Enzyme-Triggered Defined Protein Nanoarrays: Efficient Light-Harvesting Systems to Mimic Chloroplasts

The elegance and efficiency by which chloroplasts harvest solar energy and conduct energy transfer have been a source of inspiration for chemists to mimic such process. However, precise manipulation to obtain orderly arranged antenna chromophores in constructing artificial chloroplast mimics was a great challenge, especially from the structural similarity and bioaffinity standpoints. Here we reported a design strategy that combined covalent and noncovalent interactions to prepare a protein-based light-harvesting system to mimic chloroplasts. Cricoid stable protein one (SP1) was utilized as a building block model. Under enzyme-triggered covalent protein assembly, mutant SP1 with tyrosine (Tyr) residues at the designated sites can couple together to form nanostructures. Through controlling the Tyr sites on the protein surface, we can manipulate the assembly orientation to respectively generate 1D nanotubes and 2D nanosheets. The excellent stability endowed the self-assembled protein architectures with promising applications. We further integrated quantum dots (QDs) possessing optical and electronic properties with the 2D nanosheets to fabricate chloroplast mimics. By attaching different sized QDs as donor and acceptor chromophores to the negatively charged surface of SP1-based protein nanosheets via electrostatic interactions, we successfully developed an artificial light-harvesting system. The assembled protein nanosheets structurally resembled the natural thylakoids, and the QDs can achieve pronounced FRET phenomenon just like the chlorophylls. Therefore, the coassembled system was meaningful to explore the photosynthetic process in vitro, as it was designed to mimic the natural chloroplast.

叶绿体收集太阳能和进行能量转移的优雅和高效一直是化学家模仿这一过程的灵感来源。然而，在构建人工叶绿体模拟物时精确操作以获得有序排列的天线发色团是一个巨大的挑战，特别是从结构相似性和生物亲和性的角度来看。在这里，我们报告了一种设计策略，结合共价和非共价相互作用来制备基于蛋白质的光捕获系统来模拟叶绿体。环状软骨稳定蛋白一 (SP1) 被用作构建块模型。在酶触发的共价蛋白组装下，在指定位点具有酪氨酸 (Tyr) 残基的突变体 SP1 可以偶联在一起形成纳米结构。通过控制蛋白质表面的Tyr位点，我们可以操纵组装方向，分别生成一维纳米管和二维纳米片。优异的稳定性赋予自组装蛋白质结构具有广阔的应用前景。我们进一步将具有光学和电子特性的量子点（QD）与二维纳米片集成，以制造叶绿体模拟物。通过静电相互作用将不同大小的量子点作为供体和受体发色团附着到基于 SP1 的蛋白质纳米片带负电的表面，我们成功开发了一种人工光捕获系统。组装的蛋白质纳米片在结构上类似于天然类囊体，并且量子点可以像叶绿素一样实现明显的 FRET 现象。因此，共组装系统对于探索体外光合作用过程具有重要意义，因为它旨在模仿天然叶绿体。