EAGER: Iron-sulfide based Molecular-wires for Enhancing Charge Transport of Enzymatic Electrode Assemblies

知识价值：基于酶的电化学装置（如生物传感器和燃料电池）的整体有效性在很大程度上依赖于将酶附着在电极上的分子的能力，这些分子能够成功地从外部氧化点（酶活性位点）收集和运输电荷到内电极表面。目前的技术使用一系列辅助分子（带有正确的辅基）将必要的电子介质和酶复合物连接到电极表面。不幸的是，目前已知的有机系绳分子固有的低电导率使得电子传递过程受到高度限制；因此，有助于燃料电池的低功率密度和传感器的低灵敏度。缺乏一种有效的分子布线系统来允许无阻碍的电荷传输是一个重大问题，并且阻碍了利用生物电子设备所提供的巨大潜力。这项提议的总体目标是评估是否有可能用一个能够在辅酶和金属表面之间介导电子穿梭的单分子取代目前复杂的布线系统，并且有正确的假体基团同时锁住在金属表面和酶复合物上。受线粒体表面发生的自然电子传递机制的启发，我们假设葡萄糖脱氢酶-烟酰胺腺嘌呤二核苷酸（GDH-NAD）载酶辅酶系统可以通过合成铁硫[Fe-S]配合物直接附着在金电极上。众所周知，铁硫配合物在真核细胞中传输葡萄糖氧化产生的电子。其原理是，[Fe-S]配合物的巯基通过共价键附着在金表面上，而铁将与NAD的咪唑二嗪部分中的杂环氮原子配位，将酶辅酶配合物附着在电极上。假设将通过以下具体目标进行检验：1。评价通过[Fe-S]替代物将GDH-NAD+络合物拴在金电极上的有效性。这将通过合成简单形式的[Fe-S]配合物来完成，通过石英晶体微天平（QCM）研究评估将S端结合到Au电极上和将Fe端结合到NAD上的有效性，并通过电位计和电流传感原子力显微镜（CS-AFM）研究阐明开发的电极的电流-电压（CV）行为。阐明燃料氧化剂存在时电极表面发生的电化学现象。新型简化电极的电化学响应将与传统的有线电极在葡萄糖的存在下进行比较。研究的参数包括CV响应和燃料消耗/电极动力学。更广泛的影响和对EAGER资助项目的适当性：所提议的研究是高风险的，因为据我们所知，以前从未尝试过通过已知的替代物作为氧化还原介质将NAD直接附着在金属表面。如果成功，该研究将通过缓解阻碍有效生物电子器件发展的最复杂的瓶颈之一，即约束电荷传输，对生物电子学领域产生变革性影响。此外，如果成功的话，这项研究将为模拟电子传递链的第一步奠定基础，这反过来又可能使我们更接近于开发出最有效的发电厂——线粒体的合成版本！由于缺乏初步数据，这种性质的高风险提案不适合纳入常规提案。然而，这种水平的潜在高回报项目是一个？最适合的人选吗?对于一个渴望的人

1243311FernandoIntellectual Merit: The overall effectiveness of enzyme-based electrochemical devices such as biosensors and fuel cells are heavily dependent on the ability of the molecules that attach enzymes to the electrode to successfully harvest and transport charges from the outer oxidizing point (enzyme active-site) to the inner electrode surface. Current technology uses a series of ancillary molecules (with the correct prosthetic groups) to tether the essential electron mediator and the enzyme complex on to the surface of an electrode. Unfortunately, the inherently low conductivity of presently known organic tethering molecules makes the electron transport process highly constrained; therefore, contributing to fuel cells with low power density and sensors with low sensitivity. The lack of an effective molecular wiring system that can allow unimpeded charge transport is a significant problem and hinders harnessing the tremendous potential bioelectronics devices have to offer.The overall goal of this proposal is to evaluate whether it is possible to replace the current complex wiringsystem with a single molecule that has the ability to mediate electron shuttling between the coenzyme and a metal surface, and that has the correct prosthetic groups to latch simultaneously onto the metal surface and the enzyme complex.Inspired by the natural electron transport mechanism that occurs in the mitochondrial surface, we hypothesize that the glucose dehydrogenase-nicotinamide adenine dinucleotide (GDH-NAD) apoenzymecoenzyme system could be directly attached onto a gold electrode using synthetic iron-sulfur [Fe-S] complexes. Iron-sulfur complexes are well known to transport electrons generated by glucose oxidation in eukaryotic cells. The rationale is that the thiol groups of the [Fe-S] complex would attach onto the gold surface via covalent linkages while iron will coordinate with heterocyclic nitrogen atoms in imidazolediazine moieties of NAD attaching the apoenzyme-coenzyme complex on to the electrode.The hypothesis will be tested via the following Specific Objectives:1. Evaluate the effectiveness of tethering GDH-NAD+ complex onto a gold electrode via [Fe-S]surrogates. This will be done by synthesizing simple forms of [Fe-S] complexes, evaluating theeffectiveness of binding the S end onto the Au electrode and the Fe end to the NAD viaquartz crystal microbalance (QCM) studies, and elucidating the current-voltage (CV) behaviorof a developed electrode via potentiometric and current sensing atomic force microscopy(CS-AFM) studies.2. Elucidate electrochemical phenomena occurring at the electrode surface in the presence of thefuel oxidant. The electrochemical response of the novel simplified electrode will be compared with theconventionally wired electrode in the presence of glucose. The parameters studied willinclude CV response and fuel-consumption/electrode kinetics.Broader Impacts and the Appropriateness of the Project for EAGER Funding:The proposed research is high-risk since direct attachment of NAD to a metal surface via a surrogateknown to act as a redox mediator, to the best of our knowledge, has never been attempted before. Ifsuccessful, the research will provide a transformative impact on the bioelectronics area by alleviating oneof the most intricate bottlenecks impeding development of effective bio-electronic devices, i.e.,constrained charge transport. Moreover, if successful, this research will lay the foundation for mimickingthe first step of the electron transport chain which in turn may take us a step closer to developing asynthetic version of the most effective power plant known ?mitochondria!A high-risk proposition of this nature will not fit into a regular proposal due to lack of preliminary data.However, a potentially high-payoff project of this caliber is a ?good fit? for an EAGER