Role of intramolecular hydrogen bonds in promoting electron flow through amino acid and oligopeptide conjugates
Role of intramolecular hydrogen bonds in promoting electron flow through amino acid and oligopeptide conjugates
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DOI：
10.1073/pnas.2026462118
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发表时间：
2021-03
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通讯作者：
Rafał Orłowski;J. Clark;J. Derr;E. M. Espinoza;Maximilian F Mayther;O. Staszewska-Krajewska;J. Winkler;H. Jędrzejewska;A. Szumna;H. Gray;V. Vullev;D. Gryko
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作者：
Rafał Orłowski;J. Clark;J. Derr;E. M. Espinoza;Maximilian F Mayther;O. Staszewska-Krajewska;J. Winkler;H. Jędrzejewska;A. Szumna;H. Gray;V. Vullev;D. Gryko
意义远程电子转移遍及生物学、化学和工程学，因为它对于维持生命的过程、化学转化、能量转换以及电子和光子技术至关重要。阐明控制远程电子转移速率的因素仍然是一个突出的挑战，部分原因是介导这种过程的蛋白质和其他大分子结构的复杂性。我们已经发现，连接电子供体和受体的短肽可以假设折叠与分子内氢键相互作用，提供超快电荷转移的电子耦合途径。我们的工作将有助于设计有效的能量转换和存储的供体-受体系统。阐明相对柔性共轭物中控制电荷转移速率的因素对于理解生物学中的能量流动以及辅助电子器件的设计和构建具有重要意义。在这里，我们报告超快电子转移（ET）和空穴转移（HT）之间的一个咔咯（Cor）供体连接到一个二萘嵌苯二酰亚胺（PDI）受体的四聚体丙氨酸（Ala）4。供体和受体的选择性光激发触发亚皮秒和皮秒ET和HT。用单个丙氨酸或苯丙氨酸替换（Ala）4接头基本上不影响ET和HT动力学。我们推断，在这些反应中的电子耦合是不介导的四肽骨架，也不是由直接的供体-受体相互作用。采用NMR，圆二色性和计算研究的组合，我们表明，分子内氢键使供体和受体接近的“蝎子形”的分子结构，从而占异常高的ET和HT率。光诱导的电荷转移依赖于一个（Cor）NH. O=C-NH. O=C（PDI）电子耦合途径，该途径涉及两个关键氢键和一个中心酰胺基团作为介体。我们的工作为构建由长柔性桥连接的有效供体-受体组装体提供了指导方针，并为介导蛋白质中ET和HT的结构基序提供了见解。
Significance Long-range electron transfer pervades biology, chemistry, and engineering, as it is critical for life-sustaining processes, chemical transformations, energy conversion, as well as electronic and photonic technologies. Elucidating the factors that control the rates of long-range electron transfer remains an outstanding challenge, owing in part to the complexity of proteins and other macromolecular structures that mediate such processes. We have found that short peptides linking electron donors and acceptors can assume folds with intramolecular hydrogen bond interactions that provide electronic-coupling pathways for ultrafast charge transfer. Our work will assist designs of donor–acceptor systems for efficient energy conversion and storage. Elucidating the factors that control charge transfer rates in relatively flexible conjugates is of importance for understanding energy flows in biology as well as assisting the design and construction of electronic devices. Here, we report ultrafast electron transfer (ET) and hole transfer (HT) between a corrole (Cor) donor linked to a perylene-diimide (PDI) acceptor by a tetrameric alanine (Ala)4. Selective photoexcitation of the donor and acceptor triggers subpicosecond and picosecond ET and HT. Replacement of the (Ala)4 linker with either a single alanine or phenylalanine does not substantially affect the ET and HT kinetics. We infer that electronic coupling in these reactions is not mediated by tetrapeptide backbone nor by direct donor–acceptor interactions. Employing a combination of NMR, circular dichroism, and computational studies, we show that intramolecular hydrogen bonding brings the donor and the acceptor into proximity in a “scorpion-shaped” molecular architecture, thereby accounting for the unusually high ET and HT rates. Photoinduced charge transfer relies on a (Cor)NH…O=C–NH…O=C(PDI) electronic-coupling pathway involving two pivotal hydrogen bonds and a central amide group as a mediator. Our work provides guidelines for construction of effective donor–acceptor assemblies linked by long flexible bridges as well as insights into structural motifs for mediating ET and HT in proteins.