Nicking Enzyme Substrate for False Negative Detection
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Solution Overview
Problem
Current methods for nucleic acid amplification reactions face challenges in accurately detecting target nucleic acids due to issues like false negatives, where specific amplification is inhibited, and there is a need for improved methods to differentiate between true and false negative results.
Innovation Solution
The development of a nucleic acid substrate molecule with a nicking enzyme recognition site and a quenched fluorophore that, when nicked and extended by polymerase, releases a detectable signal, allowing for the detection of nicking enzyme and polymerase activity, and subsequent amplification of target nucleic acid molecules under isothermal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nucleic acid amplification reactions are used, then amplification of target nucleic acid can be achieved, but false negative results occur due to inhibition of specific amplification
Solution Approach 1:
The patent introduces a substrate molecule as an intermediary control element that mediates between the amplification reaction and detection. This substrate contains a nicking enzyme recognition site and a fluorophore-quencher system that serves as a controlled intermediary to verify enzyme activity and reaction validity, allowing differentiation between true negatives and false negatives caused by inhibition.
Solution Approach 2:
The patent implements a feedback mechanism through the substrate molecule that provides real-time verification of nicking enzyme activity during the amplification reaction. The fluorogenic signal from the substrate acts as feedback to confirm that the nicking enzyme is active and functioning properly, enabling the system to distinguish between genuine absence of target (true negative) and inhibition of reaction (false negative).
2Reliability
If a substrate molecule with nicking enzyme recognition site and fluorophore is used, then enzyme activity can be detected and false negatives reduced, but reaction complexity increases
Solution Approach 1:
The patent merges multiple functions into a single substrate molecule: it combines the nicking enzyme recognition site, the fluorophore, and the quencher into one integrated oligonucleotide structure. This merging allows the substrate to simultaneously serve as an enzyme substrate, a signal generator, and a reaction control element, reducing the need for separate components while maintaining reliability.
Solution Approach 2:
The substrate molecule is designed with multi-functionality, serving as both the control element for verifying enzyme activity and as part of the amplification reaction system. The same substrate that controls the reaction also provides the fluorescent signal for detection, eliminating the need for separate control reactions and reducing overall system complexity despite the sophisticated molecular design.
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 accuracy of nucleic acid detection by providing a means to confirm enzyme activity and amplify target sequences efficiently, reducing the likelihood of false negatives and improving the interpretation of negative results in nucleic acid amplification reactions.
Implementation Method 1
a nicking enzyme recognition site, a nick site
Implementation Method 2
contacting the nicked duplex with a polymerase in the presence of dNTPs; extending the polymerase
Implementation Method 3
a fluorescent detectable label covalently linked at the 3' end; detecting a signal from the fluorescent detectable label that is separated from the quencher
Implementation Method 4
a second nucleic acid strand having a sequence capable of duplexing with the first strand
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 2A~2B
AI summary
The present invention provides compositions and methods for assaying the activity of nicking enzyme and polymerase in a reaction involving the use of a nucleic acid substrate molecule that detects nicking enzyme and polymerase extension activities by the release of a detectable reporter (e.g., a fluorophore).