New Materials for Coupling Electron and Ion Transfer Across Model Archaebacterial Membranes

9319099 Thompson基于平面细菌视紫红质薄膜的光电开关和存储器件的开发一直是国际上密集的研究努力的焦点。在需要快速存储具有长存储寿命(1ms)的高密度光学信息的各种模式识别系统中，可以预见这些设备的使用。尽管利用细菌视紫红质的器件原型已经实现了这一点，但其设计受到多激发态的稳定性、光物理和吸收特性的限制，以及平面阵列中细菌视紫红质的方向控制不佳。这项研究的目的是合成和表征一类新型材料，该材料将在取向薄膜中耦合光化学诱导的电子和离子传输反应，用于光电子器件。将这些材料固定在光学透明的电极表面上，将在这些材料中提供一定程度的光化学和电化学可调谐性，这是目前基于细菌素的器件所缺乏的。根据光合作用细菌和植物的膜结合反应中心的概念，合成了%Gramicidin A-卟啉-醌(GAPQ)三联体，并将其加入到由模型古细菌双极膜脂(Bolalipid)组成的囊泡中。这些材料将通过以下方式在复合三联体/牛脂肪脂光化学体系中相辅相成：1)在膜内定向卟啉和苯二酚，形成具有氧化和还原表面的不对称膜结构；2)通过在相对的膜界面放置末端供体和受体部分来抑制初始电荷分离对的自湮灭；3)通过减小供体-受体分离距离来提高跨膜电子转移的速率；以及4)通过引入单价离子通道来补偿跨膜电子转移引起的膜极化，以消除电位梯度的积累。这项建议描述了制备化学，结构和光化学表征，以及钠离子电导测量，目的是优化双极类脂膜的矢量电子和离子转移速率。该提案的材料方面侧重于开发模块化的Bolalipid和GAPQ合成途径，以便能够实现界面反应、有效的跨膜电荷分离和固体载体材料的固定化的系统集成。利用激光闪光光解、差示扫描量热、核磁共振和电子显微镜等技术，对不同构型的GAPQ/Bolalipid复合膜中的三联体取向、离子通道特性、光化学动力学和电子/离子耦合进行了实验研究。这些研究的结果将被用来设计一种适合在微孔和ITO载体上进行测试的系统。***

9319099 Thompson The development of optoelectronic switching and storage devices based on planar bacteriorhodopsin films has been the focus of intense international research efforts. Utilization of these devices is envisioned in a variety of pattern recognition systems where rapid storage of high densities of optical information with long storage lifetimes ( 1 ms) is required. Although device prototypes using bacteriorhopsin have been built that achieve this, their design is limited by the stability, photophysical and absorption characteristics of the multiple excited states, and poor directional control of bacteriorhdopsin in planar arrays. The objective of the proposed research is to synthesize and characterize a new class of materials that will couple photochemically induced electron and ion transport reactions in oriented, thin membrane films for application in optoelectronic devices. Immobilization of these materials onto optically transparent electrode surfaces will provide a degree of photochemical and electrochemical tunability in these materials that is currently lacking in the bacteriorhopsin-based devices. %%% Gramicidin A-porphyrin-quinone (GAPQ triads, patterned in concept after the membrane-bound reaction centers of photosynthetic bacteria and plants, will be synthesized and incorporated into vesicles composed of model archaebacterial bipolar membrane lipids (bolalipids). These materials will complement each other in a composite triad/bolalipid photochemical system by: 1) vectorially orienting the porphyrin and quinone within the membrane to produce an asymmetric membrane structure having both oxidizing and reducing surfaces, 2) inhibiting self-annihilation of the initially charge- separated pair by placing terminal donor and acceptor moieties at opposing membrane interfaces, 3) increasing the rate of transmembrane electron transfer by reducing the donor-acceptor separation distance, and 4) compensating for membrane polarization resulting fro m transmembrane electron transfer by incorporating a monovalent ion channel to dissipate the buildup of potential gradients. This proposal describes preparative chemistry, structural and photochemical characterization, and sodium ion conductance measurements aimed at optimizing vectorial electron and ion transfer rates across bipolar lipid membranes. The materials aspects of the proposal are focused on developing modular bolalipid and GAPQ synthetic pathways such that facile system integration with respect to interfacial reactivity, efficient transmembrane charge separation, and immobilization on solid support materials can be achieved. Experiments designed to probe the triad orientation, ion channel properties, photochemical kinetics, and electron/ion coupling in various GAPQ/bolalipid composite membrane configurations using laser flash photolysis, differential scanning calorimetry, nuclear magnetic resonance, and electron microscopy techniques are also proposed. The results of these investigations will then be used to devise a suitable system for testing on microporous and ITO supports. ***