 脂膜相態行為; 靜水合壓力作用; |
語 文 | 英文(English) |
中文摘要 | 利用小角度X 光繞射實驗,測量DLPC 多片層脂膜的結構及水含量隨溫度,T 及滲透壓力,Π的關係,比較流體態與相變後不同的膠體態的行為。實驗結果顯示利用滲透壓力所造成的脂膜相態行為與靜水合壓力作用的效果十分相似。沿著第一階相變的共存線,流體態會在三個不同的T 和 Π 的範圍,分別相變到不同的膠體態,在這三個不同溫濕度範圍,流體態的脂膜會因碳氫鏈有三種不同程度的部份伸直狀態,而使厭水區的厚度呈現三個階梯狀的變化。而每一個階梯都對應一個臨界厚度,Dc* 及伸直狀態下的碳原子個數,nt*。我們發現於低T 和低 Π ,在nt*~3.3 和 Dc*~23.92Å 時,脂膜將相變到漣漪狀的Pβ’相態。於中T 和中Π,在nt*~5.7 和 Dc*~25.40Å 時,脂膜將相變到三維結晶狀的Lc 相態。於高T 和高 Π ,在nt*~7.6 和 Dc*~26.78Å 時,脂膜將相變到Lβ’相態。由厭水區厚度隨Π 的變化,可得知流體態與Lβ’相態比Pβ’相態及Lc 相態更容易隨水合程度變化而產生形變。這實驗結果確定了Pβ’和Lc 相態的脂膜分子間的作用具有很強的相干性。我們利用一個類似Clapeyron 方程式來描述流體態相變到膠體態的熱力學行為,並藉由測量的結構計算出相變時熵的變化量及潛熱的大小。其中相變到Lc 相態時釋放的潛熱最大,這表示三維結晶狀的Lc 是這些相態中最堅硬的相態。對於相變到Pβ’相態的潛熱隨溫度降低而下降,當溫度T 降到主要相變溫度,-1℃時,所外插得到的潛熱與用比熱計測量在飽和含水下的潛熱非常吻合。在本文測量的溫度範圍雖然沒有發現高溫的臨界點,但由我們的數據卻顯示在高於35℃的溫度時很有可能發現臨界點。 |
英文摘要 | The bilayer structure and the water content of DLPC bilayers lamellae were measured as a function of temperature, T, and osmotic pressure, Π, by small-angle x-ray diffraction. The fluid phase and its transition to different gel phases were explored. Phase diagram reveals that osmotic pressure affects the bilayer phase behaviors much like hydrostatic pressure. Along the first-order transition to three different gel phases in three different regimes of T and Π, the fluid phase bilayer exhibits chain partial ordering in three-step staircase change, which creates three different critical values of hydrophobic thickness, Dc* and the corresponding number of trans-carbon, nt*. We found nt*~3.3 and Dc*~23.92Å for transition to ripple Pβ’ phase in regime of low T and Π; nt*~5.7 and Dc*~ 25.40Å to 3-D crystalline Lc phase in regime of medium T and Π; nt*~7.6 and Dc*~ 26.78Å to Lβ’ phase in regime of high T and Π. The hydrophilic thickness as a function of Π reveals that fluid and Lβ’ phases are more easily dehydrated and deformed, as compared to Pβ’ and Lc phases. This confirms the fact that those bilayers in Pβ’ and Lc phases are strongly correlated each other. An analogous Clapeyron equation was derived to describe the thermodynamics of fluid to gel phase transition. The entropy change and the latent heat were then calculated from the measured structural change. Both of them are larger for Lc phase, implying that 3-D crystalline Lc phase is the most rigid phase among three gel phases. The latent heat for Pβ’ transition decreases with T decreasing, and when T is decreased to the main transition temperature, -1℃, the extrapolated value of latent heat is in excellent with the calorimetric measurement on fully hydrated bilayers. No critical point was found in the regime of T we explored, yet our data shows the possibility of finding the critical point in much higher temperature, that is , beyond 35℃. |
本系統中英文摘要資訊取自各篇刊載內容。