White Ryan J, Zhang Bo, Daniel Susan, Tang John M, Ervin Eric N, Cremer Paul S, White Henry S
Department of Chemistry, University of Utah, 315 S. 1400 E, Salt Lake City, Utah 84112, USA.
Langmuir. 2006 Dec 5;22(25):10777-83. doi: 10.1021/la061457a.
The in-plane ionic conductivity of the approximately 1-nm-thick aqueous layer separating a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer membrane and a glass support was investigated. The aqueous layer conductivity was measured by tip-dip deposition of a POPC bilayer onto the surface of a 20- to 75-microm-thick glass membrane containing a single conical-shaped nanopore and recording the current-voltage (i-V) behavior of the glass membrane nanopore/POPC bilayer structure. The steady-state current across the glass membrane passes through the nanopore (45-480 nm radius) and spreads radially outward within the aqueous layer between the glass support and bilayer. This aqueous layer corresponds to the dominant resistance of the glass membrane nanopore/POPC bilayer structure. Fluorescence recovery after photobleaching measurements using dye-labeled lipids verified that the POPC bilayer maintains a significant degree of fluidity on the glass membrane. The slopes of ohmic i-V curves yield an aqueous layer conductivity of (3 +/- 1) x 10(-3) Omega(-1) cm(-1) assuming a layer thickness of 1.0 nm. This conductivity is essentially independent of the concentration of KCl in the bulk solution (10-4 to 1 M) in contact with the membrane. The results indicate that the concentration and mobility of charge carriers in the aqueous layer between the glass support and bilayer are largely determined by the local structure of the glass/water/bilayer interface.
研究了分隔1-棕榈酰-2-油酰基-sn-甘油-3-磷酸胆碱（POPC）双层膜与玻璃支撑体的约1纳米厚水层的面内离子电导率。通过将POPC双层膜尖端浸涂到含有单个锥形纳米孔的20至75微米厚玻璃膜表面，并记录玻璃膜纳米孔/POPC双层结构的电流-电压（i-V）行为，来测量水层电导率。穿过玻璃膜的稳态电流通过纳米孔（半径45 - 480纳米），并在玻璃支撑体与双层膜之间的水层中径向向外扩散。该水层对应于玻璃膜纳米孔/POPC双层结构的主要电阻。使用染料标记脂质的光漂白后荧光恢复测量证实，POPC双层膜在玻璃膜上保持了显著程度的流动性。假设层厚度为1.0纳米，欧姆i-V曲线的斜率得出水层电导率为(3±1)×10⁻³Ω⁻¹cm⁻¹。该电导率基本上与与膜接触的本体溶液（10⁻⁴至1 M）中KCl的浓度无关。结果表明，玻璃支撑体与双层膜之间水层中电荷载流子的浓度和迁移率在很大程度上由玻璃/水/双层膜界面的局部结构决定。
