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

无机化学、生物无机化学和金属有机化学项目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研究铁-S蛋白质Rubredoxin(RD)和Ferredoxin(Fd)中的氢键效应。氢键对这些蛋白质中铁硫电子转移中心的调节被认为对簇的氧化还原电位有重要影响。N-H…S氢键对铁硫团簇的影响将通过高电子和结构保真度模型和表面修饰电极来考察。合成了三组硫化铁簇合物作为FD的模型，用于X射线结晶学和X射线吸收边(XAS)研究。第一个将由非极性反离子组成。第二个将与极性的非氢键反离子配对。第三组将具有氢键，将络合物(受体)与反离子(给体)连接起来。氢键给体将包括带有侧链季铵基团的仲铵基团或叔胺基团。这些都应该允许形成N-H…S氢键的桥联硫化物配体。化学修饰的金电极表面将成为研究阴离子电活性金属硫酸盐模型化合物中N-H-S氢键氧化还原效应的新途径。电极表面将由长链烷基硫醇分子自组装单分子膜(SAM)修饰，长链烷基硫醇分子通过硫磺固定在电极表面，并在附着分子的末端带有酰胺基团。在这种安排中，与富含酰胺的SAM接触的络合物将发生氧化还原循环，SAM旨在与分析物形成氢键。使用酰胺端自组装膜将不再需要为每一次电化学研究合成独特的氢键供体配体。这些实验的成功将极大地扩展我们测定各种Fe-S模型化合物中氢键诱导的氧化还原电位移动的能力，并可能导致选择性检测溶液中氧化还原活性物种的工具。这项工作探索了周围蛋白质对参与关键生物电子传递步骤的金属团簇的影响。教育部分包括本科生、高中教师和高中生的参与。

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.