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

1243311 Fernando Intelligence优点：生物传感器和燃料电池等基于酶的电化学设备的整体效率在很大程度上取决于将酶连接到电极上的分子成功收集电荷并将电荷从外部氧化点(酶活性部位)传输到电极内表面的能力。目前的技术使用一系列辅助分子(带有正确的假体基团)将基本的电子介体和酶复合体连接到电极表面。不幸的是，目前已知的有机系链分子固有的低电导率使得电子传输过程受到高度限制；因此，有助于制造低功率密度的燃料电池和低灵敏度的传感器。缺乏有效的分子布线系统允许畅通无阻的电荷传输是一个严重的问题，并阻碍了利用必须提供的巨大潜力的生物电子器件。这项提议的总体目标是评估是否有可能用单个分子取代目前复杂的布线系统，该分子具有在辅酶和金属表面之间介导电子穿梭的能力，并且具有正确的假体基团来同时锁存到金属表面和酶复合体上。受发生在线粒体表面的自然电子传输机制的启发，我们假设葡萄糖脱氢酶-烟酰胺腺嘌呤二核苷酸脱氢酶体系可以用合成的铁-硫[Fe-S]络合物直接连接到金电极上。铁硫络合物在真核细胞中传输葡萄糖氧化产生的电子是众所周知的。其基本原理是，[Fe-S]络合物的硫醇基团通过共价键连接到金表面，而铁将与脱辅酶-辅酶络合物连接在电极上的NAD的咪唑二氮基团中的杂环氮原子配位。这将通过合成简单形式的[Fe-S]络合物，通过石英晶体微天平研究评估S端结合到金电极上和铁端结合到NAD电极上的有效性，并通过电位和电流敏感原子力显微镜研究来阐明所开发电极的电流-电压(CV)行为。阐明在燃料氧化剂存在下电极表面发生的电化学现象。将新型简化电极在葡萄糖存在下的电化学响应与传统金属丝电极进行了比较。研究的参数将包括循环伏安响应和燃料消耗/电极动力学。广泛的影响和该项目是否适合紧急资助：拟议的研究是高风险的，因为据我们所知，通过作为氧化还原介体的替代物将NAD直接连接到金属表面之前从未尝试过。如果成功，这项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，即受限的电荷传输，对生物电子领域产生革命性的影响。此外，如果成功，这项研究将为模仿电子传输链的第一步奠定基础，这反过来可能使我们更接近于开发已知的最有效发电厂的合成版本？线粒体！由于缺乏初步数据，这种性质的高风险命题将不适合常规方案。然而，这种口径的潜在高回报项目是？好的适合？对于一个热切的

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