Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA.
ChemSusChem. 2021 May 20;14(10):2237-2246. doi: 10.1002/cssc.202100122. Epub 2021 Apr 28.
Hydrogenase enzymes produce H gas, which can be a potential source of alternative energy. Inspired by the [NiFe] hydrogenases, we report the construction of a de novo-designed artificial hydrogenase (ArH). The ArH is a dimeric coiled coil where two cysteine (Cys) residues are introduced at tandem a/d positions of a heptad to create a tetrathiolato Ni binding site. Spectroscopic studies show that Ni binding significantly stabilizes the peptide producing electronic transitions characteristic of Ni-thiolate proteins. The ArH produces H photocatalytically, demonstrating a bell-shaped pH-dependence on activity. Fluorescence lifetimes and transient absorption spectroscopic studies are undertaken to elucidate the nature of pH-dependence, and to monitor the reaction kinetics of the photochemical processes. pH titrations are employed to determine the role of protonated Cys on reactivity. Through combining these results, a fine balance is found between solution acidity and the electron transfer steps. This balance is critical to maximize the production of Ni -peptide and protonation of the Ni -H intermediate (Ni-R) by a Cys (pK ≈6.4) to produce H .
氢化酶酶产生 H 气体，这可能是替代能源的潜在来源。受 [NiFe] 氢化酶的启发，我们报告了一种全新设计的人工氢化酶（ArH）的构建。ArH 是一个二聚体螺旋线圈，其中两个半胱氨酸（Cys）残基被引入串联的 a/d 位置的七肽中，以创建四硫代镍结合位点。光谱研究表明，镍结合显著稳定了产生与镍-硫醇蛋白特征电子跃迁的肽。ArH 光催化产生 H，表现出对活性的 pH 值依赖性呈钟形。荧光寿命和瞬态吸收光谱研究用于阐明 pH 值依赖性的性质，并监测光化学过程的反应动力学。pH 滴定用于确定质子化 Cys 在反应性方面的作用。通过结合这些结果，在溶液酸度和电子转移步骤之间找到了一个很好的平衡。这种平衡对于通过 Cys（pK ≈6.4）最大限度地产生 Ni-肽和 Ni-H 中间物（Ni-R）的质子化以产生 H 至关重要。
