Retinoid chromophores as probes of membrane lipid order.
Retinoid chromophores as probes of membrane lipid order.
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DOI：
10.1021/jp072890b
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发表时间：
2007-08
期刊：
影响因子：
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通讯作者：
Frida Svensson;P. Lincoln;B. Nordén;E. K. Esbjörner
中科院分区：
文献类型：
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作者：
Frida Svensson;P. Lincoln;B. Nordén;E. K. Esbjörner
因此，迫切需要开发独立的方法来研究膜相关蛋白和肽的结构和功能。偏振光光谱（线性二色性，LD）使用剪切对齐的脂质囊泡作为模型膜已成为一个有前途的工具，用于表征膜结合的生物分子的结合几何形状。在这里，我们探讨视黄酸，视黄醇，和视网膜的功能作为探针的剪切变形的100 nm脂质体的宏观对齐的潜力。类维生素A显示负LD，证明它们优选垂直于膜表面排列。LD的大小表明在所有测试的脂质囊泡类型中关于取向程度的维甲酸>视黄醇>视黄醛的顺序。它的结论是，主要是非特异性静电相互作用支配的视黄酸内的双层的表观取向。我们提出了一个简单的模型，如何有效的方向可能与维甲酸探针的末端基团的极性，它们的插入深度，和它们的角分布的配置周围的膜正常。此外，我们提供的证据表明，类维生素A可以感觉到微妙的结构差异，由于膜组成的变化，我们探讨了视黄酸的pH敏感性，这体现在不同的表面电荷的膜中的吸收最大波长的变化。含胆固醇的脂质体的LD测量的基础上，膜成分的弯曲刚度和囊泡变形的影响被认为是在有关的宏观对齐，以及在微观尺度上的脂质链顺序。
There is a great need for development of independent methods to study the structure and function of membrane-associated proteins and peptides. Polarized light spectroscopy (linear dichroism, LD) using shear-aligned lipid vesicles as model membranes has emerged as a promising tool for the characterization of the binding geometry of membrane-bound biomolecules. Here we explore the potential of retinoic acid, retinol, and retinal to function as probes of the macroscopic alignment of shear-deformed 100 nm liposomes. The retinoids display negative LD, proving their preferred alignment perpendicular to the membrane surface. The magnitude of the LD indicates the order retinoic acid > retinol > retinal regarding the degree of orientation in all tested lipid vesicle types. It is concluded that mainly nonspecific electrostatic interactions govern the apparent orientation of the retinoids within the bilayer. We propose a simple model for how the effective orientation may be related to the polarity of the end groups of the retinoid probes, their insertion depths, and their angular distribution of configurations around the membrane normal. Further, we provide evidence that the retinoids can sense subtle structural differences due to variations in membrane composition and we explore the pH sensitivity of retinoic acid, which manifests in variations in absorption maximum wavelength in membranes of varying surface charge. Based on LD measurements on cholesterol-containing liposomes, the influence of membrane constituents on bending rigidity and vesicle deformation is considered in relation to the macroscopic alignment, as well as to lipid chain order on the microscopic scale.