5′-Mismatch Primers Resolve Multiplex PAP Annealing Conflicts
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Solution Overview
Problem
In pyrophosphorolysis activated polymerization (PAP) for nucleic acid amplification, inhibitory interactions occur when multiple pairs of primers are used to amplify almost-sequence-identical templates at a single locus, leading to reduced amplification efficiencies due to competitive annealing.
Innovation Solution
The use of 5′-artificial-mismatch primers with artificial mutations in the 5′ regions, which reduce thermal stabilities and disrupt DNA duplex structures, allowing for the amplification of multiple almost-sequence-identical templates at one locus without inhibitory interactions by introducing mismatches that favor specific primer-template interactions over competing primer interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple pairs of primers are used to amplify multiple templates at one locus, then the versatility and information content increase, but inhibitory interactions occur due to competitive annealing, reducing amplification efficiency
Solution Approach 1:
The patent applies local quality by introducing artificial mutations only in the 5′ regions of primers, while keeping the 3′ regions (which bind to templates) unchanged. This localized modification creates differential binding affinities: primers with mismatches in their 5′ regions have reduced stability when binding to non-target templates, minimizing cross-reactivity and inhibitory interactions, while maintaining full binding capability to their intended targets.
Solution Approach 2:
The patent changes the thermal stability parameter of primer-template duplexes by introducing artificial mutations. These mutations reduce the melting temperature (Tm) of mismatched duplexes more than matched duplexes, creating a thermal stability differential that allows specific primers to outcompete non-specific primers during annealing, thereby resolving the inhibitory interactions in multiplex amplification.
2Productivity
If artificial mutations are introduced into the 5′ regions of primers, then thermal stability of mismatched duplexes decreases, reducing inhibitory interactions, but primer design complexity increases
Solution Approach 1:
The patent segments the primer into two functional regions: a 3′ region that maintains perfect complementarity with the template for specific binding, and a 5′ region that contains artificial mutations to modulate thermal stability. This segmentation allows independent optimization of binding specificity and thermal properties, simplifying the overall design process despite the introduction of mutations.
Solution Approach 2:
Instead of trying to increase the stability of matched duplexes, the patent inverts the approach by decreasing the stability of mismatched duplexes through artificial mutations. This inversion strategy is simpler because it only requires introducing a few strategic mismatches rather than optimizing entire primer sequences, thereby reducing design complexity while achieving the desired effect.
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 increases amplification efficiencies by minimizing inhibitory interactions, ensuring high specificity and selectivity in amplifying multiple templates at a single locus, as demonstrated by the comparison of Singleplex-PAP and One-Locus-Duplex-PAP efficiencies.
Implementation Method 1
When the 3′ blocked primer anneals to its complementary DNA template, DNA polymerase can remove the 3′ blocker from the 3′ blocked primer in the presence of pyrophosphate or its analog, which reaction is called pyrophosphorolysis.
Implementation Method 2
The DNA polymerase can then extend the 3′ unblocked primer on the DNA template.
Implementation Method 3
The use of 5′-artificial-mismatch primers with artificial mutations in the 5′ regions, which reduce thermal stabilities and disrupt DNA duplex structures, allowing for the amplification of multiple almost-sequence-identical templates at one locus without inhibitory interactions
Data Source
AI summary
Multiplex pyrophosphorolysis activated polymerization uses multiple pairs of blocked primers to amplify multiple potential templates in a single reaction, including those almost-sequence-identical templates located in one locus. To identify and differentiate the multiple amplified products, individual molecules are sequenced in parallel. Thus multiplex PAP amplification is combined with parallel sequencing for ultrahigh-sensitive, ultrahigh-selective and ultrahigh-throughput detection of early cancer.