Modular design of a bioinspired tandem cell for direct solar-to-fuel conversion (Solarfueltandem)

所有的化石燃料都是通过光合作用从阳光中提取的。为了科普化石燃料的有限供应，人类还必须学会利用阳光来产生燃料。在自然界中，光系统II利用阳光将水氧化成氧气和等同的氢气，后者用于将二氧化碳还原成有机糖。这种困难的氧化反应发生在PSII复合物中的一个不寻常的CaMn 4发光处，称为氧气释放中心（OEC）。我们建议通过在允许金属簇结合的侧链中引入变化来模拟OEC在另一种“支架”蛋白中的组装。将OEC组装在一个合适的“智能”矩阵中，可以适当地处理水氧化产生的质子，这是构建人工光合系统的关键先决条件。基质保护催化簇免受本体溶剂的影响，控制簇的精确环境，并快速地将质子从簇穿梭到溶剂。已经使用内部计算机程序SITEGRAFT进行了初步的支架设计，该程序搜索将产生氨基酸官能团位置的靶星座的位点周围的突变。该程序也可应用于其它活性部位的设计问题。 我们计划使用四螺旋束二铁羧酸盐蛋白作为支架，因为这些蛋白已经有一个埋藏的双金属中心，因此只需要微小的变化就可以容纳稍大的簇。该簇可以用化学氧化组装，并与具有电荷分离基序的捕光颜料偶联，以产生具有足够氧化还原电位的空穴（人工反应中心）来驱动水氧化。合适的颜料包括锌-卟啉和钌联吡啶络合物。除了这种“自上而下”的方法外，我们还将研究将类似OEC的簇合并到比模型蛋白更简单的较小蛋白质模型中

All fossil fuels are derived from sunlight via photosynthesis. To cope with the finite supply of fossil fuels, humanity must also learn to use sunlight to generate fuel. In nature photosystem II uses sunlight to oxidise water to oxygen, and equivalents of hydrogen, which are used to reduce CO2 to organic sugars. This difficult oxidation reaction takes place at an unusual CaMn4 metallocluster in the PSII complex, called the oxygen evolving centre (OEC). We propose to mimic the assembly of the OEC in another "scaffold" protein, by introducing variations in the side chains that will allow a metal cluster to bind. Assembling an OEC in a suitable "smart" matrix that can deal appropriately with the protons generated by water oxidation, is a crucial prerequisite to building an artificial photosynthetic system. The matrix protects the catalytic cluster from bulk solvent, controls the precise environment of the cluster, and rapidly shuttles protons from the cluster to the solvent. Preliminary scaffold designs have been made using an in-house computer program, SITEGRAFT, which searches for mutations around a site that will generate a target constellation of amino acid functional group positions. This program could also be applied to other active-site design problems. We plan on using four-helix bundle di-iron carboxylate proteins as scaffolds, as these already have a buried dimetal centre, and so should need only minor changes to accommodate a slightly larger cluster. The cluster can be assembled with chemical oxidation, and coupled to light-harvesting pigments with a charge separation motif incorporated to generate a hole with sufficient redox potential (artificial reaction centre) to drive water oxidation. Suitable pigments include zinc-porphyrins, and ruthenium bypyridine complexes. As well as this "top-down" approach, we will also investigate the incorporation of an OEC-like cluster into smaller protein maquettes, which are simpler than model proteins