Quantitative determination of conformational disorder in the acyl chains of phospholipid bilayers by infrared spectroscopy.
Quantitative determination of conformational disorder in the acyl chains of phospholipid bilayers by infrared spectroscopy.
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DOI：
10.1021/bi00448a037
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发表时间：
1989-10
期刊：
影响因子：
2.9
通讯作者：
R. Mendelsohn;M. Davies;J. Brauner;H. F. Schuster;R. Dluhy
中科院分区：
文献类型：
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作者：
R. Mendelsohn;M. Davies;J. Brauner;H. F. Schuster;R. Dluhy
提出并证明了一种直接测定构象紊乱（反式异构化）作为磷脂双层膜中酰基链位置函数的方法。合成了三类二棕榈酰磷脂酰胆碱 (DPPC) 的特定氘化衍生物，即 4,4,4',4'-d4-DPPC (4-d4-DPPC)、6,6,6',6'-d4-DPPC (6-d4-DPPC) 和 10,10,10',10'-d4-DPPC (10-d4-DPPC)。傅里叶变换红外 (FT-IR) 光谱中的 CD2 摇摆模式已作为每个导数的温度函数进行监测。 Snyder 和 Poore 最初采用的方法 [(1973) Macromolecules 6, 708-715] 作为烷烃中烃链构象的特异性探针，已用于分析数据。对于被反式 C-C-C 骨架包围的 CD2 片段，摇摆模式出现在 622 cm-1 处；对于被特定的粗俗构象异构体包围的片段，摇摆模式出现在 645 到 655 cm-1 之间。这些模式的积分谱带强度已用于监测双层特定深度处酰基链的反式高斯异构化。在 48 摄氏度，高于凝胶-液晶相变时，4-d4-DPPC、6-d4-DPPC 和 10-d4-DPPC 中存在的高斯旋转异构体的百分比分别为 20.7 +/- 4.2、32.3 +/- 2.3 和 19.7 +/- 0.8。后两个分子的凝胶相是高度有序的。相反，在 4-d4-DPPC 中观察到大量的粗略旋转异构体。构象分析产生了相变以上 DPPC 的 3.6-4.2 个gauche 旋转异构体/酰基链。该范围与 Nagle 和 Wilkinson 的膨胀数据非常一致 [(1978) Biophys. J.23, 159-175]。讨论了 FT-IR 方法的显着优势。
A method is proposed and demonstrated for the direct determination of conformational disorder (trans-gauche isomerization) as a function of acyl-chain position in phospholipid bilayer membranes. Three specifically deuterated derivatives of dipalmitoylphosphatidylcholine (DPPC), namely 4,4,4',4'-d4-DPPC (4-d4-DPPC), 6,6,6',6'-d4-DPPC (6-d4-DPPC), and 10,10,10',10'-d4-DPPC (10-d4-DPPC), have been synthesized. The CD2 rocking modes in the Fourier transform infrared (FT-IR) spectrum have been monitored as a function of temperature for each derivative. A method originally applied by Snyder and Poore [(1973) Macromolecules 6, 708-715] as a specific probe of hydrocarbon chain conformation in alkanes has been used to analyze the data. The rocking modes appear at 622 cm-1 for a CD2 segment surrounded by a trans C-C-C skeleton and between 645 and 655 cm-1 for segments surrounded by particular gauche conformers. The integrated band intensities of these modes have been used to monitor trans-gauche isomerization in the acyl chains at particular depths in the bilayer. At 48 degrees C, above the gel-liquid-crystal phase transition, the percentage of gauche rotamers present is 20.7 +/- 4.2, 32.3 +/- 2.3, and 19.7 +/- 0.8 for 4-d4-DPPC, 6-d4-DPPC, and 10-d4-DPPC, respectively. The gel phase of the latter two molecules is highly ordered. In contrast, a substantial population of gauche rotamers was observed for the 4-d4-DPPC. The conformational analysis yields a range of 3.6-4.2 gauche rotamers/acyl chain of DPPC above the phase transition. This range is in excellent accord with the dilatometric data of Nagle and Wilkinson [(1978) Biophys. J. 23, 159-175]. The significant advantages of the FT-IR approach are discussed.