Structure and fluctuations of charged phosphatidylserine bilayers in the absence of salt
Structure and fluctuations of charged phosphatidylserine bilayers in the absence of salt
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DOI：
10.1016/s0006-3495(04)74225-3
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发表时间：
2004-03-01
影响因子：
3.4
通讯作者：
Nagle, JF
中科院分区：
文献类型：
--
作者：
Petrache, HI;Tristram-Nagle, S;Nagle, JF
使用X-射线衍射和NMR光谱，我们提出的结构和材料性能的磷脂酰丝氨酸（PS）双层，可以解释有据可查的PS头基在细胞活性的影响。在30 ℃下，处于流体状态的18-碳单不饱和DOPS具有65.3埃（2）的横截面积，其显著小于DOPC类似物的72.5埃（2）的面积，尽管对于带电PS头基预期有额外的静电排斥。类似地，在20 ℃下，凝胶相中的14-碳二饱和DMPS具有40.8埃（2）的面积，DMPC具有48.1埃（2）的面积。这种区域的缩合表明PS头基之间存在额外的吸引力相互作用，可能是氢键。与两性离子脂质不同，PS双层的堆叠随着水的加入而无限膨胀。获得的渗透压与液相DOPS双层水间距的数据是很好的配合计算的Gouy-Chapman政权的静电相互作用。结果表明，静电相互作用完全控制了脉动压力。然而，X射线数据明确地表现出流体相DOPS波动的影响。从我们测量的波动，我们得到的产品的双层弯曲模量K-c和近晶压缩模量B。在相同的双分子层间距下，DOPS的双分子层间波动小于DOPC，表明B和/或K-c较大。补充的X-射线数据，P-31-化学位移各向异性测量的NMR表明，DOPS头基是不太敏感的渗透压比DOPC头基，这是一致的一个较大的K-C在DOPS。四极分裂D2 O衰减不太迅速，随着DOPS比DOPC的水含量的增加，表明更大的扰动层间水，并建议更大的层间水合力在DOPS。我们的PS和PC脂质具有相同的链和相同的温度的双层之间的比较使我们能够专注于这些头基对双层性质的影响。
Using x-ray diffraction and NMR spectroscopy, we present structural and material properties of phosphatidylserine (PS) bilayers that may account for the well documented implications of PS headgroups in cell activity. At 30degreesC, the 18-carbon monounsaturated DOPS in the fluid state has a cross-sectional area of 65.3 Angstrom(2) which is remarkably smaller than the area 72.5 Angstrom(2) of the DOPC analog, despite the extra electrostatic repulsion expected for charged PS headgroups. Similarly, at 20degreesC, the 14-carbon disaturated DMPS in the gel phase has an area of 40.8 Angstrom(2) vs. 48.1 Angstrom(2) for DMPC. This condensation of area suggests an extra attractive interaction, perhaps hydrogen bonding, between PS headgroups. Unlike zwitterionic lipids, stacks of PS bilayers swell indefinitely as water is added. Data obtained for osmotic pressure versus interbilayer water spacing for fluid phase DOPS are well fit by electrostatic interactions calculated for the Gouy-Chapman regime. It is shown that the electrostatic interactions completely dominate the fluctuational pressure. Nevertheless, the x-ray data definitively exhibit the effects of fluctuations in fluid phase DOPS. From our measurements of fluctuations, we obtain the product of the bilayer bending modulus K-c and the smectic compression modulus B. At the same interbilayer separation, the interbilayer fluctuations are smaller in DOPS than for DOPC, showing that B and/or K-c are larger. Complementing the x-ray data, P-31-chemical shift anisotropy measured by NMR suggest that the DOPS headgroups are less sensitive to osmotic pressure than DOPC headgroups, which is consistent with a larger K-c in DOPS. Quadrupolar splittings for D2O decay less rapidly with increasing water content for DOPS than for DOPC, indicating greater perturbation of interlamellar water and suggesting a greater interlamellar hydration force in DOPS. Our comparisons between bilayers of PS and PC lipids with the same chains and the same temperature enable us to focus on the effects of these headgroups on bilayer properties.