Reversible Pol B Polymerase Inactivation for Hot-Start PCR
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Solution Overview
Problem
Current methods for reversible inactivation of thermostable DNA polymerases, such as those used in PCR, face challenges like non-specific amplification and primer degradation due to residual activity at room temperature, which can lead to mis-priming and primer-dimer formation, and existing solutions like antibody binding are costly and prone to contamination.
Innovation Solution
The method involves reacting thermostable Pol B DNA polymerases with dicarboxylic acid anhydrides like maleic anhydride or citraconic anhydride to reversibly inactivate both polymerase and 3'-5' exonuclease activities, which can be restored at elevated temperatures or in specific pH buffers, maintaining the proper activity ratio for high fidelity amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermostable Pol B DNA polymerase is used for high fidelity amplification, then amplification fidelity is improved, but residual polymerase activity and 3'-5' exonuclease activity at room temperature cause primer degradation and mis-priming
Solution Approach 1:
The polymerase is pre-modified with a reversible inactivating agent (such as N-ethylmaleimide or iodoacetamide) before the PCR reaction begins. This preliminary modification inactivates both the polymerase and 3'-5' exonuclease activities at room temperature, preventing primer degradation and mis-priming during reaction setup. The modification is reversible, allowing enzyme activation when needed.
Solution Approach 2:
The invention changes the chemical state of the polymerase by introducing reversible covalent modifications through reaction with specific reagents. The polymerase activity can be toggled between active and inactive states by controlling the presence or absence of the modifying agent, allowing precise control over when the enzyme performs its function versus when it remains dormant to avoid harmful side effects.
2Reliability
If antibody binding is used to control polymerase activity, then non-specific amplification is reduced, but contamination risk and cost increase
Solution Approach 1:
The invention replaces expensive and contamination-prone antibodies with small chemical modifying agents (such as N-ethylmaleimide, iodoacetamide, or other alkylating agents) that can be easily added to and removed from the reaction mixture. These small molecule reagents are cheaper, less prone to contamination, and can be precisely controlled through their chemical properties.
Solution Approach 2:
The invention substitutes the biological antibody-enzyme interaction system with a chemical modification system. Instead of relying on protein-protein binding (mechanical/biological system), the control is achieved through chemical reactions between the modifying agent and specific amino acid residues on the polymerase, providing more predictable and controllable activity regulation.
3Reliability
If wax-barrier is used to prevent mis-priming, then non-specific amplification is reduced, but handling complexity and contamination risk increase
Solution Approach 1:
The invention extracts the temperature-dependent activation function from a physical barrier system (wax) and implements it through chemical modification of the enzyme itself. This eliminates the need for separate wax barriers and complex layering procedures, simplifying the overall system while achieving the same goal of preventing mis-priming through temperature-controlled activation.
4Reliability
If thermostable polymerase is added at higher temperatures to prevent mis-priming, then non-specific amplification is reduced, but reaction setup complexity increases
Solution Approach 1:
The polymerase is pre-modified with a reversible inactivating agent before the PCR reaction begins. This preliminary modification inactivates both the polymerase and 3'-5' exonuclease activities at room temperature, preventing primer degradation and mis-priming during reaction setup. The modification is reversible, allowing enzyme activation when needed.
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
This approach effectively reduces non-specific amplification and primer degradation, maintaining high amplification fidelity and efficiency by ensuring proper enzyme activity ratios, and is stable for extended storage without the need for frequent preparation.
Implementation Method 1
reacting thermostable Pol B DNA polymerases with dicarboxylic acid anhydrides like maleic anhydride or citraconic anhydride to reversibly inactivate both polymerase and 3'-5' exonuclease activities
Implementation Method 2
the thermostable Pol B DNA polymerase activity and the 3'-5' exonuclease activity are restorable by incubation at an elevated temperature
Data Source
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AI summary
A modified thermostable Pol B DNA polymerase, produced by a reaction, under essentially aqueous conditions, of a thermostable Pol B DNA polymerase and a modifier reagent of Formula (I) wherein the reaction results in a thermally reversible inactivation of the thermostable Pol B DNA polymerase activity and the 3'-5' exonuclease activity, which polymerase is suitable for hot-start PCR. Also disclosed are the method for the modification, a polynucleic acid amplification method and PCR reaction mixture and kit comprising the modified thermostable Pol B DNA polymerase.