Effect of Electrostatic Fields on Self-Assembly at Surfaces

CBET-0827822 Melosh界面处的自组装涉及电荷、结合强度、传输和可逆性之间的微妙平衡。外部场或不均匀的电荷分布可以通过加速、抑制或改变组装过程以令人惊讶的方式改变组装行为。特别地，许多分子和生物物种本身是高电荷系统，其在反应/组装期间也可以经历显著的构象和静电重构。这种在外场中自组装和组装过程中电荷重新分配的一般问题很少受到关注，但对于自上而下/自下而上图案化或更传统的应用（如DNA微阵列和生物传感器）的目标至关重要。本项目将系统地测量电场如何调节界面处的自组装，并开发一个经过充分验证的理论模型。一种新的光学技术将被应用于监测组装物种的空间和时间积累以及单纳米精度的离子双层，提供新的，定量信息的高电荷物种的动态。在这些实验中，DNA作为一个理想的模型系统，因为初步的研究表明，离子强度和电场对组装有一定的影响，但尚未建立一个完整的理论模型。DNA运输到界面，杂交和熔化动力学将作为长度，势场，错配位置和电荷密度的函数进行研究。这个项目的智力价值是阐明电场和离子分布如何影响自组装机制。从根本上说，这项工作将填补我们对高电荷物种如何在外部偏压下在表面相互作用和反应的理解中的空白。虽然小离子和胶体在外场中的行为是公认的领域，但电场下的自组装，组装过程中单体重构的趋势以及场梯度内力分布对DNA的影响尚未被探索。将开发平均场和布朗动力学理论模型，这些模型可以复制这些实验的结果，从而更深入地了解它们的机制。该项目更广泛的影响包括开发模型来预测表面上DNA的杂交和熔化动力学，为纳米材料组装提供直接的纠错方法，教育研究生和本科生，并传播这些发现。开发控制界面活性的新方法对于分离、生物污染、DNA阵列技术和涂层具有重要意义。装配和字段之间的相互作用的充分理解将允许脉冲算法和条件的设计，通过它大大加速DNA杂交，同时减少错配和交叉污染，常用的DNA微阵列的一个关键问题，并可以在许多应用中实现。这些结果将与其他研究人员广泛分享，首先是通过开发一个网站，让公众免费访问所使用的代码和协议。除了科学和技术影响外，这项建议还包括教育外联部分。本科研究，课程开发，科学专业发展和辅导小学生是研究计划的一个组成部分。

CBET-0827822MeloshSelf-assembly at interfaces involves a delicate balance between charge, bonding strength, transport, and reversibility. External fields or non-uniform charge distributions can alter assembly behavior in surprising ways by accelerating, inhibiting or changing the assembly process. In particular, many molecular and biological species are themselves highly-charged systems which may also undergo significant conformational and electrostatic reconfiguration during reaction/assembly. This general problem of self-assembly in external fields and charge-redistribution during the assembly process has received little attention, yet is vital for the goals of top-down/bottom-up patterning or more traditional applications such as DNA microarrays and biosensors. This project will systematically measure how electric fields modulate self-assembly at interfaces, and develop a fully-vetted theoretical model. A new optical technique will be applied to monitor the spatial and temporal build-up of assembling species as well as the ionic double layer with single nanometer accuracy, providing new, quantitative information on the dynamics of highly charged species. In these experiments DNA serves as an ideal model system, as preliminary studies have shown that ionic strength and electric fields have some effect on assembly, but a complete theoretical model has not been established. DNA transport to the interface, hybridization, and melting kinetics will be studied as a function of length, potential field, mismatch locations, and charge density. The intellectual merit of this project is to elucidate how electric fields and ion distributions affect self-assembly mechanisms. Fundamentally, this work will fill a void in our understanding of how highly-charged species interact and react at surfaces under an external bias. While small ion and colloidal behavior in external fields are well-established areas, self-assembly under electric fields, the tendency of monomer reconfiguration during assembly, and the effect of force distribution on DNA within field gradients have not been explored. Mean-field and Brownian dynamics theoretical models will be developed that can replicate the results of these experiments, providing deeper insight into their mechanism. The broader impacts of this project include developing models to predict the hybridization and melting dynamics of DNA on surfaces, providing straight-forward error correction methods for nanomaterials assembly, educate graduate and undergraduate students, and to disseminate these findings. Development of new methods to control interfacial activity is important for separations, bio-fouling, DNA-array technology and coatings. A full understanding of the interplay between assembly and fields will allow design of pulse algorithms and conditions through which to greatly accelerate DNA hybridization while reducing mis-matches and cross-contamination, a critical problem for commonly used DNA microarrays, and can be implemented in a number of applications. These results will be widely shared with other researchers, foremost through development of a website with free public access to the codes and protocols used. In addition to scientific and technological impact, this proposal incorporates an educational outreach component as well. Undergraduate research, curriculum development, scientific professional development, and tutoring elementary school students are an integral part of the research program.