磁镊子是一种单分子力和扭矩光谱技术,能够在体外对生物分子进行机械询问,如核酸和蛋白质。它们使用源自永磁体或电磁体的磁场来吸引磁性颗粒,从而拉伸束缚的生物分子。它们可以很好地补充其他力谱技术,例如光镊子和原子力显微镜(AFM),因为它们可以作为非常稳定的力钳工作,能够在10fN到1nN的非常广泛的力范围内进行长时间的实验,具有1-10毫秒的时间和亚纳米的空间分辨率。他们的简单,鲁棒性,和多功能性使磁性镊子成为单分子生物物理学领域的关键技术,广泛应用于研究的力学性能,例如,核酸,基因组处理分子马达,蛋白质折叠,和核蛋白丝。此外,通过实时和高时空分辨率同时跟踪数百个生物分子,磁镊子允许高通量的单分子测量。磁镊子自然与基于表面的荧光光谱技术相结合,例如全内反射荧光显微镜,在生物分子上实现相关的荧光和力/扭矩光谱。本章介绍了磁镊子,包括硬件的描述,力校准背后的理论,它的时空分辨率,将它与其他技术相结合,和(非详尽的)生物应用概述。
Magnetic tweezers are a single-molecule force and torque spectroscopy technique that enable the mechanical interrogation in vitro of biomolecules, such as nucleic acids and proteins. They use a magnetic field originating from either permanent magnets or electromagnets to attract a magnetic particle, thus stretching the tethering biomolecule. They nicely complement other force spectroscopy techniques such as optical tweezers and atomic force microscopy (AFM) as they operate as a very stable force clamp, enabling long-duration experiments over a very broad range of forces spanning from 10 fN to 1 nN, with 1-10 milliseconds time and sub-nanometer spatial resolution. Their simplicity, robustness, and versatility have made magnetic tweezers a key technique within the field of single-molecule biophysics, being broadly applied to study the mechanical properties of, e.g., nucleic acids, genome processing molecular motors, protein folding, and nucleoprotein filaments. Furthermore, magnetic tweezers allow for high-throughput single-molecule measurements by tracking hundreds of biomolecules simultaneously both in real-time and at high spatiotemporal resolution. Magnetic tweezers naturally combine with surface-based fluorescence spectroscopy techniques, such as total internal reflection fluorescence microscopy, enabling correlative fluorescence and force/torque spectroscopy on biomolecules. This chapter presents an introduction to magnetic tweezers including a description of the hardware, the theory behind force calibration, its spatiotemporal resolution, combining it with other techniques, and a (non-exhaustive) overview of biological applications.