Single-Molecule Trapping and Nanoscale Dielectric Response

Katharine Hunt得到了理论和计算化学计划的资助，用于执行单分子陷阱和纳米级介电响应的理论研究。这项研究的目的是建立一个定量模型，用于标记插层染料的DNA片段的光学捕获和标记染料的聚苯乙烯球的捕获。在分析激光场与DNA等大分子之间的相互作用时，Hunt将考虑分子内激发极化的分布，而不是使用单一的全局极化率。纳米尺度的介电响应将通过从头计算和分析两个非局域介电函数来研究，一个介电函数表征分子内势屏蔽，另一个介电函数将介电位移与局域Maxwell场联系起来。这一结果将允许计算多体性质，包括溶液相介电函数。观察、捕获和操纵具有生物重要性的单个分子的能力为研究和分子水平的控制开辟了一系列新的可能性。一些可能性包括：超灵敏的DNA分析，染色体操作，直接观察生物分子在细胞内的运输，观察DNA的构象波动，研究超螺旋/解螺旋转变的动力学，以及快速DNA测序方案。亨特的研究将有助于在分子水平上对这一新发现的现象进行物理理解。

Katharine Hunt is supported by a grant from the Theoretical and Computational Chemistry Program to perform theoretical studies of single molecule trapping and nanoscale dielectric response. The goal of this research is to develop a quantitative model for optical trapping of DNA fragments labeled with intercalating dyes, and the trapping of dye-labeled polystyrene spheres. In analyzing the interaction between a laser field and a large molecule such as DNA, Hunt will consider the intramolecular distribution of induced polarization rather than using a single global polarizability. Nanoscale dielectric response will be investigated by ab initio calculation and analysis of two non-local dielectric functions, one that characterizes the intramolecular potential screening, and a second one that relates the dielectric displacement to the local Maxwell field. The result will permit the calculation of many-body properties, including solution-phase dielectric functions.The capability to observe, trap, and manipulate individual molecules of biological importance opens up a range of new possibilities for investigation, and for molecular-level control. Some possibilities include: ultrasensitive DNA analysis, chromosome manipulation, direct observation of intracellular transport of biomolecules, observation of conformational fluctuations in DNA, the study of the dynamics of supercoiling / uncoiling transitions, and schemes for rapid DNA sequencing. Hunt's research will contribute to a physical understanding of this newly discovered phenomenon at the molecular level.