Engineered PcrA Helicase and SSB for Long Isothermal Amplification
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Solution Overview
Problem
Existing isothermal nucleic acid amplification methods are limited in producing long amplicons and often result in complex, heterogeneous products, requiring multiple primer sets and are not as versatile as traditional PCR.
Innovation Solution
The SHARP method utilizes a PcrA helicase with specific mutations and a single-stranded binding protein (SSB) to perform isothermal amplification at a constant temperature, mimicking PCR's efficiency by using the same primer set and achieving amplicons up to 6000 base pairs without thermal cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional PCR is used, then amplification versatility and amplicon length are improved, but the process requires complex thermal cycling
Solution Approach 1:
The patent extracts the thermal cycling step from the amplification process by using a helicase enzyme that can unwind DNA at constant temperature, eliminating the need for complex heating and cooling cycles while maintaining amplification versatility
Solution Approach 2:
The patent replaces the mechanical thermal cycling system with a biochemical system using helicase and SSB proteins that can perform strand separation at constant temperature through enzymatic activity rather than physical heating and cooling
2Device complexity
If isothermal amplification methods are used, then thermal cycling complexity is reduced, but amplicon length and product quality deteriorate
Solution Approach 1:
The patent introduces SSB (single-stranded binding protein) as an intermediary that stabilizes the unwound DNA strands during isothermal amplification, enabling the helicase to effectively unwind long DNA molecules and produce high-quality amplicons up to 6000 base pairs without thermal cycling
Solution Approach 2:
The patent optimizes the biochemical parameters of the isothermal system by selecting specific helicase enzymes and SSB proteins that work efficiently at constant temperature, changing the operational parameters from thermal cycling to enzymatic activity at fixed temperature to achieve both simplicity and long amplicon production
3Device complexity
If isothermal amplification methods are used, then device complexity is reduced, but product homogeneity worsens due to complex heterogeneous products
Solution Approach 1:
The patent employs a self-regulating enzymatic system where the helicase and SSB proteins automatically maintain proper DNA unwinding and strand stabilization at constant temperature, producing homogeneous amplicons without requiring external thermal control mechanisms
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
SHARP achieves efficient, specific, and sensitive amplification of nucleic acids, producing clean amplicons comparable to PCR, while eliminating the need for thermal cycling, making it suitable for various applications including molecular diagnostics and cloning.
Implementation Method 1
The PcrA helicase unwinds the double-stranded template DNA into single strands... The reaction mixture also includes adenosine triphosphate (ATP)
Implementation Method 2
Compositions include a novel helicase and an SSB (Single-Stranded Binding protein) for effective strand separation at constant temperature
Implementation Method 3
SHARP uses the same starting set of primers and template DNA as PCR does, carries out the reaction at a constant temperature, and outputs the same amplicon as PCR
Data Source
AI summary
Engineered enzymes for amplification of nucleic acid sequences which function at constant temperatures thereby eliminating heating and cooling cycles associated with traditional polymerase chain reaction (PCR) are disclosed. Specifically, novel, genetically engineered PcrA helicase enzymes are utilized in conjunction with amplification components to provide a method for amplification of nucleic acid sequence by incubating at a substantially isothermal temperature i) a composition comprising a target sequence, ii) primers and iii) said engineered PcrA helicase, a single stranded binding protein (SSB), a polymerase, and/or a thermostable pyrophosphatase (PPase) buffer, or combinations thereof.