Interplay between lipid lateral diffusion, dye concentration and membrane permeability unveiled by a combined spectroscopic and computational study of a model lipid bilayer
Interplay between lipid lateral diffusion, dye concentration and membrane permeability unveiled by a combined spectroscopic and computational study of a model lipid bilayer
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DOI：
10.1038/s41598-018-37814-x
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发表时间：
2019-02-06
影响因子：
4.6
通讯作者：
Brancato, Giuseppe
中科院分区：
文献类型：
--
作者：
Akhunzada, Muhammad Jan;D'Autilia, Francesca;Brancato, Giuseppe
脂质横向扩散在膜双层是一个基本的过程，利用细胞使复杂的蛋白质结构和动态重组。由于其重要性，脂质在细胞和模型双层中的流动性近年来得到了广泛的研究，特别是通过时间分辨、荧光光学显微镜技术的应用。然而，荧光技术的一个警告是需要使用感兴趣的脂质的染料标记变体，因此可能会干扰本地物种的结构和动态特性。一般来说，染料/示踪剂分子的影响被隐式地假定为可以忽略不计。然而，鉴于光学修饰脂类广泛用于研究脂质双分子层动力学，很有必要对这一点进行评估。在这里，荧光相关光谱（FCS）和分子动力学（MD）模拟结合在一起，揭示了富含标准罗丹明标记脂质的DOPC平面膜的微妙结构和动力学效应。我们的研究结果支持染料标记的脂质在扩散实验中的非中性作用，定量估计相对于未标记的物种，脂质流动性降低高达20%。此外，研究结果强调了染料浓度、脂质横向扩散和膜通透性之间存在的相互作用，从而为未来在膜水平上发生的生物物理过程的光学显微镜研究提供了可能的启示。
Lipid lateral diffusion in membrane bilayers is a fundamental process exploited by cells to enable complex protein structural and dynamic reorganizations. For its importance, lipid mobility in both cellular and model bilayers has been extensively investigated in recent years, especially through the application of time-resolved, fluorescence-based, optical microscopy techniques. However, one caveat of fluorescence techniques is the need to use dye-labeled variants of the lipid of interest, thus potentially perturbing the structural and dynamic properties of the native species. Generally, the effect of the dye/tracer molecule is implicitly assumed to be negligible. Nevertheless, in view of the widespread use of optically modified lipids for studying lipid bilayer dynamics, it is highly desirable to well assess this point. Here, fluorescence correlation spectroscopy (FCS) and molecular dynamics (MD) simulations have been combined together to uncover subtle structural and dynamic effects in DOPC planar membranes enriched with a standard Rhodamine-labeled lipid. Our findings support a non-neutral role of the dye-labeled lipids in diffusion experiments, quantitatively estimating a decrease in lipid mobility of up to 20% with respect to the unlabeled species. Moreover, results highlight the existing interplay between dye concentration, lipid lateral diffusion and membrane permeability, thus suggesting possible implications for future optical microscopy studies of biophysical processes occurring at the membrane level.