Delayed-PAP Primer Mutations for Minimal-Copy-Ratio Amplification
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Solution Overview
Problem
In pyrophosphorolysis activated polymerization (PAP) assays, large copy numbers of templates lead to inaccurate and inconsistent amplification due to early product accumulation, and minimal-copy-ratios in multiplex reactions result in inconsistent amplification of target templates due to substrate depletion by internal controls.
Innovation Solution
Introducing artificial mutations into the 3' region of 3' blocked primers to delay product accumulation, allowing for delayed-PAP, which separates the amplification timing of internal controls and targets, thereby maintaining substrate availability for target amplification in multiplex reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regular-PAP is used to amplify templates with large copy numbers, then amplification speed is fast, but product accumulation occurs too early causing inaccurate and inconsistent results
Solution Approach 1:
The patent applies preliminary action by introducing artificial mutations into primers before the amplification reaction begins. These mutated primers are designed to bind with lower affinity to the template, which delays the onset of product accumulation until later cycles when the template has been sufficiently diluted. This pre-designed delay mechanism ensures that amplification of high-copy templates occurs at an appropriate time, resolving the contradiction between fast amplification speed and accurate results.
2Productivity
If multiplex-PAP is used with internal controls having high copy numbers, then internal control amplification is efficient, but substrates are depleted causing inconsistent target amplification
Solution Approach 1:
The patent applies preliminary action by pre-designing mutated primers for internal control templates that will delay their product accumulation kinetics. These primers contain artificial mutations that reduce binding affinity, causing the internal control amplification to occur later in the cycling process. This timing adjustment prevents early substrate depletion that would otherwise interfere with target amplification, allowing both internal controls and targets to amplify consistently in multiplex reactions.
Solution Approach 2:
The patent applies dynamics by creating a system where different primer-template combinations have dynamically different binding affinities and amplification kinetics. The mutated primers for internal controls are designed to have lower affinity than wild-type primers, creating a temporal separation in amplification events. This dynamic kinetic separation allows the system to accommodate both high-copy internal controls and low-copy targets without substrate depletion issues, improving target amplification consistency.
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
Delayed-PAP effectively delays product accumulation by 10 cycles or more, ensuring accurate and consistent amplification of targets even in minimal-copy-ratio conditions by maintaining substrate availability, improving the reliability of PAP assays.
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, and this reaction is called pyrophosphorolysis.
Implementation Method 2
The DNA polymerase can then extend the unblocked primer on the DNA template.
Data Source
AI summary
A minimal-copy-ratio of templates is a problem in detecting early stage cancer where minimal copies of somatic cancer-specific mutations are targeted in the presence of large copies of wildtype genome DNA, commonly a 1/10,000 or even less minimal-copy-ratios between the mutant target and wildtype control templates. To overcome this problem, delayed pyrophosphorolysis activated polymerization (delayed-PAP) was developed which can delay product accumulation of the wildtype control to a much later time or cycle, such as by 15 cycles or by 30,000 folds. In the multiplex format, delayed-PAP is particularly useful to amplify not only the wildtype control but also mutant target templates accurately and consistently in the minimal-copy-ratio situation.