Template-Free Construction of Highly Ordered Monolayered Fluorescent Protein Nanosheets: A Bioinspired Artificial Light-Harvesting System.

Using biological materials for light-harvesting applications has attracted considerable attention in recent years. Such materials provide excellent environmental compatibility and often exhibit superior properties over synthetic materials. Herein, inspired by the outstanding energy transfer performance in coelenterates, we constructed a template-free, highly ordered two-dimensional light-harvesting system by covalent-induced coassembly of EBFP2 (donor) and EGFP (acceptor), in which the fluorescent chromophores were well distributed and adopted a fixed orientation. By introducing approximate square planar binding sites on the side surface of protein, assembly pattern was pin down and self-assembly extended in orthogonal directions to achieve monolayered and tessellated protein nanoarrays. The excellent antiself-quenching property of fluorescent proteins endowed the coassembled system with attractive light-harvesting capability. Even at high local concentrations, a low resonance energy transfer self-quenching was observed and, therefore, energy can be efficiently transferred. More importantly, the distance between adjacent chromophores is continuously adjustable. By making minor changes to the length of the inducing linker, we have achieved significant control over the size of the assembly. A micron-sized light-harvesting system with satisfactory energy transfer efficiency was finally obtained. This work developed a template-free light-harvesting system completely based on fluorescent proteins (FPs), which overcame the restriction of using templates. Not limited to this work, the special core-shell structure of FPs may be expected to direct the optimization of fluorescent dyes by cladding.