Optical Trap DNA Supercoiling via Bead Separation
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Solution Overview
Problem
Existing methods for supercoiling DNA, such as those using magnetic tweezers, are time-consuming and limit control over DNA orientation and position, making it difficult to achieve high degrees of supercoiling and combine with techniques like fluorescence microscopy.
Innovation Solution
A method involving torsionally constrained DNA molecules connected to optically trapped beads, where increasing the distance between the beads induces torque and destabilizes bonds, allowing for rapid supercoiling and easy orientation, enabling the DNA to remain supercoiled at low tensions without active rotation of the beads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic tweezers are used to supercoil DNA by rotating magnetic beads, then supercoiling can be achieved, but the process becomes time-consuming requiring numerous rotations
Solution Approach 1:
The patent replaces the mechanical rotation of magnetic beads with an optical field-based approach. Optical traps (laser beams) are used to hold and manipulate the beads, allowing torque to be applied through optical forces rather than mechanical rotation. This substitution enables faster supercoiling by eliminating the need for numerous manual or automated rotation cycles.
Solution Approach 2:
The patent changes the control parameter from rotational position to optical trap position. By moving the optical traps relative to each other, torque is applied to the DNA molecule without requiring rotation of the beads themselves. This parameter change from angular to linear control enables more rapid application of torsional stress.
2Ease of operation
If DNA is tethered to a fixed surface using magnetic tweezers, then supercoiling can be maintained, but control over DNA orientation and position is limited
Solution Approach 1:
The patent transitions from a static tethering system to a dynamic optical trapping system. Both ends of the DNA molecule are held by optical traps that can be independently positioned and moved in three-dimensional space. This dynamic control allows the DNA to be oriented in any desired direction and position, including horizontal orientation perpendicular to the optical axis, while maintaining supercoiling through controlled relative trap movement.
Solution Approach 2:
The optical trap system serves multiple functions: it holds the beads in position, applies torque through differential positioning, enables rapid reorientation of the DNA molecule, and allows easy exchange of solution conditions. This multi-functional approach replaces the specialized fixed-surface tethering system, providing both ease of operation and experimental flexibility.
3Manufacturing precision
If magnetic beads are rotated numerous times to achieve high supercoiling, then the desired supercoiled state can be reached, but the process requires significant time for long DNA molecules
Solution Approach 1:
The patent replaces incremental mechanical rotation with direct optical torque application. By positioning optical traps at different locations, a torque is applied that directly induces supercoiling without requiring multiple small rotational steps. This allows long DNA molecules to reach high supercoiling degrees (σ ∼ -0.7) much faster than traditional magnetic rotation methods.
Solution Approach 2:
The patent applies torque in a preliminary and continuous manner through the optical trap positioning, rather than through discrete rotational steps. The optical traps are positioned to create the desired torsional stress from the beginning, allowing the DNA to supercoil continuously and rapidly to the target state without the time-consuming incremental approach of traditional methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid and controlled supercoiling of DNA, allowing for stable supercoiled states at low tensions, facilitating combination with fluorescence microscopy and other biophysical studies.
Implementation Method 1
A method involving torsionally constrained DNA molecules connected to optically trapped beads
Implementation Method 2
increasing the distance between the beads induces torque and destabilizes bonds, allowing for rapid supercoiling
Data Source
Figure 1(A)~1(E)
Figure 2
Figure 3
AI summary
A method for supercoiling DNA, e.g. negatively supercoiling DNA, is disclosed. In an initial state, at least part of a DNA molecule is torsionally constrained and associated with a first linking number. The at least part of the DNA molecule has a first end connected to a first body and a second end connected to a second body. The method comprises increasing a distance between the first body and the second body for inducing a torque in the at least part of the DNA molecule and for bringing the at least part of the DNA molecule from the initial state into an intermediate state. In the intermediate state the at least part of the DNA molecule is temporarily torsionally unconstrained for at least partially releasing the induced torque for changing, e.g. decreasing, the first linking number. The method further comprises decreasing the distance between the first and second body for bringing the at least part of the DNA molecule from the intermediate state into a further state in which the at least part of the DNA molecule is torsionally constrained and associated with a second linking number different from the first linking number.