EFFECTS OF SHORT-CHAIN ALCOHOLS ON THE PHASE-BEHAVIOR AND INTERDIGITATION OF PHOSPHATIDYLCHOLINE BILAYER-MEMBRANES
EFFECTS OF SHORT-CHAIN ALCOHOLS ON THE PHASE-BEHAVIOR AND INTERDIGITATION OF PHOSPHATIDYLCHOLINE BILAYER-MEMBRANES
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DOI：
10.1016/0005-2736(95)00076-f
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发表时间：
1995-07-06
影响因子：
3.4
通讯作者：
CEVE, G
中科院分区：
文献类型：
--
作者：
LOBBECKE, L;CEVE, G
通过羧基荧光素（CF）和磷脂酰乙醇胺罗丹明（PERho）荧光、差示扫描量热法和X射线衍射研究了溶质对二棕榈酰磷脂酰胆碱（DPPC）悬浮液中多晶型和相变的影响。具体而言，通过量热法测定了脂质链熔化相变、预转变和亚转变温度作为本体醇浓度的函数的变化。研究发现，链熔化相变温度 T-m 取决于所添加醇的链长：对于短链醇（直到正丙醇），T-m 随着醇浓度的增加先降低然后升高。然而，对于长链醇，T-m 在整个研究的醇浓度范围内降低。 DPPC 的预转变温度和亚转变温度均随着醇浓度的增加而单调（但非线性）降低，但前一个转变在某些特征性的、链长依赖的醇浓度 c(L beta i) 下消失。 DPPC 依赖于溶质的相图中的这一点是完全碳氢化合物交错的诊断。它针对从甲醇到 1-己醇的一系列短链醇进行了测定。介绍了计算这种极限酒精浓度的定量公式。该公式将 c(L beta i) 值与醇从水性子相转移到 DPPC 子相的自由能联系起来。通过使用表观链长的概念，这种形式也可用于在烃链的第二或第三位置具有极性OH基团的醇。因此，磷脂双层中酒精诱导的碳氢化合物交指主要是由脂质头基区域中溶质诱导的扰动（横向膨胀）引起的。长链醇通过扰乱磷脂链来平衡这种效应，因此不会引起链交叉。
Solute effects on the polymorphism and phase transitions in the suspensions of dipalmitoylphosphatidylcholine (DPPC) were studied by means of carboxyfluorescein (CF) and phosphatidylethanolamine rhodamine (PERho) fluorescence, differential scanning calorimetry, and X-ray diffraction. Specifically, the shifts of the lipid chain-melting phase transition, pretransition and subtransition temperature as a function of the bulk alcohol concentration were determined calorimetrically. The chain-melting phase transition temperature, T-m, was found to depend on the chain-length of the added alcohol: for short-chain alcohols (up to n-propanol), T-m first decreases and then increases with increasing alcohol concentration. For longer-chain alcohols, however, T-m decreases over the whole investigated alcohol concentration range. The pretransition and the subtransition temperature of DPPC both decrease monotonously (but non-linearly) with increasing alcohol concentration, but the former transition disappears at some characteristic, chain-length dependent alcohol concentration, c(L beta i). This point in the solute-dependent phase diagram of DPPC is diagnostic of the complete hydrocarbon interdigitation. It was determined for a series of short-chain alcohols ranging from methanol through to 1-hexanol. A quantitative formula for the calculation of such limiting alcohol concentration is introduced. This formula relates the c(L beta i) values to the free energy of transfer of alcohols from the aqueous sub-phase into the DPPC sub-phase. By using the concept of an apparent chain-length this formalism can also be used for the alcohols with polar OH-groups at the second or third position on the hydrocarbon chain. Alcohol-induced hydrocarbon interdigitation in the phospholipid bilayers is thus shown to result chiefly from the solute-induced perturbation (lateral expansion) in the lipid headgroup region. Longer-chain alcohols, which balance this effect by disordering the phospholipid chains, therefore do not induce chain interdigitation.