Alpha-Hemolysin Variants for Nanopore Sequencing
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Solution Overview
Problem
Current alpha-hemolysin nanopores used for DNA detection suffer from high 'time-to-thread' values and deletion errors due to inherent noise in ionic current signals, limiting their specificity and accuracy in sequencing single-stranded DNA.
Innovation Solution
Development of mutant staphylococcal alpha-hemolysin variants with specific amino acid substitutions, such as T12K, T12R, N17K, and N17R, which reduce the 'time-to-thread' of nucleotides and enhance sequencing efficiency by altering the pore's characteristics, allowing for improved nucleic acid detection and sequencing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wild-type alpha-hemolysin nanopores are used for DNA detection, then the nanopore can accommodate single-stranded DNA, but the time-to-thread value is high and deletion errors occur due to inherent noise in ionic current signals
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of the alpha-hemolysin nanopore through site-directed mutagenesis. Specific residues (such as positions 12, 17, 144) are mutated to alter the pore's electrostatic properties and physical dimensions, thereby changing the translocation dynamics of DNA and reducing the time-to-thread while maintaining sequencing accuracy
Solution Approach 2:
The patent applies local quality by making targeted mutations at specific locations within the nanopore structure rather than uniformly modifying the entire pore. The mutations are concentrated in key regions such as the pore lining and constriction zones, where local changes can significantly impact DNA translocation kinetics and ionic current signals without compromising overall pore function
2Reliability
If wild-type alpha-hemolysin nanopores are used, then the pore structure is stable, but the ionic current signal contains inherent noise that limits detection specificity
Solution Approach 1:
The patent changes the electrostatic parameters of the nanopore by introducing charged amino acid substitutions (e.g., adding positive charges to interact with the negatively charged DNA backbone). This enhances the signal-to-noise ratio by strengthening the interaction between the pore and translocating DNA, thereby improving detection specificity while preserving pore stability
Solution Approach 2:
The patent applies preliminary action by pre-modifying the nanopore structure with specific mutations before DNA translocation occurs. These预先 modifications create an optimized environment that enhances signal discrimination and reduces noise during the actual sequencing process, rather than attempting to correct issues during translocation
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 mutant alpha-hemolysin variants significantly decrease the time required to capture nucleotides, enhancing the accuracy and specificity of DNA sequencing by reducing errors and noise in ionic current signals, thereby improving nanopore-based sequencing technologies.
Implementation Method 1
Alpha-hemolysin (α-HL, a-HL or alpha-HL) is a self-assembling toxin which forms an aqueous channel in the membrane of a host cell
Implementation Method 2
analyzing the ionic current signature as DNA translocates through the pore
Implementation Method 3
Alpha-HL has become a principal component for the nanopore sequencing community. It has many advantageous properties including high stability, self assembly
Data Source
AI summary
Described herein are variants of alpha-hemolysin having at least one mutation selected from T12R, T12K, N17R, N17K or combinations of T12 and N17 mutations. The variants in some embodiments may further comprise H144A. The α-hemolysin variants have a decreased time to thread.