MCAA: New Models of Hydrogen Bonding in Iron-Sulfur Proteins

无机，生物无机和有机化学计划的这一奖项支持纽约大学的Marc Walters教授通过使用模型化合物来解决铁硫蛋白rubredoxin（Rd）和铁氧还蛋白（Fd）中的氢键作用。 在这些蛋白质中的铁硫电子转移位点的氢键的调制被认为对簇的氧化还原电位有重大影响。 N-H的影响S氢键的铁硫簇将检查与模型的高电子和结构的保真度，并通过使用表面修饰电极。 三套硫化铁簇合物将被合成为模型的Fd的X射线晶体学和X射线吸收边（XAS）的研究。 第一种由非极性抗衡离子组成。 第二个将与极性非氢键抗衡离子配对。 第三组将具有将复合物（受体）与抗衡离子（供体）连接的氢键。 氢键供体将包括仲或叔铵基团或带有侧链季铵基团的酰胺。 这些应该允许N-H的形成。S氢键的桥接硫化物配体。 金电极表面的化学修饰为研究阴离子电活性金属硫醇盐模型化合物中N-H.S氢键的氧化还原效应提供了一种新的途径。 电极表面将通过长链烷基硫醇盐分子的自组装单层（SAM）进行改性，所述长链烷基硫醇盐分子通过硫锚定到表面，并且在所连接的分子的末端位置具有酰胺基团。 在这种布置中，氧化还原循环将发生与富含酰胺的SAM接触的复合物，其被设计用于与分析物形成氢键。 酰胺末端自组装膜的使用将减少每种电化学研究中合成独特氢键供体配体的需要。 在这些实验中的成功将大大扩展我们的能力，以确定氢键诱导的氧化还原电位变化的各种Fe-S模型化合物，并可能导致工具的选择性检测溶液中的氧化还原活性物种。这项工作探讨了周围蛋白质对关键生物电子传递步骤中所涉及的金属簇的影响。 教育部分包括本科生、一名高中教师和一名高中生的参与。

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Marc Walters of New York University to address hydrogen bonding effects in the Fe-S proteins rubredoxin (Rd) and ferredoxin (Fd) through the use of model compounds. The modulation of hydrogen bonding to the iron sulfur electron-transfer sites in these proteins is thought to have a major influence on the redox potential of the clusters. The influence of N-H...S hydrogen bonds to iron-sulfur clusters will be examined with models of high electronic and structural fidelity and through the use of surface modified electrodes. Three sets of iron sulfide cluster complexes will be synthesized as models of Fd for X-ray crystallographic and X-ray absorption edge (XAS) studies. The first will consist of non-polar counterions. The second will be paired with polar non-hydrogen bonding counterions. A third set will have hydrogen bonds that link the complex (acceptor) to a counterion (donor). The hydrogen bond donors will include secondary or tertiary ammonium groups or amides bearing a pendant quaternary ammonium group. These should allow the formation of N-H...S hydrogen bonds to the bridging sulfide ligands. Chemically modified surfaces of gold electrodes will be employed as a new approach to study the redox effect of N-H.S hydrogen bonding in anionic electroactive metal thiolate model compounds. The electrode surface will be modified by a self-assembled monolayer (SAM) of long chain alkyl thiolate molecules anchored to the surface through sulfur and with amide groups at the terminal positions of the attached molecule. In this arrangement, redox cycling will occur for complexes that make contact with the amide-rich SAM, which is designed for hydrogen bond formation with the analyte. The use of amide terminal SAMs will obviate the need to synthesize unique hydrogen bonding donor ligands for each electrochemical study. Success in these experiments would greatly expand our ability to determine hydrogen bond induced redox potential shifts in a variety of Fe-S model compounds and possibly lead to tools for the selective detection of redox active species in solution. This work probes the effect of the surrounding protein on metal clusters involved in critical biological electron transport steps. The educational component includes participation by undergraduate students, a high school teacher and a high school student.