Synthesis and Spectroscopy of Ferric Superoxo Models for Non-Heme Enzyme Intermediates

 描述（由申请人提供）：非血红素含铁加氧酶参与各种重要的生物医学过程，包括抗生素（包括氯生霉素和青霉素）的生物合成、脱氧核糖核苷酸（DNA的关键结构单元）的产生以及铁的储存以防止破坏性的芬顿型化学（通过铁蛋白的亚铁氧化酶位点）。了解加氧酶如何使用活化的铁氧物种进行这些转化是至关重要的。尽管对铁-氧代和铁-过氧物种的作用进行了大量的研究，但已知的光谱可获得的铁-超氧代化合物却很少。这是令人惊讶的，因为铁超氧物种被提议作为几乎每一种非血红素含铁加氧酶的催化循环中的早期中间体。该建议的目标是产生光谱上易处理的Fe（III）-与非血红素含铁加氧酶相关的超氧物种。这将通过开发单核非血红素Fe（III）-superoxo物种的合成方法来实现。我们假设，通过适当的反应条件和配体设计特征（包括配体碱度，空间体积和氢键供体能力）的组合，我们将能够产生第一个合成的单核非血红素Fe（III）-superoxo物种。我们也将采用类似的设计原则，以生成Fe（III）-superoxo化合物从双核前体含有一个Fe（II）中心。合成的Fe（III）-超氧化合物将通过各种光谱方法进行全面表征，包括UV-vis，XAS，共振拉曼，EPR和穆斯堡尔光谱。这将允许建立一个初级和次级配位球功能的化合物的铁superoxo物种的结构和电子特征之间的关系的理解。到目前为止，还没有一种非血红素铁超氧化合物被拉曼、EPR和穆斯堡尔谱的组合完全表征，这是对该领域理解的一个重大空白。事实上，只有一种这样的超氧化合物被共振拉曼表征，并且1310 cm-1的超氧-O伸缩频率与其他已知的超氧化合物（1043 - 1207 cm-1）相比高得令人不安。合成的Fe（III）-superoxo化合物的反应性也将进行探索，以建立一个反应性的关系，电子和结构参数。总的来说，这项研究有可能是变革性的，以了解超氧化物中间体在非血红素含铁加氧酶领域的作用。

 DESCRIPTION (provided by applicant): Non-heme, iron-containing oxygenases are involved in various biomedically important processes, including the biosynthesis of antibiotics (including chlorobiocin and penicillin), the generation of deoxyribonucleotides (key building blocks of DNA), and the storage of iron to prevent damaging Fenton-type chemistry (via the ferroxidase site of ferritin). Understanding how oxygenases use activated iron-oxygen species to carry out these transformations is of paramount importance. Despite the wealth of studies on the role of iron-oxo and iron-peroxo species, there is a paucity of spectroscopically accessible iron-superoxo compounds known. This is surprising given that iron-superoxo species are proposed as early intermediates in the catalytic cycles of almost every non-heme iron-containing oxygenase enzyme. The goal of this proposal is to generate spectroscopically tractable Fe(III)-superoxo species of relevance to non-heme iron-containing oxygenases. This will be accomplished by developing a synthetic methodology for mononuclear non-heme Fe(III)-superoxo species. We hypothesize that by appropriate combination of reaction conditions and ligand design features (including ligand basicity, steric bulk and hydrogen bond donor ability) we will be able to generate the first synthetic mononuclear non-heme Fe(III)-superoxo species. We will also apply similar design principles to the generation of Fe(III)-superoxo compounds from dinuclear precursors containing a Fe(II) center. The synthetic Fe(III)-superoxo compounds will be comprehensively characterized by a variety of spectroscopic methods including UV-vis, XAS, resonance Raman, EPR, and Mössbauer spectroscopy. This will allow the establishment of an understanding of the relationship between primary- and secondary- coordination sphere features of the compounds to the structural and electronic features of iron-superoxo species. To date no non-heme iron-superoxo compound has been fully characterized by a combination of Raman, EPR and Mössbauer spectroscopy, and this is a significant gap in understanding for the field. In fact, only a single such superoxo compound has been characterized by resonance Raman, and the O-O stretching frequency of 1310 cm-1 is anomalously high compared to other known superoxide compounds (1043-1207 cm-1). The reactivity of the synthesized Fe(III)-superoxo compounds will also be explored in order to establish a reactivity relationship to electronic and structural parameters. Overall, this research has the potential to be transformative to understanding the role of superoxide intermediates in the field of non-heme iron-containing oxygenases.