Universitat Politècnica de Catalunya, Dpt. Enginyeria Química, 08222 Terrassa (Barcelona), Spain.
J Phys Chem B. 2013 Jun 27;117(25):7498-506. doi: 10.1021/jp4004517. Epub 2013 Jun 13.
Ubiquinone (UQ) is one of the main electron and proton shuttle molecules in biological systems, and dipalmitoylphosphatidylcholine (DPPC) is one of the most used model lipids. Supported planar bilayers (SPBs) are extensively accepted as biological model membranes. In this study, SPBs have been deposited on ITO, which is a semiconductor with good electrical and optical features. Specifically, topographic atomic force microscopy (AFM) images and force curves have been performed on SPBs with several DPPC:UQ ratios to study the location and the interaction of UQ in the SPB. Additionally, cyclic voltammetry has been used to understand the electrochemical behavior of DPPC:UQ SPBs. Obtained results show that, in our case, UQ is placed in two main different positions in SPBs. First, between the DPPC hydrophobic chains, fact that originates a decrease in the breakthrough force of the bilayer, and the second between the two leaflets that form the SPBs. This second position occurs when increasing the UQ content, fact that eventually forms UQ aggregates at high concentrations. The formation of aggregates produces an expansion of the SPB average height and a bimodal distribution of the breakthrough force. The voltammetric response of UQ depends on its position on the bilayer.
泛醌（UQ）是生物系统中主要的电子和质子穿梭分子之一，二棕榈酰磷脂酰胆碱（DPPC）是最常用的模型脂质之一。支持的平面双层（SPB）被广泛认为是生物模型膜。在这项研究中，SPB 沉积在具有良好电学和光学特性的半导体 ITO 上。具体来说，对具有不同 DPPC：UQ 比例的 SPB 进行了形貌原子力显微镜（AFM）图像和力曲线测量，以研究 UQ 在 SPB 中的位置和相互作用。此外，还使用循环伏安法来了解 DPPC：UQ SPB 的电化学行为。得到的结果表明，在我们的情况下，UQ 位于 SPB 中的两个主要不同位置。首先，在 DPPC 疏水链之间，这导致双层的突破力下降，其次是形成 SPB 的两个叶层之间。当 UQ 含量增加时，会出现第二个位置，最终在高浓度时形成 UQ 聚集体。聚集体的形成导致 SPB 平均高度的膨胀和突破力的双峰分布。UQ 的伏安响应取决于其在双层中的位置。
