Hydrophobic ion hydration and the magnitude of the dipole potential
Hydrophobic ion hydration and the magnitude of the dipole potential
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DOI：
10.1016/s0006-3495(02)75649-x
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发表时间：
2002-06-01
影响因子：
3.4
通讯作者：
Clarke, RJ
中科院分区：
文献类型：
--
作者：
Schamberger, J;Clarke, RJ
脂质膜偶极电位的大小通常根据疏水性离子、四苯基硼酸盐和四苯基砷或四苯基鏻之间的电导差来估计。该计算基于四苯胂-四苯硼酸盐假设，即阴离子和阳离子的水合能大小相等（即，电荷无关），因此它们不同的跨膜传输速率仅是由于与膜相的不同相互作用所致。在这里，我们通过水合能的量子力学计算来研究这一假设的有效性。研究发现四苯硼酸盐 (DeltaG(Hydr) = -168 kJ mol(-1)) 与水的相互作用明显强于四苯砷鎓 (DeltaG(Hydr) = - 145 kJ mol(-1)) 或四苯基鏻 (DeltaG(Hydr) = -157 kJ mol(-1))。考虑到这些差异，重新计算文献电导数据，得到膜内部偶极电位值比之前的估计值高 57 至 119 mV。这可能部分解释了从脂质单层计算的偶极电位值与双层测定的偶极电位值之间通常观察到的至少 100 mV 的差异。
The magnitude of the dipole potential of lipid membranes is often estimated from the difference in conductance between the hydrophobic ions, tetraphenylborate, and tetraphenylarsonium or tetraphenylphosphonium. The calculation is based on the tetraphenylarsonium-tetraphenylborate hypothesis that the magnitude of the hydration energies of the anions and cations are equal (i.e., charge independent), so that their different rates of transport across the membrane are solely due to differential interactions with the membrane phase. Here we investigate the validity of this assumption by quantum mechanical calculations of the hydration energies. Tetraphenylborate (DeltaG(hydr) = -168 kJ mol(-1)) was found to have a significantly stronger interaction with water than either tetraphenylarsonium (DeltaG(hydr) = - 145 kJ mol(-1)) or tetraphenylphosphonium (DeltaG(hydr) = -157 kJ mol(-1)). Taking these differences into account, literature conductance data were recalculated to yield values of the dipole potential 57 to 119 mV more positive in the membrane interior than previous estimates. This may partly account for the discrepancy of at least 100 mV generally observed between dipole potential values calculated from lipid monolayers and those determined on bilayers.