Isothermal Nucleic Acid Amplification via Stem-Loop DNA Linker
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Solution Overview
Problem
Isothermal nucleic acid amplification methods often suffer from non-specific amplifications due to DNA polymerase's chain replacement activity, which complicates sequencing processes and affects the accuracy of sequencing results, especially in specialized sequencing technologies like Oxford Nanopore.
Innovation Solution
An isothermal self-amplification method using a DNA linker with a palindromic complementary sequence that forms a stem-loop structure, allowing for primer-independent amplification by DNA polymerase, resulting in a folding-complementary, single-stranded DNA product without GC bias, suitable for two-generation sequencing libraries and improved sequencing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isothermal amplification methods are used, then amplification can be achieved, but non-specific amplifications occur due to DNA polymerase chain replacement activity
Solution Approach 1:
The DNA linker is designed with a palindromic complementary sequence that forms a stem-loop structure, enabling the DNA fragment to self-trigger amplification without external primers. The 3' end of the linker folds back and hybridizes to the template, creating a self-sufficient initiation mechanism that eliminates non-specific amplification caused by free primers
Solution Approach 2:
The DNA linker acts as an intermediary element that bridges the template DNA and the amplification process. By incorporating the palindromic sequence into the linker itself rather than using separate primers, the system achieves specific amplification initiation without the harmful effects of free primers
2Measurement precision
If rolling circle amplification is used for sequencing, then sequencing accuracy is improved, but the process becomes complicated and amplification heterogeneity is reduced
Solution Approach 1:
The invention extracts the essential function of primer-mediated initiation from the complex RCA process by embedding the primer-like palindromic sequence directly into the DNA linker. This simplifies the overall process while maintaining the ability to generate homogeneous amplification products suitable for sequencing
Solution Approach 2:
The DNA linker serves multiple functions: it acts as a structural element for fragment assembly, contains the palindromic sequence for self-triggered amplification initiation, and provides the template for homogeneous product generation. This multi-functionality eliminates the need for separate primers and complex RCA protocols
3Productivity
If primers are added for amplification, then amplification can be initiated, but non-specific amplifications occur
Solution Approach 1:
The DNA fragment itself serves as the primer through its palindromic complementary sequence. The 3' end folds back and hybridizes to the template, initiating amplification without requiring external primers. This self-service mechanism maintains high efficiency while ensuring specificity
Solution Approach 2:
The palindromic sequence is pre-built into the DNA linker during library preparation. This preliminary incorporation of the amplification trigger eliminates the need for separate primer addition steps and prevents non-specific amplification from the outset
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 method enables rapid, effective amplification of target fragments under isothermal conditions, increasing sequencing frequency and accuracy, and eliminating non-specific amplifications, with the amplification product being a long, continuous complementary single-stranded DNA suitable for high-throughput sequencing.
Implementation Method 1
a linear nucleic acid fragment having a palindromic complementary sequence, which itself spontaneously forms a stem-loop structure to trigger the extension amplification by the DNA polymerase
Implementation Method 2
the reagent comprises a DNA polymerase with chain replacement activity
Data Source
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AI summary
Provided is a nucleic acid isothermal self-amplification method comprising, adding suitable palindrome complementary sequences at both ends of a target template to form a stem-loop structure spontaneously, and providing reagents and conditions as needed to perform self-amplification. The method does not require addition of additional amplification primers. The reagent comprises a DNA polymerase having a strand displacement activity. The method does not rely on exogenous amplification primers for amplification, has a constant amplification temperature without a complex temperature control equipment, and achieves rapid amplification. The amplification product is a long single-stranded DNA of a continuous complementary sequence and can be applied to special occasions. In addition, the amplification has no GC bias.