Modified Oligonucleotides for Specific PCR Amplification
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Solution Overview
Problem
Current PCR assays face challenges with non-specific amplification, primer dimers, and contamination, which reduce efficiency and increase costs due to the need for hot-start DNA polymerases and additional reagents like dUTP and UNG enzyme.
Innovation Solution
Employing thermostable RNase H enzymes and modified oligonucleotides with cleavage domains that inhibit primer extension until hybridization and are activated at elevated temperatures, eliminating the need for reversibly inactivated DNA polymerases and reducing non-specific amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If primers are added to the reaction mixture at room temperature, then the reaction setup is simple and fast, but non-specific amplification and primer dimers form reducing assay efficiency
Solution Approach 1:
The primer is pre-modified with a blocking group at the 3'-end before the reaction begins. This preliminary modification prevents non-specific amplification and primer dimer formation during reaction setup, while still allowing the primer to hybridize to the target sequence. The blocking group is then removed in-situ during the amplification process, enabling productive extension only after proper hybridization has occurred.
2Reliability
If hot-start DNA polymerase is used to prevent non-specific amplification, then amplification specificity improves, but the cost and complexity of the assay increase
Solution Approach 1:
The blocking group is chemically extracted or removed from the primer's 3'-end during the amplification process. This removal occurs only after the primer has successfully hybridized to the target sequence, ensuring that non-specific binding does not lead to amplification. The extracted blocking group can be released as a separate molecule, allowing the primer to then serve as an effective template for DNA polymerase extension.
3Object-affected harmful factors
If additional reagents like dUTP and UNG enzyme are added to prevent contamination, then carry-over contamination is reduced, but the cost and number of reagents increase
Solution Approach 1:
The assay system performs its own contamination prevention function through the blocking group mechanism. By preventing non-specific amplification at the source through the modified primer, the system eliminates the need for additional anti-contamination reagents like dUTP and UNG enzyme. The blocking group effectively serves as a built-in safeguard that reduces carry-over contamination without requiring external chemical agents.
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 enhances the specificity of PCR assays by minimizing non-specific amplification and primer dimers, reducing costs, and allowing for more efficient and accurate nucleic acid amplification and detection.
Implementation Method 1
RNase H enzymes and modified oligonucleotides with cleavage domains that inhibit primer extension until hybridization and are activated at elevated temperatures
Data Source
AI summary
The present invention provides methods of cleaving a nucleic acid strand to initiate, assist, monitor or perform biological assays.