Bożek Justyna, Dziubak Damian, Grempka Arkadiusz, Sek Slawomir, Brand Izabella
Carl von Ossietzky Universität Oldenburg, Institute of Chemistry, 26111 Oldenburg, Germany.
University of Warsaw, Faculty of Chemistry, Biological and Chemical Research Centre, Zwirki i Wigury 101, Warsaw 02-089, Poland.
Langmuir. 2025 Aug 12;41(31):20942-20953. doi: 10.1021/acs.langmuir.5c02620. Epub 2025 Jul 30.
Bicelles are hybrid, disk-shaped aggregates. Bicelles with a diameter of 11.8 ± 0.2 nm containing a long-chain lipid (1,2-dimyristoyl--glycero-3-phosphocholine, DMPC) in their core and a short-chain, rim forming, lipid (1,2-diheptanoyl--glycero-3-phosphocholine, DHPC) were prepared. A 100-fold dilution of the stock bicelle solution destabilizes the aggregate structure. Under this condition, the bicelles spread onto a β-thioglucose:6-mercaptohexanoic acid monolayer modifying Au(111) surface to form a free-standing floating DMPC bilayer while the DHPC molecules form micelles and diffuse into the electrolyte solution. Electrochemical impedance spectroscopy, electrochemically controlled quartz crystal microbalance, and polarization modulation infrared reflection absorption spectroscopy were applied to probe the macroscopic properties and potential-driven molecular scale changes in the floating DMPC bilayer. They are dependent on the sign of the membrane potential. The high values of the membrane resistance (ca. 2 MΩ cm) indicate the formation of a compact, defect-free bilayer. At negative membrane potentials, the membrane resistance and tilt of the acyl chains (thickness of the membrane) change linearly as a function of potential, indicating that ion conduction occurs through the defect-free bilayer. A transition to positive membrane potentials leads to an abrupt decrease in the membrane resistance and tilting of acyl chains. These sudden reorientations lead to the formation of defects in the membrane structure as observed in electrochemical impedance spectroscopy experiments. The floating DMPC bilayer spread from bicelles provides ideal conditions to incorporate transmembrane proteins.
双分子层囊泡是一种混合的盘状聚集体。制备了直径为11.8±0.2纳米的双分子层囊泡，其核心含有长链脂质（1,2 - 二肉豆蔻酰 - sn - 甘油 - 3 - 磷酸胆碱，DMPC），边缘形成部分含有短链脂质（1,2 - 二庚酰 - sn - 甘油 - 3 - 磷酸胆碱，DHPC）。储备双分子层囊泡溶液100倍稀释会破坏聚集体结构。在此条件下，双分子层囊泡铺展在修饰了金（111）表面的β - 硫代葡萄糖：6 - 巯基己酸单层上，形成独立的漂浮DMPC双层，而DHPC分子形成胶束并扩散到电解质溶液中。应用电化学阻抗谱、电化学控制石英晶体微天平以及偏振调制红外反射吸收光谱来探测漂浮DMPC双层的宏观性质和电位驱动的分子尺度变化。它们取决于膜电位的符号。膜电阻的高值（约2 MΩ·cm）表明形成了致密、无缺陷的双层。在负膜电位下，膜电阻和酰基链的倾斜度（膜的厚度）随电位呈线性变化，表明离子传导通过无缺陷的双层发生。向正膜电位转变会导致膜电阻突然降低以及酰基链倾斜。这些突然的重新取向导致在膜结构中形成缺陷，这在电化学阻抗谱实验中可以观察到。从双分子层囊泡铺展得到的漂浮DMPC双层为整合跨膜蛋白提供了理想条件。
