Charge-induced phase separation in lipid membranes
Charge-induced phase separation in lipid membranes
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DOI：
10.1039/c4sm01089b
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发表时间：
2014-01-01
期刊：
影响因子：
3.4
通讯作者：
Takagi, Masahiro
中科院分区：
文献类型：
--
作者：
Himeno, Hiroki;Shimokawa, Naofumi;Takagi, Masahiro
在脂质双分子层相分离，包括带负电荷的脂质实验检查。我们观察了相分离结构，并测定了几种二元和三元脂质混合物(不饱和中性脂、二油基磷脂酰胆碱（DOPC）、饱和中性脂、二油基磷脂酰胆碱（DPPC）、不饱和带电脂、二油基磷脂酰甘油(DOPG（(-)）、饱和带电脂、二油基磷脂酰甘油（DPPG（(-)）和胆固醇）的膜混溶温度。在饱和和不饱和带电荷的脂质二元混合物中，带电荷的头部与烃类尾部的饱和度的结合是影响膜相分离稳定性的主要因素。DPPG（(-)）增强相分离，而DOPG（(-)）抑制相分离。此外，在DPPC/胆固醇二元混合物中加入DPPG（(-)）可诱导富DPPG（(-)）相与富胆固醇相分离。这表明胆固醇的定位在很大程度上取决于亲水头基团上的电荷，而不是碳氢化合物尾部的顺序。最后，将DPPG（(-)）加入到DOPC/DPPC/胆固醇的中性三元体系（传统的膜筏模型）中，产生三相共存。最后，我们用自由能方法讨论了带电膜中相行为的一些定性特征。
Phase separation in lipid bilayers that include negatively charged lipids is examined experimentally. We observed phase-separated structures and determined the membrane miscibility temperatures in several binary and ternary lipid mixtures of unsaturated neutral lipid, dioleoylphosphatidylcholine (DOPC), saturated neutral lipid, dipalmitoylphosphatidylcholine (DPPC), unsaturated charged lipid, dioleoylphosphatidylglycerol (DOPG((-))), saturated charged lipid, dipalmitoylphosphatidylglycerol (DPPG((-))), and cholesterol. In binary mixtures of saturated and unsaturated charged lipids, the combination of the charged head with the saturation of the hydrocarbon tail is a dominant factor in the stability of membrane phase separation. DPPG((-)) enhances phase separation, while DOPG((-)) suppresses it. Furthermore, the addition of DPPG((-)) to a binary mixture of DPPC/cholesterol induces phase separation between DPPG((-))-rich and cholesterol-rich phases. This indicates that cholesterol localization depends strongly on the electric charge on the hydrophilic head group rather than on the ordering of the hydrocarbon tails. Finally, when DPPG((-)) was added to a neutral ternary system of DOPC/DPPC/cholesterol (a conventional model of membrane rafts), a three-phase coexistence was produced. We conclude by discussing some qualitative features of the phase behaviour in charged membranes using a free energy approach.