A Horizontal Magnetic Tweezers and Its Use for Studying Single DNA Molecules

Abstract

We report the development of a magnetic tweezers that can be used to micromanipulate single DNA molecules by applying picoNewton (pN)-scale forces in the horizontal plane. The resulting force–extension data from our experiments show high-resolution detection of changes in the DNA tether’s extension: ~0.5 pN in the force and <10 nm change in extension. We calibrate our instrument using multiple orthogonal techniques including the well-characterized DNA overstretching transition. We also quantify the repeatability of force and extension measurements, and present data on the behavior of the overstretching transition under varying salt conditions. The design and experimental protocols are described in detail, which should enable straightforward reproduction of the tweezers.

A Horizontal Magnetic Tweezers for Studying Single DNA Molecules and DNA-Binding Proteins

“…All micromanipulation experiments were performed using the horizontal magnetic tweezers described in Ref. [ 24 ]. Figure 7 shows the schematic diagram of the horizontal magnetic tweezers.…”

“…After incubation, 5 μL of the DNA-bead construct was introduced through the sample cell loaded with 1× Tris-EDTA (TE) and 150 mM NaCl buffer. Fifth, we integrated the DNA-loaded sample cell and surface-functionalized glass pipette as described in [ 24 ] into the horizontal magnetic tweezers. The horizontal magnetic tweezers were composed of an optical microscope and a motorized micromanipulator.…”

“…We used histones H2A, H2B, H3, and H4; H1 and H5 were not used in our studies. These arrays were mechanically micromanipulated using the horizontal magnetic tweezers apparatus described in [ 24 ]. Briefly, linear DNA was tethered to superparamagnetic beads on both ends with one of the beads also connected to a stiff biotinylated micropipette while the other bead was suspended in buffer.…”

Orthogonality Measurement of Three-Axis Motion Trajectories for Micromanipulation Robot Systems

“…Their sizes range from microns to submillimeter, and the positioning precision of the system can reach micron or even submicron or nanometer levels. This kind of system has been applied in microassembly [ 1 , 2 , 3 ], microinjection [ 4 , 5 ], bioengineering [ 6 , 7 , 8 , 9 , 10 , 11 ], minimally invasive surgery [ 12 , 13 , 14 , 15 ], and other microscopic fields. The motion control system with three translational degrees of freedom and driven by ball screw, guide rail, slider, and motor, is one of the various motion control systems.…”

Design, modeling, and control of a horizontal magnetic micromanipulator

“…The vertical magnetic micromanipulators require complex and sophisticated calibration techniques. To eliminate the calibration requirements, horizontal magnetic micromanipulators have been reported (Fabian et al, 2018; McAndrew et al, 2016; Schwarz et al, 2013; Yan et al, 2004). However, the reported designs are based on permanent-magnets and the motion of these magnets are manually controlled by electric motors.…”