Mosconi Francesco, Allemand Jean François, Croquette Vincent
LPS-ENS, UMR 8550 CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France.
Rev Sci Instrum. 2011 Mar;82(3):034302. doi: 10.1063/1.3531959.
We present here the principle of soft magnetic tweezers which improve the traditional magnetic tweezers allowing the simultaneous application and measurement of an arbitrary torque to a deoxyribonucleic acid (DNA) molecule. They take advantage of a nonlinear coupling regime that appears when a fast rotating magnetic field is applied to a superparamagnetic bead immersed in a viscous fluid. In this work, we present the development of the technique and we compare it with other techniques capable of measuring the torque applied to the DNA molecule. In this proof of principle, we use standard electromagnets to achieve our experiments. Despite technical difficulties related to the present implementation of these electromagnets, the agreement of measurements with previous experiments is remarkable. Finally, we propose a simple way to modify the experimental design of electromagnets that should bring the performances of the device to a competitive level.
我们在此介绍软磁镊子的原理，它改进了传统磁镊子，能够对脱氧核糖核酸（DNA）分子同时施加并测量任意扭矩。它们利用了一种非线性耦合机制，当向浸没在粘性流体中的超顺磁性珠子施加快速旋转磁场时会出现这种机制。在这项工作中，我们展示了该技术的发展，并将其与其他能够测量施加到DNA分子上扭矩的技术进行了比较。在这个原理验证中，我们使用标准电磁铁来进行实验。尽管这些电磁铁目前的实施存在技术难题，但测量结果与先前实验的一致性非常显著。最后，我们提出了一种简单的方法来修改电磁铁的实验设计，这应该会使该装置的性能达到有竞争力的水平。
