Sulfido dithiolene complexes modeling molybdenum and tungsten dependent oxiodreductases - investigating synthesis, catalysis and biological activity to elucidate structural uncertainties, structure-function relationships and biosynthesis

铁硫簇对必需的钼和钨氧化还原酶的生物合成和功能至关重要。关键方面将研究钼和钨辅因子的成熟和催化活性，直接依赖于FeS簇蛋白（关键词：串扰）。通过化学模型合成、光谱表征、催化和动力学评价以及与蛋白质（分子伴侣/脱辅基酶）的生物相互作用，将有助于更好地理解相应的酶及其协同作用。重要的问题特别关注硫基配体在Mo和W活性位点中的作用，其通过IscS在体内引入/转移。特别是，将在模型化合物上对硫代配位及其对酶反应性的作用进行化学研究。将阐明催化机制，并使用所有的分析结果，以胜任区分实际和人为存在的这种硫配体在活性位点的相应的酶（在其中一些它的存在是不明确的）。同位素标记模型复合物中的硫基配体的选择性将进一步各自所需的洞察力。高度发达的配体系统，最近被证明可以诱导与天然蛋白质的结合，将在这种情况下产生重大影响，并进一步了解细胞过程;特别是硫转移和插入，这与二硫杂环戊烯衍生的多蝶呤（MPT）配体和硫代配位特别相关。模拟天然MPT的各个方面的钼（和钨）的复杂的单氧化双二硫杂环戊烯络合物应通过将硫基（=S）交换为氧化（=O）连接来进行修饰，其中双羰基前体的应用被确定为最可行的程序。电化学氧化和SH-离子的伴随存在下，将被调查的MVIOS物种的合成。叠氮二硫纶钼配合物的合成构成另一个重要目标。这种配合物是阐明钼依赖性大肠杆菌抑制作用所必需的。大肠杆菌甲酸脱氢酶（FDH）通过比较酶和模型复杂的光谱数据。作为酶产物CO2的等电子体，叠氮化物与蛋白质的结合将有助于理解FDH的反应机制，这又对CO2化学有影响。全面表征所有合成的配合物光谱，研究其催化潜力和动力学的反应，再加上调查其生物活性将提供深入了解自然的战略，以促进反应性和伴随的稳定性。将通过研究与参与钼或钨辅因子成熟的蛋白质的特异性结合以及与脱辅基酶的特异性结合和相应半合成酶的催化活性来评估生物活性。

Iron-sulfur cluster are critically important for the biosynthesis and function of essential molybdenum and tungsten oxidoreductases. Crucial aspects will be investigated of the maturation and catalytic activity of molybdenum and tungsten co-factors, being directly dependent on FeS cluster proteins (keyword: crosstalk). A better understanding of the respective enzymes and their synergy shall be facilitated by chemical model syntheses, spectroscopic characterization, catalytic and kinetic evaluation and the biological interaction with proteins (chaperones/apo-enzymes). Important issues specifically concern the role of the sulfido ligand in the Mo and W active sites, which is introduced/transferred in vivo by IscS. Sulfido coordination and its function for the enzymes’ reactivity in particular, will be chemically studied on model compounds. The catalytic mechanisms will be elucidated and all analytical results used to competently discriminate between actual and artefactual presence of this sulfido ligand in the active sites of respective enzymes (in some of which its presence being not unambiguously clear). Isotopically labelling the sulfido ligand in model complexes selectively will further the respective required insight. Highly developed ligand systems, having recently been shown to induce binding to natural proteins, will have significant impact in this context and further the understanding of cellular processes; in particular of sulfur transfer and insertion, which is specifically relevant for the dithiolene-derived molybdopterin (MPT) ligands and sulfido coordination. Sophisticated mono-oxido bis-dithiolene complexes of molybdenum (and tungsten), mimicking various aspects of natural MPT, shall be modified by exchanging sulfido (=S) for oxido (=O) ligation for which the application of bis-carbonyl precursors was established as the most feasible procedure. Electrochemical oxidation and the concomitant presence of SH– ions will be investigated for the synthesis of MVIOS species. The synthesis of azide dithiolene molybdenum complexes constitutes another important aim. Such complexes are needed for elucidating the inhibition of Mo-dependent E. coli formate dehydrogenase (FDH) by comparison of enzymatic and model complex spectroscopic data. Being isoelectronic to the enzymatic product CO2, azide binding to protein will serve the understanding of FDH’s reaction mechanism, which again has implications for CO2 chemistry. Comprehensively characterising all synthesised complexes spectroscopically, studying their catalytic potential and the kinetics of such reactions plus investigating their biological activity will provide intimate insight into nature’s strategies to foster reactivity and concomitant stability. The biological activity will be assessed by investigating specific binding to proteins, which participate in molybdenum or tungsten cofactor maturation, as well as to apoenzymes and the catalytic activity of respective semi-synthetic enzymes.