Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa 3200003, Israel.
Wolfson Department of Chemical Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel.
ACS Nano. 2024 Feb 13;18(6):5101-5112. doi: 10.1021/acsnano.3c11990. Epub 2024 Feb 5.
Lateral proton transport (PT) on the surface of biological membranes is a fundamental biochemical process in the bioenergetics of living cells, but a lack of available experimental techniques has resulted in a limited understanding of its mechanism. Here, we present a molecular protonics experimental approach to investigate lateral PT across membranes by measuring long-range (70 μm) lateral proton conduction via a few layers of lipid bilayers in a solid-state-like environment, i.e., without having bulk water surrounding the membrane. This configuration enables us to focus on lateral proton conduction across the surface of the membrane while decoupling it from bulk water. Hence, by controlling the relative humidity of the environment, we can directly explore the role of water in the lateral PT process. We show that proton conduction is dependent on the number of water molecules and their structure and on membrane composition, where we explore the role of the headgroup, the tail saturation, the membrane phase, and membrane fluidity. The measured PT as a function of temperature shows an inverse temperature dependency, which we explain by the desorption and adsorption of water molecules into the solid membrane platform. We explain our findings by discussing the role of percolating hydrogen bonding within the membrane structure in a Grotthuss-like mechanism.
生物膜表面的横向质子传递（PT）是活细胞生物能量学中的一个基本生化过程，但由于缺乏可用的实验技术，其机制仍未得到充分理解。在这里，我们提出了一种分子质子学实验方法，通过在类似于固态的环境中测量通过几层脂质双层的长程（70μm）横向质子传导，来研究跨膜的横向 PT。这种配置使我们能够专注于膜表面的横向质子传导，同时将其与体相水分相分离。因此，通过控制环境的相对湿度，我们可以直接探索水在横向 PT 过程中的作用。我们表明，质子传导取决于水分子的数量及其结构以及膜的组成，其中我们探索了头基、尾部饱和、膜相和膜流动性的作用。测量的质子传递作为温度的函数显示出反温度依赖性，我们通过水分子进入固体膜平台的解吸和吸附来解释这一现象。我们通过讨论在类 Grotthuss 机制中膜结构内的质子扩散氢键的作用来解释我们的发现。
