Spatially Addressable Polymerase Control for Parallel Sequence Synthesis
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Solution Overview
Problem
Enzymatic polynucleotide synthesis using template-independent polymerases lacks precise control over the base-by-base sequence of polynucleotides, leading to unregulated nucleotide addition and the formation of variable length homopolymers, which is a challenge for applications requiring high-throughput synthesis of multiple polynucleotides with different sequences.
Innovation Solution
Spatially addressable control of polymerase activity on an array surface is achieved by regulating the activity of template-independent polymerases using blocking groups, pH changes, or enzyme inhibitors, allowing for independent control of polymerase activity at specific locations on the array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If template-independent polymerase is used for enzymatic polynucleotide synthesis, then the synthesis can be performed in an aqueous environment without toxic organic chemicals, but the polymerase adds nucleotides in an unregulated manner creating random sequences or variable length homopolymers
Solution Approach 1:
The polymerase population is segmented into two distinct functional components: a template-independent polymerase for nucleotide addition and a template-dependent polymerase for sequence control. This segmentation allows each polymerase type to perform its specialized function without interference, resolving the contradiction between unregulated addition and precise sequence control
Solution Approach 2:
A template DNA strand acts as an intermediary that translates the desired sequence information into controlled nucleotide incorporation. The template-dependent polymerase uses this intermediary to ensure that only the correct nucleotide is added at each position, providing base-by-base sequence precision while maintaining aqueous synthesis conditions
2Productivity
If only a single species of nucleotide is present in the reaction, then the polymerase can add nucleotides continuously, but this creates variable length homopolymers instead of controlled sequences
Solution Approach 1:
The system dynamically switches between different nucleotide species based on the template sequence requirements. The template-dependent polymerase dynamically selects which nucleotide to incorporate at each position, allowing continuous productive synthesis while maintaining precise sequence control through template-directed recognition
Solution Approach 2:
The template DNA provides continuous feedback to the template-dependent polymerase about which nucleotide should be added next. This feedback mechanism ensures that nucleotide addition continues at high productivity while maintaining sequence specificity, as the polymerase adjusts its substrate selection based on template complementarity
3Productivity
If polymerase activity is activated at multiple locations on the array simultaneously, then parallel synthesis can be performed, but it is impossible to synthesize polynucleotides with different sequences on the same array
Solution Approach 1:
Different regions of the array are assigned different template DNA sequences, creating local quality variations. Each location's template directs the template-dependent polymerase to incorporate specific nucleotides in a sequence-specific manner, enabling parallel synthesis of multiple different polynucleotide sequences simultaneously across the array
4Manufacturing precision
If the nucleoside phosphoramidite method is used, then each synthesis cycle reliably adds a single specific nucleotide, but the method uses toxic organic chemicals and requires complex chemical reactions
Solution Approach 1:
The complex chemical reaction system of the phosphoramidite method is replaced with a biological enzyme system. Template-dependent polymerases naturally perform sequence-specific nucleotide incorporation through biochemical recognition mechanisms, achieving the same precision without toxic organic chemicals or complex chemical activation steps
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
Enables the parallel synthesis of polynucleotides with different sequences on the same array, improving scalability and throughput by confining polymerase activity to selected locations, thereby overcoming the limitations of unregulated synthesis.
Implementation Method 1
The blocking group sterically hinders access to the active site on the polymerase preventing activity
Implementation Method 2
His-tags are complexed to a ligand on the blocking group with divalent metal cations such as Cu2+
Implementation Method 3
Changing the oxidation state of the metal cation from 2+ breaks the His-tag complex and releases the blocking group from the template-independent polymerase
Implementation Method 4
The oxidation state of the metal cation may be changed by redox reactions initiated through electrodes
Implementation Method 5
The pH of the solution at a selected location on the surface of the array is changed from the unsuitable pH to an optimum pH for the polymerase
Implementation Method 6
The pH of the solution may be changed by activation of electrodes, addition of an acid or base, or photoactivation of a photoacid or a photobase
Implementation Method 7
The change in pH is confined to the selected location by a buffer in a reaction reagent solution
Data Source
AI summary
Multiple polynucleotides having different, arbitrary sequences are synthesized on the surface of an array by spatial control of polymerase activity. The polymerase is a template-independent polymerase such as terminal deoxynucleotidyl transferase (TdT). Spatial control of polymerase activity is implemented by localized changes in redox-pH conditions. A single species of nucleotide is added and incorporated on growing polynucleotide strands at locations on the array where the polymerase is active. A washing step removes the polymerase and free nucleotides. This process may be repeated multiple times changing both the location of polymerase activity and the species of nucleotide thereby synthesizing different polynucleotides in parallel on the surface of the array. Polymerase activity may be regulated by removing a blocking group attached to a His-tag sequence on the polymerase, a change in pH, or release of encapsulated inhibitors.