Circular Dichroism of Chiral Molecules in DNA-Assembled Plasmonic Hotspots
Circular Dichroism of Chiral Molecules in DNA-Assembled Plasmonic Hotspots
复制标题
DOI：
10.1021/acsnano.8b03146
复制
发表时间：
2018-09-01
期刊：
影响因子：
17.1
通讯作者：
Liedl, Tim
中科院分区：
文献类型：
--
作者：
Kneer, Luisa M.;Roller, Eva-Maria;Liedl, Tim
分子的手性状态在分子识别和生化反应中起着至关重要的作用。正因为如此，由于大多数现代药物都是手性的，因此对分子手性的灵敏可靠的检测对药物开发具有重要意义。大多数自然产生的生物分子在紫外区表现出圆二色(CD)。理论研究和多个实验表明，当金属表面和手性生物分子接近时，这种UV-CD可以转移到等离子体频域。在这里，我们证明了通过在等离子体热点中放置手性分子，这里是双链DNA，可以显著地增强CD转移效应。通过使用不同的颗粒类型(金、银、球和棒)并利用DNA折纸的多功能性，我们能够系统地研究不同颗粒距离对CD转移效率的影响，并演示整个光谱到近红外的Cd转移。为此，纳米棒也被垂直放置在DNA折纸上，形成坚固的光学天线。理论模型证明了分子手性和非手性电场之间的复杂关系，支持了我们的实验发现。从实验测量和理论考虑，我们得出结论，对于具有强等离子体热点的体系，转移的CD最密集，因为我们发现它们位于球形纳米颗粒之间的相对较小的间隙(5-12 nm)，并且最好是在纳米棒的尖端之间。
The chiral state of a molecule plays a crucial role in molecular recognition and biochemical reactions. Because of this and owing to the fact that most modern drugs are chiral, the sensitive and reliable detection of the chirality of molecules is of great interest to drug development. The majority of naturally occurring biomolecules exhibit circular dichroism (CD) in the UV range. Theoretical studies and several experiments have demonstrated that this UV-CD can be transferred into the plasmonic frequency domain when metal surfaces and chiral biomolecules are in close proximity. Here, we demonstrate that the CD transfer effect can be drastically enhanced by placing chiral molecules, here double-stranded DNA, inside a plasmonic hotspot. By using different particle types (gold, silver, spheres, and rods) and by exploiting the versatility of DNA origami, we were able to systematically study the impact of varying particle distances on the CD transfer efficiency and to demonstrate CD transfer over the whole optical spectrum down to the near-infrared. For this purpose, nanorods were also placed upright on DNA origami sheets, forming strong optical antennas. Theoretical models, demonstrating the intricate relationships between molecular chirality and achiral electric fields, support our experimental findings. From both experimental measurements and theoretical considerations, we conclude that the transferred CD is most intensive for systems with strong plasmonic hotspots, as we find them in relatively small gaps (5-12 nm) between spherical nanoparticles and preferably between the tips of nanorods.