电子自旋标记于两种共存的磷脂质相态中的不对称分布(英文)

Asymmetric Partition of Spin Labeled Lipids in the Coexistence of DPPC-Rich Ordered and DLPC-Rich Fluid Phases

该文探讨自旋标记于不同磷脂质相中不对称分布的分子机制.透过电子自旋共振(ESR)波谱技术以及理论波谱分析,探究两种在磷脂质不同烷基位点上的自旋标记(16-PC &5-PC)于两种明显不同物理性质的磷脂质(DPPC &DLPC)所构成的细胞膜两相共存区域具有不对称分布情形.根据实验结果,如果自旋探针平均分布在两相之间,则其波谱将能根据杠杆法则(lever rule)来拟合波谱的结果,而自旋探针的分布反映了该探针周围环境的脂质所给予的立体障碍,而这个不对称的情形可以合理的解释成自旋标记的表面自由面积所造成.根据结果,16-PC会平均分布在两个不同的相区域,而5-PC则会有不对称分布的情形.

The molecular mechanisms that regulate the asymmetric partitioning of the nitroxide spin-labeled lipids,5-PC and 16-PC,in the coexistence of DLPC-rich liquid-disordered and DPPC-rich gel phases are investigated.In the two-phase coexistence region,our results of the ESR spectra show that the partition of 16-PC into the two phases strictly follows the ＂lever rule＂ as a function of composition by fitting the spectra with two conjugated phases.On the other hand,5-PC spin label does not partition equally in the same region.This indicates the asymmetric partitioning of lipid spin labels that is due to the steric environment at which the spin label is attached.The mechanism of the asymmetric partitioning is rationalized in terms of the local free-surface-area of spin label,which is demonstrated the major factor that affects the partitioning of spin labels into the coexisting phases.The analysis result from the stochastic spectral simulations unravels the complex mixing behaviors and molecular incorporation of the labeled molecules in the membrane phases,irrespective of their asymmetric partition.