Circular DNA Purification Without Breakage Using Chaotropic Salts
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Solution Overview
Problem
Purification of large circular DNAs is technically challenging due to high probability of DNA breakage and degradation, hindering research and diagnostics applications.
Innovation Solution
A method involving chaotropic dense salt solutions and ultracentrifugation to stratify different DNA topologies, followed by dialysis to isolate circular DNA, without intercalating dyes or proteolytic enzymes, ensuring purity greater than 90-98%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional purification methods are used, then DNA can be isolated, but circular DNA undergoes breakage and degradation
Solution Approach 1:
The patent changes the physical-chemical parameters of the purification system by using chaotropic salts to create a dense solution that forms a gradient during ultracentrifugation. This gradient separates DNA topological forms based on their buoyant density, allowing circular DNA to be isolated in a native state without mechanical shearing forces that cause breakage in conventional methods.
Solution Approach 2:
The patent replaces mechanical purification methods (such as column-based or bead-based approaches that subject DNA to physical stress) with a density-gradient ultracentrifugation system. This substitution uses centrifugal force to stratify DNA topologies based on density differences, eliminating the mechanical shearing that leads to circular DNA degradation.
2Measurement precision
If intercalating dyes or proteolytic enzymes are used, then DNA separation may be enhanced, but DNA purity and integrity are compromised
Solution Approach 1:
The patent extracts and eliminates harmful substances from the purification protocol by omitting intercalating dyes and proteolytic enzymes entirely. The method achieves DNA topology separation using only chaotropic salt density gradients, thereby obtaining high-purity circular DNA without contamination from these reagents that can interfere with downstream applications.
Solution Approach 2:
The patent uses chaotropic salts as an intermediary substance that enables DNA topology separation without the need for intercalating dyes or enzymes. The chaotropic salt creates a density gradient that naturally stratifies different DNA forms based on their topological structure, providing a clean separation mechanism that preserves DNA integrity and purity.
3Quantity of substance
If circular DNA is present in small fraction of total DNA, then detection is difficult, but isolation is still achieved with high purity
Solution Approach 1:
The patent segments the total DNA population into distinct topological forms based on their buoyant density in the chaotropic salt gradient. Even when circular DNA constitutes a small fraction of total DNA, the density gradient resolves different topological forms (supercoiled, relaxed, linear) into separate zones, allowing selective isolation of circular DNA with high purity regardless of its abundance in the starting material.
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
Efficient isolation of circular DNA with high purity, enabling advanced research and diagnostics by maintaining the integrity of circular DNA structures.
Implementation Method 1
A sample comprising DNA species is combined with a chaotropic dense salt solution, and ultracentrifuged to generate a gradient in which different DNA topologies are stratified
Implementation Method 2
A sample comprising DNA species is combined with a chaotropic dense salt solution, and ultracentrifuged to generate a gradient in which different DNA topologies are stratified
Implementation Method 3
The matrix is dissolved by the chaotropic salt at ambient temperature, e.g. from about 10° C. to about 40° C.
Data Source
AI summary
Methods are provided for the isolation and analysis of circular DNA from complex samples, based on the topology of the DNA molecule. A sample comprising DNA species is combined with a chaotropic dense salt solution. A fraction containing the circular DNA of interest is isolated and dialyzed to remove excess salt. In some embodiments salt gradients are generated by ultracentrifugation in the absence of intercalating dyes, e.g. ethidium bromide; and in the absence of protease digestion. The circular DNA thus isolated is substantially pure, e.g. greater than about 75%, greater than about 80%, greater than about 90%, greater than about 95% of DNA in the isolated fraction is comprised of circular DNA.