Circular DNA Purification Through Topology-Based Separation
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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
Methods for isolating circular DNA based on its topology using chaotropic dense salt solutions and ultracentrifugation, without intercalating dyes or proteolytic enzymes, to generate a gradient for stratifying different DNA topologies, followed by dialysis to remove excess salt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional purification methods are used for circular DNA, then the purification process can be completed, but the DNA undergoes breakage and degradation due to high mechanical stress
Solution Approach 1:
The patent changes the physical-chemical parameters of the purification system by using a density gradient medium with specific density (1.7-2.0 g/cm³) and viscosity characteristics, along with controlled ultracentrifugation speeds, to separate circular DNA from linear DNA without subjecting the DNA to mechanical stress that causes breakage
Solution Approach 2:
The patent replaces mechanical shearing forces with density-based separation through ultracentrifugation in a density gradient medium, substituting the mechanical extraction method with a physical separation method based on topological differences in DNA density
2Measurement precision
If ultracentrifugation in density gradient medium is used, then circular DNA can be separated by topology, but the process requires specialized equipment and complex procedure
Solution Approach 1:
The patent uses a density gradient medium that serves multiple functions: it provides the density gradient for separation, maintains DNA stability during the process, and enables visualization of separated fractions through optical density measurements, reducing the need for additional specialized reagents or equipment
3Productivity
If intercalating dyes or proteolytic enzymes are used for DNA separation, then separation can be enhanced, but DNA purity is reduced due to contamination from additives
Solution Approach 1:
The patent exploits the intrinsic topological differences between circular and linear DNA molecules themselves as the separation mechanism, without requiring external additives like intercalating dyes or enzymes. The DNA's own structural properties (topology and density) are used to achieve separation, eliminating contamination from separation reagents
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
Achieves high purity isolation of circular DNA, with purity greater than 90% in some embodiments, enabling effective analysis and sequencing of circular DNA forms.
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
The matrix is dissolved by the chaotropic salt at ambient temperature, e.g. from about 10° C. to about 40° C.
Implementation Method 3
The fraction containing the circular DNA of interest is then isolated and dialyzed to remove excess salt
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.