Scanning Conductance Probe Microscope for Chemical Mapping

我们建议建立一个带有导电尖端的原子力显微镜，以确定电活性分子跨越绝缘脂质膜的位置。该显微镜将能够检测几飞安的电流，并将在环境和温度（80-300K）控制下工作。Mazur和Hipps最近的研究表明，导电部位的电流-电压特性与电活性分子的氧化还原化学有关，我们建议使用表征良好的卟啉链烷硫醇分子组合来研究这一现象，目的是区分单个有机分子。低温操作将用于控制离子电流（如水层中不必要的表面传导）和使软样品变硬（导致更高的AFM分辨率）。我们的最终目标是开发一种新的空间映射工具，用于研究跨细胞膜的电子和离子过程。我们将研究的第一个生物样本将是来自绿红假单胞菌的光合反应中心的良好表征（和高度有序）阵列。我们希望能够鉴定细胞色素bcl复合物并确定其在膜中的空间分布。

We propose to build an atomic force microscope with a conducting tip to identify sites where electroactive molecules span an otherwise insulating lipid membrane. The microscope will be capable of detecting currents of a few femtoamps, and will operate under environmental and temperature (80-300K) control. Recent work by Mazur and Hipps indicates that the current-voltage characteristics at conductive sites are related to the redox chemistry of the electroactive molecules and we propose to study this phenomenon using well-characterized molecular assemblies of porphyrin-linked alkanethiols with the goal of distinguishing individual organic molecules. Operation at low temperatures will be used to control ion currents (such as unwanted surface conduction in a water layer) and to stiffen soft samples (leading to higher AFM resolution). Our ultimate goal is to develop a new spatial-mapping tool for studying electronic and ionic processes across cell membranes. The first biological sample we will study will be the well characterized (and highly ordered) arrays of the photosynthetic reaction center from Rhodopseudomonas viridis. We hope to be able to identify the cytochrome bcl complexes and determine their spatial distribution in the membrane.