Alpha-Hemolysin Nanopore Charge Variants for DNA Sequencing Accuracy
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Solution Overview
Problem
Wild-type alpha-hemolysin nanopores result in significant deletion errors during DNA sequencing due to high translocation rates and inherent noise in ionic current signals, necessitating improved variants with reduced time-to-thread molecules for enhanced sequencing accuracy.
Innovation Solution
Development of mutant alpha-hemolysin variants with specific amino acid substitutions, such as A1K+N47K+E287R, to decrease the time-to-thread nucleotides, and incorporation of these variants into nanopore assemblies with controlled ratios of wild-type and mutant polypeptides to optimize sequencing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wild-type alpha-hemolysin nanopores are used for DNA sequencing, then the nanopore provides stable structure and self-assembly capability, but the high translocation rate causes significant deletion errors and reduces sequencing accuracy
Solution Approach 1:
The patent applies parameter changes by modifying the physical-chemical properties of the nanopore wall through amino acid substitutions. Specifically, negative charges are introduced at positions 127-131 (replacing neutral or positive residues with negatively charged amino acids like glutamate or aspartate), and additional negative charges are added at positions 70, 111, and 287. This changes the electrostatic parameter of the pore wall, creating stronger electrostatic attraction for the negatively charged DNA backbone, thereby reducing translocation speed and improving sequencing accuracy without altering the nanopore's fundamental structure or self-assembly capability
2Reliability
If the translocation rate is reduced to improve sequencing accuracy, then deletion errors decrease, but the time required for sequencing increases
Solution Approach 1:
The patent applies local quality by introducing negative charges at specific localized regions within the nanopore rather than uniformly throughout. The primary modification is concentrated at positions 127-131 (forming a negatively charged region in the pore wall), with additional targeted charges at positions 70, 111, and 287. This localized charge distribution creates electrostatic attraction zones that selectively slow down DNA translocation at critical measurement points without completely blocking the pore or requiring excessive total translocation time, thus balancing accuracy improvement with time efficiency
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 reduce sequencing errors by decreasing the time-to-thread molecules, thereby improving the accuracy and efficiency of DNA sequencing processes.
Implementation Method 1
quantitative detection of single strand nucleic acids, such as DNA, RNA, etc., employing nanopore-based single-molecule technology
Data Source
AI summary
Described herein are variants of alpha-hemolysin having at least one mutation, such as a mutation to a positive charge. In certain examples, the mutation is selected from 0K, A1K, A1R, D2N, S3K, D4K, D4N, K8R, N47K, E70K, S106K, E111N, 127-131G, D128K, K147N, V149K, E287R, M298A, or combinations thereof in the mature, wild-type alpha-hemolysin amino acid sequence. Also provided are compositions including the variants of alpha-hemolysin, nanopore assemblies including the alpha-hemolysin variants, and methods of sequencing nucleic acids incorporating the same.