Modified Oligonucleotides with RNase H Cleavage for PCR Specificity
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Solution Overview
Problem
Current nucleic acid amplification techniques, such as PCR, face challenges with non-specific amplification and primer dimers due to primer hybridization at lower temperatures, leading to reduced efficiency and false positives, and existing hot-start methods are labor-intensive or costly.
Innovation Solution
Employing a thermostable RNase H or nicking enzyme that becomes active at elevated temperatures to cleave modified oligonucleotides, preventing non-specific primer extension and eliminating the need for reversibly inactivated DNA polymerases or ligases, using oligonucleotides with 2'-fluoro residues or other modifications to enhance specificity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If primers are hybridized at lower temperatures to assemble reaction mixtures, then ease of operation is improved, but non-specific amplification increases
Solution Approach 1:
The patent applies preliminary action by incorporating a blocking group into the primer structure before the amplification reaction begins. This blocking group prevents primer extension at lower temperatures during reaction mixture assembly, while allowing specific hybridization to occur. The block is subsequently removed under controlled conditions to enable specific amplification only of the intended target sequence.
Solution Approach 2:
The patent employs parameter changes by utilizing temperature-dependent chemistry to control primer activity. The blocking group is designed to be removable under specific conditions (such as heat-labile removal or specific chemical treatments), transitioning the primer from an inactive state during assembly to an active state during amplification, thereby resolving the contradiction between ease of assembly and amplification specificity.
2Reliability
If manual hot-start methods are used to reduce non-specific amplification, then amplification specificity is improved, but labor intensity increases
Solution Approach 1:
The patent applies self-service by incorporating a blocking group that automatically prevents primer extension during the assembly phase and early denaturation steps. The block is removed automatically under controlled conditions (such as heat or chemical treatment) without requiring manual intervention, allowing the reaction mixture to self-regulate primer activity throughout the amplification cycles.
3Reliability
If reversibly inactivated DNA polymerase is used to achieve hot-start, then amplification specificity is improved, but device complexity increases
Solution Approach 1:
The patent applies taking out by separating the primer extension function from the hybridization function. Instead of modifying the DNA polymerase to be reversibly inactivated, the invention extracts the blocking function from the polymerase and places it directly on the primer molecule itself. This simplifies the overall system by eliminating the need for complex polymerase modification while achieving the same hot-start effect.
4Ease of operation
If standard primers are used at lower temperatures, then ease of operation is improved, but primer dimer formation increases
Solution Approach 1:
The patent applies preliminary anti-action by incorporating a blocking group on the primer that proactively prevents primer dimer formation during the low-temperature assembly phase. The block is strategically positioned to interfere with primer-primer hybridization and extension, countering the harmful effect of primer dimer formation before it can occur, while still allowing specific target hybridization to proceed.
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 significantly reduces non-specific amplification, increases the specificity of primer-based reactions, and provides a cost-effective means for achieving highly specific amplification reactions, including PCR, oligonucleotide ligation assays, and sequencing, while minimizing primer dimer formation and false positives.
Implementation Method 1
Employing a thermostable RNase H or nicking enzyme that becomes active at elevated temperatures to cleave modified oligonucleotides
Implementation Method 2
using oligonucleotides with 2'-fluoro residues or other modifications to enhance specificity and stability
Data Source
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AI summary
The present invention pertains to novel oligonucleotide compounds for use in various biological assays, such as nucleic acid amplification, ligation and sequencing reactions. The novel oligonucleotides comprise a ribonucleic acid domain and a blocking group at or near the 3' end of the oligonucleotide. These compounds offer an added level of specificity previously unseen. Methods for performing nucleic acid amplification, ligation and sequencing are also provided. Additionally, kits containing the oligonucleotides are also disclosed herein.