Molecular dynamics simulations of DiI-C18(3) in a DPPC lipid bilayer
Molecular dynamics simulations of DiI-C18(3) in a DPPC lipid bilayer
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DOI：
10.1039/b716979e
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发表时间：
2008-01-01
影响因子：
3.3
通讯作者：
Butler, Peter J.
中科院分区：
文献类型：
--
作者：
Gullapalli, Ramachandra R.;Demirel, Melik C.;Butler, Peter J.
我们对1，2-二棕榈酰-sn-甘油-3-磷脂酰胆碱（DPPC）双层中的1，1 '-双十八烷基-3，3，30，3'-四甲基吲哚羰花青高氯酸盐（DiI-C-18（3））进行了40 ns的模拟，以便于从荧光寿命、各向异性和荧光相关光谱（FCS）解释脂质动力学和膜结构。掺入DiI的1.6至3.2摩尔%诱导每脂质面积的变化可以忽略不计，但可检测到的双层厚度的增加，其中每一个都是膜结构扰动的指标。DiI发色团的角度为77 +/- 171相对于正常的双层，一致的旋转扩散从偏振研究推断。DiI头基位于脂质头基-水界面下方0.63 nm处，这是一个与一些流行的DiI卡通表示相反的新结果，但与DiI掺入脂质双层时量子产率的增加一致。重要的是，旋转各向异性的快速组件相匹配的实验结果表明，足够的自由体积存在于子界面区域，以支持快速旋转。模拟与不带电的二碘头基团表现出二碘触发器，表明带正电的发色团稳定的方向和位置的二碘在一个单一的单层。DiI诱导可检测到的变化，水的排序，静电势的界面特性，并在DPPC脂质的P-N矢量方向的变化。DiI的扩散系数（9.7 +/- 0.02 x 10（-8）cm（2）s（-1））与DPPC分子的扩散系数（10.7 +/- 0.04 x 10（-8）cm（2）s（-1））相似，支持DiI动力学反映脂质动力学的结论。这些结果提供了第一个原子水平的洞察DiI动力学，结果在阐明脂质动力学通过单分子荧光研究必不可少。
We performed a 40 ns simulation of 1,1'-dioctadecyl-3,3,30,3'-tetramethylindocarbocyanine perchlorate (DiI-C-18(3)) in a 1,2-dipalmitoyl-sn-glycero-3-phosphatidyl choline ( DPPC) bilayer in order to facilitate interpretation of lipid dynamics and membrane structure from fluorescence lifetime, anisotropy, and fluorescence correlations spectroscopy (FCS). Incorporation of DiI of 1.6 to 3.2 mol% induced negligible changes in area per lipid but detectable increases in bilayer thickness, each of which are indicators of membrane structural perturbation. The DiI chromophore angle was 77 +/- 171 with respect to the bilayer normal, consistent with rotational diffusion inferred from polarization studies. The DiI headgroup was located 0.63 nm below the lipid head group-water interface, a novel result in contrast to some popular cartoon representations of DiI but consistent with DiI's increase in quantum yield when incorporated into lipid bilayers. Importantly, the fast component of rotational anisotropy matched published experimental results demonstrating that sufficient free volume exists at the sub-interfacial region to support fast rotations. Simulations with non-charged DiI head groups exhibited DiI flip-flop, demonstrating that the positively-charged chromophore stabilizes the orientation and location of DiI in a single monolayer. DiI induced detectable changes in interfacial properties of water ordering, electrostatic potential, and changes in P-N vector orientation of DPPC lipids. The diffusion coefficient of DiI (9.7 +/- 0.02 x 10(-8) cm(2) s(-1)) was similar to the diffusion of DPPC molecules (10.7 +/- 0.04 x 10(-8) cm(2) s(-1)), supporting the conclusion that DiI dynamics reflect lipid dynamics. These results provide the first atomistic level insight into DiI dynamics, results essential in elucidating lipid dynamics through single molecule fluorescence studies.