Plasmonic hotspots for single-molecule biophysics

在DFG的支持下，Acuna和Tinnefeld实验室开发并表征了来自光学天线的单分子荧光。这些光学天线由两个具有限定间隙的贵金属纳米颗粒组成，所述纳米颗粒使用DNA折纸纳米结构作为支架自组装。除了纳米颗粒的结构组织之外，DNA折纸还能够将特定的分子部分放置在天线的热点中。在澄清了放置在光学天线中的荧光染料的许多光谱特性（包括高达5000倍的荧光增强和生物相容性的第一个证据）之后，Tinnefeld实验室现在的目标是探索DNA折纸纳米天线作为单分子生物物理学中的新型检测体积。更高的可实现的计数率和增加的染料分子在热点的光稳定性将被用来研究快速的生物分子过程与增加的时间分辨率。DNA折纸纳米天线将优化减少空间位阻和单分子FRET从红色光谱区域的近红外将建立适应纳米天线的光谱分布。感兴趣的生物分子系统将被放置在天线的热点和蛋白质的快速构象变化将被研究和结合诱导的蛋白质折叠以及核酸发夹的过渡路径时间将被揭示。在此之上，DNA链置换拔河将在单核苷酸分辨率下可视化，希望揭示微妙的序列依赖性动力学变化，例如发生在表观遗传核苷酸修饰中的那些。总之，我们的目标是建立DNA折纸天线作为单分子研究的新检测体积，为快速生物分子过程打开一个新的窗口。

Supported by the DFG, the Acuna and Tinnefeld labs developed and characterized single-molecule fluorescence from optical antennas. These optical antennas are comprised of two noble metal nanoparticles with a defined gap that are self-assembled using DNA origami nanostructures as scaffold. In addition to the structural organization of nanoparticles, the DNA origami enables placing specific molecular moieties in the antenna’s hotspot. After clarifying many spectroscopic characteristics of fluorescent dyes placed in the optical antennas including fluorescence enhancement up to 5000 fold and first proofs of biocompatibility, the Tinnefeld lab now aims at exploring DNA origami nanoantennas as novel detection volume in single-molecule biophysics. The higher achievable count rates and increased photostability of the dye molecules in the hotspot will be used to study fast biomolecular processes with increased time resolution. DNA origami nanoantennas will be optimized for reduced steric hindrance and single-molecule FRET from the red spectral region to the near infrared will be established adapted to the spectral profile of the nanoantennas. Biomolecular systems of interest will be placed in the antenna’s hotspot and fast conformational changes of proteins will be studied and transition path times of binding induced protein folding as well as of nucleic acid hairpins will be revealed. Above that, a DNA strand displacement tug-of-war will be visualized at single-nucleotide resolution hoping to reveal subtle sequence dependent kinetic variations such as those occurring in epigenetic nucleotide modifications. In summary, we aim at establishing DNA origami antennas as new detection volume of single-molecule research opening a novel window into fast biomolecular processes.