Nanoscale Function Group, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland.
Langmuir. 2011 Apr 5;27(7):3749-53. doi: 10.1021/la104640v. Epub 2011 Mar 3.
Supported dipalmitoylphosphatidylcholine (DPPC) bilayers are widely used membrane systems in biophysical and biochemical studies. Previously, short-range positional and orientational order of lipid headgroups of supported DPPC bilayers was observed at room temperature using low deflection noise frequency modulation atomic force microscopy (FM-AFM). While this ordering was supported by X-ray diffraction studies, it conflicted with diffusion coefficient measurements of gel-phase bilayers determined from fluorescence photobleaching experiments. In this work, we have directly imaged mica-supported DPPC bilayers with submolecular resolution over scan ranges up to 146 nm using low deflection noise FM-AFM. Both orientational and positional molecular ordering were observed in the mesoscale, indicative of crystalline order. We discuss these results in relation to previous biophysical studies and propose that the mica support induces mesoscopic crystalline order of the DPPC bilayer at room temperature. This study also demonstrates the recent advance in the scan range of submolecular scale AFM imaging.
支持的二棕榈酰磷脂酰胆碱 (DPPC) 双层膜在生物物理和生化研究中被广泛应用。此前，使用低偏折噪声频率调制原子力显微镜 (FM-AFM) 在室温下观察到支持的 DPPC 双层膜中脂质头部基团的短程位置和取向有序。虽然这种有序性得到了 X 射线衍射研究的支持，但它与荧光漂白实验确定的凝胶相双层扩散系数测量结果相冲突。在这项工作中，我们使用低偏折噪声 FM-AFM 直接以 submolecular 分辨率对云母支持的 DPPC 双层膜进行成像，扫描范围高达 146nm。在介观尺度上观察到了取向和位置分子的有序性，表明存在结晶有序。我们将这些结果与以前的生物物理研究进行了讨论，并提出云母支撑在室温下诱导 DPPC 双层膜的介观结晶有序。这项研究还展示了 submolecular 尺度 AFM 成像扫描范围的最新进展。
