Dynamic molecular structure and phase diagram of DPPC-Cholesterol binary mixtures: A 2D-ELDOR study
Dynamic molecular structure and phase diagram of DPPC-Cholesterol binary mixtures: A 2D-ELDOR study
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DOI：
10.1021/jp0732110
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发表时间：
2007-09-27
影响因子：
3.3
通讯作者：
Freed, Jack H.
中科院分区：
文献类型：
--
作者：
Chiang, Yun-Wei;Costa, Antonio J.;Freed, Jack H.
本文将二维电子-电子双共振（2D- eldor）与“全方法”应用于模型膜的研究。我们获得并确认了1,2-二棕榈酰-sn-甘油磷脂酰胆碱(DPPC)-胆固醇二元混合物随温度变化的相图，并利用2D-ELDOR在Ku波段对其动态分子结构进行了定量描述。在胆固醇摩尔浓度为0 ~ 50%和25 ~ 60℃范围内，获得了多层磷脂囊泡端链16-PC自旋标记的光谱。该相图由液体有序、液体无序、凝胶相和相共存区组成。根据光谱证据仔细检查相图，并对线形变化进行严格解释。我们发现2D-ELDOR光谱随成分的变化而显著不同。二维加混合时间表示中广泛的线形变化提供了有用的信息，可以定义和表征膜相的动态分子结构，并确定相边界。从纯吸收光谱中提取均匀的T-2，用于进一步区分膜相。这些结果表明，2D-ELDOR自然适合探测和报告模型膜系统中微域的动态结构，而且，特别是在“全Sc-方法”的帮助下，提供了其分子动态结构的非常详细的图像。
This paper is an application of 2D electron-electron double resonance (2D-ELDOR) with the "full Scmethod" to study model membranes. We obtain and confirm the phase diagram of 1,2-dipalmitoyl-sn-glycerophosphatidylcholine (DPPC)-cholesterol binary mixtures versus temperature and provide quantitative descriptions for its dynamic molecular structure using 2D-ELDOR at the Ku band. The spectra from the end-chain 16-PC spin label in multilamellar phospholipid vesicles are obtained for cholesterol molar concentrations ranging from 0 to 50% and from 25 to 60 degrees C. This phase diagram consists of liquid-ordered, liquid-disordered, and gel phases and phase coexistence regions. The phase diagram is carefully examined according to the spectroscopic evidence, and the rigorous interpretation for the line shape changes. We show that the 2D-ELDOR spectra differ markedly with variation in the composition. The extensive line shape changes in the 2D-plus-mixing-time representation provide useful information to define and characterize the membrane phases with respect to their dynamic molecular structures and to determine the phase boundaries. The homogeneous T-2's are extracted from the pure absorption spectra and are used to further distinguish the membrane phases. These results show 2D-ELDOR to be naturally suitable for probing and reporting the dynamic structures of microdomains in model membrane systems and, moreover, providing a very detailed picture of their molecular dynamic structure, especially with the aid of the "full Sc- method".