Quantitative Modeling and Optimization of Magnetic Tweezers
Quantitative Modeling and Optimization of Magnetic Tweezers
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DOI：
10.1016/j.bpj.2009.03.055
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发表时间：
2009-06-17
影响因子：
3.4
通讯作者：
Dekker, Nynke H.
中科院分区：
文献类型：
--
作者：
Lipfert, Jan;Hao, Xiaomin;Dekker, Nynke H.
磁性镊子是一种强大的工具，可以操作单个DNA或RNA分子，并实时研究核酸-蛋白质相互作用。在这里，我们对磁钳中永磁体的磁场进行了建模，并从第一性原理计算了超顺磁珠所受的力。对于简单的对称几何结构，磁场可以用毕奥-萨伐尔定律进行半解析计算。对于复杂的几何形状，在铁轭存在的情况下，我们使用有限元三维偏微分方程组来数值求解静磁问题。理论预测与磁场的直接霍尔探头测量和施加在DNA拴系珠上的力的测量是定量一致的。利用这些预测理论，我们系统地探索了磁铁排列、磁铁间距、磁铁大小以及在磁铁中添加铁轭对可施加在系留粒子上的力的影响。我们发现，最大拉伸力的最佳构型是一对垂直排列的磁体，磁体之间的间隙最小，流胞厚度最小。遵循这些原则，我们提出了一种配置，允许人们在大约1微米的系绳珠子上施加>；=40pN拉伸力。
Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply >= 40 pN stretching forces on approximate to 1-mu m tethered beads.