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

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研究的热点。这些器件的利用被设想在各种模式识别系统中，其中需要长存储寿命（1ms）的高密度光学信息的快速存储。虽然已经建立了使用细菌紫质实现这一目标的设备原型，但它们的设计受到多种激发态的稳定性、光物理和吸收特性以及细菌紫质在平面阵列中方向性控制差的限制。该研究的目的是合成和表征一类新的材料，将光化学诱导的电子和离子输运反应耦合到取向薄膜薄膜中，用于光电器件。将这些材料固定在光学透明的电极表面上，将为这些材料提供一定程度的光化学和电化学可调性，这是目前基于细菌蛋白的设备所缺乏的。Gramicidin a -卟啉-醌（GAPQ triads）将被合成并整合到由模型古细菌双极性膜脂（bolaliids）组成的囊泡中。GAPQ triads的概念来源于光合细菌和植物的膜结合反应中心。这些材料将通过以下方式在三元/脂质复合光化学系统中相互补充：1)向膜内的卟啉和醌定向，产生具有氧化和还原表面的不对称膜结构；2)通过将末端供体和受体部分放置在相反的膜界面上，抑制最初电荷分离对的自湮灭；3)通过减少供体和受体的分离距离，增加跨膜电子转移的速率。4)通过引入单价离子通道来消除电位梯度的累积，补偿由跨膜电子转移引起的膜极化。本提案描述了制备化学，结构和光化学表征，以及旨在优化双极脂质膜矢量电子和离子转移速率的钠离子电导测量。该提案的材料方面侧重于开发模块化bolali脂和GAPQ合成途径，以便在界面反应性、有效的跨膜电荷分离和固体支撑材料上的固定化方面实现系统集成。本文还提出了利用激光闪光光解、差示扫描量热法、核磁共振和电子显微镜技术来探测各种GAPQ/ bol脂复合膜构型中的三元取向、离子通道性质、光化学动力学和电子/离子耦合的实验。这些调查的结果将用于设计一个合适的系统测试微孔和ITO支撑。＊＊＊

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. ***