RT-PCR Primer Specificity via Delayed Reverse Transcriptase Addition
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Solution Overview
Problem
Current RT-PCR methods face challenges with specificity and sensitivity due to non-specific binding of oligonucleotide primers at ambient temperatures, leading to misprimed RNA transcription, which decreases assay sensitivity and specificity.
Innovation Solution
A method involving a reaction mixture with a reverse transcriptase enzyme, DNA polymerase, dNTPs, primers, an aptamer oligonucleotide to inhibit the reverse transcriptase, and an inhibitor for the aptamer oligonucleotide, where the reaction is incubated at a lower temperature to inhibit RT activity and then at a higher temperature for reverse transcription and PCR amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If reaction mixture is assembled at ambient temperature, then ease of operation is improved, but non-specific binding of primers occurs decreasing specificity
Solution Approach 1:
The reaction mixture is pre-assembled at ambient temperature including all components except the reverse transcriptase enzyme. The primer and template RNA are allowed to anneal at this temperature, but the RT enzyme is added only after the mixture is transferred to the thermocycler and heated to the RT temperature (e.g., 50°C). This preliminary assembly at ambient temperature followed by delayed enzyme addition ensures that priming occurs only at the intended temperature, preventing non-specific binding while maintaining ease of operation.
Solution Approach 2:
The patent applies preliminary anti-action by preventing the reverse transcriptase enzyme from being active during the assembly phase. The RT enzyme is either omitted during assembly or kept inactive (e.g., stored on ice or added after heating), thereby preemptively preventing non-specific reverse transcription that would occur if the enzyme were active at ambient temperature. This counter-measure is applied in advance to eliminate the harmful effect of mispriming.
2Manufacturing precision
If reaction mixture is assembled on ice, then non-specific binding is reduced improving specificity, but productivity decreases due to immediate cycling requirement
Solution Approach 1:
The reaction mixture is pre-assembled at ambient temperature (not on ice) including all components except the reverse transcriptase enzyme. This preliminary assembly can be done without immediate cycling, allowing for higher throughput workflows where multiple plates can be prepared in advance. The RT enzyme is added only after the mixture is transferred to the thermocycler and heated to the RT temperature, ensuring specificity is maintained while enabling batch preparation and improved productivity.
Solution Approach 2:
The patent introduces an intermediary step where the reaction mixture is prepared at ambient temperature and then transferred to a thermocycler for heating before RT enzyme activation. This intermediary heating step serves as a bridge between the assembly phase and the RT phase, allowing the mixture to be prepared in advance while ensuring that non-specific binding is minimized by activating the RT enzyme only at the appropriate temperature in the thermocycler.
3Productivity
If time delay occurs between assembly and thermocycling, then ease of operation is improved for high throughput, but mispriming increases decreasing sensitivity
Solution Approach 1:
The reaction mixture is pre-assembled at ambient temperature including all components except the reverse transcriptase enzyme. This preliminary assembly can be done in advance for high throughput workflows, and the mixture can be stored temporarily without significant mispriming because the RT enzyme is not yet active. The RT enzyme is added only after the mixture is transferred to the thermocycler and heated to the RT temperature, ensuring that even with time delays, sensitivity is maintained by preventing premature reverse transcription.
4Productivity
If RT enzyme is active at ambient temperature, then reverse transcription can proceed, but non-specific transcription occurs decreasing assay quality
Solution Approach 1:
The patent applies preliminary anti-action by preventing the reverse transcriptase enzyme from being active during the assembly phase. The RT enzyme is either omitted during assembly or kept inactive (e.g., stored on ice or added after heating), thereby preemptively preventing non-specific reverse transcription that would occur if the enzyme were active at ambient temperature. This counter-measure is applied in advance to eliminate the harmful effect of mispriming while allowing efficient RT to proceed when the enzyme is activated at the appropriate temperature.
Solution Approach 2:
The reaction mixture is pre-assembled at ambient temperature including all components except the reverse transcriptase enzyme. The primer and template RNA are allowed to anneal at this temperature, but the RT enzyme is added only after the mixture is transferred to the thermocycler and heated to the RT temperature (e.g., 50°C). This preliminary assembly at ambient temperature followed by delayed enzyme addition ensures that priming occurs only at the intended temperature, preventing non-specific binding while maintaining ease of operation.
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 effectively minimizes non-specific transcription, enhancing the sensitivity and specificity of RT-PCR by ensuring specific priming and efficient RT activity at optimal temperatures.
Implementation Method 1
an aptamer oligonucleotide configured to specifically inhibit the reverse transcriptase enzyme
Implementation Method 2
reverse transcribing said target RNA into cDNA by incubating said reaction mixture at a second temperature higher than said first temperature resulting in an at least partial unfolding of said aptamer oligonucleotide
Implementation Method 3
a reverse transcriptase enzyme... reverse transcribing said target RNA into cDNA
Implementation Method 4
a DNA polymerase enzyme... amplifying said cDNA by polymerase chain reaction
Data Source
AI summary
The present invention relates to a method for amplifying a target RNA in a sample, an oligonucleotide usable in the method according to the invention, a kit for amplifying a target RNA, and a use of an oligonucleotide for inhibiting an aptamer oligonucleotide.