Hydrodynamic effects on electrophoresis of biopolymers

奖项1067072 PI：巴特勒一个创新的研究计划相结合的理论，模拟和实验是追求调查的作用，流体动力学相互作用的聚电解质，如DNA的电泳。 在DNA的毛细管电泳中，分子平均是球形的，并且DNA的各个片段之间的流体动力学相互作用是指数屏蔽的-由骨架电荷和周围的抗衡离子产生的流场抵消。然而，如果DNA被拉伸，例如通过与电场结合施加的压力驱动流，则在实验上观察到横向于流动和场线的迁移。实际上存在由电场对电荷密度的极化产生的偶极流。虽然这种流动是弱的电泳速度相比，其取向的依赖性提供了一种手段，延长聚电解质迁移垂直于流动和场线。我们的研究是由这样的假设驱动的，即这种极化流是负责几种现象，如果没有远距离的，流体介导的相互作用之间的远距离的段的神经元，就无法解释。这些现象中的一些尚未被实验观察到，如一个长度依赖的电泳迁移率的伸长的纳米粒子，但他们预测的模拟。通过在实验室实验中确认这些效应的存在来测试基本假设是该项目的主要目标。智力优点：极化流的最简单模型预测了电场中带电聚合物的远段之间的偶极流体动力学相互作用。最近基于该模型的数值模拟表明，人们可以半定量地解释在有限的盐浓度，电场和流速范围内从DNA实验中收集的数据。 在这项工作的过程中，发现了一些实验上没有观察到的新现象。 正在进行的研究探讨的基础模型的有效性，并探讨了这种机制的潜在操纵的聚电解质在microchannels.Broader的影响：研究：这项工作是提高我们的理论认识的聚电解质和改变流行的观点，关于流体动力学筛选在微通道动力学。 这项研究还影响了广泛的技术，需要控制和定位带电的生物聚合物微通道内的能力，创造额外的可能性，操纵聚电解质，可能有利于应用，如增强吸附？DNA生物芯片？ 另一个潜在的应用是利用迁移速度随链长的变化，作为按长度分离DNA链的手段。教育：研究计划与我们的教育活动相结合，重点是培养学生在一个越来越依赖国际合作的世界中工作，以有效地推进科学和开发新技术。活动包括增加学生参与国际合作和会议。鼓励各级学生参与我们实验室内的高级研究;我们已经并将继续与大学现有的高中生计划合作。 在所有这些活动中，我们强调代表性不足的群体的参与，积极寻求他们的参与。

Award 1067072PIs: ButlerAn innovative research program combining theory, simulations, and experiments is pursued to investigate the role of hydrodynamic interactions in the electrophoresis of polyelectrolytes such as DNA. In capillaryelectrophoresis of DNA, the molecules are spherical on average and the hydrodynamic interactions among various segments of DNA are exponentially screened - the flow fields generated by the backbone charges and surrounding counterions cancel. However if the DNA is stretched, for example by a pressure driven flow applied in conjunction with the electric field, then a migration transverse to the flow and field lines is observed experimentally.The commonly held assumption that electric fields do not generate any long-range flow in the fluid surrounding a charged molecule is contradicted by theoretical work dating back to Debye; there is infact a dipolar flow generated by the polarization of the charge density by the electric field. Although this flow is weak in comparison to the electrophoretic velocity, its orientational dependence provides a means for elongated polyelectrolytes to migrate perpendicular to the flow and field lines. Our research is driven by the hypothesis that this polarization flow is responsible for several phenomena that cannot be explained without a long-range, fluid-mediated interaction between distant segments of the polyelectrolyte. Some of these phenomena have not yet been observed experimentally, such as a length-dependent electrophoretic mobility of an elongated polyelectrolyte, but they are predicted by simulations. Testing the underlying hypothesis by confirming the existence of these effects in laboratory experiments is a primary goal of the project.Intellectual Merit: The simplest model of the polarization flow predicts a dipolar hydrodynamic interaction between distant segments of a charged polymer in an electric field. Recent numerical simulations based on this model showed that one can semi-quantitatively account for data collected from DNA experiments over a limited range of salt concentration, electric field, and flow rate. In the course of this work several new phenomena were discovered that have not been observed experimentally. The ongoing research examines the validity of the underlying model and explores the potential of this mechanism for manipulating the distribution of polyelectrolytes in microchannels.Broader Impacts:Research: This work is enhancing our theoretical understanding of polyelectrolytes and altering prevailing views regarding hydrodynamic screening in polyelectrolyte dynamics. The research also impacts a wide range of technologies that require the ability to control and position charged biopolymers within microchannels by creating additional possibilities for manipulation of polyelectrolytes that may be advantageous for applications such as enhancing adsorption in ?DNA biochips?. Another potential application uses the variation in migration velocity with chain length as a means for separating DNA strands by length.Education: The program of research is integrated with our educational activities, which focus on preparing students to work in a world that increasingly depends upon international collaborations to efficiently advance science and develop new technologies. Activities include increasing the participation of students in international collaborations and meetings. Students of all levels are encouraged to become involved in advanced research within our laboratories; we have been, and continue, to work with an existing program for high school students at the University. In all of these activities, we emphasize the participation of underrepresented groups by actively seeking their involvement.