Phase behavior and domain size in sphingomyelin-containing lipid bilayers.
Phase behavior and domain size in sphingomyelin-containing lipid bilayers.
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DOI：
10.1016/j.bbamem.2013.01.007
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发表时间：
2013-04
影响因子：
3.4
通讯作者：
Feigenson, Gerald W.
中科院分区：
文献类型：
--
作者：
Petruzielo, Robin S.;Heberle, Frederick A.;Drazba, Paul;Katsaras, John;Feigenson, Gerald W.
膜筏尺寸测量对于理解细胞中筏的稳定性和功能性至关重要。精确测量筏大小的挑战是由不同的域大小的报告证明，其范围从纳米到微米的三元模型膜系统鞘磷脂（SM）/1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）/胆固醇（胆固醇）。利用Förster共振能量转移（FRET）和差示扫描量热法（DSC），我们建立了猪脑SM（bSM）/二油酰-sn-甘油-3-磷酸胆碱（DOPC）/Chol和bSM/POPC/Chol在15和25°C下的相图。通过结合两种具有不同空间灵敏度的技术，即FRET和小角中子散射（SANS），我们显着缩小了bSM/POPC/Chol混合物的区域尺寸估计的不确定性。FRET数据中的组成趋势显示两种混合物在15和25°C下共存的结构域，而SANS测量检测到bSM/POPC/Chol没有结构域形成。总之，这些结果表明，bSM/POPC/Chol中的液体域在25°C下的半径在2和7 nm之间：也就是说，域必须在FRET探针的2-6 nm Förster距离的数量级上，但小于SANS可检测的最小簇尺寸约7 nm。然而，对于棕榈酰SM（PSM）/POPC/Chol在类似的组成，SANS检测到共存的液体域。在用合成PSM替换天然SM组分（其由链长的混合物组成）后结构域尺寸的这种增加表明SM链长在体内调节筏尺寸中的作用。
Membrane raft size measurements are crucial to understanding the stability and functionality of rafts in cells. The challenge of accurately measuring raft size is evidenced by the disparate reports of domain sizes, which range from nanometers to microns for the ternary model membrane system sphingomyelin (SM)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). Using Förster resonance energy transfer (FRET) and differential scanning calorimetry (DSC), we established phase diagrams for porcine brain SM (bSM)/dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Chol and bSM/POPC/Chol at 15 and 25°C. By combining two techniques with different spatial sensitivities, namely FRET and small-angle neutron scattering (SANS), we have significantly narrowed the uncertainty in domain size estimates for bSM/POPC/Chol mixtures. Compositional trends in FRET data revealed coexisting domains at 15 and 25°C for both mixtures, while SANS measurements detected no domain formation for bSM/POPC/Chol. Together these results indicate that liquid domains in bSM/POPC/Chol are between 2 and 7 nm in radius at 25°C: that is, domains must be on the order of the 2–6 nm Förster distance of the FRET probes, but smaller than the ~7 nm minimum cluster size detectable with SANS. However, for palmitoyl SM (PSM)/POPC/Chol at a similar composition, SANS detected coexisting liquid domains. This increase in domain size upon replacing the natural SM component (which consists of a mixture of chain lengths) with synthetic PSM, suggests a role for SM chain length in modulating raft size in vivo.
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