Polanco Ehider A, Opdam Laura V, Passerini Leonardo, Huber Martina, Bonnet Sylvestre, Pandit Anjali
Leiden Institute of Chemistry, Leiden University Einsteinweg 55 2333 CC Leiden The Netherlands
Department of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University Niels Bohrweg 2 2333 CA Leiden The Netherlands.
Chem Sci. 2024 Jan 30;15(10):3596-3609. doi: 10.1039/d3sc05870k. eCollection 2024 Mar 6.
In nature, light-driven water oxidation (WO) catalysis is performed by photosystem II the delicate interplay of different cofactors positioned in its protein scaffold. Artificial systems for homogeneous photocatalytic WO are based on small molecules that often have limited solubility in aqueous solutions. In this work, we alleviated this issue and present a cobalt-based WO-catalyst containing artificial metalloenzyme (ArM) that is active in light-driven, homogeneous WO catalysis in neutral-pH aqueous solutions. A haem-containing electron transfer protein, cytochrome B5 (CB5), served to host a first-row transition-metal-based WO catalyst, CoSalen (CoSalen, where HSalen = ,'-bis(salicylidene)ethylenediamine), thus producing an ArM capable of driving photocatalytic WO. The CoSalen ArM formed a water-soluble pre-catalyst in the presence of Ru(bpy) as photosensitizer and NaSO as the sacrificial electron acceptor, with photocatalytic activity similar to that of free CoSalen. During photocatalysis, the CoSalen-protein interactions were destabilized, and the protein partially unfolded. Rather than forming tens of nanometer sized CoO nanoparticles as free CoSalen does under photocatalytic WO conditions, the CB5 : CoSalen ArM showed limited protein cross-linking and remained soluble. We conclude that a weak, dynamic interaction between a soluble cobalt species and CB5 was formed, which generated a catalytically active adduct during photocatalysis. A detailed analysis was performed on protein stability and decomposition processes during the harsh oxidizing reaction conditions of WO, which will serve for the future design of WO ArMs with improved activity and stability.
在自然界中，光驱动水氧化（WO）催化是由光系统II通过位于其蛋白质支架中的不同辅因子之间的微妙相互作用来进行的。用于均相光催化WO的人工系统基于小分子，这些小分子在水溶液中的溶解度通常有限。在这项工作中，我们解决了这个问题，并提出了一种含钴的WO催化剂，该催化剂包含在中性pH值的水溶液中对光驱动的均相WO催化具有活性的人工金属酶（ArM）。一种含血红素的电子传递蛋白，细胞色素B5（CB5），用于容纳一种基于第一行过渡金属的WO催化剂，CoSalen（CoSalen，其中HSalen = ，'-双（水杨基亚甲基）乙二胺），从而产生一种能够驱动光催化WO的ArM。在Ru（bpy）作为光敏剂和NaSO作为牺牲电子受体的存在下，CoSalen ArM形成了一种水溶性预催化剂，其光催化活性与游离CoSalen相似。在光催化过程中，CoSalen与蛋白质的相互作用不稳定，蛋白质部分展开。与游离CoSalen在光催化WO条件下形成数十纳米大小的CoO纳米颗粒不同，CB5 : CoSalen ArM显示出有限的蛋白质交联并且保持可溶。我们得出结论，在可溶性钴物种和CB5之间形成了一种弱的、动态的相互作用，该相互作用在光催化过程中产生了一种催化活性加合物。对WO苛刻氧化反应条件下的蛋白质稳定性和分解过程进行了详细分析，这将为未来设计具有更高活性和稳定性的WO ArM提供参考。
