Lateral proton conduction at lipid–water interfaces and its implications for the chemiosmotic-coupling hypothesis
Lateral proton conduction at lipid–water interfaces and its implications for the chemiosmotic-coupling hypothesis
复制标题
脂水界面的横向质子传导及其对化学渗透耦合假说的影响
作者：
M. Prats;J. Teissié;J. Tocanne
能量传递膜的驱动力现在被认为与膜结合的供体和受体之间的质子通量有关。关于质子路径是离域在膜两侧的两个水相中(离域化学渗透理论1)，还是位于膜表面(半定域假设2)的问题，仍然有待讨论3，4。使用原始的荧光单分子膜技术，我们最近能够提供直接的实验证据，证明磷脂-水界面可以作为有效的质子导体5，6。这一观察有力地支持了半定域假设2。在本研究中，单分子膜的表面电势和荧光测量之间的比较提供了沿着磷脂-水界面促进质子传导的额外证据。它们表明，从酸性较强的表面向主体表面存在诱导的陡峭的表面pH梯度。它们还表明，沿生物膜表面的横向质子转移会改变该膜的表面电位。
The driving force in energy-transducing membranes is now recognized to be linked to a flux of protons between membrane-bound donors and acceptors. The question of whether the proton pathway is delocalized within the two bulk aqueous phases on each side of the membrane (delocalized chemiosmotic theory1), or is localized at its surface (semi-localized hypothesis2) still remains open to discussion3,4. Using an original fluorescence monolayer technique, we have recently been able to provide direct experimental evidence that a phospholipid–water interface can act as an efficient proton conductor5,6. This observation strongly supports the semi-localized hypothesis2. In the present study, comparisons between surface potential and fluorescence measurements in monolayers provide additional evidence of a facilitated proton conduction along phospholipid–water interfaces. They suggest the existence of an induced steep surface pH gradient from a more acidic surface towards the bulk. They also show that lateral proton transfer along the surface of a biological membrane would alter the surface potential of that membrane.