Quadruplex-Forming Primers for Isothermal DNA Amplification
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Solution Overview
Problem
Current PCR and RT-PCR methods face limitations due to competition between primer binding and self-annealing of target DNA, requiring expensive thermocycling equipment and being prone to product mis-priming, and existing probes are costly, complex, and inefficient for accurate quantification.
Innovation Solution
The use of quadruplex-forming primers that dissociate from DNA duplexes without heating, allowing isothermal amplification and incorporating 2-aminopurine (2Ap) for enhanced fluorescence detection, which eliminates self-annealing and simplifies quantification by using intrinsic primer fluorescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PCR primers are used, then amplification can proceed, but self-annealing of target DNA competes with primer binding reducing efficiency
Solution Approach 1:
The patent inverts the conventional primer design by making the primer complementary to itself rather than to the target sequence. This self-complementary design causes the primer to form a stable hairpin structure that prevents self-annealing of the target DNA, thereby improving both amplification efficiency and primer binding specificity.
Solution Approach 2:
The patent introduces a blocking sequence as an intermediary element within the primer structure. This blocking sequence prevents the primer from binding to non-complementary sites and reduces self-annealing of the target DNA, acting as a mediator that enhances the reliability of primer-target binding while maintaining productivity.
2Productivity
If thermocycling is used for DNA denaturation, then amplification can proceed, but expensive equipment is required
Solution Approach 1:
The patent employs a blocking sequence within the primer that automatically denatures the DNA template without requiring external heating. The blocking sequence undergoes a conformational change or chemical reaction that spontaneously separates the DNA strands, enabling amplification to proceed without expensive thermocycling equipment while maintaining productivity.
3Measurement precision
If conventional probes are used for quantification, then detection can be performed, but probes are costly and complex
Solution Approach 1:
The patent merges the primer and probe functions into a single molecular entity. The quantification probe is integrated directly into the primer structure, eliminating the need for separate probe molecules. This reduces complexity and cost while maintaining measurement precision through the primer's inherent binding specificity.
Solution Approach 2:
The patent creates a universal primer-probe construct that can be used for both amplification and quantification in a single reaction. This multi-functional design eliminates the need for separate probes and simplifies the overall assay while maintaining accurate quantification capabilities across different target sequences.
4Productivity
If standard primers are used, then amplification proceeds, but product mis-priming occurs reducing specificity
Solution Approach 1:
The patent inverts the primer design to be self-complementary rather than target-complementary. This creates a stable hairpin structure that prevents mis-priming by ensuring the primer can only bind to its intended target sequence, thereby improving product specificity without sacrificing amplification rate.
Solution Approach 2:
The blocking sequence acts as an intermediary that prevents mis-priming by sterically blocking non-specific binding sites. This maintains high product specificity while allowing efficient amplification to proceed through the blocked primer structure.
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
This approach extends the exponential amplification phase, reduces the need for thermocycling, and provides a cost-effective, efficient method for DNA amplification and quantification under isothermal conditions with high specificity and sensitivity.
Implementation Method 1
The use of quadruplex-forming primers that dissociate from DNA duplexes without heating
Implementation Method 2
primers that dissociate from DNA duplexes without heating
Implementation Method 3
incorporating 2-aminopurine (2Ap) for enhanced fluorescence detection, which eliminates self-annealing and simplifies quantification by using intrinsic primer fluorescence
Data Source
AI summary
A primer and method for amplification of a target nucleic acid, the primer adapted to conform into a conformation that dissociates from a complementary strand of DNA duplex. The conformation may have a free energy with more favorable thermodynamics than a corresponding DNA duplex, such as a B-DNA duplex. The dissociation may occur during an extension step of an amplification method, such as polymerase chain reaction. The method can proceed isothermally, and the primers may include intrinsic fluorescence.