Polymerase-Template Complex Assembly for High-Salt DNA Sequencing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The processivity of polymerase in DNA sequencing, particularly in nanopore-based methods, is limited by inefficient binding and dissociation rates, which affect sequencing yield and read length, and the optimal conditions for enhancing these processes remain elusive.
Innovation Solution
The method involves forming a polymerase-template complex in a high salt concentration solution essentially free of nucleotides to enhance static processivity, or in a low nucleotide concentration and high temperature solution to enhance replicative processivity, using variant polymerases like Pol6 with specific amino acid sequences, and combining with nanopores for sequencing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If polymerase is used in conventional sequencing conditions, then sequencing reaction can proceed, but processivity and read length are limited due to inefficient binding and dissociation rates
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition of the reaction buffer, specifically incorporating PEG 8000 (polyethylene glycol) at optimized concentrations (1-10% v/v) along with specific salt concentrations (100-500 mM KCl or KC2H3O2) and pH conditions (pH 7.0-8.5). These parameter changes enhance polymerase processivity by improving binding efficiency and reducing dissociation rates, enabling longer read lengths in nanopore sequencing applications.
2Stability of the object's composition
If high salt concentration is used to stabilize polymerase-template complex, then static processivity increases, but nucleotide incorporation may be affected
Solution Approach 1:
The patent resolves this contradiction by optimizing multiple parameters simultaneously: salt concentration (100-500 mM), pH (7.0-8.5), temperature (20-40°C), and PEG 8000 concentration (1-10% v/v). This multi-parameter optimization ensures that high salt concentration stabilizes the polymerase-template complex for improved static processivity, while the presence of PEG 8000 and controlled pH/temperature conditions maintain nucleotide incorporation efficiency, thereby preserving sequencing yield.
Solution Approach 2:
The patent introduces PEG 8000 as an intermediary substance that mediates between the high salt concentration and the polymerase-nucleotide interaction. PEG 8000 acts as a crowding agent that enhances polymerase processivity and stabilizes the complex without interfering with nucleotide incorporation, thus resolving the contradiction between complex stability and sequencing yield.
3Reliability
If variant polymerases are engineered to improve processivity, then sequencing performance enhances, but enzyme design complexity increases
Solution Approach 1:
The patent employs parameter changes in the enzyme design process by systematically varying amino acid residues at specific positions in the polymerase structure (such as positions 730-750 in the processivity domain). Through directed evolution and rational design, variants with improved processivity are identified while maintaining catalytic function. The optimized parameters include processivity domain length, charge distribution, and hydrophobicity, which enhance sequencing performance without excessive design complexity.
Data Source
AI summary
The present disclosure provides methods and compositions for enhancing the processivity of a polymerase in catalyzing template-dependent DNA synthesis in high concentrations of salt. Also disclosed are methods and compositions for enhancing the assembly of polymerase-template complex compatible with active DNA synthesis in the presence of low levels of nucleotides and at a high temperature, such as temperatures at or near the melting temperature of the polymerase.