Loop-Shaped Primer for Specific Nucleic Acid Amplification
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Solution Overview
Problem
Current PCR technologies face challenges in detecting rare mutations due to limitations in primer specificity and the inability to prevent nonspecific amplification, particularly primer dimers, which affect the reliability of mutation detection.
Innovation Solution
The development of loop-shaped primers that form a specific loop structure, allowing for direct hybridization with target nucleic acid and incorporating a universal tag sequence for enhanced specificity and sensitivity, preventing primer dimers and enabling efficient detection of rare mutations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PCR primers are used, then amplification can be performed, but nonspecific amplification and primer dimer formation occur, reducing detection reliability
Solution Approach 1:
The primer is divided into distinct functional segments: a 5' tag sequence region and a 3' loop-forming region with complementary sequences. This segmentation allows the primer to form an intramolecular loop structure that prevents intermolecular primer dimer formation while maintaining specific target binding capability.
Solution Approach 2:
The primer is pre-designed with complementary sequences at the 5' and 3' ends that form a stable loop structure before annealing to the target. This preliminary structural configuration prevents the primer from forming dimers with other primers during the PCR reaction, eliminating nonspecific amplification at the source.
2Measurement precision
If ARMS primers with 3' end specificity are used, then mutation detection can be performed, but the ability to differentiate between different mismatches is limited
Solution Approach 1:
The invention moves the specificity-determining base from the 3' end to the 5' end of the primer, and introduces a loop structure formed by complementary sequences. This dimensional repositioning allows the 3' end to be universally compatible while the 5' end provides mutation-specific discrimination, enabling differentiation of various mismatch types through the loop structure's stability characteristics.
Solution Approach 2:
Different regions of the primer are assigned different functions: the 5' tag sequence region provides universal amplification capability, while the loop-forming complementary sequences at the 3' end provide mutation-specific discrimination. This local differentiation of functional quality allows the primer to simultaneously achieve high specificity and broad adaptability for different mutation types.
3Reliability
If probes are used to prevent nonspecific amplification, then detection reliability improves, but design complexity and synthetic cost increase
Solution Approach 1:
The invention merges the functions of the primer and probe into a single loop-shaped primer molecule. The tag sequence provides universal binding for amplification, while the loop structure with complementary sequences provides specific target recognition and prevents nonspecific amplification, eliminating the need for separate probe molecules and reducing design complexity.
Solution Approach 2:
The loop-shaped primer with 5' tag sequence and 3' loop structure serves multiple functions simultaneously: it acts as a universal amplification primer through the tag sequence, provides mutation-specific discrimination through the loop structure, and prevents primer dimer formation. This multi-functionality replaces the need for separate probes and simplifies the overall detection system.
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
The loop-shaped primers provide high specificity and sensitivity for detecting rare mutations and gene expression levels, reducing nonspecific amplification and primer dimer formation, thus improving the reliability of PCR-based mutation detection.
Implementation Method 1
the 5′ end has complementary sequence to the 3′ end, so the primer can form a loop-shaped structure
Implementation Method 2
the specific base of allele gene is set in the 3′ end of the primer, this is because the Taq DNA polymerase does not have 3′-5′ exonuclease proofreading activity
Implementation Method 3
if the base is mismatched, the DNA extension reaction will fail due to the inability to form the 3′-5′-phosphodiester linkage
Implementation Method 4
the loop-shaped structure is easy to be opened, so the amplification efficiency to the target sequence will not be affected
Data Source
AI summary
Loop-shaped primer used in nucleic acid amplification is an oligonucleotide with 3-20 bases in both 3′ and 5′ ends which can be combined together to form a double-strand under appropriate conditions, resulting in the primer forming a stem-loop structure. The double-stranded structure is opened and the stem-loop structure dissolves when the primer recognizes and hybridizes with the target sequence. If the target sequence is not present the primer can form a stem-loop structure automatically by self-annealing. The primer can comprise a universal tag sequence or not. Together with universal tag sequence primer the primer comprising the universal tag sequence can be used for a second round of amplification. The primer has high specificity and does not form a primer dimmer. The primer is easy to design and is suitable for measuring gene expression and detecting features of nucleic acids such as SNPs and rare mutations.